Free one bit in Map by removing unused retaining counter.

src/mips/builtins-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_MIPS
 
 #include "src/codegen.h"
 #include "src/debug/debug.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 405 matching lines @@
         // t4: JSObject (tagged)
         // t5: First in-object property of JSObject (not tagged)
         __ LoadRoot(t7, Heap::kUndefinedValueRootIndex);
 
         if (!is_api_function) {
           Label no_inobject_slack_tracking;
 
           MemOperand bit_field3 = FieldMemOperand(a2, Map::kBitField3Offset);
           // Check if slack tracking is enabled.
           __ lw(t0, bit_field3);
-          __ DecodeField<Map::Counter>(t2, t0);
+          __ DecodeField<Map::ConstructionCounter>(t2, t0);
           // t2: slack tracking counter
           __ Branch(&no_inobject_slack_tracking, lt, t2,
                     Operand(Map::kSlackTrackingCounterEnd));
           // Decrease generous allocation count.
-          __ Subu(t0, t0, Operand(1 << Map::Counter::kShift));
+          __ Subu(t0, t0, Operand(1 << Map::ConstructionCounter::kShift));
           __ sw(t0, bit_field3);
 
           // Allocate object with a slack.
           __ lbu(a0, FieldMemOperand(a2, Map::kUnusedPropertyFieldsOffset));
           __ sll(a0, a0, kPointerSizeLog2);
           __ subu(a0, t3, a0);
           // a0: offset of first field after pre-allocated fields
           if (FLAG_debug_code) {
             __ Assert(le, kUnexpectedNumberOfPreAllocatedPropertyFields, t5,
                       Operand(a0));
@@ skipping 1518 matching lines @@
   }
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS