tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/TransformFunctions/arm_cfft_radix2_q15.c

   1 /* ----------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:            arm_cfft_radix2_q15.c
   9 *
  10 * Description:  Radix-2 Decimation in Frequency CFFT & CIFFT Fixed point processing function
  11 *
  12 *
  13 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  14 *
  15 * Redistribution and use in source and binary forms, with or without
  16 * modification, are permitted provided that the following conditions
  17 * are met:
  18 *   - Redistributions of source code must retain the above copyright
  19 *     notice, this list of conditions and the following disclaimer.
  20 *   - Redistributions in binary form must reproduce the above copyright
  21 *     notice, this list of conditions and the following disclaimer in
  22 *     the documentation and/or other materials provided with the
  23 *     distribution.
  24 *   - Neither the name of ARM LIMITED nor the names of its contributors
  25 *     may be used to endorse or promote products derived from this
  26 *     software without specific prior written permission.
  27 *
  28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  31 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  32 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  33 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  34 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  35 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  36 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  38 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  39 * POSSIBILITY OF SUCH DAMAGE.
  40 * -------------------------------------------------------------------- */
  41
  42 #include "arm_math.h"
  43
  44 void arm_radix2_butterfly_q15(
  45   q15_t * pSrc,
  46   uint32_t fftLen,
  47   q15_t * pCoef,
  48   uint16_t twidCoefModifier);
  49
  50 void arm_radix2_butterfly_inverse_q15(
  51   q15_t * pSrc,
  52   uint32_t fftLen,
  53   q15_t * pCoef,
  54   uint16_t twidCoefModifier);
  55
  56 void arm_bitreversal_q15(
  57   q15_t * pSrc,
  58   uint32_t fftLen,
  59   uint16_t bitRevFactor,
  60   uint16_t * pBitRevTab);
  61
  62 /**
  63  * @ingroup groupTransforms
  64  */
  65
  66 /**
  67  * @addtogroup ComplexFFT
  68  * @{
  69  */
  70
  71 /**
  72  * @details
  73  * @brief Processing function for the fixed-point CFFT/CIFFT.
  74  * @param[in]      *S    points to an instance of the fixed-point CFFT/CIFFT structure.
  75  * @param[in, out] *pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.
  76  * @return none.
  77  */
  78
  79 void arm_cfft_radix2_q15(
  80   const arm_cfft_radix2_instance_q15 * S,
  81   q15_t * pSrc)
  82 {
  83
  84   if(S->ifftFlag == 1u)
  85   {
  86     arm_radix2_butterfly_inverse_q15(pSrc, S->fftLen,
  87                                      S->pTwiddle, S->twidCoefModifier);
  88   }
  89   else
  90   {
  91     arm_radix2_butterfly_q15(pSrc, S->fftLen,
  92                              S->pTwiddle, S->twidCoefModifier);
  93   }
  94
  95   arm_bitreversal_q15(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
  96 }
  97
  98 /**
  99  * @} end of ComplexFFT group
 100  */
 101
 102 void arm_radix2_butterfly_q15(
 103   q15_t * pSrc,
 104   uint32_t fftLen,
 105   q15_t * pCoef,
 106   uint16_t twidCoefModifier)
 107 {
 108 #ifndef ARM_MATH_CM0_FAMILY
 109
 110   unsigned i, j, k, l;
 111   unsigned n1, n2, ia;
 112   q15_t in;
 113   q31_t T, S, R;
 114   q31_t coeff, out1, out2;
 115
 116   //N = fftLen;
 117   n2 = fftLen;
 118
 119   n1 = n2;
 120   n2 = n2 >> 1;
 121   ia = 0;
 122
 123   // loop for groups
 124   for (i = 0; i < n2; i++)
 125   {
 126     coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 127
 128     ia = ia + twidCoefModifier;
 129
 130     l = i + n2;
 131
 132     T = _SIMD32_OFFSET(pSrc + (2 * i));
 133     in = ((int16_t) (T & 0xFFFF)) >> 2;
 134     T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 135
 136     S = _SIMD32_OFFSET(pSrc + (2 * l));
 137     in = ((int16_t) (S & 0xFFFF)) >> 2;
 138     S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 139
