[llvm] [RISCV] Add groupid/bitmask for RISC-V extension (PR #94440)

[Craig Topper via llvm-commits]

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@@ -37,6 +37,15 @@ class RISCVExtension<string name, int major, int minor, string desc,
   bit Experimental = false;
 }
 
+// The groupID/bitmask of RISCVExtension is used to retrieve a specific bit value 
+// from __riscv_feature_bit based on the groupID and bitmask.
+// gourpID      - groupID of extension
+// bitmaskShift - bitmask shift of extension
+class RISCVExtensionBitmask<bits<3> groupID, int bitmaskShift> {
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topperc wrote:

Can we merge groupID and bitmask shift into a single value where 0-63 is group 0, 64-127 is group 1, 128-191 is group 3, etc.

https://github.com/llvm/llvm-project/pull/94440