commit e661c9ef547a8526993947f4a4d4d9ce01b7f115
author Stephen Adams <sra@google.com> Mon Jun 25 23:22:23 2018 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> Mon Jun 25 23:22:23 2018 +0000
tree c371cd5800047a8e4b2c6b9b350c9857b50bc6a8
parent 65a3c4443b84561f1f3b4a4078da1b9589d46e2b

Simplify 'as T' for simple T

Example change:

      return H.subtypeOfRuntimeTypeCast(this.$index(0, "name"), P.String);
--->
      return H.stringTypeCast(this.$index(0, "name"));

Change-Id: I65752a3e9516c5d391cff4e7a0c4b74c877c81af
Reviewed-on: https://dart-review.googlesource.com/60827
Commit-Queue: Stephen Adams <sra@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>

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

diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index f684d58..a0ac620 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -927,7 +927,24 @@
   }
 
   HInstruction visitTypeConversion(HTypeConversion node) {
-    return node.isRedundant(_closedWorld) ? node.checkedInput : node;
+    if (node.isRedundant(_closedWorld)) return node.checkedInput;
+
+    // Simplify 'as T' where T is a simple type.
+    DartType checkedType = node.typeExpression;
+    if (checkedType is TypeVariableType && node.inputs.length == 2) {
+      HInstruction rep = node.typeRepresentation;
+      if (rep is HTypeInfoExpression &&
+          rep.kind == TypeInfoExpressionKind.COMPLETE &&
+          rep.inputs.isEmpty) {
+        DartType type = rep.dartType;
+        if (type.isInterfaceType && type.treatAsRaw) {
+          return node.checkedInput.convertType(_closedWorld, type, node.kind)
+            ..sourceInformation = node.sourceInformation;
+        }
+      }
+    }
+
+    return node;
   }
 
   HInstruction visitTypeKnown(HTypeKnown node) {