6800154: Add comments to long_by_long_mulhi() for better understandability
This patch adds a comment pointing to the Hacker's Delight version of the algorithm plus a verbatim copy of it. Furthermore it adds inline comments. Reviewed-by: kvn, jrose
This commit is contained in:
Christian Thalinger
parent
2f2589d2dc
commit
a2ed00b650
@ -1,5 +1,5 @@
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/*
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* Copyright 1997-2008 Sun Microsystems, Inc. All Rights Reserved.
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* Copyright 1997-2009 Sun Microsystems, 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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@ -244,42 +244,73 @@ static bool magic_long_divide_constants(jlong d, jlong &M, jint &s) {
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//---------------------long_by_long_mulhi--------------------------------------
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// Generate ideal node graph for upper half of a 64 bit x 64 bit multiplication
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static Node *long_by_long_mulhi( PhaseGVN *phase, Node *dividend, jlong magic_const) {
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static Node* long_by_long_mulhi(PhaseGVN* phase, Node* dividend, jlong magic_const) {
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// If the architecture supports a 64x64 mulhi, there is
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// no need to synthesize it in ideal nodes.
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if (Matcher::has_match_rule(Op_MulHiL)) {
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Node *v = phase->longcon(magic_const);
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Node* v = phase->longcon(magic_const);
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return new (phase->C, 3) MulHiLNode(dividend, v);
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}
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// Taken from Hacker's Delight, Fig. 8-2. Multiply high signed.
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// (http://www.hackersdelight.org/HDcode/mulhs.c)
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//
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// int mulhs(int u, int v) {
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// unsigned u0, v0, w0;
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// int u1, v1, w1, w2, t;
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//
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// u0 = u & 0xFFFF; u1 = u >> 16;
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// v0 = v & 0xFFFF; v1 = v >> 16;
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// w0 = u0*v0;
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// t = u1*v0 + (w0 >> 16);
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// w1 = t & 0xFFFF;
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// w2 = t >> 16;
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// w1 = u0*v1 + w1;
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// return u1*v1 + w2 + (w1 >> 16);
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// }
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//
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// Note: The version above is for 32x32 multiplications, while the
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// following inline comments are adapted to 64x64.
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const int N = 64;
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Node *u_hi = phase->transform(new (phase->C, 3) RShiftLNode(dividend, phase->intcon(N / 2)));
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Node *u_lo = phase->transform(new (phase->C, 3) AndLNode(dividend, phase->longcon(0xFFFFFFFF)));
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// u0 = u & 0xFFFFFFFF; u1 = u >> 32;
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Node* u0 = phase->transform(new (phase->C, 3) AndLNode(dividend, phase->longcon(0xFFFFFFFF)));
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Node* u1 = phase->transform(new (phase->C, 3) RShiftLNode(dividend, phase->intcon(N / 2)));
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Node *v_hi = phase->longcon(magic_const >> N/2);
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Node *v_lo = phase->longcon(magic_const & 0XFFFFFFFF);
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// v0 = v & 0xFFFFFFFF; v1 = v >> 32;
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Node* v0 = phase->longcon(magic_const & 0xFFFFFFFF);
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Node* v1 = phase->longcon(magic_const >> (N / 2));
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Node *hihi_product = phase->transform(new (phase->C, 3) MulLNode(u_hi, v_hi));
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Node *hilo_product = phase->transform(new (phase->C, 3) MulLNode(u_hi, v_lo));
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Node *lohi_product = phase->transform(new (phase->C, 3) MulLNode(u_lo, v_hi));
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Node *lolo_product = phase->transform(new (phase->C, 3) MulLNode(u_lo, v_lo));
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// w0 = u0*v0;
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Node* w0 = phase->transform(new (phase->C, 3) MulLNode(u0, v0));
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Node *t1 = phase->transform(new (phase->C, 3) URShiftLNode(lolo_product, phase->intcon(N / 2)));
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Node *t2 = phase->transform(new (phase->C, 3) AddLNode(hilo_product, t1));
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// t = u1*v0 + (w0 >> 32);
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Node* u1v0 = phase->transform(new (phase->C, 3) MulLNode(u1, v0));
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Node* temp = phase->transform(new (phase->C, 3) URShiftLNode(w0, phase->intcon(N / 2)));
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Node* t = phase->transform(new (phase->C, 3) AddLNode(u1v0, temp));
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// Construct both t3 and t4 before transforming so t2 doesn't go dead
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// prematurely.
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Node *t3 = new (phase->C, 3) RShiftLNode(t2, phase->intcon(N / 2));
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Node *t4 = new (phase->C, 3) AndLNode(t2, phase->longcon(0xFFFFFFFF));
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t3 = phase->transform(t3);
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t4 = phase->transform(t4);
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// w1 = t & 0xFFFFFFFF;
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Node* w1 = new (phase->C, 3) AndLNode(t, phase->longcon(0xFFFFFFFF));
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Node *t5 = phase->transform(new (phase->C, 3) AddLNode(t4, lohi_product));
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Node *t6 = phase->transform(new (phase->C, 3) RShiftLNode(t5, phase->intcon(N / 2)));
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Node *t7 = phase->transform(new (phase->C, 3) AddLNode(t3, hihi_product));
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// w2 = t >> 32;
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Node* w2 = new (phase->C, 3) RShiftLNode(t, phase->intcon(N / 2));
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return new (phase->C, 3) AddLNode(t7, t6);
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// 6732154: Construct both w1 and w2 before transforming, so t
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// doesn't go dead prematurely.
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w1 = phase->transform(w1);
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w2 = phase->transform(w2);
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// w1 = u0*v1 + w1;
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Node* u0v1 = phase->transform(new (phase->C, 3) MulLNode(u0, v1));
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w1 = phase->transform(new (phase->C, 3) AddLNode(u0v1, w1));
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// return u1*v1 + w2 + (w1 >> 32);
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Node* u1v1 = phase->transform(new (phase->C, 3) MulLNode(u1, v1));
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Node* temp1 = phase->transform(new (phase->C, 3) AddLNode(u1v1, w2));
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Node* temp2 = phase->transform(new (phase->C, 3) RShiftLNode(w1, phase->intcon(N / 2)));
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return new (phase->C, 3) AddLNode(temp1, temp2);
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}
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220
hotspot/test/compiler/6603011/Test.java
Normal file
220
hotspot/test/compiler/6603011/Test.java
Normal file
@ -0,0 +1,220 @@
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/*
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* Copyright 2009 Sun Microsystems, 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*/
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/**
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* @test
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* @bug 6603011
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* @summary long/int division by constant
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*
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* @run main/othervm -Xcomp -Xbatch -XX:-Inline Test
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*/
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//
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// -XX:-Inline is essential to this test so that verification functions
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// divi, modi, divl and modl generate "plain" divides.
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// -Xcomp -Xbatch are also useful to ensure the full range of
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// dividend and divisor combinations are tested
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//
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import java.net.*;
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class s {
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static int divi(int dividend, int divisor) { return dividend / divisor; }
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static int modi(int dividend, int divisor) { return dividend % divisor; }
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static long divl(long dividend, long divisor) { return dividend / divisor; }
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static long modl(long dividend, long divisor) { return dividend % divisor; }
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}
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public class Test implements Runnable {
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// Report verbose messages on failure; turn off to suppress
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// too much output with gross numbers of failures.
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static final boolean VERBOSE = true;
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// Initailize DIVISOR so that it is final in this class.
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static final int DIVISOR;
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static {
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int value = 0;
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try {
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value = Integer.decode(System.getProperty("divisor"));
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} catch (Throwable e) {
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}
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DIVISOR = value;
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}
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// The methods of interest. We want the JIT to compile these
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// and convert the divide into a multiply.
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public int divbyI (int dividend) { return dividend / DIVISOR; }
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public int modbyI (int dividend) { return dividend % DIVISOR; }
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public long divbyL (long dividend) { return dividend / DIVISOR; }
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public long modbyL (long dividend) { return dividend % DIVISOR; }
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public int divisor() { return DIVISOR; }
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public boolean checkI (int dividend) {
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int quo = divbyI(dividend);
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int rem = modbyI(dividend);
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int quo0 = s.divi(dividend, divisor());
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int rem0 = s.modi(dividend, divisor());
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if (quo != quo0 || rem != rem0) {
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if (VERBOSE) {
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System.out.println("Computed: " + dividend + " / " + divisor() + " = " +
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quo + ", " + dividend + " % " + divisor() + " = " + rem );
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System.out.println("expected: " + dividend + " / " + divisor() + " = " +
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quo0 + ", " + dividend + " % " + divisor() + " = " + rem0);
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// Report sign of rem failure
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if (rem != 0 && (rem ^ dividend) < 0) {
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System.out.println(" rem & dividend have different signs");
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}
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// Report range of rem failure
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if (java.lang.Math.abs(rem) >= java.lang.Math.abs(divisor())) {
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System.out.println(" remainder out of range");
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}
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// Report quo/rem identity relationship failure
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if ((quo * divisor()) + rem != dividend) {
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System.out.println(" quotien/remainder invariant broken");
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}
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}
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return false;
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}
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return true;
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}
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public boolean checkL (long dividend) {
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long quo = divbyL(dividend);
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long rem = modbyL(dividend);
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long quo0 = s.divl(dividend, divisor());
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long rem0 = s.modl(dividend, divisor());
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if (quo != quo0 || rem != rem0) {
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if (VERBOSE) {
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System.out.println(" " + dividend + " / " + divisor() + " = " +
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quo + ", " + dividend + " % " + divisor() + " = " + rem);
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// Report sign of rem failure
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if (rem != 0 && (rem ^ dividend) < 0) {
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System.out.println(" rem & dividend have different signs");
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}
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// Report range of rem failure
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if (java.lang.Math.abs(rem) >= java.lang.Math.abs(divisor())) {
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System.out.println(" remainder out of range");
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}
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// Report quo/rem identity relationship failure
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if ((quo * divisor()) + rem != dividend) {
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System.out.println(" (" + quo + " * " + divisor() + ") + " + rem + " != "
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+ dividend);
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}
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}
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return false;
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}
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return true;
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}
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public void run() {
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// Don't try to divide by zero
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if (divisor() == 0) return;
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// Range of dividends to check. Try dividends from start to end
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// inclusive, as well as variations on those values as shifted
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// left.
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int start = -1024;
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int end = 1024;
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// Test int division using a variety of dividends.
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int wrong = 0;
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int total = 0;
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outerloop:
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for (int i = start; i <= end; i++) {
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for (int s = 0; s < 32; s += 4) {
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total++;
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int dividend = i << s;
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if (!checkI(dividend)) {
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wrong++;
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// Stop on the first failure
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// break outerloop;
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}
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}
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}
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if (wrong > 0) {
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System.out.println("divisor " + divisor() + ": " +
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wrong + "/" + total + " wrong int divisions");
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}
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// Test long division using a variety of dividends.
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wrong = 0;
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total = 0;
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outerloop:
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for (int i = start; i <= end; i++) {
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for (int s = 0; s < 64; s += 4) {
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total++;
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long dividend = i << s;
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if (!checkL(dividend)) {
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wrong++;
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// Stop on the first failure
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// break outerloop;
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}
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}
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}
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if (wrong > 0) {
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System.out.println("divisor " + divisor() + ": " +
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wrong + "/" + total + " wrong long divisions");
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}
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}
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// Reload this class with the "divisor" property set to the input parameter.
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// This allows the JIT to see q.DIVISOR as a final constant, and change
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// any divisions or mod operations into multiplies.
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public static void test_divisor(int divisor,
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URLClassLoader apploader) throws Exception {
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System.setProperty("divisor", "" + divisor);
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ClassLoader loader = new URLClassLoader(apploader.getURLs(),
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apploader.getParent());
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Class c = loader.loadClass("Test");
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Runnable r = (Runnable)c.newInstance();
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r.run();
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}
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public static void main(String[] args) throws Exception {
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Class cl = Class.forName("Test");
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URLClassLoader apploader = (URLClassLoader)cl.getClassLoader();
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// Test every divisor between -100 and 100.
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for (int i = -100; i <= 100; i++) {
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test_divisor(i, apploader);
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}
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// Try a few divisors outside the typical range.
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// The values below have been observed in rt.jar.
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test_divisor(101, apploader);
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test_divisor(400, apploader);
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test_divisor(1000, apploader);
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test_divisor(3600, apploader);
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test_divisor(9973, apploader);
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test_divisor(86400, apploader);
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test_divisor(1000000, apploader);
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}
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}
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109
hotspot/test/compiler/6800154/Test6800154.java
Normal file
109
hotspot/test/compiler/6800154/Test6800154.java
Normal file
@ -0,0 +1,109 @@
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/*
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* Copyright 2009 Sun Microsystems, 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
|
||||
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
|
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* have any questions.
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*/
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/**
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* @test
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* @bug 6800154
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* @summary Add comments to long_by_long_mulhi() for better understandability
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*
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* @run main/othervm -Xcomp -XX:CompileOnly=Test6800154.divcomp Test6800154
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*/
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import java.net.URLClassLoader;
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public class Test6800154 implements Runnable {
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static final long[] DIVIDENDS = {
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0,
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1,
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2,
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1423487,
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4444441,
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4918923241323L,
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-1,
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-24351,
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0x3333,
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0x0000000080000000L,
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0x7fffffffffffffffL,
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0x8000000000000000L
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};
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static final long[] DIVISORS = {
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1,
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2,
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17,
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12342,
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24123,
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143444,
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123444442344L,
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-1,
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-2,
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-4423423234231423L,
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0x0000000080000000L,
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0x7fffffffffffffffL,
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0x8000000000000000L
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};
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// Initialize DIVISOR so that it is final in this class.
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static final long DIVISOR;
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static {
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long value = 0;
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try {
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value = Long.decode(System.getProperty("divisor"));
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} catch (Throwable e) {
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}
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DIVISOR = value;
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}
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public static void main(String[] args) throws Exception
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{
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Class cl = Class.forName("Test6800154");
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URLClassLoader apploader = (URLClassLoader) cl.getClassLoader();
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// Iterate over all divisors.
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for (int i = 0; i < DIVISORS.length; i++) {
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System.setProperty("divisor", "" + DIVISORS[i]);
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ClassLoader loader = new URLClassLoader(apploader.getURLs(), apploader.getParent());
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Class c = loader.loadClass("Test6800154");
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Runnable r = (Runnable) c.newInstance();
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r.run();
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}
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}
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public void run()
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{
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// Iterate over all dividends.
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for (int i = 0; i < DIVIDENDS.length; i++) {
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long dividend = DIVIDENDS[i];
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long expected = divint(dividend);
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long result = divcomp(dividend);
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if (result != expected)
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throw new InternalError(dividend + " / " + DIVISOR + " failed: " + result + " != " + expected);
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}
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}
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static long divint(long a) { return a / DIVISOR; }
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static long divcomp(long a) { return a / DIVISOR; }
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||||
}
|
||||
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Reference in New Issue
Block a user