1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_q31_to_q15.c
4 * Description: Converts the elements of the Q31 vector to Q15 vector
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/support_functions.h"
30
31 /**
32 @ingroup groupSupport
33 */
34
35 /**
36 @addtogroup q31_to_x
37 @{
38 */
39
40 /**
41 @brief Converts the elements of the Q31 vector to Q15 vector.
42 @param[in] pSrc points to the Q31 input vector
43 @param[out] pDst points to the Q15 output vector
44 @param[in] blockSize number of samples in each vector
45 @return none
46
47 @par Details
48 The equation used for the conversion process is:
49 <pre>
50 pDst[n] = (q15_t) pSrc[n] >> 16; 0 <= n < blockSize.
51 </pre>
52 */
53 #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
arm_q31_to_q15(const q31_t * pSrc,q15_t * pDst,uint32_t blockSize)54 void arm_q31_to_q15(
55 const q31_t * pSrc,
56 q15_t * pDst,
57 uint32_t blockSize)
58 {
59 uint32_t blkCnt; /* loop counters */
60 q31x4x2_t tmp;
61 q15x8_t vecDst;
62 q31_t const *pSrcVec;
63
64
65 pSrcVec = (q31_t const *) pSrc;
66 blkCnt = blockSize >> 3;
67 while (blkCnt > 0U)
68 {
69 /* C = (q15_t) A >> 16 */
70 /* convert from q31 to q15 and then store the results in the destination buffer */
71 tmp = vld2q(pSrcVec);
72 pSrcVec += 8;
73 vecDst = vshrnbq_n_s32(vecDst, tmp.val[0], 16);
74 vecDst = vshrntq_n_s32(vecDst, tmp.val[1], 16);
75 vst1q(pDst, vecDst);
76 pDst += 8;
77 /*
78 * Decrement the blockSize loop counter
79 */
80 blkCnt--;
81 }
82
83 /*
84 * tail
85 */
86 blkCnt = blockSize & 7;
87 while (blkCnt > 0U)
88 {
89 /* C = (q15_t) (A >> 16) */
90
91 /* Convert from q31 to q15 and store result in destination buffer */
92 *pDst++ = (q15_t) (*pSrcVec++ >> 16);
93
94 /* Decrement loop counter */
95 blkCnt--;
96 }
97 }
98
99 #else
arm_q31_to_q15(const q31_t * pSrc,q15_t * pDst,uint32_t blockSize)100 void arm_q31_to_q15(
101 const q31_t * pSrc,
102 q15_t * pDst,
103 uint32_t blockSize)
104 {
105 uint32_t blkCnt; /* Loop counter */
106 const q31_t *pIn = pSrc; /* Source pointer */
107
108 #if defined (ARM_MATH_LOOPUNROLL) && defined (ARM_MATH_DSP)
109 q31_t in1, in2, in3, in4;
110 q31_t out1, out2;
111 #endif
112
113 #if defined (ARM_MATH_LOOPUNROLL)
114
115 /* Loop unrolling: Compute 4 outputs at a time */
116 blkCnt = blockSize >> 2U;
117
118 while (blkCnt > 0U)
119 {
120 /* C = (q15_t) (A >> 16) */
121
122 /* Convert from q31 to q15 and store result in destination buffer */
123 #if defined (ARM_MATH_DSP)
124
125 in1 = *pIn++;
126 in2 = *pIn++;
127 in3 = *pIn++;
128 in4 = *pIn++;
129
130 /* pack two higher 16-bit values from two 32-bit values */
131 #ifndef ARM_MATH_BIG_ENDIAN
132 out1 = __PKHTB(in2, in1, 16);
133 out2 = __PKHTB(in4, in3, 16);
134 #else
135 out1 = __PKHTB(in1, in2, 16);
136 out2 = __PKHTB(in3, in4, 16);
137 #endif /* #ifdef ARM_MATH_BIG_ENDIAN */
138
139 write_q15x2_ia (&pDst, out1);
140 write_q15x2_ia (&pDst, out2);
141
142 #else
143
144 *pDst++ = (q15_t) (*pIn++ >> 16);
145 *pDst++ = (q15_t) (*pIn++ >> 16);
146 *pDst++ = (q15_t) (*pIn++ >> 16);
147 *pDst++ = (q15_t) (*pIn++ >> 16);
148
149 #endif /* #if defined (ARM_MATH_DSP) */
150
151 /* Decrement loop counter */
152 blkCnt--;
153 }
154
155 /* Loop unrolling: Compute remaining outputs */
156 blkCnt = blockSize % 0x4U;
157
158 #else
159
160 /* Initialize blkCnt with number of samples */
161 blkCnt = blockSize;
162
163 #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
164
165 while (blkCnt > 0U)
166 {
167 /* C = (q15_t) (A >> 16) */
168
169 /* Convert from q31 to q15 and store result in destination buffer */
170 *pDst++ = (q15_t) (*pIn++ >> 16);
171
172 /* Decrement loop counter */
173 blkCnt--;
174 }
175
176 }
177 #endif /* defined(ARM_MATH_MVEI) */
178
179 /**
180 @} end of q31_to_x group
181 */
182