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git.gir.st - tmk_keyboard.git/blob - tmk_core/tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/FilteringFunctions/arm_conv_fast_q31.c
1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_conv_fast_q31.c
10 * Description: Q31 Convolution (fast version).
12 * Target Processor: Cortex-M4/Cortex-M3
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * - Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in
21 * the documentation and/or other materials provided with the
23 * - Neither the name of ARM LIMITED nor the names of its contributors
24 * may be used to endorse or promote products derived from this
25 * software without specific prior written permission.
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38 * POSSIBILITY OF SUCH DAMAGE.
39 * -------------------------------------------------------------------- */
44 * @ingroup groupFilters
53 * @param[in] *pSrcA points to the first input sequence.
54 * @param[in] srcALen length of the first input sequence.
55 * @param[in] *pSrcB points to the second input sequence.
56 * @param[in] srcBLen length of the second input sequence.
57 * @param[out] *pDst points to the location where the output result is written. Length srcALen+srcBLen-1.
61 * <b>Scaling and Overflow Behavior:</b>
64 * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
65 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
66 * These intermediate results are accumulated in a 32-bit register in 2.30 format.
67 * Finally, the accumulator is saturated and converted to a 1.31 result.
70 * 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.
71 * In order to avoid overflows completely the input signals must be scaled down.
72 * Scale down the inputs by log2(min(srcALen, srcBLen)) (log2 is read as log to the base 2) times to avoid overflows,
73 * as maximum of min(srcALen, srcBLen) number of additions are carried internally.
76 * See <code>arm_conv_q31()</code> for a slower implementation of this function which uses 64-bit accumulation to provide higher precision.
79 void arm_conv_fast_q31 (
86 q31_t
* pIn1
; /* inputA pointer */
87 q31_t
* pIn2
; /* inputB pointer */
88 q31_t
* pOut
= pDst
; /* output pointer */
89 q31_t
* px
; /* Intermediate inputA pointer */
90 q31_t
* py
; /* Intermediate inputB pointer */
91 q31_t
* pSrc1
, * pSrc2
; /* Intermediate pointers */
92 q31_t sum
, acc0
, acc1
, acc2
, acc3
; /* Accumulator */
93 q31_t x0
, x1
, x2
, x3
, c0
; /* Temporary variables to hold state and coefficient values */
94 uint32_t j
, k
, count
, blkCnt
, blockSize1
, blockSize2
, blockSize3
; /* loop counter */
96 /* The algorithm implementation is based on the lengths of the inputs. */
97 /* srcB is always made to slide across srcA. */
98 /* So srcBLen is always considered as shorter or equal to srcALen */
99 if ( srcALen
>= srcBLen
)
101 /* Initialization of inputA pointer */
104 /* Initialization of inputB pointer */
109 /* Initialization of inputA pointer */
112 /* Initialization of inputB pointer */
115 /* srcBLen is always considered as shorter or equal to srcALen */
121 /* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
122 /* The function is internally
123 * divided into three stages according to the number of multiplications that has to be
124 * taken place between inputA samples and inputB samples. In the first stage of the
125 * algorithm, the multiplications increase by one for every iteration.
126 * In the second stage of the algorithm, srcBLen number of multiplications are done.
127 * In the third stage of the algorithm, the multiplications decrease by one
128 * for every iteration. */
130 /* The algorithm is implemented in three stages.
131 The loop counters of each stage is initiated here. */
132 blockSize1
= srcBLen
- 1u ;
133 blockSize2
= srcALen
- ( srcBLen
- 1u );
134 blockSize3
= blockSize1
;
136 /* --------------------------
137 * Initializations of stage1
138 * -------------------------*/
141 * sum = x[0] * y[1] + x[1] * y[0]
143 * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
146 /* In this stage the MAC operations are increased by 1 for every iteration.
