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Re: [PATCH] doloop_optimize miscompiles openssl
Franz Sirl <Franz.Sirl-kernel@lauterbach.com> writes:
> * doloop.c (doloop_modify): Prevent delete_insn() from
> deleting too much. Prefer loop->top over loop->start as
> target for the new JUMP insn.
> Index: gcc/doloop.c
> ===================================================================
> RCS file: /cvs/gcc/egcs/gcc/doloop.c,v
> retrieving revision 1.2
> diff -u -p -r1.2 doloop.c
> --- doloop.c 2000/08/14 20:55:11 1.2
> +++ doloop.c 2000/09/24 22:00:04
> @@ -416,11 +416,14 @@ doloop_modify (loop, iterations, iterati
> }
>
> /* Discard original jump to continue loop. The original compare
> - result may still be live, so it cannot be discarded explicitly. */
> + result may still be live, so it cannot be discarded explicitly.
> + Don't delete too much, increment the use count of the target label. */
> + LABEL_NUSES (JUMP_LABEL (jump_insn))++;
> delete_insn (jump_insn);
> + LABEL_NUSES (JUMP_LABEL (jump_insn))--;
>
> - /* Emit the label that will delimit the start of the loop. */
> - emit_label_after (start_label, loop->start);
> + /* Emit the label that will delimit the top of the loop. */
> + emit_label_after (start_label, loop->top ? loop->top : loop->start);
> LABEL_NUSES (start_label)++;
Franz,
would it work to simply emit the start_label before calling
delete_insn? After all, the label that jump_insn branches to is
really not used after this transformation, right?
--
- Geoffrey Keating <geoffk@cygnus.com>