1 /*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "roundup.h"
18
roundup(unsigned v)19 unsigned roundup(unsigned v) {
20 // __builtin_clz is undefined for zero input
21 if (v == 0) {
22 v = 1;
23 }
24
25 int lz = __builtin_clz((int) v);
26 unsigned rounded = ((unsigned) 0x80000000) >> lz;
27 // 0x800000001 and higher are actually rounded _down_ to prevent overflow
28 if (v > rounded && lz > 0) {
29 rounded <<= 1;
30 }
31 return rounded;
32 }
33