147 The count variable holds the number of MAC operations performed */
150 /* Working pointer of inputA */
153 /* Working pointer of inputB */
157 /* ------------------------
159 * ----------------------*/
161 /* The first stage starts here */
162 while ( blockSize1
> 0u )
164 /* Accumulator is made zero for every iteration */
167 /* Apply loop unrolling and compute 4 MACs simultaneously. */
170 /* First part of the processing with loop unrolling. Compute 4 MACs at a time.
171 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
174 /* x[0] * y[srcBLen - 1] */
175 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
176 (( q63_t
) * px
++ * (* py
--))) >> 32 );
178 /* x[1] * y[srcBLen - 2] */
179 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
180 (( q63_t
) * px
++ * (* py
--))) >> 32 );
182 /* x[2] * y[srcBLen - 3] */
183 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
184 (( q63_t
) * px
++ * (* py
--))) >> 32 );
186 /* x[3] * y[srcBLen - 4] */
187 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
188 (( q63_t
) * px
++ * (* py
--))) >> 32 );
190 /* Decrement the loop counter */
194 /* If the count is not a multiple of 4, compute any remaining MACs here.
195 ** No loop unrolling is used. */
200 /* Perform the multiply-accumulate */
201 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
202 (( q63_t
) * px
++ * (* py
--))) >> 32 );
204 /* Decrement the loop counter */
208 /* Store the result in the accumulator in the destination buffer. */
211 /* Update the inputA and inputB pointers for next MAC calculation */
215 /* Increment the MAC count */
218 /* Decrement the loop counter */
222 /* --------------------------
223 * Initializations of stage2
224 * ------------------------*/
226 /* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
227 * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
229 * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
232 /* Working pointer of inputA */
235 /* Working pointer of inputB */
236 pSrc2
= pIn2
+ ( srcBLen
- 1u );
239 /* count is index by which the pointer pIn1 to be incremented */
242 /* -------------------
244 * ------------------*/
246 /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
247 * So, to loop unroll over blockSize2,
248 * srcBLen should be greater than or equal to 4 */
251 /* Loop unroll over blockSize2, by 4 */
252 blkCnt
= blockSize2
>> 2u ;
256 /* Set all accumulators to zero */
262 /* read x[0], x[1], x[2] samples */
267 /* Apply loop unrolling and compute 4 MACs simultaneously. */
270 /* First part of the processing with loop unrolling. Compute 4 MACs at a time.
271 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
274 /* Read y[srcBLen - 1] sample */
277 /* Read x[3] sample */
280 /* Perform the multiply-accumulates */
281 /* acc0 += x[0] * y[srcBLen - 1] */
282 acc0
= ( q31_t
) (((( q63_t
) acc0
<< 32 ) + (( q63_t
) x0
* c0
)) >> 32 );
284 /* acc1 += x[1] * y[srcBLen - 1] */
285 acc1
= ( q31_t
) (((( q63_t
) acc1
<< 32 ) + (( q63_t
) x1
* c0
)) >> 32 );
287 /* acc2 += x[2] * y[srcBLen - 1] */
288 acc2
= ( q31_t
) (((( q63_t
) acc2
<< 32 ) + (( q63_t
) x2
* c0
)) >> 32 );
