Bug Summary

File:lib/Transforms/Scalar/ConstantHoisting.cpp
Warning:line 325, column 25
Called C++ object pointer is null

Annotated Source Code

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clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name ConstantHoisting.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-eagerly-assume -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-7/lib/clang/7.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/include -I /build/llvm-toolchain-snapshot-7~svn338205/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/x86_64-linux-gnu/c++/8 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/8/../../../../include/c++/8/backward -internal-isystem /usr/include/clang/7.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-7/lib/clang/7.0.0/include -internal-externc-isystem /usr/lib/gcc/x86_64-linux-gnu/8/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-class-memaccess -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-7~svn338205/build-llvm/lib/Transforms/Scalar -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-07-29-043837-17923-1 -x c++ /build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp -faddrsig
1//===- ConstantHoisting.cpp - Prepare code for expensive constants --------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This pass identifies expensive constants to hoist and coalesces them to
11// better prepare it for SelectionDAG-based code generation. This works around
12// the limitations of the basic-block-at-a-time approach.
13//
14// First it scans all instructions for integer constants and calculates its
15// cost. If the constant can be folded into the instruction (the cost is
16// TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't
17// consider it expensive and leave it alone. This is the default behavior and
18// the default implementation of getIntImmCost will always return TCC_Free.
19//
20// If the cost is more than TCC_BASIC, then the integer constant can't be folded
21// into the instruction and it might be beneficial to hoist the constant.
22// Similar constants are coalesced to reduce register pressure and
23// materialization code.
24//
25// When a constant is hoisted, it is also hidden behind a bitcast to force it to
26// be live-out of the basic block. Otherwise the constant would be just
27// duplicated and each basic block would have its own copy in the SelectionDAG.
28// The SelectionDAG recognizes such constants as opaque and doesn't perform
29// certain transformations on them, which would create a new expensive constant.
30//
31// This optimization is only applied to integer constants in instructions and
32// simple (this means not nested) constant cast expressions. For example:
33// %0 = load i64* inttoptr (i64 big_constant to i64*)
34//===----------------------------------------------------------------------===//
35
36#include "llvm/Transforms/Scalar/ConstantHoisting.h"
37#include "llvm/ADT/APInt.h"
38#include "llvm/ADT/DenseMap.h"
39#include "llvm/ADT/None.h"
40#include "llvm/ADT/Optional.h"
41#include "llvm/ADT/SmallPtrSet.h"
42#include "llvm/ADT/SmallVector.h"
43#include "llvm/ADT/Statistic.h"
44#include "llvm/Analysis/BlockFrequencyInfo.h"
45#include "llvm/Analysis/TargetTransformInfo.h"
46#include "llvm/Transforms/Utils/Local.h"
47#include "llvm/IR/BasicBlock.h"
48#include "llvm/IR/Constants.h"
49#include "llvm/IR/DebugInfoMetadata.h"
50#include "llvm/IR/Dominators.h"
51#include "llvm/IR/Function.h"
52#include "llvm/IR/InstrTypes.h"
53#include "llvm/IR/Instruction.h"
54#include "llvm/IR/Instructions.h"
55#include "llvm/IR/IntrinsicInst.h"
56#include "llvm/IR/Value.h"
57#include "llvm/Pass.h"
58#include "llvm/Support/BlockFrequency.h"
59#include "llvm/Support/Casting.h"
60#include "llvm/Support/CommandLine.h"
61#include "llvm/Support/Debug.h"
62#include "llvm/Support/raw_ostream.h"
63#include "llvm/Transforms/Scalar.h"
64#include <algorithm>
65#include <cassert>
66#include <cstdint>
67#include <iterator>
68#include <tuple>
69#include <utility>
70
71using namespace llvm;
72using namespace consthoist;
73
74#define DEBUG_TYPE"consthoist" "consthoist"
75
76STATISTIC(NumConstantsHoisted, "Number of constants hoisted")static llvm::Statistic NumConstantsHoisted = {"consthoist", "NumConstantsHoisted"
, "Number of constants hoisted", {0}, {false}}
;
77STATISTIC(NumConstantsRebased, "Number of constants rebased")static llvm::Statistic NumConstantsRebased = {"consthoist", "NumConstantsRebased"
, "Number of constants rebased", {0}, {false}}
;
78
79static cl::opt<bool> ConstHoistWithBlockFrequency(
80 "consthoist-with-block-frequency", cl::init(true), cl::Hidden,
81 cl::desc("Enable the use of the block frequency analysis to reduce the "
82 "chance to execute const materialization more frequently than "
83 "without hoisting."));
84
85namespace {
86
87/// The constant hoisting pass.
88class ConstantHoistingLegacyPass : public FunctionPass {
89public:
90 static char ID; // Pass identification, replacement for typeid
91
92 ConstantHoistingLegacyPass() : FunctionPass(ID) {
93 initializeConstantHoistingLegacyPassPass(*PassRegistry::getPassRegistry());
94 }
95
96 bool runOnFunction(Function &Fn) override;
97
98 StringRef getPassName() const override { return "Constant Hoisting"; }
99
100 void getAnalysisUsage(AnalysisUsage &AU) const override {
101 AU.setPreservesCFG();
102 if (ConstHoistWithBlockFrequency)
103 AU.addRequired<BlockFrequencyInfoWrapperPass>();
104 AU.addRequired<DominatorTreeWrapperPass>();
105 AU.addRequired<TargetTransformInfoWrapperPass>();
106 }
107
108 void releaseMemory() override { Impl.releaseMemory(); }
109
110private:
111 ConstantHoistingPass Impl;
112};
113
114} // end anonymous namespace
115
116char ConstantHoistingLegacyPass::ID = 0;
117
118INITIALIZE_PASS_BEGIN(ConstantHoistingLegacyPass, "consthoist",static void *initializeConstantHoistingLegacyPassPassOnce(PassRegistry
&Registry) {
119 "Constant Hoisting", false, false)static void *initializeConstantHoistingLegacyPassPassOnce(PassRegistry
&Registry) {
120INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)initializeBlockFrequencyInfoWrapperPassPass(Registry);
121INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
122INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
123INITIALIZE_PASS_END(ConstantHoistingLegacyPass, "consthoist",PassInfo *PI = new PassInfo( "Constant Hoisting", "consthoist"
, &ConstantHoistingLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<ConstantHoistingLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeConstantHoistingLegacyPassPassFlag; void
llvm::initializeConstantHoistingLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeConstantHoistingLegacyPassPassFlag
, initializeConstantHoistingLegacyPassPassOnce, std::ref(Registry
)); }
124 "Constant Hoisting", false, false)PassInfo *PI = new PassInfo( "Constant Hoisting", "consthoist"
, &ConstantHoistingLegacyPass::ID, PassInfo::NormalCtor_t
(callDefaultCtor<ConstantHoistingLegacyPass>), false, false
); Registry.registerPass(*PI, true); return PI; } static llvm
::once_flag InitializeConstantHoistingLegacyPassPassFlag; void
llvm::initializeConstantHoistingLegacyPassPass(PassRegistry &
Registry) { llvm::call_once(InitializeConstantHoistingLegacyPassPassFlag
, initializeConstantHoistingLegacyPassPassOnce, std::ref(Registry
)); }
125
126FunctionPass *llvm::createConstantHoistingPass() {
127 return new ConstantHoistingLegacyPass();
128}
129
130/// Perform the constant hoisting optimization for the given function.
131bool ConstantHoistingLegacyPass::runOnFunction(Function &Fn) {
132 if (skipFunction(Fn))
133 return false;
134
135 LLVM_DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "********** Begin Constant Hoisting **********\n"
; } } while (false)
;
136 LLVM_DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "********** Function: " <<
Fn.getName() << '\n'; } } while (false)
;
137
138 bool MadeChange =
139 Impl.runImpl(Fn, getAnalysis<TargetTransformInfoWrapperPass>().getTTI(Fn),
140 getAnalysis<DominatorTreeWrapperPass>().getDomTree(),
141 ConstHoistWithBlockFrequency
142 ? &getAnalysis<BlockFrequencyInfoWrapperPass>().getBFI()
143 : nullptr,
144 Fn.getEntryBlock());
145
146 if (MadeChange) {
147 LLVM_DEBUG(dbgs() << "********** Function after Constant Hoisting: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "********** Function after Constant Hoisting: "
<< Fn.getName() << '\n'; } } while (false)
148 << Fn.getName() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "********** Function after Constant Hoisting: "
<< Fn.getName() << '\n'; } } while (false)
;
149 LLVM_DEBUG(dbgs() << Fn)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << Fn; } } while (false)
;
150 }
151 LLVM_DEBUG(dbgs() << "********** End Constant Hoisting **********\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "********** End Constant Hoisting **********\n"
; } } while (false)
;
152
153 return MadeChange;
154}
155
156/// Find the constant materialization insertion point.
157Instruction *ConstantHoistingPass::findMatInsertPt(Instruction *Inst,
158 unsigned Idx) const {
159 // If the operand is a cast instruction, then we have to materialize the
160 // constant before the cast instruction.
161 if (Idx != ~0U) {
162 Value *Opnd = Inst->getOperand(Idx);
163 if (auto CastInst = dyn_cast<Instruction>(Opnd))
164 if (CastInst->isCast())
165 return CastInst;
166 }
167
168 // The simple and common case. This also includes constant expressions.
169 if (!isa<PHINode>(Inst) && !Inst->isEHPad())
170 return Inst;
171
172 // We can't insert directly before a phi node or an eh pad. Insert before
173 // the terminator of the incoming or dominating block.
174 assert(Entry != Inst->getParent() && "PHI or landing pad in entry block!")(static_cast <bool> (Entry != Inst->getParent() &&
"PHI or landing pad in entry block!") ? void (0) : __assert_fail
("Entry != Inst->getParent() && \"PHI or landing pad in entry block!\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 174, __extension__ __PRETTY_FUNCTION__))
;
175 if (Idx != ~0U && isa<PHINode>(Inst))
176 return cast<PHINode>(Inst)->getIncomingBlock(Idx)->getTerminator();
177
178 // This must be an EH pad. Iterate over immediate dominators until we find a
179 // non-EH pad. We need to skip over catchswitch blocks, which are both EH pads
180 // and terminators.
181 auto IDom = DT->getNode(Inst->getParent())->getIDom();
182 while (IDom->getBlock()->isEHPad()) {
183 assert(Entry != IDom->getBlock() && "eh pad in entry block")(static_cast <bool> (Entry != IDom->getBlock() &&
"eh pad in entry block") ? void (0) : __assert_fail ("Entry != IDom->getBlock() && \"eh pad in entry block\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 183, __extension__ __PRETTY_FUNCTION__))
;
184 IDom = IDom->getIDom();
185 }
186
187 return IDom->getBlock()->getTerminator();
188}
189
190/// Given \p BBs as input, find another set of BBs which collectively
191/// dominates \p BBs and have the minimal sum of frequencies. Return the BB
192/// set found in \p BBs.
193static void findBestInsertionSet(DominatorTree &DT, BlockFrequencyInfo &BFI,
194 BasicBlock *Entry,
195 SmallPtrSet<BasicBlock *, 8> &BBs) {
196 assert(!BBs.count(Entry) && "Assume Entry is not in BBs")(static_cast <bool> (!BBs.count(Entry) && "Assume Entry is not in BBs"
) ? void (0) : __assert_fail ("!BBs.count(Entry) && \"Assume Entry is not in BBs\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 196, __extension__ __PRETTY_FUNCTION__))
;
197 // Nodes on the current path to the root.
198 SmallPtrSet<BasicBlock *, 8> Path;
199 // Candidates includes any block 'BB' in set 'BBs' that is not strictly
200 // dominated by any other blocks in set 'BBs', and all nodes in the path
201 // in the dominator tree from Entry to 'BB'.
202 SmallPtrSet<BasicBlock *, 16> Candidates;
203 for (auto BB : BBs) {
204 Path.clear();
205 // Walk up the dominator tree until Entry or another BB in BBs
206 // is reached. Insert the nodes on the way to the Path.
207 BasicBlock *Node = BB;
208 // The "Path" is a candidate path to be added into Candidates set.
209 bool isCandidate = false;
210 do {
211 Path.insert(Node);
212 if (Node == Entry || Candidates.count(Node)) {
213 isCandidate = true;
214 break;
215 }
216 assert(DT.getNode(Node)->getIDom() &&(static_cast <bool> (DT.getNode(Node)->getIDom() &&
"Entry doens't dominate current Node") ? void (0) : __assert_fail
("DT.getNode(Node)->getIDom() && \"Entry doens't dominate current Node\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 217, __extension__ __PRETTY_FUNCTION__))
217 "Entry doens't dominate current Node")(static_cast <bool> (DT.getNode(Node)->getIDom() &&
"Entry doens't dominate current Node") ? void (0) : __assert_fail
("DT.getNode(Node)->getIDom() && \"Entry doens't dominate current Node\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 217, __extension__ __PRETTY_FUNCTION__))
;
218 Node = DT.getNode(Node)->getIDom()->getBlock();
219 } while (!BBs.count(Node));
220
221 // If isCandidate is false, Node is another Block in BBs dominating
222 // current 'BB'. Drop the nodes on the Path.
223 if (!isCandidate)
224 continue;
225
226 // Add nodes on the Path into Candidates.
227 Candidates.insert(Path.begin(), Path.end());
228 }
229
230 // Sort the nodes in Candidates in top-down order and save the nodes
231 // in Orders.
232 unsigned Idx = 0;
233 SmallVector<BasicBlock *, 16> Orders;
234 Orders.push_back(Entry);
235 while (Idx != Orders.size()) {
236 BasicBlock *Node = Orders[Idx++];
237 for (auto ChildDomNode : DT.getNode(Node)->getChildren()) {
238 if (Candidates.count(ChildDomNode->getBlock()))
239 Orders.push_back(ChildDomNode->getBlock());
240 }
241 }
242
243 // Visit Orders in bottom-up order.
244 using InsertPtsCostPair =
245 std::pair<SmallPtrSet<BasicBlock *, 16>, BlockFrequency>;
246
247 // InsertPtsMap is a map from a BB to the best insertion points for the
248 // subtree of BB (subtree not including the BB itself).
249 DenseMap<BasicBlock *, InsertPtsCostPair> InsertPtsMap;
250 InsertPtsMap.reserve(Orders.size() + 1);
251 for (auto RIt = Orders.rbegin(); RIt != Orders.rend(); RIt++) {
252 BasicBlock *Node = *RIt;
253 bool NodeInBBs = BBs.count(Node);
254 SmallPtrSet<BasicBlock *, 16> &InsertPts = InsertPtsMap[Node].first;
255 BlockFrequency &InsertPtsFreq = InsertPtsMap[Node].second;
256
257 // Return the optimal insert points in BBs.
258 if (Node == Entry) {
259 BBs.clear();
260 if (InsertPtsFreq > BFI.getBlockFreq(Node) ||
261 (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1))
262 BBs.insert(Entry);
263 else
264 BBs.insert(InsertPts.begin(), InsertPts.end());
265 break;
266 }
267
268 BasicBlock *Parent = DT.getNode(Node)->getIDom()->getBlock();
269 // Initially, ParentInsertPts is empty and ParentPtsFreq is 0. Every child
270 // will update its parent's ParentInsertPts and ParentPtsFreq.
271 SmallPtrSet<BasicBlock *, 16> &ParentInsertPts = InsertPtsMap[Parent].first;
272 BlockFrequency &ParentPtsFreq = InsertPtsMap[Parent].second;
273 // Choose to insert in Node or in subtree of Node.
274 // Don't hoist to EHPad because we may not find a proper place to insert
275 // in EHPad.
276 // If the total frequency of InsertPts is the same as the frequency of the
277 // target Node, and InsertPts contains more than one nodes, choose hoisting
278 // to reduce code size.
279 if (NodeInBBs ||
280 (!Node->isEHPad() &&
281 (InsertPtsFreq > BFI.getBlockFreq(Node) ||
282 (InsertPtsFreq == BFI.getBlockFreq(Node) && InsertPts.size() > 1)))) {
283 ParentInsertPts.insert(Node);
284 ParentPtsFreq += BFI.getBlockFreq(Node);
285 } else {
286 ParentInsertPts.insert(InsertPts.begin(), InsertPts.end());
287 ParentPtsFreq += InsertPtsFreq;
288 }
289 }
290}
291
292/// Find an insertion point that dominates all uses.
293SmallPtrSet<Instruction *, 8> ConstantHoistingPass::findConstantInsertionPoint(
294 const ConstantInfo &ConstInfo) const {
295 assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.")(static_cast <bool> (!ConstInfo.RebasedConstants.empty(
) && "Invalid constant info entry.") ? void (0) : __assert_fail
("!ConstInfo.RebasedConstants.empty() && \"Invalid constant info entry.\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 295, __extension__ __PRETTY_FUNCTION__))
;
296 // Collect all basic blocks.
