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/IR/Function.h"
17#include "llvm/IR/Instructions.h"
18#include "llvm/IR/Intrinsics.h"
19#include "llvm/IR/PatternMatch.h"
20#include "llvm/Transforms/Scalar.h"
21
22using namespace llvm;
23
24static bool lowerWidenableCondition(Function &F) {
25 // Check if we can cheaply rule out the possibility of not having any work to
26 // do.
27 auto *WCDecl = Intrinsic::getDeclarationIfExists(
28 M: F.getParent(), id: Intrinsic::experimental_widenable_condition);
29 if (!WCDecl || WCDecl->use_empty())
30 return false;
31
32 using namespace llvm::PatternMatch;
33 SmallVector<CallInst *, 8> ToLower;
34 // Traverse through the users of WCDecl.
35 // This is presumably cheaper than traversing all instructions in the
36 // function.
37 for (auto *U : WCDecl->users())
38 if (auto *CI = dyn_cast<CallInst>(Val: U))
39 if (CI->getFunction() == &F)
40 ToLower.push_back(Elt: CI);
41
42 if (ToLower.empty())
43 return false;
44
45 for (auto *CI : ToLower) {
46 CI->replaceAllUsesWith(V: ConstantInt::getTrue(Context&: CI->getContext()));
47 CI->eraseFromParent();
48 }
49 return true;
50}
51
52PreservedAnalyses LowerWidenableConditionPass::run(Function &F,
53 FunctionAnalysisManager &AM) {
54 if (lowerWidenableCondition(F))
55 return PreservedAnalyses::none();
56
57 return PreservedAnalyses::all();
58}
59