[llvm] r339955 - [InstrProf] Use atomic profile counter updates for TSan
Vedant Kumar via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 16 15:24:48 PDT 2018
Author: vedantk
Date: Thu Aug 16 15:24:47 2018
New Revision: 339955
URL: http://llvm.org/viewvc/llvm-project?rev=339955&view=rev
Log:
[InstrProf] Use atomic profile counter updates for TSan
Thread sanitizer instrumentation fails to skip all loads and stores to
profile counters. This can happen if profile counter updates are merged:
%.sink = phi i64* ...
%pgocount5 = load i64, i64* %.sink
%27 = add i64 %pgocount5, 1
%28 = bitcast i64* %.sink to i8*
call void @__tsan_write8(i8* %28)
store i64 %27, i64* %.sink
To suppress TSan diagnostics about racy counter updates, make the
counter updates atomic when TSan is enabled. If there's general interest
in this mode it can be surfaced as a clang/swift driver option.
Testing: check-{llvm,clang,profile}
rdar://40477803
Differential Revision: https://reviews.llvm.org/D50867
Added:
llvm/trunk/test/Instrumentation/InstrProfiling/atomic-updates.ll
Modified:
llvm/trunk/include/llvm/Transforms/Instrumentation.h
llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
Modified: llvm/trunk/include/llvm/Transforms/Instrumentation.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Instrumentation.h?rev=339955&r1=339954&r2=339955&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Instrumentation.h (original)
+++ llvm/trunk/include/llvm/Transforms/Instrumentation.h Thu Aug 16 15:24:47 2018
@@ -111,6 +111,9 @@ struct InstrProfOptions {
// Do counter register promotion
bool DoCounterPromotion = false;
+ // Use atomic profile counter increments.
+ bool Atomic = false;
+
// Name of the profile file to use as output
std::string InstrProfileOutput;
Modified: llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp?rev=339955&r1=339954&r2=339955&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp (original)
+++ llvm/trunk/lib/Transforms/Instrumentation/InstrProfiling.cpp Thu Aug 16 15:24:47 2018
@@ -96,6 +96,11 @@ cl::opt<double> NumCountersPerValueSite(
// is usually smaller than 2.
cl::init(1.0));
+cl::opt<bool> AtomicCounterUpdateAll(
+ "instrprof-atomic-counter-update-all", cl::ZeroOrMore,
+ cl::desc("Make all profile counter updates atomic (for testing only)"),
+ cl::init(false));
+
cl::opt<bool> AtomicCounterUpdatePromoted(
"atomic-counter-update-promoted", cl::ZeroOrMore,
cl::desc("Do counter update using atomic fetch add "
@@ -597,12 +602,17 @@ void InstrProfiling::lowerIncrement(Inst
IRBuilder<> Builder(Inc);
uint64_t Index = Inc->getIndex()->getZExtValue();
Value *Addr = Builder.CreateConstInBoundsGEP2_64(Counters, 0, Index);
- Value *Load = Builder.CreateLoad(Addr, "pgocount");
- auto *Count = Builder.CreateAdd(Load, Inc->getStep());
- auto *Store = Builder.CreateStore(Count, Addr);
- Inc->replaceAllUsesWith(Store);
- if (isCounterPromotionEnabled())
- PromotionCandidates.emplace_back(cast<Instruction>(Load), Store);
+
+ if (Options.Atomic || AtomicCounterUpdateAll) {
+ Builder.CreateAtomicRMW(AtomicRMWInst::Add, Addr, Inc->getStep(),
+ AtomicOrdering::Monotonic);
+ } else {
+ Value *Load = Builder.CreateLoad(Addr, "pgocount");
+ auto *Count = Builder.CreateAdd(Load, Inc->getStep());
+ auto *Store = Builder.CreateStore(Count, Addr);
+ if (isCounterPromotionEnabled())
+ PromotionCandidates.emplace_back(cast<Instruction>(Load), Store);
+ }
Inc->eraseFromParent();
}
Added: llvm/trunk/test/Instrumentation/InstrProfiling/atomic-updates.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/InstrProfiling/atomic-updates.ll?rev=339955&view=auto
==============================================================================
--- llvm/trunk/test/Instrumentation/InstrProfiling/atomic-updates.ll (added)
+++ llvm/trunk/test/Instrumentation/InstrProfiling/atomic-updates.ll Thu Aug 16 15:24:47 2018
@@ -0,0 +1,14 @@
+; RUN: opt < %s -S -instrprof -instrprof-atomic-counter-update-all | FileCheck %s
+
+target triple = "x86_64-apple-macosx10.10.0"
+
+ at __profn_foo = hidden constant [3 x i8] c"foo"
+
+; CHECK-LABEL: define void @foo
+; CHECK-NEXT: atomicrmw add i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_foo, i64 0, i64 0), i64 1 monotonic
+define void @foo() {
+ call void @llvm.instrprof.increment(i8* getelementptr inbounds ([3 x i8], [3 x i8]* @__profn_foo, i32 0, i32 0), i64 0, i32 1, i32 0)
+ ret void
+}
+
+declare void @llvm.instrprof.increment(i8*, i64, i32, i32)
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