Re: [PATCH][ARM] Fix wrong code by arm_final_prescan with fp16 move instructions

[Sudakshina Das <sudi.das@arm.com>]

On 30/11/17 16:07, Kyrill Tkachov wrote:
>
> 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.
>

Committed as r255301 on trunk. Will wait for a week before committing to 
gcc-7.

Thanks
Sudi

> 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.
>> >
>>
>