297 SmallPtrSet<BasicBlock *, 8> BBs;
298 SmallPtrSet<Instruction *, 8> InsertPts;
299 for (auto const &RCI : ConstInfo.RebasedConstants)
11
Assuming '__begin1' is equal to '__end1'
300 for (auto const &U : RCI.Uses)
301 BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());
302
303 if (BBs.count(Entry)) {
12
Assuming the condition is false
13
Taking false branch
304 InsertPts.insert(&Entry->front());
305 return InsertPts;
306 }
307
308 if (BFI) {
14
Assuming the condition is false
15
Taking false branch
309 findBestInsertionSet(*DT, *BFI, Entry, BBs);
310 for (auto BB : BBs) {
311 BasicBlock::iterator InsertPt = BB->begin();
312 for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
313 ;
314 InsertPts.insert(&*InsertPt);
315 }
316 return InsertPts;
317 }
318
319 while (BBs.size() >= 2) {
16
Assuming the condition is true
17
Loop condition is true. Entering loop body
320 BasicBlock *BB, *BB1, *BB2;
321 BB1 = *BBs.begin();
322 BB2 = *std::next(BBs.begin());
323 BB = DT->findNearestCommonDominator(BB1, BB2);
324 if (BB == Entry) {
18
Assuming pointer value is null
19
Taking true branch
325 InsertPts.insert(&Entry->front());
20
Called C++ object pointer is null
326 return InsertPts;
327 }
328 BBs.erase(BB1);
329 BBs.erase(BB2);
330 BBs.insert(BB);
331 }
332 assert((BBs.size() == 1) && "Expected only one element.")(static_cast <bool> ((BBs.size() == 1) && "Expected only one element."
) ? void (0) : __assert_fail ("(BBs.size() == 1) && \"Expected only one element.\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 332, __extension__ __PRETTY_FUNCTION__))
;
333 Instruction &FirstInst = (*BBs.begin())->front();
334 InsertPts.insert(findMatInsertPt(&FirstInst));
335 return InsertPts;
336}
337
338/// Record constant integer ConstInt for instruction Inst at operand
339/// index Idx.
340///
341/// The operand at index Idx is not necessarily the constant integer itself. It
342/// could also be a cast instruction or a constant expression that uses the
343// constant integer.
344void ConstantHoistingPass::collectConstantCandidates(
345 ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx,
346 ConstantInt *ConstInt) {
347 unsigned Cost;
348 // Ask the target about the cost of materializing the constant for the given
349 // instruction and operand index.
350 if (auto IntrInst = dyn_cast<IntrinsicInst>(Inst))
351 Cost = TTI->getIntImmCost(IntrInst->getIntrinsicID(), Idx,
352 ConstInt->getValue(), ConstInt->getType());
353 else
354 Cost = TTI->getIntImmCost(Inst->getOpcode(), Idx, ConstInt->getValue(),
355 ConstInt->getType());
356
357 // Ignore cheap integer constants.
358 if (Cost > TargetTransformInfo::TCC_Basic) {
359 ConstCandMapType::iterator Itr;
360 bool Inserted;
361 std::tie(Itr, Inserted) = ConstCandMap.insert(std::make_pair(ConstInt, 0));
362 if (Inserted) {
363 ConstCandVec.push_back(ConstantCandidate(ConstInt));
364 Itr->second = ConstCandVec.size() - 1;
365 }
366 ConstCandVec[Itr->second].addUser(Inst, Idx, Cost);
367 LLVM_DEBUG(if (isa<ConstantInt>(Inst->getOperand(Idx))) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
368 << "Collect constant " << *ConstInt << " from " << *Instdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
369 << " with cost " << Cost << '\n';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
370 else dbgs() << "Collect constant " << *ConstIntdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
371 << " indirectly from " << *Inst << " via "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
372 << *Inst->getOperand(Idx) << " with cost " << Costdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
373 << '\n';)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { if (isa<ConstantInt>(Inst->getOperand
(Idx))) dbgs() << "Collect constant " << *ConstInt
<< " from " << *Inst << " with cost " <<
Cost << '\n'; else dbgs() << "Collect constant "
<< *ConstInt << " indirectly from " << *Inst
<< " via " << *Inst->getOperand(Idx) <<
" with cost " << Cost << '\n';; } } while (false
)
;
374 }
375}
376
377/// Check the operand for instruction Inst at index Idx.
378void ConstantHoistingPass::collectConstantCandidates(
379 ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx) {
380 Value *Opnd = Inst->getOperand(Idx);
381
382 // Visit constant integers.
383 if (auto ConstInt = dyn_cast<ConstantInt>(Opnd)) {
384 collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
385 return;
386 }
387
388 // Visit cast instructions that have constant integers.
389 if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
390 // Only visit cast instructions, which have been skipped. All other
391 // instructions should have already been visited.
392 if (!CastInst->isCast())
393 return;
394
395 if (auto *ConstInt = dyn_cast<ConstantInt>(CastInst->getOperand(0))) {
396 // Pretend the constant is directly used by the instruction and ignore
397 // the cast instruction.
398 collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
399 return;
400 }
401 }
402
403 // Visit constant expressions that have constant integers.
404 if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
405 // Only visit constant cast expressions.
406 if (!ConstExpr->isCast())
407 return;
408
409 if (auto ConstInt = dyn_cast<ConstantInt>(ConstExpr->getOperand(0))) {
410 // Pretend the constant is directly used by the instruction and ignore
411 // the constant expression.
412 collectConstantCandidates(ConstCandMap, Inst, Idx, ConstInt);
413 return;
414 }
415 }
416}
417
418/// Scan the instruction for expensive integer constants and record them
419/// in the constant candidate vector.
420void ConstantHoistingPass::collectConstantCandidates(
421 ConstCandMapType &ConstCandMap, Instruction *Inst) {
422 // Skip all cast instructions. They are visited indirectly later on.
