1; mc88100 mpn_sub_n -- Subtract two limb vectors of the same length > 0 and
2; store difference in a third limb vector.
3
4; Copyright 1992, 1994, 1996, 2000 Free Software Foundation, Inc.
5
6;  This file is part of the GNU MP Library.
7;
8;  The GNU MP Library is free software; you can redistribute it and/or modify
9;  it under the terms of either:
10;
11;    * the GNU Lesser General Public License as published by the Free
12;      Software Foundation; either version 3 of the License, or (at your
13;      option) any later version.
14;
15;  or
16;
17;    * the GNU General Public License as published by the Free Software
18;      Foundation; either version 2 of the License, or (at your option) any
19;      later version.
20;
21;  or both in parallel, as here.
22;
23;  The GNU MP Library is distributed in the hope that it will be useful, but
24;  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25;  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
26;  for more details.
27;
28;  You should have received copies of the GNU General Public License and the
29;  GNU Lesser General Public License along with the GNU MP Library.  If not,
30;  see https://www.gnu.org/licenses/.
31
32
33; INPUT PARAMETERS
34; res_ptr r2
35; s1_ptr  r3
36; s2_ptr  r4
37; size              r5
38
39; This code has been optimized to run one instruction per clock, avoiding
40; load stalls and writeback contention.  As a result, the instruction
41; order is not always natural.
42
43; The speed is about 4.6 clocks/limb + 18 clocks/limb-vector on an 88100,
44; but on the 88110, it seems to run much slower, 6.6 clocks/limb.
45
46          text
47          align      16
48          global     ___gmpn_sub_n
49___gmpn_sub_n:
50          ld        r6,r3,0                       ; read first limb from s1_ptr
51          extu      r10,r5,3
52          ld        r7,r4,0                       ; read first limb from s2_ptr
53
54          subu      r5,r0,r5
55          mak       r5,r5,3<4>
56          bcnd.n    eq0,r5,Lzero
57          subu.co   r0,r0,r0            ; initialize carry
58
59          or        r12,r0,lo16(Lbase)
60          or.u      r12,r12,hi16(Lbase)
61          addu      r12,r12,r5                    ; r12 is address for entering in loop
62
63          extu      r5,r5,2                       ; divide by 4
64          subu      r2,r2,r5            ; adjust res_ptr
65          subu      r3,r3,r5            ; adjust s1_ptr
66          subu      r4,r4,r5            ; adjust s2_ptr
67
68          or        r8,r6,r0
69
70          jmp.n     r12
71           or       r9,r7,r0
72
73Loop:     addu      r3,r3,32
74          st        r8,r2,28
75          addu      r4,r4,32
76          ld        r6,r3,0
77          addu      r2,r2,32
78          ld        r7,r4,0
79Lzero:    subu      r10,r10,1           ; subtract 0 + 8r limbs (adj loop cnt)
80Lbase:    ld        r8,r3,4
81          subu.cio r6,r6,r7
82          ld        r9,r4,4
83          st        r6,r2,0
84          ld        r6,r3,8                       ; subtract 7 + 8r limbs
85          subu.cio r8,r8,r9
86          ld        r7,r4,8
87          st        r8,r2,4
88          ld        r8,r3,12            ; subtract 6 + 8r limbs
89          subu.cio r6,r6,r7
90          ld        r9,r4,12
91          st        r6,r2,8
92          ld        r6,r3,16            ; subtract 5 + 8r limbs
93          subu.cio r8,r8,r9
94          ld        r7,r4,16
95          st        r8,r2,12
96          ld        r8,r3,20            ; subtract 4 + 8r limbs
97          subu.cio r6,r6,r7
98          ld        r9,r4,20
99          st        r6,r2,16
100          ld        r6,r3,24            ; subtract 3 + 8r limbs
101          subu.cio r8,r8,r9
102          ld        r7,r4,24
103          st        r8,r2,20
104          ld        r8,r3,28            ; subtract 2 + 8r limbs
105          subu.cio r6,r6,r7
106          ld        r9,r4,28
107          st        r6,r2,24
108          bcnd.n    ne0,r10,Loop                  ; subtract 1 + 8r limbs
109           subu.cio r8,r8,r9
110
111          st        r8,r2,28            ; store most significant limb
112
113          addu.ci r2,r0,r0              ; return carry-out from most sign. limb
114          jmp.n      r1
115           xor      r2,r2,1
116