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dnl Alpha mpn_divrem_2 -- Divide an mpn number by a normalized 2-limb number.
dnl Copyright 2007, 2008, 2013 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 norm frac
C ev4
C ev5 70 70
C ev6 29 29
C TODO
C * Perhaps inline mpn_invert_limb, that would allow us to not save/restore
C any registers (thus save ~10 cycles per call).
C * Use negated d1 and/or d0 to speed carry propagation. Might save a cycle
C or two.
C * Check cluster delays (for ev6). We very likely could save some cycles.
C * Use branch-free code for computing di.
C * CAVEAT: We rely on r19 not being clobbered by mpn_invert_limb call.
C INPUT PARAMETERS
define(`qp', `r16')
define(`fn', `r17')
define(`up_param', `r18')
define(`un_param', `r19')
define(`dp', `r20')
ASM_START()
PROLOGUE(mpn_divrem_2,gp)
lda r30, -80(r30)
stq r26, 0(r30)
stq r9, 8(r30)
stq r10, 16(r30)
stq r11, 24(r30)
stq r12, 32(r30)
stq r13, 40(r30)
C stq r14, 48(r30)
stq r15, 56(r30)
.prologue 1
stq r16, 64(r30)
bis r31, r17, r15
s8addq r19, r18, r13
lda r13, -24(r13)
ldq r12, 8(r20)
ldq r10, 0(r20)
ldq r11, 16(r13)
ldq r9, 8(r13)
bis r31, r31, r3 C most_significant_q_limb = 0
cmpult r11, r12, r1
bne r1, L(L8)
cmpule r11, r12, r1
cmpult r9, r10, r2
and r1, r2, r1
bne r1, L(L8)
subq r11, r12, r11
subq r11, r2, r11
subq r9, r10, r9
lda r3, 1(r31) C most_significant_q_limb = 1
L(L8): stq r3, 72(r30)
addq r15, r19, r19
lda r19, -3(r19)
blt r19, L(L10)
bis r31, r12, r16
jsr r26, mpn_invert_limb
LDGP( r29, 0(r26))
mulq r0, r12, r4 C t0 = LO(di * d1)
umulh r0, r10, r2 C s1 = HI(di * d0)
addq r4, r10, r4 C t0 += d0
cmpule r10, r4, r7 C (t0 < d0)
addq r4, r2, r4 C t0 += s1
cmpult r4, r2, r1
subq r1, r7, r7 C t1 (-1, 0, or 1)
blt r7, L(L42)
L(L22):
lda r0, -1(r0) C di--
cmpult r4, r12, r1 C cy for: t0 -= d1 (below)
subq r7, r1, r7 C t1 -= cy
subq r4, r12, r4 C t0 -= d1
bge r7, L(L22)
L(L42):
ldq r16, 64(r30)
s8addq r19, r16, r16
ALIGN(16)
L(loop):
mulq r11, r0, r5 C q0 (early)
umulh r11, r0, r6 C q (early)
addq r5, r9, r8 C q0 += n1
addq r6, r11, r6 C q += n2
cmpult r8, r5, r1 C cy for: q0 += n1
addq r6, r1, r6 C q += cy
unop
mulq r12, r6, r1 C LO(d1 * q)
umulh r10, r6, r7 C t1 = HI(d0 * q)
subq r9, r1, r9 C n1 -= LO(d1 * q)
mulq r10, r6, r4 C t0 = LO(d0 * q)
unop
cmple r15, r19, r5 C condition and n0...
beq r5, L(L31)
ldq r5, 0(r13)
lda r13, -8(r13)
L(L31): subq r9, r12, r9 C n1 -= d1
cmpult r5, r10, r1 C
subq r9, r1, r9 C
subq r5, r10, r5 C n0 -= d0
subq r9, r7, r9 C n1 -= t0
cmpult r5, r4, r1 C
subq r9, r1, r2 C
subq r5, r4, r5 C n0 -= t1
cmpult r2, r8, r1 C (n1 < q0)
addq r6, r1, r6 C q += cond
lda r1, -1(r1) C -(n1 >= q0)
and r1, r10, r4 C
addq r5, r4, r9 C n0 += mask & d0
and r1, r12, r1 C
cmpult r9, r5, r11 C cy for: n0 += mask & d0
addq r2, r1, r1 C n1 += mask & d1
addq r1, r11, r11 C n1 += cy
cmpult r11, r12, r1 C
beq r1, L(fix) C
L(bck): stq r6, 0(r16)
lda r16, -8(r16)
lda r19, -1(r19)
bge r19, L(loop)
L(L10): stq r9, 8(r13)
stq r11, 16(r13)
ldq r0, 72(r30)
ldq r26, 0(r30)
ldq r9, 8(r30)
ldq r10, 16(r30)
ldq r11, 24(r30)
ldq r12, 32(r30)
ldq r13, 40(r30)
C ldq r14, 48(r30)
ldq r15, 56(r30)
lda r30, 80(r30)
ret r31, (r26), 1
L(fix): cmpule r11, r12, r1
cmpult r9, r10, r2
and r1, r2, r1
bne r1, L(bck)
subq r11, r12, r11
subq r11, r2, r11
subq r9, r10, r9
lda r6, 1(r6)
br L(bck)
EPILOGUE()
ASM_END()
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