423 if (Inst->isCast())
424 return;
425
426 // Scan all operands.
427 for (unsigned Idx = 0, E = Inst->getNumOperands(); Idx != E; ++Idx) {
428 // The cost of materializing the constants (defined in
429 // `TargetTransformInfo::getIntImmCost`) for instructions which only take
430 // constant variables is lower than `TargetTransformInfo::TCC_Basic`. So
431 // it's safe for us to collect constant candidates from all IntrinsicInsts.
432 if (canReplaceOperandWithVariable(Inst, Idx) || isa<IntrinsicInst>(Inst)) {
433 collectConstantCandidates(ConstCandMap, Inst, Idx);
434 }
435 } // end of for all operands
436}
437
438/// Collect all integer constants in the function that cannot be folded
439/// into an instruction itself.
440void ConstantHoistingPass::collectConstantCandidates(Function &Fn) {
441 ConstCandMapType ConstCandMap;
442 for (BasicBlock &BB : Fn)
443 for (Instruction &Inst : BB)
444 collectConstantCandidates(ConstCandMap, &Inst);
445}
446
447// This helper function is necessary to deal with values that have different
448// bit widths (APInt Operator- does not like that). If the value cannot be
449// represented in uint64 we return an "empty" APInt. This is then interpreted
450// as the value is not in range.
451static Optional<APInt> calculateOffsetDiff(const APInt &V1, const APInt &V2) {
452 Optional<APInt> Res = None;
453 unsigned BW = V1.getBitWidth() > V2.getBitWidth() ?
454 V1.getBitWidth() : V2.getBitWidth();
455 uint64_t LimVal1 = V1.getLimitedValue();
456 uint64_t LimVal2 = V2.getLimitedValue();
457
458 if (LimVal1 == ~0ULL || LimVal2 == ~0ULL)
459 return Res;
460
461 uint64_t Diff = LimVal1 - LimVal2;
462 return APInt(BW, Diff, true);
463}
464
465// From a list of constants, one needs to picked as the base and the other
466// constants will be transformed into an offset from that base constant. The
467// question is which we can pick best? For example, consider these constants
468// and their number of uses:
469//
470// Constants| 2 | 4 | 12 | 42 |
471// NumUses | 3 | 2 | 8 | 7 |
472//
473// Selecting constant 12 because it has the most uses will generate negative
474// offsets for constants 2 and 4 (i.e. -10 and -8 respectively). If negative
475// offsets lead to less optimal code generation, then there might be better
476// solutions. Suppose immediates in the range of 0..35 are most optimally
477// supported by the architecture, then selecting constant 2 is most optimal
478// because this will generate offsets: 0, 2, 10, 40. Offsets 0, 2 and 10 are in
479// range 0..35, and thus 3 + 2 + 8 = 13 uses are in range. Selecting 12 would
480// have only 8 uses in range, so choosing 2 as a base is more optimal. Thus, in
481// selecting the base constant the range of the offsets is a very important
482// factor too that we take into account here. This algorithm calculates a total
483// costs for selecting a constant as the base and substract the costs if
484// immediates are out of range. It has quadratic complexity, so we call this
485// function only when we're optimising for size and there are less than 100
486// constants, we fall back to the straightforward algorithm otherwise
487// which does not do all the offset calculations.
488unsigned
489ConstantHoistingPass::maximizeConstantsInRange(ConstCandVecType::iterator S,
490 ConstCandVecType::iterator E,
491 ConstCandVecType::iterator &MaxCostItr) {
492 unsigned NumUses = 0;
493
494 if(!Entry->getParent()->optForSize() || std::distance(S,E) > 100) {
495 for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
496 NumUses += ConstCand->Uses.size();
497 if (ConstCand->CumulativeCost > MaxCostItr->CumulativeCost)
498 MaxCostItr = ConstCand;
499 }
500 return NumUses;
501 }
502
503 LLVM_DEBUG(dbgs() << "== Maximize constants in range ==\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "== Maximize constants in range ==\n"
; } } while (false)
;
504 int MaxCost = -1;
505 for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
506 auto Value = ConstCand->ConstInt->getValue();
507 Type *Ty = ConstCand->ConstInt->getType();
508 int Cost = 0;
509 NumUses += ConstCand->Uses.size();
510 LLVM_DEBUG(dbgs() << "= Constant: " << ConstCand->ConstInt->getValue()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "= Constant: " << ConstCand
->ConstInt->getValue() << "\n"; } } while (false)
511 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "= Constant: " << ConstCand
->ConstInt->getValue() << "\n"; } } while (false)
;
512
513 for (auto User : ConstCand->Uses) {
514 unsigned Opcode = User.Inst->getOpcode();
515 unsigned OpndIdx = User.OpndIdx;
516 Cost += TTI->getIntImmCost(Opcode, OpndIdx, Value, Ty);
517 LLVM_DEBUG(dbgs() << "Cost: " << Cost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Cost: " << Cost <<
"\n"; } } while (false)
;
518
519 for (auto C2 = S; C2 != E; ++C2) {
520 Optional<APInt> Diff = calculateOffsetDiff(
521 C2->ConstInt->getValue(),
522 ConstCand->ConstInt->getValue());
523 if (Diff) {
524 const int ImmCosts =
525 TTI->getIntImmCodeSizeCost(Opcode, OpndIdx, Diff.getValue(), Ty);
526 Cost -= ImmCosts;
527 LLVM_DEBUG(dbgs() << "Offset " << Diff.getValue() << " "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Offset " << Diff.getValue
() << " " << "has penalty: " << ImmCosts <<
"\n" << "Adjusted cost: " << Cost << "\n";
} } while (false)
528 << "has penalty: " << ImmCosts << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Offset " << Diff.getValue
() << " " << "has penalty: " << ImmCosts <<
"\n" << "Adjusted cost: " << Cost << "\n";
} } while (false)
529 << "Adjusted cost: " << Cost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Offset " << Diff.getValue
() << " " << "has penalty: " << ImmCosts <<
"\n" << "Adjusted cost: " << Cost << "\n";
} } while (false)
;
530 }
531 }
532 }
533 LLVM_DEBUG(dbgs() << "Cumulative cost: " << Cost << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Cumulative cost: " <<
Cost << "\n"; } } while (false)
;
534 if (Cost > MaxCost) {
535 MaxCost = Cost;
536 MaxCostItr = ConstCand;
537 LLVM_DEBUG(dbgs() << "New candidate: " << MaxCostItr->ConstInt->getValue()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "New candidate: " << MaxCostItr
->ConstInt->getValue() << "\n"; } } while (false)
538 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "New candidate: " << MaxCostItr
->ConstInt->getValue() << "\n"; } } while (false)
;
539 }
540 }
541 return NumUses;
542}
543
544/// Find the base constant within the given range and rebase all other
545/// constants with respect to the base constant.
