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llvm-mirror/lib/Analysis/GuardUtils.cpp
Philip Reames 07eb26281f [WideableCond] Fix a nasty bug in detection of "explicit guards"
The code was failing to actually check for the presence of the call to widenable_condition.  The whole point of specifying the widenable_condition intrinsic was allowing widening transforms.  A normal branch is not widenable.  A normal branch leading to a deopt is not widenable (in general).

I added a test case via LoopPredication, but GuardWidening has an analogous bug.  Those are the only two passes actually using this utility just yet. Noticed while working on LoopPredication for non-widenable branches; POC in D60111.

llvm-svn: 357493
2019-04-02 16:51:43 +00:00

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//===-- GuardUtils.cpp - Utils for work with guards -------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// Utils that are used to perform analyzes related to guards and their
// conditions.
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/IR/PatternMatch.h"
using namespace llvm;
bool llvm::isGuard(const User *U) {
using namespace llvm::PatternMatch;
return match(U, m_Intrinsic<Intrinsic::experimental_guard>());
}
bool llvm::isGuardAsWidenableBranch(const User *U) {
Value *Condition, *WidenableCondition;
BasicBlock *GuardedBB, *DeoptBB;
if (!parseWidenableBranch(U, Condition, WidenableCondition, GuardedBB,
DeoptBB))
return false;
using namespace llvm::PatternMatch;
for (auto &Insn : *DeoptBB) {
if (match(&Insn, m_Intrinsic<Intrinsic::experimental_deoptimize>()))
return true;
if (Insn.mayHaveSideEffects())
return false;
}
return false;
}
bool llvm::parseWidenableBranch(const User *U, Value *&Condition,
Value *&WidenableCondition,
BasicBlock *&IfTrueBB, BasicBlock *&IfFalseBB) {
using namespace llvm::PatternMatch;
if (!match(U, m_Br(m_And(m_Value(Condition), m_Value(WidenableCondition)),
IfTrueBB, IfFalseBB)))
return false;
// TODO: At the moment, we only recognize the branch if the WC call in this
// specific position. We should generalize!
return match(WidenableCondition,
m_Intrinsic<Intrinsic::experimental_widenable_condition>());
}