arm_q31_to_q15.c
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00001 /* ---------------------------------------------------------------------------- 00002 * Copyright (C) 2011 ARM Limited. All rights reserved. 00003 * 00004 * $Date: 15. December 2011 00005 * $Revision: V2.0.0 00006 * 00007 * Project: Cortex-R DSP Library 00008 * Title: arm_q31_to_q15.c 00009 * 00010 * Description: Converts the elements of the Q31 vector to Q15 vector. 00011 * 00012 * Target Processor: Cortex-R4/R5 00013 * 00014 * Version 1.0.0 2011/03/08 00015 * Alpha release. 00016 * 00017 * Version 1.0.1 2011/09/30 00018 * Beta release. 00019 * 00020 * Version 2.0.0 2011/12/15 00021 * Final release. 00022 * 00023 * ---------------------------------------------------------------------------- */ 00024 #include "arm_math.h" 00025 00061 void arm_q31_to_q15( 00062 q31_t * pSrc, 00063 q15_t * pDst, 00064 uint32_t blockSize) 00065 { 00066 q31_t *pIn = pSrc; /* Src pointer */ 00067 uint32_t blkCnt; /* loop counter */ 00068 q31_t in1, in2, in3, in4; 00069 // q15_t out1, out2, out3, out4; 00070 q31_t out1, out2, out3, out4; 00071 00072 /*loop Unrolling */ 00073 blkCnt = blockSize >> 3u; 00074 00075 /* First part of the processing with loop unrolling. Compute 8 outputs at a time. 00076 ** a second loop below computes the remaining 1 to 7 samples. */ 00077 while(blkCnt > 0u) 00078 { 00079 /* C = (q15_t) A >> 16 */ 00080 /* convert from q31 to q15 and then store the results in the destination buffer */ 00081 /* read input samples */ 00082 in1 = pIn[0]; 00083 in2 = pIn[1]; 00084 in3 = pIn[2]; 00085 in4 = pIn[3]; 00086 00087 /* pack two higher 16-bit values from two 32-bit values */ 00088 #ifndef ARM_MATH_BIG_ENDIAN 00089 00090 out1 = __PKHTB(in2, in1, 16); 00091 out2 = __PKHTB(in4, in3, 16); 00092 00093 #else 00094 00095 out1 = __PKHTB(in1, in2, 16); 00096 out2 = __PKHTB(in3, in4, 16); 00097 00098 #endif // #ifdef ARM_MATH_BIG_ENDIAN 00099 00100 /* read input samples */ 00101 in1 = pIn[4]; 00102 in2 = pIn[5]; 00103 in3 = pIn[6]; 00104 in4 = pIn[7]; 00105 00106 /* pack two higher 16-bit values from two 32-bit values */ 00107 #ifndef ARM_MATH_BIG_ENDIAN 00108 00109 out3 = __PKHTB(in2, in1, 16); 00110 out4 = __PKHTB(in4, in3, 16); 00111 00112 #else 00113 00114 out3 = __PKHTB(in1, in2, 16); 00115 out4 = __PKHTB(in3, in4, 16); 00116 00117 #endif // #ifdef ARM_MATH_BIG_ENDIAN 00118 00119 /* store two samples at a time to destination */ 00120 _SIMD32_OFFSET(pDst) = out1; 00121 _SIMD32_OFFSET(pDst + 2) = out2; 00122 _SIMD32_OFFSET(pDst + 4) = out3; 00123 _SIMD32_OFFSET(pDst + 6) = out4; 00124 00125 /* incremnet source pointer */ 00126 pIn += 8u; 00127 /* increment destination pointer */ 00128 pDst += 8u; 00129 00130 /* Decrement the loop counter */ 00131 blkCnt--; 00132 } 00133 00134 /* If the blockSize is not a multiple of 8, compute any remaining output samples here. 00135 ** No loop unrolling is used. */ 00136 blkCnt = blockSize % 0x8u; 00137 00138 while(blkCnt > 0u) 00139 { 00140 /* C = (q15_t) A >> 16 */ 00141 /* convert from q31 to q15 and then store the results in the destination buffer */ 00142 *pDst++ = (q15_t) (*pIn++ >> 16); 00143 00144 blkCnt--; 00145 } 00146 00147 } 00148 00149 /* Decrement the loop counter */
