stan/jdk-24
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

8209171: Simplify Java implementation of Integer/Long.numberOfTrailingZeros()

Browse Source 
Co-authored-by: Martin Buchholz <martinrb@google.com>
Reviewed-by: martin
This commit is contained in:
Ivan Gerasimov 2018-08-23 12:09:46 -07:00
parent acaf155de7
commit ffa4cfe355
2 changed files with 12 additions and 19 deletions
src/java.base/share/classes/java/lang
Integer.javaLong.java

18
src/java.base/share/classes/java/lang/Integer.java

@ -1654,15 +1654,15 @@ public final class Integer extends Number implements Comparable<Integer> {
*/
@HotSpotIntrinsicCandidate
public static int numberOfTrailingZeros(int i) {
// HD, Figure 5-14
int y;
if (i == 0) return 32;
int n = 31;
y = i <<16; if (y != 0) { n = n -16; i = y; }
y = i << 8; if (y != 0) { n = n - 8; i = y; }
y = i << 4; if (y != 0) { n = n - 4; i = y; }
y = i << 2; if (y != 0) { n = n - 2; i = y; }
return n - ((i << 1) >>> 31);
// HD, Count trailing 0's
i = ~i & (i - 1);
if (i <= 0) return i & 32;
int n = 1;
if (i > 1 << 16) { n += 16; i >>>= 16; }
if (i > 1 << 8) { n += 8; i >>>= 8; }
if (i > 1 << 4) { n += 4; i >>>= 4; }
if (i > 1 << 2) { n += 2; i >>>= 2; }
return n + (i >>> 1);
}
/**

13
src/java.base/share/classes/java/lang/Long.java

@ -1782,16 +1782,9 @@ public final class Long extends Number implements Comparable<Long> {
*/
@HotSpotIntrinsicCandidate
public static int numberOfTrailingZeros(long i) {
// HD, Figure 5-14
int x, y;
if (i == 0) return 64;
int n = 63;
y = (int)i; if (y != 0) { n = n -32; x = y; } else x = (int)(i>>>32);
y = x <<16; if (y != 0) { n = n -16; x = y; }
y = x << 8; if (y != 0) { n = n - 8; x = y; }
y = x << 4; if (y != 0) { n = n - 4; x = y; }
y = x << 2; if (y != 0) { n = n - 2; x = y; }
return n - ((x << 1) >>> 31);
int x = (int)i;
return x == 0 ? 32 + Integer.numberOfTrailingZeros((int)(i >>> 32))
: Integer.numberOfTrailingZeros(x);
}
/**