CMSIS DSP library
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arm_correlate_fast_q31.c
00001 /* ---------------------------------------------------------------------- 00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved. 00003 * 00004 * $Date: 17. January 2013 00005 * $Revision: V1.4.1 00006 * 00007 * Project: CMSIS DSP Library 00008 * Title: arm_correlate_fast_q31.c 00009 * 00010 * Description: Fast Q31 Correlation. 00011 * 00012 * Target Processor: Cortex-M4/Cortex-M3 00013 * 00014 * Redistribution and use in source and binary forms, with or without 00015 * modification, are permitted provided that the following conditions 00016 * are met: 00017 * - Redistributions of source code must retain the above copyright 00018 * notice, this list of conditions and the following disclaimer. 00019 * - Redistributions in binary form must reproduce the above copyright 00020 * notice, this list of conditions and the following disclaimer in 00021 * the documentation and/or other materials provided with the 00022 * distribution. 00023 * - Neither the name of ARM LIMITED nor the names of its contributors 00024 * may be used to endorse or promote products derived from this 00025 * software without specific prior written permission. 00026 * 00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 00038 * POSSIBILITY OF SUCH DAMAGE. 00039 * -------------------------------------------------------------------- */ 00040 00041 #include "arm_math.h" 00042 00043 /** 00044 * @ingroup groupFilters 00045 */ 00046 00047 /** 00048 * @addtogroup Corr 00049 * @{ 00050 */ 00051 00052 /** 00053 * @brief Correlation of Q31 sequences (fast version) for Cortex-M3 and Cortex-M4. 00054 * @param[in] *pSrcA points to the first input sequence. 00055 * @param[in] srcALen length of the first input sequence. 00056 * @param[in] *pSrcB points to the second input sequence. 00057 * @param[in] srcBLen length of the second input sequence. 00058 * @param[out] *pDst points to the location where the output result is written. Length 2 * max(srcALen, srcBLen) - 1. 00059 * @return none. 00060 * 00061 * @details 00062 * <b>Scaling and Overflow Behavior:</b> 00063 * 00064 * \par 00065 * This function is optimized for speed at the expense of fixed-point precision and overflow protection. 00066 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format. 00067 * These intermediate results are accumulated in a 32-bit register in 2.30 format. 00068 * Finally, the accumulator is saturated and converted to a 1.31 result. 00069 * 00070 * \par 00071 * The fast version has the same overflow behavior as the standard version but provides less precision since it discards the low 32 bits of each multiplication result. 00072 * In order to avoid overflows completely the input signals must be scaled down. 00073 * The input signals should be scaled down to avoid intermediate overflows. 00074 * Scale down one of the inputs by 1/min(srcALen, srcBLen)to avoid overflows since a 00075 * maximum of min(srcALen, srcBLen) number of additions is carried internally. 00076 * 00077 * \par 00078 * See <code>arm_correlate_q31()</code> for a slower implementation of this function which uses 64-bit accumulation to provide higher precision. 00079 */ 00080 00081 void arm_correlate_fast_q31( 00082 q31_t * pSrcA, 00083 uint32_t srcALen, 00084 q31_t * pSrcB, 00085 uint32_t srcBLen, 00086 q31_t * pDst) 00087 { 00088 q31_t *pIn1; /* inputA pointer */ 00089 q31_t *pIn2; /* inputB pointer */ 00090 q31_t *pOut = pDst; /* output pointer */ 00091 q31_t *px; /* Intermediate inputA pointer */ 00092 q31_t *py; /* Intermediate inputB pointer */ 00093 q31_t *pSrc1; /* Intermediate pointers */ 00094 q31_t sum, acc0, acc1, acc2, acc3; /* Accumulators */ 00095 q31_t x0, x1, x2, x3, c0; /* temporary variables for holding input and coefficient values */ 00096 uint32_t j, k = 0u, count, blkCnt, outBlockSize, blockSize1, blockSize2, blockSize3; /* loop counter */ 00097 int32_t inc = 1; /* Destination address modifier */ 00098 00099 00100 /* The algorithm implementation is based on the lengths of the inputs. */ 00101 /* srcB is always made to slide across srcA. */ 00102 /* So srcBLen is always considered as shorter or equal to srcALen */ 00103 if(srcALen >= srcBLen) 00104 { 00105 /* Initialization of inputA pointer */ 00106 pIn1 = (pSrcA); 00107 00108 /* Initialization of inputB pointer */ 00109 pIn2 = (pSrcB); 00110 00111 /* Number of output samples is calculated */ 00112 outBlockSize = (2u * srcALen) - 1u; 00113 00114 /* When srcALen > srcBLen, zero padding is done to srcB 00115 * to make their lengths equal. 