MIPS: Stay in fast enum case if the empty_slow_element_dictionary is used.

src/mips/macro-assembler-mips.cc

Index: src/mips/macro-assembler-mips.cc
diff --git a/src/mips/macro-assembler-mips.cc b/src/mips/macro-assembler-mips.cc
index 8d85aed0ba226b708948bf61e13e9495e7d30594..b6476499f0560c3f27d8dedef76004dfbda9a520 100644
--- a/src/mips/macro-assembler-mips.cc
+++ b/src/mips/macro-assembler-mips.cc
@@ -5556,9 +5556,15 @@ void MacroAssembler::CheckEnumCache(Register null_value, Label* call_runtime) {
 
   // Check that there are no elements. Register r2 contains the current JS

[Paul Lind, 2014/01/21 17:46:12]

nit: comment has wrong register name (from previous CL) - I'll fix when
committing.

   // object we've reached through the prototype chain.
+  Label no_elements;
   lw(a2, FieldMemOperand(a2, JSObject::kElementsOffset));
-  Branch(call_runtime, ne, a2, Operand(empty_fixed_array_value));
+  Branch(&no_elements, eq, a2, Operand(empty_fixed_array_value));
 
+  // Second chance, the object may be using the empty slow element dictionary.
+  LoadRoot(at, Heap::kEmptySlowElementDictionaryRootIndex);
+  Branch(call_runtime, ne, a2, Operand(at));
+
+  bind(&no_elements);
   lw(a2, FieldMemOperand(a1, Map::kPrototypeOffset));
   Branch(&next, ne, a2, Operand(null_value));
 }