Optimize decoding blocks of postings using the vector API. (#13636)

Our postings use a layout that helps take advantage of Java's
auto-vectorization to be reasonably fast to decode. But we can make it a bit
faster by vectorizing directly from the MemorySegment instead of first
copying data into a long[].

This approach only works when the `Directory` uses `MemorySegmentIndexInput`
under the hood, ie. `MMapDirectory` on JDK 21+.

Co-authored-by: Uwe Schindler <uschindler@apache.org>

lucene/CHANGES.txt

@@ -352,6 +352,9 @@ Optimizations
 
 * GITHUB#13581: OnHeapHnswGraph no longer allocates a lock for every graph node (Mike Sokolov)
 
+* GITHUB#13636: Optimizations to the decoding logic of blocks of postings.
+  (Adrien Grand, Uwe Schindler)
+
 Changes in runtime behavior
 ---------------------
 

lucene/benchmark-jmh/src/java/org/apache/lucene/benchmark/jmh/PostingIndexInputBenchmark.java

@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.benchmark.jmh;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+import org.apache.lucene.codecs.lucene912.ForUtil;
+import org.apache.lucene.codecs.lucene912.PostingIndexInput;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.store.MMapDirectory;
+import org.apache.lucene.util.IOUtils;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@BenchmarkMode(Mode.Throughput)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@State(Scope.Benchmark)
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 5, time = 1)
+@Fork(
+    value = 3,
+    jvmArgsAppend = {"-Xmx1g", "-Xms1g", "-XX:+AlwaysPreTouch"})
+public class PostingIndexInputBenchmark {
+
+  private Path path;
+  private Directory dir;
+  private IndexInput in;
+  private PostingIndexInput postingIn;
+  private final ForUtil forUtil = new ForUtil();
+  private final long[] values = new long[128];
+
+  @Param({"5", "6", "7", "8", "9", "10"})
+  public int bpv;
+
+  @Setup(Level.Trial)
+  public void setup() throws Exception {
+    path = Files.createTempDirectory("forUtil");
+    dir = MMapDirectory.open(path);
+    try (IndexOutput out = dir.createOutput("docs", IOContext.DEFAULT)) {
+      Random r = new Random(0);
+      // Write enough random data to not reach EOF while decoding
+      for (int i = 0; i < 100; ++i) {
+        out.writeLong(r.nextLong());
+      }
+    }
+    in = dir.openInput("docs", IOContext.DEFAULT);
+    postingIn = new PostingIndexInput(in, forUtil);
+  }
+
+  @TearDown(Level.Trial)
+  public void tearDown() throws Exception {
+    if (dir != null) {
+      dir.deleteFile("docs");
+    }
+    IOUtils.close(in, dir);
+    in = null;
+    dir = null;
+    Files.deleteIfExists(path);
+  }
+
+  @Benchmark
+  public void decode(Blackhole bh) throws IOException {
+    in.seek(3); // random unaligned offset
+    postingIn.decode(bpv, values);
+    bh.consume(values);
+  }
+
+  @Benchmark
+  public void decodeAndPrefixSum(Blackhole bh) throws IOException {
+    in.seek(3); // random unaligned offset
+    postingIn.decodeAndPrefixSum(bpv, 100, values);
+    bh.consume(values);
+  }
+}

lucene/core/src/generated/checksums/generateForUtil.json

@@ -1,4 +1,4 @@
 {
-    "lucene/core/src/java/org/apache/lucene/codecs/lucene912/ForUtil.java": "5ff856e80cab30f9e5704aa89f3197f017d07624",
+    "lucene/core/src/java/org/apache/lucene/codecs/lucene912/ForUtil.java": "cc7d40997e2d6500b79c19ff47461ed6e89d2268",
-    "lucene/core/src/java/org/apache/lucene/codecs/lucene912/gen_ForUtil.py": "3ccf92b3ddbff6340a13e8a55090bfb900dc7be2"
+    "lucene/core/src/java/org/apache/lucene/codecs/lucene912/gen_ForUtil.py": "ba029f2e374e66c6cf315b2c93f4efa6944dfbb8"
 }

lucene/core/src/java/org/apache/lucene/codecs/lucene912/ForDeltaUtil.java

@@ -22,7 +22,7 @@ import org.apache.lucene.store.DataOutput;
 import org.apache.lucene.util.packed.PackedInts;
 
 /** Utility class to encode/decode increasing sequences of 128 integers. */
-public class ForDeltaUtil {
+final class ForDeltaUtil {
 
   // IDENTITY_PLUS_ONE[i] == i+1
   private static final long[] IDENTITY_PLUS_ONE = new long[ForUtil.BLOCK_SIZE];
@@ -67,12 +67,12 @@ public class ForDeltaUtil {
   }
 
   /** Decode deltas, compute the prefix sum and add {@code base} to all decoded longs. */
-  void decodeAndPrefixSum(DataInput in, long base, long[] longs) throws IOException {
+  void decodeAndPrefixSum(PostingIndexInput in, long base, long[] longs) throws IOException {
-    final int bitsPerValue = Byte.toUnsignedInt(in.readByte());
+    final int bitsPerValue = Byte.toUnsignedInt(in.in.readByte());
     if (bitsPerValue == 0) {
       prefixSumOfOnes(longs, base);
     } else {
-      forUtil.decodeAndPrefixSum(bitsPerValue, in, base, longs);
+      in.decodeAndPrefixSum(bitsPerValue, base, longs);
     }
   }
 

lucene/core/src/java/org/apache/lucene/codecs/lucene912/ForUtil.java

@@ -19,17 +19,18 @@
 package org.apache.lucene.codecs.lucene912;
 
 import java.io.IOException;
-import org.apache.lucene.store.DataInput;
+import org.apache.lucene.internal.vectorization.PostingDecodingUtil;
 import org.apache.lucene.store.DataOutput;
+import org.apache.lucene.store.IndexInput;
 
-// Inspired from https://fulmicoton.com/posts/bitpacking/
+/**
-// Encodes multiple integers in a long to get SIMD-like speedups.
+ * Inspired from https://fulmicoton.com/posts/bitpacking/ Encodes multiple integers in a long to get
-// If bitsPerValue <= 8 then we pack 8 ints per long
+ * SIMD-like speedups. If bitsPerValue &lt;= 8 then we pack 8 ints per long else if bitsPerValue
-// else if bitsPerValue <= 16 we pack 4 ints per long
+ * &lt;= 16 we pack 4 ints per long else we pack 2 ints per long
-// else we pack 2 ints per long
+ */
-final class ForUtil {
+public final class ForUtil {
 
-  static final int BLOCK_SIZE = 128;
+  public static final int BLOCK_SIZE = 128;
   private static final int BLOCK_SIZE_LOG2 = 7;
 
   private static long expandMask32(long mask32) {
@@ -300,13 +301,14 @@ final class ForUtil {
     return bitsPerValue << (BLOCK_SIZE_LOG2 - 3);
   }
 
-  private static void decodeSlow(int bitsPerValue, DataInput in, long[] tmp, long[] longs)
+  private static void decodeSlow(
+      int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
       throws IOException {
     final int numLongs = bitsPerValue << 1;
-    in.readLongs(tmp, 0, numLongs);
     final long mask = MASKS32[bitsPerValue];
-    int longsIdx = 0;
+    pdu.splitLongs(numLongs, longs, 32 - bitsPerValue, mask, tmp, 0, -1L);
-    int shift = 32 - bitsPerValue;
+    int longsIdx = numLongs;
+    int shift = 32 - 2 * bitsPerValue;
     for (; shift >= 0; shift -= bitsPerValue) {
       shiftLongs(tmp, numLongs, longs, longsIdx, shift, mask);
       longsIdx += numLongs;
@@ -342,6 +344,13 @@ final class ForUtil {
     }
   }
 
+  /** Likewise, but for a simple mask. */
+  private static void maskLongs(long[] a, int count, long[] b, int bi, long mask) {
+    for (int i = 0; i < count; ++i) {
+      b[bi + i] = a[i] & mask;
+    }
+  }
+
   private static final long[] MASKS8 = new long[8];
   private static final long[] MASKS16 = new long[16];
   private static final long[] MASKS32 = new long[32];
@@ -406,279 +415,280 @@ final class ForUtil {
   private static final long MASK32_24 = MASKS32[24];
 
   /** Decode 128 integers into {@code longs}. */
-  void decode(int bitsPerValue, DataInput in, long[] longs) throws IOException {
+  void decode(int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long[] longs)
+      throws IOException {
     switch (bitsPerValue) {
       case 1:
-        decode1(in, tmp, longs);
+        decode1(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 2:
-        decode2(in, tmp, longs);
+        decode2(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 3:
-        decode3(in, tmp, longs);
+        decode3(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 4:
-        decode4(in, tmp, longs);
+        decode4(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 5:
-        decode5(in, tmp, longs);
+        decode5(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 6:
-        decode6(in, tmp, longs);
+        decode6(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 7:
-        decode7(in, tmp, longs);
+        decode7(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 8:
-        decode8(in, tmp, longs);
+        decode8(in, pdu, tmp, longs);
         expand8(longs);
         break;
       case 9:
-        decode9(in, tmp, longs);
+        decode9(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 10:
-        decode10(in, tmp, longs);
+        decode10(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 11:
-        decode11(in, tmp, longs);
+        decode11(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 12:
-        decode12(in, tmp, longs);
+        decode12(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 13:
-        decode13(in, tmp, longs);
+        decode13(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 14:
-        decode14(in, tmp, longs);
+        decode14(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 15:
-        decode15(in, tmp, longs);
+        decode15(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 16:
-        decode16(in, tmp, longs);
+        decode16(in, pdu, tmp, longs);
         expand16(longs);
         break;
       case 17:
-        decode17(in, tmp, longs);
+        decode17(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 18:
-        decode18(in, tmp, longs);
+        decode18(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 19:
-        decode19(in, tmp, longs);
+        decode19(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 20:
-        decode20(in, tmp, longs);
+        decode20(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 21:
-        decode21(in, tmp, longs);
+        decode21(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 22:
-        decode22(in, tmp, longs);
+        decode22(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 23:
-        decode23(in, tmp, longs);
+        decode23(in, pdu, tmp, longs);
         expand32(longs);
         break;
       case 24:
-        decode24(in, tmp, longs);
+        decode24(in, pdu, tmp, longs);
         expand32(longs);
         break;
       default:
-        decodeSlow(bitsPerValue, in, tmp, longs);
+        decodeSlow(bitsPerValue, in, pdu, tmp, longs);
         expand32(longs);
         break;
     }
   }
 
   /** Delta-decode 128 integers into {@code longs}. */
-  void decodeAndPrefixSum(int bitsPerValue, DataInput in, long base, long[] longs)
+  void decodeAndPrefixSum(
+      int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long base, long[] longs)
       throws IOException {
     switch (bitsPerValue) {
       case 1:
-        decode1(in, tmp, longs);
+        decode1(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 2:
-        decode2(in, tmp, longs);
+        decode2(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 3:
-        decode3(in, tmp, longs);
+        decode3(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 4:
-        decode4(in, tmp, longs);
+        decode4(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 5:
-        decode5(in, tmp, longs);
+        decode5(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 6:
-        decode6(in, tmp, longs);
+        decode6(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 7:
-        decode7(in, tmp, longs);
+        decode7(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 8:
-        decode8(in, tmp, longs);
+        decode8(in, pdu, tmp, longs);
         prefixSum8(longs, base);
         break;
       case 9:
-        decode9(in, tmp, longs);
+        decode9(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 10:
-        decode10(in, tmp, longs);
+        decode10(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 11:
-        decode11(in, tmp, longs);
+        decode11(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 12:
-        decode12(in, tmp, longs);
+        decode12(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 13:
-        decode13(in, tmp, longs);
+        decode13(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 14:
-        decode14(in, tmp, longs);
+        decode14(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 15:
-        decode15(in, tmp, longs);
+        decode15(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 16:
-        decode16(in, tmp, longs);
+        decode16(in, pdu, tmp, longs);
         prefixSum16(longs, base);
         break;
       case 17:
-        decode17(in, tmp, longs);
+        decode17(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 18:
-        decode18(in, tmp, longs);
+        decode18(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 19:
-        decode19(in, tmp, longs);
+        decode19(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 20:
-        decode20(in, tmp, longs);
+        decode20(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 21:
-        decode21(in, tmp, longs);
+        decode21(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 22:
-        decode22(in, tmp, longs);
+        decode22(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 23:
-        decode23(in, tmp, longs);
+        decode23(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       case 24:
-        decode24(in, tmp, longs);
+        decode24(in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
       default:
-        decodeSlow(bitsPerValue, in, tmp, longs);
+        decodeSlow(bitsPerValue, in, pdu, tmp, longs);
         prefixSum32(longs, base);
         break;
     }
   }
 
