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 }
87