 140     R = __QSUB16(T, S);
 141
 142     _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 143
 144 #ifndef ARM_MATH_BIG_ENDIAN
 145
 146     out1 = __SMUAD(coeff, R) >> 16;
 147     out2 = __SMUSDX(coeff, R);
 148
 149 #else
 150
 151     out1 = __SMUSDX(R, coeff) >> 16u;
 152     out2 = __SMUAD(coeff, R);
 153
 154 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 155
 156     _SIMD32_OFFSET(pSrc + (2u * l)) =
 157       (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 158
 159     coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 160
 161     ia = ia + twidCoefModifier;
 162
 163     // loop for butterfly
 164     i++;
 165     l++;
 166
 167     T = _SIMD32_OFFSET(pSrc + (2 * i));
 168     in = ((int16_t) (T & 0xFFFF)) >> 2;
 169     T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 170
 171     S = _SIMD32_OFFSET(pSrc + (2 * l));
 172     in = ((int16_t) (S & 0xFFFF)) >> 2;
 173     S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 174
 175     R = __QSUB16(T, S);
 176
 177     _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 178
 179 #ifndef ARM_MATH_BIG_ENDIAN
 180
 181     out1 = __SMUAD(coeff, R) >> 16;
 182     out2 = __SMUSDX(coeff, R);
 183
 184 #else
 185
 186     out1 = __SMUSDX(R, coeff) >> 16u;
 187     out2 = __SMUAD(coeff, R);
 188
 189 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 190
 191     _SIMD32_OFFSET(pSrc + (2u * l)) =
 192       (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 193
 194   }                             // groups loop end
 195
 196   twidCoefModifier = twidCoefModifier << 1u;
 197
 198   // loop for stage
 199   for (k = fftLen / 2; k > 2; k = k >> 1)
 200   {
 201     n1 = n2;
 202     n2 = n2 >> 1;
 203     ia = 0;
 204
 205     // loop for groups
 206     for (j = 0; j < n2; j++)
 207     {
 208       coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 209
 210       ia = ia + twidCoefModifier;
 211
 212       // loop for butterfly
 213       for (i = j; i < fftLen; i += n1)
 214       {
 215         l = i + n2;
 216
 217         T = _SIMD32_OFFSET(pSrc + (2 * i));
 218
 219         S = _SIMD32_OFFSET(pSrc + (2 * l));
 220
 221         R = __QSUB16(T, S);
 222
 223         _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 224
 225 #ifndef ARM_MATH_BIG_ENDIAN
 226
 227         out1 = __SMUAD(coeff, R) >> 16;
 228         out2 = __SMUSDX(coeff, R);
 229
 230 #else
 231
 232         out1 = __SMUSDX(R, coeff) >> 16u;
 233         out2 = __SMUAD(coeff, R);
 234
 235 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 236
 237         _SIMD32_OFFSET(pSrc + (2u * l)) =
 238           (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 239
 240         i += n1;
 241
 242         l = i + n2;
 243
 244         T = _SIMD32_OFFSET(pSrc + (2 * i));
 245
 246         S = _SIMD32_OFFSET(pSrc + (2 * l));
 247
 248         R = __QSUB16(T, S);
 249
 250         _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 251
 252 #ifndef ARM_MATH_BIG_ENDIAN
 253
 254         out1 = __SMUAD(coeff, R) >> 16;
 255         out2 = __SMUSDX(coeff, R);
 256
 257 #else
 258
 259         out1 = __SMUSDX(R, coeff) >> 16u;
 260         out2 = __SMUAD(coeff, R);
 261
 262 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 263
 264         _SIMD32_OFFSET(pSrc + (2u * l)) =
 265           (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 266
 267       }                         // butterfly loop end
 268
 269     }                           // groups loop end
 270
 271     twidCoefModifier = twidCoefModifier << 1u;
 272   }                             // stages loop end
 273
 274   n1 = n2;
 275   n2 = n2 >> 1;
 276   ia = 0;
 277
 278   coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 279
 280   ia = ia + twidCoefModifier;
 281
 282   // loop for butterfly
 283   for (i = 0; i < fftLen; i += n1)
 284   {
 285     l = i + n2;
 286
 287     T = _SIMD32_OFFSET(pSrc + (2 * i));
 288
 289     S = _SIMD32_OFFSET(pSrc + (2 * l));
 290
 291     R = __QSUB16(T, S);
 292
 293     _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
 294
 295     _SIMD32_OFFSET(pSrc + (2u * l)) = R;