290 /* acc3 += x[3] * y[srcBLen - 1] */
291 acc3
= ( q31_t
) (((( q63_t
) acc3
<< 32 ) + (( q63_t
) x3
* c0
)) >> 32 );
293 /* Read y[srcBLen - 2] sample */
296 /* Read x[4] sample */
299 /* Perform the multiply-accumulate */
300 /* acc0 += x[1] * y[srcBLen - 2] */
301 acc0
= ( q31_t
) (((( q63_t
) acc0
<< 32 ) + (( q63_t
) x1
* c0
)) >> 32 );
302 /* acc1 += x[2] * y[srcBLen - 2] */
303 acc1
= ( q31_t
) (((( q63_t
) acc1
<< 32 ) + (( q63_t
) x2
* c0
)) >> 32 );
304 /* acc2 += x[3] * y[srcBLen - 2] */
305 acc2
= ( q31_t
) (((( q63_t
) acc2
<< 32 ) + (( q63_t
) x3
* c0
)) >> 32 );
306 /* acc3 += x[4] * y[srcBLen - 2] */
307 acc3
= ( q31_t
) (((( q63_t
) acc3
<< 32 ) + (( q63_t
) x0
* c0
)) >> 32 );
309 /* Read y[srcBLen - 3] sample */
312 /* Read x[5] sample */
315 /* Perform the multiply-accumulates */
316 /* acc0 += x[2] * y[srcBLen - 3] */
317 acc0
= ( q31_t
) (((( q63_t
) acc0
<< 32 ) + (( q63_t
) x2
* c0
)) >> 32 );
318 /* acc1 += x[3] * y[srcBLen - 3] */
319 acc1
= ( q31_t
) (((( q63_t
) acc1
<< 32 ) + (( q63_t
) x3
* c0
)) >> 32 );
320 /* acc2 += x[4] * y[srcBLen - 3] */
321 acc2
= ( q31_t
) (((( q63_t
) acc2
<< 32 ) + (( q63_t
) x0
* c0
)) >> 32 );
322 /* acc3 += x[5] * y[srcBLen - 3] */
323 acc3
= ( q31_t
) (((( q63_t
) acc3
<< 32 ) + (( q63_t
) x1
* c0
)) >> 32 );
325 /* Read y[srcBLen - 4] sample */
328 /* Read x[6] sample */
331 /* Perform the multiply-accumulates */
332 /* acc0 += x[3] * y[srcBLen - 4] */
333 acc0
= ( q31_t
) (((( q63_t
) acc0
<< 32 ) + (( q63_t
) x3
* c0
)) >> 32 );
334 /* acc1 += x[4] * y[srcBLen - 4] */
335 acc1
= ( q31_t
) (((( q63_t
) acc1
<< 32 ) + (( q63_t
) x0
* c0
)) >> 32 );
336 /* acc2 += x[5] * y[srcBLen - 4] */
337 acc2
= ( q31_t
) (((( q63_t
) acc2
<< 32 ) + (( q63_t
) x1
* c0
)) >> 32 );
338 /* acc3 += x[6] * y[srcBLen - 4] */
339 acc3
= ( q31_t
) (((( q63_t
) acc3
<< 32 ) + (( q63_t
) x2
* c0
)) >> 32 );
344 /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
345 ** No loop unrolling is used. */
350 /* Read y[srcBLen - 5] sample */
353 /* Read x[7] sample */
356 /* Perform the multiply-accumulates */
357 /* acc0 += x[4] * y[srcBLen - 5] */
358 acc0
= ( q31_t
) (((( q63_t
) acc0
<< 32 ) + (( q63_t
) x0
* c0
)) >> 32 );
359 /* acc1 += x[5] * y[srcBLen - 5] */
360 acc1
= ( q31_t
) (((( q63_t
) acc1
<< 32 ) + (( q63_t
) x1
* c0
)) >> 32 );
361 /* acc2 += x[6] * y[srcBLen - 5] */
362 acc2
= ( q31_t
) (((( q63_t
) acc2
<< 32 ) + (( q63_t
) x2
* c0
)) >> 32 );
363 /* acc3 += x[7] * y[srcBLen - 5] */
364 acc3
= ( q31_t
) (((( q63_t
) acc3
<< 32 ) + (( q63_t
) x3
* c0
)) >> 32 );
366 /* Reuse the present samples for the next MAC */
371 /* Decrement the loop counter */
375 /* Store the results in the accumulators in the destination buffer. */
376 * pOut
++ = ( q31_t
) ( acc0
<< 1 );
377 * pOut
++ = ( q31_t
) ( acc1
<< 1 );
378 * pOut
++ = ( q31_t
) ( acc2
<< 1 );
379 * pOut
++ = ( q31_t
) ( acc3
<< 1 );
381 /* Increment the pointer pIn1 index, count by 4 */
384 /* Update the inputA and inputB pointers for next MAC calculation */
388 /* Decrement the loop counter */
392 /* If the blockSize2 is not a multiple of 4, compute any remaining output samples here.
