MIPS: Add code again to allow reclaiming old unexecuted functions.

src/mips/codegen-mips.cc

 // 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 428 matching lines @@
   __ Addu(at, string, at);
   __ lhu(result, MemOperand(at));
   __ jmp(&done);
   __ bind(&ascii);
   // Ascii string.
   __ Addu(at, string, index);
   __ lbu(result, MemOperand(at));
   __ bind(&done);
 }
 
-#undef __
+// nop(CODE_AGE_MARKER_NOP)
+static const uint32_t kCodeAgePatchFirstInstruction = 0x00010180;
+
+static byte* GetNoCodeAgeSequence(uint32_t* length) {
+  // The sequence of instructions that is patched out for aging code is the
+  // following boilerplate stack-building prologue that is found in FUNCTIONS
+  static bool initialized = false;
+  static uint32_t sequence[kNoCodeAgeSequenceLength];
+  byte* byte_sequence = reinterpret_cast<byte*>(sequence);
+  *length = kNoCodeAgeSequenceLength * Assembler::kInstrSize;
+  if (!initialized) {
+    CodePatcher patcher(byte_sequence, kNoCodeAgeSequenceLength);
+    patcher.masm()->Push(ra, fp, cp, a1);
+    patcher.masm()->LoadRoot(at, Heap::kUndefinedValueRootIndex);
+    patcher.masm()->Addu(fp, sp, Operand(2 * kPointerSize));
+    initialized = true;
+  }
+  return byte_sequence;
+}
 
 
 byte* Code::FindPlatformCodeAgeSequence() {
-  UNIMPLEMENTED();
-  return NULL;
+  byte* start = instruction_start();
+  uint32_t young_length;
+  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  if (!memcmp(start, young_sequence, young_length) ||
+      Memory::uint32_at(start) == kCodeAgePatchFirstInstruction) {
+    return start;
+  } else {
+    byte* start_after_strict = NULL;
+    if (kind() == FUNCTION) {
+      start_after_strict = start + kSizeOfFullCodegenStrictModePrologue;
+    } else {
+      ASSERT(kind() == OPTIMIZED_FUNCTION);
+      start_after_strict = start + kSizeOfOptimizedStrictModePrologue;
+    }
+    ASSERT(!memcmp(start_after_strict, young_sequence, young_length) ||
+           Memory::uint32_at(start_after_strict) ==
+           kCodeAgePatchFirstInstruction);
+    return start_after_strict;
+  }
 }
 
 
 bool Code::IsYoungSequence(byte* sequence) {
-  UNIMPLEMENTED();
-  return false;
+  uint32_t young_length;
+  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  bool result = !memcmp(sequence, young_sequence, young_length);
+  ASSERT(result ||
+         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction);
+  return result;
 }
 
 
 void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
                                MarkingParity* parity) {
+  if (IsYoungSequence(sequence)) {
+    *age = kNoAge;
+    *parity = NO_MARKING_PARITY;
+  } else {
+    Address target_address = Memory::Address_at(
+        sequence + Assembler::kInstrSize * (kNoCodeAgeSequenceLength - 1));
+    Code* stub = GetCodeFromTargetAddress(target_address);
+    GetCodeAgeAndParity(stub, age, parity);
+  }
 }
 
 
 void Code::PatchPlatformCodeAge(byte* sequence,
                                 Code::Age age,
                                 MarkingParity parity) {
-  UNIMPLEMENTED();
+  uint32_t young_length;
+  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  if (age == kNoAge) {
+    memcpy(sequence, young_sequence, young_length);
+    CPU::FlushICache(sequence, young_length);
+  } else {
+    Code* stub = GetCodeAgeStub(age, parity);
+    CodePatcher patcher(sequence, young_length / Assembler::kInstrSize);
+    // Mark this code sequence for FindPlatformCodeAgeSequence()
+    patcher.masm()->nop(Assembler::CODE_AGE_MARKER_NOP);
+    // Save the function's original return address
+    // (it will be clobbered by Call(t9))
+    patcher.masm()->mov(at, ra);
+    // Load the stub address to t9 and call it
+    patcher.masm()->li(t9,
+        Operand(reinterpret_cast<uint32_t>(stub->instruction_start())));
+    patcher.masm()->Call(t9);
+    // Record the stub address in the empty space for GetCodeAgeAndParity()
+    patcher.masm()->dd(reinterpret_cast<uint32_t>(stub->instruction_start()));
+  }
 }
 
+
+#undef __
+
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS