--- /dev/null
+dnl PowerPC-32 mpn_modexact_1_odd -- mpn by limb exact remainder.
+
+dnl Copyright 2002, 2003, 2005, 2006 Free Software Foundation, Inc.
+dnl
+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
+dnl modify it under the terms of the GNU Lesser General Public License as
+dnl published by the Free Software Foundation; either version 3 of the
+dnl License, or (at your option) any later version.
+dnl
+dnl The GNU MP Library is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+dnl Lesser General Public License for more details.
+dnl
+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 603e: ?
+C 604e: 6.0
+C 75x (G3): 6.0-13.0, depending on divisor
+C 7400,7410 (G4): 6.0-13.0, depending on divisor
+C 744x,745x (G4+): 8.0-10.0, depending on divisor
+C power4/ppc970: 12.0
+C power5: 12.0
+
+
+C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size,
+C mp_limb_t divisor);
+C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size,
+C mp_limb_t divisor, mp_limb_t carry);
+C
+C For PIC, the inverse is established arithmetically since it measures about
+C 5 cycles faster than the nonsense needed to access binvert_limb_table in
+C SVR4 or Darwin style PIC. AIX might be better, since it avoids bl/mflr to
+C get at the GOT/TOC/whatever.
+C
+C Using divwu for size==1 measured about 10 cycles slower on 604e, or about
+C 3-5 cycles faster on 750. For now it doesn't seem worth bothering with.
+C
+C The loop allows an early-out on mullw for the inverse, and on mulhwu for
+C the divisor. So the fastest is for instance divisor==1 (inverse==-1), and
+C the slowest is anything giving a full 32-bits in both, such as
+C divisor==0xDEADBEEF (inverse==0x904B300F). These establish the stated
+C range above for 750 and 7400.
+
+
+ASM_START()
+
+EXTERN(binvert_limb_table)
+
+PROLOGUE(mpn_modexact_1_odd)
+ li r6, 0
+
+PROLOGUE(mpn_modexact_1c_odd)
+
+ mtctr r4 C size
+
+ifdef(`PIC_SLOW',`
+C Load from our table with PIC is so slow on Linux and Darwin that we avoid it
+ rlwinm r7, r5, 1,28,28 C (divisor << 1) & 8
+ rlwinm r8, r5, 2,28,28 C (divisor << 2) & 8
+ xor r7, r7, r8 C ((divisor << 1) ^ (divisor << 2)) & 8
+ rlwinm r4, r5, 0,28,31 C divisor low 4 bits, speedup mullw
+ xor r4, r4, r7 C inverse, 4 bits
+ mullw r7, r4, r4 C i*i
+ slwi r4, r4, 1 C 2*i
+ rlwinm r8, r5, 0,24,31 C divisor low 8 bits, speedup mullw
+ mullw r7, r7, r8 C i*i*d
+ sub r4, r4, r7 C inverse, 8 bits
+',`
+ LEA( r7, binvert_limb_table)
+ rlwinm r4, r5, 31,25,31 C (divisor/2) & 0x7F
+ lbzx r4, r4,r7 C inverse, 8 bits
+')
+
+ mullw r7, r4, r4 C i*i
+ slwi r4, r4, 1 C 2*i
+ mullw r7, r5, r7 C i*i*d [i*i is 16 bits, so second operand]
+ sub r4, r4, r7 C inverse, 16 bits
+ mullw r7, r4, r4 C i*i
+ slwi r4, r4, 1 C 2*i
+ mullw r7, r7, r5 C i*i*d
+ lwz r0, 0(r3) C src[0]
+ sub r4, r4, r7 C inverse, 32 bits
+ subfc r7, r6, r0 C l = src[0] - carry
+
+ mullw r7, r7, r4 C q = l * inverse
+ bdz L(one)
+
+ lwzu r0, 4(r3) C src[1]
+ mulhwu r6, r7, r5 C carry = high(q*divisor)
+ subfe r7, r6, r0 C l = src[1] - carry
+ bdz L(two)
+
+L(top):
+ mullw r7, r7, r4 C q = l * inverse
+ lwzu r0, 4(r3) C src[i]
+ mulhwu r6, r7, r5 C carry = high(q*divisor)
+ subfe r7, r6, r0 C l = src[i] - carry
+ bdnz L(top)
+
+L(two): mullw r7, r7, r4 C q = l * inverse
+L(one): subfe r3, r3, r3 C ca 0 or -1
+ mulhwu r6, r7, r5 C carry = high(q*divisor)
+ subf r3, r3, r6 C carry + ca
+ blr
+
+EPILOGUE(mpn_modexact_1c_odd)
+EPILOGUE(mpn_modexact_1_odd)
+ASM_END()
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