Rewrite for-in loop as indexing loop for JavaScript indexable arrays

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 d4e546842a3747165e85e2eb5aa7fe52b504655d..8b946af927c5743811020d055e367206dfbd514d 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -55,6 +55,7 @@ class SsaOptimizerTask extends CompilerTask {
           new SsaTypePropagator(compiler),
           new SsaCodeMotion(),
           new SsaLoadElimination(compiler),
+          new SsaRedundantPhiEliminator(),
           new SsaDeadPhiEliminator(),
           new SsaTypePropagator(compiler),
           new SsaValueRangeAnalyzer(compiler, constantSystem, this, work),
@@ -841,6 +842,19 @@ class SsaInstructionSimplifier extends HBaseVisitor
     return new HFieldSet(field, receiver, value);
   }
 
+  HInstruction visitInvokeStatic(HInvokeStatic node) {
+    if (node.element == backend.getThrowConcurrentModificationError()) {

[sra1, 2015/04/16 19:27:09]

If we agree on this general approach I will add an InvokeStaticSpecializer that
we set in construction.

+      if (node.inputs.length == 2) {
+        HInstruction firstArgument = node.inputs[0];
+        if (firstArgument is HConstant) {
+          HConstant constant = firstArgument;
+          if (constant.constant.isTrue) return constant;
+        }
+      }
+    }
+    return node;
+  }
+
   HInstruction visitStringConcat(HStringConcat node) {
     // Simplify string concat:
     //