/build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/CodeGen/PeepholeOptimizer.cpp

Bug Summary

File:	build/llvm-toolchain-snapshot-15~++20220420111733+e13d2efed663/llvm/lib/CodeGen/PeepholeOptimizer.cpp
Warning:	line 545, column 30 Called C++ object pointer is null
Annotated Source Code

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1//===- PeepholeOptimizer.cpp - Peephole Optimizations ---------------------===//
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// Perform peephole optimizations on the machine code:
10//
11// - Optimize Extensions
12//
13//     Optimization of sign / zero extension instructions. It may be extended to
14//     handle other instructions with similar properties.
15//
16//     On some targets, some instructions, e.g. X86 sign / zero extension, may
17//     leave the source value in the lower part of the result. This optimization
18//     will replace some uses of the pre-extension value with uses of the
19//     sub-register of the results.
20//
21// - Optimize Comparisons
22//
23//     Optimization of comparison instructions. For instance, in this code:
24//
25//       sub r1, 1
26//       cmp r1, 0
27//       bz  L1
28//
29//     If the "sub" instruction all ready sets (or could be modified to set) the
30//     same flag that the "cmp" instruction sets and that "bz" uses, then we can
31//     eliminate the "cmp" instruction.
32//
33//     Another instance, in this code:
34//
35//       sub r1, r3 | sub r1, imm
36//       cmp r3, r1 or cmp r1, r3 | cmp r1, imm
37//       bge L1
38//
39//     If the branch instruction can use flag from "sub", then we can replace
40//     "sub" with "subs" and eliminate the "cmp" instruction.
41//
42// - Optimize Loads:
43//
44//     Loads that can be folded into a later instruction. A load is foldable
45//     if it loads to virtual registers and the virtual register defined has
46//     a single use.
47//
48// - Optimize Copies and Bitcast (more generally, target specific copies):
49//
50//     Rewrite copies and bitcasts to avoid cross register bank copies
51//     when possible.
52//     E.g., Consider the following example, where capital and lower
53//     letters denote different register file:
54//     b = copy A <-- cross-bank copy
55//     C = copy b <-- cross-bank copy
56//   =>
57//     b = copy A <-- cross-bank copy
58//     C = copy A <-- same-bank copy
59//
60//     E.g., for bitcast:
61//     b = bitcast A <-- cross-bank copy
62//     C = bitcast b <-- cross-bank copy
63//   =>
64//     b = bitcast A <-- cross-bank copy
65//     C = copy A    <-- same-bank copy
66//===----------------------------------------------------------------------===//

68#include "llvm/ADT/DenseMap.h"
69#include "llvm/ADT/Optional.h"
70#include "llvm/ADT/SmallPtrSet.h"
71#include "llvm/ADT/SmallSet.h"
72#include "llvm/ADT/SmallVector.h"
73#include "llvm/ADT/Statistic.h"
74#include "llvm/CodeGen/MachineBasicBlock.h"
75#include "llvm/CodeGen/MachineDominators.h"
76#include "llvm/CodeGen/MachineFunction.h"
77#include "llvm/CodeGen/MachineFunctionPass.h"
78#include "llvm/CodeGen/MachineInstr.h"
79#include "llvm/CodeGen/MachineInstrBuilder.h"
80#include "llvm/CodeGen/MachineLoopInfo.h"
81#include "llvm/CodeGen/MachineOperand.h"
82#include "llvm/CodeGen/MachineRegisterInfo.h"
83#include "llvm/CodeGen/TargetInstrInfo.h"
84#include "llvm/CodeGen/TargetOpcodes.h"
85#include "llvm/CodeGen/TargetRegisterInfo.h"
86#include "llvm/CodeGen/TargetSubtargetInfo.h"
87#include "llvm/InitializePasses.h"
88#include "llvm/MC/LaneBitmask.h"
89#include "llvm/MC/MCInstrDesc.h"
90#include "llvm/Pass.h"
91#include "llvm/Support/CommandLine.h"
92#include "llvm/Support/Debug.h"
93#include "llvm/Support/raw_ostream.h"
94#include <cassert>
95#include <cstdint>
96#include <memory>
97#include <utility>

99using namespace llvm;
100using RegSubRegPair = TargetInstrInfo::RegSubRegPair;
101using RegSubRegPairAndIdx = TargetInstrInfo::RegSubRegPairAndIdx;

103#define DEBUG_TYPE"peephole-opt" "peephole-opt"

105// Optimize Extensions
106static cl::opt<bool>
107Aggressive("aggressive-ext-opt", cl::Hidden,
         cl::desc("Aggressive extension optimization"));

110static cl::opt<bool>
111DisablePeephole("disable-peephole", cl::Hidden, cl::init(false),
              cl::desc("Disable the peephole optimizer"));

114/// Specifiy whether or not the value tracking looks through
115/// complex instructions. When this is true, the value tracker
116/// bails on everything that is not a copy or a bitcast.
117static cl::opt<bool>
118DisableAdvCopyOpt("disable-adv-copy-opt", cl::Hidden, cl::init(false),
                cl::desc("Disable advanced copy optimization"));

121static cl::opt<bool> DisableNAPhysCopyOpt(
  "disable-non-allocatable-phys-copy-opt", cl::Hidden, cl::init(false),
  cl::desc("Disable non-allocatable physical register copy optimization"));

125// Limit the number of PHI instructions to process
126// in PeepholeOptimizer::getNextSource.
127static cl::opt<unsigned> RewritePHILimit(
  "rewrite-phi-limit", cl::Hidden, cl::init(10),
  cl::desc("Limit the length of PHI chains to lookup"));

131// Limit the length of recurrence chain when evaluating the benefit of
132// commuting operands.
133static cl::opt<unsigned> MaxRecurrenceChain(
  "recurrence-chain-limit", cl::Hidden, cl::init(3),
  cl::desc("Maximum length of recurrence chain when evaluating the benefit "
           "of commuting operands"));


139STATISTIC(NumReuse, "Number of extension results reused")static llvm::Statistic NumReuse = {"peephole-opt", "NumReuse"
, "Number of extension results reused"};
140STATISTIC(NumCmps, "Number of compares eliminated")static llvm::Statistic NumCmps = {"peephole-opt", "NumCmps", "Number of compares eliminated"
};
141STATISTIC(NumImmFold, "Number of move immediate folded")static llvm::Statistic NumImmFold = {"peephole-opt", "NumImmFold"
, "Number of move immediate folded"};
142STATISTIC(NumLoadFold, "Number of loads folded")static llvm::Statistic NumLoadFold = {"peephole-opt", "NumLoadFold"
, "Number of loads folded"};
143STATISTIC(NumSelects, "Number of selects optimized")static llvm::Statistic NumSelects = {"peephole-opt", "NumSelects"
, "Number of selects optimized"};
144STATISTIC(NumUncoalescableCopies, "Number of uncoalescable copies optimized")static llvm::Statistic NumUncoalescableCopies = {"peephole-opt"
, "NumUncoalescableCopies", "Number of uncoalescable copies optimized"
};
145STATISTIC(NumRewrittenCopies, "Number of copies rewritten")static llvm::Statistic NumRewrittenCopies = {"peephole-opt", "NumRewrittenCopies"
, "Number of copies rewritten"};
146STATISTIC(NumNAPhysCopies, "Number of non-allocatable physical copies removed")static llvm::Statistic NumNAPhysCopies = {"peephole-opt", "NumNAPhysCopies"
, "Number of non-allocatable physical copies removed"};

148namespace {

class ValueTrackerResult;
class RecurrenceInstr;

class PeepholeOptimizer : public MachineFunctionPass {
  const TargetInstrInfo *TII;
  const TargetRegisterInfo *TRI;
  MachineRegisterInfo *MRI;
  MachineDominatorTree *DT;  // Machine dominator tree
  MachineLoopInfo *MLI;

public:
  static char ID; // Pass identification

  PeepholeOptimizer() : MachineFunctionPass(ID) {
    initializePeepholeOptimizerPass(*PassRegistry::getPassRegistry());
  }

  bool runOnMachineFunction(MachineFunction &MF) override;

  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesCFG();
    MachineFunctionPass::getAnalysisUsage(AU);
    AU.addRequired<MachineLoopInfo>();
    AU.addPreserved<MachineLoopInfo>();
    if (Aggressive) {
      AU.addRequired<MachineDominatorTree>();
      AU.addPreserved<MachineDominatorTree>();
    }
  }

  MachineFunctionProperties getRequiredProperties() const override {
    return MachineFunctionProperties()
      .set(MachineFunctionProperties::Property::IsSSA);
  }

  /// Track Def -> Use info used for rewriting copies.
  using RewriteMapTy = SmallDenseMap<RegSubRegPair, ValueTrackerResult>;

  /// Sequence of instructions that formulate recurrence cycle.
  using RecurrenceCycle = SmallVector<RecurrenceInstr, 4>;

private:
  bool optimizeCmpInstr(MachineInstr &MI);
  bool optimizeExtInstr(MachineInstr &MI, MachineBasicBlock &MBB,
                        SmallPtrSetImpl<MachineInstr*> &LocalMIs);
  bool optimizeSelect(MachineInstr &MI,
                      SmallPtrSetImpl<MachineInstr *> &LocalMIs);
  bool optimizeCondBranch(MachineInstr &MI);
  bool optimizeCoalescableCopy(MachineInstr &MI);
  bool optimizeUncoalescableCopy(MachineInstr &MI,
                                 SmallPtrSetImpl<MachineInstr *> &LocalMIs);
  bool optimizeRecurrence(MachineInstr &PHI);
  bool findNextSource(RegSubRegPair RegSubReg, RewriteMapTy &RewriteMap);
  bool isMoveImmediate(MachineInstr &MI, SmallSet<Register, 4> &ImmDefRegs,
                       DenseMap<Register, MachineInstr *> &ImmDefMIs);
  bool foldImmediate(MachineInstr &MI, SmallSet<Register, 4> &ImmDefRegs,
                     DenseMap<Register, MachineInstr *> &ImmDefMIs);

  /// Finds recurrence cycles, but only ones that formulated around
  /// a def operand and a use operand that are tied. If there is a use
  /// operand commutable with the tied use operand, find recurrence cycle
  /// along that operand as well.
  bool findTargetRecurrence(Register Reg,
                            const SmallSet<Register, 2> &TargetReg,
                            RecurrenceCycle &RC);

  /// If copy instruction \p MI is a virtual register copy, track it in
  /// the set \p CopyMIs. If this virtual register was previously seen as a
  /// copy, replace the uses of this copy with the previously seen copy's
  /// destination register.
  bool foldRedundantCopy(MachineInstr &MI,
                         DenseMap<RegSubRegPair, MachineInstr *> &CopyMIs);

  /// Is the register \p Reg a non-allocatable physical register?
  bool isNAPhysCopy(Register Reg);

  /// If copy instruction \p MI is a non-allocatable virtual<->physical
  /// register copy, track it in the \p NAPhysToVirtMIs map. If this
  /// non-allocatable physical register was previously copied to a virtual
  /// registered and hasn't been clobbered, the virt->phys copy can be
  /// deleted.
  bool foldRedundantNAPhysCopy(
      MachineInstr &MI, DenseMap<Register, MachineInstr *> &NAPhysToVirtMIs);

  bool isLoadFoldable(MachineInstr &MI,
                      SmallSet<Register, 16> &FoldAsLoadDefCandidates);

  /// Check whether \p MI is understood by the register coalescer
  /// but may require some rewriting.
  bool isCoalescableCopy(const MachineInstr &MI) {
    // SubregToRegs are not interesting, because they are already register
    // coalescer friendly.
    return MI.isCopy() || (!DisableAdvCopyOpt &&
                           (MI.isRegSequence() || MI.isInsertSubreg() ||
                            MI.isExtractSubreg()));
  }

  /// Check whether \p MI is a copy like instruction that is
  /// not recognized by the register coalescer.
  bool isUncoalescableCopy(const MachineInstr &MI) {
    return MI.isBitcast() ||
           (!DisableAdvCopyOpt &&
            (MI.isRegSequenceLike() || MI.isInsertSubregLike() ||
             MI.isExtractSubregLike()));
  }

  MachineInstr &rewriteSource(MachineInstr &CopyLike,
                              RegSubRegPair Def, RewriteMapTy &RewriteMap);
};

/// Helper class to hold instructions that are inside recurrence cycles.
/// The recurrence cycle is formulated around 1) a def operand and its
/// tied use operand, or 2) a def operand and a use operand that is commutable
/// with another use operand which is tied to the def operand. In the latter
/// case, index of the tied use operand and the commutable use operand are
/// maintained with CommutePair.
class RecurrenceInstr {
public:
  using IndexPair = std::pair<unsigned, unsigned>;

  RecurrenceInstr(MachineInstr *MI) : MI(MI) {}
  RecurrenceInstr(MachineInstr *MI, unsigned Idx1, unsigned Idx2)
    : MI(MI), CommutePair(std::make_pair(Idx1, Idx2)) {}

