Make sure transitioned arrays efficiently call builtin Array functions

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index e1e35d251ec58c3172e6b696de0a6e0f3d352799..e79caf1854b978711411a9fa434b6bff464c12ed 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -1,4 +1,4 @@
-// Copyright 2011 the V8 project authors. All rights reserved.
+// 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:
@@ -4155,14 +4155,26 @@ void LCodeGen::DoCheckFunction(LCheckFunction* instr) {
 }
 
 
+void LCodeGen::DoCheckMapCommon(Register reg,
+                                Register scratch,
+                                Handle<Map> map,
+                                CompareMapMode mode,
+                                LEnvironment* env) {
+  Label success;
+  __ CompareMap(reg, scratch, map, &success, mode);
+  DeoptimizeIf(ne, env);
+  __ bind(&success);
+}
+
+
 void LCodeGen::DoCheckMap(LCheckMap* instr) {
   Register scratch = scratch0();
   LOperand* input = instr->InputAt(0);
   ASSERT(input->IsRegister());
   Register reg = ToRegister(input);
-  __ ldr(scratch, FieldMemOperand(reg, HeapObject::kMapOffset));
-  __ cmp(scratch, Operand(instr->hydrogen()->map()));
-  DeoptimizeIf(ne, instr->environment());
+  Handle<Map> map = instr->hydrogen()->map();
+  DoCheckMapCommon(reg, scratch, map, instr->hydrogen()->mode(),
+                   instr->environment());
 }
 
 
@@ -4231,9 +4243,9 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
 
   // Check prototype maps up to the holder.
   while (!current_prototype.is_identical_to(holder)) {
-    __ ldr(temp2, FieldMemOperand(temp1, HeapObject::kMapOffset));
-    __ cmp(temp2, Operand(Handle<Map>(current_prototype->map())));
-    DeoptimizeIf(ne, instr->environment());
+    DoCheckMapCommon(temp1, temp2,
+                     Handle<Map>(current_prototype->map()),
+                     ALLOW_ELEMENT_TRANSITION_MAPS, instr->environment());
     current_prototype =
         Handle<JSObject>(JSObject::cast(current_prototype->GetPrototype()));
     // Load next prototype object.
@@ -4241,8 +4253,9 @@ void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
   }
 
   // Check the holder map.
-  __ ldr(temp2, FieldMemOperand(temp1, HeapObject::kMapOffset));
-  __ cmp(temp2, Operand(Handle<Map>(current_prototype->map())));
+  DoCheckMapCommon(temp1, temp2,
+                   Handle<Map>(current_prototype->map()),
+                   ALLOW_ELEMENT_TRANSITION_MAPS, instr->environment());
   DeoptimizeIf(ne, instr->environment());
 }