-  private static void decode1(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode1(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 2);
+      throws IOException {
-    shiftLongs(tmp, 2, longs, 0, 7, MASK8_1);
+    pdu.splitLongs(2, longs, 7, MASK8_1, tmp, 0, MASK8_7);
     shiftLongs(tmp, 2, longs, 2, 6, MASK8_1);
     shiftLongs(tmp, 2, longs, 4, 5, MASK8_1);
     shiftLongs(tmp, 2, longs, 6, 4, MASK8_1);
     shiftLongs(tmp, 2, longs, 8, 3, MASK8_1);
     shiftLongs(tmp, 2, longs, 10, 2, MASK8_1);
     shiftLongs(tmp, 2, longs, 12, 1, MASK8_1);
-    shiftLongs(tmp, 2, longs, 14, 0, MASK8_1);
+    maskLongs(tmp, 2, longs, 14, MASK8_1);
   }
 
-  private static void decode2(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode2(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 4);
+      throws IOException {
-    shiftLongs(tmp, 4, longs, 0, 6, MASK8_2);
+    pdu.splitLongs(4, longs, 6, MASK8_2, tmp, 0, MASK8_6);
     shiftLongs(tmp, 4, longs, 4, 4, MASK8_2);
     shiftLongs(tmp, 4, longs, 8, 2, MASK8_2);
-    shiftLongs(tmp, 4, longs, 12, 0, MASK8_2);
+    maskLongs(tmp, 4, longs, 12, MASK8_2);
   }
 
-  private static void decode3(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode3(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 6);
+      throws IOException {
-    shiftLongs(tmp, 6, longs, 0, 5, MASK8_3);
+    pdu.splitLongs(6, longs, 5, MASK8_3, tmp, 0, MASK8_5);
     shiftLongs(tmp, 6, longs, 6, 2, MASK8_3);
+    maskLongs(tmp, 6, tmp, 0, MASK8_2);
     for (int iter = 0, tmpIdx = 0, longsIdx = 12; iter < 2; ++iter, tmpIdx += 3, longsIdx += 2) {
-      long l0 = (tmp[tmpIdx + 0] & MASK8_2) << 1;
+      long l0 = tmp[tmpIdx + 0] << 1;
       l0 |= (tmp[tmpIdx + 1] >>> 1) & MASK8_1;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK8_1) << 2;
-      l1 |= (tmp[tmpIdx + 2] & MASK8_2) << 0;
+      l1 |= tmp[tmpIdx + 2] << 0;
       longs[longsIdx + 1] = l1;
     }
   }
 
-  private static void decode4(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode4(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 8);
+      throws IOException {
-    shiftLongs(tmp, 8, longs, 0, 4, MASK8_4);
+    pdu.splitLongs(8, longs, 4, MASK8_4, longs, 8, MASK8_4);
-    shiftLongs(tmp, 8, longs, 8, 0, MASK8_4);
   }
 
-  private static void decode5(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode5(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 10);
+      throws IOException {
-    shiftLongs(tmp, 10, longs, 0, 3, MASK8_5);
+    pdu.splitLongs(10, longs, 3, MASK8_5, tmp, 0, MASK8_3);
     for (int iter = 0, tmpIdx = 0, longsIdx = 10; iter < 2; ++iter, tmpIdx += 5, longsIdx += 3) {
-      long l0 = (tmp[tmpIdx + 0] & MASK8_3) << 2;
+      long l0 = tmp[tmpIdx + 0] << 2;
       l0 |= (tmp[tmpIdx + 1] >>> 1) & MASK8_2;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK8_1) << 4;
-      l1 |= (tmp[tmpIdx + 2] & MASK8_3) << 1;
+      l1 |= tmp[tmpIdx + 2] << 1;
       l1 |= (tmp[tmpIdx + 3] >>> 2) & MASK8_1;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 3] & MASK8_2) << 3;
-      l2 |= (tmp[tmpIdx + 4] & MASK8_3) << 0;
+      l2 |= tmp[tmpIdx + 4] << 0;
       longs[longsIdx + 2] = l2;
     }
   }
 
-  private static void decode6(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode6(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 12);
+      throws IOException {
-    shiftLongs(tmp, 12, longs, 0, 2, MASK8_6);
+    pdu.splitLongs(12, longs, 2, MASK8_6, tmp, 0, MASK8_2);
-    shiftLongs(tmp, 12, tmp, 0, 0, MASK8_2);
     for (int iter = 0, tmpIdx = 0, longsIdx = 12; iter < 4; ++iter, tmpIdx += 3, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 4;
       l0 |= tmp[tmpIdx + 1] << 2;
@@ -687,10 +697,9 @@ final class ForUtil {
     }
   }
 
-  private static void decode7(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode7(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 14);
+      throws IOException {
-    shiftLongs(tmp, 14, longs, 0, 1, MASK8_7);
+    pdu.splitLongs(14, longs, 1, MASK8_7, tmp, 0, MASK8_1);
-    shiftLongs(tmp, 14, tmp, 0, 0, MASK8_1);
     for (int iter = 0, tmpIdx = 0, longsIdx = 14; iter < 2; ++iter, tmpIdx += 7, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 6;
       l0 |= tmp[tmpIdx + 1] << 5;
@@ -703,15 +712,16 @@ final class ForUtil {
     }
   }
 
-  private static void decode8(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode8(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
+      throws IOException {
     in.readLongs(longs, 0, 16);
   }
 
-  private static void decode9(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode9(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 18);
+      throws IOException {
-    shiftLongs(tmp, 18, longs, 0, 7, MASK16_9);
+    pdu.splitLongs(18, longs, 7, MASK16_9, tmp, 0, MASK16_7);
     for (int iter = 0, tmpIdx = 0, longsIdx = 18; iter < 2; ++iter, tmpIdx += 9, longsIdx += 7) {
-      long l0 = (tmp[tmpIdx + 0] & MASK16_7) << 2;
+      long l0 = tmp[tmpIdx + 0] << 2;
       l0 |= (tmp[tmpIdx + 1] >>> 5) & MASK16_2;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK16_5) << 4;
@@ -721,7 +731,7 @@ final class ForUtil {
       l2 |= (tmp[tmpIdx + 3] >>> 1) & MASK16_6;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 3] & MASK16_1) << 8;
-      l3 |= (tmp[tmpIdx + 4] & MASK16_7) << 1;
+      l3 |= tmp[tmpIdx + 4] << 1;
       l3 |= (tmp[tmpIdx + 5] >>> 6) & MASK16_1;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 5] & MASK16_6) << 3;
@@ -731,59 +741,58 @@ final class ForUtil {
       l5 |= (tmp[tmpIdx + 7] >>> 2) & MASK16_5;
       longs[longsIdx + 5] = l5;
       long l6 = (tmp[tmpIdx + 7] & MASK16_2) << 7;
-      l6 |= (tmp[tmpIdx + 8] & MASK16_7) << 0;
+      l6 |= tmp[tmpIdx + 8] << 0;
       longs[longsIdx + 6] = l6;
     }
   }
 
-  private static void decode10(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode10(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 20);
+      throws IOException {
-    shiftLongs(tmp, 20, longs, 0, 6, MASK16_10);
+    pdu.splitLongs(20, longs, 6, MASK16_10, tmp, 0, MASK16_6);
     for (int iter = 0, tmpIdx = 0, longsIdx = 20; iter < 4; ++iter, tmpIdx += 5, longsIdx += 3) {
-      long l0 = (tmp[tmpIdx + 0] & MASK16_6) << 4;
+      long l0 = tmp[tmpIdx + 0] << 4;
       l0 |= (tmp[tmpIdx + 1] >>> 2) & MASK16_4;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK16_2) << 8;
-      l1 |= (tmp[tmpIdx + 2] & MASK16_6) << 2;
+      l1 |= tmp[tmpIdx + 2] << 2;
       l1 |= (tmp[tmpIdx + 3] >>> 4) & MASK16_2;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 3] & MASK16_4) << 6;
-      l2 |= (tmp[tmpIdx + 4] & MASK16_6) << 0;
+      l2 |= tmp[tmpIdx + 4] << 0;
       longs[longsIdx + 2] = l2;
     }
   }
 
-  private static void decode11(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode11(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 22);
+      throws IOException {
-    shiftLongs(tmp, 22, longs, 0, 5, MASK16_11);
+    pdu.splitLongs(22, longs, 5, MASK16_11, tmp, 0, MASK16_5);
     for (int iter = 0, tmpIdx = 0, longsIdx = 22; iter < 2; ++iter, tmpIdx += 11, longsIdx += 5) {
-      long l0 = (tmp[tmpIdx + 0] & MASK16_5) << 6;
+      long l0 = tmp[tmpIdx + 0] << 6;
-      l0 |= (tmp[tmpIdx + 1] & MASK16_5) << 1;
+      l0 |= tmp[tmpIdx + 1] << 1;
       l0 |= (tmp[tmpIdx + 2] >>> 4) & MASK16_1;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 2] & MASK16_4) << 7;
-      l1 |= (tmp[tmpIdx + 3] & MASK16_5) << 2;
+      l1 |= tmp[tmpIdx + 3] << 2;
       l1 |= (tmp[tmpIdx + 4] >>> 3) & MASK16_2;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 4] & MASK16_3) << 8;
-      l2 |= (tmp[tmpIdx + 5] & MASK16_5) << 3;
+      l2 |= tmp[tmpIdx + 5] << 3;
       l2 |= (tmp[tmpIdx + 6] >>> 2) & MASK16_3;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 6] & MASK16_2) << 9;
-      l3 |= (tmp[tmpIdx + 7] & MASK16_5) << 4;
+      l3 |= tmp[tmpIdx + 7] << 4;
       l3 |= (tmp[tmpIdx + 8] >>> 1) & MASK16_4;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 8] & MASK16_1) << 10;
-      l4 |= (tmp[tmpIdx + 9] & MASK16_5) << 5;
+      l4 |= tmp[tmpIdx + 9] << 5;
-      l4 |= (tmp[tmpIdx + 10] & MASK16_5) << 0;
+      l4 |= tmp[tmpIdx + 10] << 0;
       longs[longsIdx + 4] = l4;
     }
   }
 
-  private static void decode12(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode12(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 24);
+      throws IOException {
-    shiftLongs(tmp, 24, longs, 0, 4, MASK16_12);
+    pdu.splitLongs(24, longs, 4, MASK16_12, tmp, 0, MASK16_4);
-    shiftLongs(tmp, 24, tmp, 0, 0, MASK16_4);
     for (int iter = 0, tmpIdx = 0, longsIdx = 24; iter < 8; ++iter, tmpIdx += 3, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 8;
       l0 |= tmp[tmpIdx + 1] << 4;
@@ -792,35 +801,34 @@ final class ForUtil {
     }
   }
 
