/*
* arch/alpha/lib/ev6-memset.S
*
* This is an efficient (and relatively small) implementation of the C library
* "memset()" function for the 21264 implementation of Alpha.
*
* 21264 version contributed by Rick Gorton <rick.gorton@alpha-processor.com>
*
* 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
* The algorithm for the leading and trailing quadwords remains the same,
* however the loop has been unrolled to enable better memory throughput,
* and the code has been replicated for each of the entry points: __memset
* and __memsetw to permit better scheduling to eliminate the stalling
* encountered during the mask replication.
* A future enhancement might be to put in a byte store loop for really
* small (say < 32 bytes) memset()s. Whether or not that change would be
* a win in the kernel would depend upon the contextual usage.
* WARNING: Maintaining this is going to be more work than the above version,
* as fixes will need to be made in multiple places. The performance gain
* is worth it.
*/
.set noat
.set noreorder
.text
.globl __memset
.globl __memsetw
.globl __constant_c_memset
.globl memset
.ent __memset
.align 5
__memset:
.frame $30,0,$26,0
.prologue 0
/*
* Serious stalling happens. The only way to mitigate this is to
* undertake a major re-write to interleave the constant materialization
* with other parts of the fall-through code. This is important, even
* though it makes maintenance tougher.
* Do this later.
*/
and $17,255,$1 # E : 00000000000000ch
insbl $17,1,$2 # U : 000000000000ch00
bis $16,$16,$0 # E : return value
ble $18,end_b # U : zero length requested?
addq $18,$16,$6 # E : max address to write to
bis $1,$2,$17 # E : 000000000000chch
insbl $1,2,$3 # U : 0000000000ch0000
insbl $1,3,$4 # U : 00000000ch000000
or $3,$4,$3 # E : 00000000chch0000
inswl $17,4,$5 # U : 0000chch00000000
xor $16,$6,$1 # E : will complete write be within one quadword?
inswl $17,6,$2 # U : chch000000000000
or $17,$3,$17 # E : 00000000chchchch
or $2,$5,$2 # E : chchchch00000000
bic $1,7,$1 # E : fit within a single quadword?
and $16,7,$3 # E : Target addr misalignment
or $17,$2,$17 # E : chchchchchchchch
beq $1,within_quad_b # U :
nop # E :
beq $3,aligned_b # U : target is 0mod8
/*
* Target address is misaligned, and won't fit within a quadword
*/
ldq_u $4,0($16) # L : Fetch first partial
bis $16,$16,$5 # E : Save the address
insql $17,$16,$2 # U : Insert new bytes
subq $3,8,$3 # E : Invert (for addressing uses)
addq $18,$3,$18 # E : $18 is new count ($3 is negative)
mskql $4,$16,$4 # U : clear relevant parts of the quad
subq $16,$3,$16 # E : $16 is new aligned destination
bis $2,$4,$1 # E : Final bytes
nop
stq_u $1,0($5) # L : Store result
nop
nop
.align 4
aligned_b:
/*
* We are now guaranteed to be quad aligned, with at least
* one partial quad to write.
*/
sra $18,3,$3 # U : Number of remaining quads to write
and $18,7,$18 # E : Number of trailing bytes to write
bis $16,$16,$5 # E : Save dest address
beq $3,no_quad_b # U : tail stuff only
/*
* it's worth the effort to unroll this and use wh64 if possible
* Lifted a bunch of code from clear_user.S
* At this point, entry values are:
* $16 Current destination address
* $5 A copy of $16
* $6 The max quadword address to write to
* $18 Number trailer bytes
* $3 Number quads to write
*/
and $16, 0x3f, $2 # E : Forward work (only useful for unrolled loop)
subq $3, 16, $4 # E : Only try to unroll if > 128 bytes
subq $2, 0x40, $1 # E : bias counter (aligning stuff 0mod64)
blt $4, loop_b # U :
/*
* We know we've got at least 16 quads, minimum of one trip
* through unrolled loop. Do a quad at a time to get us 0mod64
* aligned.
*/
nop # E :
nop # E :
nop # E :
beq $1, $bigalign_b # U :
$alignmod64_b:
stq $17, 0($5) # L :
subq $3, 1, $3 # E : For consistency later
addq $1, 8, $1 # E : Increment towards zero for alignment
addq $5, 8, $4 # E : Initial wh64 address (filler instruction)
nop
nop
addq $5, 8, $5 # E : Inc address
blt $1, $alignmod64_b # U :
$bigalign_b:
/*
* $3 - number quads left to go
* $5 - target address (aligned 0mod64)
* $17 - mask of stuff to store
* Scratch registers available: $7, $2, $4, $1
* we know that we'll be taking a minimum of one trip through
* CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
* Assumes the wh64 needs to be for 2 trips through the loop in the future
* The wh64 is issued on for the starting destination address for trip +2
* through the loop, and if there are less than two trips left, the target
* address will be for the current trip.
