/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp

Bug Summary

File:	llvm/lib/Transforms/Utils/SimplifyCFG.cpp
Warning:	line 3106, column 11 3rd function call argument is an uninitialized value
Annotated Source Code

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clang -cc1 -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name SimplifyCFG.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -analyzer-config-compatibility-mode=true -mrelocation-model pic -pic-level 2 -fhalf-no-semantic-interposition -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -tune-cpu generic -fno-split-dwarf-inlining -debugger-tuning=gdb -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-12/lib/clang/12.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/build-llvm/lib/Transforms/Utils -I /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils -I /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/build-llvm/include -I /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-12/lib/clang/12.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++14 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/build-llvm/lib/Transforms/Utils -fdebug-prefix-map=/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a=. -ferror-limit 19 -fvisibility-inlines-hidden -stack-protector 2 -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -faddrsig -o /tmp/scan-build-2021-01-22-054259-40355-1 -x c++ /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp

→
1//===- SimplifyCFG.cpp - Code to perform CFG simplification ---------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// Peephole optimize the CFG.
10//
11//===----------------------------------------------------------------------===//

13#include "llvm/ADT/APInt.h"
14#include "llvm/ADT/ArrayRef.h"
15#include "llvm/ADT/DenseMap.h"
16#include "llvm/ADT/MapVector.h"
17#include "llvm/ADT/Optional.h"
18#include "llvm/ADT/STLExtras.h"
19#include "llvm/ADT/ScopeExit.h"
20#include "llvm/ADT/Sequence.h"
21#include "llvm/ADT/SetOperations.h"
22#include "llvm/ADT/SetVector.h"
23#include "llvm/ADT/SmallPtrSet.h"
24#include "llvm/ADT/SmallVector.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/ADT/StringRef.h"
27#include "llvm/Analysis/AssumptionCache.h"
28#include "llvm/Analysis/ConstantFolding.h"
29#include "llvm/Analysis/EHPersonalities.h"
30#include "llvm/Analysis/GuardUtils.h"
31#include "llvm/Analysis/InstructionSimplify.h"
32#include "llvm/Analysis/MemorySSA.h"
33#include "llvm/Analysis/MemorySSAUpdater.h"
34#include "llvm/Analysis/TargetTransformInfo.h"
35#include "llvm/Analysis/ValueTracking.h"
36#include "llvm/IR/Attributes.h"
37#include "llvm/IR/BasicBlock.h"
38#include "llvm/IR/CFG.h"
39#include "llvm/IR/Constant.h"
40#include "llvm/IR/ConstantRange.h"
41#include "llvm/IR/Constants.h"
42#include "llvm/IR/DataLayout.h"
43#include "llvm/IR/DerivedTypes.h"
44#include "llvm/IR/Function.h"
45#include "llvm/IR/GlobalValue.h"
46#include "llvm/IR/GlobalVariable.h"
47#include "llvm/IR/IRBuilder.h"
48#include "llvm/IR/InstrTypes.h"
49#include "llvm/IR/Instruction.h"
50#include "llvm/IR/Instructions.h"
51#include "llvm/IR/IntrinsicInst.h"
52#include "llvm/IR/Intrinsics.h"
53#include "llvm/IR/LLVMContext.h"
54#include "llvm/IR/MDBuilder.h"
55#include "llvm/IR/Metadata.h"
56#include "llvm/IR/Module.h"
57#include "llvm/IR/NoFolder.h"
58#include "llvm/IR/Operator.h"
59#include "llvm/IR/PatternMatch.h"
60#include "llvm/IR/Type.h"
61#include "llvm/IR/Use.h"
62#include "llvm/IR/User.h"
63#include "llvm/IR/Value.h"
64#include "llvm/Support/Casting.h"
65#include "llvm/Support/CommandLine.h"
66#include "llvm/Support/Debug.h"
67#include "llvm/Support/ErrorHandling.h"
68#include "llvm/Support/KnownBits.h"
69#include "llvm/Support/MathExtras.h"
70#include "llvm/Support/raw_ostream.h"
71#include "llvm/Transforms/Utils/BasicBlockUtils.h"
72#include "llvm/Transforms/Utils/Local.h"
73#include "llvm/Transforms/Utils/SSAUpdater.h"
74#include "llvm/Transforms/Utils/ValueMapper.h"
75#include <algorithm>
76#include <cassert>
77#include <climits>
78#include <cstddef>
79#include <cstdint>
80#include <iterator>
81#include <map>
82#include <set>
83#include <tuple>
84#include <utility>
85#include <vector>

87using namespace llvm;
88using namespace PatternMatch;

90#define DEBUG_TYPE"simplifycfg" "simplifycfg"

92cl::opt<bool> llvm::RequireAndPreserveDomTree(
  "simplifycfg-require-and-preserve-domtree", cl::Hidden, cl::ZeroOrMore,
  cl::init(false),
  cl::desc("Temorary development switch used to gradually uplift SimplifyCFG "
           "into preserving DomTree,"));

98// Chosen as 2 so as to be cheap, but still to have enough power to fold
99// a select, so the "clamp" idiom (of a min followed by a max) will be caught.
100// To catch this, we need to fold a compare and a select, hence '2' being the
101// minimum reasonable default.
102static cl::opt<unsigned> PHINodeFoldingThreshold(
  "phi-node-folding-threshold", cl::Hidden, cl::init(2),
  cl::desc(
      "Control the amount of phi node folding to perform (default = 2)"));

107static cl::opt<unsigned> TwoEntryPHINodeFoldingThreshold(
  "two-entry-phi-node-folding-threshold", cl::Hidden, cl::init(4),
  cl::desc("Control the maximal total instruction cost that we are willing "
           "to speculatively execute to fold a 2-entry PHI node into a "
           "select (default = 4)"));

113static cl::opt<bool> DupRet(
  "simplifycfg-dup-ret", cl::Hidden, cl::init(false),
  cl::desc("Duplicate return instructions into unconditional branches"));

117static cl::opt<bool>
  HoistCommon("simplifycfg-hoist-common", cl::Hidden, cl::init(true),
              cl::desc("Hoist common instructions up to the parent block"));

121static cl::opt<bool>
  SinkCommon("simplifycfg-sink-common", cl::Hidden, cl::init(true),
             cl::desc("Sink common instructions down to the end block"));

125static cl::opt<bool> HoistCondStores(
  "simplifycfg-hoist-cond-stores", cl::Hidden, cl::init(true),
  cl::desc("Hoist conditional stores if an unconditional store precedes"));

129static cl::opt<bool> MergeCondStores(
  "simplifycfg-merge-cond-stores", cl::Hidden, cl::init(true),
  cl::desc("Hoist conditional stores even if an unconditional store does not "
           "precede - hoist multiple conditional stores into a single "
           "predicated store"));

135static cl::opt<bool> MergeCondStoresAggressively(
  "simplifycfg-merge-cond-stores-aggressively", cl::Hidden, cl::init(false),
  cl::desc("When merging conditional stores, do so even if the resultant "
           "basic blocks are unlikely to be if-converted as a result"));

140static cl::opt<bool> SpeculateOneExpensiveInst(
  "speculate-one-expensive-inst", cl::Hidden, cl::init(true),
  cl::desc("Allow exactly one expensive instruction to be speculatively "
           "executed"));

145static cl::opt<unsigned> MaxSpeculationDepth(
  "max-speculation-depth", cl::Hidden, cl::init(10),
  cl::desc("Limit maximum recursion depth when calculating costs of "
           "speculatively executed instructions"));

150static cl::opt<int>
151MaxSmallBlockSize("simplifycfg-max-small-block-size", cl::Hidden, cl::init(10),
                cl::desc("Max size of a block which is still considered "
                         "small enough to thread through"));

155// Two is chosen to allow one negation and a logical combine.
156static cl::opt<unsigned>
  BranchFoldThreshold("simplifycfg-branch-fold-threshold", cl::Hidden,
                      cl::init(2),
                      cl::desc("Maximum cost of combining conditions when "
                               "folding branches"));

162STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps")static llvm::Statistic NumBitMaps = {"simplifycfg", "NumBitMaps"
, "Number of switch instructions turned into bitmaps"};
163STATISTIC(NumLinearMaps,static llvm::Statistic NumLinearMaps = {"simplifycfg", "NumLinearMaps"
, "Number of switch instructions turned into linear mapping"}
        "Number of switch instructions turned into linear mapping")static llvm::Statistic NumLinearMaps = {"simplifycfg", "NumLinearMaps"
, "Number of switch instructions turned into linear mapping"};
165STATISTIC(NumLookupTables,static llvm::Statistic NumLookupTables = {"simplifycfg", "NumLookupTables"
, "Number of switch instructions turned into lookup tables"}
        "Number of switch instructions turned into lookup tables")static llvm::Statistic NumLookupTables = {"simplifycfg", "NumLookupTables"
, "Number of switch instructions turned into lookup tables"};
167STATISTIC(static llvm::Statistic NumLookupTablesHoles = {"simplifycfg",
 "NumLookupTablesHoles", "Number of switch instructions turned into lookup tables (holes checked)"
}
  NumLookupTablesHoles,static llvm::Statistic NumLookupTablesHoles = {"simplifycfg",
 "NumLookupTablesHoles", "Number of switch instructions turned into lookup tables (holes checked)"
}
  "Number of switch instructions turned into lookup tables (holes checked)")static llvm::Statistic NumLookupTablesHoles = {"simplifycfg",
 "NumLookupTablesHoles", "Number of switch instructions turned into lookup tables (holes checked)"
};
170STATISTIC(NumTableCmpReuses, "Number of reused switch table lookup compares")static llvm::Statistic NumTableCmpReuses = {"simplifycfg", "NumTableCmpReuses"
, "Number of reused switch table lookup compares"};
171STATISTIC(NumFoldValueComparisonIntoPredecessors,static llvm::Statistic NumFoldValueComparisonIntoPredecessors
 = {"simplifycfg", "NumFoldValueComparisonIntoPredecessors", "Number of value comparisons folded into predecessor basic blocks"
}
        "Number of value comparisons folded into predecessor basic blocks")static llvm::Statistic NumFoldValueComparisonIntoPredecessors
 = {"simplifycfg", "NumFoldValueComparisonIntoPredecessors", "Number of value comparisons folded into predecessor basic blocks"
};
173STATISTIC(NumFoldBranchToCommonDest,static llvm::Statistic NumFoldBranchToCommonDest = {"simplifycfg"
, "NumFoldBranchToCommonDest", "Number of branches folded into predecessor basic block"
}
        "Number of branches folded into predecessor basic block")static llvm::Statistic NumFoldBranchToCommonDest = {"simplifycfg"
, "NumFoldBranchToCommonDest", "Number of branches folded into predecessor basic block"
};
175STATISTIC(static llvm::Statistic NumHoistCommonCode = {"simplifycfg", "NumHoistCommonCode"
, "Number of common instruction 'blocks' hoisted up to the begin block"
}
  NumHoistCommonCode,static llvm::Statistic NumHoistCommonCode = {"simplifycfg", "NumHoistCommonCode"
, "Number of common instruction 'blocks' hoisted up to the begin block"
}
  "Number of common instruction 'blocks' hoisted up to the begin block")static llvm::Statistic NumHoistCommonCode = {"simplifycfg", "NumHoistCommonCode"
, "Number of common instruction 'blocks' hoisted up to the begin block"
};
178STATISTIC(NumHoistCommonInstrs,static llvm::Statistic NumHoistCommonInstrs = {"simplifycfg",
 "NumHoistCommonInstrs", "Number of common instructions hoisted up to the begin block"
}
        "Number of common instructions hoisted up to the begin block")static llvm::Statistic NumHoistCommonInstrs = {"simplifycfg",
 "NumHoistCommonInstrs", "Number of common instructions hoisted up to the begin block"
};
180STATISTIC(NumSinkCommonCode,static llvm::Statistic NumSinkCommonCode = {"simplifycfg", "NumSinkCommonCode"
, "Number of common instruction 'blocks' sunk down to the end block"
}
        "Number of common instruction 'blocks' sunk down to the end block")static llvm::Statistic NumSinkCommonCode = {"simplifycfg", "NumSinkCommonCode"
, "Number of common instruction 'blocks' sunk down to the end block"
};
182STATISTIC(NumSinkCommonInstrs,static llvm::Statistic NumSinkCommonInstrs = {"simplifycfg", "NumSinkCommonInstrs"
, "Number of common instructions sunk down to the end block"}
        "Number of common instructions sunk down to the end block")static llvm::Statistic NumSinkCommonInstrs = {"simplifycfg", "NumSinkCommonInstrs"
, "Number of common instructions sunk down to the end block"};
184STATISTIC(NumSpeculations, "Number of speculative executed instructions")static llvm::Statistic NumSpeculations = {"simplifycfg", "NumSpeculations"
, "Number of speculative executed instructions"};
185STATISTIC(NumInvokes,static llvm::Statistic NumInvokes = {"simplifycfg", "NumInvokes"
, "Number of invokes with empty resume blocks simplified into calls"
}
        "Number of invokes with empty resume blocks simplified into calls")static llvm::Statistic NumInvokes = {"simplifycfg", "NumInvokes"
, "Number of invokes with empty resume blocks simplified into calls"
};

188namespace {

190// The first field contains the value that the switch produces when a certain
191// case group is selected, and the second field is a vector containing the
192// cases composing the case group.
193using SwitchCaseResultVectorTy =
  SmallVector<std::pair<Constant *, SmallVector<ConstantInt *, 4>>, 2>;

196// The first field contains the phi node that generates a result of the switch
197// and the second field contains the value generated for a certain case in the
198// switch for that PHI.
199using SwitchCaseResultsTy = SmallVector<std::pair<PHINode *, Constant *>, 4>;

201/// ValueEqualityComparisonCase - Represents a case of a switch.
202struct ValueEqualityComparisonCase {
ConstantInt *Value;
BasicBlock *Dest;

ValueEqualityComparisonCase(ConstantInt *Value, BasicBlock *Dest)
    : Value(Value), Dest(Dest) {}

bool operator<(ValueEqualityComparisonCase RHS) const {
  // Comparing pointers is ok as we only rely on the order for uniquing.
  return Value < RHS.Value;
}

bool operator==(BasicBlock *RHSDest) const { return Dest == RHSDest; }
215};

217class SimplifyCFGOpt {
const TargetTransformInfo &TTI;
DomTreeUpdater *DTU;
const DataLayout &DL;
SmallPtrSetImpl<BasicBlock *> *LoopHeaders;
const SimplifyCFGOptions &Options;
bool Resimplify;

Value *isValueEqualityComparison(Instruction *TI);
BasicBlock *GetValueEqualityComparisonCases(
    Instruction *TI, std::vector<ValueEqualityComparisonCase> &Cases);
bool SimplifyEqualityComparisonWithOnlyPredecessor(Instruction *TI,
                                                   BasicBlock *Pred,
                                                   IRBuilder<> &Builder);
bool FoldValueComparisonIntoPredecessors(Instruction *TI,
                                         IRBuilder<> &Builder);

bool simplifyReturn(ReturnInst *RI, IRBuilder<> &Builder);
bool simplifyResume(ResumeInst *RI, IRBuilder<> &Builder);
bool simplifySingleResume(ResumeInst *RI);
bool simplifyCommonResume(ResumeInst *RI);
bool simplifyCleanupReturn(CleanupReturnInst *RI);
bool simplifyUnreachable(UnreachableInst *UI);
bool simplifySwitch(SwitchInst *SI, IRBuilder<> &Builder);
bool simplifyIndirectBr(IndirectBrInst *IBI);
bool simplifyBranch(BranchInst *Branch, IRBuilder<> &Builder);
bool simplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder);
bool simplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder);
bool SimplifyCondBranchToTwoReturns(BranchInst *BI, IRBuilder<> &Builder);

bool tryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
                                           IRBuilder<> &Builder);

bool HoistThenElseCodeToIf(BranchInst *BI, const TargetTransformInfo &TTI);
bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
                            const TargetTransformInfo &TTI);
bool SimplifyTerminatorOnSelect(Instruction *OldTerm, Value *Cond,
                                BasicBlock *TrueBB, BasicBlock *FalseBB,
                                uint32_t TrueWeight, uint32_t FalseWeight);
bool SimplifyBranchOnICmpChain(BranchInst *BI, IRBuilder<> &Builder,
                               const DataLayout &DL);
bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select);
bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI);
bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder);

262public:
SimplifyCFGOpt(const TargetTransformInfo &TTI, DomTreeUpdater *DTU,
               const DataLayout &DL,
               SmallPtrSetImpl<BasicBlock *> *LoopHeaders,
               const SimplifyCFGOptions &Opts)
    : TTI(TTI), DTU(DTU), DL(DL), LoopHeaders(LoopHeaders), Options(Opts) {
  assert((!DTU || !DTU->hasPostDomTree()) &&(((!DTU || !DTU->hasPostDomTree()) && "SimplifyCFG is not yet capable of maintaining validity of a "
 "PostDomTree, so don't ask for it.") ? static_cast<void>
 (0) : __assert_fail ("(!DTU || !DTU->hasPostDomTree()) && \"SimplifyCFG is not yet capable of maintaining validity of a \" \"PostDomTree, so don't ask for it.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 270, __PRETTY_FUNCTION__))
         "SimplifyCFG is not yet capable of maintaining validity of a "(((!DTU || !DTU->hasPostDomTree()) && "SimplifyCFG is not yet capable of maintaining validity of a "
 "PostDomTree, so don't ask for it.") ? static_cast<void>
 (0) : __assert_fail ("(!DTU || !DTU->hasPostDomTree()) && \"SimplifyCFG is not yet capable of maintaining validity of a \" \"PostDomTree, so don't ask for it.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 270, __PRETTY_FUNCTION__))
         "PostDomTree, so don't ask for it.")(((!DTU || !DTU->hasPostDomTree()) && "SimplifyCFG is not yet capable of maintaining validity of a "
 "PostDomTree, so don't ask for it.") ? static_cast<void>
 (0) : __assert_fail ("(!DTU || !DTU->hasPostDomTree()) && \"SimplifyCFG is not yet capable of maintaining validity of a \" \"PostDomTree, so don't ask for it.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 270, __PRETTY_FUNCTION__));
}

bool simplifyOnce(BasicBlock *BB);
bool simplifyOnceImpl(BasicBlock *BB);
bool run(BasicBlock *BB);

// Helper to set Resimplify and return change indication.
bool requestResimplify() {
  Resimplify = true;
  return true;
}
282};

284} // end anonymous namespace

286/// Return true if it is safe to merge these two
287/// terminator instructions together.
288static bool
289SafeToMergeTerminators(Instruction *SI1, Instruction *SI2,
                     SmallSetVector<BasicBlock *, 4> *FailBlocks = nullptr) {
if (SI1 == SI2)
50
←
Assuming 'SI1' is not equal to 'SI2'→
51
←
Taking false branch→
  return false; // Can't merge with self!

// It is not safe to merge these two switch instructions if they have a common
// successor, and if that successor has a PHI node, and if *that* PHI node has
// conflicting incoming values from the two switch blocks.
BasicBlock *SI1BB = SI1->getParent();
BasicBlock *SI2BB = SI2->getParent();

SmallPtrSet<BasicBlock *, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
bool Fail = false;
for (BasicBlock *Succ : successors(SI2BB))
  if (SI1Succs.count(Succ))
    for (BasicBlock::iterator BBI = Succ->begin(); isa<PHINode>(BBI); ++BBI) {
      PHINode *PN = cast<PHINode>(BBI);
      if (PN->getIncomingValueForBlock(SI1BB) !=
          PN->getIncomingValueForBlock(SI2BB)) {
        if (FailBlocks)
          FailBlocks->insert(Succ);
        Fail = true;
      }
    }

return !Fail;
52
←
Returning the value 1, which participates in a condition later→
315}

317/// Return true if it is safe and profitable to merge these two terminator
318/// instructions together, where SI1 is an unconditional branch. PhiNodes will
319/// store all PHI nodes in common successors.
320static bool
321isProfitableToFoldUnconditional(BranchInst *SI1, BranchInst *SI2,
                              Instruction *Cond,
                              SmallVectorImpl<PHINode *> &PhiNodes) {
if (SI1 == SI2)
  return false; // Can't merge with self!
assert(SI1->isUnconditional() && SI2->isConditional())((SI1->isUnconditional() && SI2->isConditional(
)) ? static_cast<void> (0) : __assert_fail ("SI1->isUnconditional() && SI2->isConditional()"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 326, __PRETTY_FUNCTION__));

// We fold the unconditional branch if we can easily update all PHI nodes in
// common successors:
// 1> We have a constant incoming value for the conditional branch;
// 2> We have "Cond" as the incoming value for the unconditional branch;
// 3> SI2->getCondition() and Cond have same operands.
CmpInst *Ci2 = dyn_cast<CmpInst>(SI2->getCondition());
if (!Ci2)
  return false;
if (!(Cond->getOperand(0) == Ci2->getOperand(0) &&
      Cond->getOperand(1) == Ci2->getOperand(1)) &&
    !(Cond->getOperand(0) == Ci2->getOperand(1) &&
      Cond->getOperand(1) == Ci2->getOperand(0)))
  return false;

BasicBlock *SI1BB = SI1->getParent();
BasicBlock *SI2BB = SI2->getParent();
SmallPtrSet<BasicBlock *, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB));
for (BasicBlock *Succ : successors(SI2BB))
  if (SI1Succs.count(Succ))
    for (BasicBlock::iterator BBI = Succ->begin(); isa<PHINode>(BBI); ++BBI) {
      PHINode *PN = cast<PHINode>(BBI);
      if (PN->getIncomingValueForBlock(SI1BB) != Cond ||
          !isa<ConstantInt>(PN->getIncomingValueForBlock(SI2BB)))
        return false;
      PhiNodes.push_back(PN);
    }
return true;
355}

357/// Update PHI nodes in Succ to indicate that there will now be entries in it
358/// from the 'NewPred' block. The values that will be flowing into the PHI nodes
359/// will be the same as those coming in from ExistPred, an existing predecessor
360/// of Succ.
361static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred,
                                BasicBlock *ExistPred,
                                MemorySSAUpdater *MSSAU = nullptr) {
for (PHINode &PN : Succ->phis())
  PN.addIncoming(PN.getIncomingValueForBlock(ExistPred), NewPred);
if (MSSAU)
  if (auto *MPhi = MSSAU->getMemorySSA()->getMemoryAccess(Succ))
    MPhi->addIncoming(MPhi->getIncomingValueForBlock(ExistPred), NewPred);
369}

371/// Compute an abstract "cost" of speculating the given instruction,
372/// which is assumed to be safe to speculate. TCC_Free means cheap,
373/// TCC_Basic means less cheap, and TCC_Expensive means prohibitively
374/// expensive.
375static unsigned ComputeSpeculationCost(const User *I,
                                     const TargetTransformInfo &TTI) {
assert(isSafeToSpeculativelyExecute(I) &&((isSafeToSpeculativelyExecute(I) && "Instruction is not safe to speculatively execute!"
) ? static_cast<void> (0) : __assert_fail ("isSafeToSpeculativelyExecute(I) && \"Instruction is not safe to speculatively execute!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 378, __PRETTY_FUNCTION__))
       "Instruction is not safe to speculatively execute!")((isSafeToSpeculativelyExecute(I) && "Instruction is not safe to speculatively execute!"
) ? static_cast<void> (0) : __assert_fail ("isSafeToSpeculativelyExecute(I) && \"Instruction is not safe to speculatively execute!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 378, __PRETTY_FUNCTION__));
return TTI.getUserCost(I, TargetTransformInfo::TCK_SizeAndLatency);
380}

382/// If we have a merge point of an "if condition" as accepted above,
383/// return true if the specified value dominates the block.  We
384/// don't handle the true generality of domination here, just a special case
385/// which works well enough for us.
386///
387/// If AggressiveInsts is non-null, and if V does not dominate BB, we check to
388/// see if V (which must be an instruction) and its recursive operands
389/// that do not dominate BB have a combined cost lower than CostRemaining and
390/// are non-trapping.  If both are true, the instruction is inserted into the
391/// set and true is returned.
392///
393/// The cost for most non-trapping instructions is defined as 1 except for
394/// Select whose cost is 2.
395///
396/// After this function returns, CostRemaining is decreased by the cost of
397/// V plus its non-dominating operands.  If that cost is greater than
398/// CostRemaining, false is returned and CostRemaining is undefined.
399static bool DominatesMergePoint(Value *V, BasicBlock *BB,
                              SmallPtrSetImpl<Instruction *> &AggressiveInsts,
                              int &BudgetRemaining,
                              const TargetTransformInfo &TTI,
                              unsigned Depth = 0) {
// It is possible to hit a zero-cost cycle (phi/gep instructions for example),
// so limit the recursion depth.
// TODO: While this recursion limit does prevent pathological behavior, it
// would be better to track visited instructions to avoid cycles.
if (Depth == MaxSpeculationDepth)
  return false;

Instruction *I = dyn_cast<Instruction>(V);
if (!I) {
  // Non-instructions all dominate instructions, but not all constantexprs
  // can be executed unconditionally.
  if (ConstantExpr *C = dyn_cast<ConstantExpr>(V))
    if (C->canTrap())
      return false;
  return true;
}
BasicBlock *PBB = I->getParent();

// We don't want to allow weird loops that might have the "if condition" in
// the bottom of this block.
if (PBB == BB)
  return false;

// If this instruction is defined in a block that contains an unconditional
// branch to BB, then it must be in the 'conditional' part of the "if
// statement".  If not, it definitely dominates the region.
BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator());
if (!BI || BI->isConditional() || BI->getSuccessor(0) != BB)
  return true;

// If we have seen this instruction before, don't count it again.
if (AggressiveInsts.count(I))
  return true;

// Okay, it looks like the instruction IS in the "condition".  Check to
// see if it's a cheap instruction to unconditionally compute, and if it
// only uses stuff defined outside of the condition.  If so, hoist it out.
if (!isSafeToSpeculativelyExecute(I))
  return false;

BudgetRemaining -= ComputeSpeculationCost(I, TTI);

// Allow exactly one instruction to be speculated regardless of its cost
// (as long as it is safe to do so).
// This is intended to flatten the CFG even if the instruction is a division
// or other expensive operation. The speculation of an expensive instruction
// is expected to be undone in CodeGenPrepare if the speculation has not
// enabled further IR optimizations.
if (BudgetRemaining < 0 &&
    (!SpeculateOneExpensiveInst || !AggressiveInsts.empty() || Depth > 0))
  return false;

// Okay, we can only really hoist these out if their operands do
// not take us over the cost threshold.
for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
  if (!DominatesMergePoint(*i, BB, AggressiveInsts, BudgetRemaining, TTI,
                           Depth + 1))
    return false;
// Okay, it's safe to do this!  Remember this instruction.
AggressiveInsts.insert(I);
return true;
465}

467/// Extract ConstantInt from value, looking through IntToPtr
468/// and PointerNullValue. Return NULL if value is not a constant int.
469static ConstantInt *GetConstantInt(Value *V, const DataLayout &DL) {
// Normal constant int.
ConstantInt *CI = dyn_cast<ConstantInt>(V);
if (CI || !isa<Constant>(V) || !V->getType()->isPointerTy())
  return CI;

// This is some kind of pointer constant. Turn it into a pointer-sized
// ConstantInt if possible.
IntegerType *PtrTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));

// Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*).
if (isa<ConstantPointerNull>(V))
  return ConstantInt::get(PtrTy, 0);

// IntToPtr const int.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
  if (CE->getOpcode() == Instruction::IntToPtr)
    if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(0))) {
      // The constant is very likely to have the right type already.
      if (CI->getType() == PtrTy)
        return CI;
      else
        return cast<ConstantInt>(
            ConstantExpr::getIntegerCast(CI, PtrTy, /*isSigned=*/false));
    }
return nullptr;
495}

497namespace {

499/// Given a chain of or (||) or and (&&) comparison of a value against a
500/// constant, this will try to recover the information required for a switch
501/// structure.
502/// It will depth-first traverse the chain of comparison, seeking for patterns
503/// like %a == 12 or %a < 4 and combine them to produce a set of integer
504/// representing the different cases for the switch.
505/// Note that if the chain is composed of '||' it will build the set of elements
506/// that matches the comparisons (i.e. any of this value validate the chain)
507/// while for a chain of '&&' it will build the set elements that make the test
508/// fail.
509struct ConstantComparesGatherer {
const DataLayout &DL;

/// Value found for the switch comparison
Value *CompValue = nullptr;

/// Extra clause to be checked before the switch
Value *Extra = nullptr;

/// Set of integers to match in switch
SmallVector<ConstantInt *, 8> Vals;

/// Number of comparisons matched in the and/or chain
unsigned UsedICmps = 0;

/// Construct and compute the result for the comparison instruction Cond
ConstantComparesGatherer(Instruction *Cond, const DataLayout &DL) : DL(DL) {
  gather(Cond);
}

ConstantComparesGatherer(const ConstantComparesGatherer &) = delete;
ConstantComparesGatherer &
operator=(const ConstantComparesGatherer &) = delete;

533private:
/// Try to set the current value used for the comparison, it succeeds only if
/// it wasn't set before or if the new value is the same as the old one
bool setValueOnce(Value *NewVal) {
  if (CompValue && CompValue != NewVal)
    return false;
  CompValue = NewVal;
  return (CompValue != nullptr);
}

/// Try to match Instruction "I" as a comparison against a constant and
/// populates the array Vals with the set of values that match (or do not
/// match depending on isEQ).
/// Return false on failure. On success, the Value the comparison matched
/// against is placed in CompValue.
/// If CompValue is already set, the function is expected to fail if a match
/// is found but the value compared to is different.
bool matchInstruction(Instruction *I, bool isEQ) {
  // If this is an icmp against a constant, handle this as one of the cases.
  ICmpInst *ICI;
  ConstantInt *C;
  if (!((ICI = dyn_cast<ICmpInst>(I)) &&
        (C = GetConstantInt(I->getOperand(1), DL)))) {
    return false;
  }

  Value *RHSVal;
  const APInt *RHSC;

  // Pattern match a special case
  // (x & ~2^z) == y --> x == y || x == y|2^z
  // This undoes a transformation done by instcombine to fuse 2 compares.
  if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE)) {
    // It's a little bit hard to see why the following transformations are
    // correct. Here is a CVC3 program to verify them for 64-bit values:

    /*
       ONE  : BITVECTOR(64) = BVZEROEXTEND(0bin1, 63);
       x    : BITVECTOR(64);
       y    : BITVECTOR(64);
       z    : BITVECTOR(64);
       mask : BITVECTOR(64) = BVSHL(ONE, z);
       QUERY( (y & ~mask = y) =>
              ((x & ~mask = y) <=> (x = y OR x = (y |  mask)))
       );
       QUERY( (y |  mask = y) =>
              ((x |  mask = y) <=> (x = y OR x = (y & ~mask)))
       );
    */

    // Please note that each pattern must be a dual implication (<--> or
    // iff). One directional implication can create spurious matches. If the
    // implication is only one-way, an unsatisfiable condition on the left
    // side can imply a satisfiable condition on the right side. Dual
    // implication ensures that satisfiable conditions are transformed to
    // other satisfiable conditions and unsatisfiable conditions are
    // transformed to other unsatisfiable conditions.