  MachineInstr *getMI() const { return MI; }
  Optional<IndexPair> getCommutePair() const { return CommutePair; }

private:
  MachineInstr *MI;
  Optional<IndexPair> CommutePair;
};

/// Helper class to hold a reply for ValueTracker queries.
/// Contains the returned sources for a given search and the instructions
/// where the sources were tracked from.
class ValueTrackerResult {
private:
  /// Track all sources found by one ValueTracker query.
  SmallVector<RegSubRegPair, 2> RegSrcs;

  /// Instruction using the sources in 'RegSrcs'.
  const MachineInstr *Inst = nullptr;

public:
  ValueTrackerResult() = default;

  ValueTrackerResult(Register Reg, unsigned SubReg) {
    addSource(Reg, SubReg);
  }

  bool isValid() const { return getNumSources() > 0; }

  void setInst(const MachineInstr *I) { Inst = I; }
  const MachineInstr *getInst() const { return Inst; }

  void clear() {
    RegSrcs.clear();
    Inst = nullptr;
  }

  void addSource(Register SrcReg, unsigned SrcSubReg) {
    RegSrcs.push_back(RegSubRegPair(SrcReg, SrcSubReg));
  }

  void setSource(int Idx, Register SrcReg, unsigned SrcSubReg) {
    assert(Idx < getNumSources() && "Reg pair source out of index")(static_cast <bool> (Idx < getNumSources() &&
 "Reg pair source out of index") ? void (0) : __assert_fail (
"Idx < getNumSources() && \"Reg pair source out of index\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 315, __extension__
 __PRETTY_FUNCTION__));
    RegSrcs[Idx] = RegSubRegPair(SrcReg, SrcSubReg);
  }

  int getNumSources() const { return RegSrcs.size(); }

  RegSubRegPair getSrc(int Idx) const {
    return RegSrcs[Idx];
  }

  Register getSrcReg(int Idx) const {
    assert(Idx < getNumSources() && "Reg source out of index")(static_cast <bool> (Idx < getNumSources() &&
 "Reg source out of index") ? void (0) : __assert_fail ("Idx < getNumSources() && \"Reg source out of index\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 326, __extension__
 __PRETTY_FUNCTION__));
    return RegSrcs[Idx].Reg;
  }

  unsigned getSrcSubReg(int Idx) const {
    assert(Idx < getNumSources() && "SubReg source out of index")(static_cast <bool> (Idx < getNumSources() &&
 "SubReg source out of index") ? void (0) : __assert_fail ("Idx < getNumSources() && \"SubReg source out of index\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 331, __extension__
 __PRETTY_FUNCTION__));
    return RegSrcs[Idx].SubReg;
  }

  bool operator==(const ValueTrackerResult &Other) const {
    if (Other.getInst() != getInst())
      return false;

    if (Other.getNumSources() != getNumSources())
      return false;

    for (int i = 0, e = Other.getNumSources(); i != e; ++i)
      if (Other.getSrcReg(i) != getSrcReg(i) ||
          Other.getSrcSubReg(i) != getSrcSubReg(i))
        return false;
    return true;
  }
};

/// Helper class to track the possible sources of a value defined by
/// a (chain of) copy related instructions.
/// Given a definition (instruction and definition index), this class
/// follows the use-def chain to find successive suitable sources.
/// The given source can be used to rewrite the definition into
/// def = COPY src.
///
/// For instance, let us consider the following snippet:
/// v0 =
/// v2 = INSERT_SUBREG v1, v0, sub0
/// def = COPY v2.sub0
///
/// Using a ValueTracker for def = COPY v2.sub0 will give the following
/// suitable sources:
/// v2.sub0 and v0.
/// Then, def can be rewritten into def = COPY v0.
class ValueTracker {
private:
  /// The current point into the use-def chain.
  const MachineInstr *Def = nullptr;

  /// The index of the definition in Def.
  unsigned DefIdx = 0;

  /// The sub register index of the definition.
  unsigned DefSubReg;

  /// The register where the value can be found.
  Register Reg;

  /// MachineRegisterInfo used to perform tracking.
  const MachineRegisterInfo &MRI;

  /// Optional TargetInstrInfo used to perform some complex tracking.
  const TargetInstrInfo *TII;

  /// Dispatcher to the right underlying implementation of getNextSource.
  ValueTrackerResult getNextSourceImpl();

  /// Specialized version of getNextSource for Copy instructions.
  ValueTrackerResult getNextSourceFromCopy();

  /// Specialized version of getNextSource for Bitcast instructions.
  ValueTrackerResult getNextSourceFromBitcast();

  /// Specialized version of getNextSource for RegSequence instructions.
  ValueTrackerResult getNextSourceFromRegSequence();

  /// Specialized version of getNextSource for InsertSubreg instructions.
  ValueTrackerResult getNextSourceFromInsertSubreg();

  /// Specialized version of getNextSource for ExtractSubreg instructions.
  ValueTrackerResult getNextSourceFromExtractSubreg();

  /// Specialized version of getNextSource for SubregToReg instructions.
  ValueTrackerResult getNextSourceFromSubregToReg();

  /// Specialized version of getNextSource for PHI instructions.
  ValueTrackerResult getNextSourceFromPHI();

public:
  /// Create a ValueTracker instance for the value defined by \p Reg.
  /// \p DefSubReg represents the sub register index the value tracker will
  /// track. It does not need to match the sub register index used in the
  /// definition of \p Reg.
  /// If \p Reg is a physical register, a value tracker constructed with
  /// this constructor will not find any alternative source.
  /// Indeed, when \p Reg is a physical register that constructor does not
  /// know which definition of \p Reg it should track.
  /// Use the next constructor to track a physical register.
  ValueTracker(Register Reg, unsigned DefSubReg,
               const MachineRegisterInfo &MRI,
               const TargetInstrInfo *TII = nullptr)
      : DefSubReg(DefSubReg), Reg(Reg), MRI(MRI), TII(TII) {
    if (!Reg.isPhysical()) {
      Def = MRI.getVRegDef(Reg);
      DefIdx = MRI.def_begin(Reg).getOperandNo();
    }
  }

  /// Following the use-def chain, get the next available source
  /// for the tracked value.
  /// \return A ValueTrackerResult containing a set of registers
  /// and sub registers with tracked values. A ValueTrackerResult with
  /// an empty set of registers means no source was found.
  ValueTrackerResult getNextSource();
};

438} // end anonymous namespace

440char PeepholeOptimizer::ID = 0;

442char &llvm::PeepholeOptimizerID = PeepholeOptimizer::ID;

444INITIALIZE_PASS_BEGIN(PeepholeOptimizer, DEBUG_TYPE,static void *initializePeepholeOptimizerPassOnce(PassRegistry
 &Registry) {
                    "Peephole Optimizations", false, false)static void *initializePeepholeOptimizerPassOnce(PassRegistry
 &Registry) {
446INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)initializeMachineDominatorTreePass(Registry);
447INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)initializeMachineLoopInfoPass(Registry);
448INITIALIZE_PASS_END(PeepholeOptimizer, DEBUG_TYPE,PassInfo *PI = new PassInfo( "Peephole Optimizations", "peephole-opt"
, &PeepholeOptimizer::ID, PassInfo::NormalCtor_t(callDefaultCtor
<PeepholeOptimizer>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializePeepholeOptimizerPassFlag
; void llvm::initializePeepholeOptimizerPass(PassRegistry &
Registry) { llvm::call_once(InitializePeepholeOptimizerPassFlag
, initializePeepholeOptimizerPassOnce, std::ref(Registry)); }
                  "Peephole Optimizations", false, false)PassInfo *PI = new PassInfo( "Peephole Optimizations", "peephole-opt"
, &PeepholeOptimizer::ID, PassInfo::NormalCtor_t(callDefaultCtor
<PeepholeOptimizer>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializePeepholeOptimizerPassFlag
; void llvm::initializePeepholeOptimizerPass(PassRegistry &
Registry) { llvm::call_once(InitializePeepholeOptimizerPassFlag
, initializePeepholeOptimizerPassOnce, std::ref(Registry)); }

451/// If instruction is a copy-like instruction, i.e. it reads a single register
452/// and writes a single register and it does not modify the source, and if the
453/// source value is preserved as a sub-register of the result, then replace all
454/// reachable uses of the source with the subreg of the result.
455///
456/// Do not generate an EXTRACT that is used only in a debug use, as this changes
457/// the code. Since this code does not currently share EXTRACTs, just ignore all
458/// debug uses.
459bool PeepholeOptimizer::
460optimizeExtInstr(MachineInstr &MI, MachineBasicBlock &MBB,
               SmallPtrSetImpl<MachineInstr*> &LocalMIs) {
Register SrcReg, DstReg;
unsigned SubIdx;
if (!TII->isCoalescableExtInstr(MI, SrcReg, DstReg, SubIdx))
21
←
Assuming the condition is false→
  return false;

if (DstReg.isPhysical() || SrcReg.isPhysical())
22
←
Taking false branch→
  return false;

if (MRI->hasOneNonDBGUse(SrcReg))
23
←
Assuming the condition is false→
24
←
Taking false branch→
  // No other uses.
  return false;

// Ensure DstReg can get a register class that actually supports
// sub-registers. Don't change the class until we commit.
const TargetRegisterClass *DstRC = MRI->getRegClass(DstReg);
DstRC = TRI->getSubClassWithSubReg(DstRC, SubIdx);
if (!DstRC)
25
←
Assuming 'DstRC' is non-null→
26
←
Taking false branch→
  return false;

// The ext instr may be operating on a sub-register of SrcReg as well.
// PPC::EXTSW is a 32 -> 64-bit sign extension, but it reads a 64-bit
// register.
// If UseSrcSubIdx is Set, SubIdx also applies to SrcReg, and only uses of
// SrcReg:SubIdx should be replaced.
bool UseSrcSubIdx =
    TRI->getSubClassWithSubReg(MRI->getRegClass(SrcReg), SubIdx) != nullptr;
27
←
Assuming the condition is false→

// The source has other uses. See if we can replace the other uses with use of
// the result of the extension.
SmallPtrSet<MachineBasicBlock*, 4> ReachedBBs;
for (MachineInstr &UI : MRI->use_nodbg_instructions(DstReg))
  ReachedBBs.insert(UI.getParent());

// Uses that are in the same BB of uses of the result of the instruction.
SmallVector<MachineOperand*, 8> Uses;

// Uses that the result of the instruction can reach.
SmallVector<MachineOperand*, 8> ExtendedUses;

bool ExtendLife = true;
for (MachineOperand &UseMO : MRI->use_nodbg_operands(SrcReg)) {
  MachineInstr *UseMI = UseMO.getParent();
  if (UseMI == &MI)
28
←
Assuming the condition is false→
29
←
Taking false branch→
    continue;

  if (UseMI->isPHI()) {
    ExtendLife = false;
    continue;
  }

  // Only accept uses of SrcReg:SubIdx.
  if (UseSrcSubIdx29.1
'UseSrcSubIdx' is false
 && UseMO.getSubReg() != SubIdx)
    continue;

  // It's an error to translate this:
  //
  //    %reg1025 = <sext> %reg1024
  //     ...
  //    %reg1026 = SUBREG_TO_REG 0, %reg1024, 4
  //
  // into this:
  //
  //    %reg1025 = <sext> %reg1024
  //     ...
  //    %reg1027 = COPY %reg1025:4
  //    %reg1026 = SUBREG_TO_REG 0, %reg1027, 4
  //
  // The problem here is that SUBREG_TO_REG is there to assert that an
  // implicit zext occurs. It doesn't insert a zext instruction. If we allow
  // the COPY here, it will give us the value after the <sext>, not the
  // original value of %reg1024 before <sext>.
  if (UseMI->getOpcode() == TargetOpcode::SUBREG_TO_REG)
30
←
Assuming the condition is false→
31
←
Taking false branch→
    continue;

  MachineBasicBlock *UseMBB = UseMI->getParent();
  if (UseMBB == &MBB) {
32
←
Assuming the condition is false→
33
←
Taking false branch→
    // Local uses that come after the extension.
    if (!LocalMIs.count(UseMI))
      Uses.push_back(&UseMO);
  } else if (ReachedBBs.count(UseMBB)) {
34
←
Assuming the condition is false→
    // Non-local uses where the result of the extension is used. Always
    // replace these unless it's a PHI.
    Uses.push_back(&UseMO);
  } else if (Aggressive && DT->dominates(&MBB, UseMBB)) {
35
←
Assuming the condition is true→
36
←
Called C++ object pointer is null
    // We may want to extend the live range of the extension result in order
    // to replace these uses.
    ExtendedUses.push_back(&UseMO);
  } else {
    // Both will be live out of the def MBB anyway. Don't extend live range of
    // the extension result.
    ExtendLife = false;
    break;
  }
}

if (ExtendLife && !ExtendedUses.empty())
  // Extend the liveness of the extension result.
  Uses.append(ExtendedUses.begin(), ExtendedUses.end());

