Diff: FilteringFunctions/arm_fir_fast_q15.c

Revision:

0:3d9c67d97d6f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FilteringFunctions/arm_fir_fast_q15.c	Mon Jul 28 15:03:15 2014 +0000
@@ -0,0 +1,345 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
+*    
+* $Date:        12. March 2014
+* $Revision: 	V1.4.3
+*    
+* 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    
+ */