    // Here is a concrete example of a unsatisfiable condition on the left
    // implying a satisfiable condition on the right:
    //
    // mask = (1 << z)
    // (x & ~mask) == y  --> (x == y || x == (y | mask))
    //
    // Substituting y = 3, z = 0 yields:
    // (x & -2) == 3 --> (x == 3 || x == 2)

    // Pattern match a special case:
    /*
      QUERY( (y & ~mask = y) =>
             ((x & ~mask = y) <=> (x = y OR x = (y |  mask)))
      );
    */
    if (match(ICI->getOperand(0),
              m_And(m_Value(RHSVal), m_APInt(RHSC)))) {
      APInt Mask = ~*RHSC;
      if (Mask.isPowerOf2() && (C->getValue() & ~Mask) == C->getValue()) {
        // If we already have a value for the switch, it has to match!
        if (!setValueOnce(RHSVal))
          return false;

        Vals.push_back(C);
        Vals.push_back(
            ConstantInt::get(C->getContext(),
                             C->getValue() | Mask));
        UsedICmps++;
        return true;
      }
    }

    // Pattern match a special case:
    /*
      QUERY( (y |  mask = y) =>
             ((x |  mask = y) <=> (x = y OR x = (y & ~mask)))
      );
    */
    if (match(ICI->getOperand(0),
              m_Or(m_Value(RHSVal), m_APInt(RHSC)))) {
      APInt Mask = *RHSC;
      if (Mask.isPowerOf2() && (C->getValue() | Mask) == C->getValue()) {
        // If we already have a value for the switch, it has to match!
        if (!setValueOnce(RHSVal))
          return false;

        Vals.push_back(C);
        Vals.push_back(ConstantInt::get(C->getContext(),
                                        C->getValue() & ~Mask));
        UsedICmps++;
        return true;
      }
    }

    // If we already have a value for the switch, it has to match!
    if (!setValueOnce(ICI->getOperand(0)))
      return false;

    UsedICmps++;
    Vals.push_back(C);
    return ICI->getOperand(0);
  }

  // If we have "x ult 3", for example, then we can add 0,1,2 to the set.
  ConstantRange Span = ConstantRange::makeAllowedICmpRegion(
      ICI->getPredicate(), C->getValue());

  // Shift the range if the compare is fed by an add. This is the range
  // compare idiom as emitted by instcombine.
  Value *CandidateVal = I->getOperand(0);
  if (match(I->getOperand(0), m_Add(m_Value(RHSVal), m_APInt(RHSC)))) {
    Span = Span.subtract(*RHSC);
    CandidateVal = RHSVal;
  }

  // If this is an and/!= check, then we are looking to build the set of
  // value that *don't* pass the and chain. I.e. to turn "x ugt 2" into
  // x != 0 && x != 1.
  if (!isEQ)
    Span = Span.inverse();

  // If there are a ton of values, we don't want to make a ginormous switch.
  if (Span.isSizeLargerThan(8) || Span.isEmptySet()) {
    return false;
  }

  // If we already have a value for the switch, it has to match!
  if (!setValueOnce(CandidateVal))
    return false;

  // Add all values from the range to the set
  for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
    Vals.push_back(ConstantInt::get(I->getContext(), Tmp));

  UsedICmps++;
  return true;
}

/// Given a potentially 'or'd or 'and'd together collection of icmp
/// eq/ne/lt/gt instructions that compare a value against a constant, extract
/// the value being compared, and stick the list constants into the Vals
/// vector.
/// One "Extra" case is allowed to differ from the other.
void gather(Value *V) {
  bool isEQ = match(V, m_LogicalOr(m_Value(), m_Value()));

  // Keep a stack (SmallVector for efficiency) for depth-first traversal
  SmallVector<Value *, 8> DFT;
  SmallPtrSet<Value *, 8> Visited;

  // Initialize
  Visited.insert(V);
  DFT.push_back(V);

  while (!DFT.empty()) {
    V = DFT.pop_back_val();

    if (Instruction *I = dyn_cast<Instruction>(V)) {
      // If it is a || (or && depending on isEQ), process the operands.
      Value *Op0, *Op1;
      if (isEQ ? match(I, m_LogicalOr(m_Value(Op0), m_Value(Op1)))
               : match(I, m_LogicalAnd(m_Value(Op0), m_Value(Op1)))) {
        if (Visited.insert(Op1).second)
          DFT.push_back(Op1);
        if (Visited.insert(Op0).second)
          DFT.push_back(Op0);

        continue;
      }

      // Try to match the current instruction
      if (matchInstruction(I, isEQ))
        // Match succeed, continue the loop
        continue;
    }

    // One element of the sequence of || (or &&) could not be match as a
    // comparison against the same value as the others.
    // We allow only one "Extra" case to be checked before the switch
    if (!Extra) {
      Extra = V;
      continue;
    }
    // Failed to parse a proper sequence, abort now
    CompValue = nullptr;
    break;
  }
}
739};

741} // end anonymous namespace

743static void EraseTerminatorAndDCECond(Instruction *TI,
                                    MemorySSAUpdater *MSSAU = nullptr) {
Instruction *Cond = nullptr;
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
  Cond = dyn_cast<Instruction>(SI->getCondition());
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
  if (BI->isConditional())
    Cond = dyn_cast<Instruction>(BI->getCondition());
} else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(TI)) {
  Cond = dyn_cast<Instruction>(IBI->getAddress());
}

TI->eraseFromParent();
if (Cond)
  RecursivelyDeleteTriviallyDeadInstructions(Cond, nullptr, MSSAU);
758}

760/// Return true if the specified terminator checks
761/// to see if a value is equal to constant integer value.
762Value *SimplifyCFGOpt::isValueEqualityComparison(Instruction *TI) {
Value *CV = nullptr;
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
  // Do not permit merging of large switch instructions into their
  // predecessors unless there is only one predecessor.
  if (!SI->getParent()->hasNPredecessorsOrMore(128 / SI->getNumSuccessors()))
    CV = SI->getCondition();
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI))
  if (BI->isConditional() && BI->getCondition()->hasOneUse())
    if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
      if (ICI->isEquality() && GetConstantInt(ICI->getOperand(1), DL))
        CV = ICI->getOperand(0);
    }

// Unwrap any lossless ptrtoint cast.
if (CV) {
  if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV)) {
    Value *Ptr = PTII->getPointerOperand();
    if (PTII->getType() == DL.getIntPtrType(Ptr->getType()))
      CV = Ptr;
  }
}
return CV;
785}

787/// Given a value comparison instruction,
788/// decode all of the 'cases' that it represents and return the 'default' block.
789BasicBlock *SimplifyCFGOpt::GetValueEqualityComparisonCases(
  Instruction *TI, std::vector<ValueEqualityComparisonCase> &Cases) {
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
  Cases.reserve(SI->getNumCases());
  for (auto Case : SI->cases())
    Cases.push_back(ValueEqualityComparisonCase(Case.getCaseValue(),
                                                Case.getCaseSuccessor()));
  return SI->getDefaultDest();
}

BranchInst *BI = cast<BranchInst>(TI);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
BasicBlock *Succ = BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_NE);
Cases.push_back(ValueEqualityComparisonCase(
    GetConstantInt(ICI->getOperand(1), DL), Succ));
return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
805}

807/// Given a vector of bb/value pairs, remove any entries
808/// in the list that match the specified block.
809static void
810EliminateBlockCases(BasicBlock *BB,
                  std::vector<ValueEqualityComparisonCase> &Cases) {
llvm::erase_value(Cases, BB);
813}

815/// Return true if there are any keys in C1 that exist in C2 as well.
816static bool ValuesOverlap(std::vector<ValueEqualityComparisonCase> &C1,
                        std::vector<ValueEqualityComparisonCase> &C2) {
std::vector<ValueEqualityComparisonCase> *V1 = &C1, *V2 = &C2;

// Make V1 be smaller than V2.
if (V1->size() > V2->size())
  std::swap(V1, V2);

if (V1->empty())
  return false;
if (V1->size() == 1) {
  // Just scan V2.
  ConstantInt *TheVal = (*V1)[0].Value;
  for (unsigned i = 0, e = V2->size(); i != e; ++i)
    if (TheVal == (*V2)[i].Value)
      return true;
}

// Otherwise, just sort both lists and compare element by element.
array_pod_sort(V1->begin(), V1->end());
array_pod_sort(V2->begin(), V2->end());
unsigned i1 = 0, i2 = 0, e1 = V1->size(), e2 = V2->size();
while (i1 != e1 && i2 != e2) {
  if ((*V1)[i1].Value == (*V2)[i2].Value)
    return true;
  if ((*V1)[i1].Value < (*V2)[i2].Value)
    ++i1;
  else
    ++i2;
}
return false;
847}

849// Set branch weights on SwitchInst. This sets the metadata if there is at
850// least one non-zero weight.
851static void setBranchWeights(SwitchInst *SI, ArrayRef<uint32_t> Weights) {
// Check that there is at least one non-zero weight. Otherwise, pass
// nullptr to setMetadata which will erase the existing metadata.
MDNode *N = nullptr;
if (llvm::any_of(Weights, [](uint32_t W) { return W != 0; }))
  N = MDBuilder(SI->getParent()->getContext()).createBranchWeights(Weights);
SI->setMetadata(LLVMContext::MD_prof, N);
858}

860// Similar to the above, but for branch and select instructions that take
861// exactly 2 weights.
862static void setBranchWeights(Instruction *I, uint32_t TrueWeight,
                           uint32_t FalseWeight) {
assert(isa<BranchInst>(I) || isa<SelectInst>(I))((isa<BranchInst>(I) || isa<SelectInst>(I)) ? static_cast
<void> (0) : __assert_fail ("isa<BranchInst>(I) || isa<SelectInst>(I)"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 864, __PRETTY_FUNCTION__));
// Check that there is at least one non-zero weight. Otherwise, pass
// nullptr to setMetadata which will erase the existing metadata.
MDNode *N = nullptr;
if (TrueWeight || FalseWeight)
  N = MDBuilder(I->getParent()->getContext())
          .createBranchWeights(TrueWeight, FalseWeight);
I->setMetadata(LLVMContext::MD_prof, N);
872}

874/// If TI is known to be a terminator instruction and its block is known to
875/// only have a single predecessor block, check to see if that predecessor is
876/// also a value comparison with the same value, and if that comparison
877/// determines the outcome of this comparison. If so, simplify TI. This does a
878/// very limited form of jump threading.
879bool SimplifyCFGOpt::SimplifyEqualityComparisonWithOnlyPredecessor(
  Instruction *TI, BasicBlock *Pred, IRBuilder<> &Builder) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal)
  return false; // Not a value comparison in predecessor.

Value *ThisVal = isValueEqualityComparison(TI);
assert(ThisVal && "This isn't a value comparison!!")((ThisVal && "This isn't a value comparison!!") ? static_cast
<void> (0) : __assert_fail ("ThisVal && \"This isn't a value comparison!!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 886, __PRETTY_FUNCTION__));
if (ThisVal != PredVal)
  return false; // Different predicates.

// TODO: Preserve branch weight metadata, similarly to how
// FoldValueComparisonIntoPredecessors preserves it.

// Find out information about when control will move from Pred to TI's block.
std::vector<ValueEqualityComparisonCase> PredCases;
BasicBlock *PredDef =
    GetValueEqualityComparisonCases(Pred->getTerminator(), PredCases);
EliminateBlockCases(PredDef, PredCases); // Remove default from cases.

// Find information about how control leaves this block.
std::vector<ValueEqualityComparisonCase> ThisCases;
BasicBlock *ThisDef = GetValueEqualityComparisonCases(TI, ThisCases);
EliminateBlockCases(ThisDef, ThisCases); // Remove default from cases.

// If TI's block is the default block from Pred's comparison, potentially
// simplify TI based on this knowledge.
if (PredDef == TI->getParent()) {
  // If we are here, we know that the value is none of those cases listed in
  // PredCases.  If there are any cases in ThisCases that are in PredCases, we
  // can simplify TI.
  if (!ValuesOverlap(PredCases, ThisCases))
    return false;

  if (isa<BranchInst>(TI)) {
    // Okay, one of the successors of this condbr is dead.  Convert it to a
    // uncond br.
    assert(ThisCases.size() == 1 && "Branch can only have one case!")((ThisCases.size() == 1 && "Branch can only have one case!"
) ? static_cast<void> (0) : __assert_fail ("ThisCases.size() == 1 && \"Branch can only have one case!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 916, __PRETTY_FUNCTION__));
    // Insert the new branch.
    Instruction *NI = Builder.CreateBr(ThisDef);
    (void)NI;

    // Remove PHI node entries for the dead edge.
    ThisCases[0].Dest->removePredecessor(PredDef);

    LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false)
                      << "Through successor TI: " << *TI << "Leaving: " << *NIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false)
                      << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false);

    EraseTerminatorAndDCECond(TI);

    if (DTU)
      DTU->applyUpdates(
          {{DominatorTree::Delete, PredDef, ThisCases[0].Dest}});

    return true;
  }

  SwitchInstProfUpdateWrapper SI = *cast<SwitchInst>(TI);
  // Okay, TI has cases that are statically dead, prune them away.
  SmallPtrSet<Constant *, 16> DeadCases;
  for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
    DeadCases.insert(PredCases[i].Value);

  LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI; } } while (false)
                    << "Through successor TI: " << *TI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI; } } while (false);

  SmallMapVector<BasicBlock *, int, 8> NumPerSuccessorCases;
  for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) {
    --i;
    auto *Successor = i->getCaseSuccessor();
    ++NumPerSuccessorCases[Successor];
    if (DeadCases.count(i->getCaseValue())) {
      Successor->removePredecessor(PredDef);
      SI.removeCase(i);
      --NumPerSuccessorCases[Successor];
    }
  }

  std::vector<DominatorTree::UpdateType> Updates;
  for (const std::pair<BasicBlock *, int> &I : NumPerSuccessorCases)
    if (I.second == 0)
      Updates.push_back({DominatorTree::Delete, PredDef, I.first});
  if (DTU)
    DTU->applyUpdates(Updates);

  LLVM_DEBUG(dbgs() << "Leaving: " << *TI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Leaving: " << *TI <<
 "\n"; } } while (false);
  return true;
}

// Otherwise, TI's block must correspond to some matched value.  Find out
// which value (or set of values) this is.
ConstantInt *TIV = nullptr;
BasicBlock *TIBB = TI->getParent();
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
  if (PredCases[i].Dest == TIBB) {
    if (TIV)
      return false; // Cannot handle multiple values coming to this block.
    TIV = PredCases[i].Value;
  }
assert(TIV && "No edge from pred to succ?")((TIV && "No edge from pred to succ?") ? static_cast<
void> (0) : __assert_fail ("TIV && \"No edge from pred to succ?\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 979, __PRETTY_FUNCTION__));

// Okay, we found the one constant that our value can be if we get into TI's
// BB.  Find out which successor will unconditionally be branched to.
BasicBlock *TheRealDest = nullptr;
for (unsigned i = 0, e = ThisCases.size(); i != e; ++i)
  if (ThisCases[i].Value == TIV) {
    TheRealDest = ThisCases[i].Dest;
    break;
  }

// If not handled by any explicit cases, it is handled by the default case.
if (!TheRealDest)
  TheRealDest = ThisDef;

SmallSetVector<BasicBlock *, 2> RemovedSuccs;

// Remove PHI node entries for dead edges.
BasicBlock *CheckEdge = TheRealDest;
for (BasicBlock *Succ : successors(TIBB))
  if (Succ != CheckEdge) {
    if (Succ != TheRealDest)
      RemovedSuccs.insert(Succ);
    Succ->removePredecessor(TIBB);
  } else
    CheckEdge = nullptr;

// Insert the new branch.
Instruction *NI = Builder.CreateBr(TheRealDest);
(void)NI;

LLVM_DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false)
                  << "Through successor TI: " << *TI << "Leaving: " << *NIdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false)
                  << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Threading pred instr: " <<
 *Pred->getTerminator() << "Through successor TI: " <<
 *TI << "Leaving: " << *NI << "\n"; } } while
 (false);

EraseTerminatorAndDCECond(TI);
if (DTU) {
  SmallVector<DominatorTree::UpdateType, 2> Updates;
  Updates.reserve(RemovedSuccs.size());
  for (auto *RemovedSucc : RemovedSuccs)
    Updates.push_back({DominatorTree::Delete, TIBB, RemovedSucc});
  DTU->applyUpdates(Updates);
}
return true;
1023}

1025namespace {

1027/// This class implements a stable ordering of constant
1028/// integers that does not depend on their address.  This is important for
1029/// applications that sort ConstantInt's to ensure uniqueness.
1030struct ConstantIntOrdering {
bool operator()(const ConstantInt *LHS, const ConstantInt *RHS) const {
  return LHS->getValue().ult(RHS->getValue());
}
1034};

1036} // end anonymous namespace

1038static int ConstantIntSortPredicate(ConstantInt *const *P1,
                                  ConstantInt *const *P2) {
const ConstantInt *LHS = *P1;
const ConstantInt *RHS = *P2;
if (LHS == RHS)
  return 0;
return LHS->getValue().ult(RHS->getValue()) ? 1 : -1;
1045}

1047static inline bool HasBranchWeights(const Instruction *I) {
MDNode *ProfMD = I->getMetadata(LLVMContext::MD_prof);
if (ProfMD && ProfMD->getOperand(0))
  if (MDString *MDS = dyn_cast<MDString>(ProfMD->getOperand(0)))
    return MDS->getString().equals("branch_weights");

return false;
1054}

1056/// Get Weights of a given terminator, the default weight is at the front
1057/// of the vector. If TI is a conditional eq, we need to swap the branch-weight
1058/// metadata.
1059static void GetBranchWeights(Instruction *TI,
                           SmallVectorImpl<uint64_t> &Weights) {
MDNode *MD = TI->getMetadata(LLVMContext::MD_prof);
assert(MD)((MD) ? static_cast<void> (0) : __assert_fail ("MD", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1062, __PRETTY_FUNCTION__));
for (unsigned i = 1, e = MD->getNumOperands(); i < e; ++i) {
  ConstantInt *CI = mdconst::extract<ConstantInt>(MD->getOperand(i));
  Weights.push_back(CI->getValue().getZExtValue());
}

// If TI is a conditional eq, the default case is the false case,
// and the corresponding branch-weight data is at index 2. We swap the
// default weight to be the first entry.
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
  assert(Weights.size() == 2)((Weights.size() == 2) ? static_cast<void> (0) : __assert_fail
 ("Weights.size() == 2", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1072, __PRETTY_FUNCTION__));
  ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
  if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
    std::swap(Weights.front(), Weights.back());
}
1077}

1079/// Keep halving the weights until all can fit in uint32_t.
1080static void FitWeights(MutableArrayRef<uint64_t> Weights) {
uint64_t Max = *std::max_element(Weights.begin(), Weights.end());
if (Max > UINT_MAX(2147483647 *2U +1U)) {
  unsigned Offset = 32 - countLeadingZeros(Max);
  for (uint64_t &I : Weights)
    I >>= Offset;
}
1087}

1089/// The specified terminator is a value equality comparison instruction
1090/// (either a switch or a branch on "X == c").
1091/// See if any of the predecessors of the terminator block are value comparisons
1092/// on the same value.  If so, and if safe to do so, fold them together.
1093bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(Instruction *TI,
                                                       IRBuilder<> &Builder) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); // CondVal
assert(CV && "Not a comparison?")((CV && "Not a comparison?") ? static_cast<void>
 (0) : __assert_fail ("CV && \"Not a comparison?\"", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1097, __PRETTY_FUNCTION__));

bool Changed = false;

auto _ = make_scope_exit([&]() {
  if (Changed)
    ++NumFoldValueComparisonIntoPredecessors;
});

SmallSetVector<BasicBlock *, 16> Preds(pred_begin(BB), pred_end(BB));
while (!Preds.empty()) {
  BasicBlock *Pred = Preds.pop_back_val();

  // See if the predecessor is a comparison with the same value.
  Instruction *PTI = Pred->getTerminator();
  Value *PCV = isValueEqualityComparison(PTI); // PredCondVal

  if (PCV == CV && TI != PTI) {
    SmallSetVector<BasicBlock*, 4> FailBlocks;
    if (!SafeToMergeTerminators(TI, PTI, &FailBlocks)) {
      for (auto *Succ : FailBlocks) {
        if (!SplitBlockPredecessors(Succ, TI->getParent(), ".fold.split",
                                    DTU))
          return false;
      }
    }

    std::vector<DominatorTree::UpdateType> Updates;

    // Figure out which 'cases' to copy from SI to PSI.
    std::vector<ValueEqualityComparisonCase> BBCases;
    BasicBlock *BBDefault = GetValueEqualityComparisonCases(TI, BBCases);

    std::vector<ValueEqualityComparisonCase> PredCases;
    BasicBlock *PredDefault = GetValueEqualityComparisonCases(PTI, PredCases);

    // Based on whether the default edge from PTI goes to BB or not, fill in
    // PredCases and PredDefault with the new switch cases we would like to
    // build.
    SmallMapVector<BasicBlock *, int, 8> NewSuccessors;

    // Update the branch weight metadata along the way
    SmallVector<uint64_t, 8> Weights;
    bool PredHasWeights = HasBranchWeights(PTI);
    bool SuccHasWeights = HasBranchWeights(TI);

    if (PredHasWeights) {
      GetBranchWeights(PTI, Weights);
      // branch-weight metadata is inconsistent here.
      if (Weights.size() != 1 + PredCases.size())
        PredHasWeights = SuccHasWeights = false;
    } else if (SuccHasWeights)
      // If there are no predecessor weights but there are successor weights,
      // populate Weights with 1, which will later be scaled to the sum of
      // successor's weights
      Weights.assign(1 + PredCases.size(), 1);

    SmallVector<uint64_t, 8> SuccWeights;
    if (SuccHasWeights) {
      GetBranchWeights(TI, SuccWeights);
      // branch-weight metadata is inconsistent here.
      if (SuccWeights.size() != 1 + BBCases.size())
        PredHasWeights = SuccHasWeights = false;
    } else if (PredHasWeights)
      SuccWeights.assign(1 + BBCases.size(), 1);

    if (PredDefault == BB) {
      // If this is the default destination from PTI, only the edges in TI
      // that don't occur in PTI, or that branch to BB will be activated.
      std::set<ConstantInt *, ConstantIntOrdering> PTIHandled;
      for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
        if (PredCases[i].Dest != BB)
          PTIHandled.insert(PredCases[i].Value);
        else {
          // The default destination is BB, we don't need explicit targets.
          std::swap(PredCases[i], PredCases.back());

          if (PredHasWeights || SuccHasWeights) {
            // Increase weight for the default case.
            Weights[0] += Weights[i + 1];
            std::swap(Weights[i + 1], Weights.back());
            Weights.pop_back();
          }

          PredCases.pop_back();
          --i;
          --e;
        }

      // Reconstruct the new switch statement we will be building.
      if (PredDefault != BBDefault) {
        PredDefault->removePredecessor(Pred);
        if (PredDefault != BB)
          Updates.push_back({DominatorTree::Delete, Pred, PredDefault});
        PredDefault = BBDefault;
        ++NewSuccessors[BBDefault];
      }

      unsigned CasesFromPred = Weights.size();
      uint64_t ValidTotalSuccWeight = 0;
      for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
        if (!PTIHandled.count(BBCases[i].Value) &&
            BBCases[i].Dest != BBDefault) {
          PredCases.push_back(BBCases[i]);
          ++NewSuccessors[BBCases[i].Dest];
          if (SuccHasWeights || PredHasWeights) {
            // The default weight is at index 0, so weight for the ith case
            // should be at index i+1. Scale the cases from successor by
            // PredDefaultWeight (Weights[0]).
            Weights.push_back(Weights[0] * SuccWeights[i + 1]);
            ValidTotalSuccWeight += SuccWeights[i + 1];
          }
        }

      if (SuccHasWeights || PredHasWeights) {
        ValidTotalSuccWeight += SuccWeights[0];
        // Scale the cases from predecessor by ValidTotalSuccWeight.
        for (unsigned i = 1; i < CasesFromPred; ++i)
          Weights[i] *= ValidTotalSuccWeight;
        // Scale the default weight by SuccDefaultWeight (SuccWeights[0]).
        Weights[0] *= SuccWeights[0];
      }
    } else {
      // If this is not the default destination from PSI, only the edges
      // in SI that occur in PSI with a destination of BB will be
      // activated.
      std::set<ConstantInt *, ConstantIntOrdering> PTIHandled;
      std::map<ConstantInt *, uint64_t> WeightsForHandled;
      for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
        if (PredCases[i].Dest == BB) {
          PTIHandled.insert(PredCases[i].Value);

          if (PredHasWeights || SuccHasWeights) {
            WeightsForHandled[PredCases[i].Value] = Weights[i + 1];
            std::swap(Weights[i + 1], Weights.back());
            Weights.pop_back();
          }

          std::swap(PredCases[i], PredCases.back());
          PredCases.pop_back();
          --i;
          --e;
        }

      // Okay, now we know which constants were sent to BB from the
      // predecessor.  Figure out where they will all go now.
      for (unsigned i = 0, e = BBCases.size(); i != e; ++i)
        if (PTIHandled.count(BBCases[i].Value)) {
          // If this is one we are capable of getting...
          if (PredHasWeights || SuccHasWeights)
            Weights.push_back(WeightsForHandled[BBCases[i].Value]);
          PredCases.push_back(BBCases[i]);
          ++NewSuccessors[BBCases[i].Dest];
          PTIHandled.erase(
              BBCases[i].Value); // This constant is taken care of
        }

      // If there are any constants vectored to BB that TI doesn't handle,
      // they must go to the default destination of TI.
      for (ConstantInt *I : PTIHandled) {
        if (PredHasWeights || SuccHasWeights)
          Weights.push_back(WeightsForHandled[I]);
        PredCases.push_back(ValueEqualityComparisonCase(I, BBDefault));
        ++NewSuccessors[BBDefault];
      }
    }

    // Okay, at this point, we know which new successor Pred will get.  Make
    // sure we update the number of entries in the PHI nodes for these
    // successors.
    for (const std::pair<BasicBlock *, int /*Num*/> &NewSuccessor :
         NewSuccessors) {
      for (auto I : seq(0, NewSuccessor.second)) {
        (void)I;
        AddPredecessorToBlock(NewSuccessor.first, Pred, BB);
      }
      if (!is_contained(successors(Pred), NewSuccessor.first))
        Updates.push_back({DominatorTree::Insert, Pred, NewSuccessor.first});
    }

    Builder.SetInsertPoint(PTI);
    // Convert pointer to int before we switch.
    if (CV->getType()->isPointerTy()) {
      CV = Builder.CreatePtrToInt(CV, DL.getIntPtrType(CV->getType()),
                                  "magicptr");
    }

    // Now that the successors are updated, create the new Switch instruction.
    SwitchInst *NewSI =
        Builder.CreateSwitch(CV, PredDefault, PredCases.size());
    NewSI->setDebugLoc(PTI->getDebugLoc());
    for (ValueEqualityComparisonCase &V : PredCases)
      NewSI->addCase(V.Value, V.Dest);

    if (PredHasWeights || SuccHasWeights) {
      // Halve the weights if any of them cannot fit in an uint32_t
      FitWeights(Weights);

      SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());

      setBranchWeights(NewSI, MDWeights);
    }

    EraseTerminatorAndDCECond(PTI);

    // Okay, last check.  If BB is still a successor of PSI, then we must
    // have an infinite loop case.  If so, add an infinitely looping block
    // to handle the case to preserve the behavior of the code.
    BasicBlock *InfLoopBlock = nullptr;
    for (unsigned i = 0, e = NewSI->getNumSuccessors(); i != e; ++i)
      if (NewSI->getSuccessor(i) == BB) {
        if (!InfLoopBlock) {
          // Insert it at the end of the function, because it's either code,
          // or it won't matter if it's hot. :)
          InfLoopBlock = BasicBlock::Create(BB->getContext(), "infloop",
                                            BB->getParent());
          BranchInst::Create(InfLoopBlock, InfLoopBlock);
          Updates.push_back(
              {DominatorTree::Insert, InfLoopBlock, InfLoopBlock});
        }
        NewSI->setSuccessor(i, InfLoopBlock);
      }

    if (InfLoopBlock)
      Updates.push_back({DominatorTree::Insert, Pred, InfLoopBlock});

    Updates.push_back({DominatorTree::Delete, Pred, BB});

    if (DTU)
      DTU->applyUpdates(Updates);

    Changed = true;
  }
}
return Changed;
1332}

1334// If we would need to insert a select that uses the value of this invoke
1335// (comments in HoistThenElseCodeToIf explain why we would need to do this), we
1336// can't hoist the invoke, as there is nowhere to put the select in this case.
1337static bool isSafeToHoistInvoke(BasicBlock *BB1, BasicBlock *BB2,
                              Instruction *I1, Instruction *I2) {
for (BasicBlock *Succ : successors(BB1)) {
  for (const PHINode &PN : Succ->phis()) {
    Value *BB1V = PN.getIncomingValueForBlock(BB1);
    Value *BB2V = PN.getIncomingValueForBlock(BB2);
    if (BB1V != BB2V && (BB1V == I1 || BB2V == I2)) {
      return false;
    }
  }
}
return true;
1349}

1351static bool passingValueIsAlwaysUndefined(Value *V, Instruction *I, bool PtrValueMayBeModified = false);

1353/// Given a conditional branch that goes to BB1 and BB2, hoist any common code
1354/// in the two blocks up into the branch block. The caller of this function
1355/// guarantees that BI's block dominates BB1 and BB2.
1356bool SimplifyCFGOpt::HoistThenElseCodeToIf(BranchInst *BI,
                                         const TargetTransformInfo &TTI) {
// This does very trivial matching, with limited scanning, to find identical
// instructions in the two blocks.  In particular, we don't want to get into
// O(M*N) situations here where M and N are the sizes of BB1 and BB2.  As
// such, we currently just scan for obviously identical instructions in an
// identical order.
BasicBlock *BB1 = BI->getSuccessor(0); // The true destination.
BasicBlock *BB2 = BI->getSuccessor(1); // The false destination

BasicBlock::iterator BB1_Itr = BB1->begin();
BasicBlock::iterator BB2_Itr = BB2->begin();

Instruction *I1 = &*BB1_Itr++, *I2 = &*BB2_Itr++;
// Skip debug info if it is not identical.
DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
  while (isa<DbgInfoIntrinsic>(I1))
    I1 = &*BB1_Itr++;
  while (isa<DbgInfoIntrinsic>(I2))
    I2 = &*BB2_Itr++;
}
// FIXME: Can we define a safety predicate for CallBr?
if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) ||
    (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)) ||
    isa<CallBrInst>(I1))
  return false;

