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8189230: JDK method:java.lang.Integer.numberOfLeadingZeros(int) can be optimized

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Directly return zero for a negative parameter instead of calculating

Reviewed-by: psandoz
This commit is contained in:
Brian Burkhalter 2018-03-15 08:11:01 -07:00
parent acb3103b8f
commit f5578ab220
2 changed files with 6 additions and 6 deletions
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6
src/java.base/share/classes/java/lang/Integer.java
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@ -1,5 +1,5 @@
/* /*
* Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -1625,8 +1625,8 @@ public final class Integer extends Number implements Comparable<Integer> {
@HotSpotIntrinsicCandidate @HotSpotIntrinsicCandidate
public static int numberOfLeadingZeros(int i) { public static int numberOfLeadingZeros(int i) {
// HD, Figure 5-6 // HD, Figure 5-6
if (i == 0) if (i <= 0)
return 32; return i == 0 ? 32 : 0;
int n = 1; int n = 1;
if (i >>> 16 == 0) { n += 16; i <<= 16; } if (i >>> 16 == 0) { n += 16; i <<= 16; }
if (i >>> 24 == 0) { n += 8; i <<= 8; } if (i >>> 24 == 0) { n += 8; i <<= 8; }

6
src/java.base/share/classes/java/lang/Long.java
View file

@ -1,5 +1,5 @@
/* /*
* Copyright (c) 1994, 2017, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 1994, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* *
* This code is free software; you can redistribute it and/or modify it * This code is free software; you can redistribute it and/or modify it
@ -1771,8 +1771,8 @@ public final class Long extends Number implements Comparable<Long> {
@HotSpotIntrinsicCandidate @HotSpotIntrinsicCandidate
public static int numberOfLeadingZeros(long i) { public static int numberOfLeadingZeros(long i) {
// HD, Figure 5-6 // HD, Figure 5-6
if (i == 0) if (i <= 0)
return 64; return i == 0 ? 64 : 0;
int n = 1; int n = 1;
int x = (int)(i >>> 32); int x = (int)(i >>> 32);
if (x == 0) { n += 32; x = (int)i; } if (x == 0) { n += 32; x = (int)i; }