New shot at mangling: try cleaning this up a bit.

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 137 matching lines @@
       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;
     }
 
+    // Create a namespace for temporaries.
+    prefixes['t'] = 0;
+
     equalsNullElement =
         compiler.builder.interceptors.getEqualsNullInterceptor();
   }
 
   abstract visitTypeGuard(HTypeGuard node);
 
   abstract beginGraph(HGraph graph);
   abstract endGraph(HGraph graph);
 
   abstract beginLoop(HBasicBlock block);
@@ skipping 99 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;
+    String prefix = 't';
     if (instruction.sourceElement !== null) {
       Element element = instruction.sourceElement;
       if (element !== null && !element.name.isEmpty()) {
         prefix = element.name.slowToString();
-      } else {
-        prefix = 'v';
+        // If we've never seen that prefix before, try to use it
+        // directly.
+        if (!prefixes.containsKey(prefix)) {
+          // Make sure the variable name does not conflict with our mangling.
+          while (usedNames.contains(prefix)) {
+            prefix = '${prefix}_';
+          }
+          prefixes[prefix] = 0;
+          return newName(id, prefix);
+        }
       }
-    } else {
-      prefix = 't';
-    }
-    
-    while (usedNames.contains(prefix)) {
-      prefix = '${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]++}';
-      while (usedNames.contains(name)) {
-        name = '${prefix}${prefixes[prefix]++}';
-      }
-      return newName(id, name);
     }
+    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);
@@ skipping 1615 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endElse(HIf node) {
     if (node.elseBlock.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }