[llvm] [TableGen][GISel] Learn to import patterns with physreg defs (PR #120343)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> What was the pre-select MIR?

Before regbank-select:
```
  %52:_(s32) = G_AMDGPU_INTRIN_IMAGE_LOAD intrinsic(@llvm.amdgcn.image.sample.lz.2d), 1, %71:_(<2 x s16>), $noreg, %37:_(<8 x s32>), %192:_(<4 x s32>), 0, 0, 0, 1 :: (dereferenceable load (s32), addrspace 8)
  %53:_(s32) = G_FCONSTANT float 1.000000e+00
  %54:_(s1) = G_FCMP floatpred(oeq), %52:_(s32), %53:_
```

Before instruction-select:
```
  %52:vgpr(s32) = G_AMDGPU_INTRIN_IMAGE_LOAD intrinsic(@llvm.amdgcn.image.sample.lz.2d), 1, %213:vgpr(<2 x s16>), $noreg, %37:sgpr(<8 x s32>), %192:sgpr(<4 x s32>), 0, 0, 0, 1 :: (dereferenceabl
e load (s32), addrspace 8)
  %53:sgpr(s32) = G_FCONSTANT float 1.000000e+00
  %214:vgpr(s32) = COPY %53:sgpr(s32)
  %54:vcc(s1) = G_FCMP floatpred(oeq), %52:vgpr(s32), %214:vgpr
```


https://github.com/llvm/llvm-project/pull/120343