[llvm] [llvm-exegesis] [AArch64] Resolving "not all operands are initialized by snippet generator" (PR #142529)

[Lakshay Kumar via llvm-commits]

lakshayk-nv wrote:

Resolving: targets with target-specific operands should implement this
Low hanging, Omission `OPERAND_FIRST_TARGET` with Immediate of value 0.
[Effect]
Support added for ASIMD `UMOV`, `SMOV` `INDEX_RR_H`, and few Load instructions.
```
INDEX_RR_H,
UMOVvi8_idx0,UMOVvi16_idx0,UMOVvi32_idx0,UMOVvi64_idx0,
SMOVvi8to64_idx0,SMOVvi8to32_idx0,SMOVvi32to64_idx0,SMOVvi16to64_idx0,SMOVvi16to32_idx0
```
Support added and expectedly segfault appears
`LD2W,LD1Onev16b,LD2Twov16b,LD4Fourv4h,LDPSi,LD2Rv4s,LD4Rv2s`

https://github.com/llvm/llvm-project/pull/142529