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

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index b9e282f760d3c06ecffc8ea47aed555e8761b918..f85c0f3dd33d17e46f69608ff7312b0ddaf3164b 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -171,12 +171,31 @@ void FullCodeGenerator::Generate() {
   FrameScope frame_scope(masm_, StackFrame::MANUAL);
 
   info->set_prologue_offset(masm_->pc_offset());
-  // The following three instructions must remain together and unmodified for
-  // code aging to work properly.
-  __ Push(ra, fp, cp, a1);
-  __ nop(Assembler::CODE_AGE_SEQUENCE_NOP);
-  // Adjust fp to point to caller's fp.
-  __ Addu(fp, sp, Operand(2 * kPointerSize));
+  {
+    PredictableCodeSizeScope predictible_code_size_scope(
+        masm_, kNoCodeAgeSequenceLength * Assembler::kInstrSize);
+    // The following three instructions must remain together and unmodified
+    // for code aging to work properly.
+    if (FLAG_optimize_for_size && FLAG_age_code) {
+      // Pre-age the code.
+      Code* stub = Code::GetPreAgedCodeAgeStub(isolate());
+      __ nop(Assembler::CODE_AGE_MARKER_NOP);
+      // Save the function's original return address
+      // (it will be clobbered by Call(t9))
+      __ mov(at, ra);
+      // Load the stub address to t9 and call it
+      __ li(t9,
+            Operand(reinterpret_cast<uint32_t>(stub->instruction_start())));
+      __ Call(t9);
+      // Record the stub address in the empty space for GetCodeAgeAndParity()
+      __ dd(reinterpret_cast<uint32_t>(stub->instruction_start()));
+    } else {
+      __ Push(ra, fp, cp, a1);
+      __ nop(Assembler::CODE_AGE_SEQUENCE_NOP);
+      // Adjust fp to point to caller's fp.
+      __ Addu(fp, sp, Operand(2 * kPointerSize));
+    }
+  }
   info->AddNoFrameRange(0, masm_->pc_offset());
 
   { Comment cmnt(masm_, "[ Allocate locals");