--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/ArraysSupport.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,545 @@
+/*
+ * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.util;
+
+import jdk.internal.HotSpotIntrinsicCandidate;
+import jdk.internal.misc.Unsafe;
+
+/**
+ * Utility methods to find a mismatch between two primitive arrays.
+ *
+ * <p>Array equality and lexicographical comparison can be built on top of
+ * array mismatch functionality.
+ *
+ * <p>The mismatch method implementation, {@link #vectorizedMismatch}, leverages
+ * vector-based techniques to access and compare the contents of two arrays.
+ * The Java implementation uses {@code Unsafe.getLongUnaligned} to access the
+ * content of an array, thus access is supported on platforms that do not
+ * support unaligned access. For a byte[] array, 8 bytes (64 bits) can be
+ * accessed and compared as a unit rather than individually, which increases
+ * the performance when the method is compiled by the HotSpot VM. On supported
+ * platforms the mismatch implementation is intrinsified to leverage SIMD
+ * instructions. So for a byte[] array, 16 bytes (128 bits), 32 bytes
+ * (256 bits), and perhaps in the future even 64 bytes (512 bits), platform
+ * permitting, can be accessed and compared as a unit, which further increases
+ * the performance over the Java implementation.
+ *
+ * <p>None of the mismatch methods perform array bounds checks. It is the
+ * responsibility of the caller (direct or otherwise) to perform such checks
+ * before calling this method.
+ */
+class ArraysSupport {
+ static final Unsafe U = Unsafe.getUnsafe();
+
+ private static final boolean BIG_ENDIAN = U.isBigEndian();
+
+ private static final int LOG2_ARRAY_BOOLEAN_INDEX_SCALE = exactLog2(Unsafe.ARRAY_BOOLEAN_INDEX_SCALE);
+ private static final int LOG2_ARRAY_BYTE_INDEX_SCALE = exactLog2(Unsafe.ARRAY_BYTE_INDEX_SCALE);
+ private static final int LOG2_ARRAY_CHAR_INDEX_SCALE = exactLog2(Unsafe.ARRAY_CHAR_INDEX_SCALE);
+ private static final int LOG2_ARRAY_SHORT_INDEX_SCALE = exactLog2(Unsafe.ARRAY_SHORT_INDEX_SCALE);
+ private static final int LOG2_ARRAY_INT_INDEX_SCALE = exactLog2(Unsafe.ARRAY_INT_INDEX_SCALE);
+ private static final int LOG2_ARRAY_LONG_INDEX_SCALE = exactLog2(Unsafe.ARRAY_LONG_INDEX_SCALE);
+ private static final int LOG2_ARRAY_FLOAT_INDEX_SCALE = exactLog2(Unsafe.ARRAY_FLOAT_INDEX_SCALE);
+ private static final int LOG2_ARRAY_DOUBLE_INDEX_SCALE = exactLog2(Unsafe.ARRAY_DOUBLE_INDEX_SCALE);
+
+ private static final int LOG2_BYTE_BIT_SIZE = exactLog2(Byte.SIZE);
+
+ private static int exactLog2(int scale) {
+ if ((scale & (scale - 1)) != 0)
+ throw new Error("data type scale not a power of two");
+ return Integer.numberOfTrailingZeros(scale);
+ }
+
+ private ArraysSupport() {}
+
+ /**
+ * Find the relative index of the first mismatching pair of elements in two
+ * primitive arrays of the same component type. Pairs of elements will be
+ * tested in order relative to given offsets into both arrays.
+ *
+ * <p>This method does not perform type checks or bounds checks. It is the
+ * responsibility of the caller to perform such checks before calling this
+ * method.
+ *
+ * <p>The given offsets, in bytes, need not be aligned according to the
+ * given log<sub>2</sub> size the array elements. More specifically, an
+ * offset modulus the size need not be zero.
+ *
+ * @param a the first array to be tested for mismatch, or {@code null} for
+ * direct memory access
+ * @param aOffset the relative offset, in bytes, from the base address of
+ * the first array to test from, otherwise if the first array is
+ * {@code null}, an absolute address pointing to the first element to test.
+ * @param b the second array to be tested for mismatch, or {@code null} for
+ * direct memory access
+ * @param bOffset the relative offset, in bytes, from the base address of
+ * the second array to test from, otherwise if the second array is
+ * {@code null}, an absolute address pointing to the first element to test.
+ * @param length the number of array elements to test
+ * @param log2ArrayIndexScale log<sub>2</sub> of the array index scale, that
+ * corresponds to the size, in bytes, of an array element.
