+++ /dev/null
-/* ----------------------------------------------------------------------
-* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
-*
-* $Date: 17. January 2013
-* $Revision: V1.4.1
-*
-* Project: CMSIS DSP Library
-* Title: arm_fir_fast_q15.c
-*
-* Description: Q15 Fast FIR filter processing function.
-*
-* Target Processor: Cortex-M4/Cortex-M3
-*
-* Redistribution and use in source and binary forms, with or without
-* modification, are permitted provided that the following conditions
-* are met:
-* - Redistributions of source code must retain the above copyright
-* notice, this list of conditions and the following disclaimer.
-* - Redistributions in binary form must reproduce the above copyright
-* notice, this list of conditions and the following disclaimer in
-* the documentation and/or other materials provided with the
-* distribution.
-* - Neither the name of ARM LIMITED nor the names of its contributors
-* may be used to endorse or promote products derived from this
-* software without specific prior written permission.
-*
-* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
-* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
-* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
-* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
-* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
-* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
-* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
-* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
-* POSSIBILITY OF SUCH DAMAGE.
-* -------------------------------------------------------------------- */
-
-#include "arm_math.h"
-
-/**
- * @ingroup groupFilters
- */
-
-/**
- * @addtogroup FIR
- * @{
- */
-
-/**
- * @param[in] *S points to an instance of the Q15 FIR filter structure.
- * @param[in] *pSrc points to the block of input data.
- * @param[out] *pDst points to the block of output data.
- * @param[in] blockSize number of samples to process per call.
- * @return none.
- *
- * <b>Scaling and Overflow Behavior:</b>
- * \par
- * This fast version uses a 32-bit accumulator with 2.30 format.
- * The accumulator maintains full precision of the intermediate multiplication results but provides only a single guard bit.
- * Thus, if the accumulator result overflows it wraps around and distorts the result.
- * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits.
- * The 2.30 accumulator is then truncated to 2.15 format and saturated to yield the 1.15 result.
- *
- * \par
- * Refer to the function <code>arm_fir_q15()</code> for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion. Both the slow and the fast versions use the same instance structure.
- * Use the function <code>arm_fir_init_q15()</code> to initialize the filter structure.
- */
-
-void arm_fir_fast_q15(
- const arm_fir_instance_q15 * S,
- q15_t * pSrc,
- q15_t * pDst,
- uint32_t blockSize)
-{
- q15_t *pState = S->pState; /* State pointer */
- q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
- q15_t *pStateCurnt; /* Points to the current sample of the state */
- q31_t acc0, acc1, acc2, acc3; /* Accumulators */
- q15_t *pb; /* Temporary pointer for coefficient buffer */
- q15_t *px; /* Temporary q31 pointer for SIMD state buffer accesses */
- q31_t x0, x1, x2, c0; /* Temporary variables to hold SIMD state and coefficient values */
- uint32_t numTaps = S->numTaps; /* Number of taps in the filter */
- uint32_t tapCnt, blkCnt; /* Loop counters */
-
-
- /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
- /* pStateCurnt points to the location where the new input data should be written */
- pStateCurnt = &(S->pState[(numTaps - 1u)]);
-
- /* Apply loop unrolling and compute 4 output values simultaneously.
- * The variables acc0 ... acc3 hold output values that are being computed:
- *
- * acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]
- * acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]
- * acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]
- * acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3]
- */
-
- blkCnt = blockSize >> 2;
-
- /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
- ** a second loop below computes the remaining 1 to 3 samples. */
- while(blkCnt > 0u)
- {
- /* Copy four new input samples into the state buffer.
