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8155795: Optimize Integer/Long.reverse by using reverseBytes

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Reviewed-by: redestad, shade
This commit is contained in:
Jaroslav Kamenik 2016-05-10 13:28:00 +02:00 committed by Claes Redestad
parent 26ba99921f
commit 553aa43136
4 changed files with 54 additions and 11 deletions
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13
jdk/src/java.base/share/classes/java/lang/Integer.java
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@ -1790,9 +1790,8 @@ public final class Integer extends Number implements Comparable<Integer> {
i = (i & 0x55555555) << 1 | (i >>> 1) & 0x55555555;
i = (i & 0x33333333) << 2 | (i >>> 2) & 0x33333333;
i = (i & 0x0f0f0f0f) << 4 | (i >>> 4) & 0x0f0f0f0f;
i = (i << 24) | ((i & 0xff00) << 8) |
((i >>> 8) & 0xff00) | (i >>> 24);
return i;
return reverseBytes(i);
}
/**
@ -1820,10 +1819,10 @@ public final class Integer extends Number implements Comparable<Integer> {
*/
@HotSpotIntrinsicCandidate
public static int reverseBytes(int i) {
return ((i >>> 24) ) |
((i >> 8) & 0xFF00) |
((i << 8) & 0xFF0000) |
((i << 24));
return (i << 24) |
((i & 0xff00) << 8) |
((i >>> 8) & 0xff00) |
(i >>> 24);
}
/**

6
jdk/src/java.base/share/classes/java/lang/Long.java
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@ -1952,10 +1952,8 @@ public final class Long extends Number implements Comparable<Long> {
i = (i & 0x5555555555555555L) << 1 | (i >>> 1) & 0x5555555555555555L;
i = (i & 0x3333333333333333L) << 2 | (i >>> 2) & 0x3333333333333333L;
i = (i & 0x0f0f0f0f0f0f0f0fL) << 4 | (i >>> 4) & 0x0f0f0f0f0f0f0f0fL;
i = (i & 0x00ff00ff00ff00ffL) << 8 | (i >>> 8) & 0x00ff00ff00ff00ffL;
i = (i << 48) | ((i & 0xffff0000L) << 16) |
((i >>> 16) & 0xffff0000L) | (i >>> 48);
return i;
return reverseBytes(i);
}
/**

23
jdk/test/java/lang/Integer/BitTwiddle.java
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@ -56,6 +56,21 @@ public class BitTwiddle {
if (lowestOneBit(MIN_VALUE) != MIN_VALUE)
throw new RuntimeException("f");
for (int i = 0; i < N; i++) {
int x = rnd.nextInt();
String expected = new StringBuilder()
.append(leftpad(toBinaryString(x), 32))
.reverse().toString();
String actual = leftpad(toBinaryString(reverse(x)), 32);
if (!expected.equals(actual)) {
throw new RuntimeException("reverse: \n" +
expected + " \n" + actual);
}
}
for (int i = 0; i < N; i++) {
int x = rnd.nextInt();
if (highestOneBit(x) != reverse(lowestOneBit(reverse(x))))
@ -136,4 +151,12 @@ public class BitTwiddle {
throw new RuntimeException("z: " + toHexString(x));
}
}
private static String leftpad(String s, int width) {
String r = s;
for (int c = 0; c < width - s.length(); c++) {
r = "0" + r;
}
return r;
}
}

23
jdk/test/java/lang/Long/BitTwiddle.java
View File

@ -56,6 +56,21 @@ public class BitTwiddle {
if (lowestOneBit(MIN_VALUE) != MIN_VALUE)
throw new RuntimeException("f");
for (int i = 0; i < N; i++) {
long x = rnd.nextLong();
String expected = new StringBuilder()
.append(leftpad(toBinaryString(x), 64))
.reverse().toString();
String actual = leftpad(toBinaryString(reverse(x)), 64);
if (!expected.equals(actual)) {
throw new RuntimeException("reverse: \n" +
expected + " \n" + actual);
}
}
for (int i = 0; i < N; i++) {
long x = rnd.nextLong();
if (highestOneBit(x) != reverse(lowestOneBit(reverse(x))))
@ -136,4 +151,12 @@ public class BitTwiddle {
throw new RuntimeException("z: " + toHexString(x));
}
}
private static String leftpad(String s, int width) {
String r = s;
for (int c = 0; c < width - s.length(); c++) {
r = "0" + r;
}
return r;
}
}