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From: "kkojima at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/50751] SH Target: Displacement addressing does not work for QImode and HImode
Date: Mon, 12 Dec 2011 22:16:00 -0000	[thread overview]
Message-ID: <bug-50751-4-JVUHwuJ1Kv@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-50751-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50751

--- Comment #21 from Kazumoto Kojima <kkojima at gcc dot gnu.org> 2011-12-12 22:08:18 UTC ---
(In reply to comment #20)
> As far as I could observe it, this is mainly triggered by the following in
> sh_legitimate_index_p:
>
> +      if (mode == QImode && (unsigned) INTVAL (op) < 16)
> +    return true;

It seems that, with that hunk, recog.c:offsettable_address_addr_space_p
returns always true for V2SF mode.  Without that hunk, it returns false
for that case.  There are comments and lines in that function like

      /* Use QImode because an odd displacement may be automatically invalid
     for any wider mode.  But it should be valid for a single byte.  */
      good = (*addressp) (QImode, y, as);

where addrssp is *memory_address_addr_space_p which returns true with
that hunk.

> You mean, by giving the user the option to turn off displacement addressing for
> e.g. some specific files / modules by specifying -mno-preferdisp or something
> like that?  By anomalies do you mean code that gets worse because of too much
> pressure on R0 and all the reloads around it, or do you have any other bad use
> cases?

Yes and yes.  Although I didn't look all dis-improvements,
it looks r0 pressure is the primary factor.

> Another thing I could try out is to have load/store insns that allow arbitrary
> operands in displacement addressing like on SH2A, and split them into two insns
> of one load/store and one reg-reg move after reload.  But that would probably
> require the R0 clobber in the expander which could make worse code in cases
> where displacement addressing is not used, I guess.
> Do you think this approach could make sense?

I guess that it could make worse code in some situations as you say.

> Yep, sure.  I've noticed that the latest version of the patch seems to fix some
> more testsuite failures.  I will investigate which hunk is responsible for the
> fixes so that could be pulled out from the patch.  OK?

Sounds great.


  parent reply	other threads:[~2011-12-12 22:08 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-16 22:56 [Bug target/50751] New: " oleg.endo@t-online.de
2011-10-17  0:30 ` [Bug target/50751] " kkojima at gcc dot gnu.org
2011-10-17  0:38 ` oleg.endo@t-online.de
2011-10-17  0:51 ` kkojima at gcc dot gnu.org
2011-10-23 21:57 ` oleg.endo@t-online.de
2011-10-24 23:05 ` kkojima at gcc dot gnu.org
2011-10-26 22:37 ` oleg.endo@t-online.de
2011-10-26 23:07 ` oleg.endo@t-online.de
2011-10-27  2:31 ` kkojima at gcc dot gnu.org
2011-10-27  9:31 ` oleg.endo@t-online.de
2011-10-27 21:11 ` oleg.endo@t-online.de
2011-10-27 21:54 ` oleg.endo@t-online.de
2011-10-27 22:35 ` kkojima at gcc dot gnu.org
2011-11-02  0:16 ` oleg.endo@t-online.de
2011-11-02  0:58 ` kkojima at gcc dot gnu.org
2011-11-02  1:38 ` oleg.endo@t-online.de
2011-11-18  0:03 ` oleg.endo@t-online.de
2011-11-28 13:18 ` oleg.endo@t-online.de
2011-12-11  1:00 ` oleg.endo@t-online.de
2011-12-12  2:11 ` kkojima at gcc dot gnu.org
2011-12-12  2:29 ` oleg.endo@t-online.de
2011-12-12 22:16 ` kkojima at gcc dot gnu.org [this message]
2012-02-26 23:24 ` olegendo at gcc dot gnu.org
2012-03-19 19:19 ` olegendo at gcc dot gnu.org
2012-03-21 20:39 ` olegendo at gcc dot gnu.org
2012-03-27 20:37 ` olegendo at gcc dot gnu.org
2012-04-05 18:44 ` olegendo at gcc dot gnu.org
2012-04-11 11:35 ` olegendo at gcc dot gnu.org
2012-04-11 23:01 ` olegendo at gcc dot gnu.org
2012-04-19  9:31 ` olegendo at gcc dot gnu.org
2012-04-30 19:38 ` olegendo at gcc dot gnu.org
2012-08-09 15:51 ` olegendo at gcc dot gnu.org
2012-08-14 17:54 ` olegendo at gcc dot gnu.org
2013-11-26 11:48 ` olegendo at gcc dot gnu.org
2013-12-06 19:34 ` olegendo at gcc dot gnu.org
2013-12-08 14:19 ` olegendo at gcc dot gnu.org
2014-09-12 17:29 ` olegendo at gcc dot gnu.org
2014-12-07 22:57 ` olegendo at gcc dot gnu.org
2014-12-07 22:59 ` olegendo at gcc dot gnu.org
2014-12-07 23:01 ` olegendo at gcc dot gnu.org
2015-02-08 22:26 ` olegendo at gcc dot gnu.org

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