Limit work done analyzing regexps with very large fanout.

src/jsregexp.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2174 matching lines @@
   if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
   if (type_ == POSITIVE_SUBMATCH_SUCCESS) return 0;  // Rewinds input!
   return on_success()->EatsAtLeast(still_to_find,
                                    recursion_depth + 1,
                                    not_at_start);
 }
 
 
 void ActionNode::FillInBMInfo(int offset,
                               int recursion_depth,
+                              int budget,
                               BoyerMooreLookahead* bm,
                               bool not_at_start) {
   if (type_ == BEGIN_SUBMATCH) {
     bm->SetRest(offset);
   } else if (type_ != POSITIVE_SUBMATCH_SUCCESS) {
-    on_success()->FillInBMInfo(offset, recursion_depth + 1, bm, not_at_start);
+    on_success()->FillInBMInfo(
+        offset, recursion_depth + 1, budget - 1, bm, not_at_start);
   }
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 int AssertionNode::EatsAtLeast(int still_to_find,
                                int recursion_depth,
                                bool not_at_start) {
   if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
   // If we know we are not at the start and we are asked "how many characters
   // will you match if you succeed?" then we can answer anything since false
   // implies false.  So lets just return the max answer (still_to_find) since
   // that won't prevent us from preloading a lot of characters for the other
   // branches in the node graph.
   if (type() == AT_START && not_at_start) return still_to_find;
   return on_success()->EatsAtLeast(still_to_find,
                                    recursion_depth + 1,
                                    not_at_start);
 }
 
 
 void AssertionNode::FillInBMInfo(int offset,
                                  int recursion_depth,
+                                 int budget,
                                  BoyerMooreLookahead* bm,
                                  bool not_at_start) {
   // Match the behaviour of EatsAtLeast on this node.
   if (type() == AT_START && not_at_start) return;
-  on_success()->FillInBMInfo(offset, recursion_depth + 1, bm, not_at_start);
+  on_success()->FillInBMInfo(
+      offset, recursion_depth + 1, budget - 1, bm, not_at_start);
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 int BackReferenceNode::EatsAtLeast(int still_to_find,
                                    int recursion_depth,
                                    bool not_at_start) {
   if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
   return on_success()->EatsAtLeast(still_to_find,
                                    recursion_depth + 1,
@@ skipping 562 matching lines @@
   VisitMarker marker(info());
   return ChoiceNode::GetQuickCheckDetails(details,
                                           compiler,
                                           characters_filled_in,
                                           not_at_start);
 }
 
 
 void LoopChoiceNode::FillInBMInfo(int offset,
                                   int recursion_depth,
+                                  int budget,
                                   BoyerMooreLookahead* bm,
                                   bool not_at_start) {
   if (body_can_be_zero_length_ ||
-      recursion_depth > RegExpCompiler::kMaxRecursion) {
+      recursion_depth > RegExpCompiler::kMaxRecursion ||
+      budget <= 0) {
     bm->SetRest(offset);
     SaveBMInfo(bm, not_at_start, offset);
     return;
   }
-  ChoiceNode::FillInBMInfo(offset, recursion_depth + 1, bm, not_at_start);
+  ChoiceNode::FillInBMInfo(
+      offset, recursion_depth + 1, budget, bm, not_at_start);

[ulan, 2012/06/01 11:24:04]

We either need to decrement the budget or add a comment why it is not necessary.

   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 void ChoiceNode::GetQuickCheckDetails(QuickCheckDetails* details,
                                       RegExpCompiler* compiler,
                                       int characters_filled_in,
                                       bool not_at_start) {
   not_at_start = (not_at_start || not_at_start_);
   int choice_count = alternatives_->length();
@@ skipping 81 matching lines @@
   Trace::TriBool next_is_word_character = Trace::UNKNOWN;
   bool not_at_start = (trace->at_start() == Trace::FALSE);
   BoyerMooreLookahead* lookahead = bm_info(not_at_start);
   if (lookahead == NULL) {
     int eats_at_least =
         Min(kMaxLookaheadForBoyerMoore,
             EatsAtLeast(kMaxLookaheadForBoyerMoore, 0, not_at_start));
     if (eats_at_least >= 1) {
       BoyerMooreLookahead* bm =
           new BoyerMooreLookahead(eats_at_least, compiler);
-      FillInBMInfo(0, 0, bm, not_at_start);
+      FillInBMInfo(0, 0, kFillInBMBudget, bm, not_at_start);
       if (bm->at(0)->is_non_word()) next_is_word_character = Trace::FALSE;
       if (bm->at(0)->is_word()) next_is_word_character = Trace::TRUE;
     }
   } else {
     if (lookahead->at(0)->is_non_word()) next_is_word_character = Trace::FALSE;
     if (lookahead->at(0)->is_word()) next_is_word_character = Trace::TRUE;
   }
   bool at_boundary = (type_ == AssertionNode::AT_BOUNDARY);
   if (next_is_word_character == Trace::UNKNOWN) {
     Label before_non_word;
@@ skipping 917 matching lines @@
         ASSERT(trace->is_trivial());  // This is the case on LoopChoiceNodes.
         BoyerMooreLookahead* lookahead = bm_info(not_at_start);
         if (lookahead == NULL) {
           eats_at_least =
               Min(kMaxLookaheadForBoyerMoore,
                   EatsAtLeast(kMaxLookaheadForBoyerMoore, 0, not_at_start));
           if (eats_at_least >= 1) {
             BoyerMooreLookahead* bm =
                 new BoyerMooreLookahead(eats_at_least, compiler);
             GuardedAlternative alt0 = alternatives_->at(0);
-            alt0.node()->FillInBMInfo(0, 0, bm, not_at_start);
+            alt0.node()->FillInBMInfo(0, 0, kFillInBMBudget, bm, not_at_start);
             skip_was_emitted = bm->EmitSkipInstructions(macro_assembler);
           }
         } else {
           skip_was_emitted = lookahead->EmitSkipInstructions(macro_assembler);
         }
       }
     }
   }
 
   if (eats_at_least == kEatsAtLeastNotYetInitialized) {
@@ skipping 1720 matching lines @@
 }
 
 
 void Analysis::VisitAssertion(AssertionNode* that) {
   EnsureAnalyzed(that->on_success());
 }
 
 
 void BackReferenceNode::FillInBMInfo(int offset,
                                      int recursion_depth,
+                                     int budget,
                                      BoyerMooreLookahead* bm,
                                      bool not_at_start) {
   // Working out the set of characters that a backreference can match is too
   // hard, so we just say that any character can match.
   bm->SetRest(offset);
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 STATIC_ASSERT(BoyerMoorePositionInfo::kMapSize ==
               RegExpMacroAssembler::kTableSize);
 
 
 void ChoiceNode::FillInBMInfo(int offset,
                               int recursion_depth,
+                              int budget,
                               BoyerMooreLookahead* bm,
                               bool not_at_start) {
   ZoneList<GuardedAlternative>* alts = alternatives();
+  budget /= alts->length();
   for (int i = 0; i < alts->length(); i++) {
     GuardedAlternative& alt = alts->at(i);
     if (alt.guards() != NULL && alt.guards()->length() != 0) {
       bm->SetRest(offset);  // Give up trying to fill in info.
       SaveBMInfo(bm, not_at_start, offset);
       return;
     }
-    alt.node()->FillInBMInfo(offset, recursion_depth + 1, bm, not_at_start);
+    alt.node()->FillInBMInfo(
+        offset, recursion_depth + 1, budget, bm, not_at_start);
   }
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 void TextNode::FillInBMInfo(int initial_offset,
                             int recursion_depth,
+                            int budget,
                             BoyerMooreLookahead* bm,
                             bool not_at_start) {
   if (initial_offset >= bm->length()) return;
   int offset = initial_offset;
   int max_char = bm->max_char();
   for (int i = 0; i < elements()->length(); i++) {
     if (offset >= bm->length()) {
       if (initial_offset == 0) set_bm_info(not_at_start, bm);
       return;
     }
@@ skipping 36 matching lines @@
       }
       offset++;
     }
   }
   if (offset >= bm->length()) {
     if (initial_offset == 0) set_bm_info(not_at_start, bm);
     return;
   }
   on_success()->FillInBMInfo(offset,
                              recursion_depth + 1,
+                             budget - 1,
                              bm,
                              true);  // Not at start after a text node.
   if (initial_offset == 0) set_bm_info(not_at_start, bm);
 }
 
 
 // -------------------------------------------------------------------
 // Dispatch table construction
 
 
@@ skipping 218 matching lines @@
   macro_assembler.set_global(is_global);
 
   return compiler.Assemble(&macro_assembler,
                            node,
                            data->capture_count,
                            pattern);
 }
 
 
 }}  // namespace v8::internal