Age code to allow reclaiming old unexecuted functions

src/x64/assembler-x64-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 24 matching lines @@
 #include "v8memory.h"
 
 namespace v8 {
 namespace internal {
 
 
 // -----------------------------------------------------------------------------
 // Implementation of Assembler
 
 
+static const byte kCallOpcode = 0xE8;
+
+
 void Assembler::emitl(uint32_t x) {
   Memory::uint32_at(pc_) = x;
   pc_ += sizeof(uint32_t);
 }
 
 
 void Assembler::emitq(uint64_t x, RelocInfo::Mode rmode) {
   Memory::uint64_at(pc_) = x;
   if (rmode != RelocInfo::NONE) {
     RecordRelocInfo(rmode, x);
@@ skipping 155 matching lines @@
 
 // The modes possibly affected by apply must be in kApplyMask.
 void RelocInfo::apply(intptr_t delta) {
   if (IsInternalReference(rmode_)) {
     // absolute code pointer inside code object moves with the code object.
     Memory::Address_at(pc_) += static_cast<int32_t>(delta);
     CPU::FlushICache(pc_, sizeof(Address));
   } else if (IsCodeTarget(rmode_)) {
     Memory::int32_at(pc_) -= static_cast<int32_t>(delta);
     CPU::FlushICache(pc_, sizeof(int32_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));
+    }
   }
 }
 
 
 Address RelocInfo::target_address() {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == RUNTIME_ENTRY);
   if (IsCodeTarget(rmode_)) {
     return Assembler::target_address_at(pc_);
   } else {
     return Memory::Address_at(pc_);
@@ skipping 118 matching lines @@
   return false;
 #endif
 }
 
 
 bool RelocInfo::IsPatchedDebugBreakSlotSequence() {
   return !Assembler::IsNop(pc());
 }
 
 
+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()));
   return Memory::Address_at(
       pc_ + Assembler::kRealPatchReturnSequenceAddressOffset);
 }
 
 
 void RelocInfo::set_call_address(Address target) {
   ASSERT((IsJSReturn(rmode()) && IsPatchedReturnSequence()) ||
@@ skipping 33 matching lines @@
   if (mode == RelocInfo::EMBEDDED_OBJECT) {
     visitor->VisitEmbeddedPointer(this);
     CPU::FlushICache(pc_, sizeof(Address));
   } else if (RelocInfo::IsCodeTarget(mode)) {
     visitor->VisitCodeTarget(this);
   } else if (mode == RelocInfo::GLOBAL_PROPERTY_CELL) {
     visitor->VisitGlobalPropertyCell(this);
   } else if (mode == RelocInfo::EXTERNAL_REFERENCE) {
     visitor->VisitExternalReference(this);
     CPU::FlushICache(pc_, sizeof(Address));
+  } 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()) ||
              (RelocInfo::IsDebugBreakSlot(mode) &&
               IsPatchedDebugBreakSlotSequence())) &&
              Isolate::Current()->debug()->has_break_points()) {
     visitor->VisitDebugTarget(this);
 #endif
   } else if (mode == RelocInfo::RUNTIME_ENTRY) {
     visitor->VisitRuntimeEntry(this);
   }
 }
 
 
 template<typename StaticVisitor>
 void RelocInfo::Visit(Heap* heap) {
   RelocInfo::Mode mode = rmode();
   if (mode == RelocInfo::EMBEDDED_OBJECT) {
     StaticVisitor::VisitEmbeddedPointer(heap, this);
     CPU::FlushICache(pc_, sizeof(Address));
   } else if (RelocInfo::IsCodeTarget(mode)) {
     StaticVisitor::VisitCodeTarget(heap, this);
   } else if (mode == RelocInfo::GLOBAL_PROPERTY_CELL) {
     StaticVisitor::VisitGlobalPropertyCell(heap, this);
   } 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) &&
               IsPatchedReturnSequence()) ||
              (RelocInfo::IsDebugBreakSlot(mode) &&
               IsPatchedDebugBreakSlotSequence()))) {
     StaticVisitor::VisitDebugTarget(heap, this);
 #endif
   } else if (mode == RelocInfo::RUNTIME_ENTRY) {
     StaticVisitor::VisitRuntimeEntry(this);
@@ skipping 35 matching lines @@
   ASSERT(len_ == 1 || len_ == 2);
   int32_t* p = reinterpret_cast<int32_t*>(&buf_[len_]);
   *p = disp;
   len_ += sizeof(int32_t);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_ASSEMBLER_X64_INL_H_