1 // Copyright 2018 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 //go:build gc && !purego
6 // +build gc,!purego
7
8 #include "textflag.h"
9
10 // This implementation of Poly1305 uses the vector facility (vx)
11 // to process up to 2 blocks (32 bytes) per iteration using an
12 // algorithm based on the one described in:
13 //
14 // NEON crypto, Daniel J. Bernstein & Peter Schwabe
15 // https://cryptojedi.org/papers/neoncrypto-20120320.pdf
16 //
17 // This algorithm uses 5 26-bit limbs to represent a 130-bit
18 // value. These limbs are, for the most part, zero extended and
19 // placed into 64-bit vector register elements. Each vector
20 // register is 128-bits wide and so holds 2 of these elements.
21 // Using 26-bit limbs allows us plenty of headroom to accommodate
22 // accumulations before and after multiplication without
23 // overflowing either 32-bits (before multiplication) or 64-bits
24 // (after multiplication).
25 //
26 // In order to parallelise the operations required to calculate
27 // the sum we use two separate accumulators and then sum those
28 // in an extra final step. For compatibility with the generic
29 // implementation we perform this summation at the end of every
30 // updateVX call.
31 //
32 // To use two accumulators we must multiply the message blocks
33 // by r² rather than r. Only the final message block should be
34 // multiplied by r.
35 //
36 // Example:
37 //
38 // We want to calculate the sum (h) for a 64 byte message (m):
39 //
40 // h = m[0:16]r⁴ + m[16:32]r³ + m[32:48]r² + m[48:64]r
41 //
42 // To do this we split the calculation into the even indices
43 // and odd indices of the message. These form our SIMD 'lanes':
44 //
45 // h = m[ 0:16]r⁴ + m[32:48]r² + <- lane 0
46 // m[16:32]r³ + m[48:64]r <- lane 1
47 //
48 // To calculate this iteratively we refactor so that both lanes
49 // are written in terms of r² and r:
50 //
51 // h = (m[ 0:16]r² + m[32:48])r² + <- lane 0
52 // (m[16:32]r² + m[48:64])r <- lane 1
53 // ^ ^
54 // | coefficients for second iteration
55 // coefficients for first iteration
56 //
57 // So in this case we would have two iterations. In the first
58 // both lanes are multiplied by r². In the second only the
59 // first lane is multiplied by r² and the second lane is
60 // instead multiplied by r. This gives use the odd and even
61 // powers of r that we need from the original equation.
62 //
63 // Notation:
64 //
65 // h - accumulator
66 // r - key
67 // m - message
68 //
69 // [a, b] - SIMD register holding two 64-bit values
70 // [a, b, c, d] - SIMD register holding four 32-bit values
71 // xᵢ[n] - limb n of variable x with bit width i
72 //
73 // Limbs are expressed in little endian order, so for 26-bit
74 // limbs x₂₆[4] will be the most significant limb and x₂₆[0]
75 // will be the least significant limb.
76
77 // masking constants
78 #define MOD24 V0 // [0x0000000000ffffff, 0x0000000000ffffff] - mask low 24-bits
79 #define MOD26 V1 // [0x0000000003ffffff, 0x0000000003ffffff] - mask low 26-bits
80
81 // expansion constants (see EXPAND macro)
82 #define EX0 V2
83 #define EX1 V3
84 #define EX2 V4
85
86 // key (r², r or 1 depending on context)
87 #define R_0 V5
88 #define R_1 V6
89 #define R_2 V7
90 #define R_3 V8
91 #define R_4 V9
92
93 // precalculated coefficients (5r², 5r or 0 depending on context)
94 #define R5_1 V10
95 #define R5_2 V11
96 #define R5_3 V12
97 #define R5_4 V13
98
99 // message block (m)
100 #define M_0 V14
101 #define M_1 V15
102 #define M_2 V16
103 #define M_3 V17
104 #define M_4 V18
105
106 // accumulator (h)
107 #define H_0 V19
108 #define H_1 V20
109 #define H_2 V21
110 #define H_3 V22
111 #define H_4 V23
112
113 // temporary registers (for short-lived values)
114 #define T_0 V24
115 #define T_1 V25
116 #define T_2 V26
117 #define T_3 V27
118 #define T_4 V28
119
120 GLOBL ·constants<>(SB), RODATA, $0x30
121 // EX0
122 DATA ·constants<>+0x00(SB)/8, $0x0006050403020100
123 DATA ·constants<>+0x08(SB)/8, $0x1016151413121110
124 // EX1
125 DATA ·constants<>+0x10(SB)/8, $0x060c0b0a09080706
126 DATA ·constants<>+0x18(SB)/8, $0x161c1b1a19181716
127 // EX2
128 DATA ·constants<>+0x20(SB)/8, $0x0d0d0d0d0d0f0e0d
129 DATA ·constants<>+0x28(SB)/8, $0x1d1d1d1d1d1f1e1d
130
131 // MULTIPLY multiplies each lane of f and g, partially reduced
132 // modulo 2¹³⁰ - 5. The result, h, consists of partial products
133 // in each lane that need to be reduced further to produce the
134 // final result.
135 //
136 // h₁₃₀ = (f₁₃₀g₁₃₀) % 2¹³⁰ + (5f₁₃₀g₁₃₀) / 2¹³⁰
137 //
138 // Note that the multiplication by 5 of the high bits is
139 // achieved by precalculating the multiplication of four of the
140 // g coefficients by 5. These are g51-g54.
141 #define MULTIPLY(f0, f1, f2, f3, f4, g0, g1, g2, g3, g4, g51, g52, g53, g54, h0, h1, h2, h3, h4) \
142 VMLOF f0, g0, h0 \
143 VMLOF f0, g3, h3 \
144 VMLOF f0, g1, h1 \
145 VMLOF f0, g4, h4 \
146 VMLOF f0, g2, h2 \
147 VMLOF f1, g54, T_0 \
148 VMLOF f1, g2, T_3 \
149 VMLOF f1, g0, T_1 \
150 VMLOF f1, g3, T_4 \
151 VMLOF f1, g1, T_2 \
152 VMALOF f2, g53, h0, h0 \
153 VMALOF f2, g1, h3, h3 \
154 VMALOF f2, g54, h1, h1 \
155 VMALOF f2, g2, h4, h4 \
156 VMALOF f2, g0, h2, h2 \
157 VMALOF f3, g52, T_0, T_0 \
158 VMALOF f3, g0, T_3, T_3 \
159 VMALOF f3, g53, T_1, T_1 \
160 VMALOF f3, g1, T_4, T_4 \
161 VMALOF f3, g54, T_2, T_2 \
162 VMALOF f4, g51, h0, h0 \
163 VMALOF f4, g54, h3, h3 \
164 VMALOF f4, g52, h1, h1 \
165 VMALOF f4, g0, h4, h4 \
166 VMALOF f4, g53, h2, h2 \
167 VAG T_0, h0, h0 \
168 VAG T_3, h3, h3 \
169 VAG T_1, h1, h1 \
170 VAG T_4, h4, h4 \
171 VAG T_2, h2, h2
172
173 // REDUCE performs the following carry operations in four
174 // stages, as specified in Bernstein & Schwabe:
175 //
176 // 1: h₂₆[0]->h₂₆[1] h₂₆[3]->h₂₆[4]
177 // 2: h₂₆[1]->h₂₆[2] h₂₆[4]->h₂₆[0]
178 // 3: h₂₆[0]->h₂₆[1] h₂₆[2]->h₂₆[3]
179 // 4: h₂₆[3]->h₂₆[4]
180 //
181 // The result is that all of the limbs are limited to 26-bits
182 // except for h₂₆[1] and h₂₆[4] which are limited to 27-bits.
183 //
184 // Note that although each limb is aligned at 26-bit intervals
185 // they may contain values that exceed 2²⁶ - 1, hence the need
186 // to carry the excess bits in each limb.
187 #define REDUCE(h0, h1, h2, h3, h4) \
188 VESRLG $26, h0, T_0 \
189 VESRLG $26, h3, T_1 \
190 VN MOD26, h0, h0 \
191 VN MOD26, h3, h3 \
192 VAG T_0, h1, h1 \
193 VAG T_1, h4, h4 \
194 VESRLG $26, h1, T_2 \
195 VESRLG $26, h4, T_3 \
196 VN MOD26, h1, h1 \
197 VN MOD26, h4, h4 \
198 VESLG $2, T_3, T_4 \
199 VAG T_3, T_4, T_4 \
200 VAG T_2, h2, h2 \
201 VAG T_4, h0, h0 \
202 VESRLG $26, h2, T_0 \
203 VESRLG $26, h0, T_1 \
204 VN MOD26, h2, h2 \
205 VN MOD26, h0, h0 \
206 VAG T_0, h3, h3 \
207 VAG T_1, h1, h1 \
208 VESRLG $26, h3, T_2 \
209 VN MOD26, h3, h3 \
210 VAG T_2, h4, h4
211
212 // EXPAND splits the 128-bit little-endian values in0 and in1
213 // into 26-bit big-endian limbs and places the results into
214 // the first and second lane of d₂₆[0:4] respectively.
