Re: gniibe@m17n.org: Re: target/4516: [SH] sh-unknown-linux-gnu: big jump table

[Jan Hubicka <jh at suse dot cz>]

> 
>         (CASE_VECTOR_MODE): Always SImode.  Starting from QImode (or
>         HImode) may result assembler error of "pcrel too far" (e.g.
>         compiling f/symbol.c).  It's because barrier_align depends
>         on the mode.
> 
> This kind of information doesn't belong into the ChangeLog, but in the
> explanation of the patch and comments in the source.
> 
> Anyways, the problem appears to be that alignments are computed only
> once, while we would like them to be recomputed during each iteration
> of shorten_branches.
> Actually, it is a lot wors today than it was haf a year ago, since originally
> the alignments were calculated with each invocation of shorten_branches, while
> now they are computed only once; and the new code is not even suitable to
> compute at shorten_branches time.
> 
> Mon Aug 20 01:44:50 CEST 2001  Jan Hubicka  <jh@suse.cz>
> 
>         * final.c (compute_alignments): New function.
>         (init_insn_lengths): Do not care label_align.
>         (LABEL_ALIGN_AFTER_BARRIER): Default to 1.
>         (LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP): Default to 0.
>         (JUMP_ALIGN, JUMP_ALIGN_MAX_SKIP): New.
>         (shorted_branches): Realloc label_align array; do
>         not call init_insn_lengths; Do not care about loop alignments.
>         * output.h (compute_alignments): Declare.
>         * toplev.c (rest_of_compilation): Call compute_alignments.
>         * tm.texi (JUMP_ALIGN, JUMP_ALIGN_MAX_SKIP): Document.
> 
> This change makes also the impact of changing CASE_VECTOR_MODE to be SImode
> worse,
> since we don't pick up shortened modes at the second invocation of
> shorten_branches.
> 
> Jan, what was the point of making the alignemnt computation depend on an
> up-to-date
> flowgraph?

Yes, I need flowgraph and profile info in order to set up the alignments.  It
should not be dificult to recompute alignment of case vectors in
shorten_branches in case it depends on the status of it (I didn't expected
something like that to be possible)

Honza
> 
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