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Re: unwind info for epilogues
- From: Richard Henderson <rth at redhat dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 01 Jun 2009 11:20:12 -0700
- Subject: Re: unwind info for epilogues
- References: <4A01F133.6070606@redhat.com> <Pine.LNX.4.64.0905062029010.4207@digraph.polyomino.org.uk> <4A2080E4.1050202@redhat.com> <20090530120707.GL5118@tyan-ft48-01.lab.bos.redhat.com> <4A21A120.3000009@redhat.com> <20090601171000.GF18874@tyan-ft48-01.lab.bos.redhat.com>
Jakub Jelinek wrote:
(I believe at least the removal of .cfi_restore because of red-zone
is something that is difficult to do in the middle-end, since it doesn't
know anything about red-zone).
Possibly, though it wouldn't be that hard to teach the middle-end
about a red-zone. I think this approach is certainly useful in
the short-term before a middle-end pass exists.
+ /* Calculate start of saved registers relative to esp on entry of the
+ function. When realigning stack, this needs to be smallest possible
+ value at runtime. */
+ red_offset = offset;
+ if (using_drap)
+ red_offset -= crtl->stack_alignment_needed / BITS_PER_UNIT
+ + UNITS_PER_WORD;
+ if (frame_pointer_needed)
+ red_offset -= UNITS_PER_WORD;
+ if (stack_realign_fp)
+ red_offset -= crtl->stack_alignment_needed / BITS_PER_UNIT
+ - UNITS_PER_WORD;
Only one of USING_DRAP or STACK_REALIGN_FP, surely? Also, I think
"smallest" is misleading, since it implies (to me) smallest absolute
value, whereas what I think you mean is "most negative" or "largest".
r~