1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_cfft_radix2_q15.c
4 * Description: Radix-2 Decimation in Frequency CFFT & CIFFT Fixed point processing function
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/transform_functions.h"
30
31 void arm_radix2_butterfly_q15(
32 q15_t * pSrc,
33 uint32_t fftLen,
34 const q15_t * pCoef,
35 uint16_t twidCoefModifier);
36
37 void arm_radix2_butterfly_inverse_q15(
38 q15_t * pSrc,
39 uint32_t fftLen,
40 const q15_t * pCoef,
41 uint16_t twidCoefModifier);
42
43 void arm_bitreversal_q15(
44 q15_t * pSrc,
45 uint32_t fftLen,
46 uint16_t bitRevFactor,
47 const uint16_t * pBitRevTab);
48
49
50 /**
51 @addtogroup ComplexFFTDeprecated
52 @{
53 */
54
55 /**
56 @brief Processing function for the fixed-point CFFT/CIFFT.
57 @deprecated Do not use this function. It has been superseded by \ref arm_cfft_q15 and will be removed in the future.
58 @param[in] S points to an instance of the fixed-point CFFT/CIFFT structure
59 @param[in,out] pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place
60 */
61
arm_cfft_radix2_q15(const arm_cfft_radix2_instance_q15 * S,q15_t * pSrc)62 void arm_cfft_radix2_q15(
63 const arm_cfft_radix2_instance_q15 * S,
64 q15_t * pSrc)
65 {
66
67 if (S->ifftFlag == 1U)
68 {
69 arm_radix2_butterfly_inverse_q15 (pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier);
70 }
71 else
72 {
73 arm_radix2_butterfly_q15 (pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier);
74 }
75
76 arm_bitreversal_q15(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
77 }
78
79 /**
80 @} end of ComplexFFTDeprecated group
81 */
82
arm_radix2_butterfly_q15(q15_t * pSrc,uint32_t fftLen,const q15_t * pCoef,uint16_t twidCoefModifier)83 void arm_radix2_butterfly_q15(
84 q15_t * pSrc,
85 uint32_t fftLen,
86 const q15_t * pCoef,
87 uint16_t twidCoefModifier)
88 {
89 #if defined (ARM_MATH_DSP)
90
91 uint32_t i, j, k, l;
92 uint32_t n1, n2, ia;
93 q15_t in;
94 q31_t T, S, R;
95 q31_t coeff, out1, out2;
96
97 //N = fftLen;
98 n2 = fftLen;
99
100 n1 = n2;
101 n2 = n2 >> 1;
102 ia = 0;
103
104 // loop for groups
105 for (i = 0; i < n2; i++)
106 {
107 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
108
109 ia = ia + twidCoefModifier;
110
111 l = i + n2;
112
113 T = read_q15x2 (pSrc + (2 * i));
114 in = ((int16_t) (T & 0xFFFF)) >> 1;
115 T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
116
117 S = read_q15x2 (pSrc + (2 * l));
118 in = ((int16_t) (S & 0xFFFF)) >> 1;
119 S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
120
121 R = __QSUB16(T, S);
122
123 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
124
125 #ifndef ARM_MATH_BIG_ENDIAN
126 out1 = __SMUAD(coeff, R) >> 16;
127 out2 = __SMUSDX(coeff, R);
128 #else
129 out1 = __SMUSDX(R, coeff) >> 16U;
130 out2 = __SMUAD(coeff, R);
131 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
132
133 write_q15x2 (pSrc + (2U * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
134
135 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
136
137 ia = ia + twidCoefModifier;
138
139 /* loop for butterfly */
140 i++;
141 l++;
142
143 T = read_q15x2 (pSrc + (2 * i));
144 in = ((int16_t) (T & 0xFFFF)) >> 1;
145 T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
146
