[GR-52906] Re-enable fast-forward past empty mandatory iterations in JS.

regex/ci/ci.jsonnet

@@ -33,8 +33,9 @@
       ["git", "clone", ["mx", "urlrewrite", "https://github.com/graalvm/js-tests.git"], "../../js-tests"],
       ["mx", "-p", "../vm", "--dynamicimports", "/graal-js,js-tests", "checkout-downstream", "graal-js", "js-tests"],
       # run downstream gate from js-tests suite.
-      ["mx", "-p", "../../js-tests", "sversions"],
-      ["mx", "-p", "../../js-tests", "gate", "--no-warning-as-error", "--all-suites", "--tags", "build,Test262-default,TestV8-default,regex"],
+      ["cd", "../../js-tests"],
+      ["mx", "sversions"],
+      ["mx", "gate", "--no-warning-as-error", "--all-suites", "--tags", "build,Test262-default,TestV8-default,regex"],
     ],
     targets: ["gate"],
   },

regex/src/com.oracle.truffle.regex.test/src/com/oracle/truffle/regex/tregex/test/JsTests.java

@@ -289,4 +289,17 @@ public void innerLiteralSurrogates() {
         test("\\udf06", "u", "\uD834\uDF06", 0, false);
         test("x?\\udf06", "u", "\uD834\uDF06", 0, false);
     }
+
+    @Test
+    public void gr52906() {
+        // Original test case
+        test("\\b(((.*?)){67108860})\\b|(?=(?=(?!.).\\b(\\d))){0,4}", "yi", "L1O\n\n\n11\n  \n\n11\n  \uD091  1aa\uFCDB=\n ", 0, true, 0, 0, 0, 0, 0, 0, 0, 0, -1, -1);
+        // Minimized version
+        test("(.*?){67108863}", "", "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx", 0, true, 0, 0, 0, 0);
+
+        // Linked issue
+        test("(?=(?=(\\W)\u008e+|\\uC47A|(\\s)))+?|((((?:(\\\u0015)))+?))|(?:\\r|[^]+?[^])|\\3{3,}", "gyim", "", 0, true, 0, 0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1);
+        // Minimized version
+        test("()\\1{3,}", "", "", 0, true, 0, 0, 0, 0);
+    }
 }

regex/src/com.oracle.truffle.regex/src/com/oracle/truffle/regex/tregex/nfa/PureNFATransition.java

@@ -49,6 +49,8 @@
 import com.oracle.truffle.regex.tregex.util.json.Json;
 import com.oracle.truffle.regex.tregex.util.json.JsonValue;
 
+import java.util.Arrays;
+
 /**
  * Represents a transition of a {@link PureNFA}.
  */
@@ -122,6 +124,7 @@ public JsonValue toJson(RegexAST ast) {
                         Json.prop("source", source.getId()),
                         Json.prop("target", target.getId()),
                         Json.prop("groupBoundaries", groupBoundaries),
-                        Json.prop("sourceSections", groupBoundaries.indexUpdateSourceSectionsToJson(ast)));
+                        Json.prop("sourceSections", groupBoundaries.indexUpdateSourceSectionsToJson(ast)),
+                        Json.prop("quantifierGuards", Arrays.stream(quantifierGuards).map(QuantifierGuard::toJson)));
     }
 }

regex/src/com.oracle.truffle.regex/src/com/oracle/truffle/regex/tregex/nfa/QuantifierGuard.java

@@ -44,6 +44,8 @@
 import com.oracle.truffle.regex.tregex.parser.Token.Quantifier;
 import com.oracle.truffle.regex.tregex.parser.ast.ConditionalBackReferenceGroup;
 import com.oracle.truffle.regex.tregex.parser.flavors.RegexFlavor;
+import com.oracle.truffle.regex.tregex.util.json.Json;
+import com.oracle.truffle.regex.tregex.util.json.JsonValue;
 
 import java.util.Objects;
 
@@ -228,4 +230,9 @@ public String toString() {
             return kind + " " + index;
         }
     }
+
+    @TruffleBoundary
+    public JsonValue toJson() {
+        return Json.val(toString());
+    }
 }

regex/src/com.oracle.truffle.regex/src/com/oracle/truffle/regex/tregex/nodes/nfa/TRegexBacktrackingNFAExecutorNode.java

@@ -89,12 +89,13 @@ public final class TRegexBacktrackingNFAExecutorNode extends TRegexBacktrackerSu
     private static final int FLAG_BACKREF_WITH_NULL_TARGET_FAILS = 1 << 2;
     private static final int FLAG_MONITOR_CAPTURE_GROUPS_IN_EMPTY_CHECK = 1 << 3;
     private static final int FLAG_TRANSITION_MATCHES_STEP_BY_STEP = 1 << 4;
-    private static final int FLAG_TRACK_LAST_GROUP = 1 << 5;
-    private static final int FLAG_RETURNS_FIRST_GROUP = 1 << 6;
-    private static final int FLAG_MUST_ADVANCE = 1 << 7;
-    private static final int FLAG_LONE_SURROGATES = 1 << 8;
-    private static final int FLAG_LOOPBACK_INITIAL_STATE = 1 << 9;
-    private static final int FLAG_USE_MERGE_EXPLODE = 1 << 10;
+    private static final int FLAG_EMPTY_CHECKS_ON_MANDATORY_LOOP_ITERATIONS = 1 << 5;
+    private static final int FLAG_TRACK_LAST_GROUP = 1 << 6;
+    private static final int FLAG_RETURNS_FIRST_GROUP = 1 << 7;
+    private static final int FLAG_MUST_ADVANCE = 1 << 8;
+    private static final int FLAG_LONE_SURROGATES = 1 << 9;
+    private static final int FLAG_LOOPBACK_INITIAL_STATE = 1 << 10;
+    private static final int FLAG_USE_MERGE_EXPLODE = 1 << 11;
     private static final int FLAG_RECURSIVE_BACK_REFERENCES = 1 << 12;
 
