Add MEGAMORPHIC state support for KeyedStoreIC

src/ic/x64/stub-cache-x64.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.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic/stub-cache.h"
@@ skipping 23 matching lines @@
   ExternalReference key_offset(isolate->stub_cache()->key_reference(table));
   ExternalReference value_offset(isolate->stub_cache()->value_reference(table));
   Label miss;
 
   // Multiply by 3 because there are 3 fields per entry (name, code, map).
   __ leap(offset, Operand(offset, offset, times_2, 0));
 
   __ LoadAddress(kScratchRegister, key_offset);
 
   // Check that the key in the entry matches the name.
-  // Multiply entry offset by 16 to get the entry address. Since the
-  // offset register already holds the entry offset times four, multiply
-  // by a further four.
-  __ cmpl(name, Operand(kScratchRegister, offset, scale_factor, 0));
+  __ cmpp(name, Operand(kScratchRegister, offset, scale_factor, 0));
   __ j(not_equal, &miss);
 
   // Get the map entry from the cache.
   // Use key_offset + kPointerSize * 2, rather than loading map_offset.
+  DCHECK(isolate->stub_cache()->map_reference(table).address() -
+             isolate->stub_cache()->key_reference(table).address() ==
+         kPointerSize * 2);
   __ movp(kScratchRegister,
           Operand(kScratchRegister, offset, scale_factor, kPointerSize * 2));
   __ cmpp(kScratchRegister, FieldOperand(receiver, HeapObject::kMapOffset));
   __ j(not_equal, &miss);
 
   // Get the code entry from the cache.
   __ LoadAddress(kScratchRegister, value_offset);
   __ movp(kScratchRegister, Operand(kScratchRegister, offset, scale_factor, 0));
 
   // Check that the flags match what we're looking for.
@@ skipping 82 matching lines @@
   __ bind(&miss);
   __ IncrementCounter(counters->megamorphic_stub_cache_misses(), 1);
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64