// Now replace all uses.
bool Changed = false;
if (!Uses.empty()) {
  SmallPtrSet<MachineBasicBlock*, 4> PHIBBs;

  // Look for PHI uses of the extended result, we don't want to extend the
  // liveness of a PHI input. It breaks all kinds of assumptions down
  // stream. A PHI use is expected to be the kill of its source values.
  for (MachineInstr &UI : MRI->use_nodbg_instructions(DstReg))
    if (UI.isPHI())
      PHIBBs.insert(UI.getParent());

  const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
  for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
    MachineOperand *UseMO = Uses[i];
    MachineInstr *UseMI = UseMO->getParent();
    MachineBasicBlock *UseMBB = UseMI->getParent();
    if (PHIBBs.count(UseMBB))
      continue;

    // About to add uses of DstReg, clear DstReg's kill flags.
    if (!Changed) {
      MRI->clearKillFlags(DstReg);
      MRI->constrainRegClass(DstReg, DstRC);
    }

    // SubReg defs are illegal in machine SSA phase,
    // we should not generate SubReg defs.
    //
    // For example, for the instructions:
    //
    // %1:g8rc_and_g8rc_nox0 = EXTSW %0:g8rc
    // %3:gprc_and_gprc_nor0 = COPY %0.sub_32:g8rc
    //
    // We should generate:
    //
    // %1:g8rc_and_g8rc_nox0 = EXTSW %0:g8rc
    // %6:gprc_and_gprc_nor0 = COPY %1.sub_32:g8rc_and_g8rc_nox0
    // %3:gprc_and_gprc_nor0 = COPY %6:gprc_and_gprc_nor0
    //
    if (UseSrcSubIdx)
      RC = MRI->getRegClass(UseMI->getOperand(0).getReg());

    Register NewVR = MRI->createVirtualRegister(RC);
    BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
            TII->get(TargetOpcode::COPY), NewVR)
      .addReg(DstReg, 0, SubIdx);
    if (UseSrcSubIdx)
      UseMO->setSubReg(0);

    UseMO->setReg(NewVR);
    ++NumReuse;
    Changed = true;
  }
}

return Changed;
618}

620/// If the instruction is a compare and the previous instruction it's comparing
621/// against already sets (or could be modified to set) the same flag as the
622/// compare, then we can remove the comparison and use the flag from the
623/// previous instruction.
624bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr &MI) {
// If this instruction is a comparison against zero and isn't comparing a
// physical register, we can try to optimize it.
Register SrcReg, SrcReg2;
int64_t CmpMask, CmpValue;
if (!TII->analyzeCompare(MI, SrcReg, SrcReg2, CmpMask, CmpValue) ||
    SrcReg.isPhysical() || SrcReg2.isPhysical())
  return false;

// Attempt to optimize the comparison instruction.
LLVM_DEBUG(dbgs() << "Attempting to optimize compare: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Attempting to optimize compare: "
 << MI; } } while (false);
if (TII->optimizeCompareInstr(MI, SrcReg, SrcReg2, CmpMask, CmpValue, MRI)) {
  LLVM_DEBUG(dbgs() << "  -> Successfully optimized compare!\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "  -> Successfully optimized compare!\n"
; } } while (false);
  ++NumCmps;
  return true;
}

return false;
642}

644/// Optimize a select instruction.
645bool PeepholeOptimizer::optimizeSelect(MachineInstr &MI,
                          SmallPtrSetImpl<MachineInstr *> &LocalMIs) {
unsigned TrueOp = 0;
unsigned FalseOp = 0;
bool Optimizable = false;
SmallVector<MachineOperand, 4> Cond;
if (TII->analyzeSelect(MI, Cond, TrueOp, FalseOp, Optimizable))
  return false;
if (!Optimizable)
  return false;
if (!TII->optimizeSelect(MI, LocalMIs))
  return false;
LLVM_DEBUG(dbgs() << "Deleting select: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Deleting select: " <<
 MI; } } while (false);
MI.eraseFromParent();
++NumSelects;
return true;
661}

663/// Check if a simpler conditional branch can be generated.
664bool PeepholeOptimizer::optimizeCondBranch(MachineInstr &MI) {
return TII->optimizeCondBranch(MI);
666}

668/// Try to find the next source that share the same register file
669/// for the value defined by \p Reg and \p SubReg.
670/// When true is returned, the \p RewriteMap can be used by the client to
671/// retrieve all Def -> Use along the way up to the next source. Any found
672/// Use that is not itself a key for another entry, is the next source to
673/// use. During the search for the next source, multiple sources can be found
674/// given multiple incoming sources of a PHI instruction. In this case, we
675/// look in each PHI source for the next source; all found next sources must
676/// share the same register file as \p Reg and \p SubReg. The client should
677/// then be capable to rewrite all intermediate PHIs to get the next source.
678/// \return False if no alternative sources are available. True otherwise.
679bool PeepholeOptimizer::findNextSource(RegSubRegPair RegSubReg,
                                     RewriteMapTy &RewriteMap) {
// Do not try to find a new source for a physical register.
// So far we do not have any motivating example for doing that.
// Thus, instead of maintaining untested code, we will revisit that if
// that changes at some point.
Register Reg = RegSubReg.Reg;
if (Reg.isPhysical())
  return false;
const TargetRegisterClass *DefRC = MRI->getRegClass(Reg);

SmallVector<RegSubRegPair, 4> SrcToLook;
RegSubRegPair CurSrcPair = RegSubReg;
SrcToLook.push_back(CurSrcPair);

unsigned PHICount = 0;
do {
  CurSrcPair = SrcToLook.pop_back_val();
  // As explained above, do not handle physical registers
  if (Register::isPhysicalRegister(CurSrcPair.Reg))
    return false;

  ValueTracker ValTracker(CurSrcPair.Reg, CurSrcPair.SubReg, *MRI, TII);

  // Follow the chain of copies until we find a more suitable source, a phi
  // or have to abort.
  while (true) {
    ValueTrackerResult Res = ValTracker.getNextSource();
    // Abort at the end of a chain (without finding a suitable source).
    if (!Res.isValid())
      return false;

    // Insert the Def -> Use entry for the recently found source.
    ValueTrackerResult CurSrcRes = RewriteMap.lookup(CurSrcPair);
    if (CurSrcRes.isValid()) {
      assert(CurSrcRes == Res && "ValueTrackerResult found must match")(static_cast <bool> (CurSrcRes == Res && "ValueTrackerResult found must match"
) ? void (0) : __assert_fail ("CurSrcRes == Res && \"ValueTrackerResult found must match\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 714, __extension__
 __PRETTY_FUNCTION__));
      // An existent entry with multiple sources is a PHI cycle we must avoid.
      // Otherwise it's an entry with a valid next source we already found.
      if (CurSrcRes.getNumSources() > 1) {
        LLVM_DEBUG(dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "findNextSource: found PHI cycle, aborting...\n"
; } } while (false)
                   << "findNextSource: found PHI cycle, aborting...\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "findNextSource: found PHI cycle, aborting...\n"
; } } while (false);
        return false;
      }
      break;
    }
    RewriteMap.insert(std::make_pair(CurSrcPair, Res));

    // ValueTrackerResult usually have one source unless it's the result from
    // a PHI instruction. Add the found PHI edges to be looked up further.
    unsigned NumSrcs = Res.getNumSources();
    if (NumSrcs > 1) {
      PHICount++;
      if (PHICount >= RewritePHILimit) {
        LLVM_DEBUG(dbgs() << "findNextSource: PHI limit reached\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "findNextSource: PHI limit reached\n"
; } } while (false);
        return false;
      }

      for (unsigned i = 0; i < NumSrcs; ++i)
        SrcToLook.push_back(Res.getSrc(i));
      break;
    }

    CurSrcPair = Res.getSrc(0);
    // Do not extend the live-ranges of physical registers as they add
    // constraints to the register allocator. Moreover, if we want to extend
    // the live-range of a physical register, unlike SSA virtual register,
    // we will have to check that they aren't redefine before the related use.
    if (Register::isPhysicalRegister(CurSrcPair.Reg))
      return false;

    // Keep following the chain if the value isn't any better yet.
    const TargetRegisterClass *SrcRC = MRI->getRegClass(CurSrcPair.Reg);
    if (!TRI->shouldRewriteCopySrc(DefRC, RegSubReg.SubReg, SrcRC,
                                   CurSrcPair.SubReg))
      continue;

    // We currently cannot deal with subreg operands on PHI instructions
    // (see insertPHI()).
    if (PHICount > 0 && CurSrcPair.SubReg != 0)
      continue;

    // We found a suitable source, and are done with this chain.
    break;
  }
} while (!SrcToLook.empty());

// If we did not find a more suitable source, there is nothing to optimize.
return CurSrcPair.Reg != Reg;
767}

769/// Insert a PHI instruction with incoming edges \p SrcRegs that are
770/// guaranteed to have the same register class. This is necessary whenever we
771/// successfully traverse a PHI instruction and find suitable sources coming
772/// from its edges. By inserting a new PHI, we provide a rewritten PHI def
773/// suitable to be used in a new COPY instruction.
774static MachineInstr &
775insertPHI(MachineRegisterInfo &MRI, const TargetInstrInfo &TII,
        const SmallVectorImpl<RegSubRegPair> &SrcRegs,
        MachineInstr &OrigPHI) {
assert(!SrcRegs.empty() && "No sources to create a PHI instruction?")(static_cast <bool> (!SrcRegs.empty() && "No sources to create a PHI instruction?"
) ? void (0) : __assert_fail ("!SrcRegs.empty() && \"No sources to create a PHI instruction?\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 778, __extension__
 __PRETTY_FUNCTION__));

const TargetRegisterClass *NewRC = MRI.getRegClass(SrcRegs[0].Reg);
// NewRC is only correct if no subregisters are involved. findNextSource()
// should have rejected those cases already.
assert(SrcRegs[0].SubReg == 0 && "should not have subreg operand")(static_cast <bool> (SrcRegs[0].SubReg == 0 && "should not have subreg operand"
) ? void (0) : __assert_fail ("SrcRegs[0].SubReg == 0 && \"should not have subreg operand\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 783, __extension__
 __PRETTY_FUNCTION__));
Register NewVR = MRI.createVirtualRegister(NewRC);
MachineBasicBlock *MBB = OrigPHI.getParent();
MachineInstrBuilder MIB = BuildMI(*MBB, &OrigPHI, OrigPHI.getDebugLoc(),
                                  TII.get(TargetOpcode::PHI), NewVR);

unsigned MBBOpIdx = 2;
for (const RegSubRegPair &RegPair : SrcRegs) {
  MIB.addReg(RegPair.Reg, 0, RegPair.SubReg);
  MIB.addMBB(OrigPHI.getOperand(MBBOpIdx).getMBB());
  // Since we're extended the lifetime of RegPair.Reg, clear the
  // kill flags to account for that and make RegPair.Reg reaches
  // the new PHI.
  MRI.clearKillFlags(RegPair.Reg);
  MBBOpIdx += 2;
}

return *MIB;
801}

803namespace {

805/// Interface to query instructions amenable to copy rewriting.
806class Rewriter {
807protected:
MachineInstr &CopyLike;
unsigned CurrentSrcIdx = 0;   ///< The index of the source being rewritten.
810public:
Rewriter(MachineInstr &CopyLike) : CopyLike(CopyLike) {}
virtual ~Rewriter() = default;

/// Get the next rewritable source (SrcReg, SrcSubReg) and
/// the related value that it affects (DstReg, DstSubReg).
/// A source is considered rewritable if its register class and the
/// register class of the related DstReg may not be register
/// coalescer friendly. In other words, given a copy-like instruction
/// not all the arguments may be returned at rewritable source, since
/// some arguments are none to be register coalescer friendly.
///
/// Each call of this method moves the current source to the next
/// rewritable source.
/// For instance, let CopyLike be the instruction to rewrite.
/// CopyLike has one definition and one source:
/// dst.dstSubIdx = CopyLike src.srcSubIdx.
///
/// The first call will give the first rewritable source, i.e.,
/// the only source this instruction has:
/// (SrcReg, SrcSubReg) = (src, srcSubIdx).
/// This source defines the whole definition, i.e.,
/// (DstReg, DstSubReg) = (dst, dstSubIdx).
///
/// The second and subsequent calls will return false, as there is only one
/// rewritable source.
///
/// \return True if a rewritable source has been found, false otherwise.
/// The output arguments are valid if and only if true is returned.
virtual bool getNextRewritableSource(RegSubRegPair &Src,
                                     RegSubRegPair &Dst) = 0;

/// Rewrite the current source with \p NewReg and \p NewSubReg if possible.
/// \return True if the rewriting was possible, false otherwise.
virtual bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) = 0;
845};

847/// Rewriter for COPY instructions.
848class CopyRewriter : public Rewriter {
849public:
CopyRewriter(MachineInstr &MI) : Rewriter(MI) {
  assert(MI.isCopy() && "Expected copy instruction")(static_cast <bool> (MI.isCopy() && "Expected copy instruction"
) ? void (0) : __assert_fail ("MI.isCopy() && \"Expected copy instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 851, __extension__
 __PRETTY_FUNCTION__));
}
virtual ~CopyRewriter() = default;

bool getNextRewritableSource(RegSubRegPair &Src,
                             RegSubRegPair &Dst) override {
  // CurrentSrcIdx > 0 means this function has already been called.
  if (CurrentSrcIdx > 0)
    return false;
  // This is the first call to getNextRewritableSource.
  // Move the CurrentSrcIdx to remember that we made that call.
  CurrentSrcIdx = 1;
  // The rewritable source is the argument.
  const MachineOperand &MOSrc = CopyLike.getOperand(1);
  Src = RegSubRegPair(MOSrc.getReg(), MOSrc.getSubReg());
  // What we track are the alternative sources of the definition.
  const MachineOperand &MODef = CopyLike.getOperand(0);
  Dst = RegSubRegPair(MODef.getReg(), MODef.getSubReg());
  return true;
}

bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) override {
  if (CurrentSrcIdx != 1)
    return false;
  MachineOperand &MOSrc = CopyLike.getOperand(CurrentSrcIdx);
  MOSrc.setReg(NewReg);
  MOSrc.setSubReg(NewSubReg);
  return true;
}
880};

882/// Helper class to rewrite uncoalescable copy like instructions
883/// into new COPY (coalescable friendly) instructions.
884class UncoalescableRewriter : public Rewriter {
unsigned NumDefs;  ///< Number of defs in the bitcast.

