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

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 37 matching lines @@
           new SsaTypePropagator(compiler),
           // Run a dead code eliminator before LICM because dead
           // interceptors are often in the way of LICM'able instructions.
           new SsaDeadCodeEliminator(compiler, this),
           new SsaGlobalValueNumberer(compiler),
           // After GVN, some instructions might need their type to be
           // updated because they now have different inputs.
           new SsaTypePropagator(compiler),
           new SsaCodeMotion(),
           new SsaLoadElimination(compiler),
+          new SsaRedundantPhiEliminator(),
           new SsaDeadPhiEliminator(),
           new SsaTypePropagator(compiler),
           new SsaValueRangeAnalyzer(compiler, constantSystem, this, work),
           // Previous optimizations may have generated new
           // opportunities for instruction simplification.
           new SsaInstructionSimplifier(constantSystem, backend, this, work),
           new SsaCheckInserter(
               trustPrimitives, backend, work, context.boundsChecked),
       ];
       phases.forEach(runPhase);
@@ skipping 766 matching lines @@
           type,
           HTypeConversion.CHECKED_MODE_CHECK);
       if (other != value) {
         node.block.addBefore(node, other);
         value = other;
       }
     }
     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:
     //
     //     "" + R                ->  R
     //     L + ""                ->  L
     //     "L" + "R"             ->  "LR"
     //     (prefix + "L") + "R"  ->  prefix + "LR"
     //
     StringConstantValue getString(HInstruction instruction) {
       if (!instruction.isConstantString()) return null;
@@ skipping 1411 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }