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[gcov] Increment counters with atomicrmw if -fsanitize=thread 

Without this patch, `clang --coverage -fsanitize=thread` may fail spuriously
because non-atomic counter increments can be detected as data races.
This commit is contained in:
Fangrui Song 2020-08-28 16:32:35 -07:00
parent 141c8475b6
commit b5ef137c11
5 changed files with 74 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
clang/lib/CodeGen/BackendUtil.cpp
View File

@ -553,7 +553,9 @@ static void initTargetOptions(DiagnosticsEngine &Diags,
Options.MCOptions.Argv0 = CodeGenOpts.Argv0;
Options.MCOptions.CommandLineArgs = CodeGenOpts.CommandLineArgs;
}
static Optional<GCOVOptions> getGCOVOptions(const CodeGenOptions &CodeGenOpts) {
static Optional<GCOVOptions> getGCOVOptions(const CodeGenOptions &CodeGenOpts,
const LangOptions &LangOpts) {
if (CodeGenOpts.DisableGCov)
return None;
if (!CodeGenOpts.EmitGcovArcs && !CodeGenOpts.EmitGcovNotes)
@ -567,6 +569,7 @@ static Optional<GCOVOptions> getGCOVOptions(const CodeGenOptions &CodeGenOpts) {
Options.NoRedZone = CodeGenOpts.DisableRedZone;
Options.Filter = CodeGenOpts.ProfileFilterFiles;
Options.Exclude = CodeGenOpts.ProfileExcludeFiles;
Options.Atomic = LangOpts.Sanitize.has(SanitizerKind::Thread);
return Options;
}
@ -763,7 +766,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
MPM.add(createUniqueInternalLinkageNamesPass());
}
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts)) {
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts, LangOpts)) {
MPM.add(createGCOVProfilerPass(*Options));
if (CodeGenOpts.getDebugInfo() == codegenoptions::NoDebugInfo)
MPM.add(createStripSymbolsPass(true));
@ -1229,7 +1232,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
MPM.addPass(LowerTypeTestsPass(/*ExportSummary=*/nullptr,
/*ImportSummary=*/nullptr,
/*DropTypeTests=*/true));
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts))
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts, LangOpts))
MPM.addPass(GCOVProfilerPass(*Options));
if (Optional<InstrProfOptions> Options =
getInstrProfOptions(CodeGenOpts, LangOpts))
@ -1349,7 +1352,7 @@ void EmitAssemblyHelper::EmitAssemblyWithNewPassManager(
/*CompileKernel=*/false, Recover, UseAfterScope)));
});
}
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts))
if (Optional<GCOVOptions> Options = getGCOVOptions(CodeGenOpts, LangOpts))
PB.registerPipelineStartEPCallback([Options](ModulePassManager &MPM) {
MPM.addPass(GCOVProfilerPass(*Options));
});

12
clang/test/CodeGen/code-coverage-tsan.c Normal file
View File

@ -0,0 +1,12 @@
/// -fsanitize=thread requires the (potentially concurrent) counter updates to be atomic.
// RUN: %clang_cc1 %s -triple x86_64 -emit-llvm -fsanitize=thread -femit-coverage-notes -femit-coverage-data \
// RUN: -coverage-notes-file /dev/null -coverage-data-file /dev/null -o - | FileCheck %s
// CHECK-LABEL: void @foo()
/// Two counters are incremented by __tsan_atomic64_fetch_add.
// CHECK: call i64 @__tsan_atomic64_fetch_add
// CHECK-NEXT: call i64 @__tsan_atomic64_fetch_add
// CHECK-NEXT: call i32 @__tsan_atomic32_fetch_sub
_Atomic(int) cnt;
void foo() { cnt--; }

3
llvm/include/llvm/Transforms/Instrumentation.h
View File

@ -66,6 +66,9 @@ struct GCOVOptions {
// Add the 'noredzone' attribute to added runtime library calls.
bool NoRedZone;
// Use atomic profile counter increments.
bool Atomic = false;
// Regexes separated by a semi-colon to filter the files to instrument.
std::string Filter;

