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

lib/compiler/implementation/ssa/builder.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 763 matching lines @@
   // The most recently opened block. Has the same value as [current] while
   // the block is open, but unlike [current], it isn't cleared when the current
   // block is closed.
   HBasicBlock lastOpenedBlock;
 
   LibraryElement get currentLibrary() => work.element.getLibrary();
 
   SsaBuilder(Compiler compiler, WorkItem work)
     : this.compiler = compiler,
       this.work = work,
-      interceptors = compiler.builder.interceptors,
+      interceptors = compiler.backend.builder.interceptors,
       methodInterceptionEnabled = true,
       elements = work.resolutionTree,
       graph = new HGraph(),
       stack = new List<HInstruction>(),
       jumpTargets = new Map<TargetElement, JumpHandler>() {
     localsHandler = new LocalsHandler(this);
   }
 
   void disableMethodInterception() {
     assert(methodInterceptionEnabled);
@@ skipping 658 matching lines @@
             wrapExpressionGraph(conditionExpression),
             wrapStatementGraph(bodyGraph),
             null,
             loopEntryBlock.loopInformation.target,
             loopEntryBlock.loopInformation.labels);
     loopEntryBlock.setBlockFlow(loopBlockInfo, current);
     loopInfo.loopBlockInformation = loopBlockInfo;
   }
 
   visitFunctionExpression(FunctionExpression node) {
-    ClosureData nestedClosureData = compiler.builder.closureDataCache[node];
+    ClosureData nestedClosureData = compiler.backend.builder.closureDataCache[node];
     if (nestedClosureData === null) {
       // TODO(floitsch): we can only assume that the reason for not having a
       // closure data here is, because the function is inside an initializer.
       compiler.unimplemented("Closures inside initializers", node: node);
     }
     assert(nestedClosureData !== null);
     assert(nestedClosureData.closureClassElement !== null);
     ClassElement closureClassElement =
         nestedClosureData.closureClassElement;
     FunctionElement callElement = nestedClosureData.callElement;
@@ skipping 1841 matching lines @@
                                    <HInstruction>[target, input],
                                    HType.STRING));
     return builder.pop();
   }
 
   HInstruction result() {
     flushLiterals();
     return prefix;
   }
 }