[llvm] [RISCV] Add XSfmm pseudo instruction and vset* insertion support (PR #143068)

[Kito Cheng via llvm-commits]

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@@ -503,6 +526,8 @@ class VSETVLIInfo {
   uint8_t TailAgnostic : 1;
   uint8_t MaskAgnostic : 1;
   uint8_t SEWLMULRatioOnly : 1;
+  uint8_t AltFmt : 1;
+  uint8_t TWiden = 0;
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kito-cheng wrote:

2 bit should be enough per spec 
```suggestion
  uint8_t TWiden : 2 = 0;
```

https://github.com/llvm/llvm-project/pull/143068