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

src/ia32/full-codegen-ia32.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 142 matching lines @@
   }
 
   // Open a frame scope to indicate that there is a frame on the stack.  The
   // MANUAL indicates that the scope shouldn't actually generate code to set up
   // the frame (that is done below).
   FrameScope frame_scope(masm_, StackFrame::MANUAL);
 
   info->set_prologue_offset(masm_->pc_offset());
   __ push(ebp);  // Caller's frame pointer.
   __ mov(ebp, esp);
-  __ push(esi);  // Callee's context.
+  if (isolate()->is_memory_constrained()) {
+    // This sequence marks pre-aged code.
+    __ push(esi);  // Callee's context.
+    __ nop();

[Michael Starzinger, 2013/09/17 22:56:44]

IIUC this is a glorified way to store exactly one bit of information, namely
whether a code object is freshly generated and has never been aged before.
Wouldn't it be easier to store that bit of information in the code object
header? This could spare us from adding a NOP to every single method prologue.
Also it would keep platform specific changes to a minimum.

+  } else {
+    // This sequence marks non-aged code.
+    __ nop();
+    __ push(esi);  // Callee's context
+  }
   __ push(edi);  // Callee's JS Function.
   info->AddNoFrameRange(0, masm_->pc_offset());
 
   { Comment cmnt(masm_, "[ Allocate locals");
     int locals_count = info->scope()->num_stack_slots();
     // Generators allocate locals, if any, in context slots.
     ASSERT(!info->function()->is_generator() || locals_count == 0);
     if (locals_count == 1) {
       __ push(Immediate(isolate()->factory()->undefined_value()));
     } else if (locals_count > 1) {
@@ skipping 4719 matching lines @@
   *stack_depth = 0;
   *context_length = 0;
   return previous_;
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32