[clang] [llvm] [NFC][clang][FMV][TargetInfo] Refactor API for FMV feature priority. (PR #116257)

[Jon Roelofs via cfe-commits]

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@@ -48,6 +48,19 @@ std::optional<AArch64::ArchInfo> AArch64::ArchInfo::findBySubArch(StringRef SubA
   return {};
 }
 
+unsigned AArch64::getFMVPriority(ArrayRef<StringRef> Features) {
+  constexpr unsigned MaxFMVPriority = 1000;
+  unsigned Priority = 0;
+  unsigned NumFeatures = 0;
+  for (StringRef Feature : Features) {
+    if (auto Ext = parseFMVExtension(Feature)) {
+      Priority = std::max(Priority, Ext->Priority);
+      NumFeatures++;
+    }
+  }
+  return Priority + MaxFMVPriority * NumFeatures;
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jroelofs wrote:

I'm not sure it does that correctly: `simd+dotprod` is weighted higher than `sme` with this algorithm purely because it has more features.

https://github.com/llvm/llvm-project/pull/116257