--- /dev/null
+/*
+ * 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 __memset
+ .globl ___memset
+ .globl __memsetw
+ .globl __constant_c_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
+__memset = ___memset
Code Review / kvmfornfv.git / blobdiff