llvm/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/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 LowerWidenableConditionLegacyPass : public FunctionPass {
  33   static char ID;
  34   LowerWidenableConditionLegacyPass() : FunctionPass(ID) {
  35     initializeLowerWidenableConditionLegacyPassPass(
  36         *PassRegistry::getPassRegistry());
  37   }
  38
  39   bool runOnFunction(Function &F) override;
  40 };
  41 }
  42
  43 static bool lowerWidenableCondition(Function &F) {
  44   // Check if we can cheaply rule out the possibility of not having any work to
  45   // do.
  46   auto *WCDecl = F.getParent()->getFunction(
  47       Intrinsic::getName(Intrinsic::experimental_widenable_condition));
  48   if (!WCDecl || WCDecl->use_empty())
  49     return false;
  50
  51   using namespace llvm::PatternMatch;
  52   SmallVector<CallInst *, 8> ToLower;
  53   for (auto &I : instructions(F))
  54     if (match(&I, m_Intrinsic<Intrinsic::experimental_widenable_condition>()))
  55       ToLower.push_back(cast<CallInst>(&I));
  56
  57   if (ToLower.empty())
  58     return false;
  59
  60   for (auto *CI : ToLower) {
  61     CI->replaceAllUsesWith(ConstantInt::getTrue(CI->getContext()));
  62     CI->eraseFromParent();
  63   }
  64   return true;
  65 }
  66
  67 bool LowerWidenableConditionLegacyPass::runOnFunction(Function &F) {
  68   return lowerWidenableCondition(F);
  69 }
  70
  71 char LowerWidenableConditionLegacyPass::ID = 0;
  72 INITIALIZE_PASS(LowerWidenableConditionLegacyPass, "lower-widenable-condition",
  73                 "Lower the widenable condition to default true value", false,
  74                 false)
  75
  76 Pass *llvm::createLowerWidenableConditionPass() {
  77   return new LowerWidenableConditionLegacyPass();
  78 }
  79
  80 PreservedAnalyses LowerWidenableConditionPass::run(Function &F,
  81                                                FunctionAnalysisManager &AM) {
  82   if (lowerWidenableCondition(F))
  83     return PreservedAnalyses::none();
  84
  85   return PreservedAnalyses::all();
  86 }