-  private static void decode13(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode13(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 26);
+      throws IOException {
-    shiftLongs(tmp, 26, longs, 0, 3, MASK16_13);
+    pdu.splitLongs(26, longs, 3, MASK16_13, tmp, 0, MASK16_3);
     for (int iter = 0, tmpIdx = 0, longsIdx = 26; iter < 2; ++iter, tmpIdx += 13, longsIdx += 3) {
-      long l0 = (tmp[tmpIdx + 0] & MASK16_3) << 10;
+      long l0 = tmp[tmpIdx + 0] << 10;
-      l0 |= (tmp[tmpIdx + 1] & MASK16_3) << 7;
+      l0 |= tmp[tmpIdx + 1] << 7;
-      l0 |= (tmp[tmpIdx + 2] & MASK16_3) << 4;
+      l0 |= tmp[tmpIdx + 2] << 4;
-      l0 |= (tmp[tmpIdx + 3] & MASK16_3) << 1;
+      l0 |= tmp[tmpIdx + 3] << 1;
       l0 |= (tmp[tmpIdx + 4] >>> 2) & MASK16_1;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 4] & MASK16_2) << 11;
-      l1 |= (tmp[tmpIdx + 5] & MASK16_3) << 8;
+      l1 |= tmp[tmpIdx + 5] << 8;
-      l1 |= (tmp[tmpIdx + 6] & MASK16_3) << 5;
+      l1 |= tmp[tmpIdx + 6] << 5;
-      l1 |= (tmp[tmpIdx + 7] & MASK16_3) << 2;
+      l1 |= tmp[tmpIdx + 7] << 2;
       l1 |= (tmp[tmpIdx + 8] >>> 1) & MASK16_2;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 8] & MASK16_1) << 12;
-      l2 |= (tmp[tmpIdx + 9] & MASK16_3) << 9;
+      l2 |= tmp[tmpIdx + 9] << 9;
-      l2 |= (tmp[tmpIdx + 10] & MASK16_3) << 6;
+      l2 |= tmp[tmpIdx + 10] << 6;
-      l2 |= (tmp[tmpIdx + 11] & MASK16_3) << 3;
+      l2 |= tmp[tmpIdx + 11] << 3;
-      l2 |= (tmp[tmpIdx + 12] & MASK16_3) << 0;
+      l2 |= tmp[tmpIdx + 12] << 0;
       longs[longsIdx + 2] = l2;
     }
   }
 
-  private static void decode14(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode14(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 28);
+      throws IOException {
-    shiftLongs(tmp, 28, longs, 0, 2, MASK16_14);
+    pdu.splitLongs(28, longs, 2, MASK16_14, tmp, 0, MASK16_2);
-    shiftLongs(tmp, 28, tmp, 0, 0, MASK16_2);
     for (int iter = 0, tmpIdx = 0, longsIdx = 28; iter < 4; ++iter, tmpIdx += 7, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 12;
       l0 |= tmp[tmpIdx + 1] << 10;
@@ -833,10 +841,9 @@ final class ForUtil {
     }
   }
 
-  private static void decode15(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode15(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 30);
+      throws IOException {
-    shiftLongs(tmp, 30, longs, 0, 1, MASK16_15);
+    pdu.splitLongs(30, longs, 1, MASK16_15, tmp, 0, MASK16_1);
-    shiftLongs(tmp, 30, tmp, 0, 0, MASK16_1);
     for (int iter = 0, tmpIdx = 0, longsIdx = 30; iter < 2; ++iter, tmpIdx += 15, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 14;
       l0 |= tmp[tmpIdx + 1] << 13;
@@ -857,15 +864,16 @@ final class ForUtil {
     }
   }
 
-  private static void decode16(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode16(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
+      throws IOException {
     in.readLongs(longs, 0, 32);
   }
 
-  private static void decode17(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode17(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 34);
+      throws IOException {
-    shiftLongs(tmp, 34, longs, 0, 15, MASK32_17);
+    pdu.splitLongs(34, longs, 15, MASK32_17, tmp, 0, MASK32_15);
     for (int iter = 0, tmpIdx = 0, longsIdx = 34; iter < 2; ++iter, tmpIdx += 17, longsIdx += 15) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_15) << 2;
+      long l0 = tmp[tmpIdx + 0] << 2;
       l0 |= (tmp[tmpIdx + 1] >>> 13) & MASK32_2;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK32_13) << 4;
@@ -887,7 +895,7 @@ final class ForUtil {
       l6 |= (tmp[tmpIdx + 7] >>> 1) & MASK32_14;
       longs[longsIdx + 6] = l6;
       long l7 = (tmp[tmpIdx + 7] & MASK32_1) << 16;
-      l7 |= (tmp[tmpIdx + 8] & MASK32_15) << 1;
+      l7 |= tmp[tmpIdx + 8] << 1;
       l7 |= (tmp[tmpIdx + 9] >>> 14) & MASK32_1;
       longs[longsIdx + 7] = l7;
       long l8 = (tmp[tmpIdx + 9] & MASK32_14) << 3;
@@ -909,16 +917,16 @@ final class ForUtil {
       l13 |= (tmp[tmpIdx + 15] >>> 2) & MASK32_13;
       longs[longsIdx + 13] = l13;
       long l14 = (tmp[tmpIdx + 15] & MASK32_2) << 15;
-      l14 |= (tmp[tmpIdx + 16] & MASK32_15) << 0;
+      l14 |= tmp[tmpIdx + 16] << 0;
       longs[longsIdx + 14] = l14;
     }
   }
 
-  private static void decode18(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode18(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 36);
+      throws IOException {
-    shiftLongs(tmp, 36, longs, 0, 14, MASK32_18);
+    pdu.splitLongs(36, longs, 14, MASK32_18, tmp, 0, MASK32_14);
     for (int iter = 0, tmpIdx = 0, longsIdx = 36; iter < 4; ++iter, tmpIdx += 9, longsIdx += 7) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_14) << 4;
+      long l0 = tmp[tmpIdx + 0] << 4;
       l0 |= (tmp[tmpIdx + 1] >>> 10) & MASK32_4;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK32_10) << 8;
@@ -928,7 +936,7 @@ final class ForUtil {
       l2 |= (tmp[tmpIdx + 3] >>> 2) & MASK32_12;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 3] & MASK32_2) << 16;
-      l3 |= (tmp[tmpIdx + 4] & MASK32_14) << 2;
+      l3 |= tmp[tmpIdx + 4] << 2;
       l3 |= (tmp[tmpIdx + 5] >>> 12) & MASK32_2;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 5] & MASK32_12) << 6;
@@ -938,206 +946,205 @@ final class ForUtil {
       l5 |= (tmp[tmpIdx + 7] >>> 4) & MASK32_10;
       longs[longsIdx + 5] = l5;
       long l6 = (tmp[tmpIdx + 7] & MASK32_4) << 14;
-      l6 |= (tmp[tmpIdx + 8] & MASK32_14) << 0;
+      l6 |= tmp[tmpIdx + 8] << 0;
       longs[longsIdx + 6] = l6;
     }
   }
 
-  private static void decode19(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode19(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 38);
+      throws IOException {
-    shiftLongs(tmp, 38, longs, 0, 13, MASK32_19);
+    pdu.splitLongs(38, longs, 13, MASK32_19, tmp, 0, MASK32_13);
     for (int iter = 0, tmpIdx = 0, longsIdx = 38; iter < 2; ++iter, tmpIdx += 19, longsIdx += 13) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_13) << 6;
+      long l0 = tmp[tmpIdx + 0] << 6;
       l0 |= (tmp[tmpIdx + 1] >>> 7) & MASK32_6;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK32_7) << 12;
       l1 |= (tmp[tmpIdx + 2] >>> 1) & MASK32_12;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 2] & MASK32_1) << 18;
-      l2 |= (tmp[tmpIdx + 3] & MASK32_13) << 5;
+      l2 |= tmp[tmpIdx + 3] << 5;
       l2 |= (tmp[tmpIdx + 4] >>> 8) & MASK32_5;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 4] & MASK32_8) << 11;
       l3 |= (tmp[tmpIdx + 5] >>> 2) & MASK32_11;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 5] & MASK32_2) << 17;
-      l4 |= (tmp[tmpIdx + 6] & MASK32_13) << 4;
+      l4 |= tmp[tmpIdx + 6] << 4;
       l4 |= (tmp[tmpIdx + 7] >>> 9) & MASK32_4;
       longs[longsIdx + 4] = l4;
       long l5 = (tmp[tmpIdx + 7] & MASK32_9) << 10;
       l5 |= (tmp[tmpIdx + 8] >>> 3) & MASK32_10;
       longs[longsIdx + 5] = l5;
       long l6 = (tmp[tmpIdx + 8] & MASK32_3) << 16;
-      l6 |= (tmp[tmpIdx + 9] & MASK32_13) << 3;
+      l6 |= tmp[tmpIdx + 9] << 3;
       l6 |= (tmp[tmpIdx + 10] >>> 10) & MASK32_3;
       longs[longsIdx + 6] = l6;
       long l7 = (tmp[tmpIdx + 10] & MASK32_10) << 9;
       l7 |= (tmp[tmpIdx + 11] >>> 4) & MASK32_9;
       longs[longsIdx + 7] = l7;
       long l8 = (tmp[tmpIdx + 11] & MASK32_4) << 15;
-      l8 |= (tmp[tmpIdx + 12] & MASK32_13) << 2;
+      l8 |= tmp[tmpIdx + 12] << 2;
       l8 |= (tmp[tmpIdx + 13] >>> 11) & MASK32_2;
       longs[longsIdx + 8] = l8;
       long l9 = (tmp[tmpIdx + 13] & MASK32_11) << 8;
       l9 |= (tmp[tmpIdx + 14] >>> 5) & MASK32_8;
       longs[longsIdx + 9] = l9;
       long l10 = (tmp[tmpIdx + 14] & MASK32_5) << 14;
-      l10 |= (tmp[tmpIdx + 15] & MASK32_13) << 1;
+      l10 |= tmp[tmpIdx + 15] << 1;
       l10 |= (tmp[tmpIdx + 16] >>> 12) & MASK32_1;
       longs[longsIdx + 10] = l10;
       long l11 = (tmp[tmpIdx + 16] & MASK32_12) << 7;
       l11 |= (tmp[tmpIdx + 17] >>> 6) & MASK32_7;
       longs[longsIdx + 11] = l11;
       long l12 = (tmp[tmpIdx + 17] & MASK32_6) << 13;
-      l12 |= (tmp[tmpIdx + 18] & MASK32_13) << 0;
+      l12 |= tmp[tmpIdx + 18] << 0;
       longs[longsIdx + 12] = l12;
     }
   }
 
-  private static void decode20(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode20(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 40);
+      throws IOException {
-    shiftLongs(tmp, 40, longs, 0, 12, MASK32_20);
+    pdu.splitLongs(40, longs, 12, MASK32_20, tmp, 0, MASK32_12);
     for (int iter = 0, tmpIdx = 0, longsIdx = 40; iter < 8; ++iter, tmpIdx += 5, longsIdx += 3) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_12) << 8;
+      long l0 = tmp[tmpIdx + 0] << 8;
       l0 |= (tmp[tmpIdx + 1] >>> 4) & MASK32_8;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK32_4) << 16;
-      l1 |= (tmp[tmpIdx + 2] & MASK32_12) << 4;
+      l1 |= tmp[tmpIdx + 2] << 4;
       l1 |= (tmp[tmpIdx + 3] >>> 8) & MASK32_4;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 3] & MASK32_8) << 12;
-      l2 |= (tmp[tmpIdx + 4] & MASK32_12) << 0;
+      l2 |= tmp[tmpIdx + 4] << 0;
       longs[longsIdx + 2] = l2;
     }
   }
 