887public:
UncoalescableRewriter(MachineInstr &MI) : Rewriter(MI) {
  NumDefs = MI.getDesc().getNumDefs();
}

/// \see See Rewriter::getNextRewritableSource()
/// All such sources need to be considered rewritable in order to
/// rewrite a uncoalescable copy-like instruction. This method return
/// each definition that must be checked if rewritable.
bool getNextRewritableSource(RegSubRegPair &Src,
                             RegSubRegPair &Dst) override {
  // Find the next non-dead definition and continue from there.
  if (CurrentSrcIdx == NumDefs)
    return false;

  while (CopyLike.getOperand(CurrentSrcIdx).isDead()) {
    ++CurrentSrcIdx;
    if (CurrentSrcIdx == NumDefs)
      return false;
  }

  // What we track are the alternative sources of the definition.
  Src = RegSubRegPair(0, 0);
  const MachineOperand &MODef = CopyLike.getOperand(CurrentSrcIdx);
  Dst = RegSubRegPair(MODef.getReg(), MODef.getSubReg());

  CurrentSrcIdx++;
  return true;
}

bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) override {
  return false;
}
920};

922/// Specialized rewriter for INSERT_SUBREG instruction.
923class InsertSubregRewriter : public Rewriter {
924public:
InsertSubregRewriter(MachineInstr &MI) : Rewriter(MI) {
  assert(MI.isInsertSubreg() && "Invalid instruction")(static_cast <bool> (MI.isInsertSubreg() && "Invalid instruction"
) ? void (0) : __assert_fail ("MI.isInsertSubreg() && \"Invalid instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 926, __extension__
 __PRETTY_FUNCTION__));
}

/// \see See Rewriter::getNextRewritableSource()
/// Here CopyLike has the following form:
/// dst = INSERT_SUBREG Src1, Src2.src2SubIdx, subIdx.
/// Src1 has the same register class has dst, hence, there is
/// nothing to rewrite.
/// Src2.src2SubIdx, may not be register coalescer friendly.
/// Therefore, the first call to this method returns:
/// (SrcReg, SrcSubReg) = (Src2, src2SubIdx).
/// (DstReg, DstSubReg) = (dst, subIdx).
///
/// Subsequence calls will return false.
bool getNextRewritableSource(RegSubRegPair &Src,
                             RegSubRegPair &Dst) override {
  // If we already get the only source we can rewrite, return false.
  if (CurrentSrcIdx == 2)
    return false;
  // We are looking at v2 = INSERT_SUBREG v0, v1, sub0.
  CurrentSrcIdx = 2;
  const MachineOperand &MOInsertedReg = CopyLike.getOperand(2);
  Src = RegSubRegPair(MOInsertedReg.getReg(), MOInsertedReg.getSubReg());
  const MachineOperand &MODef = CopyLike.getOperand(0);

  // We want to track something that is compatible with the
  // partial definition.
  if (MODef.getSubReg())
    // Bail if we have to compose sub-register indices.
    return false;
  Dst = RegSubRegPair(MODef.getReg(),
                      (unsigned)CopyLike.getOperand(3).getImm());
  return true;
}

bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) override {
  if (CurrentSrcIdx != 2)
    return false;
  // We are rewriting the inserted reg.
  MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx);
  MO.setReg(NewReg);
  MO.setSubReg(NewSubReg);
  return true;
}
970};

972/// Specialized rewriter for EXTRACT_SUBREG instruction.
973class ExtractSubregRewriter : public Rewriter {
const TargetInstrInfo &TII;

976public:
ExtractSubregRewriter(MachineInstr &MI, const TargetInstrInfo &TII)
    : Rewriter(MI), TII(TII) {
  assert(MI.isExtractSubreg() && "Invalid instruction")(static_cast <bool> (MI.isExtractSubreg() && "Invalid instruction"
) ? void (0) : __assert_fail ("MI.isExtractSubreg() && \"Invalid instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 979, __extension__
 __PRETTY_FUNCTION__));
}

/// \see Rewriter::getNextRewritableSource()
/// Here CopyLike has the following form:
/// dst.dstSubIdx = EXTRACT_SUBREG Src, subIdx.
/// There is only one rewritable source: Src.subIdx,
/// which defines dst.dstSubIdx.
bool getNextRewritableSource(RegSubRegPair &Src,
                             RegSubRegPair &Dst) override {
  // If we already get the only source we can rewrite, return false.
  if (CurrentSrcIdx == 1)
    return false;
  // We are looking at v1 = EXTRACT_SUBREG v0, sub0.
  CurrentSrcIdx = 1;
  const MachineOperand &MOExtractedReg = CopyLike.getOperand(1);
  // If we have to compose sub-register indices, bail out.
  if (MOExtractedReg.getSubReg())
    return false;

  Src = RegSubRegPair(MOExtractedReg.getReg(),
                      CopyLike.getOperand(2).getImm());

  // We want to track something that is compatible with the definition.
  const MachineOperand &MODef = CopyLike.getOperand(0);
  Dst = RegSubRegPair(MODef.getReg(), MODef.getSubReg());
  return true;
}

bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) override {
  // The only source we can rewrite is the input register.
  if (CurrentSrcIdx != 1)
    return false;

  CopyLike.getOperand(CurrentSrcIdx).setReg(NewReg);

  // If we find a source that does not require to extract something,
  // rewrite the operation with a copy.
  if (!NewSubReg) {
    // Move the current index to an invalid position.
    // We do not want another call to this method to be able
    // to do any change.
    CurrentSrcIdx = -1;
    // Rewrite the operation as a COPY.
    // Get rid of the sub-register index.
    CopyLike.removeOperand(2);
    // Morph the operation into a COPY.
    CopyLike.setDesc(TII.get(TargetOpcode::COPY));
    return true;
  }
  CopyLike.getOperand(CurrentSrcIdx + 1).setImm(NewSubReg);
  return true;
}
1032};

1034/// Specialized rewriter for REG_SEQUENCE instruction.
1035class RegSequenceRewriter : public Rewriter {
1036public:
RegSequenceRewriter(MachineInstr &MI) : Rewriter(MI) {
  assert(MI.isRegSequence() && "Invalid instruction")(static_cast <bool> (MI.isRegSequence() && "Invalid instruction"
) ? void (0) : __assert_fail ("MI.isRegSequence() && \"Invalid instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1038, __extension__
 __PRETTY_FUNCTION__));
}

/// \see Rewriter::getNextRewritableSource()
/// Here CopyLike has the following form:
/// dst = REG_SEQUENCE Src1.src1SubIdx, subIdx1, Src2.src2SubIdx, subIdx2.
/// Each call will return a different source, walking all the available
/// source.
///
/// The first call returns:
/// (SrcReg, SrcSubReg) = (Src1, src1SubIdx).
/// (DstReg, DstSubReg) = (dst, subIdx1).
///
/// The second call returns:
/// (SrcReg, SrcSubReg) = (Src2, src2SubIdx).
/// (DstReg, DstSubReg) = (dst, subIdx2).
///
/// And so on, until all the sources have been traversed, then
/// it returns false.
bool getNextRewritableSource(RegSubRegPair &Src,
                             RegSubRegPair &Dst) override {
  // We are looking at v0 = REG_SEQUENCE v1, sub1, v2, sub2, etc.

  // If this is the first call, move to the first argument.
  if (CurrentSrcIdx == 0) {
    CurrentSrcIdx = 1;
  } else {
    // Otherwise, move to the next argument and check that it is valid.
    CurrentSrcIdx += 2;
    if (CurrentSrcIdx >= CopyLike.getNumOperands())
      return false;
  }
  const MachineOperand &MOInsertedReg = CopyLike.getOperand(CurrentSrcIdx);
  Src.Reg = MOInsertedReg.getReg();
  // If we have to compose sub-register indices, bail out.
  if ((Src.SubReg = MOInsertedReg.getSubReg()))
    return false;

  // We want to track something that is compatible with the related
  // partial definition.
  Dst.SubReg = CopyLike.getOperand(CurrentSrcIdx + 1).getImm();

  const MachineOperand &MODef = CopyLike.getOperand(0);
  Dst.Reg = MODef.getReg();
  // If we have to compose sub-registers, bail.
  return MODef.getSubReg() == 0;
}

bool RewriteCurrentSource(Register NewReg, unsigned NewSubReg) override {
  // We cannot rewrite out of bound operands.
  // Moreover, rewritable sources are at odd positions.
  if ((CurrentSrcIdx & 1) != 1 || CurrentSrcIdx > CopyLike.getNumOperands())
    return false;

  MachineOperand &MO = CopyLike.getOperand(CurrentSrcIdx);
  MO.setReg(NewReg);
  MO.setSubReg(NewSubReg);
  return true;
}
1097};

1099} // end anonymous namespace

1101/// Get the appropriated Rewriter for \p MI.
1102/// \return A pointer to a dynamically allocated Rewriter or nullptr if no
1103/// rewriter works for \p MI.
1104static Rewriter *getCopyRewriter(MachineInstr &MI, const TargetInstrInfo &TII) {
// Handle uncoalescable copy-like instructions.
if (MI.isBitcast() || MI.isRegSequenceLike() || MI.isInsertSubregLike() ||
    MI.isExtractSubregLike())
  return new UncoalescableRewriter(MI);

switch (MI.getOpcode()) {
default:
  return nullptr;
case TargetOpcode::COPY:
  return new CopyRewriter(MI);
case TargetOpcode::INSERT_SUBREG:
  return new InsertSubregRewriter(MI);
case TargetOpcode::EXTRACT_SUBREG:
  return new ExtractSubregRewriter(MI, TII);
case TargetOpcode::REG_SEQUENCE:
  return new RegSequenceRewriter(MI);
}
1122}

1124/// Given a \p Def.Reg and Def.SubReg  pair, use \p RewriteMap to find
1125/// the new source to use for rewrite. If \p HandleMultipleSources is true and
1126/// multiple sources for a given \p Def are found along the way, we found a
1127/// PHI instructions that needs to be rewritten.
1128/// TODO: HandleMultipleSources should be removed once we test PHI handling
1129/// with coalescable copies.
1130static RegSubRegPair
1131getNewSource(MachineRegisterInfo *MRI, const TargetInstrInfo *TII,
           RegSubRegPair Def,
           const PeepholeOptimizer::RewriteMapTy &RewriteMap,
           bool HandleMultipleSources = true) {
RegSubRegPair LookupSrc(Def.Reg, Def.SubReg);
while (true) {
  ValueTrackerResult Res = RewriteMap.lookup(LookupSrc);
  // If there are no entries on the map, LookupSrc is the new source.
  if (!Res.isValid())
    return LookupSrc;

  // There's only one source for this definition, keep searching...
  unsigned NumSrcs = Res.getNumSources();
  if (NumSrcs == 1) {
    LookupSrc.Reg = Res.getSrcReg(0);
    LookupSrc.SubReg = Res.getSrcSubReg(0);
    continue;
  }

  // TODO: Remove once multiple srcs w/ coalescable copies are supported.
  if (!HandleMultipleSources)
    break;