- ** Use 32-bit SIMD to move the 16-bit data. Only requires two copies. */
- *pStateCurnt++ = *pSrc++;
- *pStateCurnt++ = *pSrc++;
- *pStateCurnt++ = *pSrc++;
- *pStateCurnt++ = *pSrc++;
-
-
- /* Set all accumulators to zero */
- acc0 = 0;
- acc1 = 0;
- acc2 = 0;
- acc3 = 0;
-
- /* Typecast q15_t pointer to q31_t pointer for state reading in q31_t */
- px = pState;
-
- /* Typecast q15_t pointer to q31_t pointer for coefficient reading in q31_t */
- pb = pCoeffs;
-
- /* Read the first two samples from the state buffer: x[n-N], x[n-N-1] */
- x0 = *__SIMD32(px)++;
-
- /* Read the third and forth samples from the state buffer: x[n-N-2], x[n-N-3] */
- x2 = *__SIMD32(px)++;
-
- /* Loop over the number of taps. Unroll by a factor of 4.
- ** Repeat until we've computed numTaps-(numTaps%4) coefficients. */
- tapCnt = numTaps >> 2;
-
- while(tapCnt > 0)
- {
- /* Read the first two coefficients using SIMD: b[N] and b[N-1] coefficients */
- c0 = *__SIMD32(pb)++;
-
- /* acc0 += b[N] * x[n-N] + b[N-1] * x[n-N-1] */
- acc0 = __SMLAD(x0, c0, acc0);
-
- /* acc2 += b[N] * x[n-N-2] + b[N-1] * x[n-N-3] */
- acc2 = __SMLAD(x2, c0, acc2);
-
- /* pack x[n-N-1] and x[n-N-2] */
-#ifndef ARM_MATH_BIG_ENDIAN
- x1 = __PKHBT(x2, x0, 0);
-#else
- x1 = __PKHBT(x0, x2, 0);
-#endif
-
- /* Read state x[n-N-4], x[n-N-5] */
- x0 = _SIMD32_OFFSET(px);
-
- /* acc1 += b[N] * x[n-N-1] + b[N-1] * x[n-N-2] */
- acc1 = __SMLADX(x1, c0, acc1);
-
- /* pack x[n-N-3] and x[n-N-4] */
-#ifndef ARM_MATH_BIG_ENDIAN
- x1 = __PKHBT(x0, x2, 0);
-#else
- x1 = __PKHBT(x2, x0, 0);
-#endif
-
- /* acc3 += b[N] * x[n-N-3] + b[N-1] * x[n-N-4] */
- acc3 = __SMLADX(x1, c0, acc3);
-
- /* Read coefficients b[N-2], b[N-3] */
- c0 = *__SIMD32(pb)++;
-
- /* acc0 += b[N-2] * x[n-N-2] + b[N-3] * x[n-N-3] */
- acc0 = __SMLAD(x2, c0, acc0);
-
- /* Read state x[n-N-6], x[n-N-7] with offset */
- x2 = _SIMD32_OFFSET(px + 2u);
-
- /* acc2 += b[N-2] * x[n-N-4] + b[N-3] * x[n-N-5] */
- acc2 = __SMLAD(x0, c0, acc2);
-
- /* acc1 += b[N-2] * x[n-N-3] + b[N-3] * x[n-N-4] */
- acc1 = __SMLADX(x1, c0, acc1);
-
- /* pack x[n-N-5] and x[n-N-6] */
-#ifndef ARM_MATH_BIG_ENDIAN
- x1 = __PKHBT(x2, x0, 0);
-#else
- x1 = __PKHBT(x0, x2, 0);
-#endif
-
- /* acc3 += b[N-2] * x[n-N-5] + b[N-3] * x[n-N-6] */
- acc3 = __SMLADX(x1, c0, acc3);
-
- /* Update state pointer for next state reading */
- px += 4u;
-
- /* Decrement tap count */
- tapCnt--;
-
- }
-
- /* If the filter length is not a multiple of 4, compute the remaining filter taps.
