[llvm] [TableGen] Add `!match` operator to do regex matching (PR #130759)

[Matt Arsenault via llvm-commits]

================
@@ -1318,6 +1319,20 @@ const Init *BinOpInit::Fold(const Record *CurRec) const {
     }
     break;
   }
+  case MATCH: {
+    const auto *StrInit = dyn_cast<StringInit>(LHS);
+    const auto *RegexInit = dyn_cast<StringInit>(RHS);
+    if (!(StrInit && RegexInit))
+      return this;
----------------
arsenm wrote:

```suggestion
    const auto *StrInit = dyn_cast<StringInit>(LHS);
    if (!StrInit)
      return this
    const auto *RegexInit = dyn_cast<StringInit>(RHS);
    if (!RegexInit)
      return this;
```

https://github.com/llvm/llvm-project/pull/130759