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[tsan] Do not instrument reads/writes to instruction profile counters.

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We have known races on profile counters, which can be reproduced by enabling
-fsanitize=thread and -fprofile-instr-generate simultaneously on a
multi-threaded program. This patch avoids reporting those races by not
instrumenting the reads and writes coming from the instruction profiler.

llvm-svn: 264805
This commit is contained in:
Anna Zaks 2016-03-29 23:19:40 +00:00
parent a6e8668e11
commit 83e4032a41
2 changed files with 58 additions and 1 deletions
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26
lib/Transforms/Instrumentation/ThreadSanitizer.cpp
View File

@ -36,6 +36,7 @@
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/MathExtras.h"
@ -243,6 +244,24 @@ static bool isVtableAccess(Instruction *I) {
return false;
}
// Do not instrument known races/"benign races" that come from compiler
// instrumentatin. The user has no way of suppressing them.
bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
// Peel off GEPs and BitCasts.
Addr = Addr->stripInBoundsOffsets();
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
if (GV->hasSection()) {
StringRef SectionName = GV->getSection();
// Check if the global is in the PGO counters section.
if (SectionName.endswith(getInstrProfCountersSectionName(
/*AddSegment=*/false)))
return false;
}
}
return true;
}
bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
// If this is a GEP, just analyze its pointer operand.
if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
@ -285,10 +304,15 @@ void ThreadSanitizer::chooseInstructionsToInstrument(
E = Local.rend(); It != E; ++It) {
Instruction *I = *It;
if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
WriteTargets.insert(Store->getPointerOperand());
Value *Addr = Store->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
WriteTargets.insert(Addr);
} else {
LoadInst *Load = cast<LoadInst>(I);
Value *Addr = Load->getPointerOperand();
if (!shouldInstrumentReadWriteFromAddress(Addr))
continue;
if (WriteTargets.count(Addr)) {
// We will write to this temp, so no reason to analyze the read.
NumOmittedReadsBeforeWrite++;

33
test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll Normal file
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@ -0,0 +1,33 @@
; This test checks that we are not instrumenting unwanted acesses to globals:
; - Instruction profiler counter instrumentation has known intended races.
;
; RUN: opt < %s -tsan -S | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10.9"
@__profc_test_gep = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
@__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
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)
ret i32 1
}
define i32 @test_bitcast() sanitize_thread {
entry:
%0 = load <2 x i64>, <2 x i64>* bitcast ([2 x i64]* @__profc_test_bitcast to <2 x i64>*), align 8
%.promoted5 = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_bitcast_foo, i64 0, i64 0), align 8
%1 = add i64 %.promoted5, 10
%2 = add <2 x i64> %0, <i64 1, i64 10>
store <2 x i64> %2, <2 x i64>* bitcast ([2 x i64]* @__profc_test_bitcast to <2 x i64>*), align 8
store i64 %1, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_bitcast_foo, i64 0, i64 0), align 8
ret i32 undef
}
; CHECK-NOT: {{call void @__tsan_write}}
; CHECK: __tsan_init