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/Instructions.h" 18 #include "llvm/IR/Intrinsics.h" 19 #include "llvm/IR/PatternMatch.h" 20 #include "llvm/Transforms/Scalar.h" 21 22 using namespace llvm; 23 24 static bool lowerWidenableCondition(Function &F) { 25 // Check if we can cheaply rule out the possibility of not having any work to 26 // do. 27 auto *WCDecl = Intrinsic::getDeclarationIfExists( 28 F.getParent(), Intrinsic::experimental_widenable_condition); 29 if (!WCDecl || WCDecl->use_empty()) 30 return false; 31 32 using namespace llvm::PatternMatch; 33 SmallVector<CallInst *, 8> ToLower; 34 // Traverse through the users of WCDecl. 35 // This is presumably cheaper than traversing all instructions in the 36 // function. 37 for (auto *U : WCDecl->users()) 38 if (auto *CI = dyn_cast<CallInst>(U)) 39 if (CI->getFunction() == &F) 40 ToLower.push_back(CI); 41 42 if (ToLower.empty()) 43 return false; 44 45 for (auto *CI : ToLower) { 46 CI->replaceAllUsesWith(ConstantInt::getTrue(CI->getContext())); 47 CI->eraseFromParent(); 48 } 49 return true; 50 } 51 52 PreservedAnalyses LowerWidenableConditionPass::run(Function &F, 53 FunctionAnalysisManager &AM) { 54 if (lowerWidenableCondition(F)) 55 return PreservedAnalyses::none(); 56 57 return PreservedAnalyses::all(); 58 } 59