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/InitializePasses.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Transforms/Scalar.h" 27 #include "llvm/Transforms/Utils/GuardUtils.h" 28 29 using namespace llvm; 30 31 namespace { 32 struct LowerGuardIntrinsicLegacyPass : public FunctionPass { 33 static char ID; 34 LowerGuardIntrinsicLegacyPass() : FunctionPass(ID) { 35 initializeLowerGuardIntrinsicLegacyPassPass( 36 *PassRegistry::getPassRegistry()); 37 } 38 39 bool runOnFunction(Function &F) override; 40 }; 41 } 42 43 static bool lowerGuardIntrinsic(Function &F) { 44 // Check if we can cheaply rule out the possibility of not having any work to 45 // do. 46 auto *GuardDecl = F.getParent()->getFunction( 47 Intrinsic::getName(Intrinsic::experimental_guard)); 48 if (!GuardDecl || GuardDecl->use_empty()) 49 return false; 50 51 SmallVector<CallInst *, 8> ToLower; 52 for (auto &I : instructions(F)) 53 if (isGuard(&I)) 54 ToLower.push_back(cast<CallInst>(&I)); 55 56 if (ToLower.empty()) 57 return false; 58 59 auto *DeoptIntrinsic = Intrinsic::getDeclaration( 60 F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()}); 61 DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv()); 62 63 for (auto *CI : ToLower) { 64 makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false); 65 CI->eraseFromParent(); 66 } 67 68 return true; 69 } 70 71 bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) { 72 return lowerGuardIntrinsic(F); 73 } 74 75 char LowerGuardIntrinsicLegacyPass::ID = 0; 76 INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic", 77 "Lower the guard intrinsic to normal control flow", false, 78 false) 79 80 Pass *llvm::createLowerGuardIntrinsicPass() { 81 return new LowerGuardIntrinsicLegacyPass(); 82 } 83 84 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F, 85 FunctionAnalysisManager &AM) { 86 if (lowerGuardIntrinsic(F)) 87 return PreservedAnalyses::none(); 88 89 return PreservedAnalyses::all(); 90 } 91