  // Multiple sources, recurse into each source to find a new source
  // for it. Then, rewrite the PHI accordingly to its new edges.
  SmallVector<RegSubRegPair, 4> NewPHISrcs;
  for (unsigned i = 0; i < NumSrcs; ++i) {
    RegSubRegPair PHISrc(Res.getSrcReg(i), Res.getSrcSubReg(i));
    NewPHISrcs.push_back(
        getNewSource(MRI, TII, PHISrc, RewriteMap, HandleMultipleSources));
  }

  // Build the new PHI node and return its def register as the new source.
  MachineInstr &OrigPHI = const_cast<MachineInstr &>(*Res.getInst());
  MachineInstr &NewPHI = insertPHI(*MRI, *TII, NewPHISrcs, OrigPHI);
  LLVM_DEBUG(dbgs() << "-- getNewSource\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "-- getNewSource\n"; } } while
 (false);
  LLVM_DEBUG(dbgs() << "   Replacing: " << OrigPHI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "   Replacing: " <<
 OrigPHI; } } while (false);
  LLVM_DEBUG(dbgs() << "        With: " << NewPHI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "        With: " <<
 NewPHI; } } while (false);
  const MachineOperand &MODef = NewPHI.getOperand(0);
  return RegSubRegPair(MODef.getReg(), MODef.getSubReg());
}

return RegSubRegPair(0, 0);
1174}

1176/// Optimize generic copy instructions to avoid cross register bank copy.
1177/// The optimization looks through a chain of copies and tries to find a source
1178/// that has a compatible register class.
1179/// Two register classes are considered to be compatible if they share the same
1180/// register bank.
1181/// New copies issued by this optimization are register allocator
1182/// friendly. This optimization does not remove any copy as it may
1183/// overconstrain the register allocator, but replaces some operands
1184/// when possible.
1185/// \pre isCoalescableCopy(*MI) is true.
1186/// \return True, when \p MI has been rewritten. False otherwise.
1187bool PeepholeOptimizer::optimizeCoalescableCopy(MachineInstr &MI) {
assert(isCoalescableCopy(MI) && "Invalid argument")(static_cast <bool> (isCoalescableCopy(MI) && "Invalid argument"
) ? void (0) : __assert_fail ("isCoalescableCopy(MI) && \"Invalid argument\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1188, __extension__
 __PRETTY_FUNCTION__));
assert(MI.getDesc().getNumDefs() == 1 &&(static_cast <bool> (MI.getDesc().getNumDefs() == 1 &&
 "Coalescer can understand multiple defs?!") ? void (0) : __assert_fail
 ("MI.getDesc().getNumDefs() == 1 && \"Coalescer can understand multiple defs?!\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1190, __extension__
 __PRETTY_FUNCTION__))
       "Coalescer can understand multiple defs?!")(static_cast <bool> (MI.getDesc().getNumDefs() == 1 &&
 "Coalescer can understand multiple defs?!") ? void (0) : __assert_fail
 ("MI.getDesc().getNumDefs() == 1 && \"Coalescer can understand multiple defs?!\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1190, __extension__
 __PRETTY_FUNCTION__));
const MachineOperand &MODef = MI.getOperand(0);
// Do not rewrite physical definitions.
if (Register::isPhysicalRegister(MODef.getReg()))
  return false;

bool Changed = false;
// Get the right rewriter for the current copy.
std::unique_ptr<Rewriter> CpyRewriter(getCopyRewriter(MI, *TII));
// If none exists, bail out.
if (!CpyRewriter)
  return false;
// Rewrite each rewritable source.
RegSubRegPair Src;
RegSubRegPair TrackPair;
while (CpyRewriter->getNextRewritableSource(Src, TrackPair)) {
  // Keep track of PHI nodes and its incoming edges when looking for sources.
  RewriteMapTy RewriteMap;
  // Try to find a more suitable source. If we failed to do so, or get the
  // actual source, move to the next source.
  if (!findNextSource(TrackPair, RewriteMap))
    continue;

  // Get the new source to rewrite. TODO: Only enable handling of multiple
  // sources (PHIs) once we have a motivating example and testcases for it.
  RegSubRegPair NewSrc = getNewSource(MRI, TII, TrackPair, RewriteMap,
                                      /*HandleMultipleSources=*/false);
  if (Src.Reg == NewSrc.Reg || NewSrc.Reg == 0)
    continue;

  // Rewrite source.
  if (CpyRewriter->RewriteCurrentSource(NewSrc.Reg, NewSrc.SubReg)) {
    // We may have extended the live-range of NewSrc, account for that.
    MRI->clearKillFlags(NewSrc.Reg);
    Changed = true;
  }
}
// TODO: We could have a clean-up method to tidy the instruction.
// E.g., v0 = INSERT_SUBREG v1, v1.sub0, sub0
// => v0 = COPY v1
// Currently we haven't seen motivating example for that and we
// want to avoid untested code.
NumRewrittenCopies += Changed;
return Changed;
1234}

1236/// Rewrite the source found through \p Def, by using the \p RewriteMap
1237/// and create a new COPY instruction. More info about RewriteMap in
1238/// PeepholeOptimizer::findNextSource. Right now this is only used to handle
1239/// Uncoalescable copies, since they are copy like instructions that aren't
1240/// recognized by the register allocator.
1241MachineInstr &
1242PeepholeOptimizer::rewriteSource(MachineInstr &CopyLike,
                               RegSubRegPair Def, RewriteMapTy &RewriteMap) {
assert(!Register::isPhysicalRegister(Def.Reg) &&(static_cast <bool> (!Register::isPhysicalRegister(Def.
Reg) && "We do not rewrite physical registers") ? void
 (0) : __assert_fail ("!Register::isPhysicalRegister(Def.Reg) && \"We do not rewrite physical registers\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1245, __extension__
 __PRETTY_FUNCTION__))
       "We do not rewrite physical registers")(static_cast <bool> (!Register::isPhysicalRegister(Def.
Reg) && "We do not rewrite physical registers") ? void
 (0) : __assert_fail ("!Register::isPhysicalRegister(Def.Reg) && \"We do not rewrite physical registers\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1245, __extension__
 __PRETTY_FUNCTION__));

// Find the new source to use in the COPY rewrite.
RegSubRegPair NewSrc = getNewSource(MRI, TII, Def, RewriteMap);

// Insert the COPY.
const TargetRegisterClass *DefRC = MRI->getRegClass(Def.Reg);
Register NewVReg = MRI->createVirtualRegister(DefRC);

MachineInstr *NewCopy =
    BuildMI(*CopyLike.getParent(), &CopyLike, CopyLike.getDebugLoc(),
            TII->get(TargetOpcode::COPY), NewVReg)
        .addReg(NewSrc.Reg, 0, NewSrc.SubReg);

if (Def.SubReg) {
  NewCopy->getOperand(0).setSubReg(Def.SubReg);
  NewCopy->getOperand(0).setIsUndef();
}

LLVM_DEBUG(dbgs() << "-- RewriteSource\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "-- RewriteSource\n"; } }
 while (false);
LLVM_DEBUG(dbgs() << "   Replacing: " << CopyLike)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "   Replacing: " <<
 CopyLike; } } while (false);
LLVM_DEBUG(dbgs() << "        With: " << *NewCopy)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "        With: " <<
 *NewCopy; } } while (false);
MRI->replaceRegWith(Def.Reg, NewVReg);
MRI->clearKillFlags(NewVReg);

// We extended the lifetime of NewSrc.Reg, clear the kill flags to
// account for that.
MRI->clearKillFlags(NewSrc.Reg);

return *NewCopy;
1275}

1277/// Optimize copy-like instructions to create
1278/// register coalescer friendly instruction.
1279/// The optimization tries to kill-off the \p MI by looking
1280/// through a chain of copies to find a source that has a compatible
1281/// register class.
1282/// If such a source is found, it replace \p MI by a generic COPY
1283/// operation.
1284/// \pre isUncoalescableCopy(*MI) is true.
1285/// \return True, when \p MI has been optimized. In that case, \p MI has
1286/// been removed from its parent.
1287/// All COPY instructions created, are inserted in \p LocalMIs.
1288bool PeepholeOptimizer::optimizeUncoalescableCopy(
  MachineInstr &MI, SmallPtrSetImpl<MachineInstr *> &LocalMIs) {
assert(isUncoalescableCopy(MI) && "Invalid argument")(static_cast <bool> (isUncoalescableCopy(MI) &&
 "Invalid argument") ? void (0) : __assert_fail ("isUncoalescableCopy(MI) && \"Invalid argument\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1290, __extension__
 __PRETTY_FUNCTION__));
UncoalescableRewriter CpyRewriter(MI);

// Rewrite each rewritable source by generating new COPYs. This works
// differently from optimizeCoalescableCopy since it first makes sure that all
// definitions can be rewritten.
RewriteMapTy RewriteMap;
RegSubRegPair Src;
RegSubRegPair Def;
SmallVector<RegSubRegPair, 4> RewritePairs;
while (CpyRewriter.getNextRewritableSource(Src, Def)) {
  // If a physical register is here, this is probably for a good reason.
  // Do not rewrite that.
  if (Register::isPhysicalRegister(Def.Reg))
    return false;

  // If we do not know how to rewrite this definition, there is no point
  // in trying to kill this instruction.
  if (!findNextSource(Def, RewriteMap))
    return false;

  RewritePairs.push_back(Def);
}

// The change is possible for all defs, do it.
for (const RegSubRegPair &Def : RewritePairs) {
  // Rewrite the "copy" in a way the register coalescer understands.
  MachineInstr &NewCopy = rewriteSource(MI, Def, RewriteMap);
  LocalMIs.insert(&NewCopy);
}

// MI is now dead.
LLVM_DEBUG(dbgs() << "Deleting uncoalescable copy: " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Deleting uncoalescable copy: "
 << MI; } } while (false);
MI.eraseFromParent();
++NumUncoalescableCopies;
return true;
1326}

1328/// Check whether MI is a candidate for folding into a later instruction.
1329/// We only fold loads to virtual registers and the virtual register defined
1330/// has a single user.
1331bool PeepholeOptimizer::isLoadFoldable(
  MachineInstr &MI, SmallSet<Register, 16> &FoldAsLoadDefCandidates) {
if (!MI.canFoldAsLoad() || !MI.mayLoad())
  return false;
const MCInstrDesc &MCID = MI.getDesc();
if (MCID.getNumDefs() != 1)
  return false;

Register Reg = MI.getOperand(0).getReg();
// To reduce compilation time, we check MRI->hasOneNonDBGUser when inserting
// loads. It should be checked when processing uses of the load, since
// uses can be removed during peephole.
if (Reg.isVirtual() && !MI.getOperand(0).getSubReg() &&
    MRI->hasOneNonDBGUser(Reg)) {
  FoldAsLoadDefCandidates.insert(Reg);
  return true;
}
return false;
1349}

1351bool PeepholeOptimizer::isMoveImmediate(
  MachineInstr &MI, SmallSet<Register, 4> &ImmDefRegs,
  DenseMap<Register, MachineInstr *> &ImmDefMIs) {
const MCInstrDesc &MCID = MI.getDesc();
if (!MI.isMoveImmediate())
  return false;
if (MCID.getNumDefs() != 1)
  return false;
Register Reg = MI.getOperand(0).getReg();
if (Reg.isVirtual()) {
  ImmDefMIs.insert(std::make_pair(Reg, &MI));
  ImmDefRegs.insert(Reg);
  return true;
}

return false;
1367}

1369/// Try folding register operands that are defined by move immediate
1370/// instructions, i.e. a trivial constant folding optimization, if
1371/// and only if the def and use are in the same BB.
1372bool PeepholeOptimizer::foldImmediate(
  MachineInstr &MI, SmallSet<Register, 4> &ImmDefRegs,
  DenseMap<Register, MachineInstr *> &ImmDefMIs) {
for (unsigned i = 0, e = MI.getDesc().getNumOperands(); i != e; ++i) {
  MachineOperand &MO = MI.getOperand(i);
  if (!MO.isReg() || MO.isDef())
    continue;
  Register Reg = MO.getReg();
  if (!Reg.isVirtual())
    continue;
  if (ImmDefRegs.count(Reg) == 0)
    continue;
  DenseMap<Register, MachineInstr *>::iterator II = ImmDefMIs.find(Reg);
  assert(II != ImmDefMIs.end() && "couldn't find immediate definition")(static_cast <bool> (II != ImmDefMIs.end() && "couldn't find immediate definition"
) ? void (0) : __assert_fail ("II != ImmDefMIs.end() && \"couldn't find immediate definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1385, __extension__
 __PRETTY_FUNCTION__));
  if (TII->FoldImmediate(MI, *II->second, Reg, MRI)) {
    ++NumImmFold;
    return true;
  }
}
return false;
1392}

