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dart2js cps: Improve rewriting of == to identical.

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We now rewrite `x == y` if x is known to have a == implementation that
corresponds to identical(). Previously it would only do this when x was
num, string, or bool.

BUG=
R=karlklose@google.com

Review URL: https://codereview.chromium.org//1286993003.
This commit is contained in:
Asger Feldthaus 2015-08-12 13:13:47 +02:00
parent 930bc75c0d
commit 703e968620
1 changed files with 22 additions and 2 deletions
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24
pkg/compiler/lib/src/cps_ir/type_propagation.dart
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@ -852,6 +852,11 @@ class TransformingVisitor extends LeafVisitor {
}
}
/// Returns the possible targets of [selector] when invoked on a receiver
/// of type [receiverType].
Iterable<Element> getAllTargets(TypeMask receiverType, Selector selector) {
return compiler.world.allFunctions.filter(selector, receiverType);
}
/************************* CALL EXPRESSIONS *************************/
@ -885,8 +890,23 @@ class TransformingVisitor extends LeafVisitor {
// Equality is special due to its treatment of null values and the
// fact that Dart-null corresponds to both JS-null and JS-undefined.
// Please see documentation for IsFalsy, StrictEq, and LooseEq.
if (lattice.isDefinitelyNumStringBool(left, allowNull: true) ||
right.isNullConstant) {
if (left.isNullConstant || right.isNullConstant) {
return replaceWithBinary(BuiltinOperator.Identical,
leftArg, rightArg);
}
// There are several implementations of == that behave like identical.
// Specialize it if we definitely call one of those.
bool behavesLikeIdentical = true;
for (Element target in getAllTargets(left.type, node.selector)) {
ClassElement clazz = target.enclosingClass.declaration;
if (clazz != compiler.world.objectClass &&
clazz != backend.jsInterceptorClass &&
clazz != backend.jsNullClass) {
behavesLikeIdentical = false;
break;
}
}
if (behavesLikeIdentical) {
return replaceWithBinary(BuiltinOperator.Identical,
leftArg, rightArg);
}