Optimize out checkInt, checkNum and checkString

pkg/compiler/lib/src/ssa/optimize.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.
 
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/names.dart' show Selectors;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
@@ skipping 934 matching lines @@
       if (other != value) {
         node.block.addBefore(node, other);
         value = other;
       }
     }
     return new HFieldSet(field, receiver, value);
   }
 
   HInstruction visitInvokeStatic(HInvokeStatic node) {
     propagateConstantValueToUses(node);
-    if (node.element == backend.helpers.checkConcurrentModificationError) {
+    Element element = node.element;
+
+    if (element == backend.helpers.checkConcurrentModificationError) {
       if (node.inputs.length == 2) {
         HInstruction firstArgument = node.inputs[0];
         if (firstArgument is HConstant) {
           HConstant constant = firstArgument;
           if (constant.constant.isTrue) return constant;
         }
       }
+    } else if (element == backend.helpers.checkInt) {
+      if (node.inputs.length == 1) {
+        HInstruction argument = node.inputs[0];
+        if (argument.isInteger(compiler)) return argument;
+      }
+    } else if (element == backend.helpers.checkNum) {
+      if (node.inputs.length == 1) {
+        HInstruction argument = node.inputs[0];
+        if (argument.isNumber(compiler)) return argument;
+      }
+    } else if (element == backend.helpers.checkString) {
+      if (node.inputs.length == 1) {
+        HInstruction argument = node.inputs[0];
+        if (argument.isString(compiler)) return argument;
+      }
     }
     return node;
   }
 
   HInstruction visitStringConcat(HStringConcat node) {
     // Simplify string concat:
     //
     //     "" + R                ->  R
     //     L + ""                ->  L
     //     "L" + "R"             ->  "LR"
@@ skipping 1704 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }