[llvm] [SVE] Don't require lookup when demangling vector function mappings (PR #72260)

[Paul Walker via llvm-commits]

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@@ -66,24 +66,26 @@ ParseRet tryParseMask(StringRef &MangledName, bool &IsMasked) {
 /// vector length. On success, the `<vlen>` token is removed from
 /// the input string `ParseString`.
 ///
-ParseRet tryParseVLEN(StringRef &ParseString, unsigned &VF, bool &IsScalable) {
+ParseRet tryParseVLEN(StringRef &ParseString,
+                      std::optional<unsigned> &ParsedVF) {
   if (ParseString.consume_front("x")) {
-    // Set VF to 0, to be later adjusted to a value grater than zero
-    // by looking at the signature of the vector function with
-    // `getECFromSignature`.
-    VF = 0;
-    IsScalable = true;
+    // We can't determine the VF of a scalable vector by looking at the vlen
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paulwalker-arm wrote:

The encoding is ISA specific and currently only supported when the SVE ISA is specified and thus everything else should result in a parse failure?

https://github.com/llvm/llvm-project/pull/72260