1 //===- InstSimplifyPass.cpp -----------------------------------------------===//
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 #include "llvm/Transforms/Scalar/InstSimplifyPass.h"
10 #include "llvm/ADT/SmallPtrSet.h"
11 #include "llvm/ADT/Statistic.h"
12 #include "llvm/Analysis/AssumptionCache.h"
13 #include "llvm/Analysis/InstructionSimplify.h"
14 #include "llvm/Analysis/OptimizationRemarkEmitter.h"
15 #include "llvm/Analysis/TargetLibraryInfo.h"
16 #include "llvm/IR/Dominators.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/InitializePasses.h"
19 #include "llvm/Pass.h"
20 #include "llvm/Transforms/Scalar.h"
21 #include "llvm/Transforms/Utils/Local.h"
22
23 using namespace llvm;
24
25 #define DEBUG_TYPE "instsimplify"
26
27 STATISTIC(NumSimplified, "Number of redundant instructions removed");
28
runImpl(Function & F,const SimplifyQuery & SQ,OptimizationRemarkEmitter * ORE)29 static bool runImpl(Function &F, const SimplifyQuery &SQ,
30 OptimizationRemarkEmitter *ORE) {
31 SmallPtrSet<const Instruction *, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
32 bool Changed = false;
33
34 do {
35 for (BasicBlock &BB : F) {
36 // Unreachable code can take on strange forms that we are not prepared to
37 // handle. For example, an instruction may have itself as an operand.
38 if (!SQ.DT->isReachableFromEntry(&BB))
39 continue;
40
41 SmallVector<WeakTrackingVH, 8> DeadInstsInBB;
42 for (Instruction &I : BB) {
43 // The first time through the loop, ToSimplify is empty and we try to
44 // simplify all instructions. On later iterations, ToSimplify is not
45 // empty and we only bother simplifying instructions that are in it.
46 if (!ToSimplify->empty() && !ToSimplify->count(&I))
47 continue;
48
49 // Don't waste time simplifying dead/unused instructions.
50 if (isInstructionTriviallyDead(&I)) {
51 DeadInstsInBB.push_back(&I);
52 Changed = true;
53 } else if (!I.use_empty()) {
54 if (Value *V = simplifyInstruction(&I, SQ, ORE)) {
55 // Mark all uses for resimplification next time round the loop.
56 for (User *U : I.users())
57 Next->insert(cast<Instruction>(U));
58 I.replaceAllUsesWith(V);
59 ++NumSimplified;
60 Changed = true;
61 // A call can get simplified, but it may not be trivially dead.
62 if (isInstructionTriviallyDead(&I))
63 DeadInstsInBB.push_back(&I);
64 }
65 }
66 }
67 RecursivelyDeleteTriviallyDeadInstructions(DeadInstsInBB, SQ.TLI);
68 }
69
70 // Place the list of instructions to simplify on the next loop iteration
71 // into ToSimplify.
72 std::swap(ToSimplify, Next);
73 Next->clear();
74 } while (!ToSimplify->empty());
75
76 return Changed;
77 }
78
79 namespace {
80 struct InstSimplifyLegacyPass : public FunctionPass {
81 static char ID; // Pass identification, replacement for typeid
InstSimplifyLegacyPass__anonf2f0630c0111::InstSimplifyLegacyPass82 InstSimplifyLegacyPass() : FunctionPass(ID) {
83 initializeInstSimplifyLegacyPassPass(*PassRegistry::getPassRegistry());
84 }
85
getAnalysisUsage__anonf2f0630c0111::InstSimplifyLegacyPass86 void getAnalysisUsage(AnalysisUsage &AU) const override {
87 AU.setPreservesCFG();
88 AU.addRequired<DominatorTreeWrapperPass>();
89 AU.addRequired<AssumptionCacheTracker>();
90 AU.addRequired<TargetLibraryInfoWrapperPass>();
91 AU.addRequired<OptimizationRemarkEmitterWrapperPass>();
92 }
93
94 /// Remove instructions that simplify.
runOnFunction__anonf2f0630c0111::InstSimplifyLegacyPass95 bool runOnFunction(Function &F) override {
96 if (skipFunction(F))
97 return false;
98
99 const DominatorTree *DT =
100 &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
101 const TargetLibraryInfo *TLI =
102 &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
103 AssumptionCache *AC =
104 &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
105 OptimizationRemarkEmitter *ORE =
106 &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
107 const DataLayout &DL = F.getParent()->getDataLayout();
108 const SimplifyQuery SQ(DL, TLI, DT, AC);
109 return runImpl(F, SQ, ORE);
110 }
111 };
112 } // namespace
113
114 char InstSimplifyLegacyPass::ID = 0;
115 INITIALIZE_PASS_BEGIN(InstSimplifyLegacyPass, "instsimplify",
116 "Remove redundant instructions", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)117 INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
118 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
119 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
120 INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass)
121 INITIALIZE_PASS_END(InstSimplifyLegacyPass, "instsimplify",
122 "Remove redundant instructions", false, false)
123
124 // Public interface to the simplify instructions pass.
125 FunctionPass *llvm::createInstSimplifyLegacyPass() {
126 return new InstSimplifyLegacyPass();
127 }
128
run(Function & F,FunctionAnalysisManager & AM)129 PreservedAnalyses InstSimplifyPass::run(Function &F,
130 FunctionAnalysisManager &AM) {
131 auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
132 auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
133 auto &AC = AM.getResult<AssumptionAnalysis>(F);
134 auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F);
135 const DataLayout &DL = F.getParent()->getDataLayout();
136 const SimplifyQuery SQ(DL, &TLI, &DT, &AC);
137 bool Changed = runImpl(F, SQ, &ORE);
138 if (!Changed)
139 return PreservedAnalyses::all();
140
141 PreservedAnalyses PA;
142 PA.preserveSet<CFGAnalyses>();
143 return PA;
144 }
145