| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_shift_q31.c |
| * Description: Shifts the elements of a Q31 vector by a specified number of bits |
| * |
| * $Date: 27. January 2017 |
| * $Revision: V.1.5.1 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @ingroup groupMath |
| */ |
| /** |
| * @defgroup shift Vector Shift |
| * |
| * Shifts the elements of a fixed-point vector by a specified number of bits. |
| * There are separate functions for Q7, Q15, and Q31 data types. |
| * The underlying algorithm used is: |
| * |
| * <pre> |
| * pDst[n] = pSrc[n] << shift, 0 <= n < blockSize. |
| * </pre> |
| * |
| * If <code>shift</code> is positive then the elements of the vector are shifted to the left. |
| * If <code>shift</code> is negative then the elements of the vector are shifted to the right. |
| * |
| * The functions support in-place computation allowing the source and destination |
| * pointers to reference the same memory buffer. |
| */ |
| |
| /** |
| * @addtogroup shift |
| * @{ |
| */ |
| |
| /** |
| * @brief Shifts the elements of a Q31 vector a specified number of bits. |
| * @param[in] *pSrc points to the input vector |
| * @param[in] shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right. |
| * @param[out] *pDst points to the output vector |
| * @param[in] blockSize number of samples in the vector |
| * @return none. |
| * |
| * |
| * <b>Scaling and Overflow Behavior:</b> |
| * \par |
| * The function uses saturating arithmetic. |
| * Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] will be saturated. |
| */ |
| |
| void arm_shift_q31( |
| q31_t * pSrc, |
| int8_t shiftBits, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| uint32_t blkCnt; /* loop counter */ |
| uint8_t sign = (shiftBits & 0x80); /* Sign of shiftBits */ |
| |
| #if defined (ARM_MATH_DSP) |
| |
| q31_t in1, in2, in3, in4; /* Temporary input variables */ |
| q31_t out1, out2, out3, out4; /* Temporary output variables */ |
| |
| /*loop Unrolling */ |
| blkCnt = blockSize >> 2U; |
| |
| |
| if (sign == 0U) |
| { |
| /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
| ** a second loop below computes the remaining 1 to 3 samples. */ |
| while (blkCnt > 0U) |
| { |
| /* C = A << shiftBits */ |
| /* Shift the input and then store the results in the destination buffer. */ |
| in1 = *pSrc; |
| in2 = *(pSrc + 1); |
| out1 = in1 << shiftBits; |
| in3 = *(pSrc + 2); |
| out2 = in2 << shiftBits; |
| in4 = *(pSrc + 3); |
| if (in1 != (out1 >> shiftBits)) |
| out1 = 0x7FFFFFFF ^ (in1 >> 31); |
| |
| if (in2 != (out2 >> shiftBits)) |
| out2 = 0x7FFFFFFF ^ (in2 >> 31); |
| |
| *pDst = out1; |
| out3 = in3 << shiftBits; |
| *(pDst + 1) = out2; |
| out4 = in4 << shiftBits; |
| |
| if (in3 != (out3 >> shiftBits)) |
| out3 = 0x7FFFFFFF ^ (in3 >> 31); |
| |
| if (in4 != (out4 >> shiftBits)) |
| out4 = 0x7FFFFFFF ^ (in4 >> 31); |
| |
| *(pDst + 2) = out3; |
| *(pDst + 3) = out4; |
| |
| /* Update destination pointer to process next sampels */ |
| pSrc += 4U; |
| pDst += 4U; |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| } |
| else |
| { |
| |
| /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
| ** a second loop below computes the remaining 1 to 3 samples. */ |
| while (blkCnt > 0U) |
| { |
| /* C = A >> shiftBits */ |
| /* Shift the input and then store the results in the destination buffer. */ |
| in1 = *pSrc; |
| in2 = *(pSrc + 1); |
| in3 = *(pSrc + 2); |
| in4 = *(pSrc + 3); |
| |
| *pDst = (in1 >> -shiftBits); |
| *(pDst + 1) = (in2 >> -shiftBits); |
| *(pDst + 2) = (in3 >> -shiftBits); |
| *(pDst + 3) = (in4 >> -shiftBits); |
| |
| |
| pSrc += 4U; |
| pDst += 4U; |
| |
| blkCnt--; |
| } |
| |
| } |
| |
| /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| |
| while (blkCnt > 0U) |
| { |
| /* C = A (>> or <<) shiftBits */ |
| /* Shift the input and then store the result in the destination buffer. */ |
| *pDst++ = (sign == 0U) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) : |
| (*pSrc++ >> -shiftBits); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| |
| } |
| |
| /** |
| * @} end of shift group |
| */ |