fixup! Add a little more comment

Author: mshockwave

llvm/include/llvm/Target/TargetSchedule.td

@@ -377,6 +377,7 @@ class MCSchedPredicate<MCInstPredicate P> : SchedPredicateBase {
   SchedMachineModel SchedModel = ?;
 }
 
+// A scheduling predicate whose logic depends on a SubtargetFeature.
 class FeatureSchedPredicate<SubtargetFeature SF> : SchedPredicateBase {
   SubtargetFeature Feature = SF;
   SchedMachineModel SchedModel = ?;

llvm/utils/TableGen/SubtargetEmitter.cpp

@@ -1589,8 +1589,14 @@ static void emitPredicates(const CodeGenSchedTransition &T,
       if (Rec->isSubClassOf("FeatureSchedPredicate")) {
         const Record *FR = Rec->getValueAsDef("Feature");
         if (PE.shouldExpandForMC())
+          // MC version of this predicate will be emitted into
+          // resolveVariantSchedClassImpl, which accesses MCSubtargetInfo
+          // through argument STI.
           SS << "STI.";
         else
+          // Otherwise, this predicate will be emitted directly into
+          // TargetGenSubtargetInfo::resolveSchedClass, which can just access
+          // TargetSubtargetInfo / MCSubtargetInfo through `this`.
           SS << "this->";
         SS << "hasFeature(" << PE.getTargetName() << "::" << FR->getName()
            << ")";