CVS commit: basesrc/lib/libc/arch/sh3/string

[ITOH Yasufumi <itohy%netbsd.org@localhost>]

Module Name:    basesrc
Committed By:   itohy
Date:           Sun Sep  1 13:14:54 UTC 2002

Modified Files:
        basesrc/lib/libc/arch/sh3/string: ffs.S
        syssrc/sys/lib/libkern/arch/sh3: ffs.S

Log Message:
Save 1-4 instructions on all cases except for the ret=0 case.

This is probably the last version from me. :)
You are welcome to speed it up, of course. :)

Here's a benchmark on SH-4 200MHz.
9.2% faster if all the cases occur evenly.

return value    C version       previous vers   this version    speed ratio
of ffs()        (ns/call) *1    (ns/call)       (ns/call) *2    (*1/*2)
------------    ------------    -------------   ------------    -----------
 0                86             81              81             1.06
 1               110            106              91             1.21
 2               132            106              92             1.43
 3               165            117              96             1.72
 4               201            116              95             2.12
 5               237            107              99             2.39
 6               271            106             101             2.68
 7               307            116             107             2.87
 8               342            116             105             3.26
 9               376            126             111             3.39
10               410            127             110             3.73
11               446            136             115             3.88
12               483            134             116             4.16
13               518            125             119             4.35
14               551            126             120             4.59
15               587            135             127             4.62
16               624            136             126             4.95
17               658            139             126             5.22
18               694            140             126             5.51
19               727            148             131             5.55
20               764            150             131             5.83
21               799            141             135             5.92
22               834            142             135             6.18
23               868            152             140             6.20
24               903            153             142             6.36
25               939            140             127             7.39
26               974            141             126             7.73
27              1009            152             131             7.70
28              1044            148             130             8.03
29              1080            141             136             7.94
30              1115            141             136             8.20
31              1151            151             141             8.16
32              1185            151             140             8.46


To generate a diff of this commit:
cvs rdiff -r1.3 -r1.4 basesrc/lib/libc/arch/sh3/string/ffs.S
cvs rdiff -r1.3 -r1.4 syssrc/sys/lib/libkern/arch/sh3/ffs.S

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.