1 //===- LowerWidenableCondition.cpp - Lower the guard intrinsic ---------------===// 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 // This pass lowers the llvm.widenable.condition intrinsic to default value 10 // which is i1 true. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Transforms/Scalar/LowerWidenableCondition.h" 15 #include "llvm/ADT/SmallVector.h" 16 #include "llvm/IR/Function.h" 17 #include "llvm/IR/InstIterator.h" 18 #include "llvm/IR/Instructions.h" 19 #include "llvm/IR/Intrinsics.h" 20 #include "llvm/IR/Module.h" 21 #include "llvm/IR/PatternMatch.h" 22 #include "llvm/InitializePasses.h" 23 #include "llvm/Pass.h" 24 #include "llvm/Transforms/Scalar.h" 25 26 using namespace llvm; 27 28 namespace { 29 struct LowerWidenableConditionLegacyPass : public FunctionPass { 30 static char ID; 31 LowerWidenableConditionLegacyPass() : FunctionPass(ID) { 32 initializeLowerWidenableConditionLegacyPassPass( 33 *PassRegistry::getPassRegistry()); 34 } 35 36 bool runOnFunction(Function &F) override; 37 }; 38 } 39 40 static bool lowerWidenableCondition(Function &F) { 41 // Check if we can cheaply rule out the possibility of not having any work to 42 // do. 43 auto *WCDecl = F.getParent()->getFunction( 44 Intrinsic::getName(Intrinsic::experimental_widenable_condition)); 45 if (!WCDecl || WCDecl->use_empty()) 46 return false; 47 48 using namespace llvm::PatternMatch; 49 SmallVector<CallInst *, 8> ToLower; 50 // Traverse through the users of WCDecl. 51 // This is presumably cheaper than traversing all instructions in the 52 // function. 53 for (auto *U : WCDecl->users()) 54 if (auto *CI = dyn_cast<CallInst>(U)) 55 if (CI->getFunction() == &F) 56 ToLower.push_back(CI); 57 58 if (ToLower.empty()) 59 return false; 60 61 for (auto *CI : ToLower) { 62 CI->replaceAllUsesWith(ConstantInt::getTrue(CI->getContext())); 63 CI->eraseFromParent(); 64 } 65 return true; 66 } 67 68 bool LowerWidenableConditionLegacyPass::runOnFunction(Function &F) { 69 return lowerWidenableCondition(F); 70 } 71 72 char LowerWidenableConditionLegacyPass::ID = 0; 73 INITIALIZE_PASS(LowerWidenableConditionLegacyPass, "lower-widenable-condition", 74 "Lower the widenable condition to default true value", false, 75 false) 76 77 Pass *llvm::createLowerWidenableConditionPass() { 78 return new LowerWidenableConditionLegacyPass(); 79 } 80 81 PreservedAnalyses LowerWidenableConditionPass::run(Function &F, 82 FunctionAnalysisManager &AM) { 83 if (lowerWidenableCondition(F)) 84 return PreservedAnalyses::none(); 85 86 return PreservedAnalyses::all(); 87 } 88