+ * @return if a mismatch is found a relative index, between 0 (inclusive)
+ * and {@code length} (exclusive), of the first mismatching pair of elements
+ * in the two arrays. Otherwise, if a mismatch is not found the bitwise
+ * compliment of the number of remaining pairs of elements to be checked in
+ * the tail of the two arrays.
+ */
+ @HotSpotIntrinsicCandidate
+ static int vectorizedMismatch(Object a, long aOffset,
+ Object b, long bOffset,
+ int length,
+ int log2ArrayIndexScale) {
+ // assert a.getClass().isArray();
+ // assert b.getClass().isArray();
+ // assert 0 <= length <= sizeOf(a)
+ // assert 0 <= length <= sizeOf(b)
+ // assert 0 <= log2ArrayIndexScale <= 3
+
+ int log2ValuesPerWidth = LOG2_ARRAY_LONG_INDEX_SCALE - log2ArrayIndexScale;
+ int wi = 0;
+ for (; wi < length >> log2ValuesPerWidth; wi++) {
+ long bi = ((long) wi) << LOG2_ARRAY_LONG_INDEX_SCALE;
+ long av = U.getLongUnaligned(a, aOffset + bi);
+ long bv = U.getLongUnaligned(b, bOffset + bi);
+ if (av != bv) {
+ long x = av ^ bv;
+ int o = BIG_ENDIAN
+ ? Long.numberOfLeadingZeros(x) >> (LOG2_BYTE_BIT_SIZE + log2ArrayIndexScale)
+ : Long.numberOfTrailingZeros(x) >> (LOG2_BYTE_BIT_SIZE + log2ArrayIndexScale);
+ return (wi << log2ValuesPerWidth) + o;
+ }
+ }
+
+ // Calculate the tail of remaining elements to check
+ int tail = length - (wi << log2ValuesPerWidth);
+
+ if (log2ArrayIndexScale < LOG2_ARRAY_INT_INDEX_SCALE) {
+ int wordTail = 1 << (LOG2_ARRAY_INT_INDEX_SCALE - log2ArrayIndexScale);
+ // Handle 4 bytes or 2 chars in the tail using int width
+ if (tail >= wordTail) {
+ long bi = ((long) wi) << LOG2_ARRAY_LONG_INDEX_SCALE;
+ int av = U.getIntUnaligned(a, aOffset + bi);
+ int bv = U.getIntUnaligned(b, bOffset + bi);
+ if (av != bv) {
+ int x = av ^ bv;
+ int o = BIG_ENDIAN
+ ? Integer.numberOfLeadingZeros(x) >> (LOG2_BYTE_BIT_SIZE + log2ArrayIndexScale)
+ : Integer.numberOfTrailingZeros(x) >> (LOG2_BYTE_BIT_SIZE + log2ArrayIndexScale);
+ return (wi << log2ValuesPerWidth) + o;
+ }
+ tail -= wordTail;
+ }
+ return ~tail;
+ }
+ else {
+ return ~tail;
+ }
+ }
+
+ // Booleans
+ // Each boolean element takes up one byte
+
+ static int mismatch(boolean[] a,
+ boolean[] b,
+ int length) {
+ int i = 0;
+ if (length > 7) {
+ i = vectorizedMismatch(
+ a, Unsafe.ARRAY_BOOLEAN_BASE_OFFSET,
+ b, Unsafe.ARRAY_BOOLEAN_BASE_OFFSET,
+ length, LOG2_ARRAY_BOOLEAN_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[i] != b[i])
+ return i;
+ }
+ return -1;
+ }
+
+ static int mismatch(boolean[] a, int aFromIndex,
+ boolean[] b, int bFromIndex,
+ int length) {
+ int i = 0;
+ if (length > 7) {
+ int aOffset = Unsafe.ARRAY_BOOLEAN_BASE_OFFSET + aFromIndex;
+ int bOffset = Unsafe.ARRAY_BOOLEAN_BASE_OFFSET + bFromIndex;
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_BOOLEAN_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[aFromIndex + i] != b[bFromIndex + i])
+ return i;
+ }
+ return -1;
+ }
+
+
+ // Bytes
+
+ /**
+ * Find the index of a mismatch between two arrays.
+ *
+ * <p>This method does not perform bounds checks. It is the responsibility
+ * of the caller to perform such bounds checks before calling this method.
+ *
+ * @param a the first array to be tested for a mismatch
+ * @param b the second array to be tested for a mismatch
+ * @param length the number of bytes from each array to check
+ * @return the index of a mismatch between the two arrays, otherwise -1 if
+ * no mismatch. The index will be within the range of (inclusive) 0 to
+ * (exclusive) the smaller of the two array lengths.
+ */
+ static int mismatch(byte[] a,
+ byte[] b,
+ int length) {
+ // ISSUE: defer to index receiving methods if performance is good
+ // assert length <= a.length
+ // assert length <= b.length
+
+ int i = 0;
+ if (length > 7) {
+ i = vectorizedMismatch(
+ a, Unsafe.ARRAY_BYTE_BASE_OFFSET,
+ b, Unsafe.ARRAY_BYTE_BASE_OFFSET,
+ length, LOG2_ARRAY_BYTE_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ // Align to tail
+ i = length - ~i;
+// assert i >= 0 && i <= 7;
+ }
+ // Tail < 8 bytes
+ for (; i < length; i++) {
+ if (a[i] != b[i])
+ return i;
+ }
+ return -1;
+ }
+
+ /**
+ * Find the relative index of a mismatch between two arrays starting from
+ * given indexes.
+ *
+ * <p>This method does not perform bounds checks. It is the responsibility
+ * of the caller to perform such bounds checks before calling this method.
+ *
+ * @param a the first array to be tested for a mismatch
+ * @param aFromIndex the index of the first element (inclusive) in the first
+ * array to be compared
+ * @param b the second array to be tested for a mismatch
+ * @param bFromIndex the index of the first element (inclusive) in the
+ * second array to be compared
+ * @param length the number of bytes from each array to check
+ * @return the relative index of a mismatch between the two arrays,
+ * otherwise -1 if no mismatch. The index will be within the range of
+ * (inclusive) 0 to (exclusive) the smaller of the two array bounds.
+ */
+ static int mismatch(byte[] a, int aFromIndex,
+ byte[] b, int bFromIndex,
+ int length) {
+ // assert 0 <= aFromIndex < a.length
+ // assert 0 <= aFromIndex + length <= a.length
+ // assert 0 <= bFromIndex < b.length
+ // assert 0 <= bFromIndex + length <= b.length
+ // assert length >= 0
+
+ int i = 0;
+ if (length > 7) {
+ int aOffset = Unsafe.ARRAY_BYTE_BASE_OFFSET + aFromIndex;
+ int bOffset = Unsafe.ARRAY_BYTE_BASE_OFFSET + bFromIndex;
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_BYTE_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[aFromIndex + i] != b[bFromIndex + i])
+ return i;
+ }
+ return -1;
+ }
+
+
+ // Chars
+
+ static int mismatch(char[] a,
+ char[] b,
+ int length) {
+ int i = 0;
+ if (length > 3) {
+ i = vectorizedMismatch(
+ a, Unsafe.ARRAY_CHAR_BASE_OFFSET,
+ b, Unsafe.ARRAY_CHAR_BASE_OFFSET,
+ length, LOG2_ARRAY_CHAR_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[i] != b[i])
+ return i;
+ }
+ return -1;
+ }
+
+ static int mismatch(char[] a, int aFromIndex,
+ char[] b, int bFromIndex,
+ int length) {
+ int i = 0;
+ if (length > 3) {
+ int aOffset = Unsafe.ARRAY_CHAR_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_CHAR_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_CHAR_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_CHAR_INDEX_SCALE);
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_CHAR_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[aFromIndex + i] != b[bFromIndex + i])
+ return i;
+ }
+ return -1;
+ }
+
+
+ // Shorts
+
+ static int mismatch(short[] a,
+ short[] b,
+ int length) {
+ int i = 0;
+ if (length > 3) {
+ i = vectorizedMismatch(
+ a, Unsafe.ARRAY_SHORT_BASE_OFFSET,
+ b, Unsafe.ARRAY_SHORT_BASE_OFFSET,
+ length, LOG2_ARRAY_SHORT_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[i] != b[i])
+ return i;
+ }
+ return -1;
+ }
+
+ static int mismatch(short[] a, int aFromIndex,
+ short[] b, int bFromIndex,
+ int length) {
+ int i = 0;
+ if (length > 3) {
+ int aOffset = Unsafe.ARRAY_SHORT_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_SHORT_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_SHORT_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_SHORT_INDEX_SCALE);
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_SHORT_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[aFromIndex + i] != b[bFromIndex + i])
+ return i;
+ }
+ return -1;
+ }
+
+
+ // Ints
+
+ static int mismatch(int[] a,
+ int[] b,
+ int length) {
+ int i = 0;
