From: Mikael Morin <morin-mikael@orange.fr>
To: Thomas Koenig <tkoenig@netcologne.de>,
Harald Anlauf <anlauf@gmx.de>,
Richard Biener <richard.guenther@gmail.com>
Cc: gcc-patches@gcc.gnu.org, fortran@gcc.gnu.org
Subject: Re: [PATCH 09/10] fortran: Support clobbering of variable subreferences [PR88364]
Date: Wed, 21 Sep 2022 20:56:12 +0200 [thread overview]
Message-ID: <cce9913a-33a9-2810-b34a-3b8c7e8a2eea@orange.fr> (raw)
In-Reply-To: <da330cf1-f6a7-cd56-1a25-40dd6280e81b@netcologne.de>
Le 21/09/2022 à 11:57, Thomas Koenig a écrit :
>
> Hi Harald,
>
>> I think I understand much of what is said, but I feel that I do
>> not really understand what *clobber* means for the different
>> beasts we are discussing (although I have an impression of what
>> it means for a scalar object).
>
> Obviously, "clobber" means taking a big stick and hitting the beast
> in question over the head with it :-)
>
> More seriously: My understanding of a clobber it is a hint to
> the middle end that the value in question will not be used,
> and that operations leading to this value can be removed,
> unless they are used otherwise.
>
My understanding is that "clobber" means "overwrite with garbage" for
all the beasts we have been discussing, which translates to nothing in
the final code, but can be used by the optimizers as Thomas said.
This is a bit off-topic but clobbers model registers having their values
changed unpredictably or by ways unknown to the compiler, in the backend
code, or in inline assembly statements.
Here is an excerpt from rtl.texi:
> @item (clobber @var{x})
> Represents the storing or possible storing of an unpredictable,
> undescribed value into @var{x}
I Hope it helps.
next prev parent reply other threads:[~2022-09-21 18:57 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-16 20:24 [PATCH 00/10] fortran: clobber fixes [PR41453] Mikael Morin
2022-09-16 20:24 ` [PATCH 01/10] fortran: Move the clobber generation code Mikael Morin
2022-09-16 20:24 ` [PATCH 02/10] fortran: Fix invalid function decl clobber ICE [PR105012] Mikael Morin
2022-09-16 20:24 ` [PATCH 03/10] fortran: Move clobbers after evaluation of all arguments [PR106817] Mikael Morin
2022-09-16 20:24 ` [PATCH 04/10] fortran: Support clobbering with implicit interfaces [PR105012] Mikael Morin
2022-09-16 20:24 ` [PATCH 05/10] fortran: Support clobbering of reference variables [PR41453] Mikael Morin
2022-09-16 20:24 ` [PATCH 06/10] fortran: Support clobbering of SAVE variables [PR87395] Mikael Morin
2022-09-16 20:24 ` [PATCH 07/10] fortran: Support clobbering of ASSOCIATE variables [PR87397] Mikael Morin
2022-09-16 20:24 ` [PATCH 08/10] fortran: Support clobbering of allocatables and pointers [PR41453] Mikael Morin
2022-09-16 20:24 ` [PATCH 09/10] fortran: Support clobbering of variable subreferences [PR88364] Mikael Morin
2022-09-17 17:03 ` Thomas Koenig
2022-09-17 19:33 ` Mikael Morin
2022-09-17 19:49 ` Bernhard Reutner-Fischer
2022-09-17 19:50 ` Mikael Morin
2022-09-17 21:24 ` Bernhard Reutner-Fischer
2022-09-18 6:12 ` Richard Biener
2022-09-18 9:10 ` Mikael Morin
2022-09-18 10:23 ` Thomas Koenig
2022-09-18 18:32 ` Harald Anlauf
2022-09-18 20:55 ` Mikael Morin
2022-09-19 7:11 ` Mikael Morin
2022-09-19 19:46 ` Harald Anlauf
2022-09-19 20:50 ` Mikael Morin
2022-09-20 6:54 ` Thomas Koenig
2022-09-20 8:46 ` Mikael Morin
2022-09-20 21:08 ` Harald Anlauf
2022-09-20 21:08 ` Harald Anlauf
2022-09-21 9:57 ` Thomas Koenig
2022-09-21 18:56 ` Mikael Morin [this message]
2022-09-21 19:12 ` Harald Anlauf
2022-09-21 19:12 ` Harald Anlauf
2022-09-18 20:43 ` Mikael Morin
2022-09-18 10:48 ` Richard Biener
2022-09-19 7:31 ` Mikael Morin
2022-09-19 7:58 ` Richard Biener
2022-09-16 20:24 ` [PATCH 10/10] fortran: Support clobbering of derived types [PR41453] Mikael Morin
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