Limit EatAtLeast recursion by a budget.

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 2281 matching lines @@
 
   // If we get here code has been generated for this node too many times or
   // recursion is too deep.  Time to switch to a generic version.  The code for
   // generic versions above can handle deep recursion properly.
   trace->Flush(compiler, this);
   return DONE;
 }
 
 
 int ActionNode::EatsAtLeast(int still_to_find,
-                            int recursion_depth,
+                            int budget,
                             bool not_at_start) {
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
+  if (budget <= 0) return 0;
   if (type_ == POSITIVE_SUBMATCH_SUCCESS) return 0;  // Rewinds input!
   return on_success()->EatsAtLeast(still_to_find,
-                                   recursion_depth + 1,
+                                   budget - 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, budget - 1, bm, not_at_start);
+    on_success()->FillInBMInfo(offset, budget - 1, bm, not_at_start);
   }
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 int AssertionNode::EatsAtLeast(int still_to_find,
-                               int recursion_depth,
+                               int budget,
                                bool not_at_start) {
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
+  if (budget <= 0) 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,
+                                   budget - 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, budget - 1, bm, not_at_start);
+  on_success()->FillInBMInfo(offset, budget - 1, bm, not_at_start);
   SaveBMInfo(bm, not_at_start, offset);
 }
 
 
 int BackReferenceNode::EatsAtLeast(int still_to_find,
-                                   int recursion_depth,
+                                   int budget,
                                    bool not_at_start) {
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
+  if (budget <= 0) return 0;
   return on_success()->EatsAtLeast(still_to_find,
-                                   recursion_depth + 1,
+                                   budget - 1,
                                    not_at_start);
 }
 
 
 int TextNode::EatsAtLeast(int still_to_find,
-                          int recursion_depth,
+                          int budget,
                           bool not_at_start) {
   int answer = Length();
   if (answer >= still_to_find) return answer;
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return answer;
+  if (budget <= 0) return answer;
   // We are not at start after this node so we set the last argument to 'true'.
   return answer + on_success()->EatsAtLeast(still_to_find - answer,
-                                            recursion_depth + 1,
+                                            budget - 1,
                                             true);
 }
 
 
 int NegativeLookaheadChoiceNode::EatsAtLeast(int still_to_find,
-                                             int recursion_depth,
+                                             int budget,
                                              bool not_at_start) {
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
+  if (budget <= 0) return 0;
   // Alternative 0 is the negative lookahead, alternative 1 is what comes
   // afterwards.
   RegExpNode* node = alternatives_->at(1).node();
-  return node->EatsAtLeast(still_to_find, recursion_depth + 1, not_at_start);
+  return node->EatsAtLeast(still_to_find, budget - 1, not_at_start);
 }
 
 
 void NegativeLookaheadChoiceNode::GetQuickCheckDetails(
     QuickCheckDetails* details,
     RegExpCompiler* compiler,
     int filled_in,
     bool not_at_start) {
   // Alternative 0 is the negative lookahead, alternative 1 is what comes
   // afterwards.
   RegExpNode* node = alternatives_->at(1).node();
   return node->GetQuickCheckDetails(details, compiler, filled_in, not_at_start);
 }
 
 
 int ChoiceNode::EatsAtLeastHelper(int still_to_find,
-                                  int recursion_depth,
+                                  int budget,
                                   RegExpNode* ignore_this_node,
                                   bool not_at_start) {
-  if (recursion_depth > RegExpCompiler::kMaxRecursion) return 0;
+  if (budget <= 0) return 0;
   int min = 100;
   int choice_count = alternatives_->length();
+  budget = (budget - 1) / choice_count;
   for (int i = 0; i < choice_count; i++) {
     RegExpNode* node = alternatives_->at(i).node();
     if (node == ignore_this_node) continue;
-    int node_eats_at_least = node->EatsAtLeast(still_to_find,
-                                               recursion_depth + 1,
-                                               not_at_start);
+    int node_eats_at_least =
+        node->EatsAtLeast(still_to_find, budget, not_at_start);
     if (node_eats_at_least < min) min = node_eats_at_least;
+    if (min == 0) return 0;
   }
   return min;
 }
 
 
 int LoopChoiceNode::EatsAtLeast(int still_to_find,
-                                int recursion_depth,
+                                int budget,
                                 bool not_at_start) {
   return EatsAtLeastHelper(still_to_find,
-                           recursion_depth,
+                           budget - 1,
                            loop_node_,
                            not_at_start);
 }
 
 
 int ChoiceNode::EatsAtLeast(int still_to_find,
-                            int recursion_depth,
+                            int budget,
                             bool not_at_start) {
   return EatsAtLeastHelper(still_to_find,
-                           recursion_depth,
+                           budget,
                            NULL,
                            not_at_start);
 }
 
