96 lines
3.9 KiB
Java
96 lines
3.9 KiB
Java
/*
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* Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 2024, Rivos Inc. 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.
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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 compiler.lib.golden;
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import jdk.internal.math.DoubleConsts;
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import jdk.internal.math.FloatConsts;
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public class GoldenRound {
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public static int golden_round(float a) {
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// below code is copied from java.base/share/classes/java/lang/Math.java
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// public static int round(float a) { ... }
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int intBits = Float.floatToRawIntBits(a);
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int biasedExp = (intBits & FloatConsts.EXP_BIT_MASK)
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>> (FloatConsts.SIGNIFICAND_WIDTH - 1);
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int shift = (FloatConsts.SIGNIFICAND_WIDTH - 2
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+ FloatConsts.EXP_BIAS) - biasedExp;
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if ((shift & -32) == 0) { // shift >= 0 && shift < 32
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// a is a finite number such that pow(2,-32) <= ulp(a) < 1
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int r = ((intBits & FloatConsts.SIGNIF_BIT_MASK)
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| (FloatConsts.SIGNIF_BIT_MASK + 1));
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if (intBits < 0) {
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r = -r;
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}
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// In the comments below each Java expression evaluates to the value
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// the corresponding mathematical expression:
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// (r) evaluates to a / ulp(a)
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// (r >> shift) evaluates to floor(a * 2)
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// ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
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// (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
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return ((r >> shift) + 1) >> 1;
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} else {
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// a is either
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// - a finite number with abs(a) < exp(2,FloatConsts.SIGNIFICAND_WIDTH-32) < 1/2
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// - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
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// - an infinity or NaN
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return (int) a;
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}
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}
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public static long golden_round(double a) {
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// below code is copied from java.base/share/classes/java/lang/Math.java
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// public static int round(double a) { ... }
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long longBits = Double.doubleToRawLongBits(a);
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long biasedExp = (longBits & DoubleConsts.EXP_BIT_MASK)
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>> (DoubleConsts.SIGNIFICAND_WIDTH - 1);
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long shift = (DoubleConsts.SIGNIFICAND_WIDTH - 2
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+ DoubleConsts.EXP_BIAS) - biasedExp;
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if ((shift & -64) == 0) { // shift >= 0 && shift < 64
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// a is a finite number such that pow(2,-64) <= ulp(a) < 1
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long r = ((longBits & DoubleConsts.SIGNIF_BIT_MASK)
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| (DoubleConsts.SIGNIF_BIT_MASK + 1));
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if (longBits < 0) {
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r = -r;
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}
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// In the comments below each Java expression evaluates to the value
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// the corresponding mathematical expression:
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// (r) evaluates to a / ulp(a)
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// (r >> shift) evaluates to floor(a * 2)
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// ((r >> shift) + 1) evaluates to floor((a + 1/2) * 2)
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// (((r >> shift) + 1) >> 1) evaluates to floor(a + 1/2)
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return ((r >> shift) + 1) >> 1;
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} else {
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// a is either
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// - a finite number with abs(a) < exp(2,DoubleConsts.SIGNIFICAND_WIDTH-64) < 1/2
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// - a finite number with ulp(a) >= 1 and hence a is a mathematical integer
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// - an infinity or NaN
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return (long) a;
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}
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}
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}
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