-  private static void decode21(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode21(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 42);
+      throws IOException {
-    shiftLongs(tmp, 42, longs, 0, 11, MASK32_21);
+    pdu.splitLongs(42, longs, 11, MASK32_21, tmp, 0, MASK32_11);
     for (int iter = 0, tmpIdx = 0, longsIdx = 42; iter < 2; ++iter, tmpIdx += 21, longsIdx += 11) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_11) << 10;
+      long l0 = tmp[tmpIdx + 0] << 10;
       l0 |= (tmp[tmpIdx + 1] >>> 1) & MASK32_10;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 1] & MASK32_1) << 20;
-      l1 |= (tmp[tmpIdx + 2] & MASK32_11) << 9;
+      l1 |= tmp[tmpIdx + 2] << 9;
       l1 |= (tmp[tmpIdx + 3] >>> 2) & MASK32_9;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 3] & MASK32_2) << 19;
-      l2 |= (tmp[tmpIdx + 4] & MASK32_11) << 8;
+      l2 |= tmp[tmpIdx + 4] << 8;
       l2 |= (tmp[tmpIdx + 5] >>> 3) & MASK32_8;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 5] & MASK32_3) << 18;
-      l3 |= (tmp[tmpIdx + 6] & MASK32_11) << 7;
+      l3 |= tmp[tmpIdx + 6] << 7;
       l3 |= (tmp[tmpIdx + 7] >>> 4) & MASK32_7;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 7] & MASK32_4) << 17;
-      l4 |= (tmp[tmpIdx + 8] & MASK32_11) << 6;
+      l4 |= tmp[tmpIdx + 8] << 6;
       l4 |= (tmp[tmpIdx + 9] >>> 5) & MASK32_6;
       longs[longsIdx + 4] = l4;
       long l5 = (tmp[tmpIdx + 9] & MASK32_5) << 16;
-      l5 |= (tmp[tmpIdx + 10] & MASK32_11) << 5;
+      l5 |= tmp[tmpIdx + 10] << 5;
       l5 |= (tmp[tmpIdx + 11] >>> 6) & MASK32_5;
       longs[longsIdx + 5] = l5;
       long l6 = (tmp[tmpIdx + 11] & MASK32_6) << 15;
-      l6 |= (tmp[tmpIdx + 12] & MASK32_11) << 4;
+      l6 |= tmp[tmpIdx + 12] << 4;
       l6 |= (tmp[tmpIdx + 13] >>> 7) & MASK32_4;
       longs[longsIdx + 6] = l6;
       long l7 = (tmp[tmpIdx + 13] & MASK32_7) << 14;
-      l7 |= (tmp[tmpIdx + 14] & MASK32_11) << 3;
+      l7 |= tmp[tmpIdx + 14] << 3;
       l7 |= (tmp[tmpIdx + 15] >>> 8) & MASK32_3;
       longs[longsIdx + 7] = l7;
       long l8 = (tmp[tmpIdx + 15] & MASK32_8) << 13;
-      l8 |= (tmp[tmpIdx + 16] & MASK32_11) << 2;
+      l8 |= tmp[tmpIdx + 16] << 2;
       l8 |= (tmp[tmpIdx + 17] >>> 9) & MASK32_2;
       longs[longsIdx + 8] = l8;
       long l9 = (tmp[tmpIdx + 17] & MASK32_9) << 12;
-      l9 |= (tmp[tmpIdx + 18] & MASK32_11) << 1;
+      l9 |= tmp[tmpIdx + 18] << 1;
       l9 |= (tmp[tmpIdx + 19] >>> 10) & MASK32_1;
       longs[longsIdx + 9] = l9;
       long l10 = (tmp[tmpIdx + 19] & MASK32_10) << 11;
-      l10 |= (tmp[tmpIdx + 20] & MASK32_11) << 0;
+      l10 |= tmp[tmpIdx + 20] << 0;
       longs[longsIdx + 10] = l10;
     }
   }
 
-  private static void decode22(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode22(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 44);
+      throws IOException {
-    shiftLongs(tmp, 44, longs, 0, 10, MASK32_22);
+    pdu.splitLongs(44, longs, 10, MASK32_22, tmp, 0, MASK32_10);
     for (int iter = 0, tmpIdx = 0, longsIdx = 44; iter < 4; ++iter, tmpIdx += 11, longsIdx += 5) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_10) << 12;
+      long l0 = tmp[tmpIdx + 0] << 12;
-      l0 |= (tmp[tmpIdx + 1] & MASK32_10) << 2;
+      l0 |= tmp[tmpIdx + 1] << 2;
       l0 |= (tmp[tmpIdx + 2] >>> 8) & MASK32_2;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 2] & MASK32_8) << 14;
-      l1 |= (tmp[tmpIdx + 3] & MASK32_10) << 4;
+      l1 |= tmp[tmpIdx + 3] << 4;
       l1 |= (tmp[tmpIdx + 4] >>> 6) & MASK32_4;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 4] & MASK32_6) << 16;
-      l2 |= (tmp[tmpIdx + 5] & MASK32_10) << 6;
+      l2 |= tmp[tmpIdx + 5] << 6;
       l2 |= (tmp[tmpIdx + 6] >>> 4) & MASK32_6;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 6] & MASK32_4) << 18;
-      l3 |= (tmp[tmpIdx + 7] & MASK32_10) << 8;
+      l3 |= tmp[tmpIdx + 7] << 8;
       l3 |= (tmp[tmpIdx + 8] >>> 2) & MASK32_8;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 8] & MASK32_2) << 20;
-      l4 |= (tmp[tmpIdx + 9] & MASK32_10) << 10;
+      l4 |= tmp[tmpIdx + 9] << 10;
-      l4 |= (tmp[tmpIdx + 10] & MASK32_10) << 0;
+      l4 |= tmp[tmpIdx + 10] << 0;
       longs[longsIdx + 4] = l4;
     }
   }
 
-  private static void decode23(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode23(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 46);
+      throws IOException {
-    shiftLongs(tmp, 46, longs, 0, 9, MASK32_23);
+    pdu.splitLongs(46, longs, 9, MASK32_23, tmp, 0, MASK32_9);
     for (int iter = 0, tmpIdx = 0, longsIdx = 46; iter < 2; ++iter, tmpIdx += 23, longsIdx += 9) {
-      long l0 = (tmp[tmpIdx + 0] & MASK32_9) << 14;
+      long l0 = tmp[tmpIdx + 0] << 14;
-      l0 |= (tmp[tmpIdx + 1] & MASK32_9) << 5;
+      l0 |= tmp[tmpIdx + 1] << 5;
       l0 |= (tmp[tmpIdx + 2] >>> 4) & MASK32_5;
       longs[longsIdx + 0] = l0;
       long l1 = (tmp[tmpIdx + 2] & MASK32_4) << 19;
-      l1 |= (tmp[tmpIdx + 3] & MASK32_9) << 10;
+      l1 |= tmp[tmpIdx + 3] << 10;
-      l1 |= (tmp[tmpIdx + 4] & MASK32_9) << 1;
+      l1 |= tmp[tmpIdx + 4] << 1;
       l1 |= (tmp[tmpIdx + 5] >>> 8) & MASK32_1;
       longs[longsIdx + 1] = l1;
       long l2 = (tmp[tmpIdx + 5] & MASK32_8) << 15;
-      l2 |= (tmp[tmpIdx + 6] & MASK32_9) << 6;
+      l2 |= tmp[tmpIdx + 6] << 6;
       l2 |= (tmp[tmpIdx + 7] >>> 3) & MASK32_6;
       longs[longsIdx + 2] = l2;
       long l3 = (tmp[tmpIdx + 7] & MASK32_3) << 20;
-      l3 |= (tmp[tmpIdx + 8] & MASK32_9) << 11;
+      l3 |= tmp[tmpIdx + 8] << 11;
-      l3 |= (tmp[tmpIdx + 9] & MASK32_9) << 2;
+      l3 |= tmp[tmpIdx + 9] << 2;
       l3 |= (tmp[tmpIdx + 10] >>> 7) & MASK32_2;
       longs[longsIdx + 3] = l3;
       long l4 = (tmp[tmpIdx + 10] & MASK32_7) << 16;
-      l4 |= (tmp[tmpIdx + 11] & MASK32_9) << 7;
+      l4 |= tmp[tmpIdx + 11] << 7;
       l4 |= (tmp[tmpIdx + 12] >>> 2) & MASK32_7;
       longs[longsIdx + 4] = l4;
       long l5 = (tmp[tmpIdx + 12] & MASK32_2) << 21;
-      l5 |= (tmp[tmpIdx + 13] & MASK32_9) << 12;
+      l5 |= tmp[tmpIdx + 13] << 12;
-      l5 |= (tmp[tmpIdx + 14] & MASK32_9) << 3;
+      l5 |= tmp[tmpIdx + 14] << 3;
       l5 |= (tmp[tmpIdx + 15] >>> 6) & MASK32_3;
       longs[longsIdx + 5] = l5;
       long l6 = (tmp[tmpIdx + 15] & MASK32_6) << 17;
-      l6 |= (tmp[tmpIdx + 16] & MASK32_9) << 8;
+      l6 |= tmp[tmpIdx + 16] << 8;
       l6 |= (tmp[tmpIdx + 17] >>> 1) & MASK32_8;
       longs[longsIdx + 6] = l6;
       long l7 = (tmp[tmpIdx + 17] & MASK32_1) << 22;
-      l7 |= (tmp[tmpIdx + 18] & MASK32_9) << 13;
+      l7 |= tmp[tmpIdx + 18] << 13;
-      l7 |= (tmp[tmpIdx + 19] & MASK32_9) << 4;
+      l7 |= tmp[tmpIdx + 19] << 4;
       l7 |= (tmp[tmpIdx + 20] >>> 5) & MASK32_4;
       longs[longsIdx + 7] = l7;
       long l8 = (tmp[tmpIdx + 20] & MASK32_5) << 18;
-      l8 |= (tmp[tmpIdx + 21] & MASK32_9) << 9;
+      l8 |= tmp[tmpIdx + 21] << 9;
-      l8 |= (tmp[tmpIdx + 22] & MASK32_9) << 0;
+      l8 |= tmp[tmpIdx + 22] << 0;
       longs[longsIdx + 8] = l8;
     }
   }
 
-  private static void decode24(DataInput in, long[] tmp, long[] longs) throws IOException {
+  private static void decode24(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
-    in.readLongs(tmp, 0, 48);
+      throws IOException {
-    shiftLongs(tmp, 48, longs, 0, 8, MASK32_24);
+    pdu.splitLongs(48, longs, 8, MASK32_24, tmp, 0, MASK32_8);
-    shiftLongs(tmp, 48, tmp, 0, 0, MASK32_8);
     for (int iter = 0, tmpIdx = 0, longsIdx = 48; iter < 16; ++iter, tmpIdx += 3, longsIdx += 1) {
       long l0 = tmp[tmpIdx + 0] << 16;
       l0 |= tmp[tmpIdx + 1] << 8;

lucene/core/src/java/org/apache/lucene/codecs/lucene912/Lucene912PostingsReader.java

@@ -352,6 +352,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     final IndexInput startDocIn;
 
     IndexInput docIn;
+    PostingIndexInput postingDocIn;
     final boolean indexHasFreq;
     final boolean indexHasPos;
     final boolean indexHasOffsetsOrPayloads;
@@ -413,6 +414,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
         if (docIn == null) {
           // lazy init
           docIn = startDocIn.clone();
+          postingDocIn = new PostingIndexInput(docIn, forUtil);
         }
         prefetchPostings(docIn, termState);
       }
@@ -446,7 +448,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     public int freq() throws IOException {
       if (freqFP != -1) {
         docIn.seek(freqFP);
-        pforUtil.decode(docIn, freqBuffer);
+        pforUtil.decode(postingDocIn, freqBuffer);
         freqFP = -1;
       }
 
@@ -481,7 +483,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     private void refillFullBlock() throws IOException {
       assert docFreq - docCountUpto >= BLOCK_SIZE;
 
-      forDeltaUtil.decodeAndPrefixSum(docIn, prevDocID, docBuffer);
+      forDeltaUtil.decodeAndPrefixSum(postingDocIn, prevDocID, docBuffer);
 
       if (indexHasFreq) {
         if (needsFreq) {
@@ -649,8 +651,11 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     final IndexInput startDocIn;
 