 296
 297     i += n1;
 298     l = i + n2;
 299
 300     T = _SIMD32_OFFSET(pSrc + (2 * i));
 301
 302     S = _SIMD32_OFFSET(pSrc + (2 * l));
 303
 304     R = __QSUB16(T, S);
 305
 306     _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
 307
 308     _SIMD32_OFFSET(pSrc + (2u * l)) = R;
 309
 310   }                             // groups loop end
 311
 312
 313 #else
 314
 315   unsigned i, j, k, l;
 316   unsigned n1, n2, ia;
 317   q15_t xt, yt, cosVal, sinVal;
 318
 319
 320   //N = fftLen;
 321   n2 = fftLen;
 322
 323   n1 = n2;
 324   n2 = n2 >> 1;
 325   ia = 0;
 326
 327   // loop for groups
 328   for (j = 0; j < n2; j++)
 329   {
 330     cosVal = pCoef[ia * 2];
 331     sinVal = pCoef[(ia * 2) + 1];
 332     ia = ia + twidCoefModifier;
 333
 334     // loop for butterfly
 335     for (i = j; i < fftLen; i += n1)
 336     {
 337       l = i + n2;
 338       xt = (pSrc[2 * i] >> 2u) - (pSrc[2 * l] >> 2u);
 339       pSrc[2 * i] = ((pSrc[2 * i] >> 2u) + (pSrc[2 * l] >> 2u)) >> 1u;
 340
 341       yt = (pSrc[2 * i + 1] >> 2u) - (pSrc[2 * l + 1] >> 2u);
 342       pSrc[2 * i + 1] =
 343         ((pSrc[2 * l + 1] >> 2u) + (pSrc[2 * i + 1] >> 2u)) >> 1u;
 344
 345       pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
 346                       ((int16_t) (((q31_t) yt * sinVal) >> 16)));
 347
 348       pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
 349                            ((int16_t) (((q31_t) xt * sinVal) >> 16)));
 350
 351     }                           // butterfly loop end
 352
 353   }                             // groups loop end
 354
 355   twidCoefModifier = twidCoefModifier << 1u;
 356
 357   // loop for stage
 358   for (k = fftLen / 2; k > 2; k = k >> 1)
 359   {
 360     n1 = n2;
 361     n2 = n2 >> 1;
 362     ia = 0;
 363
 364     // loop for groups
 365     for (j = 0; j < n2; j++)
 366     {
 367       cosVal = pCoef[ia * 2];
 368       sinVal = pCoef[(ia * 2) + 1];
 369       ia = ia + twidCoefModifier;
 370
 371       // loop for butterfly
 372       for (i = j; i < fftLen; i += n1)
 373       {
 374         l = i + n2;
 375         xt = pSrc[2 * i] - pSrc[2 * l];
 376         pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1u;
 377
 378         yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
 379         pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1u;
 380
 381         pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
 382                         ((int16_t) (((q31_t) yt * sinVal) >> 16)));
 383
 384         pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
 385                              ((int16_t) (((q31_t) xt * sinVal) >> 16)));
 386
 387       }                         // butterfly loop end
 388
 389     }                           // groups loop end
 390
 391     twidCoefModifier = twidCoefModifier << 1u;
 392   }                             // stages loop end
 393
 394   n1 = n2;
 395   n2 = n2 >> 1;
 396   ia = 0;
 397
 398   // loop for groups
 399   for (j = 0; j < n2; j++)
 400   {
 401     cosVal = pCoef[ia * 2];
 402     sinVal = pCoef[(ia * 2) + 1];
 403
 404     ia = ia + twidCoefModifier;
 405
 406     // loop for butterfly
 407     for (i = j; i < fftLen; i += n1)
 408     {
 409       l = i + n2;
 410       xt = pSrc[2 * i] - pSrc[2 * l];
 411       pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);
 412
 413       yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
 414       pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);
 415
 416       pSrc[2u * l] = xt;
 417
 418       pSrc[2u * l + 1u] = yt;
 419
 420     }                           // butterfly loop end
 421
 422   }                             // groups loop end
 423
 424   twidCoefModifier = twidCoefModifier << 1u;
 425
 426 #endif //             #ifndef ARM_MATH_CM0_FAMILY
 427
 428 }
 429
 430
 431 void arm_radix2_butterfly_inverse_q15(
 432   q15_t * pSrc,
 433   uint32_t fftLen,
 434   q15_t * pCoef,
 435   uint16_t twidCoefModifier)
 436 {
 437 #ifndef ARM_MATH_CM0_FAMILY
 438
 439   unsigned i, j, k, l;
 440   unsigned n1, n2, ia;
 441   q15_t in;
 442   q31_t T, S, R;
 443   q31_t coeff, out1, out2;