28
llvm/lib/Transforms/Instrumentation/GCOVProfiling.cpp
View File

@ -63,6 +63,9 @@ static cl::opt<std::string> DefaultGCOVVersion("default-gcov-version",
cl::init("408*"), cl::Hidden,
cl::ValueRequired);
static cl::opt<bool> AtomicCounter("gcov-atomic-counter", cl::Hidden,
cl::desc("Make counter updates atomic"));
// Returns the number of words which will be used to represent this string.
static unsigned wordsOfString(StringRef s) {
// Length + NUL-terminated string + 0~3 padding NULs.
@ -74,6 +77,7 @@ GCOVOptions GCOVOptions::getDefault() {
Options.EmitNotes = true;
Options.EmitData = true;
Options.NoRedZone = false;
Options.Atomic = AtomicCounter;
if (DefaultGCOVVersion.size() != 4) {
llvm::report_fatal_error(std::string("Invalid -default-gcov-version: ") +
@ -883,9 +887,15 @@ bool GCOVProfiler::emitProfileArcs() {
// Skip phis, landingpads.
IRBuilder<> Builder(&*BB.getFirstInsertionPt());
Value *Count = Builder.CreateLoad(Builder.getInt64Ty(), Phi);
Count = Builder.CreateAdd(Count, Builder.getInt64(1));
Builder.CreateStore(Count, Phi);
if (Options.Atomic) {
Builder.CreateAtomicRMW(AtomicRMWInst::Add, Phi,
Builder.getInt64(1),
AtomicOrdering::Monotonic);
} else {
Value *Count = Builder.CreateLoad(Builder.getInt64Ty(), Phi);
Count = Builder.CreateAdd(Count, Builder.getInt64(1));
Builder.CreateStore(Count, Phi);
}
Instruction *TI = BB.getTerminator();
if (isa<ReturnInst>(TI)) {
@ -894,9 +904,15 @@ bool GCOVProfiler::emitProfileArcs() {
const unsigned Edge = It->second;
Value *Counter = Builder.CreateConstInBoundsGEP2_64(
Counters->getValueType(), Counters, 0, Edge);
Value *Count = Builder.CreateLoad(Builder.getInt64Ty(), Counter);
Count = Builder.CreateAdd(Count, Builder.getInt64(1));
Builder.CreateStore(Count, Counter);
if (Options.Atomic) {
Builder.CreateAtomicRMW(AtomicRMWInst::Add, Counter,
Builder.getInt64(1),
AtomicOrdering::Monotonic);
} else {
Value *Count = Builder.CreateLoad(Builder.getInt64Ty(), Counter);
Count = Builder.CreateAdd(Count, Builder.getInt64(1));
Builder.CreateStore(Count, Counter);
}
}
}
}

30
llvm/test/Transforms/GCOVProfiling/atomic-counter.ll Normal file
View File

@ -0,0 +1,30 @@
;; -fsanitize=thread requires the (potentially concurrent) counter updates to be atomic.
; RUN: opt < %s -S -passes=insert-gcov-profiling -gcov-atomic-counter | FileCheck %s
; CHECK-LABEL: void @empty()
; CHECK-NEXT: entry:
; CHECK-NEXT: br label %0, !dbg [[DBG:![0-9]+]]
; CHECK: 0:
; CHECK-NEXT: %1 = phi i64* [ getelementptr inbounds ([2 x i64], [2 x i64]* @__llvm_gcov_ctr, i64 0, i64 0), %entry ], !dbg [[DBG]]
; CHECK-NEXT: %2 = atomicrmw add i64* %1, i64 1 monotonic, !dbg [[DBG]]
;; Counter for the exit.
; CHECK-NEXT: %3 = atomicrmw add i64* getelementptr inbounds ([2 x i64], [2 x i64]* @__llvm_gcov_ctr, i64 0, i64 1), i64 1 monotonic, !dbg [[DBG]]
; CHECK-NEXT: ret void, !dbg [[DBG]]
define dso_local void @empty() !dbg !5 {
entry:
ret void, !dbg !8
}
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!3, !4}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, emissionKind: FullDebug, enums: !2)
!1 = !DIFile(filename: "a.c", directory: "")
!2 = !{}
!3 = !{i32 7, !"Dwarf Version", i32 5}
!4 = !{i32 2, !"Debug Info Version", i32 3}
!5 = distinct !DISubprogram(name: "empty", scope: !1, file: !1, line: 1, type: !6, scopeLine: 1, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
!6 = !DISubroutineType(types: !7)
!7 = !{null}
!8 = !DILocation(line: 2, column: 1, scope: !5)