LowerWidenableCondition.cpp revision 360784 
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
29using namespace llvm;
30
31namespace {
32struct 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
43static 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
67bool LowerWidenableConditionLegacyPass::runOnFunction(Function &F) {
68  return lowerWidenableCondition(F);
69}
70
71char LowerWidenableConditionLegacyPass::ID = 0;
72INITIALIZE_PASS(LowerWidenableConditionLegacyPass, "lower-widenable-condition",
73                "Lower the widenable condition to default true value", false,
74                false)
75
76Pass *llvm::createLowerWidenableConditionPass() {
77  return new LowerWidenableConditionLegacyPass();
78}
79
80PreservedAnalyses LowerWidenableConditionPass::run(Function &F,
81                                               FunctionAnalysisManager &AM) {
82  if (lowerWidenableCondition(F))
83    return PreservedAnalyses::none();
84
85  return PreservedAnalyses::all();
86}
87