HLoadNamedField for Smis optimized for x64

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 2825 matching lines @@
     XMMRegister result = ToDoubleRegister(instr->result());
     __ movsd(result, FieldOperand(object, offset));
     return;
   }
 
   Register result = ToRegister(instr->result());
   if (!access.IsInobject()) {
     __ movq(result, FieldOperand(object, JSObject::kPropertiesOffset));
     object = result;
   }
-  __ Load(result, FieldOperand(object, offset), access.representation());
+
+  Representation representation = access.representation();
+  if (representation.IsSmi() &&
+      instr->hydrogen()->representation().IsInteger32()) {
+    // Read int value directly from upper half of the smi.
+    offset += kPointerSize / 2;

[Toon Verwaest, 2013/12/09 13:49:44]

If there's a kSmiTagSize, please use that instead.

[Igor Sheludko, 2013/12/09 16:10:36]

There's no such constant. I'll add static assert instead which will serve both
as a check and as a notice that the code below depends on smi's layout:
STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 32);

+    representation = Representation::Integer32();
+  }
+  __ Load(result, FieldOperand(object, offset), representation);
 }
 
 
 void LCodeGen::DoLoadNamedGeneric(LLoadNamedGeneric* instr) {
   ASSERT(ToRegister(instr->context()).is(rsi));
   ASSERT(ToRegister(instr->object()).is(rax));
   ASSERT(ToRegister(instr->result()).is(rax));
 
   __ Move(rcx, instr->name());
   Handle<Code> ic = isolate()->builtins()->LoadIC_Initialize();
@@ skipping 2725 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64