Re: [Qemu-devel] [PATCH v5 07/35] target/arm: Implement SVE FP Multiply-Add Group

[Peter Maydell]

On 26 June 2018 at 15:08, Richard Henderson
<address@hidden> wrote:
> On 06/25/2018 08:32 AM, Peter Maydell wrote:
>>> +# SVE floating-point multiply-accumulate writing addend
>>> +FMLA_zpzzz      01100101 .. 1 ..... 000 ... ..... .....         
>>> @rda_pg_rn_rm
>>> +FMLS_zpzzz      01100101 .. 1 ..... 001 ... ..... .....         
>>> @rda_pg_rn_rm
>>> +FNMLA_zpzzz     01100101 .. 1 ..... 010 ... ..... .....         
>>> @rda_pg_rn_rm
>>> +FNMLS_zpzzz     01100101 .. 1 ..... 011 ... ..... .....         
>>> @rda_pg_rn_rm
>>> +
>>> +# SVE floating-point multiply-accumulate writing multiplicand
>>> +# FMAD, FMSB, FNMAD, FNMS
>>> +FMLA_zpzzz      01100101 .. 1 ..... 100 ... ..... .....         
>>> @rdn_pg_rm_ra
>>> +FMLS_zpzzz      01100101 .. 1 ..... 101 ... ..... .....         
>>> @rdn_pg_rm_ra
>>> +FNMLA_zpzzz     01100101 .. 1 ..... 110 ... ..... .....         
>>> @rdn_pg_rm_ra
>>> +FNMLS_zpzzz     01100101 .. 1 ..... 111 ... ..... .....         
>>> @rdn_pg_rm_ra
>> It's not clear to me how we can implement both of these groups
>> with the same functions. Some commentary might help.
>
> Note the different decode: @rda_pg_rn_rm vs @rdn_pg_rm_ra.
> The same sets of arguments are filled in from different fields
> in the instruction.

Yeah, I figured that was the basic idea, but it was too confusing
to actually work out if that was being done correctly from the
patch.

thanks
-- PMM