[NVPTX] Make nvptx mma instructions convergent. (#96521)

We are running into NVPTX backend generating wrong code for an input:
```
%0 = llvm.nvvm.mma.m?n?k?.row.col.??? (...)
if laneid == 0:
  ret
else:
  store %0
```

The backend reorder the instruction (as an effect of `MachineSink` pass)
to
```
if laneid == 0:
  ret
else:
  %0 = llvm.nvvm.mma.m?n?k?.row.col.??? (...)
  store %0
```

This is incorrect because `mma` is a warp instruction which needs all
threads to sync before performing the operation instead of being guarded
by a specific thread id. It should be similar as the shuffle instruction
`shfl` in terms of warp level sync, and `shfl` is marked as
`isConvergent = true`.

Apply `isConvergent = true` to `mma` instructions.

0 files changed, 0 insertions, 0 deletions