Chandler Carruth | 5820d62 | 2011-10-16 22:15:07 +0000 | [diff] [blame] | 1 | //===- LowerExpectIntrinsic.cpp - Lower expect intrinsic ------------------===// |
| 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 lowers the 'expect' intrinsic to LLVM metadata. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 14 | #define DEBUG_TYPE "lower-expect-intrinsic" |
Chandler Carruth | d04a8d4 | 2012-12-03 16:50:05 +0000 | [diff] [blame] | 15 | #include "llvm/Transforms/Scalar.h" |
| 16 | #include "llvm/ADT/Statistic.h" |
Chandler Carruth | 0b8c9a8 | 2013-01-02 11:36:10 +0000 | [diff] [blame^] | 17 | #include "llvm/IR/BasicBlock.h" |
| 18 | #include "llvm/IR/Constants.h" |
| 19 | #include "llvm/IR/Function.h" |
| 20 | #include "llvm/IR/Instructions.h" |
| 21 | #include "llvm/IR/Intrinsics.h" |
| 22 | #include "llvm/IR/LLVMContext.h" |
| 23 | #include "llvm/IR/MDBuilder.h" |
| 24 | #include "llvm/IR/Metadata.h" |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 25 | #include "llvm/Pass.h" |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 26 | #include "llvm/Support/CommandLine.h" |
| 27 | #include "llvm/Support/Debug.h" |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 28 | #include <vector> |
| 29 | |
| 30 | using namespace llvm; |
| 31 | |
| 32 | STATISTIC(IfHandled, "Number of 'expect' intrinsic intructions handled"); |
| 33 | |
| 34 | static cl::opt<uint32_t> |
| 35 | LikelyBranchWeight("likely-branch-weight", cl::Hidden, cl::init(64), |
| 36 | cl::desc("Weight of the branch likely to be taken (default = 64)")); |
| 37 | static cl::opt<uint32_t> |
| 38 | UnlikelyBranchWeight("unlikely-branch-weight", cl::Hidden, cl::init(4), |
| 39 | cl::desc("Weight of the branch unlikely to be taken (default = 4)")); |
| 40 | |
| 41 | namespace { |
| 42 | |
| 43 | class LowerExpectIntrinsic : public FunctionPass { |
| 44 | |
| 45 | bool HandleSwitchExpect(SwitchInst *SI); |
| 46 | |
| 47 | bool HandleIfExpect(BranchInst *BI); |
| 48 | |
| 49 | public: |
| 50 | static char ID; |
| 51 | LowerExpectIntrinsic() : FunctionPass(ID) { |
| 52 | initializeLowerExpectIntrinsicPass(*PassRegistry::getPassRegistry()); |
| 53 | } |
| 54 | |
| 55 | bool runOnFunction(Function &F); |
| 56 | }; |
| 57 | } |
| 58 | |
| 59 | |
| 60 | bool LowerExpectIntrinsic::HandleSwitchExpect(SwitchInst *SI) { |
| 61 | CallInst *CI = dyn_cast<CallInst>(SI->getCondition()); |
| 62 | if (!CI) |
| 63 | return false; |
| 64 | |
| 65 | Function *Fn = CI->getCalledFunction(); |
| 66 | if (!Fn || Fn->getIntrinsicID() != Intrinsic::expect) |
| 67 | return false; |
| 68 | |
| 69 | Value *ArgValue = CI->getArgOperand(0); |
| 70 | ConstantInt *ExpectedValue = dyn_cast<ConstantInt>(CI->getArgOperand(1)); |
| 71 | if (!ExpectedValue) |
| 72 | return false; |
| 73 | |
Stepan Dyatkovskiy | c10fa6c | 2012-03-08 07:06:20 +0000 | [diff] [blame] | 74 | SwitchInst::CaseIt Case = SI->findCaseValue(ExpectedValue); |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 75 | unsigned n = SI->getNumCases(); // +1 for default case. |
| 76 | std::vector<uint32_t> Weights(n + 1); |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 77 | |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 78 | Weights[0] = Case == SI->case_default() ? LikelyBranchWeight |
| 79 | : UnlikelyBranchWeight; |
| 80 | for (unsigned i = 0; i != n; ++i) |
| 81 | Weights[i + 1] = i == Case.getCaseIndex() ? LikelyBranchWeight |
| 82 | : UnlikelyBranchWeight; |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 83 | |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 84 | SI->setMetadata(LLVMContext::MD_prof, |
| 85 | MDBuilder(CI->getContext()).createBranchWeights(Weights)); |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 86 | |
