Revert "Revert "Build new IR for functions returning a constant.""

sdk/lib/_internal/compiler/implementation/js_backend/backend.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.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 145 matching lines @@
       canBeInlinedInsideLoop[element] = false;
     } else {
       canBeInlined[element] = false;
     }
   }
 }
 
 
 class JavaScriptBackend extends Backend {
   SsaBuilderTask builder;
+  SsaFromIrBuilderTask fromIrBuilder;
   SsaOptimizerTask optimizer;
   SsaCodeGeneratorTask generator;
   CodeEmitterTask emitter;
 
   /**
    * The generated code as a js AST for compiled methods.
    */
   Map<Element, jsAst.Expression> get generatedCode {
     return compiler.enqueuer.codegen.generatedCode;
   }
@@ skipping 236 matching lines @@
 
   JavaScriptBackend(Compiler compiler, bool generateSourceMap)
       : namer = determineNamer(compiler),
         oneShotInterceptors = new Map<String, Selector>(),
         interceptedElements = new Map<String, Set<Element>>(),
         rti = new RuntimeTypes(compiler),
         specializedGetInterceptors = new Map<String, Set<ClassElement>>(),
         super(compiler, JAVA_SCRIPT_CONSTANT_SYSTEM) {
     emitter = new CodeEmitterTask(compiler, namer, generateSourceMap);
     builder = new SsaBuilderTask(this);
+    fromIrBuilder = new SsaFromIrBuilderTask(compiler);
     optimizer = new SsaOptimizerTask(this);
     generator = new SsaCodeGeneratorTask(this);
     typeVariableHandler = new TypeVariableHandler(this);
     customElementsAnalysis = new CustomElementsAnalysis(this);
   }
 
   static Namer determineNamer(Compiler compiler) {
     return compiler.enableMinification ?
         new MinifyNamer(compiler) :
         new Namer(compiler);
@@ skipping 821 matching lines @@
         // the checked setter.
         if (Elements.isStaticOrTopLevel(element)) return;
       } else {
         // If the constant-handler was not able to produce a result we have to
         // go through the builder (below) to generate the lazy initializer for
         // the static variable.
         // We also need to register the use of the cyclic-error helper.
         compiler.enqueuer.codegen.registerStaticUse(getCyclicThrowHelper());
       }
     }
-
-    HGraph graph = builder.build(work);
+    HGraph graph = compiler.irBuilder.hasIr(element)
+        ? fromIrBuilder.build(work)
+        : builder.build(work);
     optimizer.optimize(work, graph);
     jsAst.Expression code = generator.generateCode(work, graph);
     generatedCode[element] = code;
   }
 
   native.NativeEnqueuer nativeResolutionEnqueuer(Enqueuer world) {
     return new native.NativeResolutionEnqueuer(world, compiler);
   }
 
   native.NativeEnqueuer nativeCodegenEnqueuer(Enqueuer world) {
@@ skipping 704 matching lines @@
     copy(constant.values);
     copy(constant.protoValue);
     copy(constant);
   }
 
   void visitConstructed(ConstructedConstant constant) {
     copy(constant.fields);
     copy(constant);
   }
 }