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[/] [or1k_soc_on_altera_embedded_dev_kit/] [trunk/] [linux-2.6/] [linux-2.6.24/] [arch/] [alpha/] [lib/] [ev6-memcpy.S] - Rev 3
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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 memcpymemcpy:.frame $30,0,$26,0.prologue 0mov $16, $0 # E : copy dest to returnble $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, $both_0mod8 # U : Yesnop # E :/** source and dest are same misalignment. move a byte at a time* until a 0mod8 alignment for both is reached.* At least one byte more to move*/$head_align:ldbu $1, 0($17) # L : grab a bytesubq $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 alignmentbeq $1, $do_unroll # U : no single quads to fiddle$single_head_quad:ldq $1, 0($17) # L : get 8 bytessubq $18, 8, $18 # E : count -= 8addq $17, 8, $17 # E : src += 8nop # E :stq $1, 0($16) # L : storeaddq $16, 8, $16 # E : dest += 8and $16, 63, $1 # E : get mod64 alignmentbne $1, $single_head_quad # U : still not fully aligned$do_unroll:addq $16, 64, $7 # E : Initial (+1 trip) wh64 addresscmple $18, 127, $1 # E : Can we go through the unrolled loop?bne $1, $tail_quads # U : Nopenop # E :$unroll_body:wh64 ($7) # L1 : memory subsystem hint: 64 bytes at# ($7) are about to be over-writtenldq $6, 0($17) # L0 : bytes 0..7nop # E :nop # E :ldq $4, 8($17) # L : bytes 8..15ldq $5, 16($17) # L : bytes 16..23addq $7, 64, $7 # E : Update next wh64 addressnop # E :ldq $3, 24($17) # L : bytes 24..31addq $16, 64, $1 # E : fallback value for wh64nop # E :nop # E :addq $17, 32, $17 # E : src += 32 bytesstq $6, 0($16) # L : bytes 0..7nop # E :nop # E :stq $4, 8($16) # L : bytes 8..15stq $5, 16($16) # L : bytes 16..23subq $18, 192, $2 # E : At least two more trips to go?nop # E :stq $3, 24($16) # L : bytes 24..31addq $16, 32, $16 # E : dest += 32 bytesnop # E :nop # E :ldq $6, 0($17) # L : bytes 0..7ldq $4, 8($17) # L : bytes 8..15cmovlt $2, $1, $7 # E : Latency 2, extra map slot - Use# fallback wh64 address if < 2 more tripsnop # E :ldq $5, 16($17) # L : bytes 16..23ldq $3, 24($17) # L : bytes 24..31addq $16, 32, $16 # E : dest += 32subq $18, 64, $18 # E : count -= 64addq $17, 32, $17 # E : src += 32stq $6, -32($16) # L : bytes 0..7stq $4, -24($16) # L : bytes 8..15cmple $18, 63, $1 # E : At least one more trip?stq $5, -16($16) # L : bytes 16..23stq $3, -8($16) # L : bytes 24..31nop # E :beq $1, $unroll_body$tail_quads:$no_unroll:.align 4subq $18, 8, $18 # E : At least a quad left?blt $18, $less_than_8 # U : Nopenop # E :nop # E :$move_a_quad:ldq $1, 0($17) # L : fetch 8subq $18, 8, $18 # E : count -= 8addq $17, 8, $17 # E : src += 8nop # E :stq $1, 0($16) # L : store 8addq $16, 8, $16 # E : dest += 8bge $18, $move_a_quad # U :nop # E :$less_than_8:.align 4addq $18, 8, $18 # E : add back for trailing bytesble $18, $nomoredata # U : All-donenop # E :nop # E :/* Trailing bytes */$tail_bytes:subq $18, 1, $18 # E : count--ldbu $1, 0($17) # L : fetch a byteaddq $17, 1, $17 # E : src++nop # E :stb $1, 0($16) # L : store a byteaddq $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 tempand $0, 7, $1 # E : dest alignment mod8beq $1, $dest_0mod8 # U : life doesnt totally sucknop$aligndest:ble $18, $nomoredata # U :ldbu $1, 0($17) # L : fetch a bytesubq $18, 1, $18 # E : count--addq $17, 1, $17 # E : src++stb $1, 0($4) # L : store itaddq $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 : Nopeldq_u $3, 0($17) # L : seed (rotating load) of 8 bytesnop # E :$mis_quad:ldq_u $16, 8($17) # L : Fetch next 8extql $3, $17, $3 # U : maskingextqh $16, $17, $1 # U : maskingbis $3, $1, $1 # E : merged bytes to storesubq $18, 8, $18 # E : count -= 8addq $17, 8, $17 # E : src += 8stq $1, 0($4) # L : store 8 (aligned)mov $16, $3 # E : "rotate" source dataaddq $4, 8, $4 # E : dest += 8bge $18, $mis_quad # U : More quads to movenopnop$misalign_tail:addq $18, 8, $18 # E : account for tail stuffble $18, $nomoredata # U :nopnop$misalign_byte:ldbu $1, 0($17) # L : fetch 1subq $18, 1, $18 # E : count--addq $17, 1, $17 # E : src++nop # E :stb $1, 0($4) # L : storeaddq $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