 
 // Takes the left-most 1-bit and smears it out, setting all bits to its right.
 static inline uint32_t SmearBitsRight(uint32_t v) {
   v |= v >> 1;
   v |= v >> 2;
   v |= v >> 4;
@@ skipping 535 matching lines @@
   if (body_can_be_zero_length_ || info()->visited) return;
   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 ||
-      budget <= 0) {
+  if (body_can_be_zero_length_ || budget <= 0) {
     bm->SetRest(offset);
     SaveBMInfo(bm, not_at_start, offset);
     return;
   }
-  ChoiceNode::FillInBMInfo(
-      offset, recursion_depth + 1, budget - 1, bm, not_at_start);
+  ChoiceNode::FillInBMInfo(offset, budget - 1, bm, not_at_start);
   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 76 matching lines @@
 
 
 // Emit the code to handle \b and \B (word-boundary or non-word-boundary).
 void AssertionNode::EmitBoundaryCheck(RegExpCompiler* compiler, Trace* trace) {
   RegExpMacroAssembler* assembler = compiler->macro_assembler();
   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));
+        Min(kMaxLookaheadForBoyerMoore, EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                                    kFillInBMBudget,
+                                                    not_at_start));
     if (eats_at_least >= 1) {
       BoyerMooreLookahead* bm =
           new(zone()) BoyerMooreLookahead(eats_at_least, compiler, zone());
-      FillInBMInfo(0, 0, kFillInBMBudget, bm, not_at_start);
+      FillInBMInfo(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 911 matching lines @@
         // At this point we know that we are at a non-greedy loop that will eat
         // any character one at a time.  Any non-anchored regexp has such a
         // loop prepended to it in order to find where it starts.  We look for
         // a pattern of the form ...abc... where we can look 6 characters ahead
         // and step forwards 3 if the character is not one of abc.  Abc need
         // not be atoms, they can be any reasonably limited character class or
         // small alternation.
         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));
+          eats_at_least = Min(kMaxLookaheadForBoyerMoore,
+                              EatsAtLeast(kMaxLookaheadForBoyerMoore,
+                                          kFillInBMBudget,
+                                          not_at_start));
           if (eats_at_least >= 1) {
             BoyerMooreLookahead* bm =
                 new(zone()) BoyerMooreLookahead(eats_at_least,
                                                 compiler,
                                                 zone());
             GuardedAlternative alt0 = alternatives_->at(0);
-            alt0.node()->FillInBMInfo(0, 0, kFillInBMBudget, bm, not_at_start);
+            alt0.node()->FillInBMInfo(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) {
     // Save some time by looking at most one machine word ahead.
-    eats_at_least = EatsAtLeast(compiler->ascii() ? 4 : 2, 0, not_at_start);
+    eats_at_least =
+        EatsAtLeast(compiler->ascii() ? 4 : 2, kFillInBMBudget, not_at_start);
   }
   int preload_characters = CalculatePreloadCharacters(compiler, eats_at_least);
 
   bool preload_is_current = !skip_was_emitted &&
       (current_trace->characters_preloaded() == preload_characters);
   bool preload_has_checked_bounds = preload_is_current;
 
   AlternativeGenerationList alt_gens(choice_count, zone());
 
   // For now we just call all choices one after the other.  The idea ultimately
@@ skipping 1735 matching lines @@
   EnsureAnalyzed(that->on_success());
 }
 
 
 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 = (budget - 1) / 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, budget, bm, not_at_start);
+    alt.node()->FillInBMInfo(offset, 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 231 matching lines @@
   }
 
   return compiler.Assemble(&macro_assembler,
                            node,
                            data->capture_count,
                            pattern);
 }
 
 
 }}  // namespace v8::internal