     IndexInput docIn;
+    PostingIndexInput postingDocIn;
     final IndexInput posIn;
+    final PostingIndexInput postingPosIn;
     final IndexInput payIn;
+    final PostingIndexInput postingPayIn;
     final BytesRef payload;
 
     final boolean indexHasFreq;
@@ -718,10 +723,13 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       indexHasOffsetsOrPayloads = indexHasOffsets || indexHasPayloads;
 
       this.posIn = Lucene912PostingsReader.this.posIn.clone();
+      postingPosIn = new PostingIndexInput(posIn, forUtil);
       if (indexHasOffsetsOrPayloads) {
         this.payIn = Lucene912PostingsReader.this.payIn.clone();
+        postingPayIn = new PostingIndexInput(payIn, forUtil);
       } else {
         this.payIn = null;
+        postingPayIn = null;
       }
       if (indexHasOffsets) {
         offsetStartDeltaBuffer = new long[BLOCK_SIZE];
@@ -768,6 +776,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
         if (docIn == null) {
           // lazy init
           docIn = startDocIn.clone();
+          postingDocIn = new PostingIndexInput(docIn, forUtil);
         }
         prefetchPostings(docIn, termState);
       }
@@ -830,8 +839,8 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       assert left >= 0;
 
       if (left >= BLOCK_SIZE) {
-        forDeltaUtil.decodeAndPrefixSum(docIn, prevDocID, docBuffer);
+        forDeltaUtil.decodeAndPrefixSum(postingDocIn, prevDocID, docBuffer);
-        pforUtil.decode(docIn, freqBuffer);
+        pforUtil.decode(postingDocIn, freqBuffer);
         docCountUpto += BLOCK_SIZE;
       } else if (docFreq == 1) {
         docBuffer[0] = singletonDocID;
@@ -1110,11 +1119,11 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
         }
         payloadByteUpto = 0;
       } else {
-        pforUtil.decode(posIn, posDeltaBuffer);
+        pforUtil.decode(postingPosIn, posDeltaBuffer);
 
         if (indexHasPayloads) {
           if (needsPayloads) {
-            pforUtil.decode(payIn, payloadLengthBuffer);
+            pforUtil.decode(postingPayIn, payloadLengthBuffer);
             int numBytes = payIn.readVInt();
 
             if (numBytes > payloadBytes.length) {
@@ -1133,8 +1142,8 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
 
         if (indexHasOffsets) {
           if (needsOffsets) {
-            pforUtil.decode(payIn, offsetStartDeltaBuffer);
+            pforUtil.decode(postingPayIn, offsetStartDeltaBuffer);
-            pforUtil.decode(payIn, offsetLengthBuffer);
+            pforUtil.decode(postingPayIn, offsetLengthBuffer);
           } else {
             // this works, because when writing a vint block we always force the first length to be
             // written
@@ -1217,7 +1226,8 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
 
     final IndexInput startDocIn;
 
-    IndexInput docIn;
+    final IndexInput docIn;
+    final PostingIndexInput postingDocIn;
     final boolean indexHasFreq;
     final boolean indexHasPos;
     final boolean indexHasOffsetsOrPayloads;
@@ -1248,7 +1258,6 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     public BlockImpactsDocsEnum(FieldInfo fieldInfo, IntBlockTermState termState)
         throws IOException {
       this.startDocIn = Lucene912PostingsReader.this.docIn;
-      this.docIn = null;
       indexHasFreq = fieldInfo.getIndexOptions().compareTo(IndexOptions.DOCS_AND_FREQS) >= 0;
       indexHasPos =
           fieldInfo.getIndexOptions().compareTo(IndexOptions.DOCS_AND_FREQS_AND_POSITIONS) >= 0;
@@ -1264,11 +1273,12 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
 
       docFreq = termState.docFreq;
       if (docFreq > 1) {
-        if (docIn == null) {
+        docIn = startDocIn.clone();
-          // lazy init
+        postingDocIn = new PostingIndexInput(docIn, forUtil);
-          docIn = startDocIn.clone();
-        }
         prefetchPostings(docIn, termState);
+      } else {
+        docIn = null;
+        postingDocIn = null;
       }
 
       doc = -1;
@@ -1302,7 +1312,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     public int freq() throws IOException {
       if (freqFP != -1) {
         docIn.seek(freqFP);
-        pforUtil.decode(docIn, freqBuffer);
+        pforUtil.decode(postingDocIn, freqBuffer);
         freqFP = -1;
       }
       return (int) freqBuffer[docBufferUpto - 1];
@@ -1338,7 +1348,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       assert left >= 0;
 
       if (left >= BLOCK_SIZE) {
-        forDeltaUtil.decodeAndPrefixSum(docIn, prevDocID, docBuffer);
+        forDeltaUtil.decodeAndPrefixSum(postingDocIn, prevDocID, docBuffer);
 
         if (indexHasFreq) {
           freqFP = docIn.getFilePointer();
@@ -1573,8 +1583,10 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
 
     final IndexInput startDocIn;
 
-    IndexInput docIn;
+    final IndexInput docIn;
+    final PostingIndexInput postingDocIn;
     final IndexInput posIn;
+    final PostingIndexInput postingPosIn;
 
     final boolean indexHasFreq;
     final boolean indexHasPos;
@@ -1628,7 +1640,6 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
     public BlockImpactsPostingsEnum(FieldInfo fieldInfo, IntBlockTermState termState)
         throws IOException {
       this.startDocIn = Lucene912PostingsReader.this.docIn;
-      this.docIn = null;
       indexHasFreq = fieldInfo.getIndexOptions().compareTo(IndexOptions.DOCS_AND_FREQS) >= 0;
       indexHasPos =
           fieldInfo.getIndexOptions().compareTo(IndexOptions.DOCS_AND_FREQS_AND_POSITIONS) >= 0;
@@ -1641,6 +1652,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       indexHasOffsetsOrPayloads = indexHasOffsets || indexHasPayloads;
 
       this.posIn = Lucene912PostingsReader.this.posIn.clone();
+      postingPosIn = new PostingIndexInput(posIn, forUtil);
 
       // We set the last element of docBuffer to NO_MORE_DOCS, it helps save conditionals in
       // advance()
@@ -1651,11 +1663,12 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       totalTermFreq = termState.totalTermFreq;
       singletonDocID = termState.singletonDocID;
       if (docFreq > 1) {
-        if (docIn == null) {
+        docIn = startDocIn.clone();
-          // lazy init
+        postingDocIn = new PostingIndexInput(docIn, forUtil);
-          docIn = startDocIn.clone();
-        }
         prefetchPostings(docIn, termState);
+      } else {
+        docIn = null;
+        postingDocIn = null;
       }
       posIn.seek(posTermStartFP);
       level1PosEndFP = posTermStartFP;
@@ -1707,8 +1720,8 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
       assert left >= 0;
 
       if (left >= BLOCK_SIZE) {
-        forDeltaUtil.decodeAndPrefixSum(docIn, prevDocID, docBuffer);
+        forDeltaUtil.decodeAndPrefixSum(postingDocIn, prevDocID, docBuffer);
-        pforUtil.decode(docIn, freqBuffer);
+        pforUtil.decode(postingDocIn, freqBuffer);
         docCountUpto += BLOCK_SIZE;
       } else if (docFreq == 1) {
         docBuffer[0] = singletonDocID;
@@ -1981,7 +1994,7 @@ public final class Lucene912PostingsReader extends PostingsReaderBase {
           }
         }
       } else {
-        pforUtil.decode(posIn, posDeltaBuffer);
+        pforUtil.decode(postingPosIn, posDeltaBuffer);
       }
     }
 

lucene/core/src/java/org/apache/lucene/codecs/lucene912/Lucene912PostingsWriter.java

@@ -16,10 +16,12 @@
  */
 package org.apache.lucene.codecs.lucene912;
 
-import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.*;
 import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.BLOCK_SIZE;
 import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.DOC_CODEC;
+import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.LEVEL1_MASK;
+import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.META_CODEC;
 import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.PAY_CODEC;
+import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.POS_CODEC;
 import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.TERMS_CODEC;
 import static org.apache.lucene.codecs.lucene912.Lucene912PostingsFormat.VERSION_CURRENT;
 

lucene/core/src/java/org/apache/lucene/codecs/lucene912/PForUtil.java

@@ -104,18 +104,18 @@ final class PForUtil {
   }
 
   /** Decode 128 integers into {@code ints}. */
-  void decode(DataInput in, long[] longs) throws IOException {
+  void decode(PostingIndexInput in, long[] longs) throws IOException {
-    final int token = Byte.toUnsignedInt(in.readByte());
+    final int token = Byte.toUnsignedInt(in.in.readByte());
     final int bitsPerValue = token & 0x1f;
     final int numExceptions = token >>> 5;
     if (bitsPerValue == 0) {
-      Arrays.fill(longs, 0, ForUtil.BLOCK_SIZE, in.readVLong());
+      Arrays.fill(longs, 0, ForUtil.BLOCK_SIZE, in.in.readVLong());
     } else {
-      forUtil.decode(bitsPerValue, in, longs);
+      in.decode(bitsPerValue, longs);
     }
     for (int i = 0; i < numExceptions; ++i) {
-      longs[Byte.toUnsignedInt(in.readByte())] |=
+      longs[Byte.toUnsignedInt(in.in.readByte())] |=
-          Byte.toUnsignedLong(in.readByte()) << bitsPerValue;
+          Byte.toUnsignedLong(in.in.readByte()) << bitsPerValue;
     }
   }
 

lucene/core/src/java/org/apache/lucene/codecs/lucene912/PostingIndexInput.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.codecs.lucene912;
+
+import java.io.IOException;
+import org.apache.lucene.internal.vectorization.PostingDecodingUtil;
+import org.apache.lucene.internal.vectorization.VectorizationProvider;
+import org.apache.lucene.store.IndexInput;
+
+/**
+ * Wrapper around an {@link IndexInput} and a {@link ForUtil} that optionally optimizes decoding
+ * using vectorization.
+ */
+public final class PostingIndexInput {
+
+  private static final VectorizationProvider VECTORIZATION_PROVIDER =
+      VectorizationProvider.getInstance();
+
+  public final IndexInput in;
+  public final ForUtil forUtil;
+  private final PostingDecodingUtil postingDecodingUtil;
+
+  public PostingIndexInput(IndexInput in, ForUtil forUtil) throws IOException {
+    this.in = in;
+    this.forUtil = forUtil;
+    this.postingDecodingUtil = VECTORIZATION_PROVIDER.newPostingDecodingUtil(in);
+  }
+
+  /** Decode 128 integers stored on {@code bitsPerValues} bits per value into {@code longs}. */
+  public void decode(int bitsPerValue, long[] longs) throws IOException {
+    forUtil.decode(bitsPerValue, in, postingDecodingUtil, longs);
+  }
+
+  /**
+   * Decode 128 integers stored on {@code bitsPerValues} bits per value, compute their prefix sum,
+   * and store results into {@code longs}.
+   */
+  public void decodeAndPrefixSum(int bitsPerValue, long base, long[] longs) throws IOException {
+    forUtil.decodeAndPrefixSum(bitsPerValue, in, postingDecodingUtil, base, longs);
+  }
+}

lucene/core/src/java/org/apache/lucene/codecs/lucene912/gen_ForUtil.py

@@ -43,17 +43,20 @@ HEADER = """// This file has been automatically generated, DO NOT EDIT
 package org.apache.lucene.codecs.lucene912;
 
 import java.io.IOException;
-import org.apache.lucene.store.DataInput;
+import org.apache.lucene.internal.vectorization.PostingDecodingUtil;
 import org.apache.lucene.store.DataOutput;
+import org.apache.lucene.store.IndexInput;
 
