Merge branch 'jc/maint-rev-list-culled-boundary'
[git/git.git] / ppc / sha1ppc.S
1 /*
2 * SHA-1 implementation for PowerPC.
3 *
4 * Copyright (C) 2005 Paul Mackerras <paulus@samba.org>
5 */
6
7 /*
8 * PowerPC calling convention:
9 * %r0 - volatile temp
10 * %r1 - stack pointer.
11 * %r2 - reserved
12 * %r3-%r12 - Incoming arguments & return values; volatile.
13 * %r13-%r31 - Callee-save registers
14 * %lr - Return address, volatile
15 * %ctr - volatile
16 *
17 * Register usage in this routine:
18 * %r0 - temp
19 * %r3 - argument (pointer to 5 words of SHA state)
20 * %r4 - argument (pointer to data to hash)
21 * %r5 - Constant K in SHA round (initially number of blocks to hash)
22 * %r6-%r10 - Working copies of SHA variables A..E (actually E..A order)
23 * %r11-%r26 - Data being hashed W[].
24 * %r27-%r31 - Previous copies of A..E, for final add back.
25 * %ctr - loop count
26 */
27
28
29 /*
30 * We roll the registers for A, B, C, D, E around on each
31 * iteration; E on iteration t is D on iteration t+1, and so on.
32 * We use registers 6 - 10 for this. (Registers 27 - 31 hold
33 * the previous values.)
34 */
35 #define RA(t) (((t)+4)%5+6)
36 #define RB(t) (((t)+3)%5+6)
37 #define RC(t) (((t)+2)%5+6)
38 #define RD(t) (((t)+1)%5+6)
39 #define RE(t) (((t)+0)%5+6)
40
41 /* We use registers 11 - 26 for the W values */
42 #define W(t) ((t)%16+11)
43
44 /* Register 5 is used for the constant k */
45
46 /*
47 * The basic SHA-1 round function is:
48 * E += ROTL(A,5) + F(B,C,D) + W[i] + K; B = ROTL(B,30)
49 * Then the variables are renamed: (A,B,C,D,E) = (E,A,B,C,D).
50 *
51 * Every 20 rounds, the function F() and the constant K changes:
52 * - 20 rounds of f0(b,c,d) = "bit wise b ? c : d" = (^b & d) + (b & c)
53 * - 20 rounds of f1(b,c,d) = b^c^d = (b^d)^c
54 * - 20 rounds of f2(b,c,d) = majority(b,c,d) = (b&d) + ((b^d)&c)
55 * - 20 more rounds of f1(b,c,d)
56 *
57 * These are all scheduled for near-optimal performance on a G4.
58 * The G4 is a 3-issue out-of-order machine with 3 ALUs, but it can only
59 * *consider* starting the oldest 3 instructions per cycle. So to get
60 * maximum performance out of it, you have to treat it as an in-order
61 * machine. Which means interleaving the computation round t with the
62 * computation of W[t+4].
63 *
64 * The first 16 rounds use W values loaded directly from memory, while the
65 * remaining 64 use values computed from those first 16. We preload
66 * 4 values before starting, so there are three kinds of rounds:
67 * - The first 12 (all f0) also load the W values from memory.
68 * - The next 64 compute W(i+4) in parallel. 8*f0, 20*f1, 20*f2, 16*f1.
69 * - The last 4 (all f1) do not do anything with W.
70 *
71 * Therefore, we have 6 different round functions:
72 * STEPD0_LOAD(t,s) - Perform round t and load W(s). s < 16
73 * STEPD0_UPDATE(t,s) - Perform round t and compute W(s). s >= 16.
74 * STEPD1_UPDATE(t,s)
75 * STEPD2_UPDATE(t,s)
76 * STEPD1(t) - Perform round t with no load or update.
77 *
78 * The G5 is more fully out-of-order, and can find the parallelism
79 * by itself. The big limit is that it has a 2-cycle ALU latency, so
80 * even though it's 2-way, the code has to be scheduled as if it's
81 * 4-way, which can be a limit. To help it, we try to schedule the
82 * read of RA(t) as late as possible so it doesn't stall waiting for
83 * the previous round's RE(t-1), and we try to rotate RB(t) as early
84 * as possible while reading RC(t) (= RB(t-1)) as late as possible.
85 */
86
87 /* the initial loads. */
88 #define LOADW(s) \
89 lwz W(s),(s)*4(%r4)
90
91 /*
92 * Perform a step with F0, and load W(s). Uses W(s) as a temporary
93 * before loading it.
94 * This is actually 10 instructions, which is an awkward fit.
95 * It can execute grouped as listed, or delayed one instruction.
96 * (If delayed two instructions, there is a stall before the start of the
97 * second line.) Thus, two iterations take 7 cycles, 3.5 cycles per round.
98 */
99 #define STEPD0_LOAD(t,s) \
100 add RE(t),RE(t),W(t); andc %r0,RD(t),RB(t); and W(s),RC(t),RB(t); \
101 add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; rotlwi RB(t),RB(t),30; \
102 add RE(t),RE(t),W(s); add %r0,%r0,%r5; lwz W(s),(s)*4(%r4); \
103 add RE(t),RE(t),%r0
104
105 /*
106 * This is likewise awkward, 13 instructions. However, it can also
107 * execute starting with 2 out of 3 possible moduli, so it does 2 rounds
108 * in 9 cycles, 4.5 cycles/round.
