[tsan] Do not instrument reads/writes to instruction profile counters.

We have known races on profile counters, which can be reproduced by enabling
-fsanitize=thread and -fprofile-instr-generate simultaneously on a
multi-threaded program. This patch avoids reporting those races by not
instrumenting the reads and writes coming from the instruction profiler.

llvm-svn: 264805

1 files changed, 25 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index e73a4b2..38d87cb 100644
--- a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/llvm/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 @@ static bool isVtableAccess(Instruction *I) {
   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 @@ void ThreadSanitizer::chooseInstructionsToInstrument(
        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++;