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 The GNU MP Library is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU Lesser General Public License as published
dnl by the Free Software Foundation; either version 3 of the License, or (at
dnl your option) any later version.
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 Lesser General Public
dnl License for more details.
dnl You should have received a copy of the GNU Lesser General Public License
dnl along with the GNU MP Library. If not, see http://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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