File Coverage

src/int/i15_montmul.c

Criterion	Covered	Total	%
statement	0	37	0.0
branch	0	6	0.0
condition			n/a
subroutine			n/a
pod			n/a
total	0	43	0.0

line	stmt	bran	code
1			/*
2			* Copyright (c) 2017 Thomas Pornin
3			*
4			* Permission is hereby granted, free of charge, to any person obtaining
5			* a copy of this software and associated documentation files (the
6			* "Software"), to deal in the Software without restriction, including
7			* without limitation the rights to use, copy, modify, merge, publish,
8			* distribute, sublicense, and/or sell copies of the Software, and to
9			* permit persons to whom the Software is furnished to do so, subject to
10			* the following conditions:
11			*
12			* The above copyright notice and this permission notice shall be
13			* included in all copies or substantial portions of the Software.
14			*
15			* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16			* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17			* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18			* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19			* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20			* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21			* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22			* SOFTWARE.
23			*/
24
25			#include "inner.h"
26
27			/* see inner.h */
28			void
29	0		br_i15_montymul(uint16_t d, const uint16_t x, const uint16_t *y,
30			const uint16_t *m, uint16_t m0i)
31			{
32			size_t len, len4, u, v;
33			uint32_t dh;
34
35	0		len = (m[0] + 15) >> 4;
36	0		len4 = len & ~(size_t)3;
37	0		br_i15_zero(d, m[0]);
38	0		dh = 0;
39	0	0	for (u = 0; u < len; u ++) {
40			uint32_t f, xu, r, zh;
41
42	0		xu = x[u + 1];
43	0		f = MUL15((d[1] + MUL15(x[u + 1], y[1])) & 0x7FFF, m0i)
44			& 0x7FFF;
45			#if BR_ARMEL_CORTEXM_GCC
46			if (len4 != 0) {
47			uint16_t *limit;
48
49			limit = d + len4;
50			asm volatile (
51			"\n\
52			@ carry: r=r2 \n\
53			@ multipliers: xu=r3 f=r4 \n\
54			@ base registers: d+v=r5 y+v=r6 m+v=r7 \n\
55			@ r8 contains 0x7FFF \n\
56			@ r9 contains d+len4 \n\
57			ldr r0, %[limit] \n\
58			ldr r3, %[xu] \n\
59			mov r9, r0 \n\
60			ldr r4, %[f] \n\
61			eor r2, r2 \n\
62			ldr r5, %[d] \n\
63			sub r1, r2, #1 \n\
64			ldr r6, %[y] \n\
65			lsr r1, r1, #17 \n\
66			ldr r7, %[m] \n\
67			mov r8, r1 \n\
68			loop%=: \n\
69			ldrh r0, [r6, #2] \n\
70			ldrh r1, [r7, #2] \n\
71			mul r0, r3 \n\
72			mul r1, r4 \n\
73			add r2, r0, r2 \n\
74			ldrh r0, [r5, #2] \n\
75			add r2, r1, r2 \n\
76			mov r1, r8 \n\
77			add r2, r0, r2 \n\
78			and r1, r2 \n\
79			lsr r2, r2, #15 \n\
80			strh r1, [r5, #0] \n\
81			\n\
82			ldrh r0, [r6, #4] \n\
83			ldrh r1, [r7, #4] \n\
84			mul r0, r3 \n\
85			mul r1, r4 \n\
86			add r2, r0, r2 \n\
87			ldrh r0, [r5, #4] \n\
88			add r2, r1, r2 \n\
89			mov r1, r8 \n\
90			add r2, r0, r2 \n\
91			and r1, r2 \n\
92			lsr r2, r2, #15 \n\
93			strh r1, [r5, #2] \n\
94			\n\
95			ldrh r0, [r6, #6] \n\
96			ldrh r1, [r7, #6] \n\
97			mul r0, r3 \n\
98			mul r1, r4 \n\
99			add r2, r0, r2 \n\
100			ldrh r0, [r5, #6] \n\
101			add r2, r1, r2 \n\
102			mov r1, r8 \n\
103			add r2, r0, r2 \n\
104			and r1, r2 \n\
105			lsr r2, r2, #15 \n\
106			strh r1, [r5, #4] \n\
107			\n\
108			ldrh r0, [r6, #8] \n\
109			ldrh r1, [r7, #8] \n\
110			mul r0, r3 \n\
111			mul r1, r4 \n\
112			add r2, r0, r2 \n\
113			ldrh r0, [r5, #8] \n\
114			add r2, r1, r2 \n\
115			mov r1, r8 \n\
116			add r2, r0, r2 \n\
117			and r1, r2 \n\
118			lsr r2, r2, #15 \n\
119			strh r1, [r5, #6] \n\
120			\n\
121			add r5, r5, #8 \n\
122			add r6, r6, #8 \n\
123			add r7, r7, #8 \n\
124			cmp r5, r9 \n\
125			bne loop%= \n\
126			\n\
127			str r2, %[carry] \n\
128			"
129			: [carry] "=m" (r)
130			: [xu] "m" (xu), [f] "m" (f), [d] "m" (d), [y] "m" (y),
131			[m] "m" (m), [limit] "m" (limit)
132			: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9" );
133			} else {
134			r = 0;
135			}
136			v = len4;
137			#else
138	0		r = 0;
139	0	0	for (v = 0; v < len4; v += 4) {
140			uint32_t z;
141
142	0		z = d[v + 1] + MUL15(xu, y[v + 1])
143	0		+ MUL15(f, m[v + 1]) + r;
144	0		r = z >> 15;
145	0		d[v + 0] = z & 0x7FFF;
146	0		z = d[v + 2] + MUL15(xu, y[v + 2])
147	0		+ MUL15(f, m[v + 2]) + r;
148	0		r = z >> 15;
149	0		d[v + 1] = z & 0x7FFF;
150	0		z = d[v + 3] + MUL15(xu, y[v + 3])
151	0		+ MUL15(f, m[v + 3]) + r;
152	0		r = z >> 15;
153	0		d[v + 2] = z & 0x7FFF;
154	0		z = d[v + 4] + MUL15(xu, y[v + 4])
155	0		+ MUL15(f, m[v + 4]) + r;
156	0		r = z >> 15;
157	0		d[v + 3] = z & 0x7FFF;
158			}
159			#endif
160	0	0	for (; v < len; v ++) {
161			uint32_t z;
162
163	0		z = d[v + 1] + MUL15(xu, y[v + 1])
164	0		+ MUL15(f, m[v + 1]) + r;
165	0		r = z >> 15;
166	0		d[v + 0] = z & 0x7FFF;
167			}
168
169	0		zh = dh + r;
170	0		d[len] = zh & 0x7FFF;
171	0		dh = zh >> 15;
172			}
173
174			/*
175			* Restore the bit length (it was overwritten in the loop above).
176			*/
177	0		d[0] = m[0];
178
179			/*
180			* d[] may be greater than m[], but it is still lower than twice
181			* the modulus.
182			*/
183	0		br_i15_sub(d, m, NEQ(dh, 0) \| NOT(br_i15_sub(d, m, 0)));
184	0		}