Age code to allow reclaiming old unexecuted functions

src/ia32/assembler-ia32-inl.h

Index: src/ia32/assembler-ia32-inl.h
diff --git a/src/ia32/assembler-ia32-inl.h b/src/ia32/assembler-ia32-inl.h
index 7fdf50c7a1e026cab03685ffbb7acccbea348c42..114f8784214401960492f92320ab2a76e013dc1e 100644
--- a/src/ia32/assembler-ia32-inl.h
+++ b/src/ia32/assembler-ia32-inl.h
@@ -46,12 +46,21 @@ namespace v8 {
 namespace internal {
 
 
+static const byte kCallOpcode = 0xE8;
+
+
 // The modes possibly affected by apply must be in kApplyMask.
 void RelocInfo::apply(intptr_t delta) {
   if (rmode_ == RUNTIME_ENTRY || IsCodeTarget(rmode_)) {
     int32_t* p = reinterpret_cast<int32_t*>(pc_);
     *p -= delta;  // Relocate entry.
     CPU::FlushICache(p, sizeof(uint32_t));
+  } else if (rmode_ == CODE_AGE_SEQUENCE) {
+    if (*pc_ == kCallOpcode) {
+      int32_t* p = reinterpret_cast<int32_t*>(pc_ + 1);
+      *p -= delta;  // Relocate entry.
+      CPU::FlushICache(p, sizeof(uint32_t));
+    }
   } else if (rmode_ == JS_RETURN && IsPatchedReturnSequence()) {
     // Special handling of js_return when a break point is set (call
     // instruction has been inserted).
@@ -169,6 +178,21 @@ void RelocInfo::set_target_cell(JSGlobalPropertyCell* cell,
 }
 
 
+Code* RelocInfo::code_age_stub() {
+  ASSERT(rmode_ == RelocInfo::CODE_AGE_SEQUENCE);
+  ASSERT(*pc_ == kCallOpcode);
+  return Code::GetCodeFromTargetAddress(
+      Assembler::target_address_at(pc_ + 1));
+}
+
+
+void RelocInfo::set_code_age_stub(Code* stub) {
+  ASSERT(*pc_ == kCallOpcode);
+  ASSERT(rmode_ == RelocInfo::CODE_AGE_SEQUENCE);
+  Assembler::set_target_address_at(pc_ + 1, stub->instruction_start());
+}
+
+
 Address RelocInfo::call_address() {
   ASSERT((IsJSReturn(rmode()) && IsPatchedReturnSequence()) ||
          (IsDebugBreakSlot(rmode()) && IsPatchedDebugBreakSlotSequence()));
@@ -206,7 +230,7 @@ Object** RelocInfo::call_object_address() {
 
 
 bool RelocInfo::IsPatchedReturnSequence() {
-  return *pc_ == 0xE8;
+  return *pc_ == kCallOpcode;
 }
 
 
@@ -227,7 +251,9 @@ void RelocInfo::Visit(ObjectVisitor* visitor) {
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     visitor->VisitExternalReference(this);
     CPU::FlushICache(pc_, sizeof(Address));
-#ifdef ENABLE_DEBUGGER_SUPPORT
+  } else if (RelocInfo::IsCodeAgeSequence(mode)) {
+    visitor->VisitCodeAgeSequence(this);
+  #ifdef ENABLE_DEBUGGER_SUPPORT
   // TODO(isolates): Get a cached isolate below.
   } else if (((RelocInfo::IsJSReturn(mode) &&
               IsPatchedReturnSequence()) ||
@@ -255,6 +281,8 @@ void RelocInfo::Visit(Heap* heap) {
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     StaticVisitor::VisitExternalReference(this);
     CPU::FlushICache(pc_, sizeof(Address));
+  } else if (RelocInfo::IsCodeAgeSequence(mode)) {
+    StaticVisitor::VisitCodeAgeSequence(heap, this);
 #ifdef ENABLE_DEBUGGER_SUPPORT
   } else if (heap->isolate()->debug()->has_break_points() &&
              ((RelocInfo::IsJSReturn(mode) &&