147 S = read_q15x2 (pSrc + (2 * l));
148 in = ((int16_t) (S & 0xFFFF)) >> 1;
149 S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
150
151 R = __QSUB16(T, S);
152
153 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
154
155 #ifndef ARM_MATH_BIG_ENDIAN
156 out1 = __SMUAD(coeff, R) >> 16;
157 out2 = __SMUSDX(coeff, R);
158 #else
159
160 out1 = __SMUSDX(R, coeff) >> 16U;
161 out2 = __SMUAD(coeff, R);
162 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
163
164 write_q15x2 (pSrc + (2U * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
165
166 } /* groups loop end */
167
168 twidCoefModifier = twidCoefModifier << 1U;
169
170 /* loop for stage */
171 for (k = fftLen / 2; k > 2; k = k >> 1)
172 {
173 n1 = n2;
174 n2 = n2 >> 1;
175 ia = 0;
176
177 /* loop for groups */
178 for (j = 0; j < n2; j++)
179 {
180 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
181
182 ia = ia + twidCoefModifier;
183
184 /* loop for butterfly */
185 for (i = j; i < fftLen; i += n1)
186 {
187 l = i + n2;
188
189 T = read_q15x2 (pSrc + (2 * i));
190
191 S = read_q15x2 (pSrc + (2 * l));
192
193 R = __QSUB16(T, S);
194
195 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
196
197 #ifndef ARM_MATH_BIG_ENDIAN
198 out1 = __SMUAD(coeff, R) >> 16;
199 out2 = __SMUSDX(coeff, R);
200 #else
201 out1 = __SMUSDX(R, coeff) >> 16U;
202 out2 = __SMUAD(coeff, R);
203 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
204
205 write_q15x2 (pSrc + (2U * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
206
207 i += n1;
208
209 l = i + n2;
210
211 T = read_q15x2 (pSrc + (2 * i));
212
213 S = read_q15x2 (pSrc + (2 * l));
214
215 R = __QSUB16(T, S);
216
217 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
218
219 #ifndef ARM_MATH_BIG_ENDIAN
220 out1 = __SMUAD(coeff, R) >> 16;
221 out2 = __SMUSDX(coeff, R);
222 #else
223 out1 = __SMUSDX(R, coeff) >> 16U;
224 out2 = __SMUAD(coeff, R);
225 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
226
227 write_q15x2 (pSrc + (2U * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
228
229 } /* butterfly loop end */
230
231 } /* groups loop end */
232
233 twidCoefModifier = twidCoefModifier << 1U;
234 } /* stages loop end */
235
236 n1 = n2;
237 n2 = n2 >> 1;
238 ia = 0;
239
240 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
241
242 ia = ia + twidCoefModifier;
243
244 /* loop for butterfly */
245 for (i = 0; i < fftLen; i += n1)
246 {
247 l = i + n2;
248
249 T = read_q15x2 (pSrc + (2 * i));
250
251 S = read_q15x2 (pSrc + (2 * l));
252
253 R = __QSUB16(T, S);
254
255 write_q15x2 (pSrc + (2 * i), __QADD16(T, S));
256
257 write_q15x2 (pSrc + (2 * l), R);
258
259 i += n1;
260 l = i + n2;
261
262 T = read_q15x2 (pSrc + (2 * i));
263
264 S = read_q15x2 (pSrc + (2 * l));
265
266 R = __QSUB16(T, S);
267
268 write_q15x2 (pSrc + (2 * i), __QADD16(T, S));
269
270 write_q15x2 (pSrc + (2 * l), R);
271
272 } /* groups loop end */
273
274
275 #else /* #if defined (ARM_MATH_DSP) */
276
277 uint32_t i, j, k, l;
278 uint32_t n1, n2, ia;
279 q15_t xt, yt, cosVal, sinVal;
280
281
282 // N = fftLen;
283 n2 = fftLen;
284
285 n1 = n2;
286 n2 = n2 >> 1;
287 ia = 0;
288
289 /* loop for groups */
290 for (j = 0; j < n2; j++)
291 {
292 cosVal = pCoef[(ia * 2)];
