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/Analysis/GuardUtils.h" 18 #include "llvm/IR/Function.h" 19 #include "llvm/IR/InstIterator.h" 20 #include "llvm/IR/Instructions.h" 21 #include "llvm/IR/Intrinsics.h" 22 #include "llvm/IR/Module.h" 23 #include "llvm/InitializePasses.h" 24 #include "llvm/Pass.h" 25 #include "llvm/Transforms/Scalar.h" 26 #include "llvm/Transforms/Utils/GuardUtils.h" 27 28 using namespace llvm; 29 30 static bool lowerGuardIntrinsic(Function &F) { 31 // Check if we can cheaply rule out the possibility of not having any work to 32 // do. 33 auto *GuardDecl = F.getParent()->getFunction( 34 Intrinsic::getName(Intrinsic::experimental_guard)); 35 if (!GuardDecl || GuardDecl->use_empty()) 36 return false; 37 38 SmallVector<CallInst *, 8> ToLower; 39 // Traverse through the users of GuardDecl. 40 // This is presumably cheaper than traversing all instructions in the 41 // function. 42 for (auto *U : GuardDecl->users()) 43 if (auto *CI = dyn_cast<CallInst>(U)) 44 if (CI->getFunction() == &F) 45 ToLower.push_back(CI); 46 47 if (ToLower.empty()) 48 return false; 49 50 auto *DeoptIntrinsic = Intrinsic::getDeclaration( 51 F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()}); 52 DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv()); 53 54 for (auto *CI : ToLower) { 55 makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false); 56 CI->eraseFromParent(); 57 } 58 59 return true; 60 } 61 62 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F, 63 FunctionAnalysisManager &AM) { 64 if (lowerGuardIntrinsic(F)) 65 return PreservedAnalyses::none(); 66 67 return PreservedAnalyses::all(); 68 } 69