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[tsan] Do not instrument accesses to the gcov counters array

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There is a known intended race here. This is a follow-up to r264805,
which disabled tsan instrumentation for updates to instrprof counters.
For more background on this please see the discussion in D18164.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273202 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Vedant Kumar 2016-06-20 21:24:26 +00:00
parent 832e25415d
commit bdba755f85
2 changed files with 12 additions and 0 deletions
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4
lib/Transforms/Instrumentation/ThreadSanitizer.cpp
View File

@ -271,6 +271,10 @@ static bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
/*AddSegment=*/false)))
return false;
}
// Check if the global is in the GCOV counters array.
if (GV->getName() == "__llvm_gcov_ctr")
return false;
}
return true;
}

8
test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
View File

@ -1,5 +1,6 @@
; This test checks that we are not instrumenting unwanted acesses to globals:
; - Instruction profiler counter instrumentation has known intended races.
; - The gcov counters array has a known intended race.
;
; RUN: opt < %s -tsan -S | FileCheck %s
@ -10,11 +11,18 @@ target triple = "x86_64-apple-macosx10.9"
@__profc_test_bitcast = private global [2 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
@__profc_test_bitcast_foo = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
@__llvm_gcov_ctr = internal global [1 x i64] zeroinitializer
define i32 @test_gep() sanitize_thread {
entry:
%pgocount = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_gep, i64 0, i64 0)
%0 = add i64 %pgocount, 1
store i64 %0, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_gep, i64 0, i64 0)
%gcovcount = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__llvm_gcov_ctr, i64 0, i64 0)
%1 = add i64 %gcovcount, 1
store i64 %1, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__llvm_gcov_ctr, i64 0, i64 0)
ret i32 1
}