00116 * Instead, (outBlockSize - (srcALen + srcBLen - 1)) 00117 * number of output samples are made zero */ 00118 j = outBlockSize - (srcALen + (srcBLen - 1u)); 00119 00120 /* Updating the pointer position to non zero value */ 00121 pOut += j; 00122 00123 } 00124 else 00125 { 00126 /* Initialization of inputA pointer */ 00127 pIn1 = (pSrcB); 00128 00129 /* Initialization of inputB pointer */ 00130 pIn2 = (pSrcA); 00131 00132 /* srcBLen is always considered as shorter or equal to srcALen */ 00133 j = srcBLen; 00134 srcBLen = srcALen; 00135 srcALen = j; 00136 00137 /* CORR(x, y) = Reverse order(CORR(y, x)) */ 00138 /* Hence set the destination pointer to point to the last output sample */ 00139 pOut = pDst + ((srcALen + srcBLen) - 2u); 00140 00141 /* Destination address modifier is set to -1 */ 00142 inc = -1; 00143 00144 } 00145 00146 /* The function is internally 00147 * divided into three parts according to the number of multiplications that has to be 00148 * taken place between inputA samples and inputB samples. In the first part of the 00149 * algorithm, the multiplications increase by one for every iteration. 00150 * In the second part of the algorithm, srcBLen number of multiplications are done. 00151 * In the third part of the algorithm, the multiplications decrease by one 00152 * for every iteration.*/ 00153 /* The algorithm is implemented in three stages. 00154 * The loop counters of each stage is initiated here. */ 00155 blockSize1 = srcBLen - 1u; 00156 blockSize2 = srcALen - (srcBLen - 1u); 00157 blockSize3 = blockSize1; 00158 00159 /* -------------------------- 00160 * Initializations of stage1 00161 * -------------------------*/ 00162 00163 /* sum = x[0] * y[srcBlen - 1] 00164 * sum = x[0] * y[srcBlen - 2] + x[1] * y[srcBlen - 1] 00165 * .... 00166 * sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen - 1] * y[srcBLen - 1] 00167 */ 00168 00169 /* In this stage the MAC operations are increased by 1 for every iteration. 00170 The count variable holds the number of MAC operations performed */ 00171 count = 1u; 00172 00173 /* Working pointer of inputA */ 00174 px = pIn1; 00175 00176 /* Working pointer of inputB */ 00177 pSrc1 = pIn2 + (srcBLen - 1u); 00178 py = pSrc1; 00179 00180 /* ------------------------ 00181 * Stage1 process 00182 * ----------------------*/ 00183 00184 /* The first stage starts here */ 00185 while(blockSize1 > 0u) 00186 { 00187 /* Accumulator is made zero for every iteration */ 00188 sum = 0; 00189 00190 /* Apply loop unrolling and compute 4 MACs simultaneously. */ 00191 k = count >> 2; 00192 00193 /* First part of the processing with loop unrolling. Compute 4 MACs at a time. 00194 ** a second loop below computes MACs for the remaining 1 to 3 samples. */ 00195 while(k > 0u) 00196 { 00197 /* x[0] * y[srcBLen - 4] */ 00198 sum = (q31_t) ((((q63_t) sum << 32) + 00199 ((q63_t) * px++ * (*py++))) >> 32); 00200 /* x[1] * y[srcBLen - 3] */ 00201 sum = (q31_t) ((((q63_t) sum << 32) + 00202 ((q63_t) * px++ * (*py++))) >> 32); 00203 /* x[2] * y[srcBLen - 2] */ 00204 sum = (q31_t) ((((q63_t) sum << 32) + 00205 ((q63_t) * px++ * (*py++))) >> 32); 00206 /* x[3] * y[srcBLen - 1] */ 00207 sum = (q31_t) ((((q63_t) sum << 32) + 00208 ((q63_t) * px++ * (*py++))) >> 32); 00209 00210 /* Decrement the loop counter */ 00211 k--; 00212 } 00213 00214 /* If the count is not a multiple of 4, compute any remaining MACs here. 00215 ** No loop unrolling is used. */ 00216 k = count % 0x4u; 00217 00218 while(k > 0u) 00219 { 00220 /* Perform the multiply-accumulates */ 00221 /* x[0] * y[srcBLen - 1] */ 00222 sum = (q31_t) ((((q63_t) sum << 32) + 00223 ((q63_t) * px++ * (*py++))) >> 32); 00224 00225 /* Decrement the loop counter */ 00226 k--; 00227 } 00228 00229 /* Store the result in the accumulator in the destination buffer. */ 00230 *pOut = sum << 1; 00231 /* Destination pointer is updated according to the address modifier, inc */ 00232 pOut += inc; 00233 00234 /* Update the inputA and inputB pointers for next MAC calculation */ 00235 py = pSrc1 - count; 00236 px = pIn1; 00237 00238 /* Increment the MAC count */ 00239 count++; 00240 00241 /* Decrement the loop counter */ 00242 blockSize1--; 00243 } 00244 00245 /* -------------------------- 00246 * Initializations of stage2 00247 * ------------------------*/ 00248 00249 /* sum = x[0] * y[0] + x[1] * y[1] +...+ x[srcBLen-1] * y[srcBLen-1] 00250 * sum = x[1] * y[0] + x[2] * y[1] +...+ x[srcBLen] * y[srcBLen-1] 00251 * .... 00252 * sum = x[srcALen-srcBLen-2] * y[0] + x[srcALen-srcBLen-1] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] 00253 */ 00254 00255 /* Working pointer of inputA */ 00256 px = pIn1; 00257 00258 /* Working pointer of inputB */ 00259 py = pIn2; 00260 00261 /* count is index by which the pointer pIn1 to be incremented */ 00262 count = 0u; 00263 00264 /* ------------------- 00265 * Stage2 process 00266 * ------------------*/ 00267 00268 /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed. 00269 * So, to loop unroll over blockSize2, 00270 * srcBLen should be greater than or equal to 4 */ 00271 if(srcBLen >= 4u) 00272 { 00273 /* Loop unroll over blockSize2, by 4 */ 00274 blkCnt = blockSize2 >> 2u; 00275 00276 while(blkCnt > 0u) 00277 { 00278 /* Set all accumulators to zero */ 00279 acc0 = 0; 00280 acc1 = 0; 00281 acc2 = 0; 00282 acc3 = 0; 00283 00284 /* read x[0], x[1], x[2] samples */ 00285 x0 = *(px++); 00286 x1 = *(px++); 00287 x2 = *(px++); 00288 00289 /* Apply loop unrolling and compute 4 MACs simultaneously. */ 00290 k = srcBLen >> 2u; 00291 00292 /* First part of the processing with loop unrolling. Compute 4 MACs at a time. 00293 ** a second loop below computes MACs for the remaining 1 to 3 samples. */ 00294 do 00295 { 00296 /* Read y[0] sample */ 00297 c0 = *(py++); 00298 00299 /* Read x[3] sample */ 00300 x3 = *(px++); 00301 00302 /* Perform the multiply-accumulate */ 00303 /* acc0 += x[0] * y[0] */ 00304 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); 00305 /* acc1 += x[1] * y[0] */ 00306 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); 00307 /* acc2 += x[2] * y[0] */ 00308 acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32); 00309 /* acc3 += x[3] * y[0] */ 00310 acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32); 00311 00312 /* Read y[1] sample */ 00313 c0 = *(py++); 00314 00315 /* Read x[4] sample */ 00316 x0 = *(px++); 00317 00318 /* Perform the multiply-accumulates */ 00319 /* acc0 += x[1] * y[1] */ 00320 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x1 * c0)) >> 32); 00321 /* acc1 += x[2] * y[1] */ 00322 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x2 * c0)) >> 32); 00323 /* acc2 += x[3] * y[1] */ 00324 acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x3 * c0)) >> 32); 00325 /* acc3 += x[4] * y[1] */ 00326 acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x0 * c0)) >> 32); 00327 00328 /* Read y[2] sample */ 00329 c0 = *(py++); 00330 00331 /* Read x[5] sample */ 00332 x1 = *(px++); 00333 00334 /* Perform the multiply-accumulates */ 00335 /* acc0 += x[2] * y[2] */ 00336 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x2 * c0)) >> 32); 00337 /* acc1 += x[3] * y[2] */ 00338 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x3 * c0)) >> 32); 00339 /* acc2 += x[4] * y[2] */ 00340 acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x0 * c0)) >> 32); 00341 /* acc3 += x[5] * y[2] */ 00342 acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x1 * c0)) >> 32); 00343 