546void ConstantHoistingPass::findAndMakeBaseConstant(
547 ConstCandVecType::iterator S, ConstCandVecType::iterator E) {
548 auto MaxCostItr = S;
549 unsigned NumUses = maximizeConstantsInRange(S, E, MaxCostItr);
550
551 // Don't hoist constants that have only one use.
552 if (NumUses <= 1)
553 return;
554
555 ConstantInfo ConstInfo;
556 ConstInfo.BaseConstant = MaxCostItr->ConstInt;
557 Type *Ty = ConstInfo.BaseConstant->getType();
558
559 // Rebase the constants with respect to the base constant.
560 for (auto ConstCand = S; ConstCand != E; ++ConstCand) {
561 APInt Diff = ConstCand->ConstInt->getValue() -
562 ConstInfo.BaseConstant->getValue();
563 Constant *Offset = Diff == 0 ? nullptr : ConstantInt::get(Ty, Diff);
564 ConstInfo.RebasedConstants.push_back(
565 RebasedConstantInfo(std::move(ConstCand->Uses), Offset));
566 }
567 ConstantVec.push_back(std::move(ConstInfo));
568}
569
570/// Finds and combines constant candidates that can be easily
571/// rematerialized with an add from a common base constant.
572void ConstantHoistingPass::findBaseConstants() {
573 // Sort the constants by value and type. This invalidates the mapping!
574 llvm::sort(ConstCandVec.begin(), ConstCandVec.end(),
575 [](const ConstantCandidate &LHS, const ConstantCandidate &RHS) {
576 if (LHS.ConstInt->getType() != RHS.ConstInt->getType())
577 return LHS.ConstInt->getType()->getBitWidth() <
578 RHS.ConstInt->getType()->getBitWidth();
579 return LHS.ConstInt->getValue().ult(RHS.ConstInt->getValue());
580 });
581
582 // Simple linear scan through the sorted constant candidate vector for viable
583 // merge candidates.
584 auto MinValItr = ConstCandVec.begin();
585 for (auto CC = std::next(ConstCandVec.begin()), E = ConstCandVec.end();
586 CC != E; ++CC) {
587 if (MinValItr->ConstInt->getType() == CC->ConstInt->getType()) {
588 // Check if the constant is in range of an add with immediate.
589 APInt Diff = CC->ConstInt->getValue() - MinValItr->ConstInt->getValue();
590 if ((Diff.getBitWidth() <= 64) &&
591 TTI->isLegalAddImmediate(Diff.getSExtValue()))
592 continue;
593 }
594 // We either have now a different constant type or the constant is not in
595 // range of an add with immediate anymore.
596 findAndMakeBaseConstant(MinValItr, CC);
597 // Start a new base constant search.
598 MinValItr = CC;
599 }
600 // Finalize the last base constant search.
601 findAndMakeBaseConstant(MinValItr, ConstCandVec.end());
602}
603
604/// Updates the operand at Idx in instruction Inst with the result of
605/// instruction Mat. If the instruction is a PHI node then special
606/// handling for duplicate values form the same incoming basic block is
607/// required.
608/// \return The update will always succeed, but the return value indicated if
609/// Mat was used for the update or not.
610static bool updateOperand(Instruction *Inst, unsigned Idx, Instruction *Mat) {
611 if (auto PHI = dyn_cast<PHINode>(Inst)) {
612 // Check if any previous operand of the PHI node has the same incoming basic
613 // block. This is a very odd case that happens when the incoming basic block
614 // has a switch statement. In this case use the same value as the previous
615 // operand(s), otherwise we will fail verification due to different values.
616 // The values are actually the same, but the variable names are different
617 // and the verifier doesn't like that.
618 BasicBlock *IncomingBB = PHI->getIncomingBlock(Idx);
619 for (unsigned i = 0; i < Idx; ++i) {
620 if (PHI->getIncomingBlock(i) == IncomingBB) {
621 Value *IncomingVal = PHI->getIncomingValue(i);
622 Inst->setOperand(Idx, IncomingVal);
623 return false;
624 }
625 }
626 }
627
628 Inst->setOperand(Idx, Mat);
629 return true;
630}
631
632/// Emit materialization code for all rebased constants and update their
633/// users.