BasicBlock *BIParent = BI->getParent();

bool Changed = false;

auto _ = make_scope_exit([&]() {
  if (Changed)
    ++NumHoistCommonCode;
});

do {
  // If we are hoisting the terminator instruction, don't move one (making a
  // broken BB), instead clone it, and remove BI.
  if (I1->isTerminator())
    goto HoistTerminator;

  // If we're going to hoist a call, make sure that the two instructions we're
  // commoning/hoisting are both marked with musttail, or neither of them is
  // marked as such. Otherwise, we might end up in a situation where we hoist
  // from a block where the terminator is a `ret` to a block where the terminator
  // is a `br`, and `musttail` calls expect to be followed by a return.
  auto *C1 = dyn_cast<CallInst>(I1);
  auto *C2 = dyn_cast<CallInst>(I2);
  if (C1 && C2)
    if (C1->isMustTailCall() != C2->isMustTailCall())
      return Changed;

  if (!TTI.isProfitableToHoist(I1) || !TTI.isProfitableToHoist(I2))
    return Changed;

  // If any of the two call sites has nomerge attribute, stop hoisting.
  if (const auto *CB1 = dyn_cast<CallBase>(I1))
    if (CB1->cannotMerge())
      return Changed;
  if (const auto *CB2 = dyn_cast<CallBase>(I2))
    if (CB2->cannotMerge())
      return Changed;

  if (isa<DbgInfoIntrinsic>(I1) || isa<DbgInfoIntrinsic>(I2)) {
    assert (isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic>(I2))((isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic
>(I2)) ? static_cast<void> (0) : __assert_fail ("isa<DbgInfoIntrinsic>(I1) && isa<DbgInfoIntrinsic>(I2)"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1423, __PRETTY_FUNCTION__));
    // The debug location is an integral part of a debug info intrinsic
    // and can't be separated from it or replaced.  Instead of attempting
    // to merge locations, simply hoist both copies of the intrinsic.
    BIParent->getInstList().splice(BI->getIterator(),
                                   BB1->getInstList(), I1);
    BIParent->getInstList().splice(BI->getIterator(),
                                   BB2->getInstList(), I2);
    Changed = true;
  } else {
    // For a normal instruction, we just move one to right before the branch,
    // then replace all uses of the other with the first.  Finally, we remove
    // the now redundant second instruction.
    BIParent->getInstList().splice(BI->getIterator(),
                                   BB1->getInstList(), I1);
    if (!I2->use_empty())
      I2->replaceAllUsesWith(I1);
    I1->andIRFlags(I2);
    unsigned KnownIDs[] = {LLVMContext::MD_tbaa,
                           LLVMContext::MD_range,
                           LLVMContext::MD_fpmath,
                           LLVMContext::MD_invariant_load,
                           LLVMContext::MD_nonnull,
                           LLVMContext::MD_invariant_group,
                           LLVMContext::MD_align,
                           LLVMContext::MD_dereferenceable,
                           LLVMContext::MD_dereferenceable_or_null,
                           LLVMContext::MD_mem_parallel_loop_access,
                           LLVMContext::MD_access_group,
                           LLVMContext::MD_preserve_access_index};
    combineMetadata(I1, I2, KnownIDs, true);

    // I1 and I2 are being combined into a single instruction.  Its debug
    // location is the merged locations of the original instructions.
    I1->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());

    I2->eraseFromParent();
    Changed = true;
  }
  ++NumHoistCommonInstrs;

  I1 = &*BB1_Itr++;
  I2 = &*BB2_Itr++;
  // Skip debug info if it is not identical.
  DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
  DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
  if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
    while (isa<DbgInfoIntrinsic>(I1))
      I1 = &*BB1_Itr++;
    while (isa<DbgInfoIntrinsic>(I2))
      I2 = &*BB2_Itr++;
  }
} while (I1->isIdenticalToWhenDefined(I2));

return true;

1479HoistTerminator:
// It may not be possible to hoist an invoke.
// FIXME: Can we define a safety predicate for CallBr?
if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
  return Changed;

// TODO: callbr hoisting currently disabled pending further study.
if (isa<CallBrInst>(I1))
  return Changed;

for (BasicBlock *Succ : successors(BB1)) {
  for (PHINode &PN : Succ->phis()) {
    Value *BB1V = PN.getIncomingValueForBlock(BB1);
    Value *BB2V = PN.getIncomingValueForBlock(BB2);
    if (BB1V == BB2V)
      continue;

    // Check for passingValueIsAlwaysUndefined here because we would rather
    // eliminate undefined control flow then converting it to a select.
    if (passingValueIsAlwaysUndefined(BB1V, &PN) ||
        passingValueIsAlwaysUndefined(BB2V, &PN))
      return Changed;

    if (isa<ConstantExpr>(BB1V) && !isSafeToSpeculativelyExecute(BB1V))
      return Changed;
    if (isa<ConstantExpr>(BB2V) && !isSafeToSpeculativelyExecute(BB2V))
      return Changed;
  }
}

// Okay, it is safe to hoist the terminator.
Instruction *NT = I1->clone();
BIParent->getInstList().insert(BI->getIterator(), NT);
if (!NT->getType()->isVoidTy()) {
  I1->replaceAllUsesWith(NT);
  I2->replaceAllUsesWith(NT);
  NT->takeName(I1);
}
Changed = true;
++NumHoistCommonInstrs;

// Ensure terminator gets a debug location, even an unknown one, in case
// it involves inlinable calls.
NT->applyMergedLocation(I1->getDebugLoc(), I2->getDebugLoc());

// PHIs created below will adopt NT's merged DebugLoc.
IRBuilder<NoFolder> Builder(NT);

// Hoisting one of the terminators from our successor is a great thing.
// Unfortunately, the successors of the if/else blocks may have PHI nodes in
// them.  If they do, all PHI entries for BB1/BB2 must agree for all PHI
// nodes, so we insert select instruction to compute the final result.
std::map<std::pair<Value *, Value *>, SelectInst *> InsertedSelects;
for (BasicBlock *Succ : successors(BB1)) {
  for (PHINode &PN : Succ->phis()) {
    Value *BB1V = PN.getIncomingValueForBlock(BB1);
    Value *BB2V = PN.getIncomingValueForBlock(BB2);
    if (BB1V == BB2V)
      continue;

    // These values do not agree.  Insert a select instruction before NT
    // that determines the right value.
    SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
    if (!SI) {
      // Propagate fast-math-flags from phi node to its replacement select.
      IRBuilder<>::FastMathFlagGuard FMFGuard(Builder);
      if (isa<FPMathOperator>(PN))
        Builder.setFastMathFlags(PN.getFastMathFlags());

      SI = cast<SelectInst>(
          Builder.CreateSelect(BI->getCondition(), BB1V, BB2V,
                               BB1V->getName() + "." + BB2V->getName(), BI));
    }

    // Make the PHI node use the select for all incoming values for BB1/BB2
    for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
      if (PN.getIncomingBlock(i) == BB1 || PN.getIncomingBlock(i) == BB2)
        PN.setIncomingValue(i, SI);
  }
}

SmallVector<DominatorTree::UpdateType, 4> Updates;

// Update any PHI nodes in our new successors.
for (BasicBlock *Succ : successors(BB1)) {
  AddPredecessorToBlock(Succ, BIParent, BB1);
  Updates.push_back({DominatorTree::Insert, BIParent, Succ});
}
for (BasicBlock *Succ : successors(BI))
  Updates.push_back({DominatorTree::Delete, BIParent, Succ});

EraseTerminatorAndDCECond(BI);
if (DTU)
  DTU->applyUpdates(Updates);
return Changed;
1574}

1576// Check lifetime markers.
1577static bool isLifeTimeMarker(const Instruction *I) {
if (auto II = dyn_cast<IntrinsicInst>(I)) {
  switch (II->getIntrinsicID()) {
  default:
    break;
  case Intrinsic::lifetime_start:
  case Intrinsic::lifetime_end:
    return true;
  }
}
return false;
1588}

1590// TODO: Refine this. This should avoid cases like turning constant memcpy sizes
1591// into variables.
1592static bool replacingOperandWithVariableIsCheap(const Instruction *I,
                                              int OpIdx) {
return !isa<IntrinsicInst>(I);
1595}

1597// All instructions in Insts belong to different blocks that all unconditionally
1598// branch to a common successor. Analyze each instruction and return true if it
1599// would be possible to sink them into their successor, creating one common
1600// instruction instead. For every value that would be required to be provided by
1601// PHI node (because an operand varies in each input block), add to PHIOperands.
1602static bool canSinkInstructions(
  ArrayRef<Instruction *> Insts,
  DenseMap<Instruction *, SmallVector<Value *, 4>> &PHIOperands) {
// Prune out obviously bad instructions to move. Each instruction must have
// exactly zero or one use, and we check later that use is by a single, common
// PHI instruction in the successor.
bool HasUse = !Insts.front()->user_empty();
for (auto *I : Insts) {
  // These instructions may change or break semantics if moved.
  if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
      I->getType()->isTokenTy())
    return false;

  // Conservatively return false if I is an inline-asm instruction. Sinking
  // and merging inline-asm instructions can potentially create arguments
  // that cannot satisfy the inline-asm constraints.
  // If the instruction has nomerge attribute, return false.
  if (const auto *C = dyn_cast<CallBase>(I))
    if (C->isInlineAsm() || C->cannotMerge())
      return false;

  // Each instruction must have zero or one use.
  if (HasUse && !I->hasOneUse())
    return false;
  if (!HasUse && !I->user_empty())
    return false;
}

const Instruction *I0 = Insts.front();
for (auto *I : Insts)
  if (!I->isSameOperationAs(I0))
    return false;

// All instructions in Insts are known to be the same opcode. If they have a
// use, check that the only user is a PHI or in the same block as the
// instruction, because if a user is in the same block as an instruction we're
// contemplating sinking, it must already be determined to be sinkable.
if (HasUse) {
  auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
  auto *Succ = I0->getParent()->getTerminator()->getSuccessor(0);
  if (!all_of(Insts, [&PNUse,&Succ](const Instruction *I) -> bool {
        auto *U = cast<Instruction>(*I->user_begin());
        return (PNUse &&
                PNUse->getParent() == Succ &&
                PNUse->getIncomingValueForBlock(I->getParent()) == I) ||
               U->getParent() == I->getParent();
      }))
    return false;
}

// Because SROA can't handle speculating stores of selects, try not to sink
// loads, stores or lifetime markers of allocas when we'd have to create a
// PHI for the address operand. Also, because it is likely that loads or
// stores of allocas will disappear when Mem2Reg/SROA is run, don't sink
// them.
// This can cause code churn which can have unintended consequences down
// the line - see https://llvm.org/bugs/show_bug.cgi?id=30244.
// FIXME: This is a workaround for a deficiency in SROA - see
// https://llvm.org/bugs/show_bug.cgi?id=30188
if (isa<StoreInst>(I0) && any_of(Insts, [](const Instruction *I) {
      return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
    }))
  return false;
if (isa<LoadInst>(I0) && any_of(Insts, [](const Instruction *I) {
      return isa<AllocaInst>(I->getOperand(0)->stripPointerCasts());
    }))
  return false;
if (isLifeTimeMarker(I0) && any_of(Insts, [](const Instruction *I) {
      return isa<AllocaInst>(I->getOperand(1)->stripPointerCasts());
    }))
  return false;

for (unsigned OI = 0, OE = I0->getNumOperands(); OI != OE; ++OI) {
  Value *Op = I0->getOperand(OI);
  if (Op->getType()->isTokenTy())
    // Don't touch any operand of token type.
    return false;

  auto SameAsI0 = [&I0, OI](const Instruction *I) {
    assert(I->getNumOperands() == I0->getNumOperands())((I->getNumOperands() == I0->getNumOperands()) ? static_cast
<void> (0) : __assert_fail ("I->getNumOperands() == I0->getNumOperands()"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1681, __PRETTY_FUNCTION__));
    return I->getOperand(OI) == I0->getOperand(OI);
  };
  if (!all_of(Insts, SameAsI0)) {
    if ((isa<Constant>(Op) && !replacingOperandWithVariableIsCheap(I0, OI)) ||
        !canReplaceOperandWithVariable(I0, OI))
      // We can't create a PHI from this GEP.
      return false;
    // Don't create indirect calls! The called value is the final operand.
    if (isa<CallBase>(I0) && OI == OE - 1) {
      // FIXME: if the call was *already* indirect, we should do this.
      return false;
    }
    for (auto *I : Insts)
      PHIOperands[I].push_back(I->getOperand(OI));
  }
}
return true;
1699}

1701// Assuming canSinkLastInstruction(Blocks) has returned true, sink the last
1702// instruction of every block in Blocks to their common successor, commoning
1703// into one instruction.
1704static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
auto *BBEnd = Blocks[0]->getTerminator()->getSuccessor(0);

// canSinkLastInstruction returning true guarantees that every block has at
// least one non-terminator instruction.
SmallVector<Instruction*,4> Insts;
for (auto *BB : Blocks) {
  Instruction *I = BB->getTerminator();
  do {
    I = I->getPrevNode();
  } while (isa<DbgInfoIntrinsic>(I) && I != &BB->front());
  if (!isa<DbgInfoIntrinsic>(I))
    Insts.push_back(I);
}

// The only checking we need to do now is that all users of all instructions
// are the same PHI node. canSinkLastInstruction should have checked this but
// it is slightly over-aggressive - it gets confused by commutative instructions
// so double-check it here.
Instruction *I0 = Insts.front();
if (!I0->user_empty()) {
  auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
  if (!all_of(Insts, [&PNUse](const Instruction *I) -> bool {
        auto *U = cast<Instruction>(*I->user_begin());
        return U == PNUse;
      }))
    return false;
}

// We don't need to do any more checking here; canSinkLastInstruction should
// have done it all for us.
SmallVector<Value*, 4> NewOperands;
for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O) {
  // This check is different to that in canSinkLastInstruction. There, we
  // cared about the global view once simplifycfg (and instcombine) have
  // completed - it takes into account PHIs that become trivially
  // simplifiable.  However here we need a more local view; if an operand
  // differs we create a PHI and rely on instcombine to clean up the very
  // small mess we may make.
  bool NeedPHI = any_of(Insts, [&I0, O](const Instruction *I) {
    return I->getOperand(O) != I0->getOperand(O);
  });
  if (!NeedPHI) {
    NewOperands.push_back(I0->getOperand(O));
    continue;
  }

  // Create a new PHI in the successor block and populate it.
  auto *Op = I0->getOperand(O);
  assert(!Op->getType()->isTokenTy() && "Can't PHI tokens!")((!Op->getType()->isTokenTy() && "Can't PHI tokens!"
) ? static_cast<void> (0) : __assert_fail ("!Op->getType()->isTokenTy() && \"Can't PHI tokens!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 1753, __PRETTY_FUNCTION__));
  auto *PN = PHINode::Create(Op->getType(), Insts.size(),
                             Op->getName() + ".sink", &BBEnd->front());
  for (auto *I : Insts)
    PN->addIncoming(I->getOperand(O), I->getParent());
  NewOperands.push_back(PN);
}

// Arbitrarily use I0 as the new "common" instruction; remap its operands
// and move it to the start of the successor block.
for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O)
  I0->getOperandUse(O).set(NewOperands[O]);
I0->moveBefore(&*BBEnd->getFirstInsertionPt());

// Update metadata and IR flags, and merge debug locations.
for (auto *I : Insts)
  if (I != I0) {
    // The debug location for the "common" instruction is the merged locations
    // of all the commoned instructions.  We start with the original location
    // of the "common" instruction and iteratively merge each location in the
    // loop below.
    // This is an N-way merge, which will be inefficient if I0 is a CallInst.
    // However, as N-way merge for CallInst is rare, so we use simplified API
    // instead of using complex API for N-way merge.
    I0->applyMergedLocation(I0->getDebugLoc(), I->getDebugLoc());
    combineMetadataForCSE(I0, I, true);
    I0->andIRFlags(I);
  }

if (!I0->user_empty()) {
  // canSinkLastInstruction checked that all instructions were used by
  // one and only one PHI node. Find that now, RAUW it to our common
  // instruction and nuke it.
  auto *PN = cast<PHINode>(*I0->user_begin());
  PN->replaceAllUsesWith(I0);
  PN->eraseFromParent();
}

// Finally nuke all instructions apart from the common instruction.
for (auto *I : Insts)
  if (I != I0)
    I->eraseFromParent();

return true;
1797}

1799namespace {

// LockstepReverseIterator - Iterates through instructions
// in a set of blocks in reverse order from the first non-terminator.
// For example (assume all blocks have size n):
//   LockstepReverseIterator I([B1, B2, B3]);
//   *I-- = [B1[n], B2[n], B3[n]];
//   *I-- = [B1[n-1], B2[n-1], B3[n-1]];
//   *I-- = [B1[n-2], B2[n-2], B3[n-2]];
//   ...
class LockstepReverseIterator {
  ArrayRef<BasicBlock*> Blocks;
  SmallVector<Instruction*,4> Insts;
  bool Fail;

public:
  LockstepReverseIterator(ArrayRef<BasicBlock*> Blocks) : Blocks(Blocks) {
    reset();
  }

  void reset() {
    Fail = false;
    Insts.clear();
    for (auto *BB : Blocks) {
      Instruction *Inst = BB->getTerminator();
      for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
        Inst = Inst->getPrevNode();
      if (!Inst) {
        // Block wasn't big enough.
        Fail = true;
        return;
      }
      Insts.push_back(Inst);
    }
  }

  bool isValid() const {
    return !Fail;
  }

  void operator--() {
    if (Fail)
      return;
    for (auto *&Inst : Insts) {
      for (Inst = Inst->getPrevNode(); Inst && isa<DbgInfoIntrinsic>(Inst);)
        Inst = Inst->getPrevNode();
      // Already at beginning of block.
      if (!Inst) {
        Fail = true;
        return;
      }
    }
  }

  ArrayRef<Instruction*> operator * () const {
    return Insts;
  }
};

1858} // end anonymous namespace

1860/// Check whether BB's predecessors end with unconditional branches. If it is
1861/// true, sink any common code from the predecessors to BB.
1862/// We also allow one predecessor to end with conditional branch (but no more
1863/// than one).
1864static bool SinkCommonCodeFromPredecessors(BasicBlock *BB,
                                         DomTreeUpdater *DTU) {
// We support two situations:
//   (1) all incoming arcs are unconditional
//   (2) one incoming arc is conditional
//
// (2) is very common in switch defaults and
// else-if patterns;
//
//   if (a) f(1);
//   else if (b) f(2);
//
// produces:
//
//       [if]
//      /    \
//    [f(1)] [if]
//      |     | \
//      |     |  |
//      |  [f(2)]|
//       \    | /
//        [ end ]
//
// [end] has two unconditional predecessor arcs and one conditional. The
// conditional refers to the implicit empty 'else' arc. This conditional
// arc can also be caused by an empty default block in a switch.
//
// In this case, we attempt to sink code from all *unconditional* arcs.
// If we can sink instructions from these arcs (determined during the scan
// phase below) we insert a common successor for all unconditional arcs and
// connect that to [end], to enable sinking:
//
//       [if]
//      /    \
//    [x(1)] [if]
//      |     | \
//      |     |  \
//      |  [x(2)] |
//       \   /    |
//   [sink.split] |
//         \     /
//         [ end ]
//
SmallVector<BasicBlock*,4> UnconditionalPreds;
Instruction *Cond = nullptr;
for (auto *B : predecessors(BB)) {
  auto *T = B->getTerminator();
  if (isa<BranchInst>(T) && cast<BranchInst>(T)->isUnconditional())
    UnconditionalPreds.push_back(B);
  else if ((isa<BranchInst>(T) || isa<SwitchInst>(T)) && !Cond)
    Cond = T;
  else
    return false;
}
if (UnconditionalPreds.size() < 2)
  return false;

// We take a two-step approach to tail sinking. First we scan from the end of
// each block upwards in lockstep. If the n'th instruction from the end of each
// block can be sunk, those instructions are added to ValuesToSink and we
// carry on. If we can sink an instruction but need to PHI-merge some operands
// (because they're not identical in each instruction) we add these to
// PHIOperands.
unsigned ScanIdx = 0;
SmallPtrSet<Value*,4> InstructionsToSink;
DenseMap<Instruction*, SmallVector<Value*,4>> PHIOperands;
LockstepReverseIterator LRI(UnconditionalPreds);
while (LRI.isValid() &&
       canSinkInstructions(*LRI, PHIOperands)) {
  LLVM_DEBUG(dbgs() << "SINK: instruction can be sunk: " << *(*LRI)[0]do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: instruction can be sunk: "
 << *(*LRI)[0] << "\n"; } } while (false)
                    << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: instruction can be sunk: "
 << *(*LRI)[0] << "\n"; } } while (false);
  InstructionsToSink.insert((*LRI).begin(), (*LRI).end());
  ++ScanIdx;
  --LRI;
}

// If no instructions can be sunk, early-return.
if (ScanIdx == 0)
  return false;

bool Changed = false;

auto ProfitableToSinkInstruction = [&](LockstepReverseIterator &LRI) {
  unsigned NumPHIdValues = 0;
  for (auto *I : *LRI)
    for (auto *V : PHIOperands[I])
      if (InstructionsToSink.count(V) == 0)
        ++NumPHIdValues;
  LLVM_DEBUG(dbgs() << "SINK: #phid values: " << NumPHIdValues << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: #phid values: " <<
 NumPHIdValues << "\n"; } } while (false);
  unsigned NumPHIInsts = NumPHIdValues / UnconditionalPreds.size();
  if ((NumPHIdValues % UnconditionalPreds.size()) != 0)
      NumPHIInsts++;

  return NumPHIInsts <= 1;
};

if (Cond) {
  // Check if we would actually sink anything first! This mutates the CFG and
  // adds an extra block. The goal in doing this is to allow instructions that
  // couldn't be sunk before to be sunk - obviously, speculatable instructions
  // (such as trunc, add) can be sunk and predicated already. So we check that
  // we're going to sink at least one non-speculatable instruction.
  LRI.reset();
  unsigned Idx = 0;
  bool Profitable = false;
  while (ProfitableToSinkInstruction(LRI) && Idx < ScanIdx) {
    if (!isSafeToSpeculativelyExecute((*LRI)[0])) {
      Profitable = true;
      break;
    }
    --LRI;
    ++Idx;
  }
  if (!Profitable)
    return false;

  LLVM_DEBUG(dbgs() << "SINK: Splitting edge\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: Splitting edge\n"; }
 } while (false);
  // We have a conditional edge and we're going to sink some instructions.
  // Insert a new block postdominating all blocks we're going to sink from.
  if (!SplitBlockPredecessors(BB, UnconditionalPreds, ".sink.split", DTU))
    // Edges couldn't be split.
    return false;
  Changed = true;
}

// Now that we've analyzed all potential sinking candidates, perform the
// actual sink. We iteratively sink the last non-terminator of the source
// blocks into their common successor unless doing so would require too
// many PHI instructions to be generated (currently only one PHI is allowed
// per sunk instruction).
//
// We can use InstructionsToSink to discount values needing PHI-merging that will
// actually be sunk in a later iteration. This allows us to be more
// aggressive in what we sink. This does allow a false positive where we
// sink presuming a later value will also be sunk, but stop half way through
// and never actually sink it which means we produce more PHIs than intended.
// This is unlikely in practice though.
unsigned SinkIdx = 0;
for (; SinkIdx != ScanIdx; ++SinkIdx) {
  LLVM_DEBUG(dbgs() << "SINK: Sink: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: Sink: " << *UnconditionalPreds
[0]->getTerminator()->getPrevNode() << "\n"; } } while
 (false)
                    << *UnconditionalPreds[0]->getTerminator()->getPrevNode()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: Sink: " << *UnconditionalPreds
[0]->getTerminator()->getPrevNode() << "\n"; } } while
 (false)
                    << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: Sink: " << *UnconditionalPreds
[0]->getTerminator()->getPrevNode() << "\n"; } } while
 (false);

  // Because we've sunk every instruction in turn, the current instruction to
  // sink is always at index 0.
  LRI.reset();
  if (!ProfitableToSinkInstruction(LRI)) {
    // Too many PHIs would be created.
    LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: stopping here, too many PHIs would be created!\n"
; } } while (false)
        dbgs() << "SINK: stopping here, too many PHIs would be created!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: stopping here, too many PHIs would be created!\n"
; } } while (false);
    break;
  }

  if (!sinkLastInstruction(UnconditionalPreds)) {
    LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: stopping here, failed to actually sink instruction!\n"
; } } while (false)
        dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: stopping here, failed to actually sink instruction!\n"
; } } while (false)
        << "SINK: stopping here, failed to actually sink instruction!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SINK: stopping here, failed to actually sink instruction!\n"
; } } while (false);
    break;
  }

  NumSinkCommonInstrs++;
  Changed = true;
}
if (SinkIdx != 0)
  ++NumSinkCommonCode;
return Changed;
2030}

2032/// Determine if we can hoist sink a sole store instruction out of a
2033/// conditional block.
2034///
2035/// We are looking for code like the following:
2036///   BrBB:
2037///     store i32 %add, i32* %arrayidx2
2038///     ... // No other stores or function calls (we could be calling a memory
2039///     ... // function).
2040///     %cmp = icmp ult %x, %y
2041///     br i1 %cmp, label %EndBB, label %ThenBB
2042///   ThenBB:
2043///     store i32 %add5, i32* %arrayidx2
2044///     br label EndBB
2045///   EndBB:
2046///     ...
2047///   We are going to transform this into:
2048///   BrBB:
2049///     store i32 %add, i32* %arrayidx2
2050///     ... //
2051///     %cmp = icmp ult %x, %y
2052///     %add.add5 = select i1 %cmp, i32 %add, %add5
2053///     store i32 %add.add5, i32* %arrayidx2
2054///     ...
2055///
2056/// \return The pointer to the value of the previous store if the store can be
2057///         hoisted into the predecessor block. 0 otherwise.
2058static Value *isSafeToSpeculateStore(Instruction *I, BasicBlock *BrBB,
                                   BasicBlock *StoreBB, BasicBlock *EndBB) {
StoreInst *StoreToHoist = dyn_cast<StoreInst>(I);
if (!StoreToHoist)
  return nullptr;

// Volatile or atomic.
if (!StoreToHoist->isSimple())
  return nullptr;

Value *StorePtr = StoreToHoist->getPointerOperand();

// Look for a store to the same pointer in BrBB.
unsigned MaxNumInstToLookAt = 9;
// Skip pseudo probe intrinsic calls which are not really killing any memory
// accesses.
for (Instruction &CurI : reverse(BrBB->instructionsWithoutDebug(true))) {
  if (!MaxNumInstToLookAt)
    break;
  --MaxNumInstToLookAt;

  // Could be calling an instruction that affects memory like free().
  if (CurI.mayHaveSideEffects() && !isa<StoreInst>(CurI))
    return nullptr;

  if (auto *SI = dyn_cast<StoreInst>(&CurI)) {
    // Found the previous store make sure it stores to the same location.
    if (SI->getPointerOperand() == StorePtr)
      // Found the previous store, return its value operand.
      return SI->getValueOperand();
    return nullptr; // Unknown store.
  }
}

return nullptr;
2093}

2095/// Estimate the cost of the insertion(s) and check that the PHI nodes can be
2096/// converted to selects.
2097static bool validateAndCostRequiredSelects(BasicBlock *BB, BasicBlock *ThenBB,
                                         BasicBlock *EndBB,
                                         unsigned &SpeculatedInstructions,
                                         int &BudgetRemaining,
                                         const TargetTransformInfo &TTI) {
TargetTransformInfo::TargetCostKind CostKind =
  BB->getParent()->hasMinSize()
  ? TargetTransformInfo::TCK_CodeSize
  : TargetTransformInfo::TCK_SizeAndLatency;

bool HaveRewritablePHIs = false;
for (PHINode &PN : EndBB->phis()) {
  Value *OrigV = PN.getIncomingValueForBlock(BB);
  Value *ThenV = PN.getIncomingValueForBlock(ThenBB);

  // FIXME: Try to remove some of the duplication with HoistThenElseCodeToIf.
  // Skip PHIs which are trivial.
  if (ThenV == OrigV)
    continue;

  BudgetRemaining -=
      TTI.getCmpSelInstrCost(Instruction::Select, PN.getType(), nullptr,
                             CmpInst::BAD_ICMP_PREDICATE, CostKind);

  // Don't convert to selects if we could remove undefined behavior instead.
  if (passingValueIsAlwaysUndefined(OrigV, &PN) ||
      passingValueIsAlwaysUndefined(ThenV, &PN))
    return false;

  HaveRewritablePHIs = true;
  ConstantExpr *OrigCE = dyn_cast<ConstantExpr>(OrigV);
  ConstantExpr *ThenCE = dyn_cast<ConstantExpr>(ThenV);
  if (!OrigCE && !ThenCE)
    continue; // Known safe and cheap.

  if ((ThenCE && !isSafeToSpeculativelyExecute(ThenCE)) ||
      (OrigCE && !isSafeToSpeculativelyExecute(OrigCE)))
    return false;
  unsigned OrigCost = OrigCE ? ComputeSpeculationCost(OrigCE, TTI) : 0;
  unsigned ThenCost = ThenCE ? ComputeSpeculationCost(ThenCE, TTI) : 0;
  unsigned MaxCost =
      2 * PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic;
  if (OrigCost + ThenCost > MaxCost)
    return false;

  // Account for the cost of an unfolded ConstantExpr which could end up
  // getting expanded into Instructions.
  // FIXME: This doesn't account for how many operations are combined in the
  // constant expression.
  ++SpeculatedInstructions;
  if (SpeculatedInstructions > 1)
    return false;
}

return HaveRewritablePHIs;
2152}

2154/// Speculate a conditional basic block flattening the CFG.
2155///
2156/// Note that this is a very risky transform currently. Speculating
2157/// instructions like this is most often not desirable. Instead, there is an MI
2158/// pass which can do it with full awareness of the resource constraints.
2159/// However, some cases are "obvious" and we should do directly. An example of
2160/// this is speculating a single, reasonably cheap instruction.
2161///
2162/// There is only one distinct advantage to flattening the CFG at the IR level:
2163/// it makes very common but simplistic optimizations such as are common in
2164/// instcombine and the DAG combiner more powerful by removing CFG edges and
2165/// modeling their effects with easier to reason about SSA value graphs.
2166///
2167///
2168/// An illustration of this transform is turning this IR:
2169/// \code
2170///   BB:
2171///     %cmp = icmp ult %x, %y
2172///     br i1 %cmp, label %EndBB, label %ThenBB
2173///   ThenBB:
2174///     %sub = sub %x, %y
2175///     br label BB2
2176///   EndBB:
2177///     %phi = phi [ %sub, %ThenBB ], [ 0, %EndBB ]
2178///     ...
2179/// \endcode
2180///
2181/// Into this IR:
2182/// \code
2183///   BB:
2184///     %cmp = icmp ult %x, %y
2185///     %sub = sub %x, %y
2186///     %cond = select i1 %cmp, 0, %sub
2187///     ...
2188/// \endcode
2189///
2190/// \returns true if the conditional block is removed.
2191bool SimplifyCFGOpt::SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB,
                                          const TargetTransformInfo &TTI) {
// Be conservative for now. FP select instruction can often be expensive.
Value *BrCond = BI->getCondition();
if (isa<FCmpInst>(BrCond))
  return false;

BasicBlock *BB = BI->getParent();
BasicBlock *EndBB = ThenBB->getTerminator()->getSuccessor(0);
int BudgetRemaining =
  PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic;

// If ThenBB is actually on the false edge of the conditional branch, remember
// to swap the select operands later.
bool Invert = false;
if (ThenBB != BI->getSuccessor(0)) {
  assert(ThenBB == BI->getSuccessor(1) && "No edge from 'if' block?")((ThenBB == BI->getSuccessor(1) && "No edge from 'if' block?"
) ? static_cast<void> (0) : __assert_fail ("ThenBB == BI->getSuccessor(1) && \"No edge from 'if' block?\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 2207, __PRETTY_FUNCTION__));
  Invert = true;
}
assert(EndBB == BI->getSuccessor(!Invert) && "No edge from to end block")((EndBB == BI->getSuccessor(!Invert) && "No edge from to end block"
) ? static_cast<void> (0) : __assert_fail ("EndBB == BI->getSuccessor(!Invert) && \"No edge from to end block\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 2210, __PRETTY_FUNCTION__));

// Keep a count of how many times instructions are used within ThenBB when
// they are candidates for sinking into ThenBB. Specifically:
// - They are defined in BB, and
// - They have no side effects, and
// - All of their uses are in ThenBB.
SmallDenseMap<Instruction *, unsigned, 4> SinkCandidateUseCounts;

SmallVector<Instruction *, 4> SpeculatedDbgIntrinsics;

unsigned SpeculatedInstructions = 0;
Value *SpeculatedStoreValue = nullptr;
StoreInst *SpeculatedStore = nullptr;
for (BasicBlock::iterator BBI = ThenBB->begin(),
                          BBE = std::prev(ThenBB->end());
     BBI != BBE; ++BBI) {
  Instruction *I = &*BBI;
  // Skip debug info.
  if (isa<DbgInfoIntrinsic>(I)) {
    SpeculatedDbgIntrinsics.push_back(I);
    continue;
  }

  // Skip pseudo probes. The consequence is we lose track of the branch
  // probability for ThenBB, which is fine since the optimization here takes
  // place regardless of the branch probability.
  if (isa<PseudoProbeInst>(I)) {
    SpeculatedDbgIntrinsics.push_back(I);
    continue;
  }

  // Only speculatively execute a single instruction (not counting the
  // terminator) for now.
  ++SpeculatedInstructions;
  if (SpeculatedInstructions > 1)
    return false;

  // Don't hoist the instruction if it's unsafe or expensive.
  if (!isSafeToSpeculativelyExecute(I) &&
      !(HoistCondStores && (SpeculatedStoreValue = isSafeToSpeculateStore(
                                I, BB, ThenBB, EndBB))))
    return false;
  if (!SpeculatedStoreValue &&
      ComputeSpeculationCost(I, TTI) >
          PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic)
    return false;

  // Store the store speculation candidate.
  if (SpeculatedStoreValue)
    SpeculatedStore = cast<StoreInst>(I);

  // Do not hoist the instruction if any of its operands are defined but not
  // used in BB. The transformation will prevent the operand from
  // being sunk into the use block.
  for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i) {
    Instruction *OpI = dyn_cast<Instruction>(*i);
    if (!OpI || OpI->getParent() != BB || OpI->mayHaveSideEffects())
      continue; // Not a candidate for sinking.