393 ** No loop unrolling is used. */
394 blkCnt
= blockSize2
% 0x4 u
;
398 /* Accumulator is made zero for every iteration */
401 /* Apply loop unrolling and compute 4 MACs simultaneously. */
404 /* First part of the processing with loop unrolling. Compute 4 MACs at a time.
405 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
408 /* Perform the multiply-accumulates */
409 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
410 (( q63_t
) * px
++ * (* py
--))) >> 32 );
411 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
412 (( q63_t
) * px
++ * (* py
--))) >> 32 );
413 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
414 (( q63_t
) * px
++ * (* py
--))) >> 32 );
415 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
416 (( q63_t
) * px
++ * (* py
--))) >> 32 );
418 /* Decrement the loop counter */
422 /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
423 ** No loop unrolling is used. */
428 /* Perform the multiply-accumulate */
429 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
430 (( q63_t
) * px
++ * (* py
--))) >> 32 );
432 /* Decrement the loop counter */
436 /* Store the result in the accumulator in the destination buffer. */
439 /* Increment the MAC count */
442 /* Update the inputA and inputB pointers for next MAC calculation */
446 /* Decrement the loop counter */
452 /* If the srcBLen is not a multiple of 4,
453 * the blockSize2 loop cannot be unrolled by 4 */
458 /* Accumulator is made zero for every iteration */
461 /* srcBLen number of MACS should be performed */
466 /* Perform the multiply-accumulate */
467 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
468 (( q63_t
) * px
++ * (* py
--))) >> 32 );
470 /* Decrement the loop counter */
474 /* Store the result in the accumulator in the destination buffer. */
477 /* Increment the MAC count */
480 /* Update the inputA and inputB pointers for next MAC calculation */
484 /* Decrement the loop counter */
490 /* --------------------------
491 * Initializations of stage3
492 * -------------------------*/
494 /* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
495 * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
497 * sum += x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
498 * sum += x[srcALen-1] * y[srcBLen-1]
501 /* In this stage the MAC operations are decreased by 1 for every iteration.
502 The blockSize3 variable holds the number of MAC operations performed */
504 /* Working pointer of inputA */
505 pSrc1
= ( pIn1
+ srcALen
) - ( srcBLen
- 1u );
508 /* Working pointer of inputB */
509 pSrc2
= pIn2
+ ( srcBLen
- 1u );
512 /* -------------------
514 * ------------------*/
516 while ( blockSize3
> 0u )
518 /* Accumulator is made zero for every iteration */
521 /* Apply loop unrolling and compute 4 MACs simultaneously. */
522 k
= blockSize3
>> 2u ;
524 /* First part of the processing with loop unrolling. Compute 4 MACs at a time.
525 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
528 /* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */
529 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
530 (( q63_t
) * px
++ * (* py
--))) >> 32 );
532 /* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */
533 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
534 (( q63_t
) * px
++ * (* py
--))) >> 32 );
536 /* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */
537 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
538 (( q63_t
) * px
++ * (* py
--))) >> 32 );
540 /* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */
541 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
542 (( q63_t
) * px
++ * (* py
--))) >> 32 );
544 /* Decrement the loop counter */
548 /* If the blockSize3 is not a multiple of 4, compute any remaining MACs here.
549 ** No loop unrolling is used. */
550 k
= blockSize3
% 0x4 u
;
554 /* Perform the multiply-accumulate */
555 sum
= ( q31_t
) (((( q63_t
) sum
<< 32 ) +
556 (( q63_t
) * px
++ * (* py
--))) >> 32 );
558 /* Decrement the loop counter */
562 /* Store the result in the accumulator in the destination buffer. */
565 /* Update the inputA and inputB pointers for next MAC calculation */
569 /* Decrement the loop counter */
576 * @} end of Conv group