lib/Transforms/Scalar/LowerWidenableCondition.cpp

   1 //===- LowerWidenableCondition.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.widenable.condition intrinsic to default value
  10 // which is i1 true.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Transforms/Scalar/LowerWidenableCondition.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/Analysis/GuardUtils.h"
  17 #include "llvm/IR/BasicBlock.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/IR/PatternMatch.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 LowerWidenableConditionLegacyPass : public FunctionPass {
  32   static char ID;
  33   LowerWidenableConditionLegacyPass() : FunctionPass(ID) {
  34     initializeLowerWidenableConditionLegacyPassPass(
  35         *PassRegistry::getPassRegistry());
  36   }
  37
  38   bool runOnFunction(Function &F) override;
  39 };
  40 }
  41
  42 static bool lowerWidenableCondition(Function &F) {
  43   // Check if we can cheaply rule out the possibility of not having any work to
  44   // do.
  45   auto *WCDecl = F.getParent()->getFunction(
  46       Intrinsic::getName(Intrinsic::experimental_widenable_condition));
  47   if (!WCDecl || WCDecl->use_empty())
  48     return false;
  49
  50   using namespace llvm::PatternMatch;
  51   SmallVector<CallInst *, 8> ToLower;
  52   for (auto &I : instructions(F))
  53     if (match(&I, m_Intrinsic<Intrinsic::experimental_widenable_condition>()))
  54       ToLower.push_back(cast<CallInst>(&I));
  55
  56   if (ToLower.empty())
  57     return false;
  58
  59   for (auto *CI : ToLower) {
  60     CI->replaceAllUsesWith(ConstantInt::getTrue(CI->getContext()));
  61     CI->eraseFromParent();
  62   }
  63   return true;
  64 }
  65
  66 bool LowerWidenableConditionLegacyPass::runOnFunction(Function &F) {
  67   return lowerWidenableCondition(F);
  68 }
  69
  70 char LowerWidenableConditionLegacyPass::ID = 0;
  71 INITIALIZE_PASS(LowerWidenableConditionLegacyPass, "lower-widenable-condition",
  72                 "Lower the widenable condition to default true value", false,
  73                 false)
  74
  75 Pass *llvm::createLowerWidenableConditionPass() {
  76   return new LowerWidenableConditionLegacyPass();
  77 }
  78
  79 PreservedAnalyses LowerWidenableConditionPass::run(Function &F,
  80                                                FunctionAnalysisManager &AM) {
  81   if (lowerWidenableCondition(F))
  82     return PreservedAnalyses::none();
  83
  84   return PreservedAnalyses::all();
  85 }