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memset() on coldfire now exploits burst mode whenever possible, giving another speed increase of up to 2.4 times for large blocks. Added a slight optimisation for small blocks as well.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@6790 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jens Arnold 2005-06-21 18:15:35 +00:00
parent ac0bc83777
commit 8caf175c7f
1 changed files with 60 additions and 9 deletions
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69
firmware/common/memset_a.S
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@ -123,21 +123,27 @@ _memset:
*
* register usage:
* %d0 - data (spread to all 4 bytes when using long stores)
* %d1 - temporary
* %d1 - temporary / data (for burst transfer)
* %d2 - data (for burst transfer)
* %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
* to start in order to ease returning the start address.
*/
memset:
move.l (4,%sp),%a0 /* start address */
move.l (8,%sp),%d0 /* data */
move.l (12,%sp),%a1 /* length */
add.l %a0,%a1 /* %a1 = end address */
move.l %a0,%d1
neg.l %d1
and.l #3,%d1 /* %d1 = (4 - align_offset) % 4 */
addq.l #4,%d1
addq.l #7,%d1
and.l #0xFFFFFFFC,%d1 /* %d1 = first long bound + 4 */
cmp.l %d1,%a1 /* at least one aligned longword to fill? */
add.l %a0,%a1 /* %a1 = end address; doesn't change flags */
blo.b .no_longs /* no, jump directly to byte loop */
and.l #0xFF,%d0 /* start: spread data to all 4 bytes */
@ -148,7 +154,7 @@ memset:
swap %d0
or.l %d1,%d0 /* data now in all 4 bytes of %d0 */
mov.l %a1,%d1
move.l %a1,%d1
and.l #0xFFFFFFFC,%d1 /* %d1 = last long bound */
cmp.l %d1,%a1 /* any bytes to set? */
bls.b .end_b1 /* no: skip byte loop */
@ -160,14 +166,59 @@ memset:
bhi.b .loop_b1
.end_b1:
move.l %a0,%d1
add.l #31,%d1
and.l #0xFFFFFFF0,%d1 /* %d1 = first line bound + 16 */
cmp.l %d1,%a1 /* at least one full line to fill? */
blo.b .no_lines /* no, jump to longword loop */
mov.l %a1,%d1
and.l #0xFFFFFFF0,%d1 /* %d1 = last line bound */
cmp.l %d1,%a1 /* any longwords to set? */
bls.b .end_l1 /* no: skip longword loop */
/* leading longword loop: sets 0..3 longwords */
.loop_l1:
move.l %d0,-(%a1) /* store longword */
cmp.l %d1,%a1 /* runs %a1 down to last line bound */
bhi.b .loop_l1
.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 */
/* 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 */
bhi.b .loop_line
move.l (%sp)+,%a2 /* restore registers */
move.l (%sp)+,%d3
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 */
.no_lines:
move.l %a0,%d1 /* %d1 = start address ... */
addq.l #3,%d1 /* ... +3, account for possible trailing bytes */
/* main loop: set longs */
.loop_l:
/* 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_l
bhi.b .loop_l2
.no_longs:
cmp.l %a0,%a1 /* any bytes left? */