    ++SinkCandidateUseCounts[OpI];
  }
}

// Consider any sink candidates which are only used in ThenBB as costs for
// speculation. Note, while we iterate over a DenseMap here, we are summing
// and so iteration order isn't significant.
for (SmallDenseMap<Instruction *, unsigned, 4>::iterator
         I = SinkCandidateUseCounts.begin(),
         E = SinkCandidateUseCounts.end();
     I != E; ++I)
  if (I->first->hasNUses(I->second)) {
    ++SpeculatedInstructions;
    if (SpeculatedInstructions > 1)
      return false;
  }

// Check that we can insert the selects and that it's not too expensive to do
// so.
bool Convert = SpeculatedStore != nullptr;
Convert |= validateAndCostRequiredSelects(BB, ThenBB, EndBB,
                                          SpeculatedInstructions,
                                          BudgetRemaining, TTI);
if (!Convert || BudgetRemaining < 0)
  return false;

// If we get here, we can hoist the instruction and if-convert.
LLVM_DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *ThenBB << "\n";)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SPECULATIVELY EXECUTING BB"
 << *ThenBB << "\n";; } } while (false);

// Insert a select of the value of the speculated store.
if (SpeculatedStoreValue) {
  IRBuilder<NoFolder> Builder(BI);
  Value *TrueV = SpeculatedStore->getValueOperand();
  Value *FalseV = SpeculatedStoreValue;
  if (Invert)
    std::swap(TrueV, FalseV);
  Value *S = Builder.CreateSelect(
      BrCond, TrueV, FalseV, "spec.store.select", BI);
  SpeculatedStore->setOperand(0, S);
  SpeculatedStore->applyMergedLocation(BI->getDebugLoc(),
                                       SpeculatedStore->getDebugLoc());
}

// Metadata can be dependent on the condition we are hoisting above.
// Conservatively strip all metadata on the instruction. Drop the debug loc
// to avoid making it appear as if the condition is a constant, which would
// be misleading while debugging.
for (auto &I : *ThenBB) {
  if (!SpeculatedStoreValue || &I != SpeculatedStore)
    I.setDebugLoc(DebugLoc());
  I.dropUnknownNonDebugMetadata();
}

// Hoist the instructions.
BB->getInstList().splice(BI->getIterator(), ThenBB->getInstList(),
                         ThenBB->begin(), std::prev(ThenBB->end()));

// Insert selects and rewrite the PHI operands.
IRBuilder<NoFolder> Builder(BI);
for (PHINode &PN : EndBB->phis()) {
  unsigned OrigI = PN.getBasicBlockIndex(BB);
  unsigned ThenI = PN.getBasicBlockIndex(ThenBB);
  Value *OrigV = PN.getIncomingValue(OrigI);
  Value *ThenV = PN.getIncomingValue(ThenI);

  // Skip PHIs which are trivial.
  if (OrigV == ThenV)
    continue;

  // Create a select whose true value is the speculatively executed value and
  // false value is the pre-existing value. Swap them if the branch
  // destinations were inverted.
  Value *TrueV = ThenV, *FalseV = OrigV;
  if (Invert)
    std::swap(TrueV, FalseV);
  Value *V = Builder.CreateSelect(BrCond, TrueV, FalseV, "spec.select", BI);
  PN.setIncomingValue(OrigI, V);
  PN.setIncomingValue(ThenI, V);
}

// Remove speculated dbg intrinsics.
// FIXME: Is it possible to do this in a more elegant way? Moving/merging the
// dbg value for the different flows and inserting it after the select.
for (Instruction *I : SpeculatedDbgIntrinsics)
  I->eraseFromParent();

++NumSpeculations;
return true;
2358}

2360/// Return true if we can thread a branch across this block.
2361static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
int Size = 0;

for (Instruction &I : BB->instructionsWithoutDebug()) {
  if (Size > MaxSmallBlockSize)
    return false; // Don't clone large BB's.

  // Can't fold blocks that contain noduplicate or convergent calls.
  if (CallInst *CI = dyn_cast<CallInst>(&I))
    if (CI->cannotDuplicate() || CI->isConvergent())
      return false;

  // We will delete Phis while threading, so Phis should not be accounted in
  // block's size
  if (!isa<PHINode>(I))
    ++Size;

  // We can only support instructions that do not define values that are
  // live outside of the current basic block.
  for (User *U : I.users()) {
    Instruction *UI = cast<Instruction>(U);
    if (UI->getParent() != BB || isa<PHINode>(UI))
      return false;
  }

  // Looks ok, continue checking.
}

return true;
2390}

2392/// If we have a conditional branch on a PHI node value that is defined in the
2393/// same block as the branch and if any PHI entries are constants, thread edges
2394/// corresponding to that entry to be branches to their ultimate destination.
2395static bool FoldCondBranchOnPHI(BranchInst *BI, DomTreeUpdater *DTU,
                              const DataLayout &DL, AssumptionCache *AC) {
BasicBlock *BB = BI->getParent();
PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
// NOTE: we currently cannot transform this case if the PHI node is used
// outside of the block.
if (!PN || PN->getParent() != BB || !PN->hasOneUse())
  return false;

// Degenerate case of a single entry PHI.
if (PN->getNumIncomingValues() == 1) {
  FoldSingleEntryPHINodes(PN->getParent());
  return true;
}

// Now we know that this block has multiple preds and two succs.
if (!BlockIsSimpleEnoughToThreadThrough(BB))
  return false;

// Okay, this is a simple enough basic block.  See if any phi values are
// constants.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
  ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i));
  if (!CB || !CB->getType()->isIntegerTy(1))
    continue;

  // Okay, we now know that all edges from PredBB should be revectored to
  // branch to RealDest.
  BasicBlock *PredBB = PN->getIncomingBlock(i);
  BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());

  if (RealDest == BB)
    continue; // Skip self loops.
  // Skip if the predecessor's terminator is an indirect branch.
  if (isa<IndirectBrInst>(PredBB->getTerminator()))
    continue;

  SmallVector<DominatorTree::UpdateType, 3> Updates;

  // The dest block might have PHI nodes, other predecessors and other
  // difficult cases.  Instead of being smart about this, just insert a new
  // block that jumps to the destination block, effectively splitting
  // the edge we are about to create.
  BasicBlock *EdgeBB =
      BasicBlock::Create(BB->getContext(), RealDest->getName() + ".critedge",
                         RealDest->getParent(), RealDest);
  BranchInst *CritEdgeBranch = BranchInst::Create(RealDest, EdgeBB);
  Updates.push_back({DominatorTree::Insert, EdgeBB, RealDest});
  CritEdgeBranch->setDebugLoc(BI->getDebugLoc());

  // Update PHI nodes.
  AddPredecessorToBlock(RealDest, EdgeBB, BB);

  // BB may have instructions that are being threaded over.  Clone these
  // instructions into EdgeBB.  We know that there will be no uses of the
  // cloned instructions outside of EdgeBB.
  BasicBlock::iterator InsertPt = EdgeBB->begin();
  DenseMap<Value *, Value *> TranslateMap; // Track translated values.
  for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
    if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
      TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
      continue;
    }
    // Clone the instruction.
    Instruction *N = BBI->clone();
    if (BBI->hasName())
      N->setName(BBI->getName() + ".c");

    // Update operands due to translation.
    for (User::op_iterator i = N->op_begin(), e = N->op_end(); i != e; ++i) {
      DenseMap<Value *, Value *>::iterator PI = TranslateMap.find(*i);
      if (PI != TranslateMap.end())
        *i = PI->second;
    }

    // Check for trivial simplification.
    if (Value *V = SimplifyInstruction(N, {DL, nullptr, nullptr, AC})) {
      if (!BBI->use_empty())
        TranslateMap[&*BBI] = V;
      if (!N->mayHaveSideEffects()) {
        N->deleteValue(); // Instruction folded away, don't need actual inst
        N = nullptr;
      }
    } else {
      if (!BBI->use_empty())
        TranslateMap[&*BBI] = N;
    }
    if (N) {
      // Insert the new instruction into its new home.
      EdgeBB->getInstList().insert(InsertPt, N);

      // Register the new instruction with the assumption cache if necessary.
      if (AC && match(N, m_Intrinsic<Intrinsic::assume>()))
        AC->registerAssumption(cast<IntrinsicInst>(N));
    }
  }

  // Loop over all of the edges from PredBB to BB, changing them to branch
  // to EdgeBB instead.
  Instruction *PredBBTI = PredBB->getTerminator();
  for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
    if (PredBBTI->getSuccessor(i) == BB) {
      BB->removePredecessor(PredBB);
      PredBBTI->setSuccessor(i, EdgeBB);
    }

  Updates.push_back({DominatorTree::Insert, PredBB, EdgeBB});
  Updates.push_back({DominatorTree::Delete, PredBB, BB});

  if (DTU)
    DTU->applyUpdates(Updates);

  // Recurse, simplifying any other constants.
  return FoldCondBranchOnPHI(BI, DTU, DL, AC) || true;
}

return false;
2512}

2514/// Given a BB that starts with the specified two-entry PHI node,
2515/// see if we can eliminate it.
2516static bool FoldTwoEntryPHINode(PHINode *PN, const TargetTransformInfo &TTI,
                              DomTreeUpdater *DTU, const DataLayout &DL) {
// Ok, this is a two entry PHI node.  Check to see if this is a simple "if
// statement", which has a very simple dominance structure.  Basically, we
// are trying to find the condition that is being branched on, which
// subsequently causes this merge to happen.  We really want control
// dependence information for this check, but simplifycfg can't keep it up
// to date, and this catches most of the cases we care about anyway.
BasicBlock *BB = PN->getParent();

BasicBlock *IfTrue, *IfFalse;
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
if (!IfCond ||
    // Don't bother if the branch will be constant folded trivially.
    isa<ConstantInt>(IfCond))
  return false;

// Okay, we found that we can merge this two-entry phi node into a select.
// Doing so would require us to fold *all* two entry phi nodes in this block.
// At some point this becomes non-profitable (particularly if the target
// doesn't support cmov's).  Only do this transformation if there are two or
// fewer PHI nodes in this block.
unsigned NumPhis = 0;
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I)
  if (NumPhis > 2)
    return false;

// Loop over the PHI's seeing if we can promote them all to select
// instructions.  While we are at it, keep track of the instructions
// that need to be moved to the dominating block.
SmallPtrSet<Instruction *, 4> AggressiveInsts;
int BudgetRemaining =
    TwoEntryPHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic;

bool Changed = false;
for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) {
  PHINode *PN = cast<PHINode>(II++);
  if (Value *V = SimplifyInstruction(PN, {DL, PN})) {
    PN->replaceAllUsesWith(V);
    PN->eraseFromParent();
    Changed = true;
    continue;
  }

  if (!DominatesMergePoint(PN->getIncomingValue(0), BB, AggressiveInsts,
                           BudgetRemaining, TTI) ||
      !DominatesMergePoint(PN->getIncomingValue(1), BB, AggressiveInsts,
                           BudgetRemaining, TTI))
    return Changed;
}

// If we folded the first phi, PN dangles at this point.  Refresh it.  If
// we ran out of PHIs then we simplified them all.
PN = dyn_cast<PHINode>(BB->begin());
if (!PN)
  return true;

// Return true if at least one of these is a 'not', and another is either
// a 'not' too, or a constant.
auto CanHoistNotFromBothValues = [](Value *V0, Value *V1) {
  if (!match(V0, m_Not(m_Value())))
    std::swap(V0, V1);
  auto Invertible = m_CombineOr(m_Not(m_Value()), m_AnyIntegralConstant());
  return match(V0, m_Not(m_Value())) && match(V1, Invertible);
};

// Don't fold i1 branches on PHIs which contain binary operators, unless one
// of the incoming values is an 'not' and another one is freely invertible.
// These can often be turned into switches and other things.
if (PN->getType()->isIntegerTy(1) &&
    (isa<BinaryOperator>(PN->getIncomingValue(0)) ||
     isa<BinaryOperator>(PN->getIncomingValue(1)) ||
     isa<BinaryOperator>(IfCond)) &&
    !CanHoistNotFromBothValues(PN->getIncomingValue(0),
                               PN->getIncomingValue(1)))
  return Changed;

// If all PHI nodes are promotable, check to make sure that all instructions
// in the predecessor blocks can be promoted as well. If not, we won't be able
// to get rid of the control flow, so it's not worth promoting to select
// instructions.
BasicBlock *DomBlock = nullptr;
BasicBlock *IfBlock1 = PN->getIncomingBlock(0);
BasicBlock *IfBlock2 = PN->getIncomingBlock(1);
if (cast<BranchInst>(IfBlock1->getTerminator())->isConditional()) {
  IfBlock1 = nullptr;
} else {
  DomBlock = *pred_begin(IfBlock1);
  for (BasicBlock::iterator I = IfBlock1->begin(); !I->isTerminator(); ++I)
    if (!AggressiveInsts.count(&*I) && !isa<DbgInfoIntrinsic>(I) &&
        !isa<PseudoProbeInst>(I)) {
      // This is not an aggressive instruction that we can promote.
      // Because of this, we won't be able to get rid of the control flow, so
      // the xform is not worth it.
      return Changed;
    }
}

if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) {
  IfBlock2 = nullptr;
} else {
  DomBlock = *pred_begin(IfBlock2);
  for (BasicBlock::iterator I = IfBlock2->begin(); !I->isTerminator(); ++I)
    if (!AggressiveInsts.count(&*I) && !isa<DbgInfoIntrinsic>(I) &&
        !isa<PseudoProbeInst>(I)) {
      // This is not an aggressive instruction that we can promote.
      // Because of this, we won't be able to get rid of the control flow, so
      // the xform is not worth it.
      return Changed;
    }
}
assert(DomBlock && "Failed to find root DomBlock")((DomBlock && "Failed to find root DomBlock") ? static_cast
<void> (0) : __assert_fail ("DomBlock && \"Failed to find root DomBlock\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 2627, __PRETTY_FUNCTION__));

LLVM_DEBUG(dbgs() << "FOUND IF CONDITION!  " << *IfConddo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOUND IF CONDITION!  " <<
 *IfCond << "  T: " << IfTrue->getName() <<
 "  F: " << IfFalse->getName() << "\n"; } } while
 (false)
                  << "  T: " << IfTrue->getName()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOUND IF CONDITION!  " <<
 *IfCond << "  T: " << IfTrue->getName() <<
 "  F: " << IfFalse->getName() << "\n"; } } while
 (false)
                  << "  F: " << IfFalse->getName() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOUND IF CONDITION!  " <<
 *IfCond << "  T: " << IfTrue->getName() <<
 "  F: " << IfFalse->getName() << "\n"; } } while
 (false);

// If we can still promote the PHI nodes after this gauntlet of tests,
// do all of the PHI's now.
Instruction *InsertPt = DomBlock->getTerminator();
IRBuilder<NoFolder> Builder(InsertPt);

// Move all 'aggressive' instructions, which are defined in the
// conditional parts of the if's up to the dominating block.
if (IfBlock1)
  hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock1);
if (IfBlock2)
  hoistAllInstructionsInto(DomBlock, InsertPt, IfBlock2);

// Propagate fast-math-flags from phi nodes to replacement selects.
IRBuilder<>::FastMathFlagGuard FMFGuard(Builder);
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
  if (isa<FPMathOperator>(PN))
    Builder.setFastMathFlags(PN->getFastMathFlags());

  // Change the PHI node into a select instruction.
  Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
  Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);

  Value *Sel = Builder.CreateSelect(IfCond, TrueVal, FalseVal, "", InsertPt);
  PN->replaceAllUsesWith(Sel);
  Sel->takeName(PN);
  PN->eraseFromParent();
}

// At this point, IfBlock1 and IfBlock2 are both empty, so our if statement
// has been flattened.  Change DomBlock to jump directly to our new block to
// avoid other simplifycfg's kicking in on the diamond.
Instruction *OldTI = DomBlock->getTerminator();
Builder.SetInsertPoint(OldTI);
Builder.CreateBr(BB);

SmallVector<DominatorTree::UpdateType, 3> Updates;
if (DTU) {
  Updates.push_back({DominatorTree::Insert, DomBlock, BB});
  for (auto *Successor : successors(DomBlock))
    Updates.push_back({DominatorTree::Delete, DomBlock, Successor});
}

OldTI->eraseFromParent();
if (DTU)
  DTU->applyUpdates(Updates);

return true;
2680}

2682/// If we found a conditional branch that goes to two returning blocks,
2683/// try to merge them together into one return,
2684/// introducing a select if the return values disagree.
2685bool SimplifyCFGOpt::SimplifyCondBranchToTwoReturns(BranchInst *BI,
                                                  IRBuilder<> &Builder) {
auto *BB = BI->getParent();
assert(BI->isConditional() && "Must be a conditional branch")((BI->isConditional() && "Must be a conditional branch"
) ? static_cast<void> (0) : __assert_fail ("BI->isConditional() && \"Must be a conditional branch\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 2688, __PRETTY_FUNCTION__));
BasicBlock *TrueSucc = BI->getSuccessor(0);
BasicBlock *FalseSucc = BI->getSuccessor(1);
// NOTE: destinations may match, this could be degenerate uncond branch.
ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator());
ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator());

// Check to ensure both blocks are empty (just a return) or optionally empty
// with PHI nodes.  If there are other instructions, merging would cause extra
// computation on one path or the other.
if (!TrueSucc->getFirstNonPHIOrDbg()->isTerminator())
  return false;
if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator())
  return false;

Builder.SetInsertPoint(BI);
// Okay, we found a branch that is going to two return nodes.  If
// there is no return value for this function, just change the
// branch into a return.
if (FalseRet->getNumOperands() == 0) {
  TrueSucc->removePredecessor(BB);
  FalseSucc->removePredecessor(BB);
  Builder.CreateRetVoid();
  EraseTerminatorAndDCECond(BI);
  if (DTU) {
    SmallVector<DominatorTree::UpdateType, 2> Updates;
    Updates.push_back({DominatorTree::Delete, BB, TrueSucc});
    if (TrueSucc != FalseSucc)
      Updates.push_back({DominatorTree::Delete, BB, FalseSucc});
    DTU->applyUpdates(Updates);
  }
  return true;
}

// Otherwise, figure out what the true and false return values are
// so we can insert a new select instruction.
Value *TrueValue = TrueRet->getReturnValue();
Value *FalseValue = FalseRet->getReturnValue();

// Unwrap any PHI nodes in the return blocks.
if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue))
  if (TVPN->getParent() == TrueSucc)
    TrueValue = TVPN->getIncomingValueForBlock(BB);
if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue))
  if (FVPN->getParent() == FalseSucc)
    FalseValue = FVPN->getIncomingValueForBlock(BB);

// In order for this transformation to be safe, we must be able to
// unconditionally execute both operands to the return.  This is
// normally the case, but we could have a potentially-trapping
// constant expression that prevents this transformation from being
// safe.
if (ConstantExpr *TCV = dyn_cast_or_null<ConstantExpr>(TrueValue))
  if (TCV->canTrap())
    return false;
if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue))
  if (FCV->canTrap())
    return false;

// Okay, we collected all the mapped values and checked them for sanity, and
// defined to really do this transformation.  First, update the CFG.
TrueSucc->removePredecessor(BB);
FalseSucc->removePredecessor(BB);

// Insert select instructions where needed.
Value *BrCond = BI->getCondition();
if (TrueValue) {
  // Insert a select if the results differ.
  if (TrueValue == FalseValue || isa<UndefValue>(FalseValue)) {
  } else if (isa<UndefValue>(TrueValue)) {
    TrueValue = FalseValue;
  } else {
    TrueValue =
        Builder.CreateSelect(BrCond, TrueValue, FalseValue, "retval", BI);
  }
}

Value *RI =
    !TrueValue ? Builder.CreateRetVoid() : Builder.CreateRet(TrueValue);

(void)RI;

LLVM_DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
 << "\n  " << *BI << "\nNewRet = " <<
 *RI << "\nTRUEBLOCK: " << *TrueSucc << "\nFALSEBLOCK: "
 << *FalseSucc; } } while (false)
                  << "\n  " << *BI << "\nNewRet = " << *RI << "\nTRUEBLOCK: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
 << "\n  " << *BI << "\nNewRet = " <<
 *RI << "\nTRUEBLOCK: " << *TrueSucc << "\nFALSEBLOCK: "
 << *FalseSucc; } } while (false)
                  << *TrueSucc << "\nFALSEBLOCK: " << *FalseSucc)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
 << "\n  " << *BI << "\nNewRet = " <<
 *RI << "\nTRUEBLOCK: " << *TrueSucc << "\nFALSEBLOCK: "
 << *FalseSucc; } } while (false);

EraseTerminatorAndDCECond(BI);
if (DTU) {
  SmallVector<DominatorTree::UpdateType, 2> Updates;
  Updates.push_back({DominatorTree::Delete, BB, TrueSucc});
  if (TrueSucc != FalseSucc)
    Updates.push_back({DominatorTree::Delete, BB, FalseSucc});
  DTU->applyUpdates(Updates);
}

return true;
2784}

2786/// Return true if the given instruction is available
2787/// in its predecessor block. If yes, the instruction will be removed.
2788static bool tryCSEWithPredecessor(Instruction *Inst, BasicBlock *PB) {
if (!isa<BinaryOperator>(Inst) && !isa<CmpInst>(Inst))
  return false;
for (Instruction &I : *PB) {
  Instruction *PBI = &I;
  // Check whether Inst and PBI generate the same value.
  if (Inst->isIdenticalTo(PBI)) {
    Inst->replaceAllUsesWith(PBI);
    Inst->eraseFromParent();
    return true;
  }
}
return false;
2801}

2803/// Return true if either PBI or BI has branch weight available, and store
2804/// the weights in {Pred|Succ}{True|False}Weight. If one of PBI and BI does
2805/// not have branch weight, use 1:1 as its weight.
2806static bool extractPredSuccWeights(BranchInst *PBI, BranchInst *BI,
                                 uint64_t &PredTrueWeight,
                                 uint64_t &PredFalseWeight,
                                 uint64_t &SuccTrueWeight,
                                 uint64_t &SuccFalseWeight) {
bool PredHasWeights =
    PBI->extractProfMetadata(PredTrueWeight, PredFalseWeight);
bool SuccHasWeights =
    BI->extractProfMetadata(SuccTrueWeight, SuccFalseWeight);
if (PredHasWeights || SuccHasWeights) {
  if (!PredHasWeights)
    PredTrueWeight = PredFalseWeight = 1;
  if (!SuccHasWeights)
    SuccTrueWeight = SuccFalseWeight = 1;
  return true;
} else {
  return false;
}
2824}

2826/// If this basic block is simple enough, and if a predecessor branches to us
2827/// and one of our successors, fold the block into the predecessor and use
2828/// logical operations to pick the right destination.
2829bool llvm::FoldBranchToCommonDest(BranchInst *BI, DomTreeUpdater *DTU,
                                MemorySSAUpdater *MSSAU,
                                const TargetTransformInfo *TTI,
                                unsigned BonusInstThreshold) {
BasicBlock *BB = BI->getParent();

const unsigned PredCount = pred_size(BB);

bool Changed = false;

auto _ = make_scope_exit([&]() {
  if (Changed)
    ++NumFoldBranchToCommonDest;
});

TargetTransformInfo::TargetCostKind CostKind =
  BB->getParent()->hasMinSize() ? TargetTransformInfo::TCK_CodeSize
1
Assuming the condition is false→
2
←
'?' condition is false→
                                : TargetTransformInfo::TCK_SizeAndLatency;

Instruction *Cond = nullptr;
if (BI->isConditional())
3
←
Calling 'BranchInst::isConditional'→
6
←
Returning from 'BranchInst::isConditional'→
7
←
Taking true branch→
  Cond = dyn_cast<Instruction>(BI->getCondition());
8
←
Assuming the object is a 'Instruction'→
else {
  // For unconditional branch, check for a simple CFG pattern, where
  // BB has a single predecessor and BB's successor is also its predecessor's
  // successor. If such pattern exists, check for CSE between BB and its
  // predecessor.
  if (BasicBlock *PB = BB->getSinglePredecessor())
    if (BranchInst *PBI = dyn_cast<BranchInst>(PB->getTerminator()))
      if (PBI->isConditional() &&
          (BI->getSuccessor(0) == PBI->getSuccessor(0) ||
           BI->getSuccessor(0) == PBI->getSuccessor(1))) {
        for (auto I = BB->instructionsWithoutDebug().begin(),
                  E = BB->instructionsWithoutDebug().end();
             I != E;) {
          Instruction *Curr = &*I++;
          if (isa<CmpInst>(Curr)) {
            Cond = Curr;
            break;
          }
          // Quit if we can't remove this instruction.
          if (!tryCSEWithPredecessor(Curr, PB))
            return Changed;
          Changed = true;
        }
      }

  if (!Cond)
    return Changed;
}

if (!Cond8.1
'Cond' is non-null
1
'Cond' is non-null
1
'Cond' is non-null
1
'Cond' is non-null
1
'Cond' is non-null
1
'Cond' is non-null
 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
9
←
Assuming 'Cond' is not a 'CmpInst'→
10
←
Assuming 'Cond' is a 'BinaryOperator'→
20
←
Taking false branch→
    Cond->getParent() != BB || !Cond->hasOneUse())
11
←
Assuming the condition is false→
12
←
Calling 'Value::hasOneUse'→
18
←
Returning from 'Value::hasOneUse'→
19
←
Assuming the condition is false→
  return Changed;

// Only allow this transformation if computing the condition doesn't involve
// too many instructions and these involved instructions can be executed
// unconditionally. We denote all involved instructions except the condition
// as "bonus instructions", and only allow this transformation when the
// number of the bonus instructions we'll need to create when cloning into
// each predecessor does not exceed a certain threshold.
unsigned NumBonusInsts = 0;
for (Instruction &I : *BB) {
  // Don't check the branch condition comparison itself.
  if (&I == Cond)
    continue;
  // Ignore dbg intrinsics, and the terminator.
  if (isa<DbgInfoIntrinsic>(I) || isa<BranchInst>(I))
    continue;
  // I must be safe to execute unconditionally.
  if (!isSafeToSpeculativelyExecute(&I))
    return Changed;

  // Account for the cost of duplicating this instruction into each
  // predecessor.
  NumBonusInsts += PredCount;
  // Early exits once we reach the limit.
  if (NumBonusInsts > BonusInstThreshold)
    return Changed;
}

// Also, for now, all liveout uses of bonus instructions must be in PHI nodes
// in successor blocks as incoming values from the bonus instructions's block,
// otherwise we'll fail to update them.
// FIXME: We could lift this restriction, but we need to form PHI nodes and
// rewrite offending uses, but we can't do that without having a domtree.
if (any_of(*BB, [BB](Instruction &I) {
21
←
Calling 'any_of<llvm::BasicBlock &, (lambda at /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp:2915:19)>'→
32
←
Returning from 'any_of<llvm::BasicBlock &, (lambda at /build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp:2915:19)>'→
33
←
Taking false branch→
      return any_of(I.uses(), [BB](Use &U) {
        auto *User = cast<Instruction>(U.getUser());
        if (User->getParent() == BB)
          return false; // Not an external use.
        auto *PN = dyn_cast<PHINode>(User);
        return !PN || PN->getIncomingBlock(U) != BB;
      });
    }))
  return Changed;