634void ConstantHoistingPass::emitBaseConstants(Instruction *Base,
635 Constant *Offset,
636 const ConstantUser &ConstUser) {
637 Instruction *Mat = Base;
638 if (Offset) {
639 Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst,
640 ConstUser.OpndIdx);
641 Mat = BinaryOperator::Create(Instruction::Add, Base, Offset,
642 "const_mat", InsertionPt);
643
644 LLVM_DEBUG(dbgs() << "Materialize constant (" << *Base->getOperand(0)do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Materialize constant (" <<
*Base->getOperand(0) << " + " << *Offset <<
") in BB " << Mat->getParent()->getName() <<
'\n' << *Mat << '\n'; } } while (false)
645 << " + " << *Offset << ") in BB "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Materialize constant (" <<
*Base->getOperand(0) << " + " << *Offset <<
") in BB " << Mat->getParent()->getName() <<
'\n' << *Mat << '\n'; } } while (false)
646 << Mat->getParent()->getName() << '\n'do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Materialize constant (" <<
*Base->getOperand(0) << " + " << *Offset <<
") in BB " << Mat->getParent()->getName() <<
'\n' << *Mat << '\n'; } } while (false)
647 << *Mat << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Materialize constant (" <<
*Base->getOperand(0) << " + " << *Offset <<
") in BB " << Mat->getParent()->getName() <<
'\n' << *Mat << '\n'; } } while (false)
;
648 Mat->setDebugLoc(ConstUser.Inst->getDebugLoc());
649 }
650 Value *Opnd = ConstUser.Inst->getOperand(ConstUser.OpndIdx);
651
652 // Visit constant integer.
653 if (isa<ConstantInt>(Opnd)) {
654 LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Update: " << *ConstUser
.Inst << '\n'; } } while (false)
;
655 if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, Mat) && Offset)
656 Mat->eraseFromParent();
657 LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "To : " << *ConstUser
.Inst << '\n'; } } while (false)
;
658 return;
659 }
660
661 // Visit cast instruction.
662 if (auto CastInst = dyn_cast<Instruction>(Opnd)) {
663 assert(CastInst->isCast() && "Expected an cast instruction!")(static_cast <bool> (CastInst->isCast() && "Expected an cast instruction!"
) ? void (0) : __assert_fail ("CastInst->isCast() && \"Expected an cast instruction!\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 663, __extension__ __PRETTY_FUNCTION__))
;
664 // Check if we already have visited this cast instruction before to avoid
665 // unnecessary cloning.
666 Instruction *&ClonedCastInst = ClonedCastMap[CastInst];
667 if (!ClonedCastInst) {
668 ClonedCastInst = CastInst->clone();
669 ClonedCastInst->setOperand(0, Mat);
670 ClonedCastInst->insertAfter(CastInst);
671 // Use the same debug location as the original cast instruction.
672 ClonedCastInst->setDebugLoc(CastInst->getDebugLoc());
673 LLVM_DEBUG(dbgs() << "Clone instruction: " << *CastInst << '\n'do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Clone instruction: " <<
*CastInst << '\n' << "To : " <<
*ClonedCastInst << '\n'; } } while (false)
674 << "To : " << *ClonedCastInst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Clone instruction: " <<
*CastInst << '\n' << "To : " <<
*ClonedCastInst << '\n'; } } while (false)
;
675 }
676
677 LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Update: " << *ConstUser
.Inst << '\n'; } } while (false)
;
678 updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ClonedCastInst);
679 LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "To : " << *ConstUser
.Inst << '\n'; } } while (false)
;
680 return;
681 }
682
683 // Visit constant expression.
684 if (auto ConstExpr = dyn_cast<ConstantExpr>(Opnd)) {
685 Instruction *ConstExprInst = ConstExpr->getAsInstruction();
686 ConstExprInst->setOperand(0, Mat);
687 ConstExprInst->insertBefore(findMatInsertPt(ConstUser.Inst,
688 ConstUser.OpndIdx));
689
690 // Use the same debug location as the instruction we are about to update.
691 ConstExprInst->setDebugLoc(ConstUser.Inst->getDebugLoc());
692
693 LLVM_DEBUG(dbgs() << "Create instruction: " << *ConstExprInst << '\n'do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Create instruction: " <<
*ConstExprInst << '\n' << "From : "
<< *ConstExpr << '\n'; } } while (false)
694 << "From : " << *ConstExpr << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Create instruction: " <<
*ConstExprInst << '\n' << "From : "
<< *ConstExpr << '\n'; } } while (false)
;
695 LLVM_DEBUG(dbgs() << "Update: " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Update: " << *ConstUser
.Inst << '\n'; } } while (false)
;
696 if (!updateOperand(ConstUser.Inst, ConstUser.OpndIdx, ConstExprInst)) {
697 ConstExprInst->eraseFromParent();
698 if (Offset)
699 Mat->eraseFromParent();
700 }
701 LLVM_DEBUG(dbgs() << "To : " << *ConstUser.Inst << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "To : " << *ConstUser
.Inst << '\n'; } } while (false)
;
702 return;
703 }
704}
705
706/// Hoist and hide the base constant behind a bitcast and emit
707/// materialization code for derived constants.
708bool ConstantHoistingPass::emitBaseConstants() {
709 bool MadeChange = false;
710 for (auto const &ConstInfo : ConstantVec) {
8
Value assigned to field 'Entry'
9
Assuming '__begin1' is not equal to '__end1'
711 // Hoist and hide the base constant behind a bitcast.
712 SmallPtrSet<Instruction *, 8> IPSet = findConstantInsertionPoint(ConstInfo);
10
Calling 'ConstantHoistingPass::findConstantInsertionPoint'
713 assert(!IPSet.empty() && "IPSet is empty")(static_cast <bool> (!IPSet.empty() && "IPSet is empty"
) ? void (0) : __assert_fail ("!IPSet.empty() && \"IPSet is empty\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 713, __extension__ __PRETTY_FUNCTION__))
;
714
715 unsigned UsesNum = 0;
716 unsigned ReBasesNum = 0;
717 for (Instruction *IP : IPSet) {
718 IntegerType *Ty = ConstInfo.BaseConstant->getType();
719 Instruction *Base =
720 new BitCastInst(ConstInfo.BaseConstant, Ty, "const", IP);
721
722 Base->setDebugLoc(IP->getDebugLoc());
723
724 LLVM_DEBUG(dbgs() << "Hoist constant (" << *ConstInfo.BaseConstantdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Hoist constant (" <<
*ConstInfo.BaseConstant << ") to BB " << IP->
getParent()->getName() << '\n' << *Base <<
'\n'; } } while (false)
725 << ") to BB " << IP->getParent()->getName() << '\n'do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Hoist constant (" <<
*ConstInfo.BaseConstant << ") to BB " << IP->
getParent()->getName() << '\n' << *Base <<
'\n'; } } while (false)
726 << *Base << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("consthoist")) { dbgs() << "Hoist constant (" <<
*ConstInfo.BaseConstant << ") to BB " << IP->
getParent()->getName() << '\n' << *Base <<
'\n'; } } while (false)
;
727
728 // Emit materialization code for all rebased constants.
