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Don't speculate loads under ThreadSanitizer

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Summary:
Don't speculate loads under ThreadSanitizer.
This fixes https://code.google.com/p/thread-sanitizer/issues/detail?id=40
Also discussed here: http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-November/067929.html

Reviewers: chandlerc

Reviewed By: chandlerc

CC: llvm-commits, dvyukov

Differential Revision: http://llvm-reviews.chandlerc.com/D2227

llvm-svn: 195324
This commit is contained in:
Kostya Serebryany 2013-11-21 07:29:28 +00:00
parent 07a5510fa2
commit 1513e9969b
2 changed files with 43 additions and 1 deletions
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4
lib/Analysis/ValueTracking.cpp
View File

@ -2006,7 +2006,9 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V,
}
case Instruction::Load: {
const LoadInst *LI = cast<LoadInst>(Inst);
if (!LI->isUnordered())
if (!LI->isUnordered() ||
// Speculative load may create a race that did not exist in the source.
LI->getParent()->getParent()->hasFnAttribute(Attribute::SanitizeThread))
return false;
return LI->getPointerOperand()->isDereferenceablePointer();
}

40
test/Transforms/SimplifyCFG/no_speculative_loads_with_tsan.ll Normal file
View File

@ -0,0 +1,40 @@
; RUN: opt -simplifycfg -S %s | FileCheck %s
; Make sure we don't speculate loads under ThreadSanitizer.
@g = global i32 0, align 4
define i32 @TestNoTsan(i32 %cond) nounwind readonly uwtable {
entry:
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %return, label %if.then
if.then: ; preds = %entry
%0 = load i32* @g, align 4
br label %return
return: ; preds = %entry, %if.then
%retval = phi i32 [ %0, %if.then ], [ 0, %entry ]
ret i32 %retval
; CHECK-LABEL: @TestNoTsan
; CHECK: %[[LOAD:[^ ]*]] = load
; CHECK: select{{.*}}[[LOAD]]
; CHECK: ret i32
}
define i32 @TestTsan(i32 %cond) nounwind readonly uwtable sanitize_thread {
entry:
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %return, label %if.then
if.then: ; preds = %entry
%0 = load i32* @g, align 4
br label %return
return: ; preds = %entry, %if.then
%retval = phi i32 [ %0, %if.then ], [ 0, %entry ]
ret i32 %retval
; CHECK-LABEL: @TestTsan
; CHECK: br i1
; CHECK: load i32* @g
; CHECK: br label
; CHECK: ret i32
}