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 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 // Traverse through the users of GuardDecl. 52 // This is presumably cheaper than traversing all instructions in the 53 // function. 54 for (auto *U : GuardDecl->users()) 55 if (auto *CI = dyn_cast<CallInst>(U)) 56 if (CI->getFunction() == &F) 57 ToLower.push_back(CI); 58 59 if (ToLower.empty()) 60 return false; 61 62 auto *DeoptIntrinsic = Intrinsic::getDeclaration( 63 F.getParent(), Intrinsic::experimental_deoptimize, {F.getReturnType()}); 64 DeoptIntrinsic->setCallingConv(GuardDecl->getCallingConv()); 65 66 for (auto *CI : ToLower) { 67 makeGuardControlFlowExplicit(DeoptIntrinsic, CI, false); 68 CI->eraseFromParent(); 69 } 70 71 return true; 72 } 73 74 bool LowerGuardIntrinsicLegacyPass::runOnFunction(Function &F) { 75 return lowerGuardIntrinsic(F); 76 } 77 78 char LowerGuardIntrinsicLegacyPass::ID = 0; 79 INITIALIZE_PASS(LowerGuardIntrinsicLegacyPass, "lower-guard-intrinsic", 80 "Lower the guard intrinsic to normal control flow", false, 81 false) 82 83 Pass *llvm::createLowerGuardIntrinsicPass() { 84 return new LowerGuardIntrinsicLegacyPass(); 85 } 86 87 PreservedAnalyses LowerGuardIntrinsicPass::run(Function &F, 88 FunctionAnalysisManager &AM) { 89 if (lowerGuardIntrinsic(F)) 90 return PreservedAnalyses::none(); 91 92 return PreservedAnalyses::all(); 93 } 94