Remove NSM if followed by a foreign with same effect.~

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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 983 matching lines @@
   HInstruction get zapInstruction {
     if (zapInstructionCache == null) {
       // A constant with no type does not pollute types at phi nodes.
       ConstantValue constant =
           new DummyConstantValue(const TypeMask.nonNullEmpty());
       zapInstructionCache = analyzer.graph.addConstant(constant, compiler);
     }
     return zapInstructionCache;
   }
 
+  /// Returns true of [foreign] will throw an noSuchMethod error if
+  /// receiver is `null` before having any other side-effects.
+  bool templateThrowsNSMonNull(HForeignCode foreign, HInstruction receiver) {
+    // We look for a template of the form
+    //
+    // #.something -or- #.something()
+    //
+    // where # is substituted by receiver.
+    js.Template template = foreign.codeTemplate;
+    js.Node node = template.ast;
+    // #.something = ...
+    if (node is js.Assignment) {
+      js.Assignment assignment = node;
+      node = assignment.leftHandSide;
+    }
+
+    // #.something
+    if (node is js.PropertyAccess) {
+      js.PropertyAccess access = node;
+      if (access.receiver is js.InterpolatedExpression) {
+        js.InterpolatedExpression hole = access.receiver;
+        return hole.isPositional && foreign.inputs.first == receiver;
+      }
+    }
+    return false;
+  }
+
   /// Returns whether the next throwing instruction that may have side
   /// effects after [instruction], throws [NoSuchMethodError] on the
   /// same receiver of [instruction].
   bool hasFollowingThrowingNSM(HInstruction instruction) {
     HInstruction receiver = instruction.getDartReceiver(compiler);
     HInstruction current = instruction.next;
     do {
       if ((current.getDartReceiver(compiler) == receiver)
           && current.canThrow()) {
         return true;
       }
+      if (current is HForeignCode &&
+          templateThrowsNSMonNull(current, receiver)) {
+        return true;
+      }
       if (current.canThrow() || current.sideEffects.hasSideEffects()) {
         return false;
       }
       HInstruction next = current.next;
       if (next == null) {
         // We do not merge blocks in our SSA graph, so if this block just jumps
         // to a single successor, visit the successor, avoiding back-edges.
         HBasicBlock successor;
         if (current is HGoto) {
           successor = current.block.successors.single;
@@ skipping 1180 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }