Set up a stub pipline for using the new cps-based ir to generate js.

pkg/compiler/lib/src/js_backend/backend.dart

Index: pkg/compiler/lib/src/js_backend/backend.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index 0f01f9c86572926652e2c1bf78a4637cc4c23fd5..e5317f6602764b981c8f9d01bc5594b9c3bb2b26 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -97,7 +97,8 @@ class JavaScriptBackend extends Backend {
     return [closureClass, jsIndexableClass];
   }
 
-  SsaBuilderTask builder;
+  SsaBuilderTask ssaBuilder;
+  CodeGenTask cpsBuilder;
   SsaOptimizerTask optimizer;
   SsaCodeGeneratorTask generator;
   CodeEmitterTask emitter;
@@ -330,7 +331,7 @@ class JavaScriptBackend extends Backend {
       new Setlet<FunctionElement>();
 
   List<CompilerTask> get tasks {
-    return <CompilerTask>[builder, optimizer, generator, emitter];
+    return <CompilerTask>[ssaBuilder, optimizer, generator, emitter];
   }
 
   final RuntimeTypes rti;
@@ -445,9 +446,12 @@ class JavaScriptBackend extends Backend {
         specializedGetInterceptors = new Map<String, Set<ClassElement>>(),
         super(compiler) {
     emitter = new CodeEmitterTask(compiler, namer, generateSourceMap);
-    builder = new SsaBuilderTask(this);
+    ssaBuilder = new SsaBuilderTask(this);
     optimizer = new SsaOptimizerTask(this);
     generator = new SsaCodeGeneratorTask(this);
+    cpsBuilder = Compiler.USE_CPS_IR
+        ? new CodeGenTask(compiler)

[floitsch, 2014/11/12 11:03:20]

I prefer "Codegen", but I can see why the "G" should be capitalized.

[sigurdm, 2014/11/13 08:29:42]

It is renamed to CodeGenerator in the next CL.

+        : null;
     typeVariableHandler = new TypeVariableHandler(this);
     customElementsAnalysis = new CustomElementsAnalysis(this);
     constantCompilerTask = new JavaScriptConstantTask(compiler);
@@ -1203,9 +1207,20 @@ class JavaScriptBackend extends Backend {
         compiler.enqueuer.codegen.registerStaticUse(getCyclicThrowHelper());
       }
     }
-    HGraph graph = builder.build(work);
-    optimizer.optimize(work, graph);
-    jsAst.Expression code = generator.generateCode(work, graph);
+    jsAst.Expression code;

[floitsch, 2014/11/12 11:03:20]

Alternatively we could:
- have one "CodegenTask" in this class.
- Make that one either a SsaCodegenTask or a CpsCodegenTask.
- let the SsaCodegenTask do the optimizer.optimize + get generator.generateCode.
- let the CpsCodegenTask fall back to the SsaCodegen if it can't handle the
code. That is, it would always return valid code and the backend wouldn't need
to know that the CpsCodegen isn't complete yet. (The code here, would then live
in the CpsCodegenTask).

[sigurdm, 2014/11/13 08:29:41]

Done.

+    if (Compiler.USE_CPS_IR) {
+      if(!work.element.isGenerativeConstructorBody &&
+        work.element.enclosingClass is! ClosureClassElement) {
+        // First try to compile with the new backend.
+        // Will return null if it failed to compile.
+        code = cpsBuilder.build(work);
+      }
+    }
+    if (code == null) {
+      HGraph graph = ssaBuilder.build(work);
+      optimizer.optimize(work, graph);
+      code = generator.generateCode(work, graph);
+    }
     generatedCode[element] = code;
   }