[llvm] [AArch64][GlobalISel] Lower scalarizing G_UNMERGE_VALUES to G_EXTRACT_VECTOR_ELT (PR #75662)

[Thorsten Schütt via llvm-commits]

================
@@ -769,6 +769,28 @@ void applyDupLane(MachineInstr &MI, MachineRegisterInfo &MRI,
   MI.eraseFromParent();
 }
 
+bool matchScalarizeVectorUnmerge(MachineInstr &MI, MachineRegisterInfo &MRI) {
+  assert(MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES);
----------------
tschuett wrote:

```
GUnmerge *Unmerge = cast<GUnmerge>(&MI);
```

https://github.com/llvm/llvm-project/pull/75662