[5361] in Athena Bugs
RT strlen() optimization
daemon@ATHENA.MIT.EDU (John Carr)
Sat Jun 30 09:17:21 1990
To: bugs@ATHENA.MIT.EDU
Date: Sat, 30 Jun 90 09:17:09 EDT
From: John Carr <jfc@ATHENA.MIT.EDU>
*** /source/bsd-4.3/rt/lib/libc/ca/gen/strlen.s Tue Sep 19 14:20:23 1989
--- strlen.s Sat Jun 30 09:13:46 1990
***************
*** 8,14 ****
/* $Source: /ibm/acis/usr/src/lib/libc/ca/gen/RCS/strlen.s,v $ */
.data
! rcsid: .asciz "$Header:strlen.s 12.0$"
.text
#include "LINKG.h"
--- 8,14 ----
/* $Source: /ibm/acis/usr/src/lib/libc/ca/gen/RCS/strlen.s,v $ */
.data
! rcsid: .asciz "$Header:strlen.s 12.1$"
.text
#include "LINKG.h"
***************
*** 22,29 ****
nilz r5,r2,0x03 # Round string addr down to word boundary
s r2,r5 # More of the rounding
sli r5,3 # Calc offset into following switch statement
! get r4,$0f # Get address of beginning of switch statement
! a r4,r5 # Add displacement of the case
brx r4 # Branch to calculated case and
ls r4,0(r2) # get first word (possibly rounded down).
# at this point:
--- 22,28 ----
nilz r5,r2,0x03 # Round string addr down to word boundary
s r2,r5 # More of the rounding
sli r5,3 # Calc offset into following switch statement
! get r4,$0f(r5) # Add address of beginning of switch statement
brx r4 # Branch to calculated case and
ls r4,0(r2) # get first word (possibly rounded down).
# at this point:
***************
*** 32,39 ****
# r4 contains 4 byes with string's initial bytes somewhere in r2
# The following is a switch statement. Initially, control jumps to one of
# the labels 0, 1, 2 or 3 depending on where string's first byte is in r2
! #
! 9: inc r2,4 # point to next word
# code at 0f, 1f, 2f must be exactly 8 bytes long to match switch above
# The switch:
0:
--- 31,37 ----
# r4 contains 4 byes with string's initial bytes somewhere in r2
# The following is a switch statement. Initially, control jumps to one of
# the labels 0, 1, 2 or 3 depending on where string's first byte is in r2
! .align 2
# code at 0f, 1f, 2f must be exactly 8 bytes long to match switch above
# The switch:
0:
***************
*** 52,58 ****
nilz r5,r4,0x00ff # get byte 3 from r4
jeq 3f
ls r4,4(r2)
! b 9b # null not found in byte 3, try next word
# Come to one of labels 0, 1, 2 or 3 when a null byte was found and
# adjust r2 to point to the zero byte
--- 50,57 ----
nilz r5,r4,0x00ff # get byte 3 from r4
jeq 3f
ls r4,4(r2)
! bx 0b # null not found in byte 3, try next word
! inc r2,4
# Come to one of labels 0, 1, 2 or 3 when a null byte was found and
# adjust r2 to point to the zero byte
