[llvm] [TableGen] Print a warning when a Processor contains duplicate Features / TuneFeatures (PR #137864)

[Rahul Joshi via llvm-commits]

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@@ -333,6 +333,30 @@ unsigned SubtargetEmitter::cpuNames(raw_ostream &OS) {
   return Names.size();
 }
 
+static void checkDuplicateCPUFeatures(StringRef CPUName,
+                                      ArrayRef<const Record *> Features,
+                                      ArrayRef<const Record *> TuneFeatures) {
+  // We had made sure each SubtargetFeature Record has a unique name, so we can
+  // simply use pointer sets here.
+  SmallPtrSet<const Record *, 8> FeatureSet, TuneFeatureSet;
+  for (const auto *FeatureRec : Features) {
+    if (!FeatureSet.insert(FeatureRec).second)
+      PrintWarning("Processor " + CPUName + " contains duplicate feature '" +
+                   FeatureRec->getValueAsString("Name") + "'");
+  }
+
+  for (const auto *TuneFeatureRec : TuneFeatures) {
+    if (!TuneFeatureSet.insert(TuneFeatureRec).second)
+      PrintWarning("Processor " + CPUName +
+                   " contains duplicate tune feature '" +
+                   TuneFeatureRec->getValueAsString("Name") + "'");
+    if (FeatureSet.count(TuneFeatureRec))
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jurahul wrote:

nit: FeatureSer.contains() for a more canonical form?

https://github.com/llvm/llvm-project/pull/137864