[clang] [llvm] [RISCV][MC] Implement MC for Base P extension (PR #123271)

[Min-Yih Hsu via cfe-commits]

================
@@ -224,6 +224,13 @@ static DecodeStatus DecodeGPRPairRegisterClass(MCInst &Inst, uint32_t RegNo,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus decodeRVPGPRPair(MCInst &Inst, uint32_t RegNo,
+                                     uint64_t Address,
+                                     const MCDisassembler *Decoder) {
+  RegNo = RegNo << 1;
+  return DecodeGPRPairRegisterClass(Inst, RegNo, Address, Decoder);
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mshockwave wrote:

nit:
```suggestion
  return DecodeGPRPairRegisterClass(Inst, RegNo << 1, Address, Decoder);
```

https://github.com/llvm/llvm-project/pull/123271