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Unified Diff: src/jsregexp.cc

Issue 1174713002: Reland of 'Optimize trivial regexp disjunctions' CL 1176453002 (Closed) Base URL: https://chromium.googlesource.com/v8/v8.git@master
Patch Set: Fix for the out-of-bounds sort that caused the revert Created 5 years, 6 months ago
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Index: src/jsregexp.cc
diff --git a/src/jsregexp.cc b/src/jsregexp.cc
index b410d47b3d1fd41d93dd5d26cf8386050375745e..e284e8cb15f3233eee2533bc9efda8b6735bd1e3 100644
--- a/src/jsregexp.cc
+++ b/src/jsregexp.cc
@@ -4817,10 +4817,200 @@ RegExpNode* RegExpCharacterClass::ToNode(RegExpCompiler* compiler,
}
+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;
Erik Corry Chromium.org 2015/06/09 20:27:11 This is the fix.
+ 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++) {
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