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#include "DEFS.h"
/*
* memcpy(to, from, len)
* {ov}bcopy(from, to, len)
*/
LEAF(memcpy)
.set noreorder
move v0, a0 # swap from and to
move a0, a1
move a1, v0
ALEAF(bcopy)
ALEAF(ovbcopy)
.set noreorder
addu t0, a0, a2 # t0 = end of s1 region
sltu t1, a1, t0
sltu t2, a0, a1
and t1, t1, t2 # t1 = true if from < to < (from+len)
beq t1, zero, forward # non overlapping, do forward copy
slt t2, a2, 12 # check for small copy
ble a2, zero, 2f
addu t1, a1, a2 # t1 = end of to region
1:
lb v1, -1(t0) # copy bytes backwards,
subu t0, t0, 1 # doesnt happen often so do slow way
subu t1, t1, 1
bne t0, a0, 1b
sb v1, 0(t1)
2:
j ra
nop
forward:
bne t2, zero, smallcpy # do a small bcopy
xor v1, a0, a1 # compare low two bits of addresses
and v1, v1, 3
subu a3, zero, a1 # compute # bytes to word align address
beq v1, zero, aligned # addresses can be word aligned
and a3, a3, 3
beq a3, zero, 1f
subu a2, a2, a3 # subtract from remaining count
LWHI v1, 0(a0) # get next 4 bytes (unaligned)
LWLO v1, 3(a0)
addu a0, a0, a3
SWHI v1, 0(a1) # store 1, 2, or 3 bytes to align a1
addu a1, a1, a3
1:
and v1, a2, 3 # compute number of words left
subu a3, a2, v1
move a2, v1
addu a3, a3, a0 # compute ending address
2:
LWHI v1, 0(a0) # copy words a0 unaligned, a1 aligned
LWLO v1, 3(a0)
addu a0, a0, 4
sw v1, 0(a1)
addu a1, a1, 4
bne a0, a3, 2b
nop # We have to do this mmu-bug.
b smallcpy
nop
aligned:
beq a3, zero, 1f
subu a2, a2, a3 # subtract from remaining count
LWHI v1, 0(a0) # copy 1, 2, or 3 bytes to align
addu a0, a0, a3
SWHI v1, 0(a1)
addu a1, a1, a3
1:
and v1, a2, 3 # compute number of whole words left
subu a3, a2, v1
move a2, v1
addu a3, a3, a0 # compute ending address
2:
lw v1, 0(a0) # copy words
addu a0, a0, 4
sw v1, 0(a1)
bne a0, a3, 2b
addu a1, a1, 4
smallcpy:
ble a2, zero, 2f
addu a3, a2, a0 # compute ending address
1:
lbu v1, 0(a0) # copy bytes
addu a0, a0, 1
sb v1, 0(a1)
bne a0, a3, 1b
addu a1, a1, 1 # MMU BUG ? can't do -1(a1) at 0x80000000!!
2:
j ra
nop
END(memcpy)
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