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..f52ae89eec24ba071499738424c147336bd62a77 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 +4155,48 @@ void LCodeGen::DoCheckFunction(LCheckFunction* instr) {
 }
 
 
+void LCodeGen::DoCheckMapCommon(Register reg,
+                                Register scratch,
+                                Handle<Map> map,
+                                MapCheckMode mode,
+                                LEnvironment* env) {
+  Label success;
+  __ ldr(scratch, FieldMemOperand(reg, HeapObject::kMapOffset));
+  __ mov(ip, Operand(map));
+  __ cmp(scratch, ip);
+  if (mode == ALLOW_ELEMENT_TRANSITION_MAPS) {
+    bool ignore;
+    Map* transitioned_double_map =
+        map->LookupElementsTransitionMap(FAST_DOUBLE_ELEMENTS, &ignore);
+    ASSERT(transitioned_double_map == NULL ||
+           map->elements_kind() == FAST_SMI_ONLY_ELEMENTS);
+    Map* transitioned_fast_element_map =
+        map->LookupElementsTransitionMap(FAST_ELEMENTS, &ignore);
+    ASSERT(transitioned_fast_element_map == NULL ||
+           map->elements_kind() != FAST_ELEMENTS);
+    if (transitioned_fast_element_map != NULL) {
+      __ b(eq, &success);
+      __ cmp(scratch, Operand(Handle<Map>(transitioned_fast_element_map)));
+    }
+
+    if (transitioned_double_map != NULL) {
+      __ b(eq, &success);
+      __ cmp(scratch, Operand(Handle<Map>(transitioned_double_map)));
+    }
+  }
+  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 = Handle<Map>(instr->hydrogen()->map());
+  DoCheckMapCommon(reg, scratch, map, instr->hydrogen()->mode(),
+                   instr->environment());
 }
 
 
@@ -4231,9 +4265,9 @@ 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 +4275,9 @@ 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());
 }