729 unsigned Uses = 0;
730 for (auto const &RCI : ConstInfo.RebasedConstants) {
731 for (auto const &U : RCI.Uses) {
732 Uses++;
733 BasicBlock *OrigMatInsertBB =
734 findMatInsertPt(U.Inst, U.OpndIdx)->getParent();
735 // If Base constant is to be inserted in multiple places,
736 // generate rebase for U using the Base dominating U.
737 if (IPSet.size() == 1 ||
738 DT->dominates(Base->getParent(), OrigMatInsertBB)) {
739 emitBaseConstants(Base, RCI.Offset, U);
740 ReBasesNum++;
741 }
742
743 Base->setDebugLoc(DILocation::getMergedLocation(Base->getDebugLoc(), U.Inst->getDebugLoc()));
744 }
745 }
746 UsesNum = Uses;
747
748 // Use the same debug location as the last user of the constant.
749 assert(!Base->use_empty() && "The use list is empty!?")(static_cast <bool> (!Base->use_empty() && "The use list is empty!?"
) ? void (0) : __assert_fail ("!Base->use_empty() && \"The use list is empty!?\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 749, __extension__ __PRETTY_FUNCTION__))
;
750 assert(isa<Instruction>(Base->user_back()) &&(static_cast <bool> (isa<Instruction>(Base->user_back
()) && "All uses should be instructions.") ? void (0)
: __assert_fail ("isa<Instruction>(Base->user_back()) && \"All uses should be instructions.\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 751, __extension__ __PRETTY_FUNCTION__))
751 "All uses should be instructions.")(static_cast <bool> (isa<Instruction>(Base->user_back
()) && "All uses should be instructions.") ? void (0)
: __assert_fail ("isa<Instruction>(Base->user_back()) && \"All uses should be instructions.\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 751, __extension__ __PRETTY_FUNCTION__))
;
752 }
753 (void)UsesNum;
754 (void)ReBasesNum;
755 // Expect all uses are rebased after rebase is done.
756 assert(UsesNum == ReBasesNum && "Not all uses are rebased")(static_cast <bool> (UsesNum == ReBasesNum && "Not all uses are rebased"
) ? void (0) : __assert_fail ("UsesNum == ReBasesNum && \"Not all uses are rebased\""
, "/build/llvm-toolchain-snapshot-7~svn338205/lib/Transforms/Scalar/ConstantHoisting.cpp"
, 756, __extension__ __PRETTY_FUNCTION__))
;
757
758 NumConstantsHoisted++;
759
760 // Base constant is also included in ConstInfo.RebasedConstants, so
761 // deduct 1 from ConstInfo.RebasedConstants.size().
762 NumConstantsRebased = ConstInfo.RebasedConstants.size() - 1;
763
764 MadeChange = true;
765 }
766 return MadeChange;
767}
768
769/// Check all cast instructions we made a copy of and remove them if they
770/// have no more users.
771void ConstantHoistingPass::deleteDeadCastInst() const {
772 for (auto const &I : ClonedCastMap)
773 if (I.first->use_empty())
774 I.first->eraseFromParent();
775}
776
777/// Optimize expensive integer constants in the given function.
778bool ConstantHoistingPass::runImpl(Function &Fn, TargetTransformInfo &TTI,
779 DominatorTree &DT, BlockFrequencyInfo *BFI,
780 BasicBlock &Entry) {
781 this->TTI = &TTI;
782 this->DT = &DT;
783 this->BFI = BFI;
784 this->Entry = &Entry;
785 // Collect all constant candidates.
786 collectConstantCandidates(Fn);
787
788 // There are no constant candidates to worry about.
789 if (ConstCandVec.empty())
4
Assuming the condition is false
5
Taking false branch
790 return false;
791
792 // Combine constants that can be easily materialized with an add from a common
793 // base constant.
794 findBaseConstants();
795
796 // There are no constants to emit.
797 if (ConstantVec.empty())
6
Taking false branch
798 return false;
799
800 // Finally hoist the base constant and emit materialization code for dependent
801 // constants.
802 bool MadeChange = emitBaseConstants();
7
Calling 'ConstantHoistingPass::emitBaseConstants'
803
804 // Cleanup dead instructions.
805 deleteDeadCastInst();
806
807 return MadeChange;
808}
809
810PreservedAnalyses ConstantHoistingPass::run(Function &F,
811 FunctionAnalysisManager &AM) {
812 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
813 auto &TTI = AM.getResult<TargetIRAnalysis>(F);
814 auto BFI = ConstHoistWithBlockFrequency
1
Assuming the condition is false
2
'?' condition is false
815 ? &AM.getResult<BlockFrequencyAnalysis>(F)
816 : nullptr;
817 if (!runImpl(F, TTI, DT, BFI, F.getEntryBlock()))
3
Calling 'ConstantHoistingPass::runImpl'
818 return PreservedAnalyses::all();
819
820 PreservedAnalyses PA;
821 PA.preserveSet<CFGAnalyses>();
822 return PA;
823}