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

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

Index: pkg/compiler/lib/src/ssa/optimize.dart
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 5c6ec19ebf89fde870b1a0d6d10ffff330d6dfd3..9bf79b3b452b0a184f1b54127985793c7dc010fb 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -1001,6 +1001,33 @@ class SsaDeadCodeEliminator extends HGraphVisitor implements OptimizationPhase {
     return zapInstructionCache;
   }
 
+  /// Returns true of [foreign] will throw an noSuchMethod error if
+  /// receiver is `null` before having any other side-effects.
+  bool templateThrowsNSM(HForeignCode foreign, HInstruction receiver) {

[floitsch, 2015/03/23 00:48:38]

templateThrowsNsmOnNull

[herhut, 2015/03/24 11:31:43]

Done.

+    // 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].
@@ -1012,6 +1039,9 @@ class SsaDeadCodeEliminator extends HGraphVisitor implements OptimizationPhase {
           && current.canThrow()) {
         return true;
       }
+      if (current is HForeignCode && templateThrowsNSM(current, receiver)) {
+        return true;
+      }
       if (current.canThrow() || current.sideEffects.hasSideEffects()) {
         return false;
       }