Enable preaging of code objects when --optimize-for-size.

src/mips/codegen-mips.cc

Index: src/mips/codegen-mips.cc
diff --git a/src/mips/codegen-mips.cc b/src/mips/codegen-mips.cc
index a12faee433a8bb70dbaa09e131c90d836c24c73a..ab5922da0ffd42582678a8ad03035a2b049a22f3 100644
--- a/src/mips/codegen-mips.cc
+++ b/src/mips/codegen-mips.cc
@@ -597,13 +597,32 @@ 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];
+  static uint32_t sequence[kCodeAgeSequenceLength];
   byte* byte_sequence = reinterpret_cast<byte*>(sequence);
-  *length = kNoCodeAgeSequenceLength * Assembler::kInstrSize;
+  *length = kCodeAgeSequenceLength * Assembler::kInstrSize;
   if (!initialized) {
-    CodePatcher patcher(byte_sequence, kNoCodeAgeSequenceLength);
+    CodePatcher patcher(byte_sequence, kCodeAgeSequenceLength);
     patcher.masm()->Push(ra, fp, cp, a1);
-    patcher.masm()->nop(Assembler::CODE_AGE_SEQUENCE_NOP);
+    patcher.masm()->nop(Assembler::CODE_AGE_YOUNG_SEQUENCE_NOP);
+    patcher.masm()->Addu(fp, sp, Operand(2 * kPointerSize));
+    initialized = true;
+  }
+  return byte_sequence;
+}
+
+
+static byte* GetPreAgedCodeAgeSequence(uint32_t* length) {
+  // If code is "pre-aged" then this sequence of instructions is found in the
+  // boilerplate stack-building prologue that is found in FUNCTIONS, and is
+  // patched out for code aging.
+  static bool initialized = false;
+  static uint32_t sequence[kCodeAgeSequenceLength];
+  byte* byte_sequence = reinterpret_cast<byte*>(sequence);
+  *length = kCodeAgeSequenceLength * Assembler::kInstrSize;
+  if (!initialized) {
+    CodePatcher patcher(byte_sequence, kCodeAgeSequenceLength);
+    patcher.masm()->Push(ra, fp, cp, a1);
+    patcher.masm()->nop(Assembler::CODE_AGE_PRE_AGED_SEQUENCE_NOP);
     patcher.masm()->Addu(fp, sp, Operand(2 * kPointerSize));
     initialized = true;
   }
@@ -616,7 +635,19 @@ bool Code::IsYoungSequence(byte* sequence) {
   byte* young_sequence = GetNoCodeAgeSequence(&young_length);
   bool result = !memcmp(sequence, young_sequence, young_length);
   ASSERT(result ||
-         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction);
+         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction ||
+         IsPreAgedSequence(sequence));
+  return result;
+}
+
+
+bool Code::IsPreAgedSequence(byte* sequence) {
+  uint32_t pre_aged_length;
+  byte* pre_aged_sequence = GetPreAgedCodeAgeSequence(&pre_aged_length);
+  bool result = !memcmp(sequence, pre_aged_sequence, pre_aged_length);
+  ASSERT(result ||
+         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction ||
+         IsYoungSequence(sequence));
   return result;
 }
 
@@ -626,9 +657,12 @@ void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
   if (IsYoungSequence(sequence)) {
     *age = kNoAge;
     *parity = NO_MARKING_PARITY;
+  } else if (IsPreAgedSequence(sequence)) {
+    *age = kPreAgedCodeAge;
+    *parity = NO_MARKING_PARITY;
   } else {
     Address target_address = Memory::Address_at(
-        sequence + Assembler::kInstrSize * (kNoCodeAgeSequenceLength - 1));
+        sequence + Assembler::kInstrSize * (kCodeAgeSequenceLength - 1));
     Code* stub = GetCodeFromTargetAddress(target_address);
     GetCodeAgeAndParity(stub, age, parity);
   }