Revert of Reland of 'Optimize trivial regexp disjunctions' CL 1176453002

src/jsregexp.cc

Index: src/jsregexp.cc
diff --git a/src/jsregexp.cc b/src/jsregexp.cc
index e284e8cb15f3233eee2533bc9efda8b6735bd1e3..b410d47b3d1fd41d93dd5d26cf8386050375745e 100644
--- a/src/jsregexp.cc
+++ b/src/jsregexp.cc
@@ -4817,200 +4817,10 @@
 }
 
 
-int CompareFirstChar(RegExpTree* const* a, RegExpTree* const* b) {
-  RegExpAtom* atom1 = (*a)->AsAtom();
-  RegExpAtom* atom2 = (*b)->AsAtom();
-  uc16 character1 = atom1->data().at(0);
-  uc16 character2 = atom2->data().at(0);
-  if (character1 < character2) return -1;
-  if (character1 > character2) return 1;
-  return 0;
-}
-
-
-// We can stable sort runs of atoms, since the order does not matter if they
-// start with different characters.
-// Returns true if any consecutive atoms were found.
-bool RegExpDisjunction::SortConsecutiveAtoms(RegExpCompiler* compiler) {
-  ZoneList<RegExpTree*>* alternatives = this->alternatives();
-  int length = alternatives->length();
-  bool found_consecutive_atoms = false;
-  for (int i = 0; i < length; i++) {
-    while (i < length) {
-      RegExpTree* alternative = alternatives->at(i);
-      if (alternative->IsAtom()) break;
-      i++;
-    }
-    // i is length or it is the index of an atom.
-    if (i == length) break;
-    int first_atom = i;
-    i++;
-    while (i < length) {
-      RegExpTree* alternative = alternatives->at(i);
-      if (!alternative->IsAtom()) break;
-      i++;
-    }
-    // Sort atoms to get ones with common prefixes together.
-    // This step is not valid if we are in a case-independent regexp,
-    // because it would change /is|I/ to /I|is/, and order matters when
-    // the regexp parts don't match only disjoint starting points. To fix
-    // this would need a version of CompareFirstChar that uses case-
-    // independent character classes for comparison.
-    if (!compiler->ignore_case()) {
-      DCHECK_LT(first_atom, alternatives->length());
-      DCHECK_LE(i, alternatives->length());
-      DCHECK_LE(first_atom, i);
-      alternatives->StableSort(CompareFirstChar, first_atom, i - first_atom);
-    }
-    if (i - first_atom > 1) found_consecutive_atoms = true;
-  }
-  return found_consecutive_atoms;
-}
-
-
-// Optimizes ab|ac|az to a(?:b|c|d).
-void RegExpDisjunction::RationalizeConsecutiveAtoms(RegExpCompiler* compiler) {
-  Zone* zone = compiler->zone();
-  ZoneList<RegExpTree*>* alternatives = this->alternatives();
-  int length = alternatives->length();
-
-  int write_posn = 0;
-  int i = 0;
-  while (i < length) {
-    RegExpTree* alternative = alternatives->at(i);
-    if (!alternative->IsAtom()) {
-      alternatives->at(write_posn++) = alternatives->at(i);
-      i++;
-      continue;
-    }
-    RegExpAtom* atom = alternative->AsAtom();
-    uc16 common_prefix = atom->data().at(0);
-    int first_with_prefix = i;
-    int prefix_length = atom->length();
-    i++;
-    while (i < length) {
-      alternative = alternatives->at(i);
-      if (!alternative->IsAtom()) break;
-      atom = alternative->AsAtom();
-      if (atom->data().at(0) != common_prefix) break;
-      prefix_length = Min(prefix_length, atom->length());
-      i++;
-    }
-    if (i > first_with_prefix + 2) {
-      // Found worthwhile run of alternatives with common prefix of at least one
-      // character.  The sorting function above did not sort on more than one
-      // character for reasons of correctness, but there may still be a longer
-      // common prefix if the terms were similar or presorted in the input.
-      // Find out how long the common prefix is.
-      int run_length = i - first_with_prefix;
-      atom = alternatives->at(first_with_prefix)->AsAtom();
-      for (int j = 1; j < run_length && prefix_length > 1; j++) {
-        RegExpAtom* old_atom =
-            alternatives->at(j + first_with_prefix)->AsAtom();
