Patch by Geoffrey Garen <ggaren@apple.com> on 2009-10-01
Reviewed by Sam Weinig.

1.1% SunSpider speedup.

* jit/JITCall.cpp:
(JSC::JIT::compileOpCall):
* jit/JITOpcodes.cpp:
(JSC::JIT::emit_op_to_jsnumber):
(JSC::JIT::emit_op_create_arguments):
* jit/JITPropertyAccess.cpp:
(JSC::JIT::emitSlow_op_get_by_val):
(JSC::JIT::emit_op_put_by_val): Test for the empty value tag, instead
of testing for the cell tag with a 0 payload.

* runtime/JSValue.cpp:
(JSC::JSValue::description): Added support for dumping the new empty value,
and deleted values, in debug builds.

* runtime/JSValue.h:
(JSC::JSValue::JSValue()): Construct JSValue() with the empty value tag.

(JSC::JSValue::JSValue(JSCell*)): Convert null pointer to the empty value
tag, to avoid having two different c++ versions of null / empty.

(JSC::JSValue::operator bool): Test for the empty value tag, instead
of testing for the cell tag with a 0 payload.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@49004 268f45cc-cd09-0410-ab3c-d52691b4dbfc