[dart2js] Add cache to FlatTypeMask.interesection

Both the calls to ClassHierarchy.commonSubclasses and UnionTypeMask.flatten (in the worse case) are expensive for large programs. Certain programs can have a type structure that ends up in the UnionTypeMask.flatten case very often which can be especially taxing.


Change-Id: I7799d2f5a7f764162a4ca753bfa37b11f583373f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/269221
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Stephen Adams <[email protected]>

Author: natebiggs

pkg/compiler/lib/src/inferrer/typemasks/flat_type_mask.dart

@@ -436,6 +436,11 @@ class FlatTypeMask extends TypeMask {
 
   @override
   TypeMask intersection(TypeMask other, CommonMasks domain) {
+    return (domain._intersectionCache[this] ??= {})[other] ??=
+        _intersection(other, domain);
+  }
+
+  TypeMask _intersection(TypeMask other, CommonMasks domain) {
     if (other is! FlatTypeMask) return other.intersection(this, domain);
     assert(TypeMask.assertIsNormalized(this, domain._closedWorld));
     assert(TypeMask.assertIsNormalized(other, domain._closedWorld));

pkg/compiler/lib/src/inferrer/typemasks/masks.dart

@@ -45,6 +45,8 @@ class CommonMasks with AbstractValueDomain {
   CommonElements get commonElements => _closedWorld.commonElements;
   DartTypes get dartTypes => _closedWorld.dartTypes;
 
+  final Map<TypeMask, Map<TypeMask, TypeMask>> _intersectionCache = {};
+
   /// Cache of [FlatTypeMask]s grouped by the possible values of the
   /// `FlatTypeMask.flags` property.
   final List<Map<ClassEntity, TypeMask>?> _canonicalizedTypeMasks = List.filled(

pkg/compiler/lib/src/inferrer_experimental/typemasks/flat_type_mask.dart

@@ -436,6 +436,11 @@ class FlatTypeMask extends TypeMask {
 
   @override
   TypeMask intersection(TypeMask other, CommonMasks domain) {
+    return (domain._intersectionCache[this] ??= {})[other] ??=
+        _intersection(other, domain);
+  }
+
+  TypeMask _intersection(TypeMask other, CommonMasks domain) {
     if (other is! FlatTypeMask) return other.intersection(this, domain);
     assert(TypeMask.assertIsNormalized(this, domain._closedWorld));
     assert(TypeMask.assertIsNormalized(other, domain._closedWorld));

pkg/compiler/lib/src/inferrer_experimental/typemasks/masks.dart

@@ -45,6 +45,8 @@ class CommonMasks with AbstractValueDomain {
   CommonElements get commonElements => _closedWorld.commonElements;
   DartTypes get dartTypes => _closedWorld.dartTypes;
 
+  final Map<TypeMask, Map<TypeMask, TypeMask>> _intersectionCache = {};
+
   /// Cache of [FlatTypeMask]s grouped by the possible values of the
   /// `FlatTypeMask.flags` property.
   final List<Map<ClassEntity, TypeMask>?> _canonicalizedTypeMasks = List.filled(