[llvm] [RISCV][AsmParser] Allow parsing vsetvl omitting LMUL parameter (PR #115277)

[Pengcheng Wang via llvm-commits]

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@@ -2320,7 +2326,7 @@ bool RISCVAsmParser::generateVTypeError(SMLoc ErrorLoc) {
   return Error(
       ErrorLoc,
       "operand must be "
-      "e[8|16|32|64],m[1|2|4|8|f2|f4|f8],[ta|tu],[ma|mu]");
+      "e{8|16|32|64},[m{1|2|4|8|f2|f4|f8},]{ta|tu},{ma|mu}");
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wangpc-pp wrote:

Why change `[` to `{`? Mask/tail policies are optional I think. But the original format is not right, it should be `e{8|16|32|64}[,m{1|2|4|8|f2|f4|f8}][,{ta|tu}][,{ma|mu}]` now?

https://github.com/llvm/llvm-project/pull/115277