From: Mark Mitchell <mark@codesourcery.com>
To: Eric Botcazou <ebotcazou@libertysurf.fr>
Cc: Jakub Jelinek <jakub@redhat.com>,
gcc@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: GCC Status Report (2004-03-09)
Date: Fri, 19 Mar 2004 19:29:00 -0000 [thread overview]
Message-ID: <405B302B.40006@codesourcery.com> (raw)
In-Reply-To: <200403191413.10043.ebotcazou@libertysurf.fr>
Eric Botcazou wrote:
>>Can't we at least detect the case where either the whole aggregate
>>is const or all its fields are const? Then we don't need any blockage.
>>
>>
>
>Guess what? The constness is not propagated to the RTL in the former case,
>because of the pessimization recently introduced in maybe_set_unchanging:
>
> We cannot do this for non-static aggregates, because of the double
> writes that can be generated by store_constructor, depending on the
> contents of the initializer. Yes, this does eliminate a good fraction
> of the number of uses of RTX_UNCHANGING_P for a language like Ada.
> It also eliminates a good quantity of bugs. Let this be incentive to
> eliminate RTX_UNCHANGING_P entirely in favor of a more reliable
> solution, perhaps based on alias sets. */
>
>This means that const automatic aggregates would take a double pessimization
>with the blockage scheme.
>
>
Well, so, let's remove that chunk of code; it should no longer be needed.
Eric, I can tell you're unhappy with this approach, and so you're
casting about for something better. That's good, but I think we've come
as far as we can for 3.4.0. If all this is sufficiently annoyhing to
you, maybe you can work on ripping out RTX_UNCHANGING_P for 3.5 and
replacing it with something better!
--
Mark Mitchell
CodeSourcery, LLC
(916) 791-8304
mark@codesourcery.com
next prev parent reply other threads:[~2004-03-19 17:38 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-09 18:09 Mark Mitchell
2004-03-11 9:45 ` Eric Botcazou
2004-03-11 12:48 ` Jakub Jelinek
2004-03-11 21:11 ` Richard Henderson
2004-03-16 16:53 ` Mark Mitchell
2004-03-16 16:59 ` Paul Koning
2004-03-16 17:11 ` Ian Lance Taylor
2004-03-16 17:24 ` Zack Weinberg
2004-03-16 17:25 ` Paul Koning
2004-03-17 10:56 ` Eric Botcazou
2004-03-17 11:49 ` Eric Botcazou
2004-03-17 15:55 ` Mark Mitchell
2004-03-18 8:25 ` Eric Botcazou
2004-03-18 18:31 ` Eric Botcazou
2004-03-18 19:15 ` Mark Mitchell
2004-03-18 23:36 ` Eric Botcazou
2004-03-18 23:41 ` Jakub Jelinek
2004-03-19 1:23 ` Eric Botcazou
2004-03-19 14:31 ` Eric Botcazou
2004-03-19 19:29 ` Mark Mitchell [this message]
2004-03-19 20:04 ` Eric Botcazou
2004-03-19 20:23 ` Mark Mitchell
2004-03-20 19:51 ` Eric Botcazou
[not found] ` <405A3F26.2050100@codesourcery.com>
[not found] ` <200403190155.18981.ebotcazou@libertysurf.fr>
2004-03-19 6:42 ` Mark Mitchell
2004-03-16 2:09 ` C++ status (Was: GCC Status Report (2004-03-09)) Giovanni Bajo
2004-03-11 12:15 GCC Status Report (2004-03-09) Richard Kenner
2004-03-11 12:39 ` Eric Botcazou
2004-03-11 12:49 Richard Kenner
2004-03-11 14:09 ` Eric Botcazou
2004-03-19 6:34 Richard Kenner
2004-03-19 12:18 ` Jakub Jelinek
2004-03-19 14:22 Richard Kenner
2004-03-19 20:08 Richard Kenner
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