00344 /* Read y[3] sample */ 00345 c0 = *(py++); 00346 00347 /* Read x[6] sample */ 00348 x2 = *(px++); 00349 00350 /* Perform the multiply-accumulates */ 00351 /* acc0 += x[3] * y[3] */ 00352 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x3 * c0)) >> 32); 00353 /* acc1 += x[4] * y[3] */ 00354 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x0 * c0)) >> 32); 00355 /* acc2 += x[5] * y[3] */ 00356 acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x1 * c0)) >> 32); 00357 /* acc3 += x[6] * y[3] */ 00358 acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x2 * c0)) >> 32); 00359 00360 00361 } while(--k); 00362 00363 /* If the srcBLen is not a multiple of 4, compute any remaining MACs here. 00364 ** No loop unrolling is used. */ 00365 k = srcBLen % 0x4u; 00366 00367 while(k > 0u) 00368 { 00369 /* Read y[4] sample */ 00370 c0 = *(py++); 00371 00372 /* Read x[7] sample */ 00373 x3 = *(px++); 00374 00375 /* Perform the multiply-accumulates */ 00376 /* acc0 += x[4] * y[4] */ 00377 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); 00378 /* acc1 += x[5] * y[4] */ 00379 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); 00380 /* acc2 += x[6] * y[4] */ 00381 acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32); 00382 /* acc3 += x[7] * y[4] */ 00383 acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32); 00384 00385 /* Reuse the present samples for the next MAC */ 00386 x0 = x1; 00387 x1 = x2; 00388 x2 = x3; 00389 00390 /* Decrement the loop counter */ 00391 k--; 00392 } 00393 00394 /* Store the result in the accumulator in the destination buffer. */ 00395 *pOut = (q31_t) (acc0 << 1); 00396 /* Destination pointer is updated according to the address modifier, inc */ 00397 pOut += inc; 00398 00399 *pOut = (q31_t) (acc1 << 1); 00400 pOut += inc; 00401 00402 *pOut = (q31_t) (acc2 << 1); 00403 pOut += inc; 00404 00405 *pOut = (q31_t) (acc3 << 1); 00406 pOut += inc; 00407 00408 /* Increment the pointer pIn1 index, count by 4 */ 00409 count += 4u; 00410 00411 /* Update the inputA and inputB pointers for next MAC calculation */ 00412 px = pIn1 + count; 00413 py = pIn2; 00414 00415 00416 /* Decrement the loop counter */ 00417 blkCnt--; 00418 } 00419 00420 /* If the blockSize2 is not a multiple of 4, compute any remaining output samples here. 00421 ** No loop unrolling is used. */ 00422 blkCnt = blockSize2 % 0x4u; 00423 00424 while(blkCnt > 0u) 00425 { 00426 /* Accumulator is made zero for every iteration */ 00427 sum = 0; 00428 00429 /* Apply loop unrolling and compute 4 MACs simultaneously. */ 00430 k = srcBLen >> 2u; 00431 00432 /* First part of the processing with loop unrolling. Compute 4 MACs at a time. 00433 ** a second loop below computes MACs for the remaining 1 to 3 samples. */ 00434 while(k > 0u) 00435 { 00436 /* Perform the multiply-accumulates */ 00437 sum = (q31_t) ((((q63_t) sum << 32) + 00438 ((q63_t) * px++ * (*py++))) >> 32); 00439 sum = (q31_t) ((((q63_t) sum << 32) + 00440 ((q63_t) * px++ * (*py++))) >> 32); 00441 sum = (q31_t) ((((q63_t) sum << 32) + 00442 ((q63_t) * px++ * (*py++))) >> 32); 00443 sum = (q31_t) ((((q63_t) sum << 32) + 00444 ((q63_t) * px++ * (*py++))) >> 32); 00445 00446 /* Decrement the loop counter */ 00447 k--; 00448 } 00449 00450 /* If the srcBLen is not a multiple of 4, compute any remaining MACs here. 00451 ** No loop unrolling is used. */ 00452 k = srcBLen % 0x4u; 00453 00454 while(k > 0u) 00455 { 00456 /* Perform the multiply-accumulate */ 00457 sum = (q31_t) ((((q63_t) sum << 32) + 00458 ((q63_t) * px++ * (*py++))) >> 32); 00459 00460 /* Decrement the loop counter */ 00461 k--; 00462 } 00463 00464 /* Store the result in the accumulator in the destination buffer. */ 00465 *pOut = sum << 1; 00466 /* Destination pointer is updated according to the address modifier, inc */ 00467 pOut += inc; 00468 00469 /* Increment the MAC count */ 00470 count++; 00471 00472 /* Update the inputA and inputB pointers for next MAC calculation */ 00473 px = pIn1 + count; 00474 py = pIn2; 00475 00476 