Re: PING: PATCH: Do not clear the DECL_BIT_FIELD flag (prelude to ObjC fix)

[Ziemowit Laski <zlaski@apple.com>]

On Tuesday, Aug 13, 2002, at 18:37 US/Pacific, Richard Kenner wrote:

>     What kind of performance problems were you thinking of?
>
> Well, DECL_BIT_FIELD means to use bitfield access techniques, which add
> code.  If we use them when we don't need to, we generate worse code.

You mean the back-end isn't smart enough to detect bitfields that
could be accessed as bytes or words?

>
>     I suppose the ObjC front-end could be taught to keep separate
>     copies of instance variables for super classes lest they get
>     side-effected too often, but that is terribly kludgey.
>
> Why not just use a language-specific flag instead of DECL_BIT_FIELD?

Because the instance variables of ObjC classes are parsed/handled by
the same machinery as fields in a C struct.  And for a good reason --
ObjC classes _are_ C structs (among other things).

--Zem
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Ziemowit Laski                 1 Infinite Loop, MS 301-2K
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