- ** This is always be 2 taps since the filter length is even. */
- if((numTaps & 0x3u) != 0u)
- {
-
- /* Read last two coefficients */
- c0 = *__SIMD32(pb)++;
-
- /* Perform the multiply-accumulates */
- acc0 = __SMLAD(x0, c0, acc0);
- acc2 = __SMLAD(x2, c0, acc2);
-
- /* pack state variables */
-#ifndef ARM_MATH_BIG_ENDIAN
- x1 = __PKHBT(x2, x0, 0);
-#else
- x1 = __PKHBT(x0, x2, 0);
-#endif
-
- /* Read last state variables */
- x0 = *__SIMD32(px);
-
- /* Perform the multiply-accumulates */
- acc1 = __SMLADX(x1, c0, acc1);
-
- /* pack state variables */
-#ifndef ARM_MATH_BIG_ENDIAN
- x1 = __PKHBT(x0, x2, 0);
-#else
- x1 = __PKHBT(x2, x0, 0);
-#endif
-
- /* Perform the multiply-accumulates */
- acc3 = __SMLADX(x1, c0, acc3);
- }
-
- /* The results in the 4 accumulators are in 2.30 format. Convert to 1.15 with saturation.
- ** Then store the 4 outputs in the destination buffer. */
-
-#ifndef ARM_MATH_BIG_ENDIAN
-
- *__SIMD32(pDst)++ =
- __PKHBT(__SSAT((acc0 >> 15), 16), __SSAT((acc1 >> 15), 16), 16);
-
- *__SIMD32(pDst)++ =
- __PKHBT(__SSAT((acc2 >> 15), 16), __SSAT((acc3 >> 15), 16), 16);
-
-#else
-
- *__SIMD32(pDst)++ =
- __PKHBT(__SSAT((acc1 >> 15), 16), __SSAT((acc0 >> 15), 16), 16);
-
- *__SIMD32(pDst)++ =
- __PKHBT(__SSAT((acc3 >> 15), 16), __SSAT((acc2 >> 15), 16), 16);
-
-
-#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
-
- /* Advance the state pointer by 4 to process the next group of 4 samples */
- pState = pState + 4u;
-
- /* Decrement the loop counter */
- blkCnt--;
- }
-
- /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
- ** No loop unrolling is used. */
- blkCnt = blockSize % 0x4u;
- while(blkCnt > 0u)
- {
- /* Copy two samples into state buffer */
- *pStateCurnt++ = *pSrc++;
-
- /* Set the accumulator to zero */
- acc0 = 0;
-
- /* Use SIMD to hold states and coefficients */
- px = pState;
- pb = pCoeffs;
-
- tapCnt = numTaps >> 1u;
-
- do
- {
-
- acc0 += (q31_t) * px++ * *pb++;
- acc0 += (q31_t) * px++ * *pb++;
-
- tapCnt--;
- }
- while(tapCnt > 0u);
-
- /* The result is in 2.30 format. Convert to 1.15 with saturation.
- ** Then store the output in the destination buffer. */
- *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
-
- /* Advance state pointer by 1 for the next sample */
- pState = pState + 1u;
-
- /* Decrement the loop counter */
- blkCnt--;
- }
-
- /* Processing is complete.
- ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
- ** This prepares the state buffer for the next function call. */
-
- /* Points to the start of the state buffer */
- pStateCurnt = S->pState;
-
- /* Calculation of count for copying integer writes */
- tapCnt = (numTaps - 1u) >> 2;
-
- while(tapCnt > 0u)
- {
- *pStateCurnt++ = *pState++;
- *pStateCurnt++ = *pState++;
- *pStateCurnt++ = *pState++;
- *pStateCurnt++ = *pState++;
-
- tapCnt--;
-
- }
-
- /* Calculation of count for remaining q15_t data */
- tapCnt = (numTaps - 1u) % 0x4u;
-
- /* copy remaining data */
- while(tapCnt > 0u)
- {
- *pStateCurnt++ = *pState++;
-
- /* Decrement the loop counter */
- tapCnt--;
- }
-
-}
-
-/**
- * @} end of FIR group
- */
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