// Cond is known to be a compare or binary operator.  Check to make sure that
// neither operand is a potentially-trapping constant expression.
if (ConstantExpr *CE34.1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
 = dyn_cast<ConstantExpr>(Cond->getOperand(0)))
34
←
Assuming the object is not a 'ConstantExpr'→
35
←
Taking false branch→
  if (CE->canTrap())
    return Changed;
if (ConstantExpr *CE36.1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
1
'CE' is null
 = dyn_cast<ConstantExpr>(Cond->getOperand(1)))
36
←
Assuming the object is not a 'ConstantExpr'→
37
←
Taking false branch→
  if (CE->canTrap())
    return Changed;

// Finally, don't infinitely unroll conditional loops.
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = (BI->isConditional()) ? BI->getSuccessor(1) : nullptr;
38
←
'?' condition is true→
if (TrueDest38.1
'TrueDest' is not equal to 'BB'
1
'TrueDest' is not equal to 'BB'
1
'TrueDest' is not equal to 'BB'
1
'TrueDest' is not equal to 'BB'
1
'TrueDest' is not equal to 'BB'
1
'TrueDest' is not equal to 'BB'
 == BB || FalseDest38.2
'FalseDest' is not equal to 'BB'
2
'FalseDest' is not equal to 'BB'
2
'FalseDest' is not equal to 'BB'
2
'FalseDest' is not equal to 'BB'
2
'FalseDest' is not equal to 'BB'
2
'FalseDest' is not equal to 'BB'
 == BB)
39
←
Taking false branch→
  return Changed;

for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
40
←
Loop condition is true.  Entering loop body→
  BasicBlock *PredBlock = *PI;
  BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
41
←
Assuming the object is a 'BranchInst'→

  // Check that we have two conditional branches.  If there is a PHI node in
  // the common successor, verify that the same value flows in from both
  // blocks.
  SmallVector<PHINode *, 4> PHIs;
  if (!PBI41.1
'PBI' is non-null
1
'PBI' is non-null
1
'PBI' is non-null
1
'PBI' is non-null
1
'PBI' is non-null
1
'PBI' is non-null
 || PBI->isUnconditional() ||
42
←
Calling 'BranchInst::isUnconditional'→
45
←
Returning from 'BranchInst::isUnconditional'→
      (BI->isConditional() && !SafeToMergeTerminators(BI, PBI)) ||
46
←
Calling 'BranchInst::isConditional'→
48
←
Returning from 'BranchInst::isConditional'→
49
←
Calling 'SafeToMergeTerminators'→
53
←
Returning from 'SafeToMergeTerminators'→
      (!BI->isConditional() &&
54
←
Calling 'BranchInst::isConditional'→
56
←
Returning from 'BranchInst::isConditional'→
       !isProfitableToFoldUnconditional(BI, PBI, Cond, PHIs)))
    continue;

  // Determine if the two branches share a common destination.
  Instruction::BinaryOps Opc = Instruction::BinaryOpsEnd;
  bool InvertPredCond = false;

  if (BI->isConditional()) {
57
←
Calling 'BranchInst::isConditional'→
59
←
Returning from 'BranchInst::isConditional'→
60
←
Taking true branch→
    if (PBI->getSuccessor(0) == TrueDest) {
61
←
Taking true branch→
      Opc = Instruction::Or;
    } else if (PBI->getSuccessor(1) == FalseDest) {
      Opc = Instruction::And;
    } else if (PBI->getSuccessor(0) == FalseDest) {
      Opc = Instruction::And;
      InvertPredCond = true;
    } else if (PBI->getSuccessor(1) == TrueDest) {
      Opc = Instruction::Or;
      InvertPredCond = true;
    } else {
      continue;
    }
  } else {
    if (PBI->getSuccessor(0) != TrueDest && PBI->getSuccessor(1) != TrueDest)
      continue;
  }

  // Check the cost of inserting the necessary logic before performing the
  // transformation.
  if (TTI && Opc != Instruction::BinaryOpsEnd) {
62
←
Assuming 'TTI' is null→
    Type *Ty = BI->getCondition()->getType();
    unsigned Cost = TTI->getArithmeticInstrCost(Opc, Ty, CostKind);
    if (InvertPredCond && (!PBI->getCondition()->hasOneUse() ||
        !isa<CmpInst>(PBI->getCondition())))
      Cost += TTI->getArithmeticInstrCost(Instruction::Xor, Ty, CostKind);

    if (Cost > BranchFoldThreshold)
      continue;
  }

  LLVM_DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOLDING BRANCH TO COMMON DEST:\n"
 << *PBI << *BB; } } while (false);
63
←
Assuming 'DebugFlag' is false→
64
←
Loop condition is false.  Exiting loop→
  Changed = true;

  SmallVector<DominatorTree::UpdateType, 3> Updates;

  IRBuilder<> Builder(PBI);
  // The builder is used to create instructions to eliminate the branch in BB.
  // If BB's terminator has !annotation metadata, add it to the new
  // instructions.
  Builder.CollectMetadataToCopy(BB->getTerminator(),
                                {LLVMContext::MD_annotation});

  // If we need to invert the condition in the pred block to match, do so now.
  if (InvertPredCond64.1
'InvertPredCond' is false
1
'InvertPredCond' is false
1
'InvertPredCond' is false
1
'InvertPredCond' is false
1
'InvertPredCond' is false
1
'InvertPredCond' is false
) {
65
←
Taking false branch→
    Value *NewCond = PBI->getCondition();
    if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
      CmpInst *CI = cast<CmpInst>(NewCond);
      CI->setPredicate(CI->getInversePredicate());
    } else {
      NewCond =
          Builder.CreateNot(NewCond, PBI->getCondition()->getName() + ".not");
    }

    PBI->setCondition(NewCond);
    PBI->swapSuccessors();
  }

  BasicBlock *UniqueSucc =
      BI->isConditional()
66
←
'?' condition is true→
          ? (PBI->getSuccessor(0) == BB ? TrueDest : FalseDest)
67
←
'?' condition is false→
          : TrueDest;

  // Before cloning instructions, notify the successor basic block that it
  // is about to have a new predecessor. This will update PHI nodes,
  // which will allow us to update live-out uses of bonus instructions.
  if (BI->isConditional())
68
←
Taking true branch→
    AddPredecessorToBlock(UniqueSucc, PredBlock, BB, MSSAU);

  // If we have bonus instructions, clone them into the predecessor block.
  // Note that there may be multiple predecessor blocks, so we cannot move
  // bonus instructions to a predecessor block.
  ValueToValueMapTy VMap; // maps original values to cloned values
  Instruction *CondInPred;
69
←
'CondInPred' declared without an initial value→
  for (Instruction &BonusInst : *BB) {
    if (isa<DbgInfoIntrinsic>(BonusInst) || isa<BranchInst>(BonusInst))
      continue;

    Instruction *NewBonusInst = BonusInst.clone();

    if (&BonusInst == Cond)
      CondInPred = NewBonusInst;

    if (PBI->getDebugLoc() != NewBonusInst->getDebugLoc()) {
      // Unless the instruction has the same !dbg location as the original
      // branch, drop it. When we fold the bonus instructions we want to make
      // sure we reset their debug locations in order to avoid stepping on
      // dead code caused by folding dead branches.
      NewBonusInst->setDebugLoc(DebugLoc());
    }

    RemapInstruction(NewBonusInst, VMap,
                     RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
    VMap[&BonusInst] = NewBonusInst;

    // If we moved a load, we cannot any longer claim any knowledge about
    // its potential value. The previous information might have been valid
    // only given the branch precondition.
    // For an analogous reason, we must also drop all the metadata whose
    // semantics we don't understand. We *can* preserve !annotation, because
    // it is tied to the instruction itself, not the value or position.
    NewBonusInst->dropUnknownNonDebugMetadata(LLVMContext::MD_annotation);

    PredBlock->getInstList().insert(PBI->getIterator(), NewBonusInst);
    NewBonusInst->takeName(&BonusInst);
    BonusInst.setName(BonusInst.getName() + ".old");
    BonusInst.replaceUsesWithIf(
        NewBonusInst, [BB, BI, UniqueSucc, PredBlock](Use &U) {
          auto *User = cast<Instruction>(U.getUser());
          // Ignore non-external uses of bonus instructions.
          if (User->getParent() == BB) {
            assert(!isa<PHINode>(User) &&((!isa<PHINode>(User) && "Non-external users are never PHI instructions."
) ? static_cast<void> (0) : __assert_fail ("!isa<PHINode>(User) && \"Non-external users are never PHI instructions.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3072, __PRETTY_FUNCTION__))
                   "Non-external users are never PHI instructions.")((!isa<PHINode>(User) && "Non-external users are never PHI instructions."
) ? static_cast<void> (0) : __assert_fail ("!isa<PHINode>(User) && \"Non-external users are never PHI instructions.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3072, __PRETTY_FUNCTION__));
            return false;
          }
          if (User->getParent() == PredBlock) {
            // The "exteral" use is in the block into which we just cloned the
            // bonus instruction. This means two things: 1. we are in an
            // unreachable block 2. the instruction is self-referencing.
            // So let's just rewrite it...
            return true;
          }
          (void)BI;
          assert(isa<PHINode>(User) && "All external users must be PHI's.")((isa<PHINode>(User) && "All external users must be PHI's."
) ? static_cast<void> (0) : __assert_fail ("isa<PHINode>(User) && \"All external users must be PHI's.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3083, __PRETTY_FUNCTION__));
          auto *PN = cast<PHINode>(User);
          assert(is_contained(successors(BB), User->getParent()) &&((is_contained(successors(BB), User->getParent()) &&
 "All external users must be in successors of BB.") ? static_cast
<void> (0) : __assert_fail ("is_contained(successors(BB), User->getParent()) && \"All external users must be in successors of BB.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3086, __PRETTY_FUNCTION__))
                 "All external users must be in successors of BB.")((is_contained(successors(BB), User->getParent()) &&
 "All external users must be in successors of BB.") ? static_cast
<void> (0) : __assert_fail ("is_contained(successors(BB), User->getParent()) && \"All external users must be in successors of BB.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3086, __PRETTY_FUNCTION__));
          assert((PN->getIncomingBlock(U) == BB ||(((PN->getIncomingBlock(U) == BB || PN->getIncomingBlock
(U) == PredBlock) && "The incoming block for that incoming value external use "
 "must be either the original block with bonus instructions, "
 "or the new predecessor block.") ? static_cast<void> (
0) : __assert_fail ("(PN->getIncomingBlock(U) == BB || PN->getIncomingBlock(U) == PredBlock) && \"The incoming block for that incoming value external use \" \"must be either the original block with bonus instructions, \" \"or the new predecessor block.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3091, __PRETTY_FUNCTION__))
                  PN->getIncomingBlock(U) == PredBlock) &&(((PN->getIncomingBlock(U) == BB || PN->getIncomingBlock
(U) == PredBlock) && "The incoming block for that incoming value external use "
 "must be either the original block with bonus instructions, "
 "or the new predecessor block.") ? static_cast<void> (
0) : __assert_fail ("(PN->getIncomingBlock(U) == BB || PN->getIncomingBlock(U) == PredBlock) && \"The incoming block for that incoming value external use \" \"must be either the original block with bonus instructions, \" \"or the new predecessor block.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3091, __PRETTY_FUNCTION__))
                 "The incoming block for that incoming value external use "(((PN->getIncomingBlock(U) == BB || PN->getIncomingBlock
(U) == PredBlock) && "The incoming block for that incoming value external use "
 "must be either the original block with bonus instructions, "
 "or the new predecessor block.") ? static_cast<void> (
0) : __assert_fail ("(PN->getIncomingBlock(U) == BB || PN->getIncomingBlock(U) == PredBlock) && \"The incoming block for that incoming value external use \" \"must be either the original block with bonus instructions, \" \"or the new predecessor block.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3091, __PRETTY_FUNCTION__))
                 "must be either the original block with bonus instructions, "(((PN->getIncomingBlock(U) == BB || PN->getIncomingBlock
(U) == PredBlock) && "The incoming block for that incoming value external use "
 "must be either the original block with bonus instructions, "
 "or the new predecessor block.") ? static_cast<void> (
0) : __assert_fail ("(PN->getIncomingBlock(U) == BB || PN->getIncomingBlock(U) == PredBlock) && \"The incoming block for that incoming value external use \" \"must be either the original block with bonus instructions, \" \"or the new predecessor block.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3091, __PRETTY_FUNCTION__))
                 "or the new predecessor block.")(((PN->getIncomingBlock(U) == BB || PN->getIncomingBlock
(U) == PredBlock) && "The incoming block for that incoming value external use "
 "must be either the original block with bonus instructions, "
 "or the new predecessor block.") ? static_cast<void> (
0) : __assert_fail ("(PN->getIncomingBlock(U) == BB || PN->getIncomingBlock(U) == PredBlock) && \"The incoming block for that incoming value external use \" \"must be either the original block with bonus instructions, \" \"or the new predecessor block.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3091, __PRETTY_FUNCTION__));
          // UniqueSucc is the block for which we change it's predecessors,
          // so it is the only block in which we'll need to update PHI nodes.
          if (User->getParent() != UniqueSucc)
            return false;
          // Update the incoming value for the new predecessor.
          return PN->getIncomingBlock(U) ==
                 (BI->isConditional() ? PredBlock : BB);
        });
  }

  // Now that the Cond was cloned into the predecessor basic block,
  // or/and the two conditions together.
  if (BI->isConditional()) {
70
←
Calling 'BranchInst::isConditional'→
72
←
Returning from 'BranchInst::isConditional'→
73
←
Taking true branch→
    Instruction *NewCond = cast<Instruction>(
        Builder.CreateBinOp(Opc, PBI->getCondition(), CondInPred, "or.cond"));
74
←
3rd function call argument is an uninitialized value
    PBI->setCondition(NewCond);

    uint64_t PredTrueWeight, PredFalseWeight, SuccTrueWeight, SuccFalseWeight;
    bool HasWeights =
        extractPredSuccWeights(PBI, BI, PredTrueWeight, PredFalseWeight,
                               SuccTrueWeight, SuccFalseWeight);
    SmallVector<uint64_t, 8> NewWeights;

    if (PBI->getSuccessor(0) == BB) {
      if (HasWeights) {
        // PBI: br i1 %x, BB, FalseDest
        // BI:  br i1 %y, UniqueSucc, FalseDest
        // TrueWeight is TrueWeight for PBI * TrueWeight for BI.
        NewWeights.push_back(PredTrueWeight * SuccTrueWeight);
        // FalseWeight is FalseWeight for PBI * TotalWeight for BI +
        //               TrueWeight for PBI * FalseWeight for BI.
        // We assume that total weights of a BranchInst can fit into 32 bits.
        // Therefore, we will not have overflow using 64-bit arithmetic.
        NewWeights.push_back(PredFalseWeight *
                                 (SuccFalseWeight + SuccTrueWeight) +
                             PredTrueWeight * SuccFalseWeight);
      }
      PBI->setSuccessor(0, UniqueSucc);
    }
    if (PBI->getSuccessor(1) == BB) {
      if (HasWeights) {
        // PBI: br i1 %x, TrueDest, BB
        // BI:  br i1 %y, TrueDest, UniqueSucc
        // TrueWeight is TrueWeight for PBI * TotalWeight for BI +
        //              FalseWeight for PBI * TrueWeight for BI.
        NewWeights.push_back(PredTrueWeight *
                                 (SuccFalseWeight + SuccTrueWeight) +
                             PredFalseWeight * SuccTrueWeight);
        // FalseWeight is FalseWeight for PBI * FalseWeight for BI.
        NewWeights.push_back(PredFalseWeight * SuccFalseWeight);
      }
      PBI->setSuccessor(1, UniqueSucc);
    }
    if (NewWeights.size() == 2) {
      // Halve the weights if any of them cannot fit in an uint32_t
      FitWeights(NewWeights);

      SmallVector<uint32_t, 8> MDWeights(NewWeights.begin(),
                                         NewWeights.end());
      setBranchWeights(PBI, MDWeights[0], MDWeights[1]);
    } else
      PBI->setMetadata(LLVMContext::MD_prof, nullptr);

    Updates.push_back({DominatorTree::Insert, PredBlock, UniqueSucc});
    Updates.push_back({DominatorTree::Delete, PredBlock, BB});
  } else {
    // Update PHI nodes in the common successors.
    for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
      ConstantInt *PBI_C = cast<ConstantInt>(
          PHIs[i]->getIncomingValueForBlock(PBI->getParent()));
      assert(PBI_C->getType()->isIntegerTy(1))((PBI_C->getType()->isIntegerTy(1)) ? static_cast<void
> (0) : __assert_fail ("PBI_C->getType()->isIntegerTy(1)"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3162, __PRETTY_FUNCTION__));
      Instruction *MergedCond = nullptr;
      if (PBI->getSuccessor(0) == UniqueSucc) {
        Updates.push_back(
            {DominatorTree::Delete, PredBlock, PBI->getSuccessor(1)});
        // Create (PBI_Cond and PBI_C) or (!PBI_Cond and BI_Value)
        // PBI_C is true: PBI_Cond or (!PBI_Cond and BI_Value)
        //       is false: !PBI_Cond and BI_Value
        Instruction *NotCond = cast<Instruction>(
            Builder.CreateNot(PBI->getCondition(), "not.cond"));
        MergedCond = cast<Instruction>(
             Builder.CreateBinOp(Instruction::And, NotCond, CondInPred,
                                 "and.cond"));
        if (PBI_C->isOne())
          MergedCond = cast<Instruction>(Builder.CreateBinOp(
              Instruction::Or, PBI->getCondition(), MergedCond, "or.cond"));
      } else {
        assert(PBI->getSuccessor(1) == UniqueSucc && "Unexpected branch")((PBI->getSuccessor(1) == UniqueSucc && "Unexpected branch"
) ? static_cast<void> (0) : __assert_fail ("PBI->getSuccessor(1) == UniqueSucc && \"Unexpected branch\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3179, __PRETTY_FUNCTION__));
        Updates.push_back(
            {DominatorTree::Delete, PredBlock, PBI->getSuccessor(0)});
        // Create (PBI_Cond and BI_Value) or (!PBI_Cond and PBI_C)
        // PBI_C is true: (PBI_Cond and BI_Value) or (!PBI_Cond)
        //       is false: PBI_Cond and BI_Value
        MergedCond = cast<Instruction>(Builder.CreateBinOp(
            Instruction::And, PBI->getCondition(), CondInPred, "and.cond"));
        if (PBI_C->isOne()) {
          Instruction *NotCond = cast<Instruction>(
              Builder.CreateNot(PBI->getCondition(), "not.cond"));
          MergedCond = cast<Instruction>(Builder.CreateBinOp(
              Instruction::Or, NotCond, MergedCond, "or.cond"));
        }
      }
      // Update PHI Node.
      PHIs[i]->setIncomingValueForBlock(PBI->getParent(), MergedCond);
    }

    // PBI is changed to branch to UniqueSucc below. Remove itself from
    // potential phis from all other successors.
    if (MSSAU)
      MSSAU->changeCondBranchToUnconditionalTo(PBI, UniqueSucc);

    // Change PBI from Conditional to Unconditional.
    BranchInst *New_PBI = BranchInst::Create(UniqueSucc, PBI);
    EraseTerminatorAndDCECond(PBI, MSSAU);
    PBI = New_PBI;
  }

  if (DTU)
    DTU->applyUpdates(Updates);

  // If BI was a loop latch, it may have had associated loop metadata.
  // We need to copy it to the new latch, that is, PBI.
  if (MDNode *LoopMD = BI->getMetadata(LLVMContext::MD_loop))
    PBI->setMetadata(LLVMContext::MD_loop, LoopMD);

  // TODO: If BB is reachable from all paths through PredBlock, then we
  // could replace PBI's branch probabilities with BI's.

  // Copy any debug value intrinsics into the end of PredBlock.
  for (Instruction &I : *BB) {
    if (isa<DbgInfoIntrinsic>(I)) {
      Instruction *NewI = I.clone();
      RemapInstruction(NewI, VMap,
                       RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
      NewI->insertBefore(PBI);
    }
  }

  return Changed;
}
return Changed;
3233}

3235// If there is only one store in BB1 and BB2, return it, otherwise return
3236// nullptr.
3237static StoreInst *findUniqueStoreInBlocks(BasicBlock *BB1, BasicBlock *BB2) {
StoreInst *S = nullptr;
for (auto *BB : {BB1, BB2}) {
  if (!BB)
    continue;
  for (auto &I : *BB)
    if (auto *SI = dyn_cast<StoreInst>(&I)) {
      if (S)
        // Multiple stores seen.
        return nullptr;
      else
        S = SI;
    }
}
return S;
3252}

3254static Value *ensureValueAvailableInSuccessor(Value *V, BasicBlock *BB,
                                            Value *AlternativeV = nullptr) {
// PHI is going to be a PHI node that allows the value V that is defined in
// BB to be referenced in BB's only successor.
//
// If AlternativeV is nullptr, the only value we care about in PHI is V. It
// doesn't matter to us what the other operand is (it'll never get used). We
// could just create a new PHI with an undef incoming value, but that could
// increase register pressure if EarlyCSE/InstCombine can't fold it with some
// other PHI. So here we directly look for some PHI in BB's successor with V
// as an incoming operand. If we find one, we use it, else we create a new
// one.
//
// If AlternativeV is not nullptr, we care about both incoming values in PHI.
// PHI must be exactly: phi <ty> [ %BB, %V ], [ %OtherBB, %AlternativeV]
// where OtherBB is the single other predecessor of BB's only successor.
PHINode *PHI = nullptr;
BasicBlock *Succ = BB->getSingleSuccessor();

for (auto I = Succ->begin(); isa<PHINode>(I); ++I)
  if (cast<PHINode>(I)->getIncomingValueForBlock(BB) == V) {
    PHI = cast<PHINode>(I);
    if (!AlternativeV)
      break;

    assert(Succ->hasNPredecessors(2))((Succ->hasNPredecessors(2)) ? static_cast<void> (0)
 : __assert_fail ("Succ->hasNPredecessors(2)", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3279, __PRETTY_FUNCTION__));
    auto PredI = pred_begin(Succ);
    BasicBlock *OtherPredBB = *PredI == BB ? *++PredI : *PredI;
    if (PHI->getIncomingValueForBlock(OtherPredBB) == AlternativeV)
      break;
    PHI = nullptr;
  }
if (PHI)
  return PHI;

// If V is not an instruction defined in BB, just return it.
if (!AlternativeV &&
    (!isa<Instruction>(V) || cast<Instruction>(V)->getParent() != BB))
  return V;

PHI = PHINode::Create(V->getType(), 2, "simplifycfg.merge", &Succ->front());
PHI->addIncoming(V, BB);
for (BasicBlock *PredBB : predecessors(Succ))
  if (PredBB != BB)
    PHI->addIncoming(
        AlternativeV ? AlternativeV : UndefValue::get(V->getType()), PredBB);
return PHI;
3301}

3303static bool mergeConditionalStoreToAddress(
  BasicBlock *PTB, BasicBlock *PFB, BasicBlock *QTB, BasicBlock *QFB,
  BasicBlock *PostBB, Value *Address, bool InvertPCond, bool InvertQCond,
  DomTreeUpdater *DTU, const DataLayout &DL, const TargetTransformInfo &TTI) {
// For every pointer, there must be exactly two stores, one coming from
// PTB or PFB, and the other from QTB or QFB. We don't support more than one
// store (to any address) in PTB,PFB or QTB,QFB.
// FIXME: We could relax this restriction with a bit more work and performance
// testing.
StoreInst *PStore = findUniqueStoreInBlocks(PTB, PFB);
StoreInst *QStore = findUniqueStoreInBlocks(QTB, QFB);
if (!PStore || !QStore)
  return false;

// Now check the stores are compatible.
if (!QStore->isUnordered() || !PStore->isUnordered())
  return false;

// Check that sinking the store won't cause program behavior changes. Sinking
// the store out of the Q blocks won't change any behavior as we're sinking
// from a block to its unconditional successor. But we're moving a store from
// the P blocks down through the middle block (QBI) and past both QFB and QTB.
// So we need to check that there are no aliasing loads or stores in
// QBI, QTB and QFB. We also need to check there are no conflicting memory
// operations between PStore and the end of its parent block.
//
// The ideal way to do this is to query AliasAnalysis, but we don't
// preserve AA currently so that is dangerous. Be super safe and just
// check there are no other memory operations at all.
for (auto &I : *QFB->getSinglePredecessor())
  if (I.mayReadOrWriteMemory())
    return false;
for (auto &I : *QFB)
  if (&I != QStore && I.mayReadOrWriteMemory())
    return false;
if (QTB)
  for (auto &I : *QTB)
    if (&I != QStore && I.mayReadOrWriteMemory())
      return false;
for (auto I = BasicBlock::iterator(PStore), E = PStore->getParent()->end();
     I != E; ++I)
  if (&*I != PStore && I->mayReadOrWriteMemory())
    return false;

// If we're not in aggressive mode, we only optimize if we have some
// confidence that by optimizing we'll allow P and/or Q to be if-converted.
auto IsWorthwhile = [&](BasicBlock *BB, ArrayRef<StoreInst *> FreeStores) {
  if (!BB)
    return true;
  // Heuristic: if the block can be if-converted/phi-folded and the
  // instructions inside are all cheap (arithmetic/GEPs), it's worthwhile to
  // thread this store.
  int BudgetRemaining =
      PHINodeFoldingThreshold * TargetTransformInfo::TCC_Basic;
  for (auto &I : BB->instructionsWithoutDebug()) {
    // Consider terminator instruction to be free.
    if (I.isTerminator())
      continue;
    // If this is one the stores that we want to speculate out of this BB,
    // then don't count it's cost, consider it to be free.
    if (auto *S = dyn_cast<StoreInst>(&I))
      if (llvm::find(FreeStores, S))
        continue;
    // Else, we have a white-list of instructions that we are ak speculating.
    if (!isa<BinaryOperator>(I) && !isa<GetElementPtrInst>(I))
      return false; // Not in white-list - not worthwhile folding.
    // And finally, if this is a non-free instruction that we are okay
    // speculating, ensure that we consider the speculation budget.
    BudgetRemaining -= TTI.getUserCost(&I, TargetTransformInfo::TCK_SizeAndLatency);
    if (BudgetRemaining < 0)
      return false; // Eagerly refuse to fold as soon as we're out of budget.
  }
  assert(BudgetRemaining >= 0 &&((BudgetRemaining >= 0 && "When we run out of budget we will eagerly return from within the "
 "per-instruction loop.") ? static_cast<void> (0) : __assert_fail
 ("BudgetRemaining >= 0 && \"When we run out of budget we will eagerly return from within the \" \"per-instruction loop.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3377, __PRETTY_FUNCTION__))
         "When we run out of budget we will eagerly return from within the "((BudgetRemaining >= 0 && "When we run out of budget we will eagerly return from within the "
 "per-instruction loop.") ? static_cast<void> (0) : __assert_fail
 ("BudgetRemaining >= 0 && \"When we run out of budget we will eagerly return from within the \" \"per-instruction loop.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3377, __PRETTY_FUNCTION__))
         "per-instruction loop.")((BudgetRemaining >= 0 && "When we run out of budget we will eagerly return from within the "
 "per-instruction loop.") ? static_cast<void> (0) : __assert_fail
 ("BudgetRemaining >= 0 && \"When we run out of budget we will eagerly return from within the \" \"per-instruction loop.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3377, __PRETTY_FUNCTION__));
  return true;
};

const std::array<StoreInst *, 2> FreeStores = {PStore, QStore};
if (!MergeCondStoresAggressively &&
    (!IsWorthwhile(PTB, FreeStores) || !IsWorthwhile(PFB, FreeStores) ||
     !IsWorthwhile(QTB, FreeStores) || !IsWorthwhile(QFB, FreeStores)))
  return false;

// If PostBB has more than two predecessors, we need to split it so we can
// sink the store.
if (std::next(pred_begin(PostBB), 2) != pred_end(PostBB)) {
  // We know that QFB's only successor is PostBB. And QFB has a single
  // predecessor. If QTB exists, then its only successor is also PostBB.
  // If QTB does not exist, then QFB's only predecessor has a conditional
  // branch to QFB and PostBB.
  BasicBlock *TruePred = QTB ? QTB : QFB->getSinglePredecessor();
  BasicBlock *NewBB =
      SplitBlockPredecessors(PostBB, {QFB, TruePred}, "condstore.split", DTU);
  if (!NewBB)
    return false;
  PostBB = NewBB;
}

// OK, we're going to sink the stores to PostBB. The store has to be
// conditional though, so first create the predicate.
Value *PCond = cast<BranchInst>(PFB->getSinglePredecessor()->getTerminator())
                   ->getCondition();
Value *QCond = cast<BranchInst>(QFB->getSinglePredecessor()->getTerminator())
                   ->getCondition();

Value *PPHI = ensureValueAvailableInSuccessor(PStore->getValueOperand(),
                                              PStore->getParent());
Value *QPHI = ensureValueAvailableInSuccessor(QStore->getValueOperand(),
                                              QStore->getParent(), PPHI);

IRBuilder<> QB(&*PostBB->getFirstInsertionPt());

Value *PPred = PStore->getParent() == PTB ? PCond : QB.CreateNot(PCond);
Value *QPred = QStore->getParent() == QTB ? QCond : QB.CreateNot(QCond);

if (InvertPCond)
  PPred = QB.CreateNot(PPred);
if (InvertQCond)
  QPred = QB.CreateNot(QPred);
Value *CombinedPred = QB.CreateOr(PPred, QPred);

auto *T = SplitBlockAndInsertIfThen(CombinedPred, &*QB.GetInsertPoint(),
                                    /*Unreachable=*/false,
                                    /*BranchWeights=*/nullptr, DTU);
QB.SetInsertPoint(T);
StoreInst *SI = cast<StoreInst>(QB.CreateStore(QPHI, Address));
AAMDNodes AAMD;
PStore->getAAMetadata(AAMD, /*Merge=*/false);
PStore->getAAMetadata(AAMD, /*Merge=*/true);
SI->setAAMetadata(AAMD);
// Choose the minimum alignment. If we could prove both stores execute, we
// could use biggest one.  In this case, though, we only know that one of the
// stores executes.  And we don't know it's safe to take the alignment from a
// store that doesn't execute.
SI->setAlignment(std::min(PStore->getAlign(), QStore->getAlign()));

QStore->eraseFromParent();
PStore->eraseFromParent();

return true;
3444}

3446static bool mergeConditionalStores(BranchInst *PBI, BranchInst *QBI,
                                 DomTreeUpdater *DTU, const DataLayout &DL,
                                 const TargetTransformInfo &TTI) {
// The intention here is to find diamonds or triangles (see below) where each
// conditional block contains a store to the same address. Both of these
// stores are conditional, so they can't be unconditionally sunk. But it may
// be profitable to speculatively sink the stores into one merged store at the
// end, and predicate the merged store on the union of the two conditions of
// PBI and QBI.
//
// This can reduce the number of stores executed if both of the conditions are
// true, and can allow the blocks to become small enough to be if-converted.
// This optimization will also chain, so that ladders of test-and-set
// sequences can be if-converted away.
//
// We only deal with simple diamonds or triangles:
//
//     PBI       or      PBI        or a combination of the two
//    /   \               | \
//   PTB  PFB             |  PFB
//    \   /               | /
//     QBI                QBI
//    /  \                | \
//   QTB  QFB             |  QFB
//    \  /                | /
//    PostBB            PostBB
//
// We model triangles as a type of diamond with a nullptr "true" block.
// Triangles are canonicalized so that the fallthrough edge is represented by
// a true condition, as in the diagram above.
BasicBlock *PTB = PBI->getSuccessor(0);
BasicBlock *PFB = PBI->getSuccessor(1);
BasicBlock *QTB = QBI->getSuccessor(0);
BasicBlock *QFB = QBI->getSuccessor(1);
BasicBlock *PostBB = QFB->getSingleSuccessor();