+ if (length > 1) {
+ i = vectorizedMismatch(
+ a, Unsafe.ARRAY_INT_BASE_OFFSET,
+ b, Unsafe.ARRAY_INT_BASE_OFFSET,
+ length, LOG2_ARRAY_INT_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[i] != b[i])
+ return i;
+ }
+ return -1;
+ }
+
+ static int mismatch(int[] a, int aFromIndex,
+ int[] b, int bFromIndex,
+ int length) {
+ int i = 0;
+ if (length > 1) {
+ int aOffset = Unsafe.ARRAY_INT_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_INT_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_INT_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_INT_INDEX_SCALE);
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_INT_INDEX_SCALE);
+ if (i >= 0)
+ return i;
+ i = length - ~i;
+ }
+ for (; i < length; i++) {
+ if (a[aFromIndex + i] != b[bFromIndex + i])
+ return i;
+ }
+ return -1;
+ }
+
+
+ // Floats
+
+ static int mismatch(float[] a,
+ float[] b,
+ int length) {
+ return mismatch(a, 0, b, 0, length);
+ }
+
+ static int mismatch(float[] a, int aFromIndex,
+ float[] b, int bFromIndex,
+ int length) {
+ int i = 0;
+ if (length > 1) {
+ int aOffset = Unsafe.ARRAY_FLOAT_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_FLOAT_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_FLOAT_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_FLOAT_INDEX_SCALE);
+ i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_FLOAT_INDEX_SCALE);
+ // Mismatched
+ if (i >= 0) {
+ // Check if mismatch is not associated with two NaN values
+ if (!Float.isNaN(a[aFromIndex + i]) || !Float.isNaN(b[bFromIndex + i]))
+ return i;
+
+ // Mismatch on two different NaN values that are normalized to match
+ // Fall back to slow mechanism
+ // ISSUE: Consider looping over vectorizedMismatch adjusting ranges
+ // However, requires that returned value be relative to input ranges
+ i++;
+ }
+ // Matched
+ else {
+ i = length - ~i;
+ }
+ }
+ for (; i < length; i++) {
+ if (Float.floatToIntBits(a[aFromIndex + i]) != Float.floatToIntBits(b[bFromIndex + i]))
+ return i;
+ }
+ return -1;
+ }
+
+ // 64 bit sizes
+
+ // Long
+
+ static int mismatch(long[] a,
+ long[] b,
+ int length) {
+ if (length == 0) {
+ return -1;
+ }
+ int i = vectorizedMismatch(
+ a, Unsafe.ARRAY_LONG_BASE_OFFSET,
+ b, Unsafe.ARRAY_LONG_BASE_OFFSET,
+ length, LOG2_ARRAY_LONG_INDEX_SCALE);
+ return i >= 0 ? i : -1;
+ }
+
+ static int mismatch(long[] a, int aFromIndex,
+ long[] b, int bFromIndex,
+ int length) {
+ if (length == 0) {
+ return -1;
+ }
+ int aOffset = Unsafe.ARRAY_LONG_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_LONG_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_LONG_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_LONG_INDEX_SCALE);
+ int i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_LONG_INDEX_SCALE);
+ return i >= 0 ? i : -1;
+ }
+
+
+ // Double
+
+ static int mismatch(double[] a,
+ double[] b,
+ int length) {
+ return mismatch(a, 0, b, 0, length);
+ }
+
+ static int mismatch(double[] a, int aFromIndex,
+ double[] b, int bFromIndex,
+ int length) {
+ if (length == 0) {
+ return -1;
+ }
+ int aOffset = Unsafe.ARRAY_DOUBLE_BASE_OFFSET + (aFromIndex << LOG2_ARRAY_DOUBLE_INDEX_SCALE);
+ int bOffset = Unsafe.ARRAY_DOUBLE_BASE_OFFSET + (bFromIndex << LOG2_ARRAY_DOUBLE_INDEX_SCALE);
+ int i = vectorizedMismatch(
+ a, aOffset,
+ b, bOffset,
+ length, LOG2_ARRAY_DOUBLE_INDEX_SCALE);
+ if (i >= 0) {
+ // Check if mismatch is not associated with two NaN values
+ if (!Double.isNaN(a[aFromIndex + i]) || !Double.isNaN(b[bFromIndex + i]))
+ return i;
+
+ // Mismatch on two different NaN values that are normalized to match
+ // Fall back to slow mechanism
+ // ISSUE: Consider looping over vectorizedMismatch adjusting ranges
+ // However, requires that returned value be relative to input ranges
+ i++;
+ for (; i < length; i++) {
+ if (Double.doubleToLongBits(a[aFromIndex + i]) != Double.doubleToLongBits(b[bFromIndex + i]))
+ return i;
+ }
+ }
+
+ return -1;
+ }
+}