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