// Make sure we have a good guess for PostBB. If QTB's only successor is
// QFB, then QFB is a better PostBB.
if (QTB->getSingleSuccessor() == QFB)
  PostBB = QFB;

// If we couldn't find a good PostBB, stop.
if (!PostBB)
  return false;

bool InvertPCond = false, InvertQCond = false;
// Canonicalize fallthroughs to the true branches.
if (PFB == QBI->getParent()) {
  std::swap(PFB, PTB);
  InvertPCond = true;
}
if (QFB == PostBB) {
  std::swap(QFB, QTB);
  InvertQCond = true;
}

// From this point on we can assume PTB or QTB may be fallthroughs but PFB
// and QFB may not. Model fallthroughs as a nullptr block.
if (PTB == QBI->getParent())
  PTB = nullptr;
if (QTB == PostBB)
  QTB = nullptr;

// Legality bailouts. We must have at least the non-fallthrough blocks and
// the post-dominating block, and the non-fallthroughs must only have one
// predecessor.
auto HasOnePredAndOneSucc = [](BasicBlock *BB, BasicBlock *P, BasicBlock *S) {
  return BB->getSinglePredecessor() == P && BB->getSingleSuccessor() == S;
};
if (!HasOnePredAndOneSucc(PFB, PBI->getParent(), QBI->getParent()) ||
    !HasOnePredAndOneSucc(QFB, QBI->getParent(), PostBB))
  return false;
if ((PTB && !HasOnePredAndOneSucc(PTB, PBI->getParent(), QBI->getParent())) ||
    (QTB && !HasOnePredAndOneSucc(QTB, QBI->getParent(), PostBB)))
  return false;
if (!QBI->getParent()->hasNUses(2))
  return false;

// OK, this is a sequence of two diamonds or triangles.
// Check if there are stores in PTB or PFB that are repeated in QTB or QFB.
SmallPtrSet<Value *, 4> PStoreAddresses, QStoreAddresses;
for (auto *BB : {PTB, PFB}) {
  if (!BB)
    continue;
  for (auto &I : *BB)
    if (StoreInst *SI = dyn_cast<StoreInst>(&I))
      PStoreAddresses.insert(SI->getPointerOperand());
}
for (auto *BB : {QTB, QFB}) {
  if (!BB)
    continue;
  for (auto &I : *BB)
    if (StoreInst *SI = dyn_cast<StoreInst>(&I))
      QStoreAddresses.insert(SI->getPointerOperand());
}

set_intersect(PStoreAddresses, QStoreAddresses);
// set_intersect mutates PStoreAddresses in place. Rename it here to make it
// clear what it contains.
auto &CommonAddresses = PStoreAddresses;

bool Changed = false;
for (auto *Address : CommonAddresses)
  Changed |=
      mergeConditionalStoreToAddress(PTB, PFB, QTB, QFB, PostBB, Address,
                                     InvertPCond, InvertQCond, DTU, DL, TTI);
return Changed;
3553}

3555/// If the previous block ended with a widenable branch, determine if reusing
3556/// the target block is profitable and legal.  This will have the effect of
3557/// "widening" PBI, but doesn't require us to reason about hosting safety.
3558static bool tryWidenCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI,
                                         DomTreeUpdater *DTU) {
// TODO: This can be generalized in two important ways:
// 1) We can allow phi nodes in IfFalseBB and simply reuse all the input
//    values from the PBI edge.
// 2) We can sink side effecting instructions into BI's fallthrough
//    successor provided they doesn't contribute to computation of
//    BI's condition.
Value *CondWB, *WC;
BasicBlock *IfTrueBB, *IfFalseBB;
if (!parseWidenableBranch(PBI, CondWB, WC, IfTrueBB, IfFalseBB) ||
    IfTrueBB != BI->getParent() || !BI->getParent()->getSinglePredecessor())
  return false;
if (!IfFalseBB->phis().empty())
  return false; // TODO
// Use lambda to lazily compute expensive condition after cheap ones.
auto NoSideEffects = [](BasicBlock &BB) {
  return !llvm::any_of(BB, [](const Instruction &I) {
      return I.mayWriteToMemory() || I.mayHaveSideEffects();
    });
};
if (BI->getSuccessor(1) != IfFalseBB && // no inf looping
    BI->getSuccessor(1)->getTerminatingDeoptimizeCall() && // profitability
    NoSideEffects(*BI->getParent())) {
  auto *OldSuccessor = BI->getSuccessor(1);
  OldSuccessor->removePredecessor(BI->getParent());
  BI->setSuccessor(1, IfFalseBB);
  if (DTU)
    DTU->applyUpdates(
        {{DominatorTree::Insert, BI->getParent(), IfFalseBB},
         {DominatorTree::Delete, BI->getParent(), OldSuccessor}});
  return true;
}
if (BI->getSuccessor(0) != IfFalseBB && // no inf looping
    BI->getSuccessor(0)->getTerminatingDeoptimizeCall() && // profitability
    NoSideEffects(*BI->getParent())) {
  auto *OldSuccessor = BI->getSuccessor(0);
  OldSuccessor->removePredecessor(BI->getParent());
  BI->setSuccessor(0, IfFalseBB);
  if (DTU)
    DTU->applyUpdates(
        {{DominatorTree::Insert, BI->getParent(), IfFalseBB},
         {DominatorTree::Delete, BI->getParent(), OldSuccessor}});
  return true;
}
return false;
3604}

3606/// If we have a conditional branch as a predecessor of another block,
3607/// this function tries to simplify it.  We know
3608/// that PBI and BI are both conditional branches, and BI is in one of the
3609/// successor blocks of PBI - PBI branches to BI.
3610static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI,
                                         DomTreeUpdater *DTU,
                                         const DataLayout &DL,
                                         const TargetTransformInfo &TTI) {
assert(PBI->isConditional() && BI->isConditional())((PBI->isConditional() && BI->isConditional()) ?
 static_cast<void> (0) : __assert_fail ("PBI->isConditional() && BI->isConditional()"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 3614, __PRETTY_FUNCTION__));
BasicBlock *BB = BI->getParent();

// If this block ends with a branch instruction, and if there is a
// predecessor that ends on a branch of the same condition, make
// this conditional branch redundant.
if (PBI->getCondition() == BI->getCondition() &&
    PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
  // Okay, the outcome of this conditional branch is statically
  // knowable.  If this block had a single pred, handle specially.
  if (BB->getSinglePredecessor()) {
    // Turn this into a branch on constant.
    bool CondIsTrue = PBI->getSuccessor(0) == BB;
    BI->setCondition(
        ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue));
    return true; // Nuke the branch on constant.
  }

  // Otherwise, if there are multiple predecessors, insert a PHI that merges
  // in the constant and simplify the block result.  Subsequent passes of
  // simplifycfg will thread the block.
  if (BlockIsSimpleEnoughToThreadThrough(BB)) {
    pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
    PHINode *NewPN = PHINode::Create(
        Type::getInt1Ty(BB->getContext()), std::distance(PB, PE),
        BI->getCondition()->getName() + ".pr", &BB->front());
    // Okay, we're going to insert the PHI node.  Since PBI is not the only
    // predecessor, compute the PHI'd conditional value for all of the preds.
    // Any predecessor where the condition is not computable we keep symbolic.
    for (pred_iterator PI = PB; PI != PE; ++PI) {
      BasicBlock *P = *PI;
      if ((PBI = dyn_cast<BranchInst>(P->getTerminator())) && PBI != BI &&
          PBI->isConditional() && PBI->getCondition() == BI->getCondition() &&
          PBI->getSuccessor(0) != PBI->getSuccessor(1)) {
        bool CondIsTrue = PBI->getSuccessor(0) == BB;
        NewPN->addIncoming(
            ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue),
            P);
      } else {
        NewPN->addIncoming(BI->getCondition(), P);
      }
    }

    BI->setCondition(NewPN);
    return true;
  }
}

// If the previous block ended with a widenable branch, determine if reusing
// the target block is profitable and legal.  This will have the effect of
// "widening" PBI, but doesn't require us to reason about hosting safety.
if (tryWidenCondBranchToCondBranch(PBI, BI, DTU))
  return true;

if (auto *CE = dyn_cast<ConstantExpr>(BI->getCondition()))
  if (CE->canTrap())
    return false;

// If both branches are conditional and both contain stores to the same
// address, remove the stores from the conditionals and create a conditional
// merged store at the end.
if (MergeCondStores && mergeConditionalStores(PBI, BI, DTU, DL, TTI))
  return true;

// If this is a conditional branch in an empty block, and if any
// predecessors are a conditional branch to one of our destinations,
// fold the conditions into logical ops and one cond br.

// Ignore dbg intrinsics.
if (&*BB->instructionsWithoutDebug().begin() != BI)
  return false;

int PBIOp, BIOp;
if (PBI->getSuccessor(0) == BI->getSuccessor(0)) {
  PBIOp = 0;
  BIOp = 0;
} else if (PBI->getSuccessor(0) == BI->getSuccessor(1)) {
  PBIOp = 0;
  BIOp = 1;
} else if (PBI->getSuccessor(1) == BI->getSuccessor(0)) {
  PBIOp = 1;
  BIOp = 0;
} else if (PBI->getSuccessor(1) == BI->getSuccessor(1)) {
  PBIOp = 1;
  BIOp = 1;
} else {
  return false;
}

// Check to make sure that the other destination of this branch
// isn't BB itself.  If so, this is an infinite loop that will
// keep getting unwound.
if (PBI->getSuccessor(PBIOp) == BB)
  return false;

// Do not perform this transformation if it would require
// insertion of a large number of select instructions. For targets
// without predication/cmovs, this is a big pessimization.

// Also do not perform this transformation if any phi node in the common
// destination block can trap when reached by BB or PBB (PR17073). In that
// case, it would be unsafe to hoist the operation into a select instruction.

BasicBlock *CommonDest = PBI->getSuccessor(PBIOp);
BasicBlock *RemovedDest = PBI->getSuccessor(PBIOp ^ 1);
unsigned NumPhis = 0;
for (BasicBlock::iterator II = CommonDest->begin(); isa<PHINode>(II);
     ++II, ++NumPhis) {
  if (NumPhis > 2) // Disable this xform.
    return false;

  PHINode *PN = cast<PHINode>(II);
  Value *BIV = PN->getIncomingValueForBlock(BB);
  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BIV))
    if (CE->canTrap())
      return false;

  unsigned PBBIdx = PN->getBasicBlockIndex(PBI->getParent());
  Value *PBIV = PN->getIncomingValue(PBBIdx);
  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(PBIV))
    if (CE->canTrap())
      return false;
}

// Finally, if everything is ok, fold the branches to logical ops.
BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1);

LLVM_DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOLDING BRs:" << *PBI
->getParent() << "AND: " << *BI->getParent(
); } } while (false)
                  << "AND: " << *BI->getParent())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOLDING BRs:" << *PBI
->getParent() << "AND: " << *BI->getParent(
); } } while (false);

SmallVector<DominatorTree::UpdateType, 5> Updates;

// If OtherDest *is* BB, then BB is a basic block with a single conditional
// branch in it, where one edge (OtherDest) goes back to itself but the other
// exits.  We don't *know* that the program avoids the infinite loop
// (even though that seems likely).  If we do this xform naively, we'll end up
// recursively unpeeling the loop.  Since we know that (after the xform is
// done) that the block *is* infinite if reached, we just make it an obviously
// infinite loop with no cond branch.
if (OtherDest == BB) {
  // Insert it at the end of the function, because it's either code,
  // or it won't matter if it's hot. :)
  BasicBlock *InfLoopBlock =
      BasicBlock::Create(BB->getContext(), "infloop", BB->getParent());
  BranchInst::Create(InfLoopBlock, InfLoopBlock);
  Updates.push_back({DominatorTree::Insert, InfLoopBlock, InfLoopBlock});
  OtherDest = InfLoopBlock;
}

LLVM_DEBUG(dbgs() << *PBI->getParent()->getParent())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << *PBI->getParent()->getParent
(); } } while (false);

// BI may have other predecessors.  Because of this, we leave
// it alone, but modify PBI.

// Make sure we get to CommonDest on True&True directions.
Value *PBICond = PBI->getCondition();
IRBuilder<NoFolder> Builder(PBI);
if (PBIOp)
  PBICond = Builder.CreateNot(PBICond, PBICond->getName() + ".not");

Value *BICond = BI->getCondition();
if (BIOp)
  BICond = Builder.CreateNot(BICond, BICond->getName() + ".not");

// Merge the conditions.
Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge");

// Modify PBI to branch on the new condition to the new dests.
PBI->setCondition(Cond);
PBI->setSuccessor(0, CommonDest);
PBI->setSuccessor(1, OtherDest);

Updates.push_back({DominatorTree::Insert, PBI->getParent(), OtherDest});
Updates.push_back({DominatorTree::Delete, PBI->getParent(), RemovedDest});

if (DTU)
  DTU->applyUpdates(Updates);

// Update branch weight for PBI.
uint64_t PredTrueWeight, PredFalseWeight, SuccTrueWeight, SuccFalseWeight;
uint64_t PredCommon, PredOther, SuccCommon, SuccOther;
bool HasWeights =
    extractPredSuccWeights(PBI, BI, PredTrueWeight, PredFalseWeight,
                           SuccTrueWeight, SuccFalseWeight);
if (HasWeights) {
  PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight;
  PredOther = PBIOp ? PredTrueWeight : PredFalseWeight;
  SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight;
  SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight;
  // The weight to CommonDest should be PredCommon * SuccTotal +
  //                                    PredOther * SuccCommon.
  // The weight to OtherDest should be PredOther * SuccOther.
  uint64_t NewWeights[2] = {PredCommon * (SuccCommon + SuccOther) +
                                PredOther * SuccCommon,
                            PredOther * SuccOther};
  // Halve the weights if any of them cannot fit in an uint32_t
  FitWeights(NewWeights);

  setBranchWeights(PBI, NewWeights[0], NewWeights[1]);
}

// OtherDest may have phi nodes.  If so, add an entry from PBI's
// block that are identical to the entries for BI's block.
AddPredecessorToBlock(OtherDest, PBI->getParent(), BB);

// We know that the CommonDest already had an edge from PBI to
// it.  If it has PHIs though, the PHIs may have different
// entries for BB and PBI's BB.  If so, insert a select to make
// them agree.
for (PHINode &PN : CommonDest->phis()) {
  Value *BIV = PN.getIncomingValueForBlock(BB);
  unsigned PBBIdx = PN.getBasicBlockIndex(PBI->getParent());
  Value *PBIV = PN.getIncomingValue(PBBIdx);
  if (BIV != PBIV) {
    // Insert a select in PBI to pick the right value.
    SelectInst *NV = cast<SelectInst>(
        Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName() + ".mux"));
    PN.setIncomingValue(PBBIdx, NV);
    // Although the select has the same condition as PBI, the original branch
    // weights for PBI do not apply to the new select because the select's
    // 'logical' edges are incoming edges of the phi that is eliminated, not
    // the outgoing edges of PBI.
    if (HasWeights) {
      uint64_t PredCommon = PBIOp ? PredFalseWeight : PredTrueWeight;
      uint64_t PredOther = PBIOp ? PredTrueWeight : PredFalseWeight;
      uint64_t SuccCommon = BIOp ? SuccFalseWeight : SuccTrueWeight;
      uint64_t SuccOther = BIOp ? SuccTrueWeight : SuccFalseWeight;
      // The weight to PredCommonDest should be PredCommon * SuccTotal.
      // The weight to PredOtherDest should be PredOther * SuccCommon.
      uint64_t NewWeights[2] = {PredCommon * (SuccCommon + SuccOther),
                                PredOther * SuccCommon};

      FitWeights(NewWeights);

      setBranchWeights(NV, NewWeights[0], NewWeights[1]);
    }
  }
}

LLVM_DEBUG(dbgs() << "INTO: " << *PBI->getParent())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "INTO: " << *PBI->
getParent(); } } while (false);
LLVM_DEBUG(dbgs() << *PBI->getParent()->getParent())do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << *PBI->getParent()->getParent
(); } } while (false);

// This basic block is probably dead.  We know it has at least
// one fewer predecessor.
return true;
3859}

3861// Simplifies a terminator by replacing it with a branch to TrueBB if Cond is
3862// true or to FalseBB if Cond is false.
3863// Takes care of updating the successors and removing the old terminator.
3864// Also makes sure not to introduce new successors by assuming that edges to
3865// non-successor TrueBBs and FalseBBs aren't reachable.
3866bool SimplifyCFGOpt::SimplifyTerminatorOnSelect(Instruction *OldTerm,
                                              Value *Cond, BasicBlock *TrueBB,
                                              BasicBlock *FalseBB,
                                              uint32_t TrueWeight,
                                              uint32_t FalseWeight) {
auto *BB = OldTerm->getParent();
// Remove any superfluous successor edges from the CFG.
// First, figure out which successors to preserve.
// If TrueBB and FalseBB are equal, only try to preserve one copy of that
// successor.
BasicBlock *KeepEdge1 = TrueBB;
BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : nullptr;

SmallSetVector<BasicBlock *, 2> RemovedSuccessors;

// Then remove the rest.
for (BasicBlock *Succ : successors(OldTerm)) {
  // Make sure only to keep exactly one copy of each edge.
  if (Succ == KeepEdge1)
    KeepEdge1 = nullptr;
  else if (Succ == KeepEdge2)
    KeepEdge2 = nullptr;
  else {
    Succ->removePredecessor(BB,
                            /*KeepOneInputPHIs=*/true);

    if (Succ != TrueBB && Succ != FalseBB)
      RemovedSuccessors.insert(Succ);
  }
}

IRBuilder<> Builder(OldTerm);
Builder.SetCurrentDebugLocation(OldTerm->getDebugLoc());

// Insert an appropriate new terminator.
if (!KeepEdge1 && !KeepEdge2) {
  if (TrueBB == FalseBB) {
    // We were only looking for one successor, and it was present.
    // Create an unconditional branch to it.
    Builder.CreateBr(TrueBB);
  } else {
    // We found both of the successors we were looking for.
    // Create a conditional branch sharing the condition of the select.
    BranchInst *NewBI = Builder.CreateCondBr(Cond, TrueBB, FalseBB);
    if (TrueWeight != FalseWeight)
      setBranchWeights(NewBI, TrueWeight, FalseWeight);
  }
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
  // Neither of the selected blocks were successors, so this
  // terminator must be unreachable.
  new UnreachableInst(OldTerm->getContext(), OldTerm);
} else {
  // One of the selected values was a successor, but the other wasn't.
  // Insert an unconditional branch to the one that was found;
  // the edge to the one that wasn't must be unreachable.
  if (!KeepEdge1) {
    // Only TrueBB was found.
    Builder.CreateBr(TrueBB);
  } else {
    // Only FalseBB was found.
    Builder.CreateBr(FalseBB);
  }
}

EraseTerminatorAndDCECond(OldTerm);

if (DTU) {
  SmallVector<DominatorTree::UpdateType, 2> Updates;
  Updates.reserve(RemovedSuccessors.size());
  for (auto *RemovedSuccessor : RemovedSuccessors)
    Updates.push_back({DominatorTree::Delete, BB, RemovedSuccessor});
  DTU->applyUpdates(Updates);
}

return true;
3941}

3943// Replaces
3944//   (switch (select cond, X, Y)) on constant X, Y
3945// with a branch - conditional if X and Y lead to distinct BBs,
3946// unconditional otherwise.
3947bool SimplifyCFGOpt::SimplifySwitchOnSelect(SwitchInst *SI,
                                          SelectInst *Select) {
// Check for constant integer values in the select.
ConstantInt *TrueVal = dyn_cast<ConstantInt>(Select->getTrueValue());
ConstantInt *FalseVal = dyn_cast<ConstantInt>(Select->getFalseValue());
if (!TrueVal || !FalseVal)
  return false;

// Find the relevant condition and destinations.
Value *Condition = Select->getCondition();
BasicBlock *TrueBB = SI->findCaseValue(TrueVal)->getCaseSuccessor();
BasicBlock *FalseBB = SI->findCaseValue(FalseVal)->getCaseSuccessor();

// Get weight for TrueBB and FalseBB.
uint32_t TrueWeight = 0, FalseWeight = 0;
SmallVector<uint64_t, 8> Weights;
bool HasWeights = HasBranchWeights(SI);
if (HasWeights) {
  GetBranchWeights(SI, Weights);
  if (Weights.size() == 1 + SI->getNumCases()) {
    TrueWeight =
        (uint32_t)Weights[SI->findCaseValue(TrueVal)->getSuccessorIndex()];
    FalseWeight =
        (uint32_t)Weights[SI->findCaseValue(FalseVal)->getSuccessorIndex()];
  }
}

// Perform the actual simplification.
return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB, TrueWeight,
                                  FalseWeight);
3977}

3979// Replaces
3980//   (indirectbr (select cond, blockaddress(@fn, BlockA),
3981//                             blockaddress(@fn, BlockB)))
3982// with
3983//   (br cond, BlockA, BlockB).
3984bool SimplifyCFGOpt::SimplifyIndirectBrOnSelect(IndirectBrInst *IBI,
                                              SelectInst *SI) {
// Check that both operands of the select are block addresses.
BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue());
BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue());
if (!TBA || !FBA)
  return false;

// Extract the actual blocks.
BasicBlock *TrueBB = TBA->getBasicBlock();
BasicBlock *FalseBB = FBA->getBasicBlock();

// Perform the actual simplification.
return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB, 0,
                                  0);
3999}

4001/// This is called when we find an icmp instruction
4002/// (a seteq/setne with a constant) as the only instruction in a
4003/// block that ends with an uncond branch.  We are looking for a very specific
4004/// pattern that occurs when "A == 1 || A == 2 || A == 3" gets simplified.  In
4005/// this case, we merge the first two "or's of icmp" into a switch, but then the
4006/// default value goes to an uncond block with a seteq in it, we get something
4007/// like:
4008///
4009///   switch i8 %A, label %DEFAULT [ i8 1, label %end    i8 2, label %end ]
4010/// DEFAULT:
4011///   %tmp = icmp eq i8 %A, 92
4012///   br label %end
4013/// end:
4014///   ... = phi i1 [ true, %entry ], [ %tmp, %DEFAULT ], [ true, %entry ]
4015///
4016/// We prefer to split the edge to 'end' so that there is a true/false entry to
4017/// the PHI, merging the third icmp into the switch.
4018bool SimplifyCFGOpt::tryToSimplifyUncondBranchWithICmpInIt(
  ICmpInst *ICI, IRBuilder<> &Builder) {
BasicBlock *BB = ICI->getParent();

// If the block has any PHIs in it or the icmp has multiple uses, it is too
// complex.
if (isa<PHINode>(BB->begin()) || !ICI->hasOneUse())
  return false;

Value *V = ICI->getOperand(0);
ConstantInt *Cst = cast<ConstantInt>(ICI->getOperand(1));

// The pattern we're looking for is where our only predecessor is a switch on
// 'V' and this block is the default case for the switch.  In this case we can
// fold the compared value into the switch to simplify things.
BasicBlock *Pred = BB->getSinglePredecessor();
if (!Pred || !isa<SwitchInst>(Pred->getTerminator()))
  return false;

SwitchInst *SI = cast<SwitchInst>(Pred->getTerminator());
if (SI->getCondition() != V)
  return false;

// If BB is reachable on a non-default case, then we simply know the value of
// V in this block.  Substitute it and constant fold the icmp instruction
// away.
if (SI->getDefaultDest() != BB) {
  ConstantInt *VVal = SI->findCaseDest(BB);
  assert(VVal && "Should have a unique destination value")((VVal && "Should have a unique destination value") ?
 static_cast<void> (0) : __assert_fail ("VVal && \"Should have a unique destination value\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4046, __PRETTY_FUNCTION__));
  ICI->setOperand(0, VVal);

  if (Value *V = SimplifyInstruction(ICI, {DL, ICI})) {
    ICI->replaceAllUsesWith(V);
    ICI->eraseFromParent();
  }
  // BB is now empty, so it is likely to simplify away.
  return requestResimplify();
}

// Ok, the block is reachable from the default dest.  If the constant we're
// comparing exists in one of the other edges, then we can constant fold ICI
// and zap it.
if (SI->findCaseValue(Cst) != SI->case_default()) {
  Value *V;
  if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
    V = ConstantInt::getFalse(BB->getContext());
  else
    V = ConstantInt::getTrue(BB->getContext());

  ICI->replaceAllUsesWith(V);
  ICI->eraseFromParent();
  // BB is now empty, so it is likely to simplify away.
  return requestResimplify();
}

// The use of the icmp has to be in the 'end' block, by the only PHI node in
// the block.
BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0);
PHINode *PHIUse = dyn_cast<PHINode>(ICI->user_back());
if (PHIUse == nullptr || PHIUse != &SuccBlock->front() ||
    isa<PHINode>(++BasicBlock::iterator(PHIUse)))
  return false;

// If the icmp is a SETEQ, then the default dest gets false, the new edge gets
// true in the PHI.
Constant *DefaultCst = ConstantInt::getTrue(BB->getContext());
Constant *NewCst = ConstantInt::getFalse(BB->getContext());

if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
  std::swap(DefaultCst, NewCst);

// Replace ICI (which is used by the PHI for the default value) with true or
// false depending on if it is EQ or NE.
ICI->replaceAllUsesWith(DefaultCst);
ICI->eraseFromParent();

SmallVector<DominatorTree::UpdateType, 2> Updates;

// Okay, the switch goes to this block on a default value.  Add an edge from
// the switch to the merge point on the compared value.
BasicBlock *NewBB =
    BasicBlock::Create(BB->getContext(), "switch.edge", BB->getParent(), BB);
{
  SwitchInstProfUpdateWrapper SIW(*SI);
  auto W0 = SIW.getSuccessorWeight(0);
  SwitchInstProfUpdateWrapper::CaseWeightOpt NewW;
  if (W0) {
    NewW = ((uint64_t(*W0) + 1) >> 1);
    SIW.setSuccessorWeight(0, *NewW);
  }
  SIW.addCase(Cst, NewBB, NewW);
  Updates.push_back({DominatorTree::Insert, Pred, NewBB});
}

// NewBB branches to the phi block, add the uncond branch and the phi entry.
Builder.SetInsertPoint(NewBB);
Builder.SetCurrentDebugLocation(SI->getDebugLoc());
Builder.CreateBr(SuccBlock);
Updates.push_back({DominatorTree::Insert, NewBB, SuccBlock});
PHIUse->addIncoming(NewCst, NewBB);
if (DTU)
  DTU->applyUpdates(Updates);
return true;
4121}

4123/// The specified branch is a conditional branch.
4124/// Check to see if it is branching on an or/and chain of icmp instructions, and
4125/// fold it into a switch instruction if so.
4126bool SimplifyCFGOpt::SimplifyBranchOnICmpChain(BranchInst *BI,
                                             IRBuilder<> &Builder,
                                             const DataLayout &DL) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (!Cond)
  return false;

// Change br (X == 0 | X == 1), T, F into a switch instruction.
// If this is a bunch of seteq's or'd together, or if it's a bunch of
// 'setne's and'ed together, collect them.

// Try to gather values from a chain of and/or to be turned into a switch
ConstantComparesGatherer ConstantCompare(Cond, DL);
// Unpack the result
SmallVectorImpl<ConstantInt *> &Values = ConstantCompare.Vals;
Value *CompVal = ConstantCompare.CompValue;
unsigned UsedICmps = ConstantCompare.UsedICmps;
Value *ExtraCase = ConstantCompare.Extra;

// If we didn't have a multiply compared value, fail.
if (!CompVal)
  return false;

// Avoid turning single icmps into a switch.
if (UsedICmps <= 1)
  return false;

bool TrueWhenEqual = match(Cond, m_LogicalOr(m_Value(), m_Value()));

// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
Values.erase(std::unique(Values.begin(), Values.end()), Values.end());

// If Extra was used, we require at least two switch values to do the
// transformation.  A switch with one value is just a conditional branch.
if (ExtraCase && Values.size() < 2)
  return false;

// TODO: Preserve branch weight metadata, similarly to how
// FoldValueComparisonIntoPredecessors preserves it.

