1 //===- LowerGuardIntrinsic.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.experimental.guard intrinsic to a conditional call 10 // to @llvm.experimental.deoptimize. Once this happens, the guard can no longer 11 // be widened. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/Transforms/Scalar/LowerGuardIntrinsic.h" 16 #include "llvm/ADT/SmallVector.h" 17 #include "llvm/IR/Function.h" 18 #include "llvm/IR/Instructions.h" 19 #include "llvm/IR/Intrinsics.h" 20 #include "llvm/Transforms/Utils/GuardUtils.h" 21 22 using namespace llvm; 23 24 static bool lowerGuardIntrinsic(Function &F) { 25 // Check if we can cheaply rule out the possibility of not having any work to 26 // do. 27 auto *GuardDecl = Intrinsic::getDeclarationIfExists( 28 F.getParent(), Intrinsic::experimental_guard); 29 if (!GuardDecl || GuardDecl->use_empty()) 30 return false; 31 32 SmallVector<CallInst *, 8> ToLower; 33 // Traverse through the users of GuardDecl. 34 // This is presumably cheaper than traversing all instructions in the 35 // function. 36 for (auto *U : GuardDecl->users()) 37 if (auto *CI = dyn_cast<CallInst>(U)) 38 if (CI->getFunction() == &F) 39 ToLower.push_back(CI); 40 41 if (ToLower.empty()) 42 return false; 43 44 auto *DeoptIntrinsic = Intrinsic::getOrInsertDeclaration( 45 F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()}); 46 DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv()); 47 48 for (auto *CI : ToLower) { 49 makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false); 50 CI->eraseFromParent(); 51 } 52 53 return true; 54 } 55 56 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F, 57 FunctionAnalysisManager &AM) { 58 if (lowerGuardIntrinsic(F)) 59 return PreservedAnalyses::none(); 60 61 return PreservedAnalyses::all(); 62 } 63