293 sinVal = pCoef[(ia * 2) + 1];
294 ia = ia + twidCoefModifier;
295
296 /* loop for butterfly */
297 for (i = j; i < fftLen; i += n1)
298 {
299 l = i + n2;
300 xt = (pSrc[2 * i] >> 1U) - (pSrc[2 * l] >> 1U);
301 pSrc[2 * i] = ((pSrc[2 * i] >> 1U) + (pSrc[2 * l] >> 1U)) >> 1U;
302
303 yt = (pSrc[2 * i + 1] >> 1U) - (pSrc[2 * l + 1] >> 1U);
304 pSrc[2 * i + 1] = ((pSrc[2 * l + 1] >> 1U) +
305 (pSrc[2 * i + 1] >> 1U) ) >> 1U;
306
307 pSrc[2 * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
308 ((int16_t) (((q31_t) yt * sinVal) >> 16)));
309
310 pSrc[2U * l + 1] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
311 ((int16_t) (((q31_t) xt * sinVal) >> 16)));
312
313 } /* butterfly loop end */
314
315 } /* groups loop end */
316
317 twidCoefModifier = twidCoefModifier << 1U;
318
319 /* loop for stage */
320 for (k = fftLen / 2; k > 2; k = k >> 1)
321 {
322 n1 = n2;
323 n2 = n2 >> 1;
324 ia = 0;
325
326 /* loop for groups */
327 for (j = 0; j < n2; j++)
328 {
329 cosVal = pCoef[ia * 2];
330 sinVal = pCoef[(ia * 2) + 1];
331 ia = ia + twidCoefModifier;
332
333 /* loop for butterfly */
334 for (i = j; i < fftLen; i += n1)
335 {
336 l = i + n2;
337 xt = pSrc[2 * i] - pSrc[2 * l];
338 pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1U;
339
340 yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
341 pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1U;
342
343 pSrc[2 * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
344 ((int16_t) (((q31_t) yt * sinVal) >> 16)));
345
346 pSrc[2U * l + 1] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
347 ((int16_t) (((q31_t) xt * sinVal) >> 16)));
348
349 } /* butterfly loop end */
350
351 } /* groups loop end */
352
353 twidCoefModifier = twidCoefModifier << 1U;
354 } /* stages loop end */
355
356 n1 = n2;
357 n2 = n2 >> 1;
358 ia = 0;
359
360 /* loop for groups */
361 for (j = 0; j < n2; j++)
362 {
363 cosVal = pCoef[ia * 2];
364 sinVal = pCoef[(ia * 2) + 1];
365
366 ia = ia + twidCoefModifier;
367
368 /* loop for butterfly */
369 for (i = j; i < fftLen; i += n1)
370 {
371 l = i + n2;
372 xt = pSrc[2 * i] - pSrc[2 * l];
373 pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);
374
375 yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
376 pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);
377
378 pSrc[2 * l] = xt;
379
380 pSrc[2 * l + 1] = yt;
381
382 } /* butterfly loop end */
383
384 } /* groups loop end */
385
386 twidCoefModifier = twidCoefModifier << 1U;
387
388 #endif /* #if defined (ARM_MATH_DSP) */
389
390 }
391
392
arm_radix2_butterfly_inverse_q15(q15_t * pSrc,uint32_t fftLen,const q15_t * pCoef,uint16_t twidCoefModifier)393 void arm_radix2_butterfly_inverse_q15(
394 q15_t * pSrc,
395 uint32_t fftLen,
396 const q15_t * pCoef,
397 uint16_t twidCoefModifier)
398 {
399 #if defined (ARM_MATH_DSP)
400
401 uint32_t i, j, k, l;
402 uint32_t n1, n2, ia;
403 q15_t in;
404 q31_t T, S, R;
405 q31_t coeff, out1, out2;
406
407 // N = fftLen;
408 n2 = fftLen;
409
410 n1 = n2;
411 n2 = n2 >> 1;
412 ia = 0;
413
414 /* loop for groups */
415 for (i = 0; i < n2; i++)
416 {
417 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
418
419 ia = ia + twidCoefModifier;
420
421 l = i + n2;
422
423 T = read_q15x2 (pSrc + (2 * i));
