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//== MemoryTaggingSupport.cpp - helpers for memory tagging implementations ===//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file declares common infrastructure for HWAddressSanitizer and
// Aarch64StackTagging.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/MemoryTaggingSupport.h"
namespace llvm {
namespace {
bool maybeReachableFromEachOther(const SmallVectorImpl<IntrinsicInst *> &Insts,
const DominatorTree *DT, size_t MaxLifetimes) {
// If we have too many lifetime ends, give up, as the algorithm below is N^2.
if (Insts.size() > MaxLifetimes)
return true;
for (size_t I = 0; I < Insts.size(); ++I) {
for (size_t J = 0; J < Insts.size(); ++J) {
if (I == J)
continue;
if (isPotentiallyReachable(Insts[I], Insts[J], nullptr, DT))
return true;
}
}
return false;
}
} // namespace
bool isStandardLifetime(const SmallVectorImpl<IntrinsicInst *> &LifetimeStart,
const SmallVectorImpl<IntrinsicInst *> &LifetimeEnd,
const DominatorTree *DT, size_t MaxLifetimes) {
// An alloca that has exactly one start and end in every possible execution.
// If it has multiple ends, they have to be unreachable from each other, so
// at most one of them is actually used for each execution of the function.
return LifetimeStart.size() == 1 &&
(LifetimeEnd.size() == 1 ||
(LifetimeEnd.size() > 0 &&
!maybeReachableFromEachOther(LifetimeEnd, DT, MaxLifetimes)));
}
Instruction *getUntagLocationIfFunctionExit(Instruction &Inst) {
if (isa<ReturnInst>(Inst)) {
if (CallInst *CI = Inst.getParent()->getTerminatingMustTailCall())
return CI;
return &Inst;
}
if (isa<ResumeInst, CleanupReturnInst>(Inst)) {
return &Inst;
}
return nullptr;
}
} // namespace llvm
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