[llvm] [RISCV] Reduce size of CSR lookup tables. NFC (PR #121606)

[Craig Topper via llvm-commits]

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@@ -1915,6 +1915,8 @@ ParseStatus RISCVAsmParser::parseCSRSystemRegister(OperandVector &Operands) {
         // Accept an immediate representing a named Sys Reg if it satisfies the
         // the required features.
         for (auto &Reg : Range) {
+          if (Reg.IsAltName || Reg.IsDeprecatedName)
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topperc wrote:

This isn't strictly needed, but ensures we use the required features from the primary name and not the alternate or deprecated names.

https://github.com/llvm/llvm-project/pull/121606