1394// FIXME: This is very simple and misses some cases which should be handled when
1395// motivating examples are found.
1396//
1397// The copy rewriting logic should look at uses as well as defs and be able to
1398// eliminate copies across blocks.
1399//
1400// Later copies that are subregister extracts will also not be eliminated since
1401// only the first copy is considered.
1402//
1403// e.g.
1404// %1 = COPY %0
1405// %2 = COPY %0:sub1
1406//
1407// Should replace %2 uses with %1:sub1
1408bool PeepholeOptimizer::foldRedundantCopy(
  MachineInstr &MI, DenseMap<RegSubRegPair, MachineInstr *> &CopyMIs) {
assert(MI.isCopy() && "expected a COPY machine instruction")(static_cast <bool> (MI.isCopy() && "expected a COPY machine instruction"
) ? void (0) : __assert_fail ("MI.isCopy() && \"expected a COPY machine instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1410, __extension__
 __PRETTY_FUNCTION__));

Register SrcReg = MI.getOperand(1).getReg();
unsigned SrcSubReg = MI.getOperand(1).getSubReg();
if (!SrcReg.isVirtual())
  return false;

Register DstReg = MI.getOperand(0).getReg();
if (!DstReg.isVirtual())
  return false;

RegSubRegPair SrcPair(SrcReg, SrcSubReg);

if (CopyMIs.insert(std::make_pair(SrcPair, &MI)).second) {
  // First copy of this reg seen.
  return false;
}

MachineInstr *PrevCopy = CopyMIs.find(SrcPair)->second;

assert(SrcSubReg == PrevCopy->getOperand(1).getSubReg() &&(static_cast <bool> (SrcSubReg == PrevCopy->getOperand
(1).getSubReg() && "Unexpected mismatching subreg!") ?
 void (0) : __assert_fail ("SrcSubReg == PrevCopy->getOperand(1).getSubReg() && \"Unexpected mismatching subreg!\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1431, __extension__
 __PRETTY_FUNCTION__))
       "Unexpected mismatching subreg!")(static_cast <bool> (SrcSubReg == PrevCopy->getOperand
(1).getSubReg() && "Unexpected mismatching subreg!") ?
 void (0) : __assert_fail ("SrcSubReg == PrevCopy->getOperand(1).getSubReg() && \"Unexpected mismatching subreg!\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1431, __extension__
 __PRETTY_FUNCTION__));

Register PrevDstReg = PrevCopy->getOperand(0).getReg();

// Only replace if the copy register class is the same.
//
// TODO: If we have multiple copies to different register classes, we may want
// to track multiple copies of the same source register.
if (MRI->getRegClass(DstReg) != MRI->getRegClass(PrevDstReg))
  return false;

MRI->replaceRegWith(DstReg, PrevDstReg);

// Lifetime of the previous copy has been extended.
MRI->clearKillFlags(PrevDstReg);
return true;
1447}

1449bool PeepholeOptimizer::isNAPhysCopy(Register Reg) {
return Reg.isPhysical() && !MRI->isAllocatable(Reg);
1451}

1453bool PeepholeOptimizer::foldRedundantNAPhysCopy(
  MachineInstr &MI, DenseMap<Register, MachineInstr *> &NAPhysToVirtMIs) {
assert(MI.isCopy() && "expected a COPY machine instruction")(static_cast <bool> (MI.isCopy() && "expected a COPY machine instruction"
) ? void (0) : __assert_fail ("MI.isCopy() && \"expected a COPY machine instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1455, __extension__
 __PRETTY_FUNCTION__));

if (DisableNAPhysCopyOpt)
  return false;

Register DstReg = MI.getOperand(0).getReg();
Register SrcReg = MI.getOperand(1).getReg();
if (isNAPhysCopy(SrcReg) && Register::isVirtualRegister(DstReg)) {
  // %vreg = COPY $physreg
  // Avoid using a datastructure which can track multiple live non-allocatable
  // phys->virt copies since LLVM doesn't seem to do this.
  NAPhysToVirtMIs.insert({SrcReg, &MI});
  return false;
}

if (!(SrcReg.isVirtual() && isNAPhysCopy(DstReg)))
  return false;

// $physreg = COPY %vreg
auto PrevCopy = NAPhysToVirtMIs.find(DstReg);
if (PrevCopy == NAPhysToVirtMIs.end()) {
  // We can't remove the copy: there was an intervening clobber of the
  // non-allocatable physical register after the copy to virtual.
  LLVM_DEBUG(dbgs() << "NAPhysCopy: intervening clobber forbids erasing "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: intervening clobber forbids erasing "
 << MI; } } while (false)
                    << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: intervening clobber forbids erasing "
 << MI; } } while (false);
  return false;
}

Register PrevDstReg = PrevCopy->second->getOperand(0).getReg();
if (PrevDstReg == SrcReg) {
  // Remove the virt->phys copy: we saw the virtual register definition, and
  // the non-allocatable physical register's state hasn't changed since then.
  LLVM_DEBUG(dbgs() << "NAPhysCopy: erasing " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: erasing " <<
 MI; } } while (false);
  ++NumNAPhysCopies;
  return true;
}

// Potential missed optimization opportunity: we saw a different virtual
// register get a copy of the non-allocatable physical register, and we only
// track one such copy. Avoid getting confused by this new non-allocatable
// physical register definition, and remove it from the tracked copies.
LLVM_DEBUG(dbgs() << "NAPhysCopy: missed opportunity " << MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: missed opportunity "
 << MI; } } while (false);
NAPhysToVirtMIs.erase(PrevCopy);
return false;
1499}

1501/// \bried Returns true if \p MO is a virtual register operand.
1502static bool isVirtualRegisterOperand(MachineOperand &MO) {
return MO.isReg() && MO.getReg().isVirtual();
1504}

1506bool PeepholeOptimizer::findTargetRecurrence(
  Register Reg, const SmallSet<Register, 2> &TargetRegs,
  RecurrenceCycle &RC) {
// Recurrence found if Reg is in TargetRegs.
if (TargetRegs.count(Reg))
  return true;

// TODO: Curerntly, we only allow the last instruction of the recurrence
// cycle (the instruction that feeds the PHI instruction) to have more than
// one uses to guarantee that commuting operands does not tie registers
// with overlapping live range. Once we have actual live range info of
// each register, this constraint can be relaxed.
if (!MRI->hasOneNonDBGUse(Reg))
  return false;

// Give up if the reccurrence chain length is longer than the limit.
if (RC.size() >= MaxRecurrenceChain)
  return false;

MachineInstr &MI = *(MRI->use_instr_nodbg_begin(Reg));
unsigned Idx = MI.findRegisterUseOperandIdx(Reg);

// Only interested in recurrences whose instructions have only one def, which
// is a virtual register.
if (MI.getDesc().getNumDefs() != 1)
  return false;

MachineOperand &DefOp = MI.getOperand(0);
if (!isVirtualRegisterOperand(DefOp))
  return false;

// Check if def operand of MI is tied to any use operand. We are only
// interested in the case that all the instructions in the recurrence chain
// have there def operand tied with one of the use operand.
unsigned TiedUseIdx;
if (!MI.isRegTiedToUseOperand(0, &TiedUseIdx))
  return false;

if (Idx == TiedUseIdx) {
  RC.push_back(RecurrenceInstr(&MI));
  return findTargetRecurrence(DefOp.getReg(), TargetRegs, RC);
} else {
  // If Idx is not TiedUseIdx, check if Idx is commutable with TiedUseIdx.
  unsigned CommIdx = TargetInstrInfo::CommuteAnyOperandIndex;
  if (TII->findCommutedOpIndices(MI, Idx, CommIdx) && CommIdx == TiedUseIdx) {
    RC.push_back(RecurrenceInstr(&MI, Idx, CommIdx));
    return findTargetRecurrence(DefOp.getReg(), TargetRegs, RC);
  }
}

return false;
1557}

1559/// Phi instructions will eventually be lowered to copy instructions.
1560/// If phi is in a loop header, a recurrence may formulated around the source
1561/// and destination of the phi. For such case commuting operands of the
1562/// instructions in the recurrence may enable coalescing of the copy instruction
1563/// generated from the phi. For example, if there is a recurrence of
1564///
1565/// LoopHeader:
1566///   %1 = phi(%0, %100)
1567/// LoopLatch:
1568///   %0<def, tied1> = ADD %2<def, tied0>, %1
1569///
1570/// , the fact that %0 and %2 are in the same tied operands set makes
1571/// the coalescing of copy instruction generated from the phi in
1572/// LoopHeader(i.e. %1 = COPY %0) impossible, because %1 and
1573/// %2 have overlapping live range. This introduces additional move
1574/// instruction to the final assembly. However, if we commute %2 and
1575/// %1 of ADD instruction, the redundant move instruction can be
1576/// avoided.
1577bool PeepholeOptimizer::optimizeRecurrence(MachineInstr &PHI) {
SmallSet<Register, 2> TargetRegs;
for (unsigned Idx = 1; Idx < PHI.getNumOperands(); Idx += 2) {
  MachineOperand &MO = PHI.getOperand(Idx);
  assert(isVirtualRegisterOperand(MO) && "Invalid PHI instruction")(static_cast <bool> (isVirtualRegisterOperand(MO) &&
 "Invalid PHI instruction") ? void (0) : __assert_fail ("isVirtualRegisterOperand(MO) && \"Invalid PHI instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1581, __extension__
 __PRETTY_FUNCTION__));
  TargetRegs.insert(MO.getReg());
}

bool Changed = false;
RecurrenceCycle RC;
if (findTargetRecurrence(PHI.getOperand(0).getReg(), TargetRegs, RC)) {
  // Commutes operands of instructions in RC if necessary so that the copy to
  // be generated from PHI can be coalesced.
  LLVM_DEBUG(dbgs() << "Optimize recurrence chain from " << PHI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Optimize recurrence chain from "
 << PHI; } } while (false);
  for (auto &RI : RC) {
    LLVM_DEBUG(dbgs() << "\tInst: " << *(RI.getMI()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "\tInst: " << *(RI.
getMI()); } } while (false);
    auto CP = RI.getCommutePair();
    if (CP) {
      Changed = true;
      TII->commuteInstruction(*(RI.getMI()), false, (*CP).first,
                              (*CP).second);
      LLVM_DEBUG(dbgs() << "\t\tCommuted: " << *(RI.getMI()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "\t\tCommuted: " <<
 *(RI.getMI()); } } while (false);
    }
  }
}

return Changed;
1604}

1606bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
if (skipFunction(MF.getFunction()))
1
Assuming the condition is false→
  return false;

LLVM_DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "********** PEEPHOLE OPTIMIZER **********\n"
; } } while (false);
2
←
Taking false branch→
3
←
Assuming 'DebugFlag' is false→
LLVM_DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "********** Function: " <<
 MF.getName() << '\n'; } } while (false);
4
←
Loop condition is false.  Exiting loop→
5
←
Loop condition is false.  Exiting loop→

if (DisablePeephole)
6
←
Assuming the condition is false→
7
←
Taking false branch→
  return false;

TII = MF.getSubtarget().getInstrInfo();
TRI = MF.getSubtarget().getRegisterInfo();
MRI = &MF.getRegInfo();
DT  = Aggressive ? &getAnalysis<MachineDominatorTree>() : nullptr;
8
←
Assuming the condition is false→
9
←
'?' condition is false→
10
←
Null pointer value stored to field 'DT'→
MLI = &getAnalysis<MachineLoopInfo>();

bool Changed = false;

for (MachineBasicBlock &MBB : MF) {
  bool SeenMoveImm = false;

  // During this forward scan, at some point it needs to answer the question
  // "given a pointer to an MI in the current BB, is it located before or
  // after the current instruction".
  // To perform this, the following set keeps track of the MIs already seen
  // during the scan, if a MI is not in the set, it is assumed to be located
  // after. Newly created MIs have to be inserted in the set as well.
  SmallPtrSet<MachineInstr*, 16> LocalMIs;
  SmallSet<Register, 4> ImmDefRegs;
  DenseMap<Register, MachineInstr *> ImmDefMIs;
  SmallSet<Register, 16> FoldAsLoadDefCandidates;

  // Track when a non-allocatable physical register is copied to a virtual
  // register so that useless moves can be removed.
  //
  // $physreg is the map index; MI is the last valid `%vreg = COPY $physreg`
  // without any intervening re-definition of $physreg.
  DenseMap<Register, MachineInstr *> NAPhysToVirtMIs;

  // Set of pairs of virtual registers and their subregs that are copied
  // from.
  DenseMap<RegSubRegPair, MachineInstr *> CopySrcMIs;

  bool IsLoopHeader = MLI->isLoopHeader(&MBB);

  for (MachineBasicBlock::iterator MII = MBB.begin(), MIE = MBB.end();
11
←
Loop condition is true.  Entering loop body→
       MII != MIE; ) {
    MachineInstr *MI = &*MII;
    // We may be erasing MI below, increment MII now.
    ++MII;
    LocalMIs.insert(MI);

