From: Peter Bergner <bergner@linux.ibm.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: David Edelsohn <dje.gcc@gmail.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Bill Schmidt <wschmidt@linux.ibm.com>,
Rajalakshmi Srinivasaraghavan <rajis@linux.ibm.com>
Subject: Re: [PATCH] rs6000: MMA test case emits wrong code when building a vector pair
Date: Tue, 16 Nov 2021 12:18:50 -0600 [thread overview]
Message-ID: <40dc497d-9e87-63f3-5836-00518bd4be5a@linux.ibm.com> (raw)
In-Reply-To: <20211113132509.GM614@gate.crashing.org>
On 11/13/21 7:25 AM, Segher Boessenkool wrote:
> On Wed, Oct 27, 2021 at 08:37:57PM -0500, Peter Bergner wrote:
>> PR102976 shows a test case where we generate wrong code when building
>> a vector pair from 2 vector registers. The bug here is that with unlucky
>> register assignments, we can clobber one of the input operands before
>> we write both registers of the output operand. The solution is to use
>> early-clobbers in the assemble pair and accumulator patterns.
>
> Because of what insns there are after the split. Aha.
>
> Please add a comment explaining this, near the earlyclobber itself.
Done for both patterns.
> You can just write this as {\mxxlor \d+,44,44\M} etc., that will be
> simplest I think.
Done and tested that it still works.
> Okay for trunk with comments added near the earlyclobber, and the RE
> improved. Also fine for 11 after some burn-in. Thanks!
Ok, I pushed with both changes. I'll push a change to GCC11 in a few days.
Thanks!
Peter
prev parent reply other threads:[~2021-11-16 18:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 1:37 Peter Bergner
2021-11-12 19:49 ` PING: " Peter Bergner
2021-11-13 13:25 ` Segher Boessenkool
2021-11-16 18:18 ` Peter Bergner [this message]
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