Reflow computeCommonPrefixLengthAndBuildHistogram to avoid crash

gradle/testing/randomization/policies/tests.policy

@@ -60,6 +60,9 @@ grant {
   permission java.lang.RuntimePermission "getFileStoreAttributes";
   permission java.lang.RuntimePermission "writeFileDescriptor";
 
+  // needed to check if C2 (implied by the presence of the CI env) is enabled
+  permission java.lang.RuntimePermission "getenv.CI";
+
   // TestLockFactoriesMultiJVM opens a random port on 127.0.0.1 (port 0 = ephemeral port range):
   permission java.net.SocketPermission "127.0.0.1:0", "accept,listen,resolve";
 

lucene/core/src/java/org/apache/lucene/util/MSBRadixSorter.java

@@ -213,7 +213,16 @@ protected int getBucket(int i, int k) {
    *
    * @see #buildHistogram
    */
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  // See https://github.com/apache/lucene/issues/12898
   private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k, int[] histogram) {
+    int commonPrefixLength = computeInitialCommonPrefixLength(from, k);
+    return computeCommonPrefixLengthAndBuildHistogramPart1(
+        from, to, k, histogram, commonPrefixLength);
+  }
+
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeInitialCommonPrefixLength(int from, int k) {
     final int[] commonPrefix = this.commonPrefix;
     int commonPrefixLength = Math.min(commonPrefix.length, maxLength - k);
     for (int j = 0; j < commonPrefixLength; ++j) {
@@ -224,7 +233,13 @@ private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k,
         break;
       }
     }
+    return commonPrefixLength;
+  }
 
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeCommonPrefixLengthAndBuildHistogramPart1(
+      int from, int to, int k, int[] histogram, int commonPrefixLength) {
+    final int[] commonPrefix = this.commonPrefix;
     int i;
     outer:
     for (i = from + 1; i < to; ++i) {
@@ -239,7 +254,13 @@ private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k,
         }
       }
     }
+    return computeCommonPrefixLengthAndBuildHistogramPart2(
+        from, to, k, histogram, commonPrefixLength, i);
+  }
 
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeCommonPrefixLengthAndBuildHistogramPart2(
+      int from, int to, int k, int[] histogram, int commonPrefixLength, int i) {
     if (i < to) {
       // the loop got broken because there is no common prefix
       assert commonPrefixLength == 0;

lucene/core/src/java/org/apache/lucene/util/RadixSelector.java

@@ -198,7 +198,16 @@ private int getBucket(int i, int k) {
    *
    * @see #buildHistogram
    */
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  // See https://github.com/apache/lucene/issues/12898
   private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k, int[] histogram) {
+    int commonPrefixLength = computeInitialCommonPrefixLength(from, k);
+    return computeCommonPrefixLengthAndBuildHistogramPart1(
+        from, to, k, histogram, commonPrefixLength);
+  }
+
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeInitialCommonPrefixLength(int from, int k) {
     final int[] commonPrefix = this.commonPrefix;
     int commonPrefixLength = Math.min(commonPrefix.length, maxLength - k);
     for (int j = 0; j < commonPrefixLength; ++j) {
@@ -209,7 +218,13 @@ private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k,
         break;
       }
     }
+    return commonPrefixLength;
+  }
 
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeCommonPrefixLengthAndBuildHistogramPart1(
+      int from, int to, int k, int[] histogram, int commonPrefixLength) {
+    final int[] commonPrefix = this.commonPrefix;
     int i;
     outer:
     for (i = from + 1; i < to; ++i) {
@@ -226,7 +241,13 @@ private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k,
         }
       }
     }
+    return computeCommonPrefixLengthAndBuildHistogramPart2(
+        from, to, k, histogram, commonPrefixLength, i);
+  }
 
+  // This method, and its namesakes, have been manually split to work around a JVM crash.
+  private int computeCommonPrefixLengthAndBuildHistogramPart2(
+      int from, int to, int k, int[] histogram, int commonPrefixLength, int i) {
     if (i < to) {
       // the loop got broken because there is no common prefix
       assert commonPrefixLength == 0;

lucene/core/src/test/org/apache/lucene/util/bkd/TestDocIdsWriter.java

@@ -17,8 +17,14 @@
 package org.apache.lucene.util.bkd;
 
 import java.io.IOException;
+import java.security.AccessController;
+import java.security.PrivilegedAction;
 import java.util.Arrays;
+import java.util.List;
 import java.util.Set;
+import org.apache.lucene.document.IntPoint;
+import org.apache.lucene.document.SortedNumericDocValuesField;
+import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.PointValues.IntersectVisitor;
 import org.apache.lucene.index.PointValues.Relation;
 import org.apache.lucene.store.Directory;
@@ -28,6 +34,7 @@
 import org.apache.lucene.tests.util.LuceneTestCase;
 import org.apache.lucene.tests.util.TestUtil;
 import org.apache.lucene.util.CollectionUtil;
+import org.apache.lucene.util.SuppressForbidden;
 
 public class TestDocIdsWriter extends LuceneTestCase {
 
@@ -150,4 +157,28 @@ public Relation compare(byte[] minPackedValue, byte[] maxPackedValue) {
     }
     dir.deleteFile("tmp");
   }
+
+  // This simple test tickles a JVM C2 JIT crash on JDK's less than 21.0.1
+  // Crashes only when run with C2, so with the environment variable `CI` set
+  // Regardless of whether C2 is enabled or not, the test should never fail.
+  public void testCrash() throws IOException {
+    assumeTrue("Requires C2, which is only enabled when CI env is set", getCIEnv() != null);
+    int itrs = atLeast(100);
+    for (int i = 0; i < itrs; i++) {
+      try (Directory dir = newDirectory();
+          IndexWriter iw = new IndexWriter(dir, newIndexWriterConfig(null))) {
+        for (int d = 0; d < 20_000; d++) {
+          iw.addDocument(
+              List.of(new IntPoint("foo", 0), new SortedNumericDocValuesField("bar", 0)));
+        }
+      }
+    }
+  }
+
+  @SuppressForbidden(reason = "needed to check if C2 is enabled")
+  @SuppressWarnings("removal")
+  private static String getCIEnv() {
+    PrivilegedAction<String> pa = () -> System.getenv("CI");
+    return AccessController.doPrivileged(pa);
+  }
 }