Implement "one-shot" interceptors.

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart	(revision 17466)
+++ sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart	(working copy)
@@ -2095,6 +2095,50 @@
     }
   }
 
+  void emitOneShotInterceptors(CodeBuffer buffer) {

[kasperl, 2013/01/24 07:19:14]

How difficult would it be to build these one shot interceptors in SSA form
instead? The reason I ask is that it would be nice for us to get to a point
where we could unfold the call to getInterceptor like this:

  function foo$oneshot(receiver, x) {
    if (typeof receiver == "number")
      return $.JSNumber.prototype.foo(receiver, x);
    else 
      return $.ObjectInterceptor.prototype.foo(receiver, x);
  }

and then let the builder decide if it wants to inline the calls to two different
calls to foo (based on the code size implications, etc.). 

[ngeoffray, 2013/01/24 08:39:15]

As discussed, I agree it will be pretty neat to rely on the SSA to do further
optimizations. I'll leave that to another CL. Filed
https://code.google.com/p/dart/issues/detail?id=8089 to not forget about it.

+    JavaScriptBackend backend = compiler.backend;
+    for (Selector selector in backend.oneShotInterceptors) {

[sra1, 2013/01/23 21:21:30]

These need to be sorted to have stable output.

It would be useful to have a canonical sort order for selectors.  If you think
this is a separate CL, add an issue to the tracker to implement and use the
order here and make Issue 2388 blocking on it.

[ngeoffray, 2013/01/24 08:39:15]

Issue filed: https://code.google.com/p/dart/issues/detail?id=8088.

+      Set<ClassElement> classes = backend.getInterceptedClassesOn(selector);
+      String oneShotInterceptorName = namer.oneShotInterceptorName(selector);
+      String getInterceptorName =
+          namer.getInterceptorName(backend.getInterceptorMethod, classes);
+
+      List<js.Parameter> parameters = <js.Parameter>[];
+      List<js.Expression> arguments = <js.Expression>[];
+      parameters.add(new js.Parameter('receiver'));
+      arguments.add(new js.VariableUse('receiver'));

[sra1, 2013/01/23 21:21:30]

also: js.use('receiver')

[ngeoffray, 2013/01/24 08:39:15]

Done.

+
+      if (selector.isSetter()) {
+        parameters.add(new js.Parameter('value'));
+        arguments.add(new js.VariableUse('value'));
+      } else {
+        for (int i = 0; i < selector.argumentCount; i++) {
+          String argName = 'a$i';
+          parameters.add(new js.Parameter(argName));
+          arguments.add(new js.VariableUse(argName));
+        }
+      }
+
+      String invocationName = backend.namer.invocationName(selector);
+      js.Fun function =
+          new js.Fun(parameters,
+              new js.Block(
+                  <js.Statement>[
+                      new js.Return(

[sra1, 2013/01/23 21:21:30]

also: js.return_(x)

[ngeoffray, 2013/01/24 08:39:15]

Done.

+                          js.use(isolateProperties)
+                              .dot(getInterceptorName)
+                              .callWith([js.use('receiver')])
+                                  .dot(invocationName)
+                                  .callWith(arguments))]));
+
+      js.PropertyAccess property =
+          js.fieldAccess(js.use(isolateProperties), oneShotInterceptorName);
+
+      buffer.add(js.prettyPrint(js.assign(property, function), compiler));
+      buffer.add(N);
+    }
+  }
+
   String assembleProgram() {
     measure(() {
       computeNeededClasses();
@@ -2124,6 +2168,7 @@
       // Static field initializations require the classes and compile-time
       // constants to be set up.
       emitStaticNonFinalFieldInitializations(mainBuffer);
+      emitOneShotInterceptors(mainBuffer);
       emitGetInterceptorMethods(mainBuffer);
       emitLazilyInitializedStaticFields(mainBuffer);