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

src/mips/macro-assembler-mips.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
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@@ skipping 5536 matching lines @@
 
   bind(&next);
   lw(a1, FieldMemOperand(a2, HeapObject::kMapOffset));
 
   // For all objects but the receiver, check that the cache is empty.
   EnumLength(a3, a1);
   Branch(call_runtime, ne, a3, Operand(Smi::FromInt(0)));
 
   bind(&start);
 
   // 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));
 }
 
 
 void MacroAssembler::ClampUint8(Register output_reg, Register input_reg) {
   ASSERT(!output_reg.is(input_reg));
   Label done;
   li(output_reg, Operand(255));
   // Normal branch: nop in delay slot.
@@ skipping 167 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS