Re: [PR] [branch_9_9] Reflow computeCommonPrefixLengthAndBuildHistogram to avoid crash [lucene]

["jpountz (via GitHub)" <gi...@apache.org>]

jpountz commented on code in PR #12903:
URL: https://github.com/apache/lucene/pull/12903#discussion_r1421819068


##########
lucene/core/src/java/org/apache/lucene/util/MSBRadixSorter.java:
##########
@@ -214,6 +214,12 @@ protected int getBucket(int i, int k) {
    * @see #buildHistogram
    */
   private int computeCommonPrefixLengthAndBuildHistogram(int from, int to, int k, int[] histogram) {
+    int commonPrefixLength = computeInitialCommonPrefixLength(from, k);
+    return computeCommonPrefixLengthAndBuildHistogramPart1(
+        from, to, k, histogram, commonPrefixLength);
+  }
+
+  private int computeInitialCommonPrefixLength(int from, int k) {

Review Comment:
   Can you add a comment here and in other places that you touched, explaining that this works around a C2 compiler bug?



##########
lucene/core/src/test/org/apache/lucene/util/bkd/TestDocIdsWriter.java:
##########
@@ -150,4 +154,18 @@ public Relation compare(byte[] minPackedValue, byte[] maxPackedValue) {
     }
     dir.deleteFile("tmp");
   }
+
+  // This simple test tickles a JVM JIT crash on JDK's less than 21.0.1
+  // Needs to be run with C2, so with the environment variable `CI` set
+  public void testCrash() throws IOException {
+    for (int i = 0; i < 100; 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)));
+        }
+      }
+    }
+  }

Review Comment:
   How long does this test take? If it's multiple seconds, should it only run nightly?



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