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| 2 | mjames | 1 | /* ---------------------------------------------------------------------------- |
| 2 | * Copyright (C) 2010-2014 ARM Limited. All rights reserved. |
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| 3 | * |
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| 4 | * $Date: 19. March 2015 |
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| 5 | * $Revision: V.1.4.5 |
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| 6 | * |
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| 7 | * Project: CMSIS DSP Library |
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| 8 | * Title: arm_q31_to_q15.c |
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| 9 | * |
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| 10 | * Description: Converts the elements of the Q31 vector to Q15 vector. |
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| 11 | * |
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| 12 | * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 |
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| 13 | * |
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| 14 | * Redistribution and use in source and binary forms, with or without |
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| 15 | * modification, are permitted provided that the following conditions |
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| 16 | * are met: |
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| 17 | * - Redistributions of source code must retain the above copyright |
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| 18 | * notice, this list of conditions and the following disclaimer. |
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| 19 | * - Redistributions in binary form must reproduce the above copyright |
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| 20 | * notice, this list of conditions and the following disclaimer in |
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| 21 | * the documentation and/or other materials provided with the |
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| 22 | * distribution. |
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| 23 | * - Neither the name of ARM LIMITED nor the names of its contributors |
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| 24 | * may be used to endorse or promote products derived from this |
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| 25 | * software without specific prior written permission. |
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| 26 | * |
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| 27 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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| 28 | * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| 29 | * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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| 30 | * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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| 31 | * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 32 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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| 33 | * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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| 34 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
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| 35 | * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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| 36 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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| 37 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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| 38 | * POSSIBILITY OF SUCH DAMAGE. |
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| 39 | * ---------------------------------------------------------------------------- */ |
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| 40 | |||
| 41 | #include "arm_math.h" |
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| 42 | |||
| 43 | /** |
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| 44 | * @ingroup groupSupport |
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| 45 | */ |
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| 46 | |||
| 47 | /** |
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| 48 | * @addtogroup q31_to_x |
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| 49 | * @{ |
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| 50 | */ |
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| 51 | |||
| 52 | /** |
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| 53 | * @brief Converts the elements of the Q31 vector to Q15 vector. |
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| 54 | * @param[in] *pSrc points to the Q31 input vector |
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| 55 | * @param[out] *pDst points to the Q15 output vector |
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| 56 | * @param[in] blockSize length of the input vector |
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| 57 | * @return none. |
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| 58 | * |
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| 59 | * \par Description: |
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| 60 | * |
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| 61 | * The equation used for the conversion process is: |
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| 62 | * |
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| 63 | * <pre> |
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| 64 | * pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize. |
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| 65 | * </pre> |
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| 66 | * |
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| 67 | */ |
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| 68 | |||
| 69 | |||
| 70 | void arm_q31_to_q15( |
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| 71 | q31_t * pSrc, |
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| 72 | q15_t * pDst, |
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| 73 | uint32_t blockSize) |
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| 74 | { |
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| 75 | q31_t *pIn = pSrc; /* Src pointer */ |
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| 76 | uint32_t blkCnt; /* loop counter */ |
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| 77 | |||
| 78 | #ifndef ARM_MATH_CM0_FAMILY |
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| 79 | |||
| 80 | /* Run the below code for Cortex-M4 and Cortex-M3 */ |
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| 81 | q31_t in1, in2, in3, in4; |
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| 82 | q31_t out1, out2; |
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| 83 | |||
| 84 | /*loop Unrolling */ |
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| 85 | blkCnt = blockSize >> 2u; |
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| 86 | |||
| 87 | /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
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| 88 | ** a second loop below computes the remaining 1 to 3 samples. */ |
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| 89 | while(blkCnt > 0u) |
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| 90 | { |
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| 91 | /* C = (q15_t) A >> 16 */ |
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| 92 | /* convert from q31 to q15 and then store the results in the destination buffer */ |
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| 93 | in1 = *pIn++; |
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| 94 | in2 = *pIn++; |
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| 95 | in3 = *pIn++; |
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| 96 | in4 = *pIn++; |
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| 97 | |||
| 98 | /* pack two higher 16-bit values from two 32-bit values */ |
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| 99 | #ifndef ARM_MATH_BIG_ENDIAN |
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| 100 | |||
| 101 | out1 = __PKHTB(in2, in1, 16); |
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| 102 | out2 = __PKHTB(in4, in3, 16); |
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| 103 | |||
| 104 | #else |
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| 105 | |||
| 106 | out1 = __PKHTB(in1, in2, 16); |
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| 107 | out2 = __PKHTB(in3, in4, 16); |
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| 108 | |||
| 109 | #endif // #ifdef ARM_MATH_BIG_ENDIAN |
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| 110 | |||
| 111 | *__SIMD32(pDst)++ = out1; |
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| 112 | *__SIMD32(pDst)++ = out2; |
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| 113 | |||
| 114 | /* Decrement the loop counter */ |
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| 115 | blkCnt--; |
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| 116 | } |
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| 117 | |||
| 118 | /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
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| 119 | ** No loop unrolling is used. */ |
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| 120 | blkCnt = blockSize % 0x4u; |
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| 121 | |||
| 122 | #else |
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| 123 | |||
| 124 | /* Run the below code for Cortex-M0 */ |
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| 125 | |||
| 126 | /* Loop over blockSize number of values */ |
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| 127 | blkCnt = blockSize; |
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| 128 | |||
| 129 | #endif /* #ifndef ARM_MATH_CM0_FAMILY */ |
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| 130 | |||
| 131 | while(blkCnt > 0u) |
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| 132 | { |
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| 133 | /* C = (q15_t) A >> 16 */ |
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| 134 | /* convert from q31 to q15 and then store the results in the destination buffer */ |
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| 135 | *pDst++ = (q15_t) (*pIn++ >> 16); |
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| 136 | |||
| 137 | /* Decrement the loop counter */ |
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| 138 | blkCnt--; |
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| 139 | } |
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| 140 | |||
| 141 | } |
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| 142 | |||
| 143 | /** |
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| 144 | * @} end of q31_to_x group |
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| 145 | */ |