215 //
216 // The EX0, EX1 and EX2 constants are arrays of byte indices
217 // for permutation. The permutation both reverses the bytes
218 // in the input and ensures the bytes are copied into the
219 // destination limb ready to be shifted into their final
220 // position.
221 #define EXPAND(in0, in1, d0, d1, d2, d3, d4) \
222 VPERM in0, in1, EX0, d0 \
223 VPERM in0, in1, EX1, d2 \
224 VPERM in0, in1, EX2, d4 \
225 VESRLG $26, d0, d1 \
226 VESRLG $30, d2, d3 \
227 VESRLG $4, d2, d2 \
228 VN MOD26, d0, d0 \ // [in0₂₆[0], in1₂₆[0]]
229 VN MOD26, d3, d3 \ // [in0₂₆[3], in1₂₆[3]]
230 VN MOD26, d1, d1 \ // [in0₂₆[1], in1₂₆[1]]
231 VN MOD24, d4, d4 \ // [in0₂₆[4], in1₂₆[4]]
232 VN MOD26, d2, d2 // [in0₂₆[2], in1₂₆[2]]
233
234 // func updateVX(state *macState, msg []byte)
235 TEXT ·updateVX(SB), NOSPLIT, $0
236 MOVD state+0(FP), R1
237 LMG msg+8(FP), R2, R3 // R2=msg_base, R3=msg_len
238
239 // load EX0, EX1 and EX2
240 MOVD $·constants<>(SB), R5
241 VLM (R5), EX0, EX2
242
243 // generate masks
244 VGMG $(64-24), $63, MOD24 // [0x00ffffff, 0x00ffffff]
245 VGMG $(64-26), $63, MOD26 // [0x03ffffff, 0x03ffffff]
246
247 // load h (accumulator) and r (key) from state
248 VZERO T_1 // [0, 0]
249 VL 0(R1), T_0 // [h₆₄[0], h₆₄[1]]
250 VLEG $0, 16(R1), T_1 // [h₆₄[2], 0]
251 VL 24(R1), T_2 // [r₆₄[0], r₆₄[1]]
252 VPDI $0, T_0, T_2, T_3 // [h₆₄[0], r₆₄[0]]
253 VPDI $5, T_0, T_2, T_4 // [h₆₄[1], r₆₄[1]]
254
255 // unpack h and r into 26-bit limbs
256 // note: h₆₄[2] may have the low 3 bits set, so h₂₆[4] is a 27-bit value
257 VN MOD26, T_3, H_0 // [h₂₆[0], r₂₆[0]]
258 VZERO H_1 // [0, 0]
259 VZERO H_3 // [0, 0]
260 VGMG $(64-12-14), $(63-12), T_0 // [0x03fff000, 0x03fff000] - 26-bit mask with low 12 bits masked out
261 VESLG $24, T_1, T_1 // [h₆₄[2]<<24, 0]
262 VERIMG $-26&63, T_3, MOD26, H_1 // [h₂₆[1], r₂₆[1]]
263 VESRLG $+52&63, T_3, H_2 // [h₂₆[2], r₂₆[2]] - low 12 bits only
264 VERIMG $-14&63, T_4, MOD26, H_3 // [h₂₆[1], r₂₆[1]]
265 VESRLG $40, T_4, H_4 // [h₂₆[4], r₂₆[4]] - low 24 bits only
266 VERIMG $+12&63, T_4, T_0, H_2 // [h₂₆[2], r₂₆[2]] - complete
267 VO T_1, H_4, H_4 // [h₂₆[4], r₂₆[4]] - complete
268
269 // replicate r across all 4 vector elements
270 VREPF $3, H_0, R_0 // [r₂₆[0], r₂₆[0], r₂₆[0], r₂₆[0]]
271 VREPF $3, H_1, R_1 // [r₂₆[1], r₂₆[1], r₂₆[1], r₂₆[1]]
272 VREPF $3, H_2, R_2 // [r₂₆[2], r₂₆[2], r₂₆[2], r₂₆[2]]
273 VREPF $3, H_3, R_3 // [r₂₆[3], r₂₆[3], r₂₆[3], r₂₆[3]]
274 VREPF $3, H_4, R_4 // [r₂₆[4], r₂₆[4], r₂₆[4], r₂₆[4]]
275
276 // zero out lane 1 of h
277 VLEIG $1, $0, H_0 // [h₂₆[0], 0]
278 VLEIG $1, $0, H_1 // [h₂₆[1], 0]
279 VLEIG $1, $0, H_2 // [h₂₆[2], 0]
280 VLEIG $1, $0, H_3 // [h₂₆[3], 0]
281 VLEIG $1, $0, H_4 // [h₂₆[4], 0]
282
