Turn FastNewContextStub into a HydrogenCodeStub.

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index d3b9d5ba70276050e0a81e7454ac41eeb42b28a1..05b6f3c5bfea2f261125ae3c241f00bae9acb22a 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -292,17 +292,18 @@ bool LCodeGen::GeneratePrologue() {
   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();