[llvm] [RISCV][MC] Improve GPR Error Messages (PR #209669)

[Luke Lau via llvm-commits]

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@@ -391,7 +397,10 @@ def SP : GPRRegisterClass<(add X2)> {
 
 // Saved Registers from s0 to s7, for C.MVA01S07 instruction in Zcmp extension
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lukel97 wrote:

Drive by nit, is this an old mnemonic name? Should this be `cm.mvsa01`

https://github.com/llvm/llvm-project/pull/209669