1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
4 * $Date: 17. January 2013
7 * Project: CMSIS DSP Library
8 * Title: arm_scale_q15.c
10 * Description: Multiplies a Q15 vector by a scalar.
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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15 * modification, are permitted provided that the following conditions
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27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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39 * -------------------------------------------------------------------- */
53 * @brief Multiplies a Q15 vector by a scalar.
54 * @param[in] *pSrc points to the input vector
55 * @param[in] scaleFract fractional portion of the scale value
56 * @param[in] shift number of bits to shift the result by
57 * @param[out] *pDst points to the output vector
58 * @param[in] blockSize number of samples in the vector
61 * <b>Scaling and Overflow Behavior:</b>
63 * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.15 format.
64 * These are multiplied to yield a 2.30 intermediate result and this is shifted with saturation to 1.15 format.
75 int8_t kShift = 15 - shift; /* shift to apply after scaling */
76 uint32_t blkCnt; /* loop counter */
78 #ifndef ARM_MATH_CM0_FAMILY
80 /* Run the below code for Cortex-M4 and Cortex-M3 */
81 q15_t in1, in2, in3, in4;
82 q31_t inA1, inA2; /* Temporary variables */
83 q31_t out1, out2, out3, out4;
87 blkCnt = blockSize >> 2u;
89 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
90 ** a second loop below computes the remaining 1 to 3 samples. */
93 /* Reading 2 inputs from memory */
94 inA1 = *__SIMD32(pSrc)++;
95 inA2 = *__SIMD32(pSrc)++;
98 /* Scale the inputs and then store the 2 results in the destination buffer
99 * in single cycle by packing the outputs */
100 out1 = (q31_t) ((q15_t) (inA1 >> 16) * scaleFract);
101 out2 = (q31_t) ((q15_t) inA1 * scaleFract);
102 out3 = (q31_t) ((q15_t) (inA2 >> 16) * scaleFract);
103 out4 = (q31_t) ((q15_t) inA2 * scaleFract);
106 out1 = out1 >> kShift;
107 out2 = out2 >> kShift;
108 out3 = out3 >> kShift;
109 out4 = out4 >> kShift;
111 /* saturate the output */
112 in1 = (q15_t) (__SSAT(out1, 16));
113 in2 = (q15_t) (__SSAT(out2, 16));
114 in3 = (q15_t) (__SSAT(out3, 16));
115 in4 = (q15_t) (__SSAT(out4, 16));
117 /* store the result to destination */
118 *__SIMD32(pDst)++ = __PKHBT(in2, in1, 16);
119 *__SIMD32(pDst)++ = __PKHBT(in4, in3, 16);
121 /* Decrement the loop counter */
125 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
126 ** No loop unrolling is used. */
127 blkCnt = blockSize % 0x4u;
132 /* Scale the input and then store the result in the destination buffer. */
133 *pDst++ = (q15_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 16));
135 /* Decrement the loop counter */
141 /* Run the below code for Cortex-M0 */
143 /* Initialize blkCnt with number of samples */
149 /* Scale the input and then store the result in the destination buffer. */
150 *pDst++ = (q15_t) (__SSAT(((q31_t) * pSrc++ * scaleFract) >> kShift, 16));
152 /* Decrement the loop counter */
156 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
161 * @} end of scale group