dart2js: Constant fold num.round()

pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.dart

 // Copyright (c) 2013, 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 '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../elements/elements.dart';
 import '../js_backend/js_backend.dart';
 import '../types/types.dart';
@@ skipping 16 matching lines @@
       HInvokeDynamic instruction, Compiler compiler) {
     return TypeMaskFactory.inferredTypeForSelector(
         instruction.selector, instruction.mask, compiler);
   }
 
   HInstruction tryConvertToBuiltin(
       HInvokeDynamic instruction, Compiler compiler) {
     return null;
   }
 
+  void clearAllSideEffects(HInstruction instruction) {
+    instruction.sideEffects.clearAllSideEffects();
+    instruction.sideEffects.clearAllDependencies();
+    instruction.setUseGvn();
+  }
+
   Operation operation(ConstantSystem constantSystem) => null;
 
   static InvokeDynamicSpecializer lookupSpecializer(Selector selector) {
     if (selector.isIndex) {
       return const IndexSpecializer();
     } else if (selector.isIndexSet) {
       return const IndexAssignSpecializer();
     } else if (selector.isOperator) {
       if (selector.name == 'unary-') {
         return const UnaryNegateSpecializer();
@@ skipping 31 matching lines @@
         return const GreaterSpecializer();
       } else if (selector.name == '>=') {
         return const GreaterEqualSpecializer();
       }
     } else if (selector.isCall) {
       if (selector.argumentCount == 1 && selector.namedArguments.length == 0) {
         if (selector.name == 'codeUnitAt') {
           return const CodeUnitAtSpecializer();
         }
       }
+      if (selector.argumentCount == 0 && selector.namedArguments.length == 0) {
+        if (selector.name == 'round') {
+          return const RoundSpecializer();
+        }
+      }
     }
     return const InvokeDynamicSpecializer();
   }
 }
 
 class IndexAssignSpecializer extends InvokeDynamicSpecializer {
   const IndexAssignSpecializer();
 
   HInstruction tryConvertToBuiltin(
       HInvokeDynamic instruction, Compiler compiler) {
@@ skipping 114 matching lines @@
       HInstruction builtin = newBuiltinVariant(instruction, compiler);
       if (builtin != null) return builtin;
       // Even if there is no builtin equivalent instruction, we know
       // the instruction does not have any side effect, and that it
       // can be GVN'ed.
       clearAllSideEffects(instruction);
     }
     return null;
   }
 
-  void clearAllSideEffects(HInstruction instruction) {
-    instruction.sideEffects.clearAllSideEffects();
-    instruction.sideEffects.clearAllDependencies();
-    instruction.setUseGvn();
-  }
-
   bool inputsArePositiveIntegers(HInstruction instruction, Compiler compiler) {
     HInstruction left = instruction.inputs[1];
     HInstruction right = instruction.inputs[2];
     return left.isPositiveIntegerOrNull(compiler) &&
         right.isPositiveIntegerOrNull(compiler);
   }
 
   bool inputsAreUInt31(HInstruction instruction, Compiler compiler) {
     HInstruction left = instruction.inputs[1];
     HInstruction right = instruction.inputs[2];
@@ skipping 514 matching lines @@
     return constantSystem.codeUnitAt;
   }
 
   HInstruction tryConvertToBuiltin(
       HInvokeDynamic instruction, Compiler compiler) {
     // TODO(sra): Implement a builtin HCodeUnitAt instruction and the same index
     // bounds checking optimizations as for HIndex.
     return null;
   }
 }
+
+class RoundSpecializer extends InvokeDynamicSpecializer {
+  const RoundSpecializer();
+
+  UnaryOperation operation(ConstantSystem constantSystem) {
+    return constantSystem.round;
+  }
+
+  HInstruction tryConvertToBuiltin(
+      HInvokeDynamic instruction, Compiler compiler) {
+    HInstruction receiver = instruction.getDartReceiver(compiler);
+    if (receiver.isNumberOrNull(compiler)) {
+      // Even if there is no builtin equivalent instruction, we know the
+      // instruction does not have any side effect, and that it can be GVN'ed.
+      clearAllSideEffects(instruction);
+    }
+    return null;
+  }
+}