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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_sub_q15.c
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9 *
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10 * Description: Q15 vector subtraction.
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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
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41 #include "arm_math.h"
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42
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43 /**
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44 * @ingroup groupMath
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45 */
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46
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47 /**
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48 * @addtogroup BasicSub
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49 * @{
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50 */
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51
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52 /**
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53 * @brief Q15 vector subtraction.
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54 * @param[in] *pSrcA points to the first input vector
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55 * @param[in] *pSrcB points to the second input vector
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56 * @param[out] *pDst points to the output vector
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57 * @param[in] blockSize number of samples in each vector
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58 * @return none.
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59 *
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60 * <b>Scaling and Overflow Behavior:</b>
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61 * \par
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62 * The function uses saturating arithmetic.
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63 * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
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64 */
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65
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66 void arm_sub_q15(
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67 q15_t * pSrcA,
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68 q15_t * pSrcB,
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69 q15_t * pDst,
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70 uint32_t blockSize)
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71 {
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72 uint32_t blkCnt; /* loop counter */
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73
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74
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75 #ifndef ARM_MATH_CM0_FAMILY
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76
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77 /* Run the below code for Cortex-M4 and Cortex-M3 */
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78 q31_t inA1, inA2;
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79 q31_t inB1, inB2;
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80
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81 /*loop Unrolling */
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82 blkCnt = blockSize >> 2u;
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83
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84 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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85 ** a second loop below computes the remaining 1 to 3 samples. */
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86 while(blkCnt > 0u)
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87 {
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88 /* C = A - B */
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89 /* Subtract and then store the results in the destination buffer two samples at a time. */
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90 inA1 = *__SIMD32(pSrcA)++;
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91 inA2 = *__SIMD32(pSrcA)++;
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92 inB1 = *__SIMD32(pSrcB)++;
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93 inB2 = *__SIMD32(pSrcB)++;
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94
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95 *__SIMD32(pDst)++ = __QSUB16(inA1, inB1);
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96 *__SIMD32(pDst)++ = __QSUB16(inA2, inB2);
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97
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98 /* Decrement the loop counter */
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99 blkCnt--;
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100 }
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101
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102 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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103 ** No loop unrolling is used. */
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104 blkCnt = blockSize % 0x4u;
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105
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106 while(blkCnt > 0u)
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107 {
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108 /* C = A - B */
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109 /* Subtract and then store the result in the destination buffer. */
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110 *pDst++ = (q15_t) __QSUB16(*pSrcA++, *pSrcB++);
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111
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112 /* Decrement the loop counter */
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113 blkCnt--;
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114 }
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115
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116 #else
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117
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118 /* Run the below code for Cortex-M0 */
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119
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120 /* Initialize blkCnt with number of samples */
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121 blkCnt = blockSize;
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122
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123 while(blkCnt > 0u)
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124 {
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125 /* C = A - B */
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126 /* Subtract and then store the result in the destination buffer. */
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127 *pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
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128
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129 /* Decrement the loop counter */
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130 blkCnt--;
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131 }
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132
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133 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
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134
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135
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136 }
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137
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138 /**
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139 * @} end of BasicSub group
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140 */
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