 444
 445   //N = fftLen;
 446   n2 = fftLen;
 447
 448   n1 = n2;
 449   n2 = n2 >> 1;
 450   ia = 0;
 451
 452   // loop for groups
 453   for (i = 0; i < n2; i++)
 454   {
 455     coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 456
 457     ia = ia + twidCoefModifier;
 458
 459     l = i + n2;
 460
 461     T = _SIMD32_OFFSET(pSrc + (2 * i));
 462     in = ((int16_t) (T & 0xFFFF)) >> 2;
 463     T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 464
 465     S = _SIMD32_OFFSET(pSrc + (2 * l));
 466     in = ((int16_t) (S & 0xFFFF)) >> 2;
 467     S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 468
 469     R = __QSUB16(T, S);
 470
 471     _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 472
 473 #ifndef ARM_MATH_BIG_ENDIAN
 474
 475     out1 = __SMUSD(coeff, R) >> 16;
 476     out2 = __SMUADX(coeff, R);
 477 #else
 478
 479     out1 = __SMUADX(R, coeff) >> 16u;
 480     out2 = __SMUSD(__QSUB(0, coeff), R);
 481
 482 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 483
 484     _SIMD32_OFFSET(pSrc + (2u * l)) =
 485       (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 486
 487     coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 488
 489     ia = ia + twidCoefModifier;
 490
 491     // loop for butterfly
 492     i++;
 493     l++;
 494
 495     T = _SIMD32_OFFSET(pSrc + (2 * i));
 496     in = ((int16_t) (T & 0xFFFF)) >> 2;
 497     T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 498
 499     S = _SIMD32_OFFSET(pSrc + (2 * l));
 500     in = ((int16_t) (S & 0xFFFF)) >> 2;
 501     S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
 502
 503     R = __QSUB16(T, S);
 504
 505     _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 506
 507 #ifndef ARM_MATH_BIG_ENDIAN
 508
 509     out1 = __SMUSD(coeff, R) >> 16;
 510     out2 = __SMUADX(coeff, R);
 511 #else
 512
 513     out1 = __SMUADX(R, coeff) >> 16u;
 514     out2 = __SMUSD(__QSUB(0, coeff), R);
 515
 516 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 517
 518     _SIMD32_OFFSET(pSrc + (2u * l)) =
 519       (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 520
 521   }                             // groups loop end
 522
 523   twidCoefModifier = twidCoefModifier << 1u;
 524
 525   // loop for stage
 526   for (k = fftLen / 2; k > 2; k = k >> 1)
 527   {
 528     n1 = n2;
 529     n2 = n2 >> 1;
 530     ia = 0;
 531
 532     // loop for groups
 533     for (j = 0; j < n2; j++)
 534     {
 535       coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 536
 537       ia = ia + twidCoefModifier;
 538
 539       // loop for butterfly
 540       for (i = j; i < fftLen; i += n1)
 541       {
 542         l = i + n2;
 543
 544         T = _SIMD32_OFFSET(pSrc + (2 * i));
 545
 546         S = _SIMD32_OFFSET(pSrc + (2 * l));
 547
 548         R = __QSUB16(T, S);
 549
 550         _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 551
 552 #ifndef ARM_MATH_BIG_ENDIAN
 553
 554         out1 = __SMUSD(coeff, R) >> 16;
 555         out2 = __SMUADX(coeff, R);
 556
 557 #else
 558
 559         out1 = __SMUADX(R, coeff) >> 16u;
 560         out2 = __SMUSD(__QSUB(0, coeff), R);
 561
 562 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 563
 564         _SIMD32_OFFSET(pSrc + (2u * l)) =
 565           (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 566
 567         i += n1;
 568
 569         l = i + n2;
 570
 571         T = _SIMD32_OFFSET(pSrc + (2 * i));
 572
 573         S = _SIMD32_OFFSET(pSrc + (2 * l));
 574
 575         R = __QSUB16(T, S);
 576
 577         _SIMD32_OFFSET(pSrc + (2 * i)) = __SHADD16(T, S);
 578
 579 #ifndef ARM_MATH_BIG_ENDIAN
 580
 581         out1 = __SMUSD(coeff, R) >> 16;
 582         out2 = __SMUADX(coeff, R);
 583 #else
 584
 585         out1 = __SMUADX(R, coeff) >> 16u;
 586         out2 = __SMUSD(__QSUB(0, coeff), R);
 587
 588 #endif //     #ifndef ARM_MATH_BIG_ENDIAN
 589
 590         _SIMD32_OFFSET(pSrc + (2u * l)) =
 591           (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
 592
 593       }                         // butterfly loop end
 594
 595     }                           // groups loop end
