infernap12/jdk
1
0
Fork 0
mirror of https://github.com/openjdk/jdk.git synced 2026-07-28 11:53:09 +00:00
Code Issues Packages Projects Releases Wiki Activity

8349637: Integer.numberOfLeadingZeros outputs incorrectly in certain cases

Browse Source 
Reviewed-by: thartmann, qamai, jbhateja
This commit is contained in:
Jasmine Karthikeyan 2025-03-03 05:18:55 +00:00
parent 93c878455b
commit 3657e92ead
3 changed files with 222 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp
View File

@ -6227,15 +6227,21 @@ void C2_MacroAssembler::vector_count_leading_zeros_int_avx(XMMRegister dst, XMMR
// Since IEEE 754 floating point format represents mantissa in 1.0 format
// hence biased exponent can be used to compute leading zero count as per
// following formula:-
// LZCNT = 32 - (biased_exp - 127)
// LZCNT = 31 - (biased_exp - 127)
// Special handling has been introduced for Zero, Max_Int and -ve source values.
// Broadcast 0xFF
vpcmpeqd(xtmp1, xtmp1, xtmp1, vec_enc);
vpsrld(xtmp1, xtmp1, 24, vec_enc);
// Remove the bit to the right of the highest set bit ensuring that the conversion to float cannot round up to a higher
// power of 2, which has a higher exponent than the input. This transformation is valid as only the highest set bit
// contributes to the leading number of zeros.
vpsrld(xtmp2, src, 1, vec_enc);
vpandn(xtmp3, xtmp2, src, vec_enc);
// Extract biased exponent.
vcvtdq2ps(dst, src, vec_enc);
vcvtdq2ps(dst, xtmp3, vec_enc);
vpsrld(dst, dst, 23, vec_enc);
vpand(dst, dst, xtmp1, vec_enc);
@ -6244,7 +6250,7 @@ void C2_MacroAssembler::vector_count_leading_zeros_int_avx(XMMRegister dst, XMMR
// Exponent = biased_exp - 127
vpsubd(dst, dst, xtmp1, vec_enc);
// Exponent = Exponent + 1
// Exponent_plus_one = Exponent + 1
vpsrld(xtmp3, xtmp1, 6, vec_enc);
vpaddd(dst, dst, xtmp3, vec_enc);
@ -6257,7 +6263,7 @@ void C2_MacroAssembler::vector_count_leading_zeros_int_avx(XMMRegister dst, XMMR
vpslld(xtmp1, xtmp3, 5, vec_enc);
// Exponent is 32 if corresponding source lane contains max_int value.
vpcmpeqd(xtmp2, dst, xtmp1, vec_enc);
// LZCNT = 32 - exponent
// LZCNT = 32 - exponent_plus_one
vpsubd(dst, xtmp1, dst, vec_enc);
// Replace LZCNT with a value 1 if corresponding source lane

87
test/hotspot/jtreg/compiler/vectorization/TestNumberOfContinuousZeros.java
View File

@ -1,5 +1,6 @@
/*
* Copyright (c) 2022, 2023, Arm Limited. All rights reserved.
* Copyright (c) 2025, 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
@ -23,6 +24,7 @@
/**
* @test
* @bug 8297172 8331993 8349637
* @key randomness
* @summary Test vectorization of numberOfTrailingZeros/numberOfLeadingZeros for Long
* @requires vm.compiler2.enabled
@ -30,16 +32,20 @@
* (os.simpleArch == "aarch64" & vm.cpu.features ~= ".*sve.*") |
* (os.simpleArch == "riscv64" & vm.cpu.features ~= ".*zvbb.*")
* @library /test/lib /
* @modules jdk.incubator.vector
* @run driver compiler.vectorization.TestNumberOfContinuousZeros
*/
package compiler.vectorization;
import jdk.incubator.vector.*;
import compiler.lib.ir_framework.*;
import java.util.Random;
import jdk.test.lib.Asserts;
import jdk.test.lib.Utils;
public class TestNumberOfContinuousZeros {
private static final int[] SPECIAL = { 0x01FFFFFF, 0x03FFFFFE, 0x07FFFFFC, 0x0FFFFFF8, 0x1FFFFFF0, 0x3FFFFFE0, 0xFFFFFFFF };
private long[] inputLong;
private int[] outputLong;
private int[] inputInt;
@ -47,8 +53,8 @@ public class TestNumberOfContinuousZeros {
private static final int LEN = 1024;
private Random rng;
public static void main(String args[]) {
TestFramework.run();
public static void main(String[] args) {
TestFramework.runWithFlags("--add-modules=jdk.incubator.vector");
}
public TestNumberOfContinuousZeros() {
@ -56,7 +62,7 @@ public class TestNumberOfContinuousZeros {
outputLong = new int[LEN];
inputInt = new int[LEN];
outputInt = new int[LEN];
rng = new Random(42);
rng = Utils.getRandomInstance();
for (int i = 0; i < LEN; ++i) {
inputLong[i] = rng.nextLong();
inputInt[i] = rng.nextInt();
@ -119,5 +125,80 @@ public class TestNumberOfContinuousZeros {
Asserts.assertEquals(outputInt[i], Integer.numberOfLeadingZeros(inputInt[i]));
}
}
@Setup
static Object[] setupSpecialIntArray() {
int[] res = new int[LEN];
for (int i = 0; i < LEN; i++) {
res[i] = SPECIAL[i % SPECIAL.length];
}
return new Object[] { res };
}
@Test
@IR(counts = {IRNode.COUNT_LEADING_ZEROS_VI, "> 0"})
@Arguments(setup = "setupSpecialIntArray")
public Object[] testSpecialIntLeadingZeros(int[] ints) {
int[] res = new int[LEN];
for (int i = 0; i < LEN; ++i) {
res[i] = Integer.numberOfLeadingZeros(ints[i]);
}
return new Object[] { ints, res };
}
@Check(test = "testSpecialIntLeadingZeros")
public void checkSpecialIntLeadingZeros(Object[] vals) {
int[] in = (int[]) vals[0];
int[] out = (int[]) vals[1];
for (int i = 0; i < LEN; ++i) {
int value = Integer.numberOfLeadingZeros(in[i]);
if (out[i] != value) {
throw new IllegalStateException("Expected lzcnt(" + in[i] + ") to be " + value + " but got " + out[i]);
}
}
}
private static final VectorSpecies<Integer> SPECIES = IntVector.SPECIES_PREFERRED;
@Test
@IR(counts = {IRNode.COUNT_LEADING_ZEROS_VI, "> 0"})
@Arguments(setup = "setupSpecialIntArray")
public Object[] checkSpecialIntLeadingZerosVector(int[] ints) {
int[] res = new int[LEN];
for (int i = 0; i < ints.length; i += SPECIES.length()) {
IntVector av = IntVector.fromArray(SPECIES, ints, i);
av.lanewise(VectorOperators.LEADING_ZEROS_COUNT).intoArray(res, i);
}
return new Object[] { ints, res };
}
@Check(test = "checkSpecialIntLeadingZerosVector")
public void checkSpecialIntLeadingZerosVector(Object[] vals) {
int[] ints = (int[]) vals[0];
int[] res = (int[]) vals[1];
// Verification
int[] check = new int[LEN];
for (int i = 0; i < ints.length; i += SPECIES.length()) {
IntVector av = IntVector.fromArray(SPECIES, ints, i);
av.lanewise(VectorOperators.LEADING_ZEROS_COUNT).intoArray(check, i);
}
for (int i = 0; i < LEN; i++) {
if (res[i] != check[i]) {
throw new IllegalStateException("Expected " + check[i] + " but got " + res[i]);
}
}
}
}

128
test/hotspot/jtreg/compiler/vectorization/TestVectorZeroCount.java Normal file
View File

@ -0,0 +1,128 @@
/*
* Copyright (c) 2025, 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.
*
* 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.
*/
/* @test
* @bug 8349637
* @summary Ensure that vectorization of numberOfLeadingZeros and numberOfTrailingZeros outputs correct values
* @library /test/lib /
* @run main/othervm compiler.vectorization.TestVectorZeroCount
*/
package compiler.vectorization;
import java.util.Random;
import jdk.test.lib.Utils;
public class TestVectorZeroCount {
private static final int SIZE = 1024;
private static final Random RANDOM = Utils.getRandomInstance();
private static final int[] INT_VALUES = new int[SIZE];
private static final int[] INT_EXPECTED_LEADING = new int[SIZE];
private static final int[] INT_RESULT_LEADING = new int[SIZE];
private static final int[] INT_EXPECTED_TRAILING = new int[SIZE];
private static final int[] INT_RESULT_TRAILING = new int[SIZE];
private static final long[] LONG_VALUES = new long[SIZE];
private static final long[] LONG_EXPECTED_LEADING = new long[SIZE];
private static final long[] LONG_RESULT_LEADING = new long[SIZE];
private static final long[] LONG_EXPECTED_TRAILING = new long[SIZE];
private static final long[] LONG_RESULT_TRAILING = new long[SIZE];
private static int intCounter = Integer.MIN_VALUE;
private static int longIterations = 100_000_000;
public static boolean testInt() {
boolean done = false;
// Non-vectorized loop as baseline (not vectorized because source array is initialized)
for (int i = 0; i < SIZE; ++i) {
INT_VALUES[i] = intCounter++;
if (intCounter == Integer.MAX_VALUE) {
done = true;
}
INT_EXPECTED_LEADING[i] = Integer.numberOfLeadingZeros(INT_VALUES[i]);
INT_EXPECTED_TRAILING[i] = Integer.numberOfTrailingZeros(INT_VALUES[i]);
}
// Vectorized loop
for (int i = 0; i < SIZE; ++i) {
INT_RESULT_LEADING[i] = Integer.numberOfLeadingZeros(INT_VALUES[i]);
}
for (int i = 0; i < SIZE; ++i) {
INT_RESULT_TRAILING[i] = Integer.numberOfTrailingZeros(INT_VALUES[i]);
}
// Compare results
for (int i = 0; i < SIZE; ++i) {
if (INT_RESULT_LEADING[i] != INT_EXPECTED_LEADING[i]) {
throw new RuntimeException("Unexpected result for Integer.numberOfLeadingZeros(" + INT_VALUES[i] + "): " + INT_RESULT_LEADING[i] + ", expected " + INT_EXPECTED_LEADING[i]);
}
if (INT_RESULT_TRAILING[i] != INT_EXPECTED_TRAILING[i]) {
throw new RuntimeException("Unexpected result for Integer.numberOfTrailingZeros(" + INT_VALUES[i] + "): " + INT_RESULT_TRAILING[i] + ", expected " + INT_EXPECTED_TRAILING[i]);
}
}
return done;
}
public static boolean testLong() {
boolean done = false;
// Non-vectorized loop as baseline (not vectorized because source array is initialized)
for (int i = 0; i < SIZE; ++i) {
// Use random values because the long range is too large to iterate over it
LONG_VALUES[i] = RANDOM.nextLong();
if (longIterations-- == 0) {
done = true;
}
LONG_EXPECTED_LEADING[i] = Long.numberOfLeadingZeros(LONG_VALUES[i]);
LONG_EXPECTED_TRAILING[i] = Long.numberOfTrailingZeros(LONG_VALUES[i]);
}
// Vectorized loop
for (int i = 0; i < SIZE; ++i) {
LONG_RESULT_LEADING[i] = Long.numberOfLeadingZeros(LONG_VALUES[i]);
}
for (int i = 0; i < SIZE; ++i) {
LONG_RESULT_TRAILING[i] = Long.numberOfTrailingZeros(LONG_VALUES[i]);
}
// Compare results
for (int i = 0; i < SIZE; ++i) {
if (LONG_RESULT_LEADING[i] != LONG_EXPECTED_LEADING[i]) {
throw new RuntimeException("Unexpected result for Long.numberOfLeadingZeros(" + LONG_VALUES[i] + "): " + LONG_RESULT_LEADING[i] + ", expected " + LONG_EXPECTED_LEADING[i]);
}
if (LONG_RESULT_TRAILING[i] != LONG_EXPECTED_TRAILING[i]) {
throw new RuntimeException("Unexpected result for Long.numberOfTrailingZeros(" + LONG_VALUES[i] + "): " + LONG_RESULT_TRAILING[i] + ", expected " + LONG_EXPECTED_TRAILING[i]);
}
}
return done;
}
public static void main(String[] args) {
// Run twice to make sure compiled code is used from the beginning
for (int i = 0; i < 2; ++i) {
while (!testLong()) ;
while (!testInt()) ;
}
}
}