283 // calculate 5r (ignore least significant limb)
284 VREPIF $5, T_0
285 VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r₂₆[1], 5r₂₆[1], 5r₂₆[1]]
286 VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r₂₆[2], 5r₂₆[2], 5r₂₆[2]]
287 VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r₂₆[3], 5r₂₆[3], 5r₂₆[3]]
288 VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r₂₆[4], 5r₂₆[4], 5r₂₆[4]]
289
290 // skip r² calculation if we are only calculating one block
291 CMPBLE R3, $16, skip
292
293 // calculate r²
294 MULTIPLY(R_0, R_1, R_2, R_3, R_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, M_0, M_1, M_2, M_3, M_4)
295 REDUCE(M_0, M_1, M_2, M_3, M_4)
296 VGBM $0x0f0f, T_0
297 VERIMG $0, M_0, T_0, R_0 // [r₂₆[0], r²₂₆[0], r₂₆[0], r²₂₆[0]]
298 VERIMG $0, M_1, T_0, R_1 // [r₂₆[1], r²₂₆[1], r₂₆[1], r²₂₆[1]]
299 VERIMG $0, M_2, T_0, R_2 // [r₂₆[2], r²₂₆[2], r₂₆[2], r²₂₆[2]]
300 VERIMG $0, M_3, T_0, R_3 // [r₂₆[3], r²₂₆[3], r₂₆[3], r²₂₆[3]]
301 VERIMG $0, M_4, T_0, R_4 // [r₂₆[4], r²₂₆[4], r₂₆[4], r²₂₆[4]]
302
303 // calculate 5r² (ignore least significant limb)
304 VREPIF $5, T_0
305 VMLF T_0, R_1, R5_1 // [5r₂₆[1], 5r²₂₆[1], 5r₂₆[1], 5r²₂₆[1]]
306 VMLF T_0, R_2, R5_2 // [5r₂₆[2], 5r²₂₆[2], 5r₂₆[2], 5r²₂₆[2]]
307 VMLF T_0, R_3, R5_3 // [5r₂₆[3], 5r²₂₆[3], 5r₂₆[3], 5r²₂₆[3]]
308 VMLF T_0, R_4, R5_4 // [5r₂₆[4], 5r²₂₆[4], 5r₂₆[4], 5r²₂₆[4]]
309
310 loop:
311 CMPBLE R3, $32, b2 // 2 or fewer blocks remaining, need to change key coefficients
312
313 // load next 2 blocks from message
314 VLM (R2), T_0, T_1
315
316 // update message slice
317 SUB $32, R3
318 MOVD $32(R2), R2
319
320 // unpack message blocks into 26-bit big-endian limbs
321 EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)
322
323 // add 2¹²⁸ to each message block value
324 VLEIB $4, $1, M_4
325 VLEIB $12, $1, M_4
326
327 multiply:
328 // accumulate the incoming message
329 VAG H_0, M_0, M_0
330 VAG H_3, M_3, M_3
331 VAG H_1, M_1, M_1
332 VAG H_4, M_4, M_4
333 VAG H_2, M_2, M_2
334
335 // multiply the accumulator by the key coefficient
336 MULTIPLY(M_0, M_1, M_2, M_3, M_4, R_0, R_1, R_2, R_3, R_4, R5_1, R5_2, R5_3, R5_4, H_0, H_1, H_2, H_3, H_4)
337
338 // carry and partially reduce the partial products
339 REDUCE(H_0, H_1, H_2, H_3, H_4)
340
341 CMPBNE R3, $0, loop
342
343 finish:
344 // sum lane 0 and lane 1 and put the result in lane 1
345 VZERO T_0
346 VSUMQG H_0, T_0, H_0
347 VSUMQG H_3, T_0, H_3
348 VSUMQG H_1, T_0, H_1
349 VSUMQG H_4, T_0, H_4
350 VSUMQG H_2, T_0, H_2
351
352 // reduce again after summation
353 // TODO(mundaym): there might be a more efficient way to do this
354 // now that we only have 1 active lane. For example, we could
355 // simultaneously pack the values as we reduce them.
