Diffstat (limited to 'lib/libc')
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
@@ -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 */