Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/arm64/codegen-arm64.cc

Index: src/arm64/codegen-arm64.cc
diff --git a/src/arm64/codegen-arm64.cc b/src/arm64/codegen-arm64.cc
index 7276024e15939bed10e2e9926568bc00402e58ec..ff06eda86ab593ca3df7f5df56b74b9fd9b72403 100644
--- a/src/arm64/codegen-arm64.cc
+++ b/src/arm64/codegen-arm64.cc
@@ -350,14 +350,41 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
 }
 
 
-bool Code::IsYoungSequence(byte* sequence) {
-  return MacroAssembler::IsYoungSequence(sequence);
+CodeAgingHelper::CodeAgingHelper() {
+  ASSERT(young_sequence_.length() == kNoCodeAgeSequenceLength);
+  // The sequence of instructions that is patched out for aging code is the
+  // following boilerplate stack-building prologue that is found both in
+  // FUNCTION and OPTIMIZED_FUNCTION code:
+  PatchingAssembler patcher(young_sequence_.start(),
+                            young_sequence_.length() / kInstructionSize);
+  // The young sequence is the frame setup code for FUNCTION code types. It is
+  // generated by FullCodeGenerator::Generate.
+  MacroAssembler::EmitFrameSetupForCodeAgePatching(&patcher);
+
+#ifdef DEBUG
+  const int length = kCodeAgeStubEntryOffset / kInstructionSize;
+  ASSERT(old_sequence_.length() >= kCodeAgeStubEntryOffset);
+  PatchingAssembler patcher_old(old_sequence_.start(), length);
+  MacroAssembler::EmitCodeAgeSequence(&patcher_old, NULL);
+#endif
+}
+
+
+#ifdef DEBUG
+bool CodeAgingHelper::IsOld(byte* candidate) const {
+  return memcmp(candidate, old_sequence_.start(), kCodeAgeStubEntryOffset) == 0;
+}
+#endif
+
+
+bool Code::IsYoungSequence(Isolate* isolate, byte* sequence) {
+  return MacroAssembler::IsYoungSequence(isolate, sequence);
 }
 
 
-void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
+void Code::GetCodeAgeAndParity(Isolate* isolate, byte* sequence, Age* age,
                                MarkingParity* parity) {
-  if (IsYoungSequence(sequence)) {
+  if (IsYoungSequence(isolate, sequence)) {
     *age = kNoAgeCodeAge;
     *parity = NO_MARKING_PARITY;
   } else {
@@ -372,7 +399,8 @@ void Code::PatchPlatformCodeAge(Isolate* isolate,
                                 byte* sequence,
                                 Code::Age age,
                                 MarkingParity parity) {
-  PatchingAssembler patcher(sequence, kCodeAgeSequenceSize / kInstructionSize);
+  PatchingAssembler patcher(sequence,
+                            kNoCodeAgeSequenceLength / kInstructionSize);
   if (age == kNoAgeCodeAge) {
     MacroAssembler::EmitFrameSetupForCodeAgePatching(&patcher);
   } else {