Fix mangling of local variables when their name conflict with Dart2JS's temporaries.

lib/compiler/implementation/ssa/codegen.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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   SsaCodeGeneratorTask(Compiler compiler) : super(compiler);
   String get name() => 'SSA code generator';
 
 
   String generateMethod(WorkItem work, HGraph graph) {
@@ skipping 82 matching lines @@
   static final int STATE_EXPRESSION = 3;
   static final int STATE_DECLARATION = 4;
 
   final Compiler compiler;
   final WorkItem work;
   final StringBuffer buffer;
   final String parameters;
 
   final Map<Element, String> parameterNames;
   final Map<int, String> names;
+  final Set<String> usedNames;
   final Map<String, int> prefixes;
   final Set<HInstruction> generateAtUseSite;
   final Map<HPhi, String> logicalOperations;
   final Map<Element, ElementAction> breakAction;
   final Map<Element, ElementAction> continueAction;
   final Equivalence<HPhi> phiEquivalence;
 
   Element equalsNullElement;
   int indent = 0;
   int expectedPrecedence = JSPrecedence.STATEMENT_PRECEDENCE;
@@ skipping 22 matching lines @@
   bool isGenerateAtUseSite(HInstruction instruction) {
     return generateAtUseSite.contains(instruction);
   }
 
   SsaCodeGenerator(this.compiler,
                    this.work,
                    this.parameters,
                    this.parameterNames)
     : names = new Map<int, String>(),
       prefixes = new Map<String, int>(),
+      usedNames = new Set<String>(),
       buffer = new StringBuffer(),
       generateAtUseSite = new Set<HInstruction>(),
       logicalOperations = new Map<HPhi, String>(),
       breakAction = new Map<Element, ElementAction>(),
       continueAction = new Map<Element, ElementAction>(),
       phiEquivalence = new Equivalence<HPhi>() {
 
     for (final name in parameterNames.getValues()) {
       prefixes[name] = 0;
     }
@@ skipping 110 matching lines @@
 
   void visitConditionGraph(SubGraph conditionSubGraph) {
     visitExpressionGraph(conditionSubGraph);
   }
 
   String temporary(HInstruction instruction) {
     int id = instruction.id;
     String name = names[id];
     if (name !== null) return name;
 
+    String prefix;
     if (instruction.sourceElement !== null) {
       Element element = instruction.sourceElement;
-      String prefix;
       if (element !== null && !element.name.isEmpty()) {
         prefix = element.name.slowToString();
       } else {
         prefix = 'v';
       }
-      if (!prefixes.containsKey(prefix)) {
-        prefixes[prefix] = 0;
-        return newName(id, prefix);
-      } else {
-        return newName(id, '${prefix}_${prefixes[prefix]++}');
+    } else {
+      prefix = 't';
+    }
+    
+    while (usedNames.contains(prefix)) {
+      prefix = '${prefix}_';
+    }
+
+    if (!prefixes.containsKey(prefix)) {
+      prefixes[prefix] = 0;
+      return newName(id, prefix);
+    } else {
+      name = '${prefix}${prefixes[prefix]++}';
+      while (usedNames.contains(name)) {
+        name = '${prefix}${prefixes[prefix]++}';
       }
-    } else {
-      String prefix = 't';
-      if (!prefixes.containsKey(prefix)) prefixes[prefix] = 0;
-      return newName(id, '${prefix}${prefixes[prefix]++}');
+      return newName(id, name);
     }
   }
 
   bool temporaryExists(HInstruction instruction) {
     return names.containsKey(instruction.id);
   }
 
   String newName(int id, String name) {
     String result = JsNames.getValid(name);
     names[id] = result;
+    usedNames.add(result);
     return result;
   }
 
   /**
     * Only visits the arguments starting at inputs[HInvoke.ARGUMENTS_OFFSET].
     */
   void visitArguments(List<HInstruction> inputs) {
     assert(inputs.length >= HInvoke.ARGUMENTS_OFFSET);
     buffer.add('(');
     for (int i = HInvoke.ARGUMENTS_OFFSET; i < inputs.length; i++) {
@@ skipping 1605 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endElse(HIf node) {
     if (node.elseBlock.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }