/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_fir_q15.c
* Description: Q15 FIR filter processing function
*
* $Date: 27. January 2017
* $Revision: V.1.5.1
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup FIR
* @{
*/
/**
* @brief Processing function for the Q15 FIR filter.
* @param[in] *S points to an instance of the Q15 FIR 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.
*
*
* \par Restrictions
* If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
* In this case input, output, state buffers should be aligned by 32-bit
*
* Scaling and Overflow Behavior:
* \par
* The function is implemented using a 64-bit internal accumulator.
* Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
* The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
* There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
* After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
* Lastly, the accumulator is saturated to yield a result in 1.15 format.
*
* \par
* Refer to the function arm_fir_fast_q15() for a faster but less precise implementation of this function.
*/
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
#ifndef UNALIGNED_SUPPORT_DISABLE
void arm_fir_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 */
q15_t *px1; /* Temporary q15 pointer for state buffer */
q15_t *pb; /* Temporary pointer for coefficient buffer */
q31_t x0, x1, x2, x3, c0; /* Temporary variables to hold SIMD state and coefficient values */
q63_t acc0, acc1, acc2, acc3; /* Accumulators */
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. */
*__SIMD32(pStateCurnt)++ = *__SIMD32(pSrc)++;
*__SIMD32(pStateCurnt)++ = *__SIMD32(pSrc)++;
/* Set all accumulators to zero */
acc0 = 0;
acc1 = 0;
acc2 = 0;
acc3 = 0;
/* Initialize state pointer of type q15 */
px1 = pState;
/* Initialize coeff pointer of type q31 */
pb = pCoeffs;
/* Read the first two samples from the state buffer: x[n-N], x[n-N-1] */
x0 = _SIMD32_OFFSET(px1);
/* Read the third and forth samples from the state buffer: x[n-N-1], x[n-N-2] */
x1 = _SIMD32_OFFSET(px1 + 1U);
px1 += 2U;
/* Loop over the number of taps. Unroll by a factor of 4.
** Repeat until we've computed numTaps-4 coefficients. */
tapCnt = numTaps >> 2;
while (tapCnt > 0U)
{
/* 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 = __SMLALD(x0, c0, acc0);
/* acc1 += b[N] * x[n-N-1] + b[N-1] * x[n-N-2] */
acc1 = __SMLALD(x1, c0, acc1);
/* Read state x[n-N-2], x[n-N-3] */
x2 = _SIMD32_OFFSET(px1);
/* Read state x[n-N-3], x[n-N-4] */
x3 = _SIMD32_OFFSET(px1 + 1U);
/* acc2 += b[N] * x[n-N-2] + b[N-1] * x[n-N-3] */
acc2 = __SMLALD(x2, c0, acc2);
/* acc3 += b[N] * x[n-N-3] + b[N-1] * x[n-N-4] */
acc3 = __SMLALD(x3, 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 = __SMLALD(x2, c0, acc0);
/* acc1 += b[N-2] * x[n-N-3] + b[N-3] * x[n-N-4] */
acc1 = __SMLALD(x3, c0, acc1);
/* Read state x[n-N-4], x[n-N-5] */
x0 = _SIMD32_OFFSET(px1 + 2U);
/* Read state x[n-N-5], x[n-N-6] */
x1 = _SIMD32_OFFSET(px1 + 3U);
/* acc2 += b[N-2] * x[n-N-4] + b[N-3] * x[n-N-5] */
acc2 = __SMLALD(x0, c0, acc2);
/* acc3 += b[N-2] * x[n-N-5] + b[N-3] * x[n-N-6] */
acc3 = __SMLALD(x1, c0, acc3);
px1 += 4U;
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 2 coefficients */
c0 = *__SIMD32(pb)++;
/* Fetch 4 state variables */
x2 = _SIMD32_OFFSET(px1);
x3 = _SIMD32_OFFSET(px1 + 1U);
/* Perform the multiply-accumulates */
acc0 = __SMLALD(x0, c0, acc0);
px1 += 2U;
acc1 = __SMLALD(x1, c0, acc1);
acc2 = __SMLALD(x2, c0, acc2);
acc3 = __SMLALD(x3, 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 + 4;
/* 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;
/* Initialize state pointer of type q15 */
px1 = pState;
/* Initialize coeff pointer of type q31 */
pb = pCoeffs;
tapCnt = numTaps >> 1;
do
{
c0 = *__SIMD32(pb)++;
x0 = *__SIMD32(px1)++;
acc0 = __SMLALD(x0, c0, acc0);
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 + 1;
/* 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)
{
/* Copy state values to start of state buffer */
*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
*__SIMD32(pStateCurnt)++ = *__SIMD32(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--;
}
}
#else /* UNALIGNED_SUPPORT_DISABLE */
void arm_fir_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 */
q63_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 = __SMLALD(x0, c0, acc0);
/* acc2 += b[N] * x[n-N-2] + b[N-1] * x[n-N-3] */
acc2 = __SMLALD(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 = __SMLALDX(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 = __SMLALDX(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 = __SMLALD(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 = __SMLALD(x0, c0, acc2);
/* acc1 += b[N-2] * x[n-N-3] + b[N-3] * x[n-N-4] */
acc1 = __SMLALDX(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 = __SMLALDX(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 = __SMLALD(x0, c0, acc0);
acc2 = __SMLALD(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 = __SMLALDX(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 = __SMLALDX(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 + 4;
/* 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--;
}
}
#endif /* #ifndef UNALIGNED_SUPPORT_DISABLE */
#else /* ARM_MATH_CM0_FAMILY */
/* Run the below code for Cortex-M0 */
void arm_fir_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 */
q15_t *px; /* Temporary pointer for state buffer */
q15_t *pb; /* Temporary pointer for coefficient buffer */
q63_t acc; /* Accumulator */
uint32_t numTaps = S->numTaps; /* Number of nTaps in the filter */
uint32_t tapCnt, blkCnt; /* Loop counters */
/* S->pState buffer contains previous frame (numTaps - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = &(S->pState[(numTaps - 1U)]);
/* Initialize blkCnt with blockSize */
blkCnt = blockSize;
while (blkCnt > 0U)
{
/* Copy one sample at a time into state buffer */
*pStateCurnt++ = *pSrc++;
/* Set the accumulator to zero */
acc = 0;
/* Initialize state pointer */
px = pState;
/* Initialize Coefficient pointer */
pb = pCoeffs;
tapCnt = numTaps;
/* Perform the multiply-accumulates */
do
{
/* acc = 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] */
acc += (q31_t) * px++ * *pb++;
tapCnt--;
} while (tapCnt > 0U);
/* The result is in 2.30 format. Convert to 1.15
** Then store the output in the destination buffer. */
*pDst++ = (q15_t) __SSAT((acc >> 15U), 16);
/* Advance state pointer by 1 for the next sample */
pState = pState + 1;
/* Decrement the samples 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;
/* Copy numTaps number of values */
tapCnt = (numTaps - 1U);
/* copy data */
while (tapCnt > 0U)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
}
#endif /* #if defined (ARM_MATH_DSP) */
/**
* @} end of FIR group
*/