[llvm] [RISCV] Use decodeUImmLog2XLenNonZeroOperand in decodeRVCInstrRdRs1UImm. NFC (PR #133759)

[Sam Elliott via llvm-commits]

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@@ -661,7 +661,7 @@ def C_SLLI_HINT : RVInst16CI<0b000, 0b10, (outs GPRX0:$rd_wb),
                   Sched<[WriteShiftImm, ReadShiftImm]> {
   let Constraints = "$rd = $rd_wb";
   let Inst{11-7} = 0;
-  let DecoderMethod = "decodeRVCInstrRdRs1UImm";
+  let DecoderMethod = "decodeRVCInstrRdRs1UImmLog2XLenNonZero";
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lenary wrote:

I think there are two things going on here:
- `c.slli` is a hint when rd=0 (which I think this patch is refactoring, maybe?)
- `c.slli` is a hint when shamt=0

For the latter case, do we have a different Inst defintion?

If not, then isn't this wrong, because we should allow `shamt=0` when decoding this instruction, which I think is now prevented? I'm not entirely sure, honestly.

https://github.com/llvm/llvm-project/pull/133759