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/*
* arch/alpha/lib/ev6-memcpy.S
* 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
*
* Reasonably optimized memcpy() routine for the Alpha 21264
*
* - memory accessed as aligned quadwords only
* - uses bcmpge to compare 8 bytes in parallel
*
* Much of the information about 21264 scheduling/coding comes from:
* Compiler Writer's Guide for the Alpha 21264
* abbreviated as 'CWG' in other comments here
* ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
* Scheduling notation:
* E - either cluster
* U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
* L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
*
* Temp usage notes:
* $1,$2, - scratch
*/
.set noreorder
.set noat
.align 4
.globl memcpy
.ent memcpy
memcpy:
.frame $30,0,$26,0
.prologue 0
mov $16, $0 # E : copy dest to return
ble $18, $nomoredata # U : done with the copy?
xor $16, $17, $1 # E : are source and dest alignments the same?
and $1, 7, $1 # E : are they the same mod 8?
bne $1, $misaligned # U : Nope - gotta do this the slow way
/* source and dest are same mod 8 address */
and $16, 7, $1 # E : Are both 0mod8?
beq $1, $both_0mod8 # U : Yes
nop # E :
/*
* source and dest are same misalignment. move a byte at a time
* until a 0mod8 alignment for both is reached.
* At least one byte more to move
*/
$head_align:
ldbu $1, 0($17) # L : grab a byte
subq $18, 1, $18 # E : count--
addq $17, 1, $17 # E : src++
stb $1, 0($16) # L :
addq $16, 1, $16 # E : dest++
and $16, 7, $1 # E : Are we at 0mod8 yet?
ble $18, $nomoredata # U : done with the copy?
bne $1, $head_align # U :
$both_0mod8:
cmple $18, 127, $1 # E : Can we unroll the loop?
bne $1, $no_unroll # U :
and $16, 63, $1 # E : get mod64 alignment
beq $1, $do_unroll # U : no single quads to fiddle
$single_head_quad:
ldq $1, 0($17) # L : get 8 bytes
subq $18, 8, $18 # E : count -= 8
addq $17, 8, $17 # E : src += 8
nop # E :
stq $1, 0($16) # L : store
addq $16, 8, $16 # E : dest += 8
and $16, 63, $1 # E : get mod64 alignment
bne $1, $single_head_quad # U : still not fully aligned
$do_unroll:
addq $16, 64, $7 # E : Initial (+1 trip) wh64 address
cmple $18, 127, $1 # E : Can we go through the unrolled loop?
bne $1, $tail_quads # U : Nope
nop # E :
$unroll_body:
wh64 ($7) # L1 : memory subsystem hint: 64 bytes at
# ($7) are about to be over-written
ldq $6, 0($17) # L0 : bytes 0..7
nop # E :
nop # E :
ldq $4, 8($17) # L : bytes 8..15
ldq $5, 16($17) # L : bytes 16..23
addq $7, 64, $7 # E : Update next wh64 address
nop # E :
ldq $3, 24($17) # L : bytes 24..31
addq $16, 64, $1 # E : fallback value for wh64
nop # E :
nop # E :
addq $17, 32, $17 # E : src += 32 bytes
stq $6, 0($16) # L : bytes 0..7
nop # E :
nop # E :
stq $4, 8($16) # L : bytes 8..15
stq $5, 16($16) # L : bytes 16..23
subq $18, 192, $2 # E : At least two more trips to go?
nop # E :
stq $3, 24($16) # L : bytes 24..31
addq $16, 32, $16 # E : dest += 32 bytes
nop # E :
nop # E :
ldq $6, 0($17) # L : bytes 0..7
ldq $4, 8($17) # L : bytes 8..15
cmovlt $2, $1, $7 # E : Latency 2, extra map slot - Use
# fallback wh64 address if < 2 more trips
nop # E :
ldq $5, 16($17) # L : bytes 16..23
ldq $3, 24($17) # L : bytes 24..31
addq $16, 32, $16 # E : dest += 32
subq $18, 64, $18 # E : count -= 64
addq $17, 32, $17 # E : src += 32
stq $6, -32($16) # L : bytes 0..7
stq $4, -24($16) # L : bytes 8..15
cmple $18, 63, $1 # E : At least one more trip?
stq $5, -16($16) # L : bytes 16..23
stq $3, -8($16) # L : bytes 24..31
nop # E :
beq $1, $unroll_body
$tail_quads:
$no_unroll:
.align 4
subq $18, 8, $18 # E : At least a quad left?
blt $18, $less_than_8 # U : Nope
nop # E :
nop # E :
$move_a_quad:
ldq $1, 0($17) # L : fetch 8
subq $18, 8, $18 # E : count -= 8
addq $17, 8, $17 # E : src += 8
nop # E :
stq $1, 0($16) # L : store 8
addq $16, 8, $16 # E : dest += 8
bge $18, $move_a_quad # U :
nop # E :
$less_than_8:
.align 4
addq $18, 8, $18 # E : add back for trailing bytes
ble $18, $nomoredata # U : All-done
nop # E :
nop # E :
/* Trailing bytes */
$tail_bytes:
subq $18, 1, $18 # E : count--
ldbu $1, 0($17) # L : fetch a byte
addq $17, 1, $17 # E : src++
nop # E :
stb $1, 0($16) # L : store a byte
addq $16, 1, $16 # E : dest++
bgt $18, $tail_bytes # U : more to be done?
nop # E :
/* branching to exit takes 3 extra cycles, so replicate exit here */
ret $31, ($26), 1 # L0 :
nop # E :
nop # E :
nop # E :
$misaligned:
mov $0, $4 # E : dest temp
and $0, 7, $1 # E : dest alignment mod8
beq $1, $dest_0mod8 # U : life doesnt totally suck
nop
$aligndest:
ble $18, $nomoredata # U :
ldbu $1, 0($17) # L : fetch a byte
subq $18, 1, $18 # E : count--
addq $17, 1, $17 # E : src++
stb $1, 0($4) # L : store it
addq $4, 1, $4 # E : dest++
and $4, 7, $1 # E : dest 0mod8 yet?
bne $1, $aligndest # U : go until we are aligned.
/* Source has unknown alignment, but dest is known to be 0mod8 */
$dest_0mod8:
subq $18, 8, $18 # E : At least a quad left?
blt $18, $misalign_tail # U : Nope
ldq_u $3, 0($17) # L : seed (rotating load) of 8 bytes
nop # E :
$mis_quad:
ldq_u $16, 8($17) # L : Fetch next 8
extql $3, $17, $3 # U : masking
extqh $16, $17, $1 # U : masking
bis $3, $1, $1 # E : merged bytes to store
subq $18, 8, $18 # E : count -= 8
addq $17, 8, $17 # E : src += 8
stq $1, 0($4) # L : store 8 (aligned)
mov $16, $3 # E : "rotate" source data
addq $4, 8, $4 # E : dest += 8
bge $18, $mis_quad # U : More quads to move
nop
nop
$misalign_tail:
addq $18, 8, $18 # E : account for tail stuff
ble $18, $nomoredata # U :
nop
nop
$misalign_byte:
ldbu $1, 0($17) # L : fetch 1
subq $18, 1, $18 # E : count--
addq $17, 1, $17 # E : src++
nop # E :
stb $1, 0($4) # L : store
addq $4, 1, $4 # E : dest++
bgt $18, $misalign_byte # U : more to go?
nop
$nomoredata:
ret $31, ($26), 1 # L0 :
nop # E :
nop # E :
nop # E :
.end memcpy
/* For backwards module compatibility. */
__memcpy = memcpy
.globl __memcpy
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