-// Inspired from https://fulmicoton.com/posts/bitpacking/
+/**
-// Encodes multiple integers in a long to get SIMD-like speedups.
+ * Inspired from https://fulmicoton.com/posts/bitpacking/
-// If bitsPerValue <= 8 then we pack 8 ints per long
+ * Encodes multiple integers in a long to get SIMD-like speedups.
-// else if bitsPerValue <= 16 we pack 4 ints per long
+ * If bitsPerValue &lt;= 8 then we pack 8 ints per long
-// else we pack 2 ints per long
+ * else if bitsPerValue &lt;= 16 we pack 4 ints per long
-final class ForUtil {
+ * else we pack 2 ints per long
+ */
+public final class ForUtil {
 
-  static final int BLOCK_SIZE = 128;
+  public static final int BLOCK_SIZE = 128;
   private static final int BLOCK_SIZE_LOG2 = 7;
 
   private static long expandMask32(long mask32) {
@@ -324,13 +327,13 @@ final class ForUtil {
     return bitsPerValue << (BLOCK_SIZE_LOG2 - 3);
   }
 
-  private static void decodeSlow(int bitsPerValue, DataInput in, long[] tmp, long[] longs)
+  private static void decodeSlow(int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs)
       throws IOException {
     final int numLongs = bitsPerValue << 1;
-    in.readLongs(tmp, 0, numLongs);
     final long mask = MASKS32[bitsPerValue];
-    int longsIdx = 0;
+    pdu.splitLongs(numLongs, longs, 32 - bitsPerValue, mask, tmp, 0, -1L);
-    int shift = 32 - bitsPerValue;
+    int longsIdx = numLongs;
+    int shift = 32 - 2 * bitsPerValue;
     for (; shift >= 0; shift -= bitsPerValue) {
       shiftLongs(tmp, numLongs, longs, longsIdx, shift, mask);
       longsIdx += numLongs;
@@ -366,31 +369,17 @@ final class ForUtil {
     }
   }
 
+  /**
+   * Likewise, but for a simple mask.
+   */
+  private static void maskLongs(long[] a, int count, long[] b, int bi, long mask) {
+    for (int i = 0; i < count; ++i) {
+      b[bi + i] = a[i] & mask;
+    }
+  }
+
 """
 
-def writeRemainderWithSIMDOptimize(bpv, next_primitive, remaining_bits_per_long, o, num_values, f):
-  iteration = 1
-  num_longs = bpv * num_values / remaining_bits_per_long
-  while num_longs % 2 == 0 and num_values % 2 == 0:
-    num_longs /= 2
-    num_values /= 2
-    iteration *= 2
-
-  f.write('    shiftLongs(tmp, %d, tmp, 0, 0, MASK%d_%d);\n' % (iteration * num_longs, next_primitive, remaining_bits_per_long))
-  f.write('    for (int iter = 0, tmpIdx = 0, longsIdx = %d; iter < %d; ++iter, tmpIdx += %d, longsIdx += %d) {\n' %(o, iteration, num_longs, num_values))
-  tmp_idx = 0
-  b = bpv
-  b -= remaining_bits_per_long
-  f.write('      long l0 = tmp[tmpIdx + %d] << %d;\n' %(tmp_idx, b))
-  tmp_idx += 1
-  while b >= remaining_bits_per_long:
-    b -= remaining_bits_per_long
-    f.write('      l0 |= tmp[tmpIdx + %d] << %d;\n' %(tmp_idx, b))
-    tmp_idx += 1
-  f.write('      longs[longsIdx + 0] = l0;\n')
-  f.write('    }\n')
-  
-
 def writeRemainder(bpv, next_primitive, remaining_bits_per_long, o, num_values, f):
   iteration = 1
   num_longs = bpv * num_values / remaining_bits_per_long
@@ -406,14 +395,14 @@ def writeRemainder(bpv, next_primitive, remaining_bits_per_long, o, num_values,
     b = bpv
     if remaining_bits == 0:
       b -= remaining_bits_per_long
-      f.write('      long l%d = (tmp[tmpIdx + %d] & MASK%d_%d) << %d;\n' %(i, tmp_idx, next_primitive, remaining_bits_per_long, b))
+      f.write('      long l%d = tmp[tmpIdx + %d] << %d;\n' %(i, tmp_idx, b))
     else:
       b -= remaining_bits
       f.write('      long l%d = (tmp[tmpIdx + %d] & MASK%d_%d) << %d;\n' %(i, tmp_idx, next_primitive, remaining_bits, b))
     tmp_idx += 1
     while b >= remaining_bits_per_long:
       b -= remaining_bits_per_long
-      f.write('      l%d |= (tmp[tmpIdx + %d] & MASK%d_%d) << %d;\n' %(i, tmp_idx, next_primitive, remaining_bits_per_long, b))
+      f.write('      l%d |= tmp[tmpIdx + %d] << %d;\n' %(i, tmp_idx, b))
       tmp_idx += 1
     if b > 0:
       f.write('      l%d |= (tmp[tmpIdx + %d] >>> %d) & MASK%d_%d;\n' %(i, tmp_idx, remaining_bits_per_long-b, next_primitive, b))
@@ -428,23 +417,30 @@ def writeDecode(bpv, f):
     next_primitive = 8
   elif bpv <= 16:
     next_primitive = 16
-  f.write('  private static void decode%d(DataInput in, long[] tmp, long[] longs) throws IOException {\n' %bpv)
+  f.write('  private static void decode%d(IndexInput in, PostingDecodingUtil pdu, long[] tmp, long[] longs) throws IOException {\n' %bpv)
-  num_values_per_long = 64 / next_primitive
   if bpv == next_primitive:
     f.write('    in.readLongs(longs, 0, %d);\n' %(bpv*2))
+  elif bpv * 2 == next_primitive:
+    f.write('    pdu.splitLongs(%d, longs, %d, MASK%d_%d, longs, %d, MASK%d_%d);\n' %(bpv*2, next_primitive - bpv, next_primitive, bpv, bpv*2, next_primitive, next_primitive - bpv))
   else:
-    f.write('    in.readLongs(tmp, 0, %d);\n' %(bpv*2))
+    num_values_per_long = 64 / next_primitive
-    shift = next_primitive - bpv
+    f.write('    pdu.splitLongs(%d, longs, %d, MASK%d_%d, tmp, 0, MASK%d_%d);\n' %(bpv*2, next_primitive - bpv, next_primitive, bpv, next_primitive, next_primitive - bpv))
-    o = 0
+
+    shift = next_primitive - 2 * bpv
+    o = 2 * bpv
     while shift >= 0:
-      f.write('    shiftLongs(tmp, %d, longs, %d, %d, MASK%d_%d);\n' %(bpv*2, o, shift, next_primitive, bpv))
+      if shift == 0:
+        f.write('    maskLongs(tmp, %d, longs, %d, MASK%d_%d);\n' %(bpv*2, o, next_primitive, bpv))
+      else:
+        f.write('    shiftLongs(tmp, %d, longs, %d, %d, MASK%d_%d);\n' %(bpv*2, o, shift, next_primitive, bpv))
       o += bpv*2
       shift -= bpv
-    if shift + bpv > 0:
+    remaining_bits = shift + bpv
-      if bpv % (next_primitive % bpv) == 0:
+    if remaining_bits > 0:
-        writeRemainderWithSIMDOptimize(bpv, next_primitive, shift + bpv, o, 128/num_values_per_long - o, f)
+      if remaining_bits != next_primitive - bpv:
-      else:
+        # values in tmp still have more bits per value than remaining_bits, clear the higher bits now
-        writeRemainder(bpv, next_primitive, shift + bpv, o, 128/num_values_per_long - o, f)
+        f.write('    maskLongs(tmp, %d, tmp, 0, MASK%d_%d);\n' %(bpv*2, next_primitive, remaining_bits))
+      writeRemainder(bpv, next_primitive, remaining_bits, o, 128/num_values_per_long - o, f)
   f.write('  }\n')
 
 
@@ -471,7 +467,7 @@ if __name__ == '__main__':
 
   f.write("""
   /** Decode 128 integers into {@code longs}. */
-  void decode(int bitsPerValue, DataInput in, long[] longs) throws IOException {
+  void decode(int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long[] longs) throws IOException {
     switch (bitsPerValue) {
 """)
   for bpv in range(1, MAX_SPECIALIZED_BITS_PER_VALUE+1):
@@ -481,11 +477,11 @@ if __name__ == '__main__':
     elif bpv <= 16:
       next_primitive = 16
     f.write('      case %d:\n' %bpv)
-    f.write('        decode%d(in, tmp, longs);\n' %bpv)
+    f.write('        decode%d(in, pdu, tmp, longs);\n' %bpv)
     f.write('        expand%d(longs);\n' %next_primitive)
     f.write('        break;\n')
   f.write('      default:\n')
-  f.write('        decodeSlow(bitsPerValue, in, tmp, longs);\n')
+  f.write('        decodeSlow(bitsPerValue, in, pdu, tmp, longs);\n')
   f.write('        expand32(longs);\n')
   f.write('        break;\n')
   f.write('    }\n')
@@ -495,7 +491,7 @@ if __name__ == '__main__':
   /**
    * Delta-decode 128 integers into {@code longs}.
    */
-  void decodeAndPrefixSum(int bitsPerValue, DataInput in, long base, long[] longs) throws IOException {
+  void decodeAndPrefixSum(int bitsPerValue, IndexInput in, PostingDecodingUtil pdu, long base, long[] longs) throws IOException {
     switch (bitsPerValue) {
 """)
   for bpv in range(1, MAX_SPECIALIZED_BITS_PER_VALUE+1):
@@ -505,11 +501,11 @@ if __name__ == '__main__':
     elif bpv <= 16:
       next_primitive = 16
     f.write('    case %d:\n' %bpv)
-    f.write('      decode%d(in, tmp, longs);\n' %bpv)
+    f.write('      decode%d(in, pdu, tmp, longs);\n' %bpv)
     f.write('      prefixSum%d(longs, base);\n' %next_primitive)
     f.write('      break;\n')
   f.write('    default:\n')
-  f.write('      decodeSlow(bitsPerValue, in, tmp, longs);\n')
+  f.write('      decodeSlow(bitsPerValue, in, pdu, tmp, longs);\n')
   f.write('      prefixSum32(longs, base);\n')
   f.write('      break;\n')
   f.write('    }\n')

lucene/core/src/java/org/apache/lucene/internal/vectorization/DefaultPostingDecodingUtil.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.internal.vectorization;
+
+import java.io.IOException;
+import org.apache.lucene.store.IndexInput;
+
+final class DefaultPostingDecodingUtil extends PostingDecodingUtil {
+
+  protected final IndexInput in;
+
+  public DefaultPostingDecodingUtil(IndexInput in) {
+    this.in = in;
+  }
+
+  @Override
+  public void splitLongs(
+      int count, long[] b, int bShift, long bMask, long[] c, int cIndex, long cMask)
+      throws IOException {
+    assert count <= 64;
+    in.readLongs(c, cIndex, count);
+    // The below loop is auto-vectorized
+    for (int i = 0; i < count; ++i) {
+      b[i] = (c[cIndex + i] >>> bShift) & bMask;
+      c[cIndex + i] &= cMask;
+    }
+  }
+}

lucene/core/src/java/org/apache/lucene/internal/vectorization/DefaultVectorizationProvider.java

@@ -19,6 +19,7 @@ package org.apache.lucene.internal.vectorization;
 
 import org.apache.lucene.codecs.hnsw.DefaultFlatVectorScorer;
 import org.apache.lucene.codecs.hnsw.FlatVectorsScorer;
+import org.apache.lucene.store.IndexInput;
 
 /** Default provider returning scalar implementations. */
 final class DefaultVectorizationProvider extends VectorizationProvider {
@@ -38,4 +39,9 @@ final class DefaultVectorizationProvider extends VectorizationProvider {
   public FlatVectorsScorer getLucene99FlatVectorsScorer() {
     return DefaultFlatVectorScorer.INSTANCE;
   }
+
+  @Override
+  public PostingDecodingUtil newPostingDecodingUtil(IndexInput input) {
+    return new DefaultPostingDecodingUtil(input);
+  }
 }

lucene/core/src/java/org/apache/lucene/internal/vectorization/PostingDecodingUtil.java

