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llvm-mirror/test/Instrumentation/ThreadSanitizer/read_before_write.ll
Kostya Serebryany 01d463472d [tsan] compile-time instrumentation: do not instrument a read if
a write to the same temp follows in the same BB.
Also add stats printing.

On Spec CPU2006 this optimization saves roughly 4% of instrumented reads
(which is 3% of all instrumented accesses):
Writes            : 161216
Reads             : 446458
Reads-before-write: 18295

llvm-svn: 154418
2012-04-10 18:18:56 +00:00

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LLVM

; RUN: opt < %s -tsan -S | FileCheck %s
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
define void @IncrementMe(i32* nocapture %ptr) nounwind uwtable {
entry:
%0 = load i32* %ptr, align 4
%inc = add nsw i32 %0, 1
store i32 %inc, i32* %ptr, align 4
ret void
}
; CHECK: define void @IncrementMe
; CHECK-NOT: __tsan_read
; CHECK: __tsan_write
; CHECK: ret void
define void @IncrementMeWithCallInBetween(i32* nocapture %ptr) nounwind uwtable {
entry:
%0 = load i32* %ptr, align 4
%inc = add nsw i32 %0, 1
call void @foo()
store i32 %inc, i32* %ptr, align 4
ret void
}
; CHECK: define void @IncrementMeWithCallInBetween
; CHECK: __tsan_read
; CHECK: __tsan_write
; CHECK: ret void
declare void @foo()