356 REDUCE(H_0, H_1, H_2, H_3, H_4)
357
358 // carry h[1] through to h[4] so that only h[4] can exceed 2²⁶ - 1
359 // TODO(mundaym): in testing this final carry was unnecessary.
360 // Needs a proof before it can be removed though.
361 VESRLG $26, H_1, T_1
362 VN MOD26, H_1, H_1
363 VAQ T_1, H_2, H_2
364 VESRLG $26, H_2, T_2
365 VN MOD26, H_2, H_2
366 VAQ T_2, H_3, H_3
367 VESRLG $26, H_3, T_3
368 VN MOD26, H_3, H_3
369 VAQ T_3, H_4, H_4
370
371 // h is now < 2(2¹³⁰ - 5)
372 // Pack each lane in h₂₆[0:4] into h₁₂₈[0:1].
373 VESLG $26, H_1, H_1
374 VESLG $26, H_3, H_3
375 VO H_0, H_1, H_0
376 VO H_2, H_3, H_2
377 VESLG $4, H_2, H_2
378 VLEIB $7, $48, H_1
379 VSLB H_1, H_2, H_2
380 VO H_0, H_2, H_0
381 VLEIB $7, $104, H_1
382 VSLB H_1, H_4, H_3
383 VO H_3, H_0, H_0
384 VLEIB $7, $24, H_1
385 VSRLB H_1, H_4, H_1
386
387 // update state
388 VSTEG $1, H_0, 0(R1)
389 VSTEG $0, H_0, 8(R1)
390 VSTEG $1, H_1, 16(R1)
391 RET
392
393 b2: // 2 or fewer blocks remaining
394 CMPBLE R3, $16, b1
395
396 // Load the 2 remaining blocks (17-32 bytes remaining).
397 MOVD $-17(R3), R0 // index of final byte to load modulo 16
398 VL (R2), T_0 // load full 16 byte block
399 VLL R0, 16(R2), T_1 // load final (possibly partial) block and pad with zeros to 16 bytes
400
401 // The Poly1305 algorithm requires that a 1 bit be appended to
402 // each message block. If the final block is less than 16 bytes
403 // long then it is easiest to insert the 1 before the message
404 // block is split into 26-bit limbs. If, on the other hand, the
405 // final message block is 16 bytes long then we append the 1 bit
406 // after expansion as normal.
407 MOVBZ $1, R0
408 MOVD $-16(R3), R3 // index of byte in last block to insert 1 at (could be 16)
409 CMPBEQ R3, $16, 2(PC) // skip the insertion if the final block is 16 bytes long
410 VLVGB R3, R0, T_1 // insert 1 into the byte at index R3
411
412 // Split both blocks into 26-bit limbs in the appropriate lanes.
413 EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)
414
415 // Append a 1 byte to the end of the second to last block.
416 VLEIB $4, $1, M_4
417
418 // Append a 1 byte to the end of the last block only if it is a
419 // full 16 byte block.
420 CMPBNE R3, $16, 2(PC)
421 VLEIB $12, $1, M_4
422
423 // Finally, set up the coefficients for the final multiplication.
424 // We have previously saved r and 5r in the 32-bit even indexes
425 // of the R_[0-4] and R5_[1-4] coefficient registers.
426 //
427 // We want lane 0 to be multiplied by r² so that can be kept the
428 // same. We want lane 1 to be multiplied by r so we need to move
429 // the saved r value into the 32-bit odd index in lane 1 by
430 // rotating the 64-bit lane by 32.
