Re: [PATCH 8/17][ARM] Add VFP FP16 arithmetic instructions.

[Ramana Radhakrishnan <ramana dot gcc at googlemail dot com>]

On Mon, Jul 4, 2016 at 3:02 PM, Matthew Wahab
<matthew.wahab@foss.arm.com> wrote:
> On 19/05/16 15:54, Matthew Wahab wrote:
>> On 18/05/16 16:20, Joseph Myers wrote:
>>> On Wed, 18 May 2016, Matthew Wahab wrote:
>>>
>>> In short: instructions for direct HFmode arithmetic should be described
>>> with patterns with the standard names.  It's the job of the
>>> architecture-independent compiler to ensure that fp16 arithmetic in the
>>> user's source code only generates direct fp16 arithmetic in GIMPLE (and
>>> thus ends up using those patterns) if that is a correct representation of
>>> the source code's semantics according to ACLE.
>>>
>>> The intrinsics you provide can then be written to use direct arithmetic,
>>> and rely on convert_to_real_1 eliminating the promotions, rather than
>>> needing built-in functions at all, just like many arm_neon.h intrinsics
>>> make direct use of GNU C vector arithmetic.
>>
>> I think it's clear that this has exhausted my knowledge of FP semantics.
>>
>> Forcing promotion to single-precision was to settle concerns brought up in
>> internal discussions about __fp16 semantics. I'll see if anybody has any
>> problem with the changes you suggest.
>
> This patch changes the implementation to use the standard names for the
> HFmode arithmetic. Later patches will also be updated to use the
> arithmetic operators where appropriate.
>
> Changes since the last version of this patch:
> - The standard names for plus, minus, mult, div and fma are defined for
>   HF mode.
> - The patterns supporting the new ACLE intrinsics vnegh_f16, vaddh_f16,
>   vsubh_f16, vmulh_f16 and vdivh_f16 are removed, the arithmetic
>   operators will be used instead.
> - The tests are updated to expect f16 instructions rather than the f32
>   instructions that were previously emitted.
>
> Tested the series for arm-none-linux-gnueabihf with native bootstrap and
> make check and for arm-none-eabi and armeb-none-eabi with make check on
> an ARMv8.2-A emulator.


All fine except -

Why can we not extend the <vrint_pattern> and the l<vrint_pattern> in
vfp.md for fp16 and avoid all the unspecs for vcvta and vrnd*
instructions ?

Ramana




>
> Ok for trunk?
> Matthew
>
> 2016-07-04  Matthew Wahab  <matthew.wahab@arm.com>
>
>         * config/arm/iterators.md (Code iterators): Fix some white-space
>         in the comments.
>         (GLTE): New.
>         (ABSNEG): New
>         (FCVT): Moved from vfp.md.
>         (VCVT_HF_US_N): New.
>         (VCVT_SI_US_N): New.
>         (VCVT_HF_US): New.
>         (VCVTH_US): New.
>         (FP16_RND): New.
>         (absneg_str): New.
>         (FCVTI32typename): Moved from vfp.md.
>         (sup): Add UNSPEC_VCVTA_S, UNSPEC_VCVTA_U, UNSPEC_VCVTM_S,
>         UNSPEC_VCVTM_U, UNSPEC_VCVTN_S, UNSPEC_VCVTN_U, UNSPEC_VCVTP_S,
>         UNSPEC_VCVTP_U, UNSPEC_VCVT_HF_S_N, UNSPEC_VCVT_HF_U_N,
>         UNSPEC_VCVT_SI_S_N, UNSPEC_VCVT_SI_U_N,  UNSPEC_VCVTH_S_N,
>         UNSPEC_VCVTH_U_N, UNSPEC_VCVTH_S and UNSPEC_VCVTH_U.
>
>         (vcvth_op): New.
>         (fp16_rnd_str): New.
>         (fp16_rnd_insn): New.


>         * config/arm/unspecs.md (UNSPEC_VCVT_HF_S_N): New.
>         (UNSPEC_VCVT_HF_U_N): New.
>         (UNSPEC_VCVT_SI_S_N): New.
>         (UNSPEC_VCVT_SI_U_N): New.
>         (UNSPEC_VCVTH_S): New.
>         (UNSPEC_VCVTH_U): New.
>         (UNSPEC_VCVTA_S): New.
>         (UNSPEC_VCVTA_U): New.
>         (UNSPEC_VCVTM_S): New.
>         (UNSPEC_VCVTM_U): New.
>         (UNSPEC_VCVTN_S): New.
>         (UNSPEC_VCVTN_U): New.
>         (UNSPEC_VCVTP_S): New.
>         (UNSPEC_VCVTP_U): New.
>         (UNSPEC_VCVTP_S): New.
>         (UNSPEC_VCVTP_U): New.
>         (UNSPEC_VRND): New.
>         (UNSPEC_VRNDA): New.
>         (UNSPEC_VRNDI): New.
>         (UNSPEC_VRNDM): New.
>         (UNSPEC_VRNDN): New.
>         (UNSPEC_VRNDP): New.
>         (UNSPEC_VRNDX): New.
>         * config/arm/vfp.md (<absneg_str>hf2): New.
>         (neon_vabshf): New.
>         (neon_v<fp16_rnd_str>hf): New.
>         (neon_vrndihf): New.
>         (addhf3): New.
>         (subhf3): New.
>         (divhf3): New.
>         (mulhf3): New.
>         (*mulsf3neghf_vfp): New.
>         (*negmulhf3_vfp): New.
>         (*mulsf3addhf_vfp): New.
>         (*mulhf3subhf_vfp): New.
>         (*mulhf3neghfaddhf_vfp): New.
>         (*mulhf3neghfsubhf_vfp): New.
>         (fmahf4): New.
>         (neon_vfmahf): New.
>         (fmsubhf4_fp16): New.
>         (neon_vfmshf): New.
>         (*fnmsubhf4): New.
>         (*fnmaddhf4): New.
>         (neon_vsqrthf): New.
>         (neon_vrsqrtshf): New.
>         (FCVT): Move to iterators.md.
>         (FCVTI32typename): Likewise.
>         (neon_vcvth<sup>hf): New.
>         (neon_vcvth<sup>si): New.
>         (neon_vcvth<sup>_nhf_unspec): New.
>         (neon_vcvth<sup>_nhf): New.
>         (neon_vcvth<sup>_nsi_unspec): New.
>         (neon_vcvth<sup>_nsi): New.
>         (neon_vcvt<vcvth_op>h<sup>si): New.
>         (neon_<fmaxmin_op>hf): New.
>
> testsuite/
> 2016-07-04  Matthew Wahab  <matthew.wahab@arm.com>
>
>
>         * gcc.target/arm/armv8_2-fp16-arith-1.c: New.
>         * gcc.target/arm/armv8_2-fp16-conv-1.c: New.
>