[Libre-soc-dev] LD/ST Elwidth Overrides

[lkcl]

On September 1, 2021 8:15:08 PM UTC, Jacob Lifshay <programmerjake at gmail.com> wrote:
>On Wed, Sep 1, 2021, 13:09 lkcl <luke.leighton at gmail.com> wrote:
>
>>
>>
>> On September 1, 2021 7:54:05 PM UTC, Jacob Lifshay <
>> programmerjake at gmail.com> wrote:
>>
>> >yup, but that still doesn't cover 23(r5.v)
>>
>> different section, 1st 4 entries.  23(r5.v) is an
>> immediate variant (elstride/unit stride) and that you *do* want
>ffirst,
>> it's the whole point.
>>
>> the sole reason Indexed FFIRST is banned is because it can be used to
>> probe multiple pages extremely rapidly.
>>
>
>strided ffirst can probe pages just about as rapidly...

not really.  Indexed can do multiple pages in a single instruction.

Unit strided can only cross a single page boundary per instruction.

the difference is an order of magnitude in speed.  nearly 2 orders of magnitude if VL=64.

l.