-        for (int k = 1; k < prefix_length; k++) {
-          if (atom->data().at(k) != old_atom->data().at(k)) prefix_length = k;
-        }
-      }
-      RegExpAtom* prefix =
-          new (zone) RegExpAtom(atom->data().SubVector(0, prefix_length));
-      ZoneList<RegExpTree*>* pair = new (zone) ZoneList<RegExpTree*>(2, zone);
-      pair->Add(prefix, zone);
-      ZoneList<RegExpTree*>* suffixes =
-          new (zone) ZoneList<RegExpTree*>(run_length, zone);
-      for (int j = 0; j < run_length; j++) {
-        RegExpAtom* old_atom =
-            alternatives->at(j + first_with_prefix)->AsAtom();
-        int len = old_atom->length();
-        if (len == prefix_length) {
-          suffixes->Add(new (zone) RegExpEmpty(), zone);
-        } else {
-          RegExpTree* suffix = new (zone) RegExpAtom(
-              old_atom->data().SubVector(prefix_length, old_atom->length()));
-          suffixes->Add(suffix, zone);
-        }
-      }
-      pair->Add(new (zone) RegExpDisjunction(suffixes), zone);
-      alternatives->at(write_posn++) = new (zone) RegExpAlternative(pair);
-    } else {
-      // Just copy any non-worthwhile alternatives.
-      for (int j = first_with_prefix; j < i; j++) {
-        alternatives->at(write_posn++) = alternatives->at(j);
-      }
-    }
-  }
-  alternatives->Rewind(write_posn);  // Trim end of array.
-}
-
-
-// Optimizes b|c|z to [bcz].
-void RegExpDisjunction::FixSingleCharacterDisjunctions(
-    RegExpCompiler* compiler) {
-  Zone* zone = compiler->zone();
-  ZoneList<RegExpTree*>* alternatives = this->alternatives();
-  int length = alternatives->length();
-
-  int write_posn = 0;
-  int i = 0;
-  while (i < length) {
-    RegExpTree* alternative = alternatives->at(i);
-    if (!alternative->IsAtom()) {
-      alternatives->at(write_posn++) = alternatives->at(i);
-      i++;
-      continue;
-    }
-    RegExpAtom* atom = alternative->AsAtom();
-    if (atom->length() != 1) {
-      alternatives->at(write_posn++) = alternatives->at(i);
-      i++;
-      continue;
-    }
-    int first_in_run = i;
-    i++;
-    while (i < length) {
-      alternative = alternatives->at(i);
-      if (!alternative->IsAtom()) break;
-      atom = alternative->AsAtom();
-      if (atom->length() != 1) break;
-      i++;
-    }
-    if (i > first_in_run + 1) {
-      // Found non-trivial run of single-character alternatives.
-      int run_length = i - first_in_run;
-      ZoneList<CharacterRange>* ranges =
-          new (zone) ZoneList<CharacterRange>(2, zone);
-      for (int j = 0; j < run_length; j++) {
-        RegExpAtom* old_atom = alternatives->at(j + first_in_run)->AsAtom();
-        DCHECK_EQ(old_atom->length(), 1);
-        ranges->Add(CharacterRange::Singleton(old_atom->data().at(0)), zone);
-      }
-      alternatives->at(write_posn++) =
-          new (zone) RegExpCharacterClass(ranges, false);
-    } else {
-      // Just copy any trivial alternatives.
-      for (int j = first_in_run; j < i; j++) {
-        alternatives->at(write_posn++) = alternatives->at(j);
-      }
-    }
-  }
-  alternatives->Rewind(write_posn);  // Trim end of array.
-}
-
-
 RegExpNode* RegExpDisjunction::ToNode(RegExpCompiler* compiler,
                                       RegExpNode* on_success) {
   ZoneList<RegExpTree*>* alternatives = this->alternatives();
-
-  if (alternatives->length() > 2) {
-    bool found_consecutive_atoms = SortConsecutiveAtoms(compiler);
-    if (found_consecutive_atoms) RationalizeConsecutiveAtoms(compiler);
-    FixSingleCharacterDisjunctions(compiler);
-    if (alternatives->length() == 1) {
-      return alternatives->at(0)->ToNode(compiler, on_success);
-    }
-  }
-
   int length = alternatives->length();
-
   ChoiceNode* result =
       new(compiler->zone()) ChoiceNode(length, compiler->zone());
   for (int i = 0; i < length; i++) {