[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 don't understand the algorithm here. This seems like sorts resolvees first by how many conditions they've got, and _then_ by the highest priority of each in that group. But what we actually need is a total order on two sets. Maybe the API should be shaped more like a comparison operator on feature sets, rather than a serialized index constructed from members's priorities?

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