Re: [PATCH v2 3/8] RISC-V: Add Zfhmin/Zhinxmin (with refactoring)

[Tsukasa OI <research_trasio@irq.a4lg.com>]

On 2022/07/07 13:43, Nelson Chu wrote:
> I cannot just use "git am" for this patch, there are too many
> conflicts.  Am I doing something wrong?

No, you are doing right.

I submitted two Zfinx-related patchsets:

-   Quicker patchset
    <https://sourceware.org/pipermail/binutils/2022-June/121416.html>
    <https://github.com/a4lg/binutils-gdb/wiki/riscv_zhinx_quick_fix>
-   Larger patchset
    <https://sourceware.org/pipermail/binutils/2022-June/121441.html>
    <https://github.com/a4lg/binutils-gdb/wiki/riscv_float_combined>

You merged all functional part of quicker one's patches and some of
larger patchset but they were intended to be mutually exclusive (if
quicker one is merged first, I was going to rebase larger patchset and
submit it).

I will rebase remaining patches (from larger patchset) and submit later
(to make merging [for GNU Binutils 2.40] smoother).

Thanks,
Tsukasa

> 
> On Thu, Jul 7, 2022 at 10:57 AM Kito Cheng <kito.cheng@gmail.com> wrote:
>>
>> Hi Andrew:
>>
>> The sound makes sense to me, but personally I would prefer to keep
>> fmv.h for zfh to make that consistent with fmv.* :P
>>
>> Hi Tsukasa, Nelson:
>>
>> I am OK with the current version, and verified with GCC.
>>
>> On Wed, Jul 6, 2022 at 7:19 AM Andrew Waterman <andrew@sifive.com> wrote:
>>>
>>> IMO, we should not add this alias for Zfhmin, reason being that it
>>> would mean FMV.H has different semantics in Zfhmin vs. Zfh.
>>>
>>> Yes, the behavior is the same if the input is a NaN-boxed
>>> half-precision number, but what if it isn't?  Namely, what if the
>>> programmer accidentally uses FMV.H to move a single-precision number?
>>> This would work correctly when assembling for Zfhmin, but would fail
>>> when assembling for Zfh.  Obviously, this is a programming error, but
>>> it still seems a bit unfortunate to me.
>>>
>>> (In fact, we could consider deleting the FMV.H alias altogether--even
>>> for Zfh.  We would then recommend programmers and compilers always use
>>> FMV.S to move half-precision floating-point numbers for both Zfh and
>>> Zfhmin.)
>>>
>>>
>>>
>>> On Tue, Jul 5, 2022 at 7:22 AM Kito Cheng via Binutils
>>> <binutils@sourceware.org> wrote:
>>>>
>>>>> +{"fmv.h",      0, INSN_CLASS_ZFH_OR_ZHINX,   "D,U",       MATCH_FSGNJ_H, MASK_FSGNJ_H, match_rs1_eq_rs2, INSN_ALIAS },
>>>> Maybe we need one more alias for ZFHMIN? like this: {"fmv.h",      0,
>>>> INSN_CLASS_ZFHMIN,   "D,U",       MATCH_FSGNJ_S, MASK_FSGNJ_S,
>>>> match_rs1_eq_rs2, INSN_ALIAS },
>>>>
>>>> ---
>>>> Spec say:
>>>> Zfhmin does not include the FSGNJ.H instruction, because it suffices to
>>>> instead use the FSGNJ.S instruction to move half-precision values between
>>>> floating-point registers.
>