From: hlu@eecs.wsu.edu (H.J. Lu) Subject: ANNOUNCE: effects of-fomit-frame-pointer Date: Fri, 2 Oct 1992 03:52:31 GMT
> To: hlu@eecs.wsu.edu
> Cc: rms@gnu.ai.mit.edu
> Subject: Re: Linux patches for ss-920925
>
> > From: H.J. Lu <hlu@irl.eecs.wsu.edu>
> > Date: Wed, 30 Sep 92 16:18:31 PDT
>
> > One thing puzzles me a lot recently. I compiled gcc ss-920925 with -O2
> > and -O2 -fomit-frame-pointer. I expected by adding -fomit-frame-pointer
> > I would get the smaller binaries. But quite the opposite, with -O2, I
> > got
>
> | I have no idea why. The only way to find out is by comparing the
> | assembler code. If you want to do this, please tell me what you find.
>
> Addressing modes that offset the stack pointer are one byte longer than
> addressing modes that offset the frame pointer. -fomit-frame-pointer
> only wins if you can get better register allocation by freeing up the
> frame pointer for reloading.
> ---
> James R. Van Artsdalen james@bigtex.cactus.org "Live Free or Die"
> Dell Computer Co 9505 Arboretum Blvd Austin TX 78759 512-338-8789
>
-fomit-frame-pointer may give fewer assembler codes, but bigger machine
codes in certain circumstances.
H.J.