@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.internal.vectorization;
+
+import java.io.IOException;
+
+/** Utility class to decode postings. */
+public abstract class PostingDecodingUtil {
+
+  /**
+   * Read {@code count} longs. This number must not exceed 64. Apply shift {@code bShift} and mask
+   * {@code bMask} and store the result in {@code b} starting at offset 0. Apply mask {@code cMask}
+   * and store the result in {@code c} starting at offset {@code cIndex}.
+   */
+  public abstract void splitLongs(
+      int count, long[] b, int bShift, long bMask, long[] c, int cIndex, long cMask)
+      throws IOException;
+}

lucene/core/src/java/org/apache/lucene/internal/vectorization/VectorizationProvider.java

@@ -17,6 +17,7 @@
 
 package org.apache.lucene.internal.vectorization;
 
+import java.io.IOException;
 import java.lang.StackWalker.StackFrame;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
@@ -28,6 +29,7 @@ import java.util.function.Predicate;
 import java.util.logging.Logger;
 import java.util.stream.Stream;
 import org.apache.lucene.codecs.hnsw.FlatVectorsScorer;
+import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.util.Constants;
 import org.apache.lucene.util.VectorUtil;
 
@@ -95,6 +97,9 @@ public abstract class VectorizationProvider {
   /** Returns a FlatVectorsScorer that supports the Lucene99 format. */
   public abstract FlatVectorsScorer getLucene99FlatVectorsScorer();
 
+  /** Create a new {@link PostingDecodingUtil} for the given {@link IndexInput}. */
+  public abstract PostingDecodingUtil newPostingDecodingUtil(IndexInput input) throws IOException;
+
   // *** Lookup mechanism: ***
 
   private static final Logger LOG = Logger.getLogger(VectorizationProvider.class.getName());
@@ -184,7 +189,8 @@ public abstract class VectorizationProvider {
   private static final Set<String> VALID_CALLERS =
       Set.of(
           "org.apache.lucene.codecs.hnsw.FlatVectorScorerUtil",
-          "org.apache.lucene.util.VectorUtil");
+          "org.apache.lucene.util.VectorUtil",
+          "org.apache.lucene.codecs.lucene912.PostingIndexInput");
 
   private static void ensureCaller() {
     final boolean validCaller =

lucene/core/src/java21/org/apache/lucene/internal/vectorization/MemorySegmentPostingDecodingUtil.java

@@ -0,0 +1,85 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.internal.vectorization;
+
+import java.io.IOException;
+import java.lang.foreign.MemorySegment;
+import java.nio.ByteOrder;
+import jdk.incubator.vector.LongVector;
+import jdk.incubator.vector.VectorOperators;
+import jdk.incubator.vector.VectorSpecies;
+import org.apache.lucene.store.IndexInput;
+
+final class MemorySegmentPostingDecodingUtil extends PostingDecodingUtil {
+
+  private static final VectorSpecies<Long> LONG_SPECIES =
+      PanamaVectorConstants.PRERERRED_LONG_SPECIES;
+
+  private final IndexInput in;
+  private final MemorySegment memorySegment;
+
+  MemorySegmentPostingDecodingUtil(IndexInput in, MemorySegment memorySegment) {
+    this.in = in;
+    this.memorySegment = memorySegment;
+  }
+
+  @Override
+  public void splitLongs(
+      int count, long[] b, int bShift, long bMask, long[] c, int cIndex, long cMask)
+      throws IOException {
+    if (count < LONG_SPECIES.length()) {
+      // Not enough data to vectorize without going out-of-bounds. In practice, this branch is never
+      // used if the bit width is 256, and is used for 2 and 3 bits per value if the bit width is
+      // 512.
+      in.readLongs(c, cIndex, count);
+      for (int i = 0; i < count; ++i) {
+        b[i] = (c[cIndex + i] >>> bShift) & bMask;
+        c[cIndex + i] &= cMask;
+      }
+    } else {
+      long offset = in.getFilePointer();
+      long endOffset = offset + count * Long.BYTES;
+      int loopBound = LONG_SPECIES.loopBound(count - 1);
+      for (int i = 0;
+          i < loopBound;
+          i += LONG_SPECIES.length(), offset += LONG_SPECIES.length() * Long.BYTES) {
+        LongVector vector =
+            LongVector.fromMemorySegment(
+                LONG_SPECIES, memorySegment, offset, ByteOrder.LITTLE_ENDIAN);
+        vector
+            .lanewise(VectorOperators.LSHR, bShift)
+            .lanewise(VectorOperators.AND, bMask)
+            .intoArray(b, i);
+        vector.lanewise(VectorOperators.AND, cMask).intoArray(c, cIndex + i);
+      }
+
+      // Handle the tail by reading a vector that is aligned with with `count` on the right side.
+      int i = count - LONG_SPECIES.length();
+      offset = endOffset - LONG_SPECIES.length() * Long.BYTES;
+      LongVector vector =
+          LongVector.fromMemorySegment(
+              LONG_SPECIES, memorySegment, offset, ByteOrder.LITTLE_ENDIAN);
+      vector
+          .lanewise(VectorOperators.LSHR, bShift)
+          .lanewise(VectorOperators.AND, bMask)
+          .intoArray(b, i);
+      vector.lanewise(VectorOperators.AND, cMask).intoArray(c, cIndex + i);
+
+      in.seek(endOffset);
+    }
+  }
+}

lucene/core/src/java21/org/apache/lucene/internal/vectorization/PanamaVectorConstants.java

@@ -0,0 +1,55 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.internal.vectorization;
+
+import jdk.incubator.vector.VectorShape;
+import jdk.incubator.vector.VectorSpecies;
+import org.apache.lucene.util.Constants;
+
+/** Shared constants for implementations that take advantage of the Panama Vector API. */
+final class PanamaVectorConstants {
+
+  /** Preferred width in bits for vectors. */
+  static final int PREFERRED_VECTOR_BITSIZE;
+
+  /** Whether integer vectors can be trusted to actually be fast. */
+  static final boolean HAS_FAST_INTEGER_VECTORS;
+
+  static final VectorSpecies<Long> PRERERRED_LONG_SPECIES;
+  static final VectorSpecies<Integer> PRERERRED_INT_SPECIES;
+
+  static {
+    // default to platform supported bitsize
+    int vectorBitSize = VectorShape.preferredShape().vectorBitSize();
+    // but allow easy overriding for testing
+    PREFERRED_VECTOR_BITSIZE = VectorizationProvider.TESTS_VECTOR_SIZE.orElse(vectorBitSize);
+
+    // hotspot misses some SSE intrinsics, workaround it
+    // to be fair, they do document this thing only works well with AVX2/AVX3 and Neon
+    boolean isAMD64withoutAVX2 =
+        Constants.OS_ARCH.equals("amd64") && PREFERRED_VECTOR_BITSIZE < 256;
+    HAS_FAST_INTEGER_VECTORS =
+        VectorizationProvider.TESTS_FORCE_INTEGER_VECTORS || (isAMD64withoutAVX2 == false);
+
+    PRERERRED_LONG_SPECIES =
+        VectorSpecies.of(long.class, VectorShape.forBitSize(PREFERRED_VECTOR_BITSIZE));
+    PRERERRED_INT_SPECIES =
+        VectorSpecies.of(int.class, VectorShape.forBitSize(PREFERRED_VECTOR_BITSIZE));
+  }
+
+  private PanamaVectorConstants() {}
+}

lucene/core/src/java21/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java

@@ -52,20 +52,15 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
 
   // preferred vector sizes, which can be altered for testing
   private static final VectorSpecies<Float> FLOAT_SPECIES;
-  private static final VectorSpecies<Integer> INT_SPECIES;
+  private static final VectorSpecies<Integer> INT_SPECIES =
+      PanamaVectorConstants.PRERERRED_INT_SPECIES;
   private static final VectorSpecies<Byte> BYTE_SPECIES;
   private static final VectorSpecies<Short> SHORT_SPECIES;
 
   static final int VECTOR_BITSIZE;
-  static final boolean HAS_FAST_INTEGER_VECTORS;
 
   static {
-    // default to platform supported bitsize
+    VECTOR_BITSIZE = PanamaVectorConstants.PREFERRED_VECTOR_BITSIZE;
-    int vectorBitSize = VectorShape.preferredShape().vectorBitSize();
-    // but allow easy overriding for testing
-    vectorBitSize = VectorizationProvider.TESTS_VECTOR_SIZE.orElse(vectorBitSize);
-    INT_SPECIES = VectorSpecies.of(int.class, VectorShape.forBitSize(vectorBitSize));
-    VECTOR_BITSIZE = INT_SPECIES.vectorBitSize();
     FLOAT_SPECIES = INT_SPECIES.withLanes(float.class);
     // compute BYTE/SHORT sizes relative to preferred integer vector size
     if (VECTOR_BITSIZE >= 256) {
@@ -76,11 +71,6 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
       BYTE_SPECIES = null;
       SHORT_SPECIES = null;
     }
-    // hotspot misses some SSE intrinsics, workaround it
-    // to be fair, they do document this thing only works well with AVX2/AVX3 and Neon
-    boolean isAMD64withoutAVX2 = Constants.OS_ARCH.equals("amd64") && VECTOR_BITSIZE < 256;
-    HAS_FAST_INTEGER_VECTORS =
-        VectorizationProvider.TESTS_FORCE_INTEGER_VECTORS || (isAMD64withoutAVX2 == false);
   }
 
   // the way FMA should work! if available use it, otherwise fall back to mul/add
@@ -320,7 +310,7 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
 
     // only vectorize if we'll at least enter the loop a single time, and we have at least 128-bit
     // vectors (256-bit on intel to dodge performance landmines)
-    if (a.byteSize() >= 16 && HAS_FAST_INTEGER_VECTORS) {
+    if (a.byteSize() >= 16 && PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS) {
       // compute vectorized dot product consistent with VPDPBUSD instruction
       if (VECTOR_BITSIZE >= 512) {
         i += BYTE_SPECIES.loopBound(a.byteSize());
@@ -414,7 +404,7 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
         } else if (VECTOR_BITSIZE == 256) {
           i += ByteVector.SPECIES_128.loopBound(packed.length);
           res += dotProductBody256Int4Packed(unpacked, packed, i);
-        } else if (HAS_FAST_INTEGER_VECTORS) {
+        } else if (PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS) {
           i += ByteVector.SPECIES_64.loopBound(packed.length);
           res += dotProductBody128Int4Packed(unpacked, packed, i);
         }
@@ -430,7 +420,7 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
     } else {
       if (VECTOR_BITSIZE >= 512 || VECTOR_BITSIZE == 256) {
         return dotProduct(a, b);
-      } else if (a.length >= 32 && HAS_FAST_INTEGER_VECTORS) {
+      } else if (a.length >= 32 && PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS) {
         i += ByteVector.SPECIES_128.loopBound(a.length);
         res += int4DotProductBody128(a, b, i);
       }
@@ -588,7 +578,7 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
 
     // only vectorize if we'll at least enter the loop a single time, and we have at least 128-bit
     // vectors (256-bit on intel to dodge performance landmines)
-    if (a.byteSize() >= 16 && HAS_FAST_INTEGER_VECTORS) {
+    if (a.byteSize() >= 16 && PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS) {
       final float[] ret;
       if (VECTOR_BITSIZE >= 512) {
         i += BYTE_SPECIES.loopBound((int) a.byteSize());
@@ -711,7 +701,7 @@ final class PanamaVectorUtilSupport implements VectorUtilSupport {
 
     // only vectorize if we'll at least enter the loop a single time, and we have at least 128-bit
     // vectors (256-bit on intel to dodge performance landmines)
-    if (a.byteSize() >= 16 && HAS_FAST_INTEGER_VECTORS) {
+    if (a.byteSize() >= 16 && PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS) {
       if (VECTOR_BITSIZE >= 256) {
         i += BYTE_SPECIES.loopBound((int) a.byteSize());
         res += squareDistanceBody256(a, b, i);

lucene/core/src/java21/org/apache/lucene/internal/vectorization/PanamaVectorizationProvider.java

@@ -16,19 +16,25 @@
  */
 package org.apache.lucene.internal.vectorization;
 
+import java.io.IOException;
+import java.lang.foreign.MemorySegment;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.Locale;
 import java.util.logging.Logger;
 import jdk.incubator.vector.FloatVector;
 import org.apache.lucene.codecs.hnsw.FlatVectorsScorer;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.MemorySegmentAccessInput;
 import org.apache.lucene.util.Constants;
 import org.apache.lucene.util.SuppressForbidden;
 
 /** A vectorization provider that leverages the Panama Vector API. */
 final class PanamaVectorizationProvider extends VectorizationProvider {
 
-  private final VectorUtilSupport vectorUtilSupport;
+  // NOTE: Avoid static fields or initializers which rely on the vector API, as these initializers
+  // would get called before we have a chance to perform sanity checks around the vector API in the
+  // constructor of this class. Put them in PanamaVectorConstants instead.
 
