Index: lib/Transforms/Instrumentation/ThreadSanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -36,6 +36,7 @@
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
+#include "llvm/ProfileData/InstrProf.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
@@ -243,6 +244,24 @@
   return false;
 }
 
+// Do not instrument known races/"benign races" that come from compiler
+// instrumentatin. The user has no way of suppressing them.
+bool shouldInstrumentReadWriteFromAddress(Value *Addr) {
+  // Peel off GEPs and BitCasts.
+  Addr = Addr->stripInBoundsOffsets();
+
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
+    if (GV->hasSection()) {
+      StringRef SectionName = GV->getSection();
+      // Check if the global is in the PGO counters section.
+      if (SectionName.endswith(getInstrProfCountersSectionName(
+            /*AddSegment=*/false)))
+        return false;
+    }
+  }
+  return true;
+}
+
 bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
   // If this is a GEP, just analyze its pointer operand.
   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
@@ -285,10 +304,15 @@
        E = Local.rend(); It != E; ++It) {
     Instruction *I = *It;
     if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
-      WriteTargets.insert(Store->getPointerOperand());
+      Value *Addr = Store->getPointerOperand();
+      if (!shouldInstrumentReadWriteFromAddress(Addr))
+        continue;
+      WriteTargets.insert(Addr);
     } else {
       LoadInst *Load = cast<LoadInst>(I);
       Value *Addr = Load->getPointerOperand();
+      if (!shouldInstrumentReadWriteFromAddress(Addr))
+        continue;
       if (WriteTargets.count(Addr)) {
         // We will write to this temp, so no reason to analyze the read.
         NumOmittedReadsBeforeWrite++;
Index: test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
===================================================================
--- /dev/null
+++ test/Instrumentation/ThreadSanitizer/do-not-instrument-memory-access.ll
@@ -0,0 +1,33 @@
+; This test checks that we are not instrumenting unwanted acesses to globals:
+; - Instruction profiler counter instrumentation has known intended races.
+;
+; RUN: opt < %s -tsan -S | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.9"
+
+@__profc_test_gep = private global [1 x i64] zeroinitializer, section "__DATA,__llvm_prf_cnts", align 8
+@__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
+
+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)
+  ret i32 1
+}
+
+define i32 @test_bitcast() sanitize_thread {
+entry:
+  %0 = load <2 x i64>, <2 x i64>* bitcast ([2 x i64]* @__profc_test_bitcast to <2 x i64>*), align 8
+  %.promoted5 = load i64, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_bitcast_foo, i64 0, i64 0), align 8
+  %1 = add i64 %.promoted5, 10
+  %2 = add <2 x i64> %0, <i64 1, i64 10>
+  store <2 x i64> %2, <2 x i64>* bitcast ([2 x i64]* @__profc_test_bitcast to <2 x i64>*), align 8
+  store i64 %1, i64* getelementptr inbounds ([1 x i64], [1 x i64]* @__profc_test_bitcast_foo, i64 0, i64 0), align 8
+  ret i32 undef
+}
+
+; CHECK-NOT: {{call void @__tsan_write}}
+; CHECK: __tsan_init