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1 /* ----------------------------------------------------------------------
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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_negate_q15.c
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9 *
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10 * Description: Negates Q15 vectors.
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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 #include "arm_math.h"
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41
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42 /**
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43 * @ingroup groupMath
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44 */
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45
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46 /**
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47 * @addtogroup negate
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48 * @{
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49 */
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50
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51 /**
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52 * @brief Negates the elements of a Q15 vector.
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53 * @param[in] *pSrc points to the input vector
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54 * @param[out] *pDst points to the output vector
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55 * @param[in] blockSize number of samples in the vector
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56 * @return none.
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57 *
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58 * \par Conditions for optimum performance
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59 * Input and output buffers should be aligned by 32-bit
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60 *
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61 *
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62 * <b>Scaling and Overflow Behavior:</b>
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63 * \par
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64 * The function uses saturating arithmetic.
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65 * The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.
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66 */
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67
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68 void arm_negate_q15(
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69 q15_t * pSrc,
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70 q15_t * pDst,
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71 uint32_t blockSize)
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72 {
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73 uint32_t blkCnt; /* loop counter */
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74 q15_t in;
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75
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76 #ifndef ARM_MATH_CM0_FAMILY
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77
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78 /* Run the below code for Cortex-M4 and Cortex-M3 */
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79
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80 q31_t in1, in2; /* Temporary variables */
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81
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82
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83 /*loop Unrolling */
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84 blkCnt = blockSize >> 2u;
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85
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86 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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87 ** a second loop below computes the remaining 1 to 3 samples. */
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88 while(blkCnt > 0u)
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89 {
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90 /* C = -A */
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91 /* Read two inputs at a time */
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92 in1 = _SIMD32_OFFSET(pSrc);
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93 in2 = _SIMD32_OFFSET(pSrc + 2);
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94
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95 /* negate two samples at a time */
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96 in1 = __QSUB16(0, in1);
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97
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98 /* negate two samples at a time */
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99 in2 = __QSUB16(0, in2);
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100
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101 /* store the result to destination 2 samples at a time */
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102 _SIMD32_OFFSET(pDst) = in1;
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103 /* store the result to destination 2 samples at a time */
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104 _SIMD32_OFFSET(pDst + 2) = in2;
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105
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106
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107 /* update pointers to process next samples */
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108 pSrc += 4u;
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109 pDst += 4u;
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110
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111 /* Decrement the loop counter */
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112 blkCnt--;
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113 }
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114
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115 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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116 ** No loop unrolling is used. */
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117 blkCnt = blockSize % 0x4u;
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118
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119 #else
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120
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121 /* Run the below code for Cortex-M0 */
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122
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123 /* Initialize blkCnt with number of samples */
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124 blkCnt = blockSize;
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125
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126 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
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127
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128 while(blkCnt > 0u)
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129 {
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130 /* C = -A */
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131 /* Negate and then store the result in the destination buffer. */
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132 in = *pSrc++;
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133 *pDst++ = (in == (q15_t) 0x8000) ? 0x7fff : -in;
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134
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135 /* Decrement the loop counter */
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136 blkCnt--;
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137 }
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138 }
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139
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140 /**
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141 * @} end of negate group
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142 */
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