   // Extracted to a method to be able to apply the SuppressForbidden annotation
   @SuppressWarnings("removal")
@@ -37,6 +43,8 @@ final class PanamaVectorizationProvider extends VectorizationProvider {
     return AccessController.doPrivileged(action);
   }
 
+  private final VectorUtilSupport vectorUtilSupport;
+
   PanamaVectorizationProvider() {
     // hack to work around for JDK-8309727:
     try {
@@ -51,9 +59,9 @@ final class PanamaVectorizationProvider extends VectorizationProvider {
           "We hit initialization failure described in JDK-8309727: " + se);
     }
 
-    if (PanamaVectorUtilSupport.VECTOR_BITSIZE < 128) {
+    if (PanamaVectorConstants.PREFERRED_VECTOR_BITSIZE < 128) {
       throw new UnsupportedOperationException(
-          "Vector bit size is less than 128: " + PanamaVectorUtilSupport.VECTOR_BITSIZE);
+          "Vector bit size is less than 128: " + PanamaVectorConstants.PREFERRED_VECTOR_BITSIZE);
     }
 
     this.vectorUtilSupport = new PanamaVectorUtilSupport();
@@ -63,11 +71,9 @@ final class PanamaVectorizationProvider extends VectorizationProvider {
         String.format(
             Locale.ENGLISH,
             "Java vector incubator API enabled; uses preferredBitSize=%d%s%s",
-            PanamaVectorUtilSupport.VECTOR_BITSIZE,
+            PanamaVectorConstants.PREFERRED_VECTOR_BITSIZE,
             Constants.HAS_FAST_VECTOR_FMA ? "; FMA enabled" : "",
-            PanamaVectorUtilSupport.HAS_FAST_INTEGER_VECTORS
+            PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS ? "" : "; floating-point vectors only"));
-                ? ""
-                : "; floating-point vectors only"));
   }
 
   @Override
@@ -79,4 +85,16 @@ final class PanamaVectorizationProvider extends VectorizationProvider {
   public FlatVectorsScorer getLucene99FlatVectorsScorer() {
     return Lucene99MemorySegmentFlatVectorsScorer.INSTANCE;
   }
+
+  @Override
+  public PostingDecodingUtil newPostingDecodingUtil(IndexInput input) throws IOException {
+    if (PanamaVectorConstants.HAS_FAST_INTEGER_VECTORS
+        && input instanceof MemorySegmentAccessInput msai) {
+      MemorySegment ms = msai.segmentSliceOrNull(0, input.length());
+      if (ms != null) {
+        return new MemorySegmentPostingDecodingUtil(input, ms);
+      }
+    }
+    return new DefaultPostingDecodingUtil(input);
+  }
 }

lucene/core/src/java21/org/apache/lucene/store/MemorySegmentAccessInput.java

@@ -27,7 +27,7 @@ import java.lang.foreign.MemorySegment;
 public interface MemorySegmentAccessInput extends RandomAccessInput, Cloneable {
 
   /** Returns the memory segment for a given position and length, or null. */
-  MemorySegment segmentSliceOrNull(long pos, int len) throws IOException;
+  MemorySegment segmentSliceOrNull(long pos, long len) throws IOException;
 
   MemorySegmentAccessInput clone();
 }

lucene/core/src/java21/org/apache/lucene/store/MemorySegmentIndexInput.java

@@ -742,7 +742,7 @@ abstract class MemorySegmentIndexInput extends IndexInput
     }
 
     @Override
-    public MemorySegment segmentSliceOrNull(long pos, int len) throws IOException {
+    public MemorySegment segmentSliceOrNull(long pos, long len) throws IOException {
       try {
         Objects.checkIndex(pos + len, this.length + 1);
         return curSegment.asSlice(pos, len);
@@ -816,7 +816,8 @@ abstract class MemorySegmentIndexInput extends IndexInput
       return super.readLong(pos + offset);
     }
 
-    public MemorySegment segmentSliceOrNull(long pos, int len) throws IOException {
+    @Override
+    public MemorySegment segmentSliceOrNull(long pos, long len) throws IOException {
       if (pos + len > length) {
         throw handlePositionalIOOBE(null, "segmentSliceOrNull", pos);
       }

lucene/core/src/test/org/apache/lucene/codecs/lucene912/TestForDeltaUtil.java

@@ -64,11 +64,13 @@ public class TestForDeltaUtil extends LuceneTestCase {
     {
       // decode
       IndexInput in = d.openInput("test.bin", IOContext.READONCE);
-      final ForDeltaUtil forDeltaUtil = new ForDeltaUtil(new ForUtil());
+      ForUtil forUtil = new ForUtil();
+      PostingIndexInput postingIn = new PostingIndexInput(in, forUtil);
+      final ForDeltaUtil forDeltaUtil = new ForDeltaUtil(forUtil);
       for (int i = 0; i < iterations; ++i) {
         long base = 0;
         final long[] restored = new long[ForUtil.BLOCK_SIZE];
-        forDeltaUtil.decodeAndPrefixSum(in, base, restored);
+        forDeltaUtil.decodeAndPrefixSum(postingIn, base, restored);
         final long[] expected = new long[ForUtil.BLOCK_SIZE];
         for (int j = 0; j < ForUtil.BLOCK_SIZE; ++j) {
           expected[j] = values[i * ForUtil.BLOCK_SIZE + j];

lucene/core/src/test/org/apache/lucene/codecs/lucene912/TestForUtil.java

@@ -69,12 +69,13 @@ public class TestForUtil extends LuceneTestCase {
     {
       // decode
       IndexInput in = d.openInput("test.bin", IOContext.READONCE);
-      final ForUtil forUtil = new ForUtil();
+      ForUtil forUtil = new ForUtil();
+      PostingIndexInput postingIn = new PostingIndexInput(in, forUtil);
       for (int i = 0; i < iterations; ++i) {
         final int bitsPerValue = in.readByte();
         final long currentFilePointer = in.getFilePointer();
         final long[] restored = new long[ForUtil.BLOCK_SIZE];
-        forUtil.decode(bitsPerValue, in, restored);
+        postingIn.decode(bitsPerValue, restored);
         int[] ints = new int[ForUtil.BLOCK_SIZE];
         for (int j = 0; j < ForUtil.BLOCK_SIZE; ++j) {
           ints[j] = Math.toIntExact(restored[j]);

lucene/core/src/test/org/apache/lucene/codecs/lucene912/TestPForUtil.java

@@ -38,15 +38,17 @@ public class TestPForUtil extends LuceneTestCase {
     final Directory d = new ByteBuffersDirectory();
     final long endPointer = encodeTestData(iterations, values, d);
 
+    ForUtil forUtil = new ForUtil();
     IndexInput in = d.openInput("test.bin", IOContext.READONCE);
-    final PForUtil pforUtil = new PForUtil(new ForUtil());
+    PostingIndexInput postingIn = new PostingIndexInput(in, forUtil);
+    final PForUtil pforUtil = new PForUtil(forUtil);
     for (int i = 0; i < iterations; ++i) {
       if (random().nextInt(5) == 0) {
         pforUtil.skip(in);
         continue;
       }
       final long[] restored = new long[ForUtil.BLOCK_SIZE];
-      pforUtil.decode(in, restored);
+      pforUtil.decode(postingIn, restored);
       int[] ints = new int[ForUtil.BLOCK_SIZE];
       for (int j = 0; j < ForUtil.BLOCK_SIZE; ++j) {
         ints[j] = Math.toIntExact(restored[j]);

lucene/core/src/test/org/apache/lucene/internal/vectorization/TestPostingDecodingUtil.java

@@ -0,0 +1,81 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.lucene.internal.vectorization;
+
+import org.apache.lucene.codecs.lucene912.ForUtil;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.IndexOutput;
+import org.apache.lucene.store.MMapDirectory;
+import org.apache.lucene.tests.util.LuceneTestCase;
+import org.apache.lucene.tests.util.TestUtil;
+
+public class TestPostingDecodingUtil extends LuceneTestCase {
+
+  public void testDuelSplitLongs() throws Exception {
+    final int iterations = atLeast(100);
+
+    try (Directory dir = new MMapDirectory(createTempDir())) {
+      try (IndexOutput out = dir.createOutput("tests.bin", IOContext.DEFAULT)) {
+        out.writeInt(random().nextInt());
+        for (int i = 0; i < ForUtil.BLOCK_SIZE; ++i) {
+          out.writeLong(random().nextInt());
+        }
+      }
+      VectorizationProvider vectorizationProvider = VectorizationProvider.lookup(true);
+      try (IndexInput in = dir.openInput("tests.bin", IOContext.DEFAULT)) {
+        long[] expectedB = new long[ForUtil.BLOCK_SIZE];
+        long[] expectedC = new long[ForUtil.BLOCK_SIZE];
+        long[] actualB = new long[ForUtil.BLOCK_SIZE];
+        long[] actualC = new long[ForUtil.BLOCK_SIZE];
+        for (int iter = 0; iter < iterations; ++iter) {
+          // Initialize arrays with random content.
+          for (int i = 0; i < expectedB.length; ++i) {
+            expectedB[i] = random().nextLong();
+            actualB[i] = expectedB[i];
+            expectedC[i] = random().nextLong();
+            actualC[i] = expectedC[i];
+          }
+          int count = TestUtil.nextInt(random(), 1, 64);
+          int bShift = TestUtil.nextInt(random(), 1, 31);
+          long bMask = random().nextLong();
+          int cIndex = random().nextInt(64);
+          long cMask = random().nextLong();
+          long startFP = random().nextInt(4);
+
+          // Work on a slice that has just the right number of bytes to make the test fail with an
+          // index-out-of-bounds in case the implementation reads more than the allowed number of
+          // padding bytes.
+          IndexInput slice = in.slice("test", 0, startFP + count * Long.BYTES);
+
+          PostingDecodingUtil defaultUtil = new DefaultPostingDecodingUtil(slice);
+          PostingDecodingUtil optimizedUtil = vectorizationProvider.newPostingDecodingUtil(slice);
+
+          slice.seek(startFP);
+          defaultUtil.splitLongs(count, expectedB, bShift, bMask, expectedC, cIndex, cMask);
+          long expectedEndFP = slice.getFilePointer();
+          slice.seek(startFP);
+          optimizedUtil.splitLongs(count, actualB, bShift, bMask, actualC, cIndex, cMask);
+          assertEquals(expectedEndFP, slice.getFilePointer());
+          assertArrayEquals(expectedB, actualB);
+          assertArrayEquals(expectedC, actualC);
+        }
+      }
+    }
+  }
+}