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kernel add
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/*
Copyright 2003 Richard Curnow, SuperH (UK) Ltd.
This file is subject to the terms and conditions of the GNU General Public
License. See the file "COPYING" in the main directory of this archive
for more details.
Tight version of mempy for the case of just copying a page.
Prefetch strategy empirically optimised against RTL simulations
of SH5-101 cut2 eval chip with Cayman board DDR memory.
Parameters:
r2 : destination effective address (start of page)
r3 : source effective address (start of page)
Always copies 4096 bytes.
Points to review.
* Currently the prefetch is 4 lines ahead and the alloco is 2 lines ahead.
It seems like the prefetch needs to be at at least 4 lines ahead to get
the data into the cache in time, and the allocos contend with outstanding
prefetches for the same cache set, so it's better to have the numbers
different.
*/
.section .text..SHmedia32,"ax"
.little
.balign 8
.global copy_page
copy_page:
/* Copy 4096 bytes worth of data from r3 to r2.
Do prefetches 4 lines ahead.
Do alloco 2 lines ahead */
pta 1f, tr1
pta 2f, tr2
pta 3f, tr3
ptabs r18, tr0
#if 0
/* TAKum03020 */
ld.q r3, 0x00, r63
ld.q r3, 0x20, r63
ld.q r3, 0x40, r63
ld.q r3, 0x60, r63
#endif
alloco r2, 0x00
synco ! TAKum03020
alloco r2, 0x20
synco ! TAKum03020
movi 3968, r6
add r2, r6, r6
addi r6, 64, r7
addi r7, 64, r8
sub r3, r2, r60
addi r60, 8, r61
addi r61, 8, r62
addi r62, 8, r23
addi r60, 0x80, r22
/* Minimal code size. The extra branches inside the loop don't cost much
because they overlap with the time spent waiting for prefetches to
complete. */
1:
#if 0
/* TAKum03020 */
bge/u r2, r6, tr2 ! skip prefetch for last 4 lines
ldx.q r2, r22, r63 ! prefetch 4 lines hence
#endif
2:
bge/u r2, r7, tr3 ! skip alloco for last 2 lines
alloco r2, 0x40 ! alloc destination line 2 lines ahead
synco ! TAKum03020
3:
ldx.q r2, r60, r36
ldx.q r2, r61, r37
ldx.q r2, r62, r38
ldx.q r2, r23, r39
st.q r2, 0, r36
st.q r2, 8, r37
st.q r2, 16, r38
st.q r2, 24, r39
addi r2, 32, r2
bgt/l r8, r2, tr1
blink tr0, r63 ! return
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