// Figure out which block is which destination.
BasicBlock *DefaultBB = BI->getSuccessor(1);
BasicBlock *EdgeBB = BI->getSuccessor(0);
if (!TrueWhenEqual)
  std::swap(DefaultBB, EdgeBB);

BasicBlock *BB = BI->getParent();

// MSAN does not like undefs as branch condition which can be introduced
// with "explicit branch".
if (ExtraCase && BB->getParent()->hasFnAttribute(Attribute::SanitizeMemory))
  return false;

LLVM_DEBUG(dbgs() << "Converting 'icmp' chain with " << Values.size()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Converting 'icmp' chain with "
 << Values.size() << " cases into SWITCH.  BB is:\n"
 << *BB; } } while (false)
                  << " cases into SWITCH.  BB is:\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Converting 'icmp' chain with "
 << Values.size() << " cases into SWITCH.  BB is:\n"
 << *BB; } } while (false)
                  << *BB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "Converting 'icmp' chain with "
 << Values.size() << " cases into SWITCH.  BB is:\n"
 << *BB; } } while (false);

SmallVector<DominatorTree::UpdateType, 2> Updates;

// If there are any extra values that couldn't be folded into the switch
// then we evaluate them with an explicit branch first. Split the block
// right before the condbr to handle it.
if (ExtraCase) {
  BasicBlock *NewBB = SplitBlock(BB, BI, DTU, /*LI=*/nullptr,
                                 /*MSSAU=*/nullptr, "switch.early.test");

  // Remove the uncond branch added to the old block.
  Instruction *OldTI = BB->getTerminator();
  Builder.SetInsertPoint(OldTI);

  if (TrueWhenEqual)
    Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB);
  else
    Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB);

  OldTI->eraseFromParent();

  Updates.push_back({DominatorTree::Insert, BB, EdgeBB});

  // If there are PHI nodes in EdgeBB, then we need to add a new entry to them
  // for the edge we just added.
  AddPredecessorToBlock(EdgeBB, BB, NewBB);

  LLVM_DEBUG(dbgs() << "  ** 'icmp' chain unhandled condition: " << *ExtraCasedo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "  ** 'icmp' chain unhandled condition: "
 << *ExtraCase << "\nEXTRABB = " << *BB; } }
 while (false)
                    << "\nEXTRABB = " << *BB)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "  ** 'icmp' chain unhandled condition: "
 << *ExtraCase << "\nEXTRABB = " << *BB; } }
 while (false);
  BB = NewBB;
}

Builder.SetInsertPoint(BI);
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
  CompVal = Builder.CreatePtrToInt(
      CompVal, DL.getIntPtrType(CompVal->getType()), "magicptr");
}

// Create the new switch instruction now.
SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());

// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
  New->addCase(Values[i], EdgeBB);

// We added edges from PI to the EdgeBB.  As such, if there were any
// PHI nodes in EdgeBB, they need entries to be added corresponding to
// the number of edges added.
for (BasicBlock::iterator BBI = EdgeBB->begin(); isa<PHINode>(BBI); ++BBI) {
  PHINode *PN = cast<PHINode>(BBI);
  Value *InVal = PN->getIncomingValueForBlock(BB);
  for (unsigned i = 0, e = Values.size() - 1; i != e; ++i)
    PN->addIncoming(InVal, BB);
}

// Erase the old branch instruction.
EraseTerminatorAndDCECond(BI);
if (DTU)
  DTU->applyUpdates(Updates);

LLVM_DEBUG(dbgs() << "  ** 'icmp' chain result is:\n" << *BB << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "  ** 'icmp' chain result is:\n"
 << *BB << '\n'; } } while (false);
return true;
4247}

4249bool SimplifyCFGOpt::simplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
if (isa<PHINode>(RI->getValue()))
  return simplifyCommonResume(RI);
else if (isa<LandingPadInst>(RI->getParent()->getFirstNonPHI()) &&
         RI->getValue() == RI->getParent()->getFirstNonPHI())
  // The resume must unwind the exception that caused control to branch here.
  return simplifySingleResume(RI);

return false;
4258}

4260// Check if cleanup block is empty
4261static bool isCleanupBlockEmpty(iterator_range<BasicBlock::iterator> R) {
for (Instruction &I : R) {
  auto *II = dyn_cast<IntrinsicInst>(&I);
  if (!II)
    return false;

  Intrinsic::ID IntrinsicID = II->getIntrinsicID();
  switch (IntrinsicID) {
  case Intrinsic::dbg_declare:
  case Intrinsic::dbg_value:
  case Intrinsic::dbg_label:
  case Intrinsic::lifetime_end:
    break;
  default:
    return false;
  }
}
return true;
4279}

4281// Simplify resume that is shared by several landing pads (phi of landing pad).
4282bool SimplifyCFGOpt::simplifyCommonResume(ResumeInst *RI) {
BasicBlock *BB = RI->getParent();

// Check that there are no other instructions except for debug and lifetime
// intrinsics between the phi's and resume instruction.
if (!isCleanupBlockEmpty(
        make_range(RI->getParent()->getFirstNonPHI(), BB->getTerminator())))
  return false;

SmallSetVector<BasicBlock *, 4> TrivialUnwindBlocks;
auto *PhiLPInst = cast<PHINode>(RI->getValue());

// Check incoming blocks to see if any of them are trivial.
for (unsigned Idx = 0, End = PhiLPInst->getNumIncomingValues(); Idx != End;
     Idx++) {
  auto *IncomingBB = PhiLPInst->getIncomingBlock(Idx);
  auto *IncomingValue = PhiLPInst->getIncomingValue(Idx);

  // If the block has other successors, we can not delete it because
  // it has other dependents.
  if (IncomingBB->getUniqueSuccessor() != BB)
    continue;

  auto *LandingPad = dyn_cast<LandingPadInst>(IncomingBB->getFirstNonPHI());
  // Not the landing pad that caused the control to branch here.
  if (IncomingValue != LandingPad)
    continue;

  if (isCleanupBlockEmpty(
          make_range(LandingPad->getNextNode(), IncomingBB->getTerminator())))
    TrivialUnwindBlocks.insert(IncomingBB);
}

// If no trivial unwind blocks, don't do any simplifications.
if (TrivialUnwindBlocks.empty())
  return false;

// Turn all invokes that unwind here into calls.
for (auto *TrivialBB : TrivialUnwindBlocks) {
  // Blocks that will be simplified should be removed from the phi node.
  // Note there could be multiple edges to the resume block, and we need
  // to remove them all.
  while (PhiLPInst->getBasicBlockIndex(TrivialBB) != -1)
    BB->removePredecessor(TrivialBB, true);

  for (pred_iterator PI = pred_begin(TrivialBB), PE = pred_end(TrivialBB);
       PI != PE;) {
    BasicBlock *Pred = *PI++;
    removeUnwindEdge(Pred, DTU);
    ++NumInvokes;
  }

  // In each SimplifyCFG run, only the current processed block can be erased.
  // Otherwise, it will break the iteration of SimplifyCFG pass. So instead
  // of erasing TrivialBB, we only remove the branch to the common resume
  // block so that we can later erase the resume block since it has no
  // predecessors.
  TrivialBB->getTerminator()->eraseFromParent();
  new UnreachableInst(RI->getContext(), TrivialBB);
  if (DTU)
    DTU->applyUpdates({{DominatorTree::Delete, TrivialBB, BB}});
}

// Delete the resume block if all its predecessors have been removed.
if (pred_empty(BB)) {
  if (DTU)
    DTU->deleteBB(BB);
  else
    BB->eraseFromParent();
}

return !TrivialUnwindBlocks.empty();
4354}

4356// Simplify resume that is only used by a single (non-phi) landing pad.
4357bool SimplifyCFGOpt::simplifySingleResume(ResumeInst *RI) {
BasicBlock *BB = RI->getParent();
auto *LPInst = cast<LandingPadInst>(BB->getFirstNonPHI());
assert(RI->getValue() == LPInst &&((RI->getValue() == LPInst && "Resume must unwind the exception that caused control to here"
) ? static_cast<void> (0) : __assert_fail ("RI->getValue() == LPInst && \"Resume must unwind the exception that caused control to here\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4361, __PRETTY_FUNCTION__))
       "Resume must unwind the exception that caused control to here")((RI->getValue() == LPInst && "Resume must unwind the exception that caused control to here"
) ? static_cast<void> (0) : __assert_fail ("RI->getValue() == LPInst && \"Resume must unwind the exception that caused control to here\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4361, __PRETTY_FUNCTION__));

// Check that there are no other instructions except for debug intrinsics.
if (!isCleanupBlockEmpty(
        make_range<Instruction *>(LPInst->getNextNode(), RI)))
  return false;

// Turn all invokes that unwind here into calls and delete the basic block.
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
  BasicBlock *Pred = *PI++;
  removeUnwindEdge(Pred, DTU);
  ++NumInvokes;
}

// The landingpad is now unreachable.  Zap it.
if (LoopHeaders)
  LoopHeaders->erase(BB);
if (DTU)
  DTU->deleteBB(BB);
else
  BB->eraseFromParent();
return true;
4383}

4385static bool removeEmptyCleanup(CleanupReturnInst *RI, DomTreeUpdater *DTU) {
// If this is a trivial cleanup pad that executes no instructions, it can be
// eliminated.  If the cleanup pad continues to the caller, any predecessor
// that is an EH pad will be updated to continue to the caller and any
// predecessor that terminates with an invoke instruction will have its invoke
// instruction converted to a call instruction.  If the cleanup pad being
// simplified does not continue to the caller, each predecessor will be
// updated to continue to the unwind destination of the cleanup pad being
// simplified.
BasicBlock *BB = RI->getParent();
CleanupPadInst *CPInst = RI->getCleanupPad();
if (CPInst->getParent() != BB)
  // This isn't an empty cleanup.
  return false;

// We cannot kill the pad if it has multiple uses.  This typically arises
// from unreachable basic blocks.
if (!CPInst->hasOneUse())
  return false;

// Check that there are no other instructions except for benign intrinsics.
if (!isCleanupBlockEmpty(
        make_range<Instruction *>(CPInst->getNextNode(), RI)))
  return false;

// If the cleanup return we are simplifying unwinds to the caller, this will
// set UnwindDest to nullptr.
BasicBlock *UnwindDest = RI->getUnwindDest();
Instruction *DestEHPad = UnwindDest ? UnwindDest->getFirstNonPHI() : nullptr;

// We're about to remove BB from the control flow.  Before we do, sink any
// PHINodes into the unwind destination.  Doing this before changing the
// control flow avoids some potentially slow checks, since we can currently
// be certain that UnwindDest and BB have no common predecessors (since they
// are both EH pads).
if (UnwindDest) {
  // First, go through the PHI nodes in UnwindDest and update any nodes that
  // reference the block we are removing
  for (BasicBlock::iterator I = UnwindDest->begin(),
                            IE = DestEHPad->getIterator();
       I != IE; ++I) {
    PHINode *DestPN = cast<PHINode>(I);

    int Idx = DestPN->getBasicBlockIndex(BB);
    // Since BB unwinds to UnwindDest, it has to be in the PHI node.
    assert(Idx != -1)((Idx != -1) ? static_cast<void> (0) : __assert_fail ("Idx != -1"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4430, __PRETTY_FUNCTION__));
    // This PHI node has an incoming value that corresponds to a control
    // path through the cleanup pad we are removing.  If the incoming
    // value is in the cleanup pad, it must be a PHINode (because we
    // verified above that the block is otherwise empty).  Otherwise, the
    // value is either a constant or a value that dominates the cleanup
    // pad being removed.
    //
    // Because BB and UnwindDest are both EH pads, all of their
    // predecessors must unwind to these blocks, and since no instruction
    // can have multiple unwind destinations, there will be no overlap in
    // incoming blocks between SrcPN and DestPN.
    Value *SrcVal = DestPN->getIncomingValue(Idx);
    PHINode *SrcPN = dyn_cast<PHINode>(SrcVal);

    // Remove the entry for the block we are deleting.
    DestPN->removeIncomingValue(Idx, false);

    if (SrcPN && SrcPN->getParent() == BB) {
      // If the incoming value was a PHI node in the cleanup pad we are
      // removing, we need to merge that PHI node's incoming values into
      // DestPN.
      for (unsigned SrcIdx = 0, SrcE = SrcPN->getNumIncomingValues();
           SrcIdx != SrcE; ++SrcIdx) {
        DestPN->addIncoming(SrcPN->getIncomingValue(SrcIdx),
                            SrcPN->getIncomingBlock(SrcIdx));
      }
    } else {
      // Otherwise, the incoming value came from above BB and
      // so we can just reuse it.  We must associate all of BB's
      // predecessors with this value.
      for (auto *pred : predecessors(BB)) {
        DestPN->addIncoming(SrcVal, pred);
      }
    }
  }

  // Sink any remaining PHI nodes directly into UnwindDest.
  Instruction *InsertPt = DestEHPad;
  for (BasicBlock::iterator I = BB->begin(),
                            IE = BB->getFirstNonPHI()->getIterator();
       I != IE;) {
    // The iterator must be incremented here because the instructions are
    // being moved to another block.
    PHINode *PN = cast<PHINode>(I++);
    if (PN->use_empty() || !PN->isUsedOutsideOfBlock(BB))
      // If the PHI node has no uses or all of its uses are in this basic
      // block (meaning they are debug or lifetime intrinsics), just leave
      // it.  It will be erased when we erase BB below.
      continue;

    // Otherwise, sink this PHI node into UnwindDest.
    // Any predecessors to UnwindDest which are not already represented
    // must be back edges which inherit the value from the path through
    // BB.  In this case, the PHI value must reference itself.
    for (auto *pred : predecessors(UnwindDest))
      if (pred != BB)
        PN->addIncoming(PN, pred);
    PN->moveBefore(InsertPt);
  }
}

std::vector<DominatorTree::UpdateType> Updates;

for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
  // The iterator must be updated here because we are removing this pred.
  BasicBlock *PredBB = *PI++;
  if (UnwindDest == nullptr) {
    if (DTU)
      DTU->applyUpdates(Updates);
    Updates.clear();
    removeUnwindEdge(PredBB, DTU);
    ++NumInvokes;
  } else {
    Instruction *TI = PredBB->getTerminator();
    TI->replaceUsesOfWith(BB, UnwindDest);
    Updates.push_back({DominatorTree::Insert, PredBB, UnwindDest});
    Updates.push_back({DominatorTree::Delete, PredBB, BB});
  }
}

if (DTU) {
  DTU->applyUpdates(Updates);
  DTU->deleteBB(BB);
} else
  // The cleanup pad is now unreachable.  Zap it.
  BB->eraseFromParent();

return true;
4519}

4521// Try to merge two cleanuppads together.
4522static bool mergeCleanupPad(CleanupReturnInst *RI) {
// Skip any cleanuprets which unwind to caller, there is nothing to merge
// with.
BasicBlock *UnwindDest = RI->getUnwindDest();
if (!UnwindDest)
  return false;

// This cleanupret isn't the only predecessor of this cleanuppad, it wouldn't
// be safe to merge without code duplication.
if (UnwindDest->getSinglePredecessor() != RI->getParent())
  return false;

// Verify that our cleanuppad's unwind destination is another cleanuppad.
auto *SuccessorCleanupPad = dyn_cast<CleanupPadInst>(&UnwindDest->front());
if (!SuccessorCleanupPad)
  return false;

CleanupPadInst *PredecessorCleanupPad = RI->getCleanupPad();
// Replace any uses of the successor cleanupad with the predecessor pad
// The only cleanuppad uses should be this cleanupret, it's cleanupret and
// funclet bundle operands.
SuccessorCleanupPad->replaceAllUsesWith(PredecessorCleanupPad);
// Remove the old cleanuppad.
SuccessorCleanupPad->eraseFromParent();
// Now, we simply replace the cleanupret with a branch to the unwind
// destination.
BranchInst::Create(UnwindDest, RI->getParent());
RI->eraseFromParent();

return true;
4552}

4554bool SimplifyCFGOpt::simplifyCleanupReturn(CleanupReturnInst *RI) {
// It is possible to transiantly have an undef cleanuppad operand because we
// have deleted some, but not all, dead blocks.
// Eventually, this block will be deleted.
if (isa<UndefValue>(RI->getOperand(0)))
  return false;

if (mergeCleanupPad(RI))
  return true;

if (removeEmptyCleanup(RI, DTU))
  return true;

return false;
4568}

4570bool SimplifyCFGOpt::simplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
BasicBlock *BB = RI->getParent();
if (!BB->getFirstNonPHIOrDbg()->isTerminator())
  return false;

// Find predecessors that end with branches.
SmallVector<BasicBlock *, 8> UncondBranchPreds;
SmallVector<BranchInst *, 8> CondBranchPreds;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
  BasicBlock *P = *PI;
  Instruction *PTI = P->getTerminator();
  if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
    if (BI->isUnconditional())
      UncondBranchPreds.push_back(P);
    else
      CondBranchPreds.push_back(BI);
  }
}

// If we found some, do the transformation!
if (!UncondBranchPreds.empty() && DupRet) {
  while (!UncondBranchPreds.empty()) {
    BasicBlock *Pred = UncondBranchPreds.pop_back_val();
    LLVM_DEBUG(dbgs() << "FOLDING: " << *BBdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOLDING: " << *BB <<
 "INTO UNCOND BRANCH PRED: " << *Pred; } } while (false
)
                      << "INTO UNCOND BRANCH PRED: " << *Pred)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "FOLDING: " << *BB <<
 "INTO UNCOND BRANCH PRED: " << *Pred; } } while (false
);
    (void)FoldReturnIntoUncondBranch(RI, BB, Pred, DTU);
  }

  // If we eliminated all predecessors of the block, delete the block now.
  if (pred_empty(BB)) {
    // We know there are no successors, so just nuke the block.
    if (LoopHeaders)
      LoopHeaders->erase(BB);
    if (DTU)
      DTU->deleteBB(BB);
    else
      BB->eraseFromParent();
  }

  return true;
}

// Check out all of the conditional branches going to this return
// instruction.  If any of them just select between returns, change the
// branch itself into a select/return pair.
while (!CondBranchPreds.empty()) {
  BranchInst *BI = CondBranchPreds.pop_back_val();

  // Check to see if the non-BB successor is also a return block.
  if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
      isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
      SimplifyCondBranchToTwoReturns(BI, Builder))
    return true;
}
return false;
4625}

4627bool SimplifyCFGOpt::simplifyUnreachable(UnreachableInst *UI) {
BasicBlock *BB = UI->getParent();

bool Changed = false;

// If there are any instructions immediately before the unreachable that can
// be removed, do so.
while (UI->getIterator() != BB->begin()) {
  BasicBlock::iterator BBI = UI->getIterator();
  --BBI;
  // Do not delete instructions that can have side effects which might cause
  // the unreachable to not be reachable; specifically, calls and volatile
  // operations may have this effect.
  if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI))
    break;

  if (BBI->mayHaveSideEffects()) {
    if (auto *SI = dyn_cast<StoreInst>(BBI)) {
      if (SI->isVolatile())
        break;
    } else if (auto *LI = dyn_cast<LoadInst>(BBI)) {
      if (LI->isVolatile())
        break;
    } else if (auto *RMWI = dyn_cast<AtomicRMWInst>(BBI)) {
      if (RMWI->isVolatile())
        break;
    } else if (auto *CXI = dyn_cast<AtomicCmpXchgInst>(BBI)) {
      if (CXI->isVolatile())
        break;
    } else if (isa<CatchPadInst>(BBI)) {
      // A catchpad may invoke exception object constructors and such, which
      // in some languages can be arbitrary code, so be conservative by
      // default.
      // For CoreCLR, it just involves a type test, so can be removed.
      if (classifyEHPersonality(BB->getParent()->getPersonalityFn()) !=
          EHPersonality::CoreCLR)
        break;
    } else if (!isa<FenceInst>(BBI) && !isa<VAArgInst>(BBI) &&
               !isa<LandingPadInst>(BBI)) {
      break;
    }
    // Note that deleting LandingPad's here is in fact okay, although it
    // involves a bit of subtle reasoning. If this inst is a LandingPad,
    // all the predecessors of this block will be the unwind edges of Invokes,
    // and we can therefore guarantee this block will be erased.
  }

  // Delete this instruction (any uses are guaranteed to be dead)
  if (!BBI->use_empty())
    BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
  BBI->eraseFromParent();
  Changed = true;
}

// If the unreachable instruction is the first in the block, take a gander
// at all of the predecessors of this instruction, and simplify them.
if (&BB->front() != UI)
  return Changed;

std::vector<DominatorTree::UpdateType> Updates;

SmallSetVector<BasicBlock *, 8> Preds(pred_begin(BB), pred_end(BB));
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
  auto *Predecessor = Preds[i];
  Instruction *TI = Predecessor->getTerminator();
  IRBuilder<> Builder(TI);
  if (auto *BI = dyn_cast<BranchInst>(TI)) {
    // We could either have a proper unconditional branch,
    // or a degenerate conditional branch with matching destinations.
    if (all_of(BI->successors(),
               [BB](auto *Successor) { return Successor == BB; })) {
      new UnreachableInst(TI->getContext(), TI);
      TI->eraseFromParent();
      Changed = true;
    } else {
      assert(BI->isConditional() && "Can't get here with an uncond branch.")((BI->isConditional() && "Can't get here with an uncond branch."
) ? static_cast<void> (0) : __assert_fail ("BI->isConditional() && \"Can't get here with an uncond branch.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4702, __PRETTY_FUNCTION__));
      Value* Cond = BI->getCondition();
      assert(BI->getSuccessor(0) != BI->getSuccessor(1) &&((BI->getSuccessor(0) != BI->getSuccessor(1) &&
 "The destinations are guaranteed to be different here.") ? static_cast
<void> (0) : __assert_fail ("BI->getSuccessor(0) != BI->getSuccessor(1) && \"The destinations are guaranteed to be different here.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4705, __PRETTY_FUNCTION__))
             "The destinations are guaranteed to be different here.")((BI->getSuccessor(0) != BI->getSuccessor(1) &&
 "The destinations are guaranteed to be different here.") ? static_cast
<void> (0) : __assert_fail ("BI->getSuccessor(0) != BI->getSuccessor(1) && \"The destinations are guaranteed to be different here.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4705, __PRETTY_FUNCTION__));
      if (BI->getSuccessor(0) == BB) {
        Builder.CreateAssumption(Builder.CreateNot(Cond));
        Builder.CreateBr(BI->getSuccessor(1));
      } else {
        assert(BI->getSuccessor(1) == BB && "Incorrect CFG")((BI->getSuccessor(1) == BB && "Incorrect CFG") ? static_cast
<void> (0) : __assert_fail ("BI->getSuccessor(1) == BB && \"Incorrect CFG\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4710, __PRETTY_FUNCTION__));
        Builder.CreateAssumption(Cond);
        Builder.CreateBr(BI->getSuccessor(0));
      }
      EraseTerminatorAndDCECond(BI);
      Changed = true;
    }
    Updates.push_back({DominatorTree::Delete, Predecessor, BB});
  } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
    SwitchInstProfUpdateWrapper SU(*SI);
    for (auto i = SU->case_begin(), e = SU->case_end(); i != e;) {
      if (i->getCaseSuccessor() != BB) {
        ++i;
        continue;
      }
      BB->removePredecessor(SU->getParent());
      i = SU.removeCase(i);
      e = SU->case_end();
      Changed = true;
    }
    // Note that the default destination can't be removed!
    if (SI->getDefaultDest() != BB)
      Updates.push_back({DominatorTree::Delete, Predecessor, BB});
  } else if (auto *II = dyn_cast<InvokeInst>(TI)) {
    if (II->getUnwindDest() == BB) {
      if (DTU)
        DTU->applyUpdates(Updates);
      Updates.clear();
      removeUnwindEdge(TI->getParent(), DTU);
      Changed = true;
    }
  } else if (auto *CSI = dyn_cast<CatchSwitchInst>(TI)) {
    if (CSI->getUnwindDest() == BB) {
      if (DTU)
        DTU->applyUpdates(Updates);
      Updates.clear();
      removeUnwindEdge(TI->getParent(), DTU);
      Changed = true;
      continue;
    }

    for (CatchSwitchInst::handler_iterator I = CSI->handler_begin(),
                                           E = CSI->handler_end();
         I != E; ++I) {
      if (*I == BB) {
        CSI->removeHandler(I);
        --I;
        --E;
        Changed = true;
      }
    }
    Updates.push_back({DominatorTree::Delete, Predecessor, BB});
    if (CSI->getNumHandlers() == 0) {
      if (CSI->hasUnwindDest()) {
        // Redirect all predecessors of the block containing CatchSwitchInst
        // to instead branch to the CatchSwitchInst's unwind destination.
        for (auto *PredecessorOfPredecessor : predecessors(Predecessor)) {
          Updates.push_back({DominatorTree::Insert, PredecessorOfPredecessor,
                             CSI->getUnwindDest()});
          Updates.push_back(
              {DominatorTree::Delete, PredecessorOfPredecessor, Predecessor});
        }
        Predecessor->replaceAllUsesWith(CSI->getUnwindDest());
      } else {
        // Rewrite all preds to unwind to caller (or from invoke to call).
        if (DTU)
          DTU->applyUpdates(Updates);
        Updates.clear();
        SmallVector<BasicBlock *, 8> EHPreds(predecessors(Predecessor));
        for (BasicBlock *EHPred : EHPreds)
          removeUnwindEdge(EHPred, DTU);
      }
      // The catchswitch is no longer reachable.
      new UnreachableInst(CSI->getContext(), CSI);
      CSI->eraseFromParent();
      Changed = true;
    }
  } else if (auto *CRI = dyn_cast<CleanupReturnInst>(TI)) {
    (void)CRI;
    assert(CRI->hasUnwindDest() && CRI->getUnwindDest() == BB &&((CRI->hasUnwindDest() && CRI->getUnwindDest() ==
 BB && "Expected to always have an unwind to BB.") ? static_cast
<void> (0) : __assert_fail ("CRI->hasUnwindDest() && CRI->getUnwindDest() == BB && \"Expected to always have an unwind to BB.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4790, __PRETTY_FUNCTION__))
           "Expected to always have an unwind to BB.")((CRI->hasUnwindDest() && CRI->getUnwindDest() ==
 BB && "Expected to always have an unwind to BB.") ? static_cast
<void> (0) : __assert_fail ("CRI->hasUnwindDest() && CRI->getUnwindDest() == BB && \"Expected to always have an unwind to BB.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4790, __PRETTY_FUNCTION__));
    Updates.push_back({DominatorTree::Delete, Predecessor, BB});
    new UnreachableInst(TI->getContext(), TI);
    TI->eraseFromParent();
    Changed = true;
  }
}

if (DTU)
  DTU->applyUpdates(Updates);

// If this block is now dead, remove it.
if (pred_empty(BB) && BB != &BB->getParent()->getEntryBlock()) {
  // We know there are no successors, so just nuke the block.
  if (LoopHeaders)
    LoopHeaders->erase(BB);
  if (DTU)
    DTU->deleteBB(BB);
  else
    BB->eraseFromParent();
  return true;
}

return Changed;
4814}

4816static bool CasesAreContiguous(SmallVectorImpl<ConstantInt *> &Cases) {
assert(Cases.size() >= 1)((Cases.size() >= 1) ? static_cast<void> (0) : __assert_fail
 ("Cases.size() >= 1", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4817, __PRETTY_FUNCTION__));

array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate);
for (size_t I = 1, E = Cases.size(); I != E; ++I) {
  if (Cases[I - 1]->getValue() != Cases[I]->getValue() + 1)
    return false;
}
return true;
4825}

4827static void createUnreachableSwitchDefault(SwitchInst *Switch,
                                         DomTreeUpdater *DTU) {
LLVM_DEBUG(dbgs() << "SimplifyCFG: switch default is dead.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SimplifyCFG: switch default is dead.\n"
; } } while (false);
auto *BB = Switch->getParent();
BasicBlock *NewDefaultBlock = SplitBlockPredecessors(
    Switch->getDefaultDest(), Switch->getParent(), "", DTU);
auto *OrigDefaultBlock = Switch->getDefaultDest();
Switch->setDefaultDest(&*NewDefaultBlock);
if (DTU)
  DTU->applyUpdates({{DominatorTree::Insert, BB, &*NewDefaultBlock},
                     {DominatorTree::Delete, BB, OrigDefaultBlock}});
SplitBlock(&*NewDefaultBlock, &NewDefaultBlock->front(), DTU);
SmallVector<DominatorTree::UpdateType, 2> Updates;
for (auto *Successor : successors(NewDefaultBlock))
  Updates.push_back({DominatorTree::Delete, NewDefaultBlock, Successor});
auto *NewTerminator = NewDefaultBlock->getTerminator();
new UnreachableInst(Switch->getContext(), NewTerminator);
EraseTerminatorAndDCECond(NewTerminator);
if (DTU)
  DTU->applyUpdates(Updates);
4847}

4849/// Turn a switch with two reachable destinations into an integer range
4850/// comparison and branch.
4851bool SimplifyCFGOpt::TurnSwitchRangeIntoICmp(SwitchInst *SI,
                                           IRBuilder<> &Builder) {
assert(SI->getNumCases() > 1 && "Degenerate switch?")((SI->getNumCases() > 1 && "Degenerate switch?"
) ? static_cast<void> (0) : __assert_fail ("SI->getNumCases() > 1 && \"Degenerate switch?\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4853, __PRETTY_FUNCTION__));

bool HasDefault =
    !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());

auto *BB = SI->getParent();

// Partition the cases into two sets with different destinations.
BasicBlock *DestA = HasDefault ? SI->getDefaultDest() : nullptr;
BasicBlock *DestB = nullptr;
SmallVector<ConstantInt *, 16> CasesA;
SmallVector<ConstantInt *, 16> CasesB;

for (auto Case : SI->cases()) {
  BasicBlock *Dest = Case.getCaseSuccessor();
  if (!DestA)
    DestA = Dest;
  if (Dest == DestA) {
    CasesA.push_back(Case.getCaseValue());
    continue;
  }
  if (!DestB)
    DestB = Dest;
  if (Dest == DestB) {
    CasesB.push_back(Case.getCaseValue());
    continue;
  }
  return false; // More than two destinations.
}

assert(DestA && DestB &&((DestA && DestB && "Single-destination switch should have been folded."
) ? static_cast<void> (0) : __assert_fail ("DestA && DestB && \"Single-destination switch should have been folded.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4884, __PRETTY_FUNCTION__))
       "Single-destination switch should have been folded.")((DestA && DestB && "Single-destination switch should have been folded."
) ? static_cast<void> (0) : __assert_fail ("DestA && DestB && \"Single-destination switch should have been folded.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4884, __PRETTY_FUNCTION__));
assert(DestA != DestB)((DestA != DestB) ? static_cast<void> (0) : __assert_fail
 ("DestA != DestB", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4885, __PRETTY_FUNCTION__));
assert(DestB != SI->getDefaultDest())((DestB != SI->getDefaultDest()) ? static_cast<void>
 (0) : __assert_fail ("DestB != SI->getDefaultDest()", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4886, __PRETTY_FUNCTION__));
assert(!CasesB.empty() && "There must be non-default cases.")((!CasesB.empty() && "There must be non-default cases."
) ? static_cast<void> (0) : __assert_fail ("!CasesB.empty() && \"There must be non-default cases.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4887, __PRETTY_FUNCTION__));
assert(!CasesA.empty() || HasDefault)((!CasesA.empty() || HasDefault) ? static_cast<void> (0
) : __assert_fail ("!CasesA.empty() || HasDefault", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 4888, __PRETTY_FUNCTION__));

// Figure out if one of the sets of cases form a contiguous range.
SmallVectorImpl<ConstantInt *> *ContiguousCases = nullptr;
BasicBlock *ContiguousDest = nullptr;
BasicBlock *OtherDest = nullptr;
if (!CasesA.empty() && CasesAreContiguous(CasesA)) {
  ContiguousCases = &CasesA;
  ContiguousDest = DestA;
  OtherDest = DestB;
} else if (CasesAreContiguous(CasesB)) {
  ContiguousCases = &CasesB;
  ContiguousDest = DestB;
  OtherDest = DestA;
} else
  return false;

// Start building the compare and branch.