00477 /* Decrement the loop counter */ 00478 blkCnt--; 00479 } 00480 } 00481 else 00482 { 00483 /* If the srcBLen is not a multiple of 4, 00484 * the blockSize2 loop cannot be unrolled by 4 */ 00485 blkCnt = blockSize2; 00486 00487 while(blkCnt > 0u) 00488 { 00489 /* Accumulator is made zero for every iteration */ 00490 sum = 0; 00491 00492 /* Loop over srcBLen */ 00493 k = srcBLen; 00494 00495 while(k > 0u) 00496 { 00497 /* Perform the multiply-accumulate */ 00498 sum = (q31_t) ((((q63_t) sum << 32) + 00499 ((q63_t) * px++ * (*py++))) >> 32); 00500 00501 /* Decrement the loop counter */ 00502 k--; 00503 } 00504 00505 /* Store the result in the accumulator in the destination buffer. */ 00506 *pOut = sum << 1; 00507 /* Destination pointer is updated according to the address modifier, inc */ 00508 pOut += inc; 00509 00510 /* Increment the MAC count */ 00511 count++; 00512 00513 /* Update the inputA and inputB pointers for next MAC calculation */ 00514 px = pIn1 + count; 00515 py = pIn2; 00516 00517 /* Decrement the loop counter */ 00518 blkCnt--; 00519 } 00520 } 00521 00522 /* -------------------------- 00523 * Initializations of stage3 00524 * -------------------------*/ 00525 00526 /* sum += x[srcALen-srcBLen+1] * y[0] + x[srcALen-srcBLen+2] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] 00527 * sum += x[srcALen-srcBLen+2] * y[0] + x[srcALen-srcBLen+3] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] 00528 * .... 00529 * sum += x[srcALen-2] * y[0] + x[srcALen-1] * y[1] 00530 * sum += x[srcALen-1] * y[0] 00531 */ 00532 00533 /* In this stage the MAC operations are decreased by 1 for every iteration. 00534 The count variable holds the number of MAC operations performed */ 00535 count = srcBLen - 1u; 00536 00537 /* Working pointer of inputA */ 00538 pSrc1 = ((pIn1 + srcALen) - srcBLen) + 1u; 00539 px = pSrc1; 00540 00541 /* Working pointer of inputB */ 00542 py = pIn2; 00543 00544 /* ------------------- 00545 * Stage3 process 00546 * ------------------*/ 00547 00548 while(blockSize3 > 0u) 00549 { 00550 /* Accumulator is made zero for every iteration */ 00551 sum = 0; 00552 00553 /* Apply loop unrolling and compute 4 MACs simultaneously. */ 00554 k = count >> 2u; 00555 00556 /* First part of the processing with loop unrolling. Compute 4 MACs at a time. 00557 ** a second loop below computes MACs for the remaining 1 to 3 samples. */ 00558 while(k > 0u) 00559 { 00560 /* Perform the multiply-accumulates */ 00561 /* sum += x[srcALen - srcBLen + 4] * y[3] */ 00562 sum = (q31_t) ((((q63_t) sum << 32) + 00563 ((q63_t) * px++ * (*py++))) >> 32); 00564 /* sum += x[srcALen - srcBLen + 3] * y[2] */ 00565 sum = (q31_t) ((((q63_t) sum << 32) + 00566 ((q63_t) * px++ * (*py++))) >> 32); 00567 /* sum += x[srcALen - srcBLen + 2] * y[1] */ 00568 sum = (q31_t) ((((q63_t) sum << 32) + 00569 ((q63_t) * px++ * (*py++))) >> 32); 00570 /* sum += x[srcALen - srcBLen + 1] * y[0] */ 00571 sum = (q31_t) ((((q63_t) sum << 32) + 00572 ((q63_t) * px++ * (*py++))) >> 32); 00573 00574 /* Decrement the loop counter */ 00575 k--; 00576 } 00577 00578 /* If the count is not a multiple of 4, compute any remaining MACs here. 00579 ** No loop unrolling is used. */ 00580 k = count % 0x4u; 00581 00582 while(k > 0u) 00583 { 00584 /* Perform the multiply-accumulates */ 00585 sum = (q31_t) ((((q63_t) sum << 32) + 00586 ((q63_t) * px++ * (*py++))) >> 32); 00587 00588 /* Decrement the loop counter */ 00589 k--; 00590 } 00591 00592 /* Store the result in the accumulator in the destination buffer. */ 00593 *pOut = sum << 1; 00594 /* Destination pointer is updated according to the address modifier, inc */ 00595 pOut += inc; 00596 00597 /* Update the inputA and inputB pointers for next MAC calculation */ 00598 px = ++pSrc1; 00599 py = pIn2; 00600 00601 /* Decrement the MAC count */ 00602 count--; 00603 00604 /* Decrement the loop counter */ 00605 blockSize3--; 00606 } 00607 00608 } 00609 00610 /** 00611 * @} end of Corr group 00612 */
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