MIPS: Support fast case for-in in Crankshaft.

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
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5075 matching lines @@
                                              Register descriptors) {
   lw(descriptors,
      FieldMemOperand(map, Map::kInstanceDescriptorsOrBitField3Offset));
   Label not_smi;
   JumpIfNotSmi(descriptors, &not_smi);
   li(descriptors, Operand(FACTORY->empty_descriptor_array()));
   bind(&not_smi);
 }
 
 
+void MacroAssembler::CheckEnumCache(Register null_value, Label* call_runtime) {
+  Label next;
+  // Preload a couple of values used in the loop.
+  Register  empty_fixed_array_value = t2;
+  LoadRoot(empty_fixed_array_value, Heap::kEmptyFixedArrayRootIndex);
+  Register empty_descriptor_array_value = t3;
+  LoadRoot(empty_descriptor_array_value,
+           Heap::kEmptyDescriptorArrayRootIndex);
+  mov(a1, a0);
+  bind(&next);
+
+  // Check that there are no elements.  Register a1 contains the
+  // current JS object we've reached through the prototype chain.
+  lw(a2, FieldMemOperand(a1, JSObject::kElementsOffset));
+  Branch(call_runtime, ne, a2, Operand(empty_fixed_array_value));
+
+  // Check that instance descriptors are not empty so that we can
+  // check for an enum cache.  Leave the map in a2 for the subsequent
+  // prototype load.
+  lw(a2, FieldMemOperand(a1, HeapObject::kMapOffset));
+  lw(a3, FieldMemOperand(a2, Map::kInstanceDescriptorsOrBitField3Offset));
+  JumpIfSmi(a3, call_runtime);
+
+  // Check that there is an enum cache in the non-empty instance
+  // descriptors (a3).  This is the case if the next enumeration
+  // index field does not contain a smi.
+  lw(a3, FieldMemOperand(a3, DescriptorArray::kEnumerationIndexOffset));
+  JumpIfSmi(a3, call_runtime);
+
+  // For all objects but the receiver, check that the cache is empty.
+  Label check_prototype;
+  Branch(&check_prototype, eq, a1, Operand(a0));
+  lw(a3, FieldMemOperand(a3, DescriptorArray::kEnumCacheBridgeCacheOffset));
+  Branch(call_runtime, ne, a3, Operand(empty_fixed_array_value));
+
+  // Load the prototype from the map and loop if non-null.
+  bind(&check_prototype);
+  lw(a1, FieldMemOperand(a2, Map::kPrototypeOffset));
+  Branch(&next, ne, a1, 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.
   Branch(&done, gt, input_reg, Operand(output_reg));
   // Use delay slot in this branch.
   Branch(USE_DELAY_SLOT, &done, lt, input_reg, Operand(zero_reg));
   mov(output_reg, zero_reg);  // In delay slot.
   mov(output_reg, input_reg);  // Value is in range 0..255.
@@ skipping 91 matching lines @@
        opcode == BGTZL);
   opcode = (cond == eq) ? BEQ : BNE;
   instr = (instr & ~kOpcodeMask) | opcode;
   masm_.emit(instr);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS