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Coldfire: slight optimisations of memset().

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7649 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jens Arnold 2005-10-22 08:06:49 +00:00
parent 56bb45cfaf
commit aaf36caeb6
1 changed files with 10 additions and 12 deletions
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22
firmware/common/memset_a.S
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@ -128,7 +128,6 @@ _memset:
* %d3 - data (for burst transfer)
* %a0 - start address
* %a1 - current address (runs down from end to start)
* %a2 - end address (for burst transfer)
*
* For maximum speed this routine uses both long stores and burst mode,
* storing whole lines with movem.l. The routine fills memory from end
@ -186,37 +185,36 @@ memset:
.end_l1:
move.l %d2,-(%sp) /* free some registers */
move.l %d3,-(%sp)
move.l %a2,-(%sp)
move.l %d0,%d1 /* spread data to 4 data registers */
move.l %d0,%d2
move.l %d0,%d3
lea.l (15,%a0),%a2 /* %a2 = start address + 15, acct. for trl. data */
lea.l (15,%a0),%a0 /* start address += 15, acct. for trl. data */
/* main loop: set whole lines utilising burst mode */
.loop_line:
lea.l (-16,%a1),%a1 /* pre-decrement */
movem.l %d0-%d3,(%a1) /* store line */
cmp.l %a2,%a1 /* runs %a1 down to first line bound */
cmp.l %a0,%a1 /* runs %a1 down to first line bound */
bhi.b .loop_line
move.l (%sp)+,%a2 /* restore registers */
move.l (%sp)+,%d3
lea.l (-15,%a0),%a0 /* correct start address */
move.l (%sp)+,%d3 /* restore registers */
move.l (%sp)+,%d2
move.l %a0,%d1 /* %d1 = start address ... */
addq.l #3,%d1 /* ... +3, account for possible trailing bytes */
bra.b .start_l2 /* there might be no longwords left when coming
* out of the main loop */
cmp.l %d1,%a1 /* any longwords left */
bhi.b .loop_l2 /* yes: jump to longword loop */
bra.b .no_longs /* no: skip loop */
.no_lines:
move.l %a0,%d1 /* %d1 = start address ... */
addq.l #3,%d1 /* ... +3, account for possible trailing bytes */
/* trailing longword loop */
.loop_l2:
move.l %d0,-(%a1) /* store longword */
.start_l2:
cmp.l %d1,%a1 /* runs %a1 down to first long bound */
bhi.b .loop_l2