diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/libc/string/strlen.c | 15 |
1 files changed, 4 insertions, 11 deletions
diff --git a/lib/libc/string/strlen.c b/lib/libc/string/strlen.c index a862ffc245ca..2d1803b1e078 100644 --- a/lib/libc/string/strlen.c +++ b/lib/libc/string/strlen.c @@ -35,10 +35,6 @@ __FBSDID("$FreeBSD$"); /* * Portable strlen() for 32-bit and 64-bit systems. * - * Rationale: it is generally much more efficient to do word length - * operations and avoid branches on modern computer systems, as - * compared to byte-length operations with a lot of branches. - * * The expression: * * ((x - 0x01....01) & ~x & 0x80....80) @@ -46,15 +42,12 @@ __FBSDID("$FreeBSD$"); * would evaluate to a non-zero value iff any of the bytes in the * original word is zero. * - * On multi-issue processors, we can divide the above expression into: - * a) (x - 0x01....01) - * b) (~x & 0x80....80) - * c) a & b - * - * Where, a) and b) can be partially computed in parallel. - * * The algorithm above is found on "Hacker's Delight" by * Henry S. Warren, Jr. + * + * Note: this leaves performance on the table and each architecture + * would be best served with a tailor made routine instead, even if + * using the same trick. */ /* Magic numbers for the algorithm */ |