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/BasicBlock.h" 19 #include "llvm/IR/Function.h" 20 #include "llvm/IR/InstIterator.h" 21 #include "llvm/IR/Instructions.h" 22 #include "llvm/IR/Intrinsics.h" 23 #include "llvm/IR/Module.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 namespace { 31 struct LowerGuardIntrinsicLegacyPass : public FunctionPass { 32 static char ID; 33 LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) { 34 initializeLowerGuardIntrinsicLegacyPassPass( 35 *PassRegistry::getPassRegistry()); 36 } 37 38 bool runOnFunction(Function &F) override; 39 }; 40 } 41 42 static bool lowerGuardIntrinsic(Function &F) { 43 // Check if we can cheaply rule out the possibility of not having any work to 44 // do. 45 auto *GuardDecl = F.getParent()->getFunction( 46 Intrinsic::getName(Intrinsic::experimental_guard)); 47 if (!GuardDecl || GuardDecl->use_empty()) 48 return false; 49 50 SmallVector<CallInst *, 8> ToLower; 51 for (auto &I : instructions(F)) 52 if (isGuard(&I)) 53 ToLower.push_back(cast<CallInst>(&I)); 54 55 if (ToLower.empty()) 56 return false; 57 58 auto *DeoptIntrinsic = Intrinsic::getDeclaration( 59 F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()}); 60 DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv()); 61 62 for (auto *CI : ToLower) { 63 makeGuardControlFlowExplicit(DeoptIntrinsic, CI); 64 CI->eraseFromParent(); 65 } 66 67 return true; 68 } 69 70 bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) { 71 return lowerGuardIntrinsic(F); 72 } 73 74 char LowerGuardIntrinsicLegacyPass::ID = 0; 75 INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic", 76 "Lower the guard intrinsic to normal control flow", false, 77 false) 78 79 Pass *llvm::createLowerGuardIntrinsicPass() { 80 return new LowerGuardIntrinsicLegacyPass(); 81 } 82 83 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F, 84 FunctionAnalysisManager &AM) { 85 if (lowerGuardIntrinsic(F)) 86 return PreservedAnalyses::none(); 87 88 return PreservedAnalyses::all(); 89 } 90