Constant *Offset = ConstantExpr::getNeg(ContiguousCases->back());
Constant *NumCases =
    ConstantInt::get(Offset->getType(), ContiguousCases->size());

Value *Sub = SI->getCondition();
if (!Offset->isNullValue())
  Sub = Builder.CreateAdd(Sub, Offset, Sub->getName() + ".off");

Value *Cmp;
// If NumCases overflowed, then all possible values jump to the successor.
if (NumCases->isNullValue() && !ContiguousCases->empty())
  Cmp = ConstantInt::getTrue(SI->getContext());
else
  Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
BranchInst *NewBI = Builder.CreateCondBr(Cmp, ContiguousDest, OtherDest);

// Update weight for the newly-created conditional branch.
if (HasBranchWeights(SI)) {
  SmallVector<uint64_t, 8> Weights;
  GetBranchWeights(SI, Weights);
  if (Weights.size() == 1 + SI->getNumCases()) {
    uint64_t TrueWeight = 0;
    uint64_t FalseWeight = 0;
    for (size_t I = 0, E = Weights.size(); I != E; ++I) {
      if (SI->getSuccessor(I) == ContiguousDest)
        TrueWeight += Weights[I];
      else
        FalseWeight += Weights[I];
    }
    while (TrueWeight > UINT32_MAX(4294967295U) || FalseWeight > UINT32_MAX(4294967295U)) {
      TrueWeight /= 2;
      FalseWeight /= 2;
    }
    setBranchWeights(NewBI, TrueWeight, FalseWeight);
  }
}

// Prune obsolete incoming values off the successors' PHI nodes.
for (auto BBI = ContiguousDest->begin(); isa<PHINode>(BBI); ++BBI) {
  unsigned PreviousEdges = ContiguousCases->size();
  if (ContiguousDest == SI->getDefaultDest())
    ++PreviousEdges;
  for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I)
    cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
}
for (auto BBI = OtherDest->begin(); isa<PHINode>(BBI); ++BBI) {
  unsigned PreviousEdges = SI->getNumCases() - ContiguousCases->size();
  if (OtherDest == SI->getDefaultDest())
    ++PreviousEdges;
  for (unsigned I = 0, E = PreviousEdges - 1; I != E; ++I)
    cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
}

// Clean up the default block - it may have phis or other instructions before
// the unreachable terminator.
if (!HasDefault)
  createUnreachableSwitchDefault(SI, DTU);

auto *UnreachableDefault = SI->getDefaultDest();

// Drop the switch.
SI->eraseFromParent();

if (!HasDefault && DTU)
  DTU->applyUpdates({{DominatorTree::Delete, BB, UnreachableDefault}});

return true;
4974}

4976/// Compute masked bits for the condition of a switch
4977/// and use it to remove dead cases.
4978static bool eliminateDeadSwitchCases(SwitchInst *SI, DomTreeUpdater *DTU,
                                   AssumptionCache *AC,
                                   const DataLayout &DL) {
Value *Cond = SI->getCondition();
unsigned Bits = Cond->getType()->getIntegerBitWidth();
KnownBits Known = computeKnownBits(Cond, DL, 0, AC, SI);

// We can also eliminate cases by determining that their values are outside of
// the limited range of the condition based on how many significant (non-sign)
// bits are in the condition value.
unsigned ExtraSignBits = ComputeNumSignBits(Cond, DL, 0, AC, SI) - 1;
unsigned MaxSignificantBitsInCond = Bits - ExtraSignBits;

// Gather dead cases.
SmallVector<ConstantInt *, 8> DeadCases;
SmallMapVector<BasicBlock *, int, 8> NumPerSuccessorCases;
for (auto &Case : SI->cases()) {
  auto *Successor = Case.getCaseSuccessor();
  ++NumPerSuccessorCases[Successor];
  const APInt &CaseVal = Case.getCaseValue()->getValue();
  if (Known.Zero.intersects(CaseVal) || !Known.One.isSubsetOf(CaseVal) ||
      (CaseVal.getMinSignedBits() > MaxSignificantBitsInCond)) {
    DeadCases.push_back(Case.getCaseValue());
    --NumPerSuccessorCases[Successor];
    LLVM_DEBUG(dbgs() << "SimplifyCFG: switch case " << CaseValdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SimplifyCFG: switch case "
 << CaseVal << " is dead.\n"; } } while (false)
                      << " is dead.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("simplifycfg")) { dbgs() << "SimplifyCFG: switch case "
 << CaseVal << " is dead.\n"; } } while (false);
  }
}

// If we can prove that the cases must cover all possible values, the
// default destination becomes dead and we can remove it.  If we know some
// of the bits in the value, we can use that to more precisely compute the
// number of possible unique case values.
bool HasDefault =
    !isa<UnreachableInst>(SI->getDefaultDest()->getFirstNonPHIOrDbg());
const unsigned NumUnknownBits =
    Bits - (Known.Zero | Known.One).countPopulation();
assert(NumUnknownBits <= Bits)((NumUnknownBits <= Bits) ? static_cast<void> (0) : __assert_fail
 ("NumUnknownBits <= Bits", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5015, __PRETTY_FUNCTION__));
if (HasDefault && DeadCases.empty() &&
    NumUnknownBits < 64 /* avoid overflow */ &&
    SI->getNumCases() == (1ULL << NumUnknownBits)) {
  createUnreachableSwitchDefault(SI, DTU);
  return true;
}

if (DeadCases.empty())
  return false;

SwitchInstProfUpdateWrapper SIW(*SI);
for (ConstantInt *DeadCase : DeadCases) {
  SwitchInst::CaseIt CaseI = SI->findCaseValue(DeadCase);
  assert(CaseI != SI->case_default() &&((CaseI != SI->case_default() && "Case was not found. Probably mistake in DeadCases forming."
) ? static_cast<void> (0) : __assert_fail ("CaseI != SI->case_default() && \"Case was not found. Probably mistake in DeadCases forming.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5030, __PRETTY_FUNCTION__))
         "Case was not found. Probably mistake in DeadCases forming.")((CaseI != SI->case_default() && "Case was not found. Probably mistake in DeadCases forming."
) ? static_cast<void> (0) : __assert_fail ("CaseI != SI->case_default() && \"Case was not found. Probably mistake in DeadCases forming.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5030, __PRETTY_FUNCTION__));
  // Prune unused values from PHI nodes.
  CaseI->getCaseSuccessor()->removePredecessor(SI->getParent());
  SIW.removeCase(CaseI);
}

std::vector<DominatorTree::UpdateType> Updates;
for (const std::pair<BasicBlock *, int> &I : NumPerSuccessorCases)
  if (I.second == 0)
    Updates.push_back({DominatorTree::Delete, SI->getParent(), I.first});
if (DTU)
  DTU->applyUpdates(Updates);

return true;
5044}

5046/// If BB would be eligible for simplification by
5047/// TryToSimplifyUncondBranchFromEmptyBlock (i.e. it is empty and terminated
5048/// by an unconditional branch), look at the phi node for BB in the successor
5049/// block and see if the incoming value is equal to CaseValue. If so, return
5050/// the phi node, and set PhiIndex to BB's index in the phi node.
5051static PHINode *FindPHIForConditionForwarding(ConstantInt *CaseValue,
                                            BasicBlock *BB, int *PhiIndex) {
if (BB->getFirstNonPHIOrDbg() != BB->getTerminator())
  return nullptr; // BB must be empty to be a candidate for simplification.
if (!BB->getSinglePredecessor())
  return nullptr; // BB must be dominated by the switch.

BranchInst *Branch = dyn_cast<BranchInst>(BB->getTerminator());
if (!Branch || !Branch->isUnconditional())
  return nullptr; // Terminator must be unconditional branch.

BasicBlock *Succ = Branch->getSuccessor(0);

for (PHINode &PHI : Succ->phis()) {
  int Idx = PHI.getBasicBlockIndex(BB);
  assert(Idx >= 0 && "PHI has no entry for predecessor?")((Idx >= 0 && "PHI has no entry for predecessor?")
 ? static_cast<void> (0) : __assert_fail ("Idx >= 0 && \"PHI has no entry for predecessor?\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5066, __PRETTY_FUNCTION__));

  Value *InValue = PHI.getIncomingValue(Idx);
  if (InValue != CaseValue)
    continue;

  *PhiIndex = Idx;
  return &PHI;
}

return nullptr;
5077}

5079/// Try to forward the condition of a switch instruction to a phi node
5080/// dominated by the switch, if that would mean that some of the destination
5081/// blocks of the switch can be folded away. Return true if a change is made.
5082static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
using ForwardingNodesMap = DenseMap<PHINode *, SmallVector<int, 4>>;

ForwardingNodesMap ForwardingNodes;
BasicBlock *SwitchBlock = SI->getParent();
bool Changed = false;
for (auto &Case : SI->cases()) {
  ConstantInt *CaseValue = Case.getCaseValue();
  BasicBlock *CaseDest = Case.getCaseSuccessor();

  // Replace phi operands in successor blocks that are using the constant case
  // value rather than the switch condition variable:
  //   switchbb:
  //   switch i32 %x, label %default [
  //     i32 17, label %succ
  //   ...
  //   succ:
  //     %r = phi i32 ... [ 17, %switchbb ] ...
  // -->
  //     %r = phi i32 ... [ %x, %switchbb ] ...

  for (PHINode &Phi : CaseDest->phis()) {
    // This only works if there is exactly 1 incoming edge from the switch to
    // a phi. If there is >1, that means multiple cases of the switch map to 1
    // value in the phi, and that phi value is not the switch condition. Thus,
    // this transform would not make sense (the phi would be invalid because
    // a phi can't have different incoming values from the same block).
    int SwitchBBIdx = Phi.getBasicBlockIndex(SwitchBlock);
    if (Phi.getIncomingValue(SwitchBBIdx) == CaseValue &&
        count(Phi.blocks(), SwitchBlock) == 1) {
      Phi.setIncomingValue(SwitchBBIdx, SI->getCondition());
      Changed = true;
    }
  }

  // Collect phi nodes that are indirectly using this switch's case constants.
  int PhiIdx;
  if (auto *Phi = FindPHIForConditionForwarding(CaseValue, CaseDest, &PhiIdx))
    ForwardingNodes[Phi].push_back(PhiIdx);
}

for (auto &ForwardingNode : ForwardingNodes) {
  PHINode *Phi = ForwardingNode.first;
  SmallVectorImpl<int> &Indexes = ForwardingNode.second;
  if (Indexes.size() < 2)
    continue;

  for (int Index : Indexes)
    Phi->setIncomingValue(Index, SI->getCondition());
  Changed = true;
}

return Changed;
5135}

5137/// Return true if the backend will be able to handle
5138/// initializing an array of constants like C.
5139static bool ValidLookupTableConstant(Constant *C, const TargetTransformInfo &TTI) {
if (C->isThreadDependent())
  return false;
if (C->isDLLImportDependent())
  return false;

if (!isa<ConstantFP>(C) && !isa<ConstantInt>(C) &&
    !isa<ConstantPointerNull>(C) && !isa<GlobalValue>(C) &&
    !isa<UndefValue>(C) && !isa<ConstantExpr>(C))
  return false;

if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
  if (!CE->isGEPWithNoNotionalOverIndexing())
    return false;
  if (!ValidLookupTableConstant(CE->getOperand(0), TTI))
    return false;
}

if (!TTI.shouldBuildLookupTablesForConstant(C))
  return false;

return true;
5161}

5163/// If V is a Constant, return it. Otherwise, try to look up
5164/// its constant value in ConstantPool, returning 0 if it's not there.
5165static Constant *
5166LookupConstant(Value *V,
             const SmallDenseMap<Value *, Constant *> &ConstantPool) {
if (Constant *C = dyn_cast<Constant>(V))
  return C;
return ConstantPool.lookup(V);
5171}

5173/// Try to fold instruction I into a constant. This works for
5174/// simple instructions such as binary operations where both operands are
5175/// constant or can be replaced by constants from the ConstantPool. Returns the
5176/// resulting constant on success, 0 otherwise.
5177static Constant *
5178ConstantFold(Instruction *I, const DataLayout &DL,
           const SmallDenseMap<Value *, Constant *> &ConstantPool) {
if (SelectInst *Select = dyn_cast<SelectInst>(I)) {
  Constant *A = LookupConstant(Select->getCondition(), ConstantPool);
  if (!A)
    return nullptr;
  if (A->isAllOnesValue())
    return LookupConstant(Select->getTrueValue(), ConstantPool);
  if (A->isNullValue())
    return LookupConstant(Select->getFalseValue(), ConstantPool);
  return nullptr;
}

SmallVector<Constant *, 4> COps;
for (unsigned N = 0, E = I->getNumOperands(); N != E; ++N) {
  if (Constant *A = LookupConstant(I->getOperand(N), ConstantPool))
    COps.push_back(A);
  else
    return nullptr;
}

if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
  return ConstantFoldCompareInstOperands(Cmp->getPredicate(), COps[0],
                                         COps[1], DL);
}

return ConstantFoldInstOperands(I, COps, DL);
5205}

5207/// Try to determine the resulting constant values in phi nodes
5208/// at the common destination basic block, *CommonDest, for one of the case
5209/// destionations CaseDest corresponding to value CaseVal (0 for the default
5210/// case), of a switch instruction SI.
5211static bool
5212GetCaseResults(SwitchInst *SI, ConstantInt *CaseVal, BasicBlock *CaseDest,
             BasicBlock **CommonDest,
             SmallVectorImpl<std::pair<PHINode *, Constant *>> &Res,
             const DataLayout &DL, const TargetTransformInfo &TTI) {
// The block from which we enter the common destination.
BasicBlock *Pred = SI->getParent();

// If CaseDest is empty except for some side-effect free instructions through
// which we can constant-propagate the CaseVal, continue to its successor.
SmallDenseMap<Value *, Constant *> ConstantPool;
ConstantPool.insert(std::make_pair(SI->getCondition(), CaseVal));
for (Instruction &I :CaseDest->instructionsWithoutDebug()) {
  if (I.isTerminator()) {
    // If the terminator is a simple branch, continue to the next block.
    if (I.getNumSuccessors() != 1 || I.isExceptionalTerminator())
      return false;
    Pred = CaseDest;
    CaseDest = I.getSuccessor(0);
  } else if (Constant *C = ConstantFold(&I, DL, ConstantPool)) {
    // Instruction is side-effect free and constant.

    // If the instruction has uses outside this block or a phi node slot for
    // the block, it is not safe to bypass the instruction since it would then
    // no longer dominate all its uses.
    for (auto &Use : I.uses()) {
      User *User = Use.getUser();
      if (Instruction *I = dyn_cast<Instruction>(User))
        if (I->getParent() == CaseDest)
          continue;
      if (PHINode *Phi = dyn_cast<PHINode>(User))
        if (Phi->getIncomingBlock(Use) == CaseDest)
          continue;
      return false;
    }

    ConstantPool.insert(std::make_pair(&I, C));
  } else {
    break;
  }
}

// If we did not have a CommonDest before, use the current one.
if (!*CommonDest)
  *CommonDest = CaseDest;
// If the destination isn't the common one, abort.
if (CaseDest != *CommonDest)
  return false;

// Get the values for this case from phi nodes in the destination block.
for (PHINode &PHI : (*CommonDest)->phis()) {
  int Idx = PHI.getBasicBlockIndex(Pred);
  if (Idx == -1)
    continue;

  Constant *ConstVal =
      LookupConstant(PHI.getIncomingValue(Idx), ConstantPool);
  if (!ConstVal)
    return false;

  // Be conservative about which kinds of constants we support.
  if (!ValidLookupTableConstant(ConstVal, TTI))
    return false;

  Res.push_back(std::make_pair(&PHI, ConstVal));
}

return Res.size() > 0;
5279}

5281// Helper function used to add CaseVal to the list of cases that generate
5282// Result. Returns the updated number of cases that generate this result.
5283static uintptr_t MapCaseToResult(ConstantInt *CaseVal,
                               SwitchCaseResultVectorTy &UniqueResults,
                               Constant *Result) {
for (auto &I : UniqueResults) {
  if (I.first == Result) {
    I.second.push_back(CaseVal);
    return I.second.size();
  }
}
UniqueResults.push_back(
    std::make_pair(Result, SmallVector<ConstantInt *, 4>(1, CaseVal)));
return 1;
5295}

5297// Helper function that initializes a map containing
5298// results for the PHI node of the common destination block for a switch
5299// instruction. Returns false if multiple PHI nodes have been found or if
5300// there is not a common destination block for the switch.
5301static bool
5302InitializeUniqueCases(SwitchInst *SI, PHINode *&PHI, BasicBlock *&CommonDest,
                    SwitchCaseResultVectorTy &UniqueResults,
                    Constant *&DefaultResult, const DataLayout &DL,
                    const TargetTransformInfo &TTI,
                    uintptr_t MaxUniqueResults, uintptr_t MaxCasesPerResult) {
for (auto &I : SI->cases()) {
  ConstantInt *CaseVal = I.getCaseValue();

  // Resulting value at phi nodes for this case value.
  SwitchCaseResultsTy Results;
  if (!GetCaseResults(SI, CaseVal, I.getCaseSuccessor(), &CommonDest, Results,
                      DL, TTI))
    return false;

  // Only one value per case is permitted.
  if (Results.size() > 1)
    return false;

  // Add the case->result mapping to UniqueResults.
  const uintptr_t NumCasesForResult =
      MapCaseToResult(CaseVal, UniqueResults, Results.begin()->second);

  // Early out if there are too many cases for this result.
  if (NumCasesForResult > MaxCasesPerResult)
    return false;

  // Early out if there are too many unique results.
  if (UniqueResults.size() > MaxUniqueResults)
    return false;

  // Check the PHI consistency.
  if (!PHI)
    PHI = Results[0].first;
  else if (PHI != Results[0].first)
    return false;
}
// Find the default result value.
SmallVector<std::pair<PHINode *, Constant *>, 1> DefaultResults;
BasicBlock *DefaultDest = SI->getDefaultDest();
GetCaseResults(SI, nullptr, SI->getDefaultDest(), &CommonDest, DefaultResults,
               DL, TTI);
// If the default value is not found abort unless the default destination
// is unreachable.
DefaultResult =
    DefaultResults.size() == 1 ? DefaultResults.begin()->second : nullptr;
if ((!DefaultResult &&
     !isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg())))
  return false;

return true;
5352}

5354// Helper function that checks if it is possible to transform a switch with only
5355// two cases (or two cases + default) that produces a result into a select.
5356// Example:
5357// switch (a) {
5358//   case 10:                %0 = icmp eq i32 %a, 10
5359//     return 10;            %1 = select i1 %0, i32 10, i32 4
5360//   case 20:        ---->   %2 = icmp eq i32 %a, 20
5361//     return 2;             %3 = select i1 %2, i32 2, i32 %1
5362//   default:
5363//     return 4;
5364// }
5365static Value *ConvertTwoCaseSwitch(const SwitchCaseResultVectorTy &ResultVector,
                                 Constant *DefaultResult, Value *Condition,
                                 IRBuilder<> &Builder) {
assert(ResultVector.size() == 2 &&((ResultVector.size() == 2 && "We should have exactly two unique results at this point"
) ? static_cast<void> (0) : __assert_fail ("ResultVector.size() == 2 && \"We should have exactly two unique results at this point\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5369, __PRETTY_FUNCTION__))
       "We should have exactly two unique results at this point")((ResultVector.size() == 2 && "We should have exactly two unique results at this point"
) ? static_cast<void> (0) : __assert_fail ("ResultVector.size() == 2 && \"We should have exactly two unique results at this point\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5369, __PRETTY_FUNCTION__));
// If we are selecting between only two cases transform into a simple
// select or a two-way select if default is possible.
if (ResultVector[0].second.size() == 1 &&
    ResultVector[1].second.size() == 1) {
  ConstantInt *const FirstCase = ResultVector[0].second[0];
  ConstantInt *const SecondCase = ResultVector[1].second[0];

  bool DefaultCanTrigger = DefaultResult;
  Value *SelectValue = ResultVector[1].first;
  if (DefaultCanTrigger) {
    Value *const ValueCompare =
        Builder.CreateICmpEQ(Condition, SecondCase, "switch.selectcmp");
    SelectValue = Builder.CreateSelect(ValueCompare, ResultVector[1].first,
                                       DefaultResult, "switch.select");
  }
  Value *const ValueCompare =
      Builder.CreateICmpEQ(Condition, FirstCase, "switch.selectcmp");
  return Builder.CreateSelect(ValueCompare, ResultVector[0].first,
                              SelectValue, "switch.select");
}

return nullptr;
5392}

5394// Helper function to cleanup a switch instruction that has been converted into
5395// a select, fixing up PHI nodes and basic blocks.
5396static void RemoveSwitchAfterSelectConversion(SwitchInst *SI, PHINode *PHI,
                                            Value *SelectValue,
                                            IRBuilder<> &Builder,
                                            DomTreeUpdater *DTU) {
std::vector<DominatorTree::UpdateType> Updates;

BasicBlock *SelectBB = SI->getParent();
BasicBlock *DestBB = PHI->getParent();

if (!is_contained(predecessors(DestBB), SelectBB))
  Updates.push_back({DominatorTree::Insert, SelectBB, DestBB});
Builder.CreateBr(DestBB);

// Remove the switch.

while (PHI->getBasicBlockIndex(SelectBB) >= 0)
  PHI->removeIncomingValue(SelectBB);
PHI->addIncoming(SelectValue, SelectBB);

for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
  BasicBlock *Succ = SI->getSuccessor(i);

  if (Succ == DestBB)
    continue;
  Succ->removePredecessor(SelectBB);
  Updates.push_back({DominatorTree::Delete, SelectBB, Succ});
}
SI->eraseFromParent();
if (DTU)
  DTU->applyUpdates(Updates);
5426}

5428/// If the switch is only used to initialize one or more
5429/// phi nodes in a common successor block with only two different
5430/// constant values, replace the switch with select.
5431static bool switchToSelect(SwitchInst *SI, IRBuilder<> &Builder,
                         DomTreeUpdater *DTU, const DataLayout &DL,
                         const TargetTransformInfo &TTI) {
Value *const Cond = SI->getCondition();
PHINode *PHI = nullptr;
BasicBlock *CommonDest = nullptr;
Constant *DefaultResult;
SwitchCaseResultVectorTy UniqueResults;
// Collect all the cases that will deliver the same value from the switch.
if (!InitializeUniqueCases(SI, PHI, CommonDest, UniqueResults, DefaultResult,
                           DL, TTI, 2, 1))
  return false;
// Selects choose between maximum two values.
if (UniqueResults.size() != 2)
  return false;
assert(PHI != nullptr && "PHI for value select not found")((PHI != nullptr && "PHI for value select not found")
 ? static_cast<void> (0) : __assert_fail ("PHI != nullptr && \"PHI for value select not found\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5446, __PRETTY_FUNCTION__));

Builder.SetInsertPoint(SI);
Value *SelectValue =
    ConvertTwoCaseSwitch(UniqueResults, DefaultResult, Cond, Builder);
if (SelectValue) {
  RemoveSwitchAfterSelectConversion(SI, PHI, SelectValue, Builder, DTU);
  return true;
}
// The switch couldn't be converted into a select.
return false;
5457}

5459namespace {

5461/// This class represents a lookup table that can be used to replace a switch.
5462class SwitchLookupTable {
5463public:
/// Create a lookup table to use as a switch replacement with the contents
/// of Values, using DefaultValue to fill any holes in the table.
SwitchLookupTable(
    Module &M, uint64_t TableSize, ConstantInt *Offset,
    const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values,
    Constant *DefaultValue, const DataLayout &DL, const StringRef &FuncName);

/// Build instructions with Builder to retrieve the value at
/// the position given by Index in the lookup table.
Value *BuildLookup(Value *Index, IRBuilder<> &Builder);

/// Return true if a table with TableSize elements of
/// type ElementType would fit in a target-legal register.
static bool WouldFitInRegister(const DataLayout &DL, uint64_t TableSize,
                               Type *ElementType);

5480private:
// Depending on the contents of the table, it can be represented in
// different ways.
enum {
  // For tables where each element contains the same value, we just have to
  // store that single value and return it for each lookup.
  SingleValueKind,

  // For tables where there is a linear relationship between table index
  // and values. We calculate the result with a simple multiplication
  // and addition instead of a table lookup.
  LinearMapKind,

  // For small tables with integer elements, we can pack them into a bitmap
  // that fits into a target-legal register. Values are retrieved by
  // shift and mask operations.
  BitMapKind,

  // The table is stored as an array of values. Values are retrieved by load
  // instructions from the table.
  ArrayKind
} Kind;

// For SingleValueKind, this is the single value.
Constant *SingleValue = nullptr;

// For BitMapKind, this is the bitmap.
ConstantInt *BitMap = nullptr;
IntegerType *BitMapElementTy = nullptr;

// For LinearMapKind, these are the constants used to derive the value.
ConstantInt *LinearOffset = nullptr;
ConstantInt *LinearMultiplier = nullptr;

// For ArrayKind, this is the array.
GlobalVariable *Array = nullptr;
5516};

5518} // end anonymous namespace

5520SwitchLookupTable::SwitchLookupTable(
  Module &M, uint64_t TableSize, ConstantInt *Offset,
  const SmallVectorImpl<std::pair<ConstantInt *, Constant *>> &Values,
  Constant *DefaultValue, const DataLayout &DL, const StringRef &FuncName) {
assert(Values.size() && "Can't build lookup table without values!")((Values.size() && "Can't build lookup table without values!"
) ? static_cast<void> (0) : __assert_fail ("Values.size() && \"Can't build lookup table without values!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5524, __PRETTY_FUNCTION__));
assert(TableSize >= Values.size() && "Can't fit values in table!")((TableSize >= Values.size() && "Can't fit values in table!"
) ? static_cast<void> (0) : __assert_fail ("TableSize >= Values.size() && \"Can't fit values in table!\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5525, __PRETTY_FUNCTION__));

// If all values in the table are equal, this is that value.
SingleValue = Values.begin()->second;

Type *ValueType = Values.begin()->second->getType();

// Build up the table contents.
SmallVector<Constant *, 64> TableContents(TableSize);
for (size_t I = 0, E = Values.size(); I != E; ++I) {
  ConstantInt *CaseVal = Values[I].first;
  Constant *CaseRes = Values[I].second;
  assert(CaseRes->getType() == ValueType)((CaseRes->getType() == ValueType) ? static_cast<void>
 (0) : __assert_fail ("CaseRes->getType() == ValueType", "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5537, __PRETTY_FUNCTION__));

  uint64_t Idx = (CaseVal->getValue() - Offset->getValue()).getLimitedValue();
  TableContents[Idx] = CaseRes;

  if (CaseRes != SingleValue)
    SingleValue = nullptr;
}

// Fill in any holes in the table with the default result.
if (Values.size() < TableSize) {
  assert(DefaultValue &&((DefaultValue && "Need a default value to fill the lookup table holes."
) ? static_cast<void> (0) : __assert_fail ("DefaultValue && \"Need a default value to fill the lookup table holes.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5549, __PRETTY_FUNCTION__))
         "Need a default value to fill the lookup table holes.")((DefaultValue && "Need a default value to fill the lookup table holes."
) ? static_cast<void> (0) : __assert_fail ("DefaultValue && \"Need a default value to fill the lookup table holes.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5549, __PRETTY_FUNCTION__));
  assert(DefaultValue->getType() == ValueType)((DefaultValue->getType() == ValueType) ? static_cast<void
> (0) : __assert_fail ("DefaultValue->getType() == ValueType"
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5550, __PRETTY_FUNCTION__));
  for (uint64_t I = 0; I < TableSize; ++I) {
    if (!TableContents[I])
      TableContents[I] = DefaultValue;
  }

  if (DefaultValue != SingleValue)
    SingleValue = nullptr;
}

// If each element in the table contains the same value, we only need to store
// that single value.
if (SingleValue) {
  Kind = SingleValueKind;
  return;
}

// Check if we can derive the value with a linear transformation from the
// table index.
if (isa<IntegerType>(ValueType)) {
  bool LinearMappingPossible = true;
  APInt PrevVal;
  APInt DistToPrev;
  assert(TableSize >= 2 && "Should be a SingleValue table.")((TableSize >= 2 && "Should be a SingleValue table."
) ? static_cast<void> (0) : __assert_fail ("TableSize >= 2 && \"Should be a SingleValue table.\""
, "/build/llvm-toolchain-snapshot-12~++20210121111113+bee486851c1a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp"
, 5573, __PRETTY_FUNCTION__));
  // Check if there is the same distance between two consecutive values.
  for (uint64_t I = 0; I < TableSize; ++I) {
    ConstantInt *ConstVal = dyn_cast<ConstantInt>(TableContents[I]);
    if (!ConstVal) {
      // This is an undef. We could deal with it, but undefs in lookup tables
      // are very seldom. It's probably not worth the additional complexity.
      LinearMappingPossible = false;
      break;
    }
    const APInt &Val = ConstVal->getValue();
    if (I != 0) {
      APInt Dist = Val - PrevVal;
      if (I == 1) {
        DistToPrev = Dist;
      } else if (Dist != DistToPrev) {
        LinearMappingPossible = false;
        break;
      }
    }
    PrevVal = Val;
  }
  if (LinearMappingPossible) {
    LinearOffset = cast<ConstantInt>(TableContents[0]);
    LinearMultiplier = ConstantInt::get(M.getContext(), DistToPrev);
    Kind = LinearMapKind;
    ++NumLinearMaps;
    return;
  }
}

// If the type is integer and the table fits in a register, build a bitmap.
if (WouldFitInRegister(DL, TableSize, ValueType)) {
  IntegerType *IT = cast<IntegerType>(ValueType);
  APInt TableInt(TableSize * IT->getBitWidth(), 0);
  for (uint64_t I = TableSize; I > 0; --I) {
    TableInt <<= IT->getBitWidth();
    // Insert values into the bitmap. Undef values are set to zero.
    if (!isa<UndefValue>(TableContents[I - 1])) {
      ConstantInt *Val = cast<ConstantInt>(TableContents[I - 1]);
      TableInt |= Val->getValue().zext(TableInt.getBitWidth());
    }
  }
  BitMap = ConstantInt::get(M.getContext(), TableInt);
  BitMapElementTy = IT;
  Kind = BitMapKind;
  ++NumBitMaps;
  return;
}

// Store the table in an array.
ArrayType *ArrayTy = ArrayType::get(ValueType, TableSize);
Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);

Array = new GlobalVariable(M, ArrayTy, /*isConstant=*/true,
                           GlobalVariable::PrivateLinkage, Initializer,
                           "switch.table." + FuncName);
Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
// Set the alignment to that of an array items. We will be only loading one
// value out of it.
Array->setAlignment(Align(DL.getPrefTypeAlignment(ValueType)));
Kind = ArrayKind;
5635}

5637Value *SwitchLookupTable::BuildLookup(Value *Index, IRBuilder<> &Builder) {
switch (Kind) {
case SingleValueKind:
  return SingleValue;
case LinearMapKind: {
  // Derive the result value from the input value.
  Value *Result = Builder.CreateIntCast(Index, LinearMultiplier->getType(),
                                        false, "switch.idx.cast");
  if (!LinearMultiplier->isOne())
    Result = Builder.CreateMul(Result, LinearMultiplier, "switch.idx.mult");
  if (!LinearOffset->isZero())
    Result = Builder.CreateAdd(Result, LinearOffset, "switch.offset");
  return Result;
}
case BitMapKind: {
  // Type of the bitmap (e.g. i59).
  IntegerType *MapTy = BitMap->getType();

  // Cast Index to the same type as the bitmap.
  // Note: The Index is <= the number of elements in the table, so
  // truncating it to the width of the bitmask is safe.
  Value *ShiftAmt = Builder.CreateZExtOrTrunc(Index, MapTy, "switch.cast");

  // Multiply the shift amount by the element width.
  ShiftAmt = Builder.CreateMul(
      ShiftAmt, ConstantInt::get(MapTy, BitMapElementTy->getBitWidth()),
      "switch.shiftamt");

  // Shift down.
  Value *DownShifted =
      Builder.CreateLShr(BitMap, ShiftAmt, "switch.downshift");
  // Mask off.