[llvm] [RISCV][MC] Improve FPR Error Messages (PR #212492)

[via llvm-commits]

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@@ -38,13 +38,15 @@ def GPRPairAsFPR : AsmOperandClass {
   let ParserMethod = "parseGPRPairAsFPR64";
   let PredicateMethod = "isGPRPairAsFPR64";
   let RenderMethod = "addRegOperands";
+  let DiagnosticString = "register must be an even-numbered GPR when used as FPR";
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saloni-shinde-Q wrote:

Sure, I'll update it to 'as an FP operand'

https://github.com/llvm/llvm-project/pull/212492