From: Kyrill Tkachov <kyrylo.tkachov@foss.arm.com>
To: Sudi 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: Mon, 27 Nov 2017 12:39:00 -0000 [thread overview]
Message-ID: <5A1C0434.5000109@foss.arm.com> (raw)
In-Reply-To: <4db1e5be-24b1-bab7-d351-b00ef5332728@arm.com>
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?
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:[~2017-11-27 12:25 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 [this message]
2017-11-30 16:08 ` Sudakshina Das
2017-11-30 16:28 ` Kyrill Tkachov
2017-12-01 10:18 ` Sudakshina Das
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