HLoadNamedField for Smis optimized for x64

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 7c9949a1fad8da5b441e7ecd79d96ab41dbea073..f3a10266af293208b021e2a12f8c925779ff3470 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2843,7 +2843,15 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
     __ 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);
 }