*/
$do_wh64_b:
wh64 ($4) # L1 : memory subsystem write hint
subq $3, 24, $2 # E : For determining future wh64 addresses
stq $17, 0($5) # L :
nop # E :
addq $5, 128, $4 # E : speculative target of next wh64
stq $17, 8($5) # L :
stq $17, 16($5) # L :
addq $5, 64, $7 # E : Fallback address for wh64 (== next trip addr)
stq $17, 24($5) # L :
stq $17, 32($5) # L :
cmovlt $2, $7, $4 # E : Latency 2, extra mapping cycle
nop
stq $17, 40($5) # L :
stq $17, 48($5) # L :
subq $3, 16, $2 # E : Repeat the loop at least once more?
nop
stq $17, 56($5) # L :
addq $5, 64, $5 # E :
subq $3, 8, $3 # E :
bge $2, $do_wh64_b # U :
nop
nop
nop
beq $3, no_quad_b # U : Might have finished already
.align 4
/*
* Simple loop for trailing quadwords, or for small amounts
* of data (where we can't use an unrolled loop and wh64)
*/
loop_b:
stq $17,0($5) # L :
subq $3,1,$3 # E : Decrement number quads left
addq $5,8,$5 # E : Inc address
bne $3,loop_b # U : more?
no_quad_b:
/*
* Write 0..7 trailing bytes.
*/
nop # E :
beq $18,end_b # U : All done?
ldq $7,0($5) # L :
mskqh $7,$6,$2 # U : Mask final quad
insqh $17,$6,$4 # U : New bits
bis $2,$4,$1 # E : Put it all together
stq $1,0($5) # L : And back to memory
ret $31,($26),1 # L0 :
within_quad_b:
ldq_u $1,0($16) # L :
insql $17,$16,$2 # U : New bits
mskql $1,$16,$4 # U : Clear old
bis $2,$4,$2 # E : New result
mskql $2,$6,$4 # U :
mskqh $1,$6,$2 # U :
bis $2,$4,$1 # E :
stq_u $1,0($16) # L :
end_b:
nop
nop
nop
ret $31,($26),1 # L0 :
.end __memset
/*
* This is the original body of code, prior to replication and
* rescheduling. Leave it here, as there may be calls to this
* entry point.
*/
.align 4
.ent __constant_c_memset
__constant_c_memset:
.frame $30,0,$26,0
.prologue 0
addq $18,$16,$6 # E : max address to write to
bis $16,$16,$0 # E : return value
xor $16,$6,$1 # E : will complete write be within one quadword?
ble $18,end # U : zero length requested?
bic $1,7,$1 # E : fit within a single quadword
beq $1,within_one_quad # U :
and $16,7,$3 # E : Target addr misalignment
beq $3,aligned # U : target is 0mod8
/*
* Target address is misaligned, and won't fit within a quadword
*/
ldq_u $4,0($16) # L : Fetch first partial
bis $16,$16,$5 # E : Save the address
insql $17,$16,$2 # U : Insert new bytes
subq $3,8,$3 # E : Invert (for addressing uses)
addq $18,$3,$18 # E : $18 is new count ($3 is negative)
mskql $4,$16,$4 # U : clear relevant parts of the quad
subq $16,$3,$16 # E : $16 is new aligned destination
bis $2,$4,$1 # E : Final bytes
nop
stq_u $1,0($5) # L : Store result
nop
nop
.align 4
aligned:
/*
* We are now guaranteed to be quad aligned, with at least
* one partial quad to write.
*/
sra $18,3,$3 # U : Number of remaining quads to write
and $18,7,$18 # E : Number of trailing bytes to write
bis $16,$16,$5 # E : Save dest address
beq $3,no_quad # U : tail stuff only
/*
* it's worth the effort to unroll this and use wh64 if possible
* Lifted a bunch of code from clear_user.S
* At this point, entry values are:
* $16 Current destination address
* $5 A copy of $16
* $6 The max quadword address to write to
* $18 Number trailer bytes
* $3 Number quads to write
*/
and $16, 0x3f, $2 # E : Forward work (only useful for unrolled loop)
subq $3, 16, $4 # E : Only try to unroll if > 128 bytes
subq $2, 0x40, $1 # E : bias counter (aligning stuff 0mod64)
blt $4, loop # U :
/*
* We know we've got at least 16 quads, minimum of one trip
* through unrolled loop. Do a quad at a time to get us 0mod64
* aligned.
