[tsan] Do not instrument accesses to the gcov counters array

There is a known intended race here. This is a follow-up to r264805,
which disabled tsan instrumentation for updates to instrprof counters.
For more background on this please see the discussion in D18164.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273202 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index eed77b701e339551a47caf2f015f39bf6c267c3d..22a26d49374608a2d5b67b6a8b57b569a0a7d677 100644 (file)
--- a/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -271,6 +271,10 @@ static bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
             /*AddSegment=*/false)))
         return false;
     }
+
+    // Check if the global is in the GCOV counters array.
+    if (GV->getName() == "__llvm_gcov_ctr")
+      return false;
   }
   return true;
 }

diff --git a/test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll b/test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
index 5559441d0adc54a05317ec9fa9b0dd5f534da42b..e734a382a9c1abfdd47d69d456e714948052176c 100644 (file)
--- a/test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
+++ b/test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
@@ -1,5 +1,6 @@
 ; This test checks that we are not instrumenting unwanted acesses to globals:
 ; - Instruction profiler counter instrumentation has known intended races.
+; - The gcov counters array has a known intended race.
 ;
 ; RUN: opt < %s -tsan -S | FileCheck %s
 
@@ -10,11 +11,18 @@ target triple = "x86_64-apple-macosx10.9"
 @__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
 
+@__llvm_gcov_ctr = internal global [1 x i64] zeroinitializer
+
 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)
+
+  %gcovcount = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__llvm_gcov_ctr, i64 0, i64 0)
+  %1 = add i64 %gcovcount, 1
+  store i64 %1, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__llvm_gcov_ctr, i64 0, i64 0)
+
   ret i32 1
 }