Fixing dead code in empty array init.

src/ia32/builtins-ia32.cc

Index: src/ia32/builtins-ia32.cc
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index 70e342d3d7832e9edfd037b4eeff081526db6182..603a48a5f53497359da8e60c87208720bebf2971 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -996,6 +996,7 @@ static void AllocateEmptyJSArray(MacroAssembler* masm,
     }
   } else {
     Label loop, entry;
+    __ add(scratch1, Immediate(FixedArray::kHeaderSize - kHeapObjectTag));

[Kevin Millikin (Chromium), 2011/10/27 10:35:54]

On ia32, there's usually no need to untag like this because we can build
untagging into the operand's offset.  (See FieldOperand.)

In this case, we can get slightly tighter loop by using a counted loop,
something like:

    mov scratch2, initial_capacity
    jmp entry
loop:
    mov FieldOperand(scratch1, scratch2, kPointerSize, 0), the_hole_value
entry:
    dec scratch2
    j not_sign, loop

     __ jmp(&entry);
     __ bind(&loop);
     __ mov(Operand(scratch1, 0), factory->the_hole_value());