diff options
Diffstat (limited to 'common/clz.c')
-rw-r--r-- | common/clz.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/common/clz.c b/common/clz.c new file mode 100644 index 0000000000..30c987e367 --- /dev/null +++ b/common/clz.c @@ -0,0 +1,42 @@ +/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved. + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + * + * Software emulation for CLZ instruction + */ + +/** + * Count leading zeros + * + * @param x non null integer. + * @return the number of leading 0-bits in x, + * starting at the most significant bit position. + */ +int __clzsi2(int x) +{ + int r = 0; + + if (!x) + return 32; + if (!(x & 0xffff0000u)) { + x <<= 16; + r += 16; + } + if (!(x & 0xff000000u)) { + x <<= 8; + r += 8; + } + if (!(x & 0xf0000000u)) { + x <<= 4; + r += 4; + } + if (!(x & 0xc0000000u)) { + x <<= 2; + r += 2; + } + if (!(x & 0x80000000u)) { + x <<= 1; + r += 1; + } + return r; +} |