dart2js cps: Better 'is int' checks.

pkg/compiler/lib/src/cps_ir/builtin_operator.dart

 // Copyright (c) 2015, 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.
 library builtin_operator;
 // This is shared by the CPS and Tree IRs.
 // Both cps_ir_nodes and tree_ir_nodes import and re-export this file.
 
 /// An operator supported natively in the CPS and Tree IRs using the
 /// `ApplyBuiltinOperator` instructions.
 ///
 /// These operators are pure in the sense that they cannot throw, diverge,
 /// have observable side-effects, return new objects, nor depend on any
 /// mutable state.
 ///
 /// Most operators place restrictions on the values that may be given as
 /// argument; their behaviour is unspecified if those requirements are violated.
 ///
 /// In all cases, the word "null" refers to the Dart null object, corresponding
 /// to both JS null and JS undefined.
+///
+/// Some operators, notably [IsFloor] and [IsNumberAndFloor], take "repeated"
+/// arguments to reflect the number of times the given value is referenced
+/// by the generated code. The tree IR needs to know the number of references
+/// to safely propagate assignments.
 enum BuiltinOperator {
   /// The numeric binary operators must take two numbers as argument.
   /// The bitwise operators coerce the result to an unsigned integer, but
   /// otherwise these all behave like the corresponding JS operator.
   NumAdd,
   NumSubtract,
   NumMultiply,
   NumAnd,
   NumOr,
   NumXor,
@@ skipping 18 matching lines @@
   /// One of the following must hold:
   /// - At least one argument is null.
   /// - Arguments are both strings, or both booleans, or both numbers.
   LooseEq,
 
   /// Negated version of [LooseEq]. Introduced by [LogicalRewriter] in Tree IR.
   LooseNeq,
 
   /// Returns true if the argument is false, +0. -0, NaN, the empty string,
   /// or null.
-  IsFalsy
+  IsFalsy,
+
+  /// Returns true if the argument is a number.
+  ///
+  /// Compiles to `typeof x === 'number'`
+  IsNumber,
+
+  /// Returns true if the argument is not a number.
+  ///
+  /// Compiles to `typeof x !== 'number'`.
+  IsNotNumber,
+
+  /// Returns true if the argument is an integer, false if it is a double or
+  /// null, and unspecified if it is anything else.
+  ///
+  /// The argument must be repeated 2 times.
+  ///
+  /// Compiles to `Math.floor(x) === x`
+  IsFloor,
+
+  /// Returns true if the argument is an integer.
+  ///
+  /// The argument must be repeated 3 times.
+  ///
+  /// Compiles to `typeof x === 'number' && Math.floor(x) === x`
+  IsNumberAndFloor,
 }