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

[Erich Keane via cfe-commits]

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@@ -1363,19 +1363,28 @@ static llvm::X86::ProcessorFeatures getFeature(StringRef Name) {
   // correct, so it asserts if the value is out of range.
 }
 
-unsigned X86TargetInfo::multiVersionSortPriority(StringRef Name) const {
-  // Valid CPUs have a 'key feature' that compares just better than its key
-  // feature.
-  using namespace llvm::X86;
-  CPUKind Kind = parseArchX86(Name);
-  if (Kind != CK_None) {
-    ProcessorFeatures KeyFeature = getKeyFeature(Kind);
-    return (getFeaturePriority(KeyFeature) << 1) + 1;
-  }
-
-  // Now we know we have a feature, so get its priority and shift it a few so
-  // that we have sufficient room for the CPUs (above).
-  return getFeaturePriority(getFeature(Name)) << 1;
+unsigned X86TargetInfo::getFMVPriority(ArrayRef<StringRef> Features) const {
+  auto getPriority = [this](StringRef Feature) -> unsigned {
+    if (Feature.empty())
+      return 0;
+
+    // Valid CPUs have a 'key feature' that compares just better than its key
+    // feature.
+    using namespace llvm::X86;
+    CPUKind Kind = parseArchX86(Feature);
+    if (Kind != CK_None) {
+      ProcessorFeatures KeyFeature = getKeyFeature(Kind);
+      return (getFeaturePriority(KeyFeature) << 1) + 1;
+    }
+    // Now we know we have a feature, so get its priority and shift it a few so
+    // that we have sufficient room for the CPUs (above).
+    return getFeaturePriority(getFeature(Feature)) << 1;
+  };
+
+  unsigned Priority = 0;
+  for (StringRef Feature : Features)
+    Priority = std::max(Priority, getPriority(Feature));
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erichkeane wrote:

I don't think 'max' does the right thing here, does it?  The whole point was to put together a mask representation that matches the `cpuid` call (Best we could!) that is the collection of all the features.  That way you could have a list of features and have them be differentiated (that is, some of the FMV supports just a list of features, and we want to be able to differentiate between `high-feature, low-feature` and `high-feature, lower-feature`.

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