     private final PureNFA nfa;
@@ -199,6 +200,7 @@ private static int createFlags(RegexAST ast, PureNFA nfa, boolean mustAdvance, R
         flags = setFlag(flags, FLAG_BACKREF_WITH_NULL_TARGET_FAILS, ast.getOptions().getFlavor().backreferencesToUnmatchedGroupsFail());
         flags = setFlag(flags, FLAG_MONITOR_CAPTURE_GROUPS_IN_EMPTY_CHECK, ast.getOptions().getFlavor().emptyChecksMonitorCaptureGroups());
         flags = setFlag(flags, FLAG_TRANSITION_MATCHES_STEP_BY_STEP, ast.getOptions().getFlavor().matchesTransitionsStepByStep());
+        flags = setFlag(flags, FLAG_EMPTY_CHECKS_ON_MANDATORY_LOOP_ITERATIONS, ast.getOptions().getFlavor().emptyChecksOnMandatoryLoopIterations());
         flags = setFlag(flags, FLAG_TRACK_LAST_GROUP, ast.getOptions().getFlavor().usesLastGroupResultField());
         flags = setFlag(flags, FLAG_RETURNS_FIRST_GROUP, !isFlagSet(flags, FLAG_FORWARD) && ast.getOptions().getFlavor().lookBehindsRunLeftToRight());
         flags = setFlag(flags, FLAG_MUST_ADVANCE, mustAdvance);
@@ -250,6 +252,10 @@ public boolean isTransitionMatchesStepByStep() {
         return isFlagSet(FLAG_TRANSITION_MATCHES_STEP_BY_STEP);
     }
 
+    public boolean isEmptyChecksOnMandatoryLoopIterations() {
+        return isFlagSet(FLAG_EMPTY_CHECKS_ON_MANDATORY_LOOP_ITERATIONS);
+    }
+
     public boolean isTrackLastGroup() {
         return isFlagSet(FLAG_TRACK_LAST_GROUP);
     }
@@ -749,7 +755,10 @@ protected boolean transitionMatches(VirtualFrame frame, TRegexBacktrackingNFAExe
                 case exitZeroWidth:
                     if (locals.getZeroWidthQuantifierGuardIndex(q) == index &&
                                     (!isMonitorCaptureGroupsInEmptyCheck() || locals.isResultUnmodifiedByZeroWidthQuantifier(q)) &&
-                                    (!q.hasIndex() || locals.getQuantifierCount(q) > q.getMin())) {
+                                    // In JS, we allow this guard to pass if we are still in the
+                                    // optional part of the quantifier. This allows JS to fast-
+                                    // forward past all the empty mandatory iterations.
+                                    (isEmptyChecksOnMandatoryLoopIterations() || !q.hasIndex() || locals.getQuantifierCount(q) > q.getMin())) {
                         return false;
                     }
                     break;
@@ -827,6 +836,29 @@ protected void updateState(TRegexBacktrackingNFAExecutorLocals locals, PureNFATr
                     locals.setZeroWidthQuantifierGuardIndex(q);
                     locals.setZeroWidthQuantifierResults(q);
                     break;
+                case exitZeroWidth:
+                    boolean emptyCheckFailed = locals.getZeroWidthQuantifierGuardIndex(q) == index &&
+                                    (!isMonitorCaptureGroupsInEmptyCheck() || locals.isResultUnmodifiedByZeroWidthQuantifier(q));
+                    boolean advancePastOptionalIterations = !isEmptyChecksOnMandatoryLoopIterations() && q.hasIndex() && locals.getQuantifierCount(q) < q.getMin();
+                    if (emptyCheckFailed && advancePastOptionalIterations && !transition.hasCaretGuard() && !transition.hasDollarGuard()) {
+                        // We advance the counter to min - 1 to skip past all but one mandatory
+                        // iteration. We do not skip the last mandatory iteration and set the
+                        // counter to min, because of the way JavaScript regexes are executed. The
+                        // JavaScript flavor does not set matchesTransitionStepByStep and therefore
+                        // all guards are tested against the same original state. In the case of the
+                        // last mandatory iteration, we would like it to be possible to match the
+                        // exitZeroWidth guard followed by the exit guard, so that it is possible to
+                        // hit the exact minimum number of iterations. However, this relies on first
+                        // updating the state with exitZeroWidth and then testing this new state
+                        // with the exit guard. This would mean having to enable
+                        // matchesTransitionStepByStep for JavaScript and implementing this logic in
+                        // tryUpdateState instead, which would lead to degraded performance for JS
+                        // regexps. Instead, we choose to advance the counter to just before the
+                        // last mandatory iteration so that this fast-forwarding behavior does not
+                        // coincide with an exit guard that should pass.
+                        locals.setQuantifierCount(q, q.getMin() - 1);
+                    }
+                    break;
                 default:
                     break;
             }