 596
 597     twidCoefModifier = twidCoefModifier << 1u;
 598   }                             // stages loop end
 599
 600   n1 = n2;
 601   n2 = n2 >> 1;
 602   ia = 0;
 603
 604   // loop for groups
 605   for (j = 0; j < n2; j++)
 606   {
 607     coeff = _SIMD32_OFFSET(pCoef + (ia * 2u));
 608
 609     ia = ia + twidCoefModifier;
 610
 611     // loop for butterfly
 612     for (i = j; i < fftLen; i += n1)
 613     {
 614       l = i + n2;
 615
 616       T = _SIMD32_OFFSET(pSrc + (2 * i));
 617
 618       S = _SIMD32_OFFSET(pSrc + (2 * l));
 619
 620       R = __QSUB16(T, S);
 621
 622       _SIMD32_OFFSET(pSrc + (2 * i)) = __QADD16(T, S);
 623
 624       _SIMD32_OFFSET(pSrc + (2u * l)) = R;
 625
 626     }                           // butterfly loop end
 627
 628   }                             // groups loop end
 629
 630   twidCoefModifier = twidCoefModifier << 1u;
 631
 632 #else
 633
 634
 635   unsigned i, j, k, l;
 636   unsigned n1, n2, ia;
 637   q15_t xt, yt, cosVal, sinVal;
 638
 639   //N = fftLen;
 640   n2 = fftLen;
 641
 642   n1 = n2;
 643   n2 = n2 >> 1;
 644   ia = 0;
 645
 646   // loop for groups
 647   for (j = 0; j < n2; j++)
 648   {
 649     cosVal = pCoef[ia * 2];
 650     sinVal = pCoef[(ia * 2) + 1];
 651     ia = ia + twidCoefModifier;
 652
 653     // loop for butterfly
 654     for (i = j; i < fftLen; i += n1)
 655     {
 656       l = i + n2;
 657       xt = (pSrc[2 * i] >> 2u) - (pSrc[2 * l] >> 2u);
 658       pSrc[2 * i] = ((pSrc[2 * i] >> 2u) + (pSrc[2 * l] >> 2u)) >> 1u;
 659
 660       yt = (pSrc[2 * i + 1] >> 2u) - (pSrc[2 * l + 1] >> 2u);
 661       pSrc[2 * i + 1] =
 662         ((pSrc[2 * l + 1] >> 2u) + (pSrc[2 * i + 1] >> 2u)) >> 1u;
 663
 664       pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
 665                       ((int16_t) (((q31_t) yt * sinVal) >> 16)));
 666
 667       pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
 668                            ((int16_t) (((q31_t) xt * sinVal) >> 16)));
 669
 670     }                           // butterfly loop end
 671
 672   }                             // groups loop end
 673
 674   twidCoefModifier = twidCoefModifier << 1u;
 675
 676   // loop for stage
 677   for (k = fftLen / 2; k > 2; k = k >> 1)
 678   {
 679     n1 = n2;
 680     n2 = n2 >> 1;
 681     ia = 0;
 682
 683     // loop for groups
 684     for (j = 0; j < n2; j++)
 685     {
 686       cosVal = pCoef[ia * 2];
 687       sinVal = pCoef[(ia * 2) + 1];
 688       ia = ia + twidCoefModifier;
 689
 690       // loop for butterfly
 691       for (i = j; i < fftLen; i += n1)
 692       {
 693         l = i + n2;
 694         xt = pSrc[2 * i] - pSrc[2 * l];
 695         pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]) >> 1u;
 696
 697         yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
 698         pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]) >> 1u;
 699
 700         pSrc[2u * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
 701                         ((int16_t) (((q31_t) yt * sinVal) >> 16)));
 702
 703         pSrc[2u * l + 1u] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
 704                              ((int16_t) (((q31_t) xt * sinVal) >> 16)));
 705
 706       }                         // butterfly loop end
 707
 708     }                           // groups loop end
 709
 710     twidCoefModifier = twidCoefModifier << 1u;
 711   }                             // stages loop end
 712
 713   n1 = n2;
 714   n2 = n2 >> 1;
 715   ia = 0;
 716
 717   cosVal = pCoef[ia * 2];
 718   sinVal = pCoef[(ia * 2) + 1];
 719
 720   ia = ia + twidCoefModifier;
 721
 722   // loop for butterfly
 723   for (i = 0; i < fftLen; i += n1)
 724   {
 725     l = i + n2;
 726     xt = pSrc[2 * i] - pSrc[2 * l];
 727     pSrc[2 * i] = (pSrc[2 * i] + pSrc[2 * l]);
 728
 729     yt = pSrc[2 * i + 1] - pSrc[2 * l + 1];
 730     pSrc[2 * i + 1] = (pSrc[2 * l + 1] + pSrc[2 * i + 1]);
 731
 732     pSrc[2u * l] = xt;
 733
 734     pSrc[2u * l + 1u] = yt;
 735
 736   }                             // groups loop end
 737
 738
 739 #endif //             #ifndef ARM_MATH_CM0_FAMILY
 740
 741 }