[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

llvm-svn: 339955

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/test/CodeGen/tsan-instrprof-atomic.c b/clang/test/CodeGen/tsan-instrprof-atomic.c
new file mode 100644
index 00000000000..b7f99e73d3c
--- /dev/null
+++ b/clang/test/CodeGen/tsan-instrprof-atomic.c
@@ -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() {}