Bugfix for sanity check of changed scopes.

Clone the AST at the beginning of a loopable pass, instead of after the sanity check. This way, if there are two optimization loops, and the non-loopable passes between the loops change the AST, the 1st pass of the 2nd loop doesn't use a stale clone for its sanity check.

Also, don't do the scope-change sanity check for cross-module-code-motion, it's not relevant.
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=66241818

Author: blickly

src/com/google/javascript/jscomp/Compiler.java

@@ -103,6 +103,7 @@ public class Compiler extends AbstractCompiler {
 
   // Used in PerformanceTracker
   static final String PARSING_PASS_NAME = "parseInputs";
+  static final String CROSS_MODULE_CODE_MOTION_NAME = "crossModuleCodeMotion";
 
   private static final String CONFIG_RESOURCE =
       "com.google.javascript.jscomp.parsing.ParserConfig";

src/com/google/javascript/jscomp/DefaultPassConfig.java

@@ -1962,7 +1962,7 @@ protected CompilerPass create(AbstractCompiler compiler) {
    * Move global symbols to a deeper common module
    */
   final PassFactory crossModuleCodeMotion =
-      new PassFactory("crossModuleCodeMotion", false) {
+      new PassFactory(Compiler.CROSS_MODULE_CODE_MOTION_NAME, false) {
     @Override
     protected CompilerPass create(AbstractCompiler compiler) {
       return new CrossModuleCodeMotion(

src/com/google/javascript/jscomp/PhaseOptimizer.java

@@ -187,8 +187,10 @@ void setSanityCheck(PassFactory sanityCheck) {
   }
 
   private void setSanityCheckState() {
-    lastAst = jsRoot.cloneTree();
-    mtoc = NodeUtil.mapMainToClone(jsRoot, lastAst);
+    if (inLoop) {
+      lastAst = jsRoot.cloneTree();
+      mtoc = NodeUtil.mapMainToClone(jsRoot, lastAst);
+    }
   }
 
   /**
@@ -236,7 +238,6 @@ private void maybeSanityCheck(Node externs, Node root) {
       sanityCheck.create(compiler).process(externs, root);
       if (inLoop) {
         NodeUtil.verifyScopeChanges(mtoc, jsRoot, true, compiler);
-        setSanityCheckState();
       }
     }
   }
@@ -261,6 +262,18 @@ class NamedPass implements CompilerPass {
     @Override
     public void process(Node externs, Node root) {
       logger.fine(name);
+      // Cross-module code motion is a loopable pass on its own, but does not
+      // participate in the other optimization loops, and is not relevant to
+      // tracking changed scopes.
+      // Don't set inLoop, to avoid the special sanity check.
+      if (name.equals(Compiler.CROSS_MODULE_CODE_MOTION_NAME)) {
+        inLoop = false;
+      }
+      if (sanityCheck != null) {
+        // Before running the pass, clone the AST so you can sanity-check the
+        // changed AST against the clone after the pass finishes.
+        setSanityCheckState();
+      }
       if (tracker != null) {
         tracker.recordPassStart(name, factory.isOneTimePass());
       }

test/com/google/javascript/jscomp/MultiPassTest.java

@@ -17,6 +17,7 @@
 package com.google.javascript.jscomp;
 
 import com.google.common.collect.Lists;
+import com.google.javascript.rhino.Node;
 
 import java.util.List;
 
@@ -120,6 +121,14 @@ public void testTopScopeChange() {
     test("var x = 1, y = x, z = x + y;", "var z = 2;");
   }
 
+  public void testTwoOptimLoopsNoCrash() {
+    passes = Lists.newLinkedList();
+    addInlineVariables();
+    addSmartNamePass();
+    addInlineVariables();
+    test("var x = '';", "");
+  }
+
   private void addCollapseObjectLiterals() {
     passes.add(
         new PassFactory("collapseObjectLiterals", false) {
@@ -200,4 +209,21 @@ protected CompilerPass create(AbstractCompiler compiler) {
           }
         });
   }
+
+  private void addSmartNamePass() {
+    passes.add(
+        new PassFactory("smartNamePass", true) {
+          @Override
+          protected CompilerPass create(final AbstractCompiler compiler) {
+            return new CompilerPass() {
+              @Override
+              public void process(Node externs, Node root) {
+                NameAnalyzer na = new NameAnalyzer(compiler, false);
+                na.process(externs, root);
+                na.removeUnreferenced();
+              }
+            };
+          }
+        });
+  }
 }