lib/Transforms/Scalar/LowerGuardIntrinsic.cpp

   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 }