1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_q31_to_q7.c
4 * Description: Converts the elements of the Q31 vector to Q7 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 Q7 vector.
42 @param[in] pSrc points to the Q31 input vector
43 @param[out] pDst points to the Q7 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] = (q7_t) pSrc[n] >> 24; 0 <= n < blockSize.
51 </pre>
52 */
53 #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
arm_q31_to_q7(const q31_t * pSrc,q7_t * pDst,uint32_t blockSize)54 void arm_q31_to_q7(
55 const q31_t * pSrc,
56 q7_t * pDst,
57 uint32_t blockSize)
58 {
59 uint32_t blkCnt; /* loop counters */
60 q31x4x4_t tmp;
61 q15x8_t evVec, oddVec;
62 q7x16_t vecDst;
63 q31_t const *pSrcVec;
64
65 pSrcVec = (q31_t const *) pSrc;
66 blkCnt = blockSize >> 4;
67 while (blkCnt > 0U)
68 {
69 tmp = vld4q(pSrcVec);
70 pSrcVec += 16;
71 /* C = (q7_t) A >> 24 */
72 /* convert from q31 to q7 and then store the results in the destination buffer */
73 /*
74 * narrow and pack evens
75 */
76 evVec = vshrnbq_n_s32(evVec, tmp.val[0], 16);
77 evVec = vshrntq_n_s32(evVec, tmp.val[2], 16);
78 /*
79 * narrow and pack odds
80 */
81 oddVec = vshrnbq_n_s32(oddVec, tmp.val[1], 16);
82 oddVec = vshrntq_n_s32(oddVec, tmp.val[3], 16);
83 /*
84 * narrow & merge
85 */
86 vecDst = vshrnbq_n_s16(vecDst, evVec, 8);
87 vecDst = vshrntq_n_s16(vecDst, oddVec, 8);
88
89 vst1q(pDst, vecDst);
90 pDst += 16;
91 /*
92 * Decrement the blockSize loop counter
93 */
94 blkCnt--;
95 }
96 /*
97 * tail
98 */
99 blkCnt = blockSize & 0xF;
100 while (blkCnt > 0U)
101 {
102 /* C = (q7_t) (A >> 24) */
103
104 /* Convert from q31 to q7 and store result in destination buffer */
105 *pDst++ = (q7_t) (*pSrcVec++ >> 24);
106
107 /* Decrement loop counter */
108 blkCnt--;
109 }
110 }
111 #else
arm_q31_to_q7(const q31_t * pSrc,q7_t * pDst,uint32_t blockSize)112 void arm_q31_to_q7(
113 const q31_t * pSrc,
114 q7_t * pDst,
115 uint32_t blockSize)
116 {
117 uint32_t blkCnt; /* Loop counter */
118 const q31_t *pIn = pSrc; /* Source pointer */
119
120 #if defined (ARM_MATH_LOOPUNROLL)
121
122 q7_t out1, out2, out3, out4;
123
124 /* Loop unrolling: Compute 4 outputs at a time */
125 blkCnt = blockSize >> 2U;
126
127 while (blkCnt > 0U)
128 {
129 /* C = (q7_t) (A >> 24) */
130
131 /* Convert from q31 to q7 and store result in destination buffer */
132
133 out1 = (q7_t) (*pIn++ >> 24);
134 out2 = (q7_t) (*pIn++ >> 24);
135 out3 = (q7_t) (*pIn++ >> 24);
136 out4 = (q7_t) (*pIn++ >> 24);
137 write_q7x4_ia (&pDst, __PACKq7(out1, out2, out3, out4));
138
139 /* Decrement loop counter */
140 blkCnt--;
141 }
142
143 /* Loop unrolling: Compute remaining outputs */
144 blkCnt = blockSize % 0x4U;
145
146 #else
147
148 /* Initialize blkCnt with number of samples */
149 blkCnt = blockSize;
150
151 #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
152
153 while (blkCnt > 0U)
154 {
155 /* C = (q7_t) (A >> 24) */
156
157 /* Convert from q31 to q7 and store result in destination buffer */
158 *pDst++ = (q7_t) (*pIn++ >> 24);
159
160 /* Decrement loop counter */
161 blkCnt--;
162 }
163
164 }
165 #endif /* defined(ARM_MATH_MVEI) */
166
167 /**
168 @} end of q31_to_x group
169 */
170