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From: Jeff Law <jeffreyalaw@gmail.com>
To: gcc-patches@gcc.gnu.org
Subject: Re: [Documentation] Correct RTL documentation: (use (mem ...)) is allowed.
Date: Tue, 27 Sep 2022 09:13:17 -0600	[thread overview]
Message-ID: <0b5d2b5d-fccb-ff3d-d1cc-5276e914f6da@gmail.com> (raw)
In-Reply-To: <06f201d89e76$4ddb3210$e9919630$@nextmovesoftware.com>


On 7/23/22 03:26, Roger Sayle wrote:
> This patch is a one line correction/clarification to GCC's current
> RTL documentation that explains a USE of a MEM is permissible.
>
> PR rtl-optimization/99930 is an interesting example on x86_64 where
> the backend generates better code when a USE is a (const) MEM than
> when it is a REG. In fact the backend relies on CSE to propagate the
> MEM (a constant pool reference) into the USE, to enable combine to
> merge/simplify instructions.
>
> This change has been tested with a make bootstrap, but as it might
> provoke a discussion, I've decided to not consider it "obvious".
> Ok for mainline (to document the actual current behavior)?
>
>
> 2022-07-23  Roger Sayle   <roger@nextmovesoftware.com>
>
> gcc/ChangeLog
>          * doc/rtl.texi (use): Document that the operand may be a MEM.

Given this is documenting existing behavior and it's not hard to 
envision the MEM being useful in this context.  OK.

jeff



  reply	other threads:[~2022-09-27 15:13 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-23  9:26 Roger Sayle
2022-09-27 15:13 ` Jeff Law [this message]
2022-09-28  9:38   ` Uros Bizjak

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