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Do not remove empty lifetime.start/lifetime.end ranges

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Summary:
Asan stack-use-after-scope check should poison alloca even if there is
no access between start and end.

This is possible for code like this:
for (int i = 0; i < 3; i++) {
  int x;
  p = &x;
}

"Loop Invariant Code Motion" will move "p = &x;" out of the loop, making
start/end range empty.

PR27453

Reviewers: eugenis

Differential Revision: https://reviews.llvm.org/D22842

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277072 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Vitaly Buka 2016-07-28 22:59:03 +00:00
parent 3ec908dfba
commit 2328afe0b5
2 changed files with 40 additions and 0 deletions
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5
lib/Transforms/InstCombine/InstCombineCalls.cpp
View File

@ -2243,6 +2243,11 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
break;
}
case Intrinsic::lifetime_start:
// Asan needs to poison memory to detect invalid access which is possible
// even for empty lifetime range.
if (II->getFunction()->hasFnAttribute(Attribute::SanitizeAddress))
break;
if (removeTriviallyEmptyRange(*II, Intrinsic::lifetime_start,
Intrinsic::lifetime_end, *this))
return nullptr;

35
test/Transforms/InstCombine/lifetime-asan.ll Normal file
View File

@ -0,0 +1,35 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
declare void @llvm.lifetime.start(i64, i8* nocapture)
declare void @llvm.lifetime.end(i64, i8* nocapture)
declare void @foo(i8* nocapture)
define void @asan() sanitize_address {
entry:
; CHECK-LABEL: @asan(
%text = alloca i8, align 1
call void @llvm.lifetime.start(i64 1, i8* %text)
call void @llvm.lifetime.end(i64 1, i8* %text)
; CHECK: call void @llvm.lifetime.start
; CHECK-NEXT: call void @llvm.lifetime.end
call void @foo(i8* %text) ; Keep alloca alive
ret void
}
define void @no_asan() {
entry:
; CHECK-LABEL: @no_asan(
%text = alloca i8, align 1
call void @llvm.lifetime.start(i64 1, i8* %text)
call void @llvm.lifetime.end(i64 1, i8* %text)
; CHECK-NO: call void @llvm.lifetime
call void @foo(i8* %text) ; Keep alloca alive
ret void
}