431 VGBM $0x00ff, T_0 // [0, 0xffffffffffffffff] - mask lane 1 only
432 VERIMG $32, R_0, T_0, R_0 // [_, r²₂₆[0], _, r₂₆[0]]
433 VERIMG $32, R_1, T_0, R_1 // [_, r²₂₆[1], _, r₂₆[1]]
434 VERIMG $32, R_2, T_0, R_2 // [_, r²₂₆[2], _, r₂₆[2]]
435 VERIMG $32, R_3, T_0, R_3 // [_, r²₂₆[3], _, r₂₆[3]]
436 VERIMG $32, R_4, T_0, R_4 // [_, r²₂₆[4], _, r₂₆[4]]
437 VERIMG $32, R5_1, T_0, R5_1 // [_, 5r²₂₆[1], _, 5r₂₆[1]]
438 VERIMG $32, R5_2, T_0, R5_2 // [_, 5r²₂₆[2], _, 5r₂₆[2]]
439 VERIMG $32, R5_3, T_0, R5_3 // [_, 5r²₂₆[3], _, 5r₂₆[3]]
440 VERIMG $32, R5_4, T_0, R5_4 // [_, 5r²₂₆[4], _, 5r₂₆[4]]
441
442 MOVD $0, R3
443 BR multiply
444
445 skip:
446 CMPBEQ R3, $0, finish
447
448 b1: // 1 block remaining
449
450 // Load the final block (1-16 bytes). This will be placed into
451 // lane 0.
452 MOVD $-1(R3), R0
453 VLL R0, (R2), T_0 // pad to 16 bytes with zeros
454
455 // The Poly1305 algorithm requires that a 1 bit be appended to
456 // each message block. If the final block is less than 16 bytes
457 // long then it is easiest to insert the 1 before the message
458 // block is split into 26-bit limbs. If, on the other hand, the
459 // final message block is 16 bytes long then we append the 1 bit
460 // after expansion as normal.
461 MOVBZ $1, R0
462 CMPBEQ R3, $16, 2(PC)
463 VLVGB R3, R0, T_0
464
465 // Set the message block in lane 1 to the value 0 so that it
466 // can be accumulated without affecting the final result.
467 VZERO T_1
468
469 // Split the final message block into 26-bit limbs in lane 0.
470 // Lane 1 will be contain 0.
471 EXPAND(T_0, T_1, M_0, M_1, M_2, M_3, M_4)
472
473 // Append a 1 byte to the end of the last block only if it is a
474 // full 16 byte block.
475 CMPBNE R3, $16, 2(PC)
476 VLEIB $4, $1, M_4
477
478 // We have previously saved r and 5r in the 32-bit even indexes
479 // of the R_[0-4] and R5_[1-4] coefficient registers.
480 //
481 // We want lane 0 to be multiplied by r so we need to move the
482 // saved r value into the 32-bit odd index in lane 0. We want
483 // lane 1 to be set to the value 1. This makes multiplication
484 // a no-op. We do this by setting lane 1 in every register to 0
485 // and then just setting the 32-bit index 3 in R_0 to 1.
486 VZERO T_0
487 MOVD $0, R0
488 MOVD $0x10111213, R12
489 VLVGP R12, R0, T_1 // [_, 0x10111213, _, 0x00000000]
490 VPERM T_0, R_0, T_1, R_0 // [_, r₂₆[0], _, 0]
491 VPERM T_0, R_1, T_1, R_1 // [_, r₂₆[1], _, 0]
492 VPERM T_0, R_2, T_1, R_2 // [_, r₂₆[2], _, 0]
493 VPERM T_0, R_3, T_1, R_3 // [_, r₂₆[3], _, 0]
494 VPERM T_0, R_4, T_1, R_4 // [_, r₂₆[4], _, 0]
495 VPERM T_0, R5_1, T_1, R5_1 // [_, 5r₂₆[1], _, 0]
496 VPERM T_0, R5_2, T_1, R5_2 // [_, 5r₂₆[2], _, 0]
497 VPERM T_0, R5_3, T_1, R5_3 // [_, 5r₂₆[3], _, 0]
498 VPERM T_0, R5_4, T_1, R5_4 // [_, 5r₂₆[4], _, 0]
499
500 // Set the value of lane 1 to be 1.
501 VLEIF $3, $1, R_0 // [_, r₂₆[0], _, 1]
502
503 MOVD $0, R3
504 BR multiply
505
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