109 */
110 #define STEPD0_UPDATE(t,s,loadk...) \
111 add RE(t),RE(t),W(t); andc %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \
112 add RE(t),RE(t),%r0; and %r0,RC(t),RB(t); xor W(s),W(s),W((s)-8); \
113 add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; xor W(s),W(s),W((s)-14); \
114 add RE(t),RE(t),%r5; loadk; rotlwi RB(t),RB(t),30; rotlwi W(s),W(s),1; \
115 add RE(t),RE(t),%r0
116
117 /* Nicely optimal. Conveniently, also the most common. */
118 #define STEPD1_UPDATE(t,s,loadk...) \
119 add RE(t),RE(t),W(t); xor %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \
120 add RE(t),RE(t),%r5; loadk; xor %r0,%r0,RC(t); xor W(s),W(s),W((s)-8); \
121 add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; xor W(s),W(s),W((s)-14); \
122 add RE(t),RE(t),%r0; rotlwi RB(t),RB(t),30; rotlwi W(s),W(s),1
123
124 /*
125 * The naked version, no UPDATE, for the last 4 rounds. 3 cycles per.
126 * We could use W(s) as a temp register, but we don't need it.
127 */
128 #define STEPD1(t) \
129 add RE(t),RE(t),W(t); xor %r0,RD(t),RB(t); \
130 rotlwi RB(t),RB(t),30; add RE(t),RE(t),%r5; xor %r0,%r0,RC(t); \
131 add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; /* spare slot */ \
132 add RE(t),RE(t),%r0
133
134 /*
135 * 14 instructions, 5 cycles per. The majority function is a bit
136 * awkward to compute. This can execute with a 1-instruction delay,
137 * but it causes a 2-instruction delay, which triggers a stall.
138 */
139 #define STEPD2_UPDATE(t,s,loadk...) \
140 add RE(t),RE(t),W(t); and %r0,RD(t),RB(t); xor W(s),W((s)-16),W((s)-3); \
141 add RE(t),RE(t),%r0; xor %r0,RD(t),RB(t); xor W(s),W(s),W((s)-8); \
142 add RE(t),RE(t),%r5; loadk; and %r0,%r0,RC(t); xor W(s),W(s),W((s)-14); \
143 add RE(t),RE(t),%r0; rotlwi %r0,RA(t),5; rotlwi W(s),W(s),1; \
144 add RE(t),RE(t),%r0; rotlwi RB(t),RB(t),30
145
146 #define STEP0_LOAD4(t,s) \
147 STEPD0_LOAD(t,s); \
148 STEPD0_LOAD((t+1),(s)+1); \
149 STEPD0_LOAD((t)+2,(s)+2); \
150 STEPD0_LOAD((t)+3,(s)+3)
151
152 #define STEPUP4(fn, t, s, loadk...) \
153 STEP##fn##_UPDATE(t,s,); \
154 STEP##fn##_UPDATE((t)+1,(s)+1,); \
155 STEP##fn##_UPDATE((t)+2,(s)+2,); \
156 STEP##fn##_UPDATE((t)+3,(s)+3,loadk)
157
158 #define STEPUP20(fn, t, s, loadk...) \
159 STEPUP4(fn, t, s,); \
160 STEPUP4(fn, (t)+4, (s)+4,); \
161 STEPUP4(fn, (t)+8, (s)+8,); \
162 STEPUP4(fn, (t)+12, (s)+12,); \
163 STEPUP4(fn, (t)+16, (s)+16, loadk)
164
165 .globl ppc_sha1_core
166 ppc_sha1_core:
167 stwu %r1,-80(%r1)
168 stmw %r13,4(%r1)
169
170 /* Load up A - E */
171 lmw %r27,0(%r3)
172
173 mtctr %r5
174
175 1:
176 LOADW(0)
177 lis %r5,0x5a82
178 mr RE(0),%r31
179 LOADW(1)
180 mr RD(0),%r30
181 mr RC(0),%r29
182 LOADW(2)
183 ori %r5,%r5,0x7999 /* K0-19 */
184 mr RB(0),%r28
185 LOADW(3)
186 mr RA(0),%r27
187
188 STEP0_LOAD4(0, 4)
189 STEP0_LOAD4(4, 8)
190 STEP0_LOAD4(8, 12)
191 STEPUP4(D0, 12, 16,)
192 STEPUP4(D0, 16, 20, lis %r5,0x6ed9)
193
194 ori %r5,%r5,0xeba1 /* K20-39 */
195 STEPUP20(D1, 20, 24, lis %r5,0x8f1b)
196
197 ori %r5,%r5,0xbcdc /* K40-59 */
198 STEPUP20(D2, 40, 44, lis %r5,0xca62)
199
200 ori %r5,%r5,0xc1d6 /* K60-79 */
201 STEPUP4(D1, 60, 64,)
202 STEPUP4(D1, 64, 68,)
203 STEPUP4(D1, 68, 72,)
204 STEPUP4(D1, 72, 76,)
205 addi %r4,%r4,64
206 STEPD1(76)
207 STEPD1(77)
208 STEPD1(78)
209 STEPD1(79)
210
211 /* Add results to original values */
212 add %r31,%r31,RE(0)
213 add %r30,%r30,RD(0)
214 add %r29,%r29,RC(0)
215 add %r28,%r28,RB(0)
216 add %r27,%r27,RA(0)
217
218 bdnz 1b
219
220 /* Save final hash, restore registers, and return */
221 stmw %r27,0(%r3)
222 lmw %r13,4(%r1)
223 addi %r1,%r1,80
224 blr