    // Skip debug instructions. They should not affect this peephole
    // optimization.
    if (MI->isDebugInstr())
12
←
Taking false branch→
      continue;

    if (MI->isPosition())
      continue;

    if (IsLoopHeader && MI->isPHI()) {
13
←
Assuming 'IsLoopHeader' is false→
      if (optimizeRecurrence(*MI)) {
        Changed = true;
        continue;
      }
    }

    if (!MI->isCopy()) {
14
←
Taking true branch→
      for (const MachineOperand &MO : MI->operands()) {
15
←
Assuming '__begin4' is equal to '__end4'→
        // Visit all operands: definitions can be implicit or explicit.
        if (MO.isReg()) {
          Register Reg = MO.getReg();
          if (MO.isDef() && isNAPhysCopy(Reg)) {
            const auto &Def = NAPhysToVirtMIs.find(Reg);
            if (Def != NAPhysToVirtMIs.end()) {
              // A new definition of the non-allocatable physical register
              // invalidates previous copies.
              LLVM_DEBUG(dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: invalidating because of "
 << *MI; } } while (false)
                         << "NAPhysCopy: invalidating because of " << *MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: invalidating because of "
 << *MI; } } while (false);
              NAPhysToVirtMIs.erase(Def);
            }
          }
        } else if (MO.isRegMask()) {
          const uint32_t *RegMask = MO.getRegMask();
          for (auto &RegMI : NAPhysToVirtMIs) {
            Register Def = RegMI.first;
            if (MachineOperand::clobbersPhysReg(RegMask, Def)) {
              LLVM_DEBUG(dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: invalidating because of "
 << *MI; } } while (false)
                         << "NAPhysCopy: invalidating because of " << *MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: invalidating because of "
 << *MI; } } while (false);
              NAPhysToVirtMIs.erase(Def);
            }
          }
        }
      }
    }

    if (MI->isImplicitDef() || MI->isKill())
      continue;

    if (MI->isInlineAsm() || MI->hasUnmodeledSideEffects()) {
16
←
Assuming the condition is false→
      // Blow away all non-allocatable physical registers knowledge since we
      // don't know what's correct anymore.
      //
      // FIXME: handle explicit asm clobbers.
      LLVM_DEBUG(dbgs() << "NAPhysCopy: blowing away all info due to "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: blowing away all info due to "
 << *MI; } } while (false)
                        << *MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "NAPhysCopy: blowing away all info due to "
 << *MI; } } while (false);
      NAPhysToVirtMIs.clear();
    }

    if ((isUncoalescableCopy(*MI) &&
         optimizeUncoalescableCopy(*MI, LocalMIs)) ||
        (MI->isCompare() && optimizeCmpInstr(*MI)) ||
17
←
Assuming the condition is false→
        (MI->isSelect() && optimizeSelect(*MI, LocalMIs))) {
18
←
Assuming the condition is false→
      // MI is deleted.
      LocalMIs.erase(MI);
      Changed = true;
      continue;
    }

    if (MI->isConditionalBranch() && optimizeCondBranch(*MI)) {
      Changed = true;
      continue;
    }

    if (isCoalescableCopy(*MI) && optimizeCoalescableCopy(*MI)) {
      // MI is just rewritten.
      Changed = true;
      continue;
    }

    if (MI->isCopy() && (foldRedundantCopy(*MI, CopySrcMIs) ||
                         foldRedundantNAPhysCopy(*MI, NAPhysToVirtMIs))) {
      LocalMIs.erase(MI);
      LLVM_DEBUG(dbgs() << "Deleting redundant copy: " << *MI << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Deleting redundant copy: "
 << *MI << "\n"; } } while (false);
      MI->eraseFromParent();
      Changed = true;
      continue;
    }

    if (isMoveImmediate(*MI, ImmDefRegs, ImmDefMIs)) {
19
←
Taking false branch→
      SeenMoveImm = true;
    } else {
      Changed |= optimizeExtInstr(*MI, MBB, LocalMIs);
20
←
Calling 'PeepholeOptimizer::optimizeExtInstr'→
      // optimizeExtInstr might have created new instructions after MI
      // and before the already incremented MII. Adjust MII so that the
      // next iteration sees the new instructions.
      MII = MI;
      ++MII;
      if (SeenMoveImm)
        Changed |= foldImmediate(*MI, ImmDefRegs, ImmDefMIs);
    }

    // Check whether MI is a load candidate for folding into a later
    // instruction. If MI is not a candidate, check whether we can fold an
    // earlier load into MI.
    if (!isLoadFoldable(*MI, FoldAsLoadDefCandidates) &&
        !FoldAsLoadDefCandidates.empty()) {

      // We visit each operand even after successfully folding a previous
      // one.  This allows us to fold multiple loads into a single
      // instruction.  We do assume that optimizeLoadInstr doesn't insert
      // foldable uses earlier in the argument list.  Since we don't restart
      // iteration, we'd miss such cases.
      const MCInstrDesc &MIDesc = MI->getDesc();
      for (unsigned i = MIDesc.getNumDefs(); i != MI->getNumOperands();
           ++i) {
        const MachineOperand &MOp = MI->getOperand(i);
        if (!MOp.isReg())
          continue;
        Register FoldAsLoadDefReg = MOp.getReg();
        if (FoldAsLoadDefCandidates.count(FoldAsLoadDefReg)) {
          // We need to fold load after optimizeCmpInstr, since
          // optimizeCmpInstr can enable folding by converting SUB to CMP.
          // Save FoldAsLoadDefReg because optimizeLoadInstr() resets it and
          // we need it for markUsesInDebugValueAsUndef().
          Register FoldedReg = FoldAsLoadDefReg;
          MachineInstr *DefMI = nullptr;
          if (MachineInstr *FoldMI =
                  TII->optimizeLoadInstr(*MI, MRI, FoldAsLoadDefReg, DefMI)) {
            // Update LocalMIs since we replaced MI with FoldMI and deleted
            // DefMI.
            LLVM_DEBUG(dbgs() << "Replacing: " << *MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Replacing: " << *MI
; } } while (false);
            LLVM_DEBUG(dbgs() << "     With: " << *FoldMI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "     With: " << *FoldMI
; } } while (false);
            LocalMIs.erase(MI);
            LocalMIs.erase(DefMI);
            LocalMIs.insert(FoldMI);
            // Update the call site info.
            if (MI->shouldUpdateCallSiteInfo())
              MI->getMF()->moveCallSiteInfo(MI, FoldMI);
            MI->eraseFromParent();
            DefMI->eraseFromParent();
            MRI->markUsesInDebugValueAsUndef(FoldedReg);
            FoldAsLoadDefCandidates.erase(FoldedReg);
            ++NumLoadFold;

            // MI is replaced with FoldMI so we can continue trying to fold
            Changed = true;
            MI = FoldMI;
          }
        }
      }
    }

    // If we run into an instruction we can't fold across, discard
    // the load candidates.  Note: We might be able to fold *into* this
    // instruction, so this needs to be after the folding logic.
    if (MI->isLoadFoldBarrier()) {
      LLVM_DEBUG(dbgs() << "Encountered load fold barrier on " << *MI)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("peephole-opt")) { dbgs() << "Encountered load fold barrier on "
 << *MI; } } while (false);
      FoldAsLoadDefCandidates.clear();
    }
  }
}

return Changed;
1820}

1822ValueTrackerResult ValueTracker::getNextSourceFromCopy() {
assert(Def->isCopy() && "Invalid definition")(static_cast <bool> (Def->isCopy() && "Invalid definition"
) ? void (0) : __assert_fail ("Def->isCopy() && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1823, __extension__
 __PRETTY_FUNCTION__));
// Copy instruction are supposed to be: Def = Src.
// If someone breaks this assumption, bad things will happen everywhere.
// There may be implicit uses preventing the copy to be moved across
// some target specific register definitions
assert(Def->getNumOperands() - Def->getNumImplicitOperands() == 2 &&(static_cast <bool> (Def->getNumOperands() - Def->
getNumImplicitOperands() == 2 && "Invalid number of operands"
) ? void (0) : __assert_fail ("Def->getNumOperands() - Def->getNumImplicitOperands() == 2 && \"Invalid number of operands\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1829, __extension__
 __PRETTY_FUNCTION__))
       "Invalid number of operands")(static_cast <bool> (Def->getNumOperands() - Def->
getNumImplicitOperands() == 2 && "Invalid number of operands"
) ? void (0) : __assert_fail ("Def->getNumOperands() - Def->getNumImplicitOperands() == 2 && \"Invalid number of operands\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1829, __extension__
 __PRETTY_FUNCTION__));
assert(!Def->hasImplicitDef() && "Only implicit uses are allowed")(static_cast <bool> (!Def->hasImplicitDef() &&
 "Only implicit uses are allowed") ? void (0) : __assert_fail
 ("!Def->hasImplicitDef() && \"Only implicit uses are allowed\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1830, __extension__
 __PRETTY_FUNCTION__));

if (Def->getOperand(DefIdx).getSubReg() != DefSubReg)
  // If we look for a different subreg, it means we want a subreg of src.
  // Bails as we do not support composing subregs yet.
  return ValueTrackerResult();
// Otherwise, we want the whole source.
const MachineOperand &Src = Def->getOperand(1);
if (Src.isUndef())
  return ValueTrackerResult();
return ValueTrackerResult(Src.getReg(), Src.getSubReg());
1841}

1843ValueTrackerResult ValueTracker::getNextSourceFromBitcast() {
assert(Def->isBitcast() && "Invalid definition")(static_cast <bool> (Def->isBitcast() && "Invalid definition"
) ? void (0) : __assert_fail ("Def->isBitcast() && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1844, __extension__
 __PRETTY_FUNCTION__));

// Bail if there are effects that a plain copy will not expose.
if (Def->mayRaiseFPException() || Def->hasUnmodeledSideEffects())
  return ValueTrackerResult();

// Bitcasts with more than one def are not supported.
if (Def->getDesc().getNumDefs() != 1)
  return ValueTrackerResult();
const MachineOperand DefOp = Def->getOperand(DefIdx);
if (DefOp.getSubReg() != DefSubReg)
  // If we look for a different subreg, it means we want a subreg of the src.
  // Bails as we do not support composing subregs yet.
  return ValueTrackerResult();

unsigned SrcIdx = Def->getNumOperands();
for (unsigned OpIdx = DefIdx + 1, EndOpIdx = SrcIdx; OpIdx != EndOpIdx;
     ++OpIdx) {
  const MachineOperand &MO = Def->getOperand(OpIdx);
  if (!MO.isReg() || !MO.getReg())
    continue;
  // Ignore dead implicit defs.
  if (MO.isImplicit() && MO.isDead())
    continue;
  assert(!MO.isDef() && "We should have skipped all the definitions by now")(static_cast <bool> (!MO.isDef() && "We should have skipped all the definitions by now"
) ? void (0) : __assert_fail ("!MO.isDef() && \"We should have skipped all the definitions by now\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1868, __extension__
 __PRETTY_FUNCTION__));
  if (SrcIdx != EndOpIdx)
    // Multiple sources?
    return ValueTrackerResult();
  SrcIdx = OpIdx;
}

// In some rare case, Def has no input, SrcIdx is out of bound,
// getOperand(SrcIdx) will fail below.
if (SrcIdx >= Def->getNumOperands())
  return ValueTrackerResult();

// Stop when any user of the bitcast is a SUBREG_TO_REG, replacing with a COPY
// will break the assumed guarantees for the upper bits.
for (const MachineInstr &UseMI : MRI.use_nodbg_instructions(DefOp.getReg())) {
  if (UseMI.isSubregToReg())
    return ValueTrackerResult();
}

const MachineOperand &Src = Def->getOperand(SrcIdx);
if (Src.isUndef())
  return ValueTrackerResult();
return ValueTrackerResult(Src.getReg(), Src.getSubReg());
1891}

1893ValueTrackerResult ValueTracker::getNextSourceFromRegSequence() {
assert((Def->isRegSequence() || Def->isRegSequenceLike()) &&(static_cast <bool> ((Def->isRegSequence() || Def->
isRegSequenceLike()) && "Invalid definition") ? void (
0) : __assert_fail ("(Def->isRegSequence() || Def->isRegSequenceLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1895, __extension__
 __PRETTY_FUNCTION__))
       "Invalid definition")(static_cast <bool> ((Def->isRegSequence() || Def->
isRegSequenceLike()) && "Invalid definition") ? void (
0) : __assert_fail ("(Def->isRegSequence() || Def->isRegSequenceLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1895, __extension__
 __PRETTY_FUNCTION__));

if (Def->getOperand(DefIdx).getSubReg())
  // If we are composing subregs, bail out.
  // The case we are checking is Def.<subreg> = REG_SEQUENCE.
  // This should almost never happen as the SSA property is tracked at
  // the register level (as opposed to the subreg level).
  // I.e.,
  // Def.sub0 =
  // Def.sub1 =
  // is a valid SSA representation for Def.sub0 and Def.sub1, but not for
  // Def. Thus, it must not be generated.
  // However, some code could theoretically generates a single
  // Def.sub0 (i.e, not defining the other subregs) and we would
  // have this case.
  // If we can ascertain (or force) that this never happens, we could
  // turn that into an assertion.
  return ValueTrackerResult();

if (!TII)
  // We could handle the REG_SEQUENCE here, but we do not want to
  // duplicate the code from the generic TII.
  return ValueTrackerResult();

