From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
To: Sudakshina Das <sudi.das@arm.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: nd <nd@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>
Subject: Re: [PATCH][ARM] Fix wrong code by arm_final_prescan with fp16 move instructions
Date: Thu, 30 Nov 2017 16:28:00 -0000 [thread overview]
Message-ID: <5A202CDE.10906@foss.arm.com> (raw)
In-Reply-To: <2662e77b-cf75-8072-d6ef-14e184ce95c1@arm.com>
On 30/11/17 16:06, Sudakshina Das wrote:
> Hi Kyrill
>
> On 27/11/17 12:25, Kyrill Tkachov wrote:
> > Hi Sudi,
> >
> > On 24/11/17 14:57, Sudi Das wrote:
> >> Hi
> >>
> >> For the following test case:
> >> __fp16
> >> test_select (__fp16 a, __fp16 b, __fp16 c)
> >> {
> >> return (a < b) ? b : c;
> >> }
> >>
> >> when compiled with -mfpu=fp-armv8 -march=armv8.2-a+fp16 -marm
> >> -mfloat-abi=hard trunk generates wrong code:
> >>
> >> test_select:
> >> @ args = 0, pretend = 0, frame = 0
> >> @ frame_needed = 0, uses_anonymous_args = 0
> >> @ link register save eliminated.
> >> vcvtb.f32.f16 s0, s0
> >> vcvtb.f32.f16 s15, s1
> >> vcmpe.f32 s0, s15
> >> vmrs APSR_nzcv, FPSCR
> >> // <------ No conditional branch!
> >> vmov s1, s2 @ __fp16
> >> .L2:
> >> vmov s0, s1 @ __fp16
> >> bx lr
> >>
> >> There should have been a conditional branch there to skip one of the
> >> VMOVs.
> >> This patch fixes this problem by making *movhf_vfp_fp16 unconditional
> >> wherever needed.
> >>
> >> Testing done: Add a new test case and checked for regressions
> >> arm-none-linux-gnueabihf.
> >>
> >> Is this ok for trunk?
> >>
> >
> > This is ok after assuming a bootstrap on arm-none-linux-gnueabihf passes
> > as well.
> > Does this bug appear on the GCC 7 branch?
> > If so, could you please test this patch on that branch as well if so?
> >
>
> I have tested the patch and also sent a new patch request for gcc-7
> https://gcc.gnu.org/ml/gcc-patches/2017-11/msg02577.html
>
Thanks Sudi, this is ok to commit to the branch after we let this patch
bake on trunk for a week without problems.
Kyrill
> Thanks
> Sudi
>
> > Thanks,
> > Kyrill
> >
> >> Sudi
> >>
> >> ChangeLog entry are as follow:
> >>
> >> *** gcc/ChangeLog ***
> >>
> >> 2017-11-24 Sudakshina Das <sudi.das@arm.com>
> >>
> >> * config/arm/vfp.md (*movhf_vfp_fp16): Add conds attribute.
> >>
> >> *** gcc/testsuite/ChangeLog ***
> >>
> >> 2017-11-24 Sudakshina Das <sudi.das@arm.com>
> >>
> >> * gcc.target/arm/armv8_2-fp16-move-2.c: New test.
> >
>
next prev parent reply other threads:[~2017-11-30 16:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-24 15:44 Sudakshina Das
2017-11-27 12:39 ` Kyrill Tkachov
2017-11-30 16:08 ` Sudakshina Das
2017-11-30 16:28 ` Kyrill Tkachov [this message]
2017-12-01 10:18 ` Sudakshina Das
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