*/
nop # E :
nop # E :
nop # E :
beq $1, $bigalign # U :
$alignmod64:
stq $17, 0($5) # L :
subq $3, 1, $3 # E : For consistency later
addq $1, 8, $1 # E : Increment towards zero for alignment
addq $5, 8, $4 # E : Initial wh64 address (filler instruction)
nop
nop
addq $5, 8, $5 # E : Inc address
blt $1, $alignmod64 # U :
$bigalign:
/*
* $3 - number quads left to go
* $5 - target address (aligned 0mod64)
* $17 - mask of stuff to store
* Scratch registers available: $7, $2, $4, $1
* we know that we'll be taking a minimum of one trip through
* CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
* Assumes the wh64 needs to be for 2 trips through the loop in the future
* The wh64 is issued on for the starting destination address for trip +2
* through the loop, and if there are less than two trips left, the target
* address will be for the current trip.
*/
$do_wh64:
wh64 ($4) # L1 : memory subsystem write hint
subq $3, 24, $2 # E : For determining future wh64 addresses
stq $17, 0($5) # L :
nop # E :
addq $5, 128, $4 # E : speculative target of next wh64
stq $17, 8($5) # L :
stq $17, 16($5) # L :
addq $5, 64, $7 # E : Fallback address for wh64 (== next trip addr)
stq $17, 24($5) # L :
stq $17, 32($5) # L :
cmovlt $2, $7, $4 # E : Latency 2, extra mapping cycle
nop
stq $17, 40($5) # L :
stq $17, 48($5) # L :
subq $3, 16, $2 # E : Repeat the loop at least once more?
nop
stq $17, 56($5) # L :
addq $5, 64, $5 # E :
subq $3, 8, $3 # E :
bge $2, $do_wh64 # U :
nop
nop
nop
beq $3, no_quad # U : Might have finished already
.align 4
/*
* Simple loop for trailing quadwords, or for small amounts
* of data (where we can't use an unrolled loop and wh64)
*/
loop:
stq $17,0($5) # L :
subq $3,1,$3 # E : Decrement number quads left
addq $5,8,$5 # E : Inc address
bne $3,loop # U : more?
no_quad:
/*
* Write 0..7 trailing bytes.
*/
nop # E :
beq $18,end # U : All done?
ldq $7,0($5) # L :
mskqh $7,$6,$2 # U : Mask final quad
insqh $17,$6,$4 # U : New bits
bis $2,$4,$1 # E : Put it all together
stq $1,0($5) # L : And back to memory
ret $31,($26),1 # L0 :
within_one_quad:
ldq_u $1,0($16) # L :
insql $17,$16,$2 # U : New bits
mskql $1,$16,$4 # U : Clear old
bis $2,$4,$2 # E : New result
mskql $2,$6,$4 # U :
mskqh $1,$6,$2 # U :
bis $2,$4,$1 # E :
stq_u $1,0($16) # L :
end:
nop
nop
nop
ret $31,($26),1 # L0 :
.end __constant_c_memset
/*
* This is a replicant of the __constant_c_memset code, rescheduled
* to mask stalls. Note that entry point names also had to change
*/
.align 5
.ent __memsetw
__memsetw:
.frame $30,0,$26,0
.prologue 0
inswl $17,0,$5 # U : 000000000000c1c2
inswl $17,2,$2 # U : 00000000c1c20000
bis $16,$16,$0 # E : return value
addq $18,$16,$6 # E : max address to write to
ble $18, end_w # U : zero length requested?
inswl $17,4,$3 # U : 0000c1c200000000
inswl $17,6,$4 # U : c1c2000000000000
xor $16,$6,$1 # E : will complete write be within one quadword?
or $2,$5,$2 # E : 00000000c1c2c1c2
or $3,$4,$17 # E : c1c2c1c200000000
bic $1,7,$1 # E : fit within a single quadword
and $16,7,$3 # E : Target addr misalignment
or $17,$2,$17 # E : c1c2c1c2c1c2c1c2
beq $1,within_quad_w # U :
nop
beq $3,aligned_w # U : target is 0mod8
/*
* Target address is misaligned, and won't fit within a quadword
*/
ldq_u $4,0($16) # L : Fetch first partial
bis $16,$16,$5 # E : Save the address
insql $17,$16,$2 # U : Insert new bytes
subq $3,8,$3 # E : Invert (for addressing uses)
addq $18,$3,$18 # E : $18 is new count ($3 is negative)
mskql $4,$16,$4 # U : clear relevant parts of the quad
subq $16,$3,$16 # E : $16 is new aligned destination
bis $2,$4,$1 # E : Final bytes
nop
stq_u $1,0($5) # L : Store result
nop
nop
.align 4
aligned_w:
/*
* We are now guaranteed to be quad aligned, with at least
* one partial quad to write.
