Use predicates to check simple function types.

sdk/lib/_internal/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.
 
 part of ssa;
 
 /**
  * A special element for the extra parameter taken by intercepted
  * methods. We need to override [Element.computeType] because our
  * optimizers may look at its declared type.
@@ skipping 1758 matching lines @@
      HInstruction representations = buildTypeArgumentRepresentations(type);
      add(representations);
      return new HTypeConversion.withTypeRepresentation(type, kind, subtype,
           original, representations);
     } else if (type.kind == TypeKind.TYPE_VARIABLE) {
       HType subtype = original.instructionType;
       HInstruction typeVariable = addTypeVariableReference(type);
       return new HTypeConversion.withTypeRepresentation(type, kind, subtype,
           original, typeVariable);
     } else if (type.kind == TypeKind.FUNCTION) {
+      FunctionType functionType = type;
+      if (functionType.isSimple) {
+        return original.convertType(compiler, type, kind);
+      }
       HType subtype = original.instructionType;
       if (type.containsTypeVariables) {
         bool contextIsTypeArguments = false;
         HInstruction context;
         if (currentElement.isInstanceMember()) {
           context = localsHandler.readThis();
         } else {
           ClassElement contextClass = Types.getClassContext(type);
           context = buildTypeVariableList(contextClass);
           add(context);
@@ skipping 998 matching lines @@
         !link.isEmpty;
         link = link.tail) {
       inputs.add(addTypeVariableReference(link.head));
     }
     return buildLiteralList(inputs);
   }
 
   HInstruction buildIsNode(Node node, DartType type, HInstruction expression) {
     type = type.unalias(compiler);
     if (type.kind == TypeKind.FUNCTION) {
+      FunctionType functionType = type;
+      if (functionType.isSimple) {
+        return new HIs(type, <HInstruction>[expression], HIs.RAW_CHECK);
+      }
       Element checkFunctionSubtype = backend.getCheckFunctionSubtype();
 
       HInstruction signatureName = graph.addConstantString(
           new DartString.literal(backend.namer.getFunctionTypeName(type)),
           node, compiler);
 
       HInstruction contextName;
       HInstruction context;
       HInstruction typeArguments;
       if (type.containsTypeVariables) {
@@ skipping 2656 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }