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