[dart2js] New RTI: Use precomputed1 to access first type argument of

interface types.

Change-Id: I167bb9be3f07dd3734993a46283a9d6eea56ac92
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/119960
Commit-Queue: Mayank Patke <fishythefish@google.com>
Reviewed-by: Stephen Adams <sra@google.com>

Author: fishythefish

pkg/compiler/lib/src/common_elements.dart

@@ -499,6 +499,7 @@ abstract class CommonElements {
   FieldEntity get rtiCheckField;
   FieldEntity get rtiIsField;
   FieldEntity get rtiRestField;
+  FieldEntity get rtiPrecomputed1Field;
   FunctionEntity get rtiEvalMethod;
   FunctionEntity get rtiBindMethod;
   FunctionEntity get rtiAddRulesMethod;
@@ -1914,6 +1915,11 @@ class CommonElementsImpl
   @override
   FieldEntity get rtiRestField => _rtiRestField ??= _findRtiClassField('_rest');
 
+  FieldEntity _rtiPrecomputed1Field;
+  @override
+  FieldEntity get rtiPrecomputed1Field =>
+      _rtiPrecomputed1Field ??= _findRtiClassField('_precomputed1');
+
   FunctionEntity _rtiEvalMethod;
   @override
   FunctionEntity get rtiEvalMethod =>

pkg/compiler/lib/src/ssa/codegen.dart

@@ -2212,6 +2212,14 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
     }
   }
 
+  js.Expression _loadField(js.Expression receiver, FieldEntity field,
+      SourceInformation sourceInformation) {
+    _registry.registerStaticUse(StaticUse.fieldGet(field));
+    js.Name name = _namer.instanceFieldPropertyName(field);
+    return js.PropertyAccess(receiver, name)
+        .withSourceInformation(sourceInformation);
+  }
+
   @override
   visitFieldGet(HFieldGet node) {
     use(node.receiver);
@@ -2222,11 +2230,7 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
       push(new js.PropertyAccess.field(pop(), 'toString')
           .withSourceInformation(node.sourceInformation));
     } else {
-      FieldEntity field = node.element;
-      js.Name name = _namer.instanceFieldPropertyName(field);
-      push(new js.PropertyAccess(pop(), name)
-          .withSourceInformation(node.sourceInformation));
-      _registry.registerStaticUse(new StaticUse.fieldGet(field));
+      push(_loadField(pop(), node.element, node.sourceInformation));
     }
   }
 
@@ -3492,13 +3496,20 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
             // its length (i.e. into its base), since in that case, we could
             // eval against the base directly.
             assert(index <= bindings.length);
+          } else {
+            // If the environment is an interface RTI, use precomputed fields
+            // for common accesses.
+            if (index == 1) {
+              push(_loadField(environment, _commonElements.rtiPrecomputed1Field,
+                  node.sourceInformation));
+              return;
+            }
           }
-          js.Expression access = js.js('#.#[#]', [
-            environment,
-            _namer.instanceFieldPropertyName(_commonElements.rtiRestField),
-            js.number(index - 1),
-          ]);
-          push(access.withSourceInformation(node.sourceInformation));
+
+          js.Expression rest = _loadField(environment,
+              _commonElements.rtiRestField, node.sourceInformation);
+          push(js.PropertyAccess.indexed(rest, index - 1)
+              .withSourceInformation(node.sourceInformation));
           return;
         }
       }

sdk/lib/_internal/js_runtime/lib/rti.dart

@@ -98,6 +98,11 @@ class Rti {
   dynamic _precomputed3;
   dynamic _precomputed4;
 
+  static Rti _getPrecomputed1(Rti rti) => _castToRti(rti._precomputed1);
+  static void _setPrecomputed1(Rti rti, Rti precomputed) {
+    rti._precomputed1 = precomputed;
+  }
+
   // The Type object corresponding to this Rti.
   Object _cachedRuntimeType;
   static _Type _getCachedRuntimeType(Rti rti) =>
@@ -1495,6 +1500,10 @@ class _Universe {
     Rti._setKind(rti, Rti.kindInterface);
     Rti._setPrimary(rti, name);
     Rti._setRest(rti, typeArguments);
+    int length = _Utils.arrayLength(typeArguments);
+    if (length > 0) {
+      Rti._setPrecomputed1(rti, _castToRti(_Utils.arrayAt(typeArguments, 0)));
+    }
     Rti._setCanonicalRecipe(rti, key);
     return _finishRti(universe, rti);
   }
@@ -2077,6 +2086,7 @@ class _Parser {
     if (kind != Rti.kindInterface) {
       throw AssertionError('Indexed base must be an interface type');
     }
+    if (index == 1) return Rti._getPrecomputed1(environment);
     var typeArguments = Rti._getInterfaceTypeArguments(environment);
     int len = _Utils.arrayLength(typeArguments);
     if (index <= len) {

sdk_nnbd/lib/_internal/js_runtime/lib/rti.dart

@@ -100,6 +100,11 @@ class Rti {
   dynamic _precomputed3;
   dynamic _precomputed4;
 
+  static Rti _getPrecomputed1(Rti rti) => _castToRti(rti._precomputed1);
+  static void _setPrecomputed1(Rti rti, Rti precomputed) {
+    rti._precomputed1 = precomputed;
+  }
+
   // The Type object corresponding to this Rti.
   Object _cachedRuntimeType;
   static _Type _getCachedRuntimeType(Rti rti) =>
@@ -1497,6 +1502,10 @@ class _Universe {
     Rti._setKind(rti, Rti.kindInterface);
     Rti._setPrimary(rti, name);
     Rti._setRest(rti, typeArguments);
+    int length = _Utils.arrayLength(typeArguments);
+    if (length > 0) {
+      Rti._setPrecomputed1(rti, _castToRti(_Utils.arrayAt(typeArguments, 0)));
+    }
     Rti._setCanonicalRecipe(rti, key);
     return _finishRti(universe, rti);
   }
@@ -2079,6 +2088,7 @@ class _Parser {
     if (kind != Rti.kindInterface) {
       throw AssertionError('Indexed base must be an interface type');
     }
+    if (index == 1) return Rti._getPrecomputed1(environment);
     var typeArguments = Rti._getInterfaceTypeArguments(environment);
     int len = _Utils.arrayLength(typeArguments);
     if (index <= len) {