| 87 | SI->setCondition(ArgValue); |
| 88 | return true; |
| 89 | } |
| 90 | |
| 91 | |
| 92 | bool LowerExpectIntrinsic::HandleIfExpect(BranchInst *BI) { |
| 93 | if (BI->isUnconditional()) |
| 94 | return false; |
| 95 | |
| 96 | // Handle non-optimized IR code like: |
| 97 | // %expval = call i64 @llvm.expect.i64.i64(i64 %conv1, i64 1) |
| 98 | // %tobool = icmp ne i64 %expval, 0 |
| 99 | // br i1 %tobool, label %if.then, label %if.end |
| 100 | |
| 101 | ICmpInst *CmpI = dyn_cast<ICmpInst>(BI->getCondition()); |
| 102 | if (!CmpI || CmpI->getPredicate() != CmpInst::ICMP_NE) |
| 103 | return false; |
| 104 | |
| 105 | CallInst *CI = dyn_cast<CallInst>(CmpI->getOperand(0)); |
| 106 | if (!CI) |
| 107 | return false; |
| 108 | |
| 109 | Function *Fn = CI->getCalledFunction(); |
| 110 | if (!Fn || Fn->getIntrinsicID() != Intrinsic::expect) |
| 111 | return false; |
| 112 | |
| 113 | Value *ArgValue = CI->getArgOperand(0); |
| 114 | ConstantInt *ExpectedValue = dyn_cast<ConstantInt>(CI->getArgOperand(1)); |
| 115 | if (!ExpectedValue) |
| 116 | return false; |
| 117 | |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 118 | MDBuilder MDB(CI->getContext()); |
| 119 | MDNode *Node; |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 120 | |
| 121 | // If expect value is equal to 1 it means that we are more likely to take |
| 122 | // branch 0, in other case more likely is branch 1. |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 123 | if (ExpectedValue->isOne()) |
| 124 | Node = MDB.createBranchWeights(LikelyBranchWeight, UnlikelyBranchWeight); |
| 125 | else |
| 126 | Node = MDB.createBranchWeights(UnlikelyBranchWeight, LikelyBranchWeight); |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 127 | |
Benjamin Kramer | 937338c | 2012-05-26 13:59:43 +0000 | [diff] [blame] | 128 | BI->setMetadata(LLVMContext::MD_prof, Node); |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 129 | |
| 130 | CmpI->setOperand(0, ArgValue); |
| 131 | return true; |
| 132 | } |
| 133 | |
| 134 | |
| 135 | bool LowerExpectIntrinsic::runOnFunction(Function &F) { |
| 136 | for (Function::iterator I = F.begin(), E = F.end(); I != E;) { |
| 137 | BasicBlock *BB = I++; |
| 138 | |
| 139 | // Create "block_weights" metadata. |
| 140 | if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) { |
| 141 | if (HandleIfExpect(BI)) |
| 142 | IfHandled++; |
| 143 | } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) { |
| 144 | if (HandleSwitchExpect(SI)) |
| 145 | IfHandled++; |
| 146 | } |
| 147 | |
| 148 | // remove llvm.expect intrinsics. |
| 149 | for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); |
| 150 | BI != BE; ) { |
| 151 | CallInst *CI = dyn_cast<CallInst>(BI++); |
| 152 | if (!CI) |
| 153 | continue; |
| 154 | |
| 155 | Function *Fn = CI->getCalledFunction(); |
Jakub Staszak | 447c40c | 2011-07-06 23:50:16 +0000 | [diff] [blame] | 156 | if (Fn && Fn->getIntrinsicID() == Intrinsic::expect) { |
| 157 | Value *Exp = CI->getArgOperand(0); |
| 158 | CI->replaceAllUsesWith(Exp); |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 159 | CI->eraseFromParent(); |
Jakub Staszak | 447c40c | 2011-07-06 23:50:16 +0000 | [diff] [blame] | 160 | } |
Jakub Staszak | 9da9934 | 2011-07-06 18:22:43 +0000 | [diff] [blame] | 161 | } |
| 162 | } |
| 163 | |
| 164 | return false; |
| 165 | } |
| 166 | |
| 167 | |
| 168 | char LowerExpectIntrinsic::ID = 0; |
| 169 | INITIALIZE_PASS(LowerExpectIntrinsic, "lower-expect", "Lower 'expect' " |
| 170 | "Intrinsics", false, false) |
| 171 | |
| 172 | FunctionPass *llvm::createLowerExpectIntrinsicPass() { |
| 173 | return new LowerExpectIntrinsic(); |
| 174 | } |