SmallVector<RegSubRegPairAndIdx, 8> RegSeqInputRegs;
if (!TII->getRegSequenceInputs(*Def, DefIdx, RegSeqInputRegs))
  return ValueTrackerResult();

// We are looking at:
// Def = REG_SEQUENCE v0, sub0, v1, sub1, ...
// Check if one of the operand defines the subreg we are interested in.
for (const RegSubRegPairAndIdx &RegSeqInput : RegSeqInputRegs) {
  if (RegSeqInput.SubIdx == DefSubReg)
    return ValueTrackerResult(RegSeqInput.Reg, RegSeqInput.SubReg);
}

// If the subreg we are tracking is super-defined by another subreg,
// we could follow this value. However, this would require to compose
// the subreg and we do not do that for now.
return ValueTrackerResult();
1935}

1937ValueTrackerResult ValueTracker::getNextSourceFromInsertSubreg() {
assert((Def->isInsertSubreg() || Def->isInsertSubregLike()) &&(static_cast <bool> ((Def->isInsertSubreg() || Def->
isInsertSubregLike()) && "Invalid definition") ? void
 (0) : __assert_fail ("(Def->isInsertSubreg() || Def->isInsertSubregLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1939, __extension__
 __PRETTY_FUNCTION__))
       "Invalid definition")(static_cast <bool> ((Def->isInsertSubreg() || Def->
isInsertSubregLike()) && "Invalid definition") ? void
 (0) : __assert_fail ("(Def->isInsertSubreg() || Def->isInsertSubregLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1939, __extension__
 __PRETTY_FUNCTION__));

if (Def->getOperand(DefIdx).getSubReg())
  // If we are composing subreg, bail out.
  // Same remark as getNextSourceFromRegSequence.
  // I.e., this may be turned into an assert.
  return ValueTrackerResult();

if (!TII)
  // We could handle the REG_SEQUENCE here, but we do not want to
  // duplicate the code from the generic TII.
  return ValueTrackerResult();

RegSubRegPair BaseReg;
RegSubRegPairAndIdx InsertedReg;
if (!TII->getInsertSubregInputs(*Def, DefIdx, BaseReg, InsertedReg))
  return ValueTrackerResult();

// We are looking at:
// Def = INSERT_SUBREG v0, v1, sub1
// There are two cases:
// 1. DefSubReg == sub1, get v1.
// 2. DefSubReg != sub1, the value may be available through v0.

// #1 Check if the inserted register matches the required sub index.
if (InsertedReg.SubIdx == DefSubReg) {
  return ValueTrackerResult(InsertedReg.Reg, InsertedReg.SubReg);
}
// #2 Otherwise, if the sub register we are looking for is not partial
// defined by the inserted element, we can look through the main
// register (v0).
const MachineOperand &MODef = Def->getOperand(DefIdx);
// If the result register (Def) and the base register (v0) do not
// have the same register class or if we have to compose
// subregisters, bail out.
if (MRI.getRegClass(MODef.getReg()) != MRI.getRegClass(BaseReg.Reg) ||
    BaseReg.SubReg)
  return ValueTrackerResult();

// Get the TRI and check if the inserted sub-register overlaps with the
// sub-register we are tracking.
const TargetRegisterInfo *TRI = MRI.getTargetRegisterInfo();
if (!TRI ||
    !(TRI->getSubRegIndexLaneMask(DefSubReg) &
      TRI->getSubRegIndexLaneMask(InsertedReg.SubIdx)).none())
  return ValueTrackerResult();
// At this point, the value is available in v0 via the same subreg
// we used for Def.
return ValueTrackerResult(BaseReg.Reg, DefSubReg);
1988}

1990ValueTrackerResult ValueTracker::getNextSourceFromExtractSubreg() {
assert((Def->isExtractSubreg() ||(static_cast <bool> ((Def->isExtractSubreg() || Def->
isExtractSubregLike()) && "Invalid definition") ? void
 (0) : __assert_fail ("(Def->isExtractSubreg() || Def->isExtractSubregLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1992, __extension__
 __PRETTY_FUNCTION__))
        Def->isExtractSubregLike()) && "Invalid definition")(static_cast <bool> ((Def->isExtractSubreg() || Def->
isExtractSubregLike()) && "Invalid definition") ? void
 (0) : __assert_fail ("(Def->isExtractSubreg() || Def->isExtractSubregLike()) && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 1992, __extension__
 __PRETTY_FUNCTION__));
// We are looking at:
// Def = EXTRACT_SUBREG v0, sub0

// Bail if we have to compose sub registers.
// Indeed, if DefSubReg != 0, we would have to compose it with sub0.
if (DefSubReg)
  return ValueTrackerResult();

if (!TII)
  // We could handle the EXTRACT_SUBREG here, but we do not want to
  // duplicate the code from the generic TII.
  return ValueTrackerResult();

RegSubRegPairAndIdx ExtractSubregInputReg;
if (!TII->getExtractSubregInputs(*Def, DefIdx, ExtractSubregInputReg))
  return ValueTrackerResult();

// Bail if we have to compose sub registers.
// Likewise, if v0.subreg != 0, we would have to compose v0.subreg with sub0.
if (ExtractSubregInputReg.SubReg)
  return ValueTrackerResult();
// Otherwise, the value is available in the v0.sub0.
return ValueTrackerResult(ExtractSubregInputReg.Reg,
                          ExtractSubregInputReg.SubIdx);
2017}

2019ValueTrackerResult ValueTracker::getNextSourceFromSubregToReg() {
assert(Def->isSubregToReg() && "Invalid definition")(static_cast <bool> (Def->isSubregToReg() &&
 "Invalid definition") ? void (0) : __assert_fail ("Def->isSubregToReg() && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2020, __extension__
 __PRETTY_FUNCTION__));
// We are looking at:
// Def = SUBREG_TO_REG Imm, v0, sub0

// Bail if we have to compose sub registers.
// If DefSubReg != sub0, we would have to check that all the bits
// we track are included in sub0 and if yes, we would have to
// determine the right subreg in v0.
if (DefSubReg != Def->getOperand(3).getImm())
  return ValueTrackerResult();
// Bail if we have to compose sub registers.
// Likewise, if v0.subreg != 0, we would have to compose it with sub0.
if (Def->getOperand(2).getSubReg())
  return ValueTrackerResult();

return ValueTrackerResult(Def->getOperand(2).getReg(),
                          Def->getOperand(3).getImm());
2037}

2039/// Explore each PHI incoming operand and return its sources.
2040ValueTrackerResult ValueTracker::getNextSourceFromPHI() {
assert(Def->isPHI() && "Invalid definition")(static_cast <bool> (Def->isPHI() && "Invalid definition"
) ? void (0) : __assert_fail ("Def->isPHI() && \"Invalid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2041, __extension__
 __PRETTY_FUNCTION__));
ValueTrackerResult Res;

// If we look for a different subreg, bail as we do not support composing
// subregs yet.
if (Def->getOperand(0).getSubReg() != DefSubReg)
  return ValueTrackerResult();

// Return all register sources for PHI instructions.
for (unsigned i = 1, e = Def->getNumOperands(); i < e; i += 2) {
  const MachineOperand &MO = Def->getOperand(i);
  assert(MO.isReg() && "Invalid PHI instruction")(static_cast <bool> (MO.isReg() && "Invalid PHI instruction"
) ? void (0) : __assert_fail ("MO.isReg() && \"Invalid PHI instruction\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2052, __extension__
 __PRETTY_FUNCTION__));
  // We have no code to deal with undef operands. They shouldn't happen in
  // normal programs anyway.
  if (MO.isUndef())
    return ValueTrackerResult();
  Res.addSource(MO.getReg(), MO.getSubReg());
}

return Res;
2061}

2063ValueTrackerResult ValueTracker::getNextSourceImpl() {
assert(Def && "This method needs a valid definition")(static_cast <bool> (Def && "This method needs a valid definition"
) ? void (0) : __assert_fail ("Def && \"This method needs a valid definition\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2064, __extension__
 __PRETTY_FUNCTION__));

assert(((Def->getOperand(DefIdx).isDef() &&(static_cast <bool> (((Def->getOperand(DefIdx).isDef
() && (DefIdx < Def->getDesc().getNumDefs() || Def
->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit
()) && "Invalid DefIdx") ? void (0) : __assert_fail (
"((Def->getOperand(DefIdx).isDef() && (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit()) && \"Invalid DefIdx\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2070, __extension__
 __PRETTY_FUNCTION__))
         (DefIdx < Def->getDesc().getNumDefs() ||(static_cast <bool> (((Def->getOperand(DefIdx).isDef
() && (DefIdx < Def->getDesc().getNumDefs() || Def
->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit
()) && "Invalid DefIdx") ? void (0) : __assert_fail (
"((Def->getOperand(DefIdx).isDef() && (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit()) && \"Invalid DefIdx\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2070, __extension__
 __PRETTY_FUNCTION__))
          Def->getDesc().isVariadic())) ||(static_cast <bool> (((Def->getOperand(DefIdx).isDef
() && (DefIdx < Def->getDesc().getNumDefs() || Def
->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit
()) && "Invalid DefIdx") ? void (0) : __assert_fail (
"((Def->getOperand(DefIdx).isDef() && (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit()) && \"Invalid DefIdx\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2070, __extension__
 __PRETTY_FUNCTION__))
        Def->getOperand(DefIdx).isImplicit()) &&(static_cast <bool> (((Def->getOperand(DefIdx).isDef
() && (DefIdx < Def->getDesc().getNumDefs() || Def
->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit
()) && "Invalid DefIdx") ? void (0) : __assert_fail (
"((Def->getOperand(DefIdx).isDef() && (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit()) && \"Invalid DefIdx\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2070, __extension__
 __PRETTY_FUNCTION__))
       "Invalid DefIdx")(static_cast <bool> (((Def->getOperand(DefIdx).isDef
() && (DefIdx < Def->getDesc().getNumDefs() || Def
->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit
()) && "Invalid DefIdx") ? void (0) : __assert_fail (
"((Def->getOperand(DefIdx).isDef() && (DefIdx < Def->getDesc().getNumDefs() || Def->getDesc().isVariadic())) || Def->getOperand(DefIdx).isImplicit()) && \"Invalid DefIdx\""
, "llvm/lib/CodeGen/PeepholeOptimizer.cpp", 2070, __extension__
 __PRETTY_FUNCTION__));
if (Def->isCopy())
  return getNextSourceFromCopy();
if (Def->isBitcast())
  return getNextSourceFromBitcast();
// All the remaining cases involve "complex" instructions.
// Bail if we did not ask for the advanced tracking.
if (DisableAdvCopyOpt)
  return ValueTrackerResult();
if (Def->isRegSequence() || Def->isRegSequenceLike())
  return getNextSourceFromRegSequence();
if (Def->isInsertSubreg() || Def->isInsertSubregLike())
  return getNextSourceFromInsertSubreg();
if (Def->isExtractSubreg() || Def->isExtractSubregLike())
  return getNextSourceFromExtractSubreg();
if (Def->isSubregToReg())
  return getNextSourceFromSubregToReg();
if (Def->isPHI())
  return getNextSourceFromPHI();
return ValueTrackerResult();
2090}

2092ValueTrackerResult ValueTracker::getNextSource() {
// If we reach a point where we cannot move up in the use-def chain,
// there is nothing we can get.
if (!Def)
  return ValueTrackerResult();

ValueTrackerResult Res = getNextSourceImpl();
if (Res.isValid()) {
  // Update definition, definition index, and subregister for the
  // next call of getNextSource.
  // Update the current register.
  bool OneRegSrc = Res.getNumSources() == 1;
  if (OneRegSrc)
    Reg = Res.getSrcReg(0);
  // Update the result before moving up in the use-def chain
  // with the instruction containing the last found sources.
  Res.setInst(Def);

  // If we can still move up in the use-def chain, move to the next
  // definition.
  if (!Register::isPhysicalRegister(Reg) && OneRegSrc) {
    MachineRegisterInfo::def_iterator DI = MRI.def_begin(Reg);
    if (DI != MRI.def_end()) {
      Def = DI->getParent();
      DefIdx = DI.getOperandNo();
      DefSubReg = Res.getSrcSubReg(0);
    } else {
      Def = nullptr;
    }
    return Res;
  }
}
// If we end up here, this means we will not be able to find another source
// for the next iteration. Make sure any new call to getNextSource bails out
// early by cutting the use-def chain.
Def = nullptr;
return Res;
2129}