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

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 7fabb9ff2e56a8521e500d83f144c7607cdc450b..984d0a0e65cbf49e48d45bc4ec3b9d1870a1431d 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -139,14 +139,29 @@ bool LCodeGen::GeneratePrologue() {
       // Adjust FP to point to saved FP.
       __ Addu(fp, sp, Operand(2 * kPointerSize));
     } else {
+      PredictableCodeSizeScope predictible_code_size_scope(
+        masm_, kNoCodeAgeSequenceLength * Assembler::kInstrSize);
       // The following three instructions must remain together and unmodified
       // for code aging to work properly.
-      __ Push(ra, fp, cp, a1);
-      // Add unused nop to ensure prologue sequence is identical for
-      // full-codegen and lithium-codegen.
-      __ nop(Assembler::CODE_AGE_SEQUENCE_NOP);
-      // Adj. FP to point to saved FP.
-      __ Addu(fp, sp, Operand(2 * kPointerSize));
+      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));
+      }
     }
     frame_is_built_ = true;
     info_->AddNoFrameRange(0, masm_->pc_offset());