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Diffstat (limited to 'arch/alpha/lib/ev6-memset.S')
| -rw-r--r-- | arch/alpha/lib/ev6-memset.S | 597 |
1 files changed, 597 insertions, 0 deletions
diff --git a/arch/alpha/lib/ev6-memset.S b/arch/alpha/lib/ev6-memset.S new file mode 100644 index 0000000..d8b94e1 --- /dev/null +++ b/arch/alpha/lib/ev6-memset.S @@ -0,0 +1,597 @@ +/* + * 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 |