From: James Greenhalgh <james.greenhalgh@arm.com>
To: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
Cc: GCC Patches <gcc-patches@gcc.gnu.org>,
Marcus Shawcroft <marcus.shawcroft@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>, <nd@arm.com>
Subject: Re: [PATCH][AArch64] PR target/70809: Delete aarch64_vmls<mode> pattern
Date: Tue, 17 May 2016 11:05:00 -0000 [thread overview]
Message-ID: <20160517110438.GA8129@arm.com> (raw)
In-Reply-To: <573AF485.9080205@foss.arm.com>
On Tue, May 17, 2016 at 11:37:57AM +0100, Kyrill Tkachov wrote:
> Hi all,
>
> The aarch64_vmls<mode> pattern claims to perform a normal vector
> floating-point multiply-subtract but in fact performs a fused
> multiply-subtract. This is fine when -ffp-contract=fast, but it's not guarded
> on anything so will generate the FMLS instruction even when
> -ffp-contract=off.
>
> The solution is just to delete the pattern. If -ffp-contract=fast then an fma
> operation will have been generated and the fnma<mode>4 would be used to
> generate the FMLS instruction.
>
> Bootstrapped and tested on aarch64-none-linux-gnu.
>
> Ok for trunk and GCC 6 and 5? GCC 4.9 needs a different -mtune option in the
> testcase to trigger the testcase...
OK, thanks.
Please consider the GCC 4.9 backport preapproved with whatever flag is
needed to expose the issue.
Thanks,
James
>
> Thanks,
> Kyrill
>
> 2016-05-17 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
>
> PR target/70809
> * config/aarch64/aarch64-simd.md (aarch64_vmls<mode>): Delete.
>
> 2016-05-17 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
>
> PR target/70809
> * gcc.target/aarch64/pr70809_1.c: New test.
next prev parent reply other threads:[~2016-05-17 11:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-17 10:38 Kyrill Tkachov
2016-05-17 11:05 ` James Greenhalgh [this message]
2016-05-20 9:04 ` Kyrill Tkachov
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