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From: Richard Sandiford <richard.sandiford@arm.com>
To: gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] doc: Update documentation on MODE_PARTIAL_INT subregs
Date: Mon, 07 Sep 2020 13:55:59 +0100	[thread overview]
Message-ID: <mptft7tu4o0.fsf@arm.com> (raw)
In-Reply-To: <20200831165915.jzly4pgtadxcvpxp@jozef-acer-manjaro> (Jozef Lawrynowicz's message of "Mon, 31 Aug 2020 17:59:15 +0100")

Jozef Lawrynowicz <jozef.l@mittosystems.com> writes:
> In d8487c949ad5 (~GCC 4.9.0), MODE_PARTIAL_INT modes were changed from
> having an unknown number of undefined bits, to having a known number of
> undefined bits, however the documentation on using SUBREG expressions
> with MODE_PARTIAL_INT modes was not updated to reflect this.
>
> The attached patch updates that portion of the GCC internals
> documentation.
>
> Ok for trunk?

Thanks for doing this.  OK for trunk with one very minor nit:

> -does not guarantee that @samp{(subreg:HI (reg:PSI 0) 0)} has the
> -value @samp{(reg:HI 4)}.
> +sets the low 16 bits of @samp{(reg:PSI 0)} to @samp{(reg:HI 4)}, and
> +the high 4 defined bits of @samp{(reg:PSI 0)} retain their
> +original value.  The behavior here is therefore the same as

IMO reads more naturally as “the same as for”.

Richard

> +normal @code{subreg}s, when there are no
> +@code{MODE_PARTIAL_INT} modes involved.
>  
>  @cindex @code{TARGET_CAN_CHANGE_MODE_CLASS} and subreg semantics
>  The rules above apply to both pseudo @var{reg}s and hard @var{reg}s.

  reply	other threads:[~2020-09-07 12:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-31 16:59 Jozef Lawrynowicz
2020-09-07 12:55 ` Richard Sandiford [this message]
2020-09-07 16:56   ` Jozef Lawrynowicz

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