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dnl Alpha ev6 mpn_sub_n -- Subtract two limb vectors of the same length > 0
dnl and store difference in a third limb vector.
dnl Copyright 2000, 2003, 2005 Free Software Foundation, Inc.
dnl This file is part of the GNU MP Library.
dnl
dnl The GNU MP Library is free software; you can redistribute it and/or modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://www.gnu.org/licenses/.
include(`../config.m4')
C cycles/limb
C EV4: ?
C EV5: 5.4
C EV6: 2.125
C INPUT PARAMETERS
C rp r16
C up r17
C vp r18
C n r19
C cy r20 (for mpn_add_nc)
C TODO
C Finish cleaning up cy registers r22, r23 (make them use cy0/cy1)
C Use multi-pronged feed-in.
C Perform additional micro-tuning
C This code was written in cooperation with ev6 pipeline expert Steve Root.
C Pair loads and stores where possible
C Store pairs oct-aligned where possible (didn't need it here)
C Stores are delayed every third cycle
C Loads and stores are delayed by fills
C U stays still, put code there where possible (note alternation of U1 and U0)
C L moves because of loads and stores
C Note dampers in L to limit damage
C This odd-looking optimization expects that were having random bits in our
C data, so that a pure zero result is unlikely. so we penalize the unlikely
C case to help the common case.
define(`u0', `r0') define(`u1', `r3')
define(`v0', `r1') define(`v1', `r4')
define(`cy0', `r20') define(`cy1', `r21')
MULFUNC_PROLOGUE(mpn_sub_n mpn_sub_nc)
ASM_START()
PROLOGUE(mpn_sub_nc)
br r31, $entry
EPILOGUE()
PROLOGUE(mpn_sub_n)
bis r31, r31, cy0 C clear carry in
$entry: cmpult r19, 5, r22 C L1 move counter
ldq u1, 0(r17) C L0 get next ones
ldq v1, 0(r18) C L1
bne r22, $Lsmall
ldq u0, 8(r17) C L0 get next ones
ldq v0, 8(r18) C L1
subq u1, v1, r5 C U0 sub two data
cmpult u1, v1, r23 C U0 did it borrow
ldq u1, 16(r17) C L0 get next ones
ldq v1, 16(r18) C L1
subq u0, v0, r8 C U1 sub two data
subq r5, cy0, r24 C U0 borrow in
cmpult u0, v0, r22 C U1 did it borrow
beq r5, $fix5f C U0 fix exact zero
$ret5f: ldq u0, 24(r17) C L0 get next ones
ldq v0, 24(r18) C L1
subq r8, r23, r25 C U1 borrow from last
subq u1, v1, r7 C U0 sub two data
beq r8, $fix6f C U1 fix exact zero
$ret6f: cmpult u1, v1, r23 C U0 did it borrow
ldq u1, 32(r17) C L0 get next ones
ldq v1, 32(r18) C L1
lda r17, 40(r17) C L0 move pointer
lda r18, 40(r18) C L1 move pointer
lda r16, -8(r16)
lda r19, -13(r19) C L1 move counter
blt r19, $Lend C U1 loop control
C Main loop. 8-way unrolled.
ALIGN(16)
$Loop: subq u0, v0, r2 C U1 sub two data
stq r24, 8(r16) C L0 put an answer
subq r7, r22, r24 C U0 borrow from last
stq r25, 16(r16) C L1 pair
cmpult u0, v0, cy1 C U1 did it borrow
beq r7, $fix7 C U0 fix exact 0
$ret7: ldq u0, 0(r17) C L0 get next ones
ldq v0, 0(r18) C L1
bis r31, r31, r31 C L damp out
subq r2, r23, r25 C U1 borrow from last
bis r31, r31, r31 C L moves in L !
subq u1, v1, r5 C U0 sub two data
beq r2, $fix0 C U1 fix exact zero
$ret0: cmpult u1, v1, cy0 C U0 did it borrow
ldq u1, 8(r17) C L0 get next ones
ldq v1, 8(r18) C L1
subq u0, v0, r8 C U1 sub two data
stq r24, 24(r16) C L0 store pair
subq r5, cy1, r24 C U0 borrow from last
stq r25, 32(r16) C L1
cmpult u0, v0, r22 C U1 did it borrow
beq r5, $fix1 C U0 fix exact zero
$ret1: ldq u0, 16(r17) C L0 get next ones
ldq v0, 16(r18) C L1
lda r16, 64(r16) C L0 move pointer
subq r8, cy0, r25 C U1 borrow from last
lda r19, -8(r19) C L1 move counter
subq u1, v1, r7 C U0 sub two data
beq r8, $fix2 C U1 fix exact zero
$ret2: cmpult u1, v1, r23 C U0 did it borrow
ldq u1, 24(r17) C L0 get next ones
ldq v1, 24(r18) C L1
subq u0, v0, r2 C U1 sub two data
stq r24, -24(r16) C L0 put an answer
subq r7, r22, r24 C U0 borrow from last
stq r25, -16(r16) C L1 pair
cmpult u0, v0, cy1 C U1 did it borrow
beq r7, $fix3 C U0 fix exact 0
$ret3: ldq u0, 32(r17) C L0 get next ones
ldq v0, 32(r18) C L1
bis r31, r31, r31 C L damp out
subq r2, r23, r25 C U1 borrow from last
bis r31, r31, r31 C L moves in L !
subq u1, v1, r5 C U0 sub two data
beq r2, $fix4 C U1 fix exact zero
$ret4: cmpult u1, v1, cy0 C U0 did it borrow
ldq u1, 40(r17) C L0 get next ones
ldq v1, 40(r18) C L1
subq u0, v0, r8 C U1 sub two data
stq r24, -8(r16) C L0 store pair
subq r5, cy1, r24 C U0 borrow from last
stq r25, 0(r16) C L1
cmpult u0, v0, r22 C U1 did it borrow
beq r5, $fix5 C U0 fix exact zero
$ret5: ldq u0, 48(r17) C L0 get next ones
ldq v0, 48(r18) C L1
ldl r31, 256(r17) C L0 prefetch
subq r8, cy0, r25 C U1 borrow from last
ldl r31, 256(r18) C L1 prefetch
subq u1, v1, r7 C U0 sub two data
beq r8, $fix6 C U1 fix exact zero
$ret6: cmpult u1, v1, r23 C U0 did it borrow
ldq u1, 56(r17) C L0 get next ones
ldq v1, 56(r18) C L1
lda r17, 64(r17) C L0 move pointer
bis r31, r31, r31 C U
lda r18, 64(r18) C L1 move pointer
bge r19, $Loop C U1 loop control
C ==== main loop end
$Lend: subq u0, v0, r2 C U1 sub two data
stq r24, 8(r16) C L0 put an answer
subq r7, r22, r24 C U0 borrow from last
stq r25, 16(r16) C L1 pair
cmpult u0, v0, cy1 C U1 did it borrow
beq r7, $fix7c C U0 fix exact 0
$ret7c: subq r2, r23, r25 C U1 borrow from last
subq u1, v1, r5 C U0 sub two data
beq r2, $fix0c C U1 fix exact zero
$ret0c: cmpult u1, v1, cy0 C U0 did it borrow
stq r24, 24(r16) C L0 store pair
subq r5, cy1, r24 C U0 borrow from last
stq r25, 32(r16) C L1
beq r5, $fix1c C U0 fix exact zero
$ret1c: stq r24, 40(r16) C L0 put an answer
lda r16, 48(r16) C L0 move pointer
lda r19, 8(r19)
beq r19, $Lret
ldq u1, 0(r17)
ldq v1, 0(r18)
$Lsmall:
lda r19, -1(r19)
beq r19, $Lend0
ALIGN(8)
$Loop0: subq u1, v1, r2 C main sub
cmpult u1, v1, r8 C compute bw from last sub
ldq u1, 8(r17)
ldq v1, 8(r18)
subq r2, cy0, r5 C borrow sub
lda r17, 8(r17)
lda r18, 8(r18)
stq r5, 0(r16)
cmpult r2, cy0, cy0 C compute bw from last sub
lda r19, -1(r19) C decr loop cnt
bis r8, cy0, cy0 C combine bw from the two subs
lda r16, 8(r16)
bne r19, $Loop0
$Lend0: subq u1, v1, r2 C main sub
subq r2, cy0, r5 C borrow sub
cmpult u1, v1, r8 C compute bw from last sub
cmpult r2, cy0, cy0 C compute bw from last sub
stq r5, 0(r16)
bis r8, cy0, r0 C combine bw from the two subs
ret r31,(r26),1
ALIGN(8)
$Lret: lda r0, 0(cy0) C copy borrow into return register
ret r31,(r26),1
$fix5f: bis r23, cy0, r23 C bring forward borrow
br r31, $ret5f
$fix6f: bis r22, r23, r22 C bring forward borrow
br r31, $ret6f
$fix0: bis cy1, r23, cy1 C bring forward borrow
br r31, $ret0
$fix1: bis cy0, cy1, cy0 C bring forward borrow
br r31, $ret1
$fix2: bis r22, cy0, r22 C bring forward borrow
br r31, $ret2
$fix3: bis r23, r22, r23 C bring forward borrow
br r31, $ret3
$fix4: bis cy1, r23, cy1 C bring forward borrow
br r31, $ret4
$fix5: bis cy1, cy0, cy0 C bring forward borrow
br r31, $ret5
$fix6: bis r22, cy0, r22 C bring forward borrow
br r31, $ret6
$fix7: bis r23, r22, r23 C bring forward borrow
br r31, $ret7
$fix0c: bis cy1, r23, cy1 C bring forward borrow
br r31, $ret0c
$fix1c: bis cy0, cy1, cy0 C bring forward borrow
br r31, $ret1c
$fix7c: bis r23, r22, r23 C bring forward borrow
br r31, $ret7c
EPILOGUE()
ASM_END()
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