424 in = ((int16_t) (T & 0xFFFF)) >> 1;
425 T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
426
427 S = read_q15x2 (pSrc + (2 * l));
428 in = ((int16_t) (S & 0xFFFF)) >> 1;
429 S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
430
431 R = __QSUB16(T, S);
432
433 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
434
435 #ifndef ARM_MATH_BIG_ENDIAN
436 out1 = __SMUSD(coeff, R) >> 16;
437 out2 = __SMUADX(coeff, R);
438 #else
439 out1 = __SMUADX(R, coeff) >> 16U;
440 out2 = __SMUSD(__QSUB(0, coeff), R);
441 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
442
443 write_q15x2 (pSrc + (2 * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
444
445 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
446
447 ia = ia + twidCoefModifier;
448
449 /* loop for butterfly */
450 i++;
451 l++;
452
453 T = read_q15x2 (pSrc + (2 * i));
454 in = ((int16_t) (T & 0xFFFF)) >> 1;
455 T = ((T >> 1) & 0xFFFF0000) | (in & 0xFFFF);
456
457 S = read_q15x2 (pSrc + (2 * l));
458 in = ((int16_t) (S & 0xFFFF)) >> 1;
459 S = ((S >> 1) & 0xFFFF0000) | (in & 0xFFFF);
460
461 R = __QSUB16(T, S);
462
463 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
464
465 #ifndef ARM_MATH_BIG_ENDIAN
466 out1 = __SMUSD(coeff, R) >> 16;
467 out2 = __SMUADX(coeff, R);
468 #else
469 out1 = __SMUADX(R, coeff) >> 16U;
470 out2 = __SMUSD(__QSUB(0, coeff), R);
471 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
472
473 write_q15x2 (pSrc + (2 * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
474
475 } /* groups loop end */
476
477 twidCoefModifier = twidCoefModifier << 1U;
478
479 /* loop for stage */
480 for (k = fftLen / 2; k > 2; k = k >> 1)
481 {
482 n1 = n2;
483 n2 = n2 >> 1;
484 ia = 0;
485
486 /* loop for groups */
487 for (j = 0; j < n2; j++)
488 {
489 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
490
491 ia = ia + twidCoefModifier;
492
493 /* loop for butterfly */
494 for (i = j; i < fftLen; i += n1)
495 {
496 l = i + n2;
497
498 T = read_q15x2 (pSrc + (2 * i));
499
500 S = read_q15x2 (pSrc + (2 * l));
501
502 R = __QSUB16(T, S);
503
504 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
505
506 #ifndef ARM_MATH_BIG_ENDIAN
507 out1 = __SMUSD(coeff, R) >> 16;
508 out2 = __SMUADX(coeff, R);
509 #else
510 out1 = __SMUADX(R, coeff) >> 16U;
511 out2 = __SMUSD(__QSUB(0, coeff), R);
512 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
513
514 write_q15x2 (pSrc + (2 * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
515
516 i += n1;
517
518 l = i + n2;
519
520 T = read_q15x2 (pSrc + (2 * i));
521
522 S = read_q15x2 (pSrc + (2 * l));
523
524 R = __QSUB16(T, S);
525
526 write_q15x2 (pSrc + (2 * i), __SHADD16(T, S));
527
528 #ifndef ARM_MATH_BIG_ENDIAN
529 out1 = __SMUSD(coeff, R) >> 16;
530 out2 = __SMUADX(coeff, R);
531 #else
532 out1 = __SMUADX(R, coeff) >> 16U;
533 out2 = __SMUSD(__QSUB(0, coeff), R);
534 #endif /* #ifndef ARM_MATH_BIG_ENDIAN */
535
536 write_q15x2 (pSrc + (2 * l), (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF));
537
538 } /* butterfly loop end */
539
540 } /* groups loop end */
541
542 twidCoefModifier = twidCoefModifier << 1U;
543 } /* stages loop end */
544
545 n1 = n2;
546 n2 = n2 >> 1;
547 ia = 0;
548
549 /* loop for groups */
550 for (j = 0; j < n2; j++)
