[AMDGPU] Avoid or clean unused IMPLICIT_DEF generated from SIFixSGPRCopies pass with REG_SEQUENCE instructions #144518
Description
An example can be found in llvm/test/CodeGen/AMDGPU/legalize-amdgcn.raw.ptr.buffer.store.format.f32.ll:
....
[[DEF:%[0-9]+]]:sgpr_32 = IMPLICIT_DEF
[[DEF1:%[0-9]+]]:sgpr_32 = IMPLICIT_DEF
[[REG_SEQUENCE:%[0-9]+]]:vreg_64 = REG_SEQUENCE [[COPY4]], %subreg.sub0, [[COPY3]], %subreg.sub1
....
Where the implicit_defs remain unused
Seems to be caused by some juggling of sgpr/vgpr with reg_sequence in SIFixSGPRCopies.
sgpr = reg_sequence vgpr, ...., vgpr, ....
to
sgpr = copy vgpr
sgpr = copy vgpr
sgpr = reg_sequence sgpr, ...., sgpr, ....
to
sgpr = implicit_def
sgpr = implicit_def
vgpr= reg_sequence vgpr, ...., vgpr, ....
<uses changes to vgpr>
I assume it's a non-issue, but I'd like to see it not emit implicit_def. Not sure if it's best to avoid the implicit_def altogether or have a clean up stage.