[PATCH] x86: Remove AMX-TRANSPOSE support

[Jan Beulich]

On 10.10.2025 08:20, Haochen Jiang wrote:
> In ISE059, AMX-TRANSPOSE is removed. It will never happen to any
> future hardware since x86 Advisory Group is aware of the removal.
> Thus, We decide to remove the support to ease maintainence effort.
> 
> Due to the support being in Binutils 2.44/2.45, we should make sure
> no one use the same encoding in the future or it will conflict
> between versions. I added comments in the patch in case someone
> encounter that.
> 
> Discussions are welcomed for the removal.

I'm generally unconvinced of removing things that were once specified,
and clearly for a reason. AVX10/256 had sensible reasons to exist, and
transposing matrices is something one can't - afaict - easily
synthesize from other insns (say, no more than three). Yet use of
transposed matrices does occur in (mathematical) practice. Hence I find
it somewhat hard to believe that "it will never happen to any future
hardware".

That said, gradually I'm more concerned of the removal from the
disassembler than that from the assembler. (And just to clarify: I
think the compiler is in a different position here. Much like e.g. MPX
and Phi support was removed there, we already made clear that we intend
to keep it in binutils. Of course that's not exactly an apples-to-
apples comparison, because there production hardware exists with the
features available.)

Further, if we decided to retain support, perhaps bafcf0823c1a
("x86/APX: drop AMX-TRANSPOSE promoted insns") would then probably also
want undoing.

Jan