RFC: Start refactoring to provide more than a single backend.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index 781c4847ce9dfdee073b640a8811f8c3db025b24..e6bb94055b32d835b4b9879d8b4677b9c9e18a97 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -30,6 +30,36 @@ class WorkItem {
   }
 }
 
+interface Backend {

[ahe, 2012/05/11 11:39:48]

This looks reasonable, but I would prefer to have a common base class instead of
an interface. In dart2js, we tend to make much fewer interfaces than is common
in Java.

One of the reasons is that we have implicit interfaces from classes.

Also, there is a bit of an allergic reaction based on our experience in dartc.

[floitsch, 2012/05/11 13:51:04]

Personally I prefer an interface over an empty class. If there is something to
share, I would of course prefer a class.

[Anton Muhin, 2012/05/12 15:48:43]

I erred to interface for as of now I'd rather move any common code into compiler
than backend.

Again, you all should know this stuff better so I'd introduce a base class if
you think it's better approach.

On 2012/05/11 13:51:04, floitsch wrote:

+  String codegen(WorkItem work);
+}
+
+class JsBackend implements Backend {

[ahe, 2012/05/11 11:39:48]

Personally, I prefer JavaScriptBackend instead of the abbreviation.

[Anton Muhin, 2012/05/12 15:48:43]

Done.

+  Compiler compiler;
+  SsaBuilderTask builder;
+  SsaOptimizerTask optimizer;
+  SsaCodeGeneratorTask generator;
+
+  JsBackend(Compiler compiler)
+      : this.compiler = compiler,
+        builder = new SsaBuilderTask(compiler),
+        optimizer = new SsaOptimizerTask(compiler),
+        generator = new SsaCodeGeneratorTask(compiler);
+
+  String codegen(WorkItem work) {
+    HGraph graph = builder.build(work);
+    optimizer.optimize(work, graph);
+    if (work.allowSpeculativeOptimization
+        && optimizer.trySpeculativeOptimizations(work, graph)) {
+      String code = generator.generateBailoutMethod(work, graph);
+      compiler.universe.addBailoutCode(work, code);
+      optimizer.prepareForSpeculativeOptimizations(work, graph);
+      optimizer.optimize(work, graph);
+    }
+    return generator.generateMethod(work, graph);
+  }
+}
+
 class Compiler implements DiagnosticListener {
   Queue<WorkItem> worklist;
   Universe universe;
@@ -80,9 +110,7 @@ class Compiler implements DiagnosticListener {
   TreeValidatorTask validator;
   ResolverTask resolver;
   TypeCheckerTask checker;
-  SsaBuilderTask builder;
-  SsaOptimizerTask optimizer;
-  SsaCodeGeneratorTask generator;
+  Backend backend;
   CodeEmitterTask emitter;
   ConstantHandler constantHandler;
   EnqueueTask enqueuer;
@@ -112,13 +140,10 @@ class Compiler implements DiagnosticListener {
     validator = new TreeValidatorTask(this);
     resolver = new ResolverTask(this);
     checker = new TypeCheckerTask(this);
-    builder = new SsaBuilderTask(this);
-    optimizer = new SsaOptimizerTask(this);
-    generator = new SsaCodeGeneratorTask(this);
+    backend = new JsBackend(this);
     emitter = new CodeEmitterTask(this);
     enqueuer = new EnqueueTask(this);
     tasks = [scanner, dietParser, parser, resolver, checker,
-             builder, optimizer, generator,
              emitter, constantHandler, enqueuer];
   }
 
@@ -345,22 +370,9 @@ class Compiler implements DiagnosticListener {
       constantHandler.compileWorkItem(work);
       return null;
     } else {
-      HGraph graph = builder.build(work);
-      optimizer.optimize(work, graph);
-      if (work.allowSpeculativeOptimization
-          && optimizer.trySpeculativeOptimizations(work, graph)) {
-        String code = generator.generateBailoutMethod(work, graph);
-        universe.addBailoutCode(work, code);
-        optimizer.prepareForSpeculativeOptimizations(work, graph);
-        optimizer.optimize(work, graph);
-        code = generator.generateMethod(work, graph);
-        universe.addGeneratedCode(work, code);
-        return code;
-      } else {
-        String code = generator.generateMethod(work, graph);
-        universe.addGeneratedCode(work, code);
-        return code;
-      }
+      String code = backend.codegen(work);
+      universe.addGeneratedCode(work, code);
+      return code;
     }
   }