r339955 - [InstrProf] Use atomic profile counter updates for TSan

[Vedant Kumar via cfe-commits]

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:
    cfe/trunk/test/CodeGen/tsan-instrprof-atomic.c
Modified:
    cfe/trunk/lib/CodeGen/BackendUtil.cpp

Modified: cfe/trunk/lib/CodeGen/BackendUtil.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/BackendUtil.cpp?rev=339955&r1=339954&r2=339955&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/BackendUtil.cpp (original)
+++ cfe/trunk/lib/CodeGen/BackendUtil.cpp Thu Aug 16 15:24:47 2018
@@ -653,6 +653,11 @@ void EmitAssemblyHelper::CreatePasses(le
     InstrProfOptions Options;
     Options.NoRedZone = CodeGenOpts.DisableRedZone;
     Options.InstrProfileOutput = CodeGenOpts.InstrProfileOutput;
+
+    // TODO: Surface the option to emit atomic profile counter increments at
+    // the driver level.
+    Options.Atomic = LangOpts.Sanitize.has(SanitizerKind::Thread);
+
     MPM.add(createInstrProfilingLegacyPass(Options));
   }
   if (CodeGenOpts.hasProfileIRInstr()) {

Added: cfe/trunk/test/CodeGen/tsan-instrprof-atomic.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/tsan-instrprof-atomic.c?rev=339955&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/tsan-instrprof-atomic.c (added)
+++ cfe/trunk/test/CodeGen/tsan-instrprof-atomic.c Thu Aug 16 15:24:47 2018
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 %s -emit-llvm -fprofile-instrument=clang -fsanitize=thread -o - | FileCheck %s
+
+// CHECK: define void @foo
+// CHECK-NOT: load {{.*}}foo
+// CHECK: ret void
+void foo() {}