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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_shift_q31.c
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9 *
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10 * Description: Shifts the elements of a Q31 vector by a specified number of bits.
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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 * @defgroup shift Vector Shift
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48 *
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49 * Shifts the elements of a fixed-point vector by a specified number of bits.
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50 * There are separate functions for Q7, Q15, and Q31 data types.
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51 * The underlying algorithm used is:
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52 *
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53 * <pre>
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54 * pDst[n] = pSrc[n] << shift, 0 <= n < blockSize.
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55 * </pre>
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56 *
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57 * If <code>shift</code> is positive then the elements of the vector are shifted to the left.
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58 * If <code>shift</code> is negative then the elements of the vector are shifted to the right.
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59 *
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60 * The functions support in-place computation allowing the source and destination
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61 * pointers to reference the same memory buffer.
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62 */
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63
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64 /**
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65 * @addtogroup shift
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66 * @{
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67 */
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68
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69 /**
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70 * @brief Shifts the elements of a Q31 vector a specified number of bits.
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71 * @param[in] *pSrc points to the input vector
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72 * @param[in] shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right.
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73 * @param[out] *pDst points to the output vector
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74 * @param[in] blockSize number of samples in the vector
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75 * @return none.
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76 *
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77 *
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78 * <b>Scaling and Overflow Behavior:</b>
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79 * \par
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80 * The function uses saturating arithmetic.
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81 * Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated.
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82 */
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83
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84 void arm_shift_q31(
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85 q31_t * pSrc,
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86 int8_t shiftBits,
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87 q31_t * pDst,
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88 uint32_t blockSize)
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89 {
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90 uint32_t blkCnt; /* loop counter */
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91 uint8_t sign = (shiftBits & 0x80); /* Sign of shiftBits */
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92
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93 #ifndef ARM_MATH_CM0_FAMILY
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94
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95 q31_t in1, in2, in3, in4; /* Temporary input variables */
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96 q31_t out1, out2, out3, out4; /* Temporary output variables */
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97
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98 /*loop Unrolling */
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99 blkCnt = blockSize >> 2u;
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100
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101
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102 if(sign == 0u)
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103 {
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104 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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105 ** a second loop below computes the remaining 1 to 3 samples. */
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106 while(blkCnt > 0u)
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107 {
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108 /* C = A << shiftBits */
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109 /* Shift the input and then store the results in the destination buffer. */
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110 in1 = *pSrc;
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111 in2 = *(pSrc + 1);
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112 out1 = in1 << shiftBits;
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113 in3 = *(pSrc + 2);
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114 out2 = in2 << shiftBits;
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115 in4 = *(pSrc + 3);
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116 if(in1 != (out1 >> shiftBits))
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117 out1 = 0x7FFFFFFF ^ (in1 >> 31);
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118
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119 if(in2 != (out2 >> shiftBits))
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120 out2 = 0x7FFFFFFF ^ (in2 >> 31);
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121
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122 *pDst = out1;
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123 out3 = in3 << shiftBits;
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124 *(pDst + 1) = out2;
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125 out4 = in4 << shiftBits;
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126
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127 if(in3 != (out3 >> shiftBits))
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128 out3 = 0x7FFFFFFF ^ (in3 >> 31);
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129
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130 if(in4 != (out4 >> shiftBits))
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131 out4 = 0x7FFFFFFF ^ (in4 >> 31);
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132
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133 *(pDst + 2) = out3;
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134 *(pDst + 3) = out4;
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135
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136 /* Update destination pointer to process next sampels */
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137 pSrc += 4u;
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138 pDst += 4u;
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139
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140 /* Decrement the loop counter */
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141 blkCnt--;
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142 }
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143 }
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144 else
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145 {
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146
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147 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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148 ** a second loop below computes the remaining 1 to 3 samples. */
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149 while(blkCnt > 0u)
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150 {
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151 /* C = A >> shiftBits */
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152 /* Shift the input and then store the results in the destination buffer. */
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153 in1 = *pSrc;
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154 in2 = *(pSrc + 1);
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155 in3 = *(pSrc + 2);
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156 in4 = *(pSrc + 3);
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157
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158 *pDst = (in1 >> -shiftBits);
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159 *(pDst + 1) = (in2 >> -shiftBits);
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160 *(pDst + 2) = (in3 >> -shiftBits);
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161 *(pDst + 3) = (in4 >> -shiftBits);
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162
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163
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164 pSrc += 4u;
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165 pDst += 4u;
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166
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167 blkCnt--;
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168 }
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169
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170 }
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171
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172 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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173 ** No loop unrolling is used. */
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174 blkCnt = blockSize % 0x4u;
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175
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176 #else
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177
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178 /* Run the below code for Cortex-M0 */
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179
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180
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181 /* Initialize blkCnt with number of samples */
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182 blkCnt = blockSize;
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183
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184 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
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185
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186
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187 while(blkCnt > 0u)
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188 {
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189 /* C = A (>> or <<) shiftBits */
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190 /* Shift the input and then store the result in the destination buffer. */
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191 *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
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192 (*pSrc++ >> -shiftBits);
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193
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194 /* Decrement the loop counter */
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195 blkCnt--;
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196 }
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197
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198
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199 }
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200
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201 /**
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202 * @} end of shift group
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203 */
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