*/
sra $18,3,$3 # U : Number of remaining quads to write
and $18,7,$18 # E : Number of trailing bytes to write
bis $16,$16,$5 # E : Save dest address
beq $3,no_quad_w # U : tail stuff only
/*
* it's worth the effort to unroll this and use wh64 if possible
* Lifted a bunch of code from clear_user.S
* At this point, entry values are:
* $16 Current destination address
* $5 A copy of $16
* $6 The max quadword address to write to
* $18 Number trailer bytes
* $3 Number quads to write
*/
and $16, 0x3f, $2 # E : Forward work (only useful for unrolled loop)
subq $3, 16, $4 # E : Only try to unroll if > 128 bytes
subq $2, 0x40, $1 # E : bias counter (aligning stuff 0mod64)
blt $4, loop_w # U :
/*
* We know we've got at least 16 quads, minimum of one trip
* through unrolled loop. Do a quad at a time to get us 0mod64
* aligned.
*/
nop # E :
nop # E :
nop # E :
beq $1, $bigalign_w # U :
$alignmod64_w:
stq $17, 0($5) # L :
subq $3, 1, $3 # E : For consistency later
addq $1, 8, $1 # E : Increment towards zero for alignment
addq $5, 8, $4 # E : Initial wh64 address (filler instruction)
nop
nop
addq $5, 8, $5 # E : Inc address
blt $1, $alignmod64_w # U :
$bigalign_w:
/*
* $3 - number quads left to go
* $5 - target address (aligned 0mod64)
* $17 - mask of stuff to store
* Scratch registers available: $7, $2, $4, $1
* we know that we'll be taking a minimum of one trip through
* CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
* Assumes the wh64 needs to be for 2 trips through the loop in the future
* The wh64 is issued on for the starting destination address for trip +2
* through the loop, and if there are less than two trips left, the target
* address will be for the current trip.
*/
$do_wh64_w:
wh64 ($4) # L1 : memory subsystem write hint
subq $3, 24, $2 # E : For determining future wh64 addresses
stq $17, 0($5) # L :
nop # E :
addq $5, 128, $4 # E : speculative target of next wh64
stq $17, 8($5) # L :
stq $17, 16($5) # L :
addq $5, 64, $7 # E : Fallback address for wh64 (== next trip addr)
stq $17, 24($5) # L :
stq $17, 32($5) # L :
cmovlt $2, $7, $4 # E : Latency 2, extra mapping cycle
nop
stq $17, 40($5) # L :
stq $17, 48($5) # L :
subq $3, 16, $2 # E : Repeat the loop at least once more?
nop
stq $17, 56($5) # L :
addq $5, 64, $5 # E :
subq $3, 8, $3 # E :
bge $2, $do_wh64_w # U :
nop
nop
nop
beq $3, no_quad_w # U : Might have finished already
.align 4
/*
* Simple loop for trailing quadwords, or for small amounts
* of data (where we can't use an unrolled loop and wh64)
*/
loop_w:
stq $17,0($5) # L :
subq $3,1,$3 # E : Decrement number quads left
addq $5,8,$5 # E : Inc address
bne $3,loop_w # U : more?
no_quad_w:
/*
* Write 0..7 trailing bytes.
*/
nop # E :
beq $18,end_w # U : All done?
ldq $7,0($5) # L :
mskqh $7,$6,$2 # U : Mask final quad
insqh $17,$6,$4 # U : New bits
bis $2,$4,$1 # E : Put it all together
stq $1,0($5) # L : And back to memory
ret $31,($26),1 # L0 :
within_quad_w:
ldq_u $1,0($16) # L :
insql $17,$16,$2 # U : New bits
mskql $1,$16,$4 # U : Clear old
bis $2,$4,$2 # E : New result
mskql $2,$6,$4 # U :
mskqh $1,$6,$2 # U :
bis $2,$4,$1 # E :
stq_u $1,0($16) # L :
end_w:
nop
nop
nop
ret $31,($26),1 # L0 :
.end __memsetw
memset = __memset
