Turn FastNewContextStub into a HydrogenCodeStub.

src/ia32/lithium-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 274 matching lines @@
     if (info()->saves_caller_doubles() && CpuFeatures::IsSupported(SSE2)) {
       SaveCallerDoubles();
     }
   }
 
   // Possibly allocate a local context.
   int heap_slots = info_->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
   if (heap_slots > 0) {
     Comment(";;; Allocate local context");
     // Argument to NewContext is the function, which is still in edi.
-    __ push(edi);
     if (heap_slots <= FastNewContextStub::kMaximumSlots) {
       FastNewContextStub stub(heap_slots);
       __ CallStub(&stub);
     } else {
+      __ push(edi);
       __ CallRuntime(Runtime::kNewFunctionContext, 1);
     }
     RecordSafepoint(Safepoint::kNoLazyDeopt);
-    // Context is returned in both eax and esi.  It replaces the context
-    // passed to us.  It's saved in the stack and kept live in esi.
-    __ mov(Operand(ebp, StandardFrameConstants::kContextOffset), esi);
+    // Context is returned in eax.  It replaces the context passed to us.
+    // It's saved in the stack and kept live in esi.
+    __ mov(esi, eax);
+    __ mov(Operand(ebp, StandardFrameConstants::kContextOffset), eax);
 
     // Copy parameters into context if necessary.
     int num_parameters = scope()->num_parameters();
     for (int i = 0; i < num_parameters; i++) {
       Variable* var = scope()->parameter(i);
       if (var->IsContextSlot()) {
         int parameter_offset = StandardFrameConstants::kCallerSPOffset +
             (num_parameters - 1 - i) * kPointerSize;
         // Load parameter from stack.
         __ mov(eax, Operand(ebp, parameter_offset));
@@ skipping 6039 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32