551 {
552 coeff = read_q15x2 ((q15_t *)pCoef + (ia * 2U));
553
554 ia = ia + twidCoefModifier;
555
556 /* loop for butterfly */
557 for (i = j; i < fftLen; i += n1)
558 {
559 l = i + n2;
560
561 T = read_q15x2 (pSrc + (2 * i));
562
563 S = read_q15x2 (pSrc + (2 * l));
564
565 R = __QSUB16(T, S);
566
567 write_q15x2 (pSrc + (2 * i), __QADD16(T, S));
568
569 write_q15x2 (pSrc + (2 * l), R);
570
571 } /* butterfly loop end */
572
573 } /* groups loop end */
574
575 twidCoefModifier = twidCoefModifier << 1U;
576
577 #else /* #if defined (ARM_MATH_DSP) */
578
579 uint32_t i, j, k, l;
580 uint32_t n1, n2, ia;
581 q15_t xt, yt, cosVal, sinVal;
582
583 // N = fftLen;
584 n2 = fftLen;
585
586 n1 = n2;
587 n2 = n2 >> 1;
588 ia = 0;
589
590 /* loop for groups */
591 for (j = 0; j < n2; j++)
592 {
593 cosVal = pCoef[(ia * 2)];
594 sinVal = pCoef[(ia * 2) + 1];
595 ia = ia + twidCoefModifier;
596
597 /* loop for butterfly */
598 for (i = j; i < fftLen; i += n1)
599 {
600 l = i + n2;
601 xt = (pSrc[2 * i] >> 1U) - (pSrc[2 * l] >> 1U);
602 pSrc[2 * i] = ((pSrc[2 * i] >> 1U) + (pSrc[2 * l] >> 1U)) >> 1U;
603
604 yt = (pSrc[2 * i + 1] >> 1U) - (pSrc[2 * l + 1] >> 1U);
605 pSrc[2 * i + 1] = ((pSrc[2 * l + 1] >> 1U) +
606 (pSrc[2 * i + 1] >> 1U) ) >> 1U;
607
608 pSrc[2 * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
609 ((int16_t) (((q31_t) yt * sinVal) >> 16)));
610
611 pSrc[2 * l + 1] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
612 ((int16_t) (((q31_t) xt * sinVal) >> 16)));
613
614 } /* butterfly loop end */
615
616 } /* groups loop end */
617
618 twidCoefModifier = twidCoefModifier << 1U;
619
620 /* loop for stage */
621 for (k = fftLen / 2; k > 2; k = k >> 1)
622 {
623 n1 = n2;
624 n2 = n2 >> 1;
625 ia = 0;
626
627 /* loop for groups */
628 for (j = 0; j < n2; j++)
629 {
630 cosVal = pCoef[(ia * 2)];
631 sinVal = pCoef[(ia * 2) + 1];
632 ia = ia + twidCoefModifier;
633
634 /* loop for butterfly */
635 for (i = j; i < fftLen; i += n1)
636 {
637 l = i + n2;
638 xt = pSrc[2 * i] - pSrc[2 * l];
639 pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1U;
640
641 yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
642 pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1U;
643
644 pSrc[2 * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
645 ((int16_t) (((q31_t) yt * sinVal) >> 16)) );
646
647 pSrc[2 * l + 1] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
648 ((int16_t) (((q31_t) xt * sinVal) >> 16)) );
649
650 } /* butterfly loop end */
651
652 } /* groups loop end */
653
654 twidCoefModifier = twidCoefModifier << 1U;
655 } /* stages loop end */
656
657 n1 = n2;
658 n2 = n2 >> 1;
659 ia = 0;
660
661 cosVal = pCoef[(ia * 2)];
662 sinVal = pCoef[(ia * 2) + 1];
663
664 ia = ia + twidCoefModifier;
665
666 /* loop for butterfly */
667 for (i = 0; i < fftLen; i += n1)
668 {
669 l = i + n2;
670 xt = pSrc[2 * i] - pSrc[2 * l];
671 pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);
672
673 yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
674 pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);
675
676 pSrc[2 * l] = xt;
677
678 pSrc[2 * l + 1] = yt;
679
680 } /* groups loop end */
681
682
683 #endif /* #if defined (ARM_MATH_DSP) */
684
685 }
686
