[PATCH] RISC-V: Add implication for M extension.

[Palmer Dabbelt]

On Wed, 09 Oct 2024 09:55:02 PDT (-0700), jeffreyalaw@gmail.com wrote:
>
>
> On 10/9/24 10:52 AM, Palmer Dabbelt wrote:
>> On Tue, 08 Oct 2024 16:43:13 PDT (-0700), jeffreyalaw@gmail.com wrote:
>>>
>>>
>>> On 10/7/24 11:33 PM, Tsung Chun Lin wrote:
>>>> That M implies Zmmul.
>>>>
>>>> gcc/ChangeLog:
>>>>
>>>>          * common/config/riscv/riscv-common.cc: M implies Zmmul.
>>> THanks.  I've pushed this to the trunk.
>>>
>>> jeff
>>>
>>> ps.  Quite a discussion on this topic in the zmmul public discussion
>>> from a couple years ago.  But it looks like the consensus was that M
>>> should imply Zmmul.
>>
>> Wacky timing: I just sat down to try and reply to the "how do C and Zca
>> relate" thread in binutils, only to find this one instead.  I think
>> we've now got the same issue that Jan is pointing out in binutils:
>> basically +M and -M aren't inverses any more (it would leave on Zmmul).
>> Not 100% sure there.
>>
>> FWIW that M/Zmmul thread basically made me give up so I don't really
>> care that much either way, IMO anyone depending on these fine-grained
>> extension things is in for a pile of brokenness.  So as long as we
>> document what we do it's fine with me.
> Yea, when I read it my thought was this was a waste of time, but that I
> didn't care enough to fight it.
>
> Unfortunately it looks like the patches didn't actually get tested and
> is causing a few hundred regressions.  Once I confirm I'll officially
> revert and ask Tsung Chun to post an update after fixing the testing
> failures.

OK, works for me ;)

>
> Jeff