[llvm] [RISCV][MC] Implement ISA mapping symbols (PR #67541)

[Joe Faulls via llvm-commits]

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@@ -44,14 +44,33 @@ RISCVTargetELFStreamer::RISCVTargetELFStreamer(MCStreamer &S,
   // its ParseInstruction may call setForceRelocs as well.
   if (STI.hasFeature(RISCV::FeatureRelax))
     static_cast<RISCVAsmBackend &>(MAB).setForceRelocs();
+
+  // Using RISCVISAInfo, construct ISAString from given features.
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joe-img wrote:

Thanks - I missed that function.

https://github.com/llvm/llvm-project/pull/67541