| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_shift_q31.c |
| * Description: Shifts the elements of a Q31 vector by a specified number of bits |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 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 BasicShift 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 BasicShift |
| @{ |
| */ |
| |
| /** |
| @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 |
| |
| @par Scaling and Overflow Behavior |
| The function uses saturating arithmetic. |
| Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] are saturated. |
| */ |
| |
| void arm_shift_q31( |
| const 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_LOOPUNROLL) |
| |
| q31_t in, out; /* Temporary variables */ |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| blkCnt = blockSize >> 2U; |
| |
| /* If the shift value is positive then do right shift else left shift */ |
| if (sign == 0U) |
| { |
| while (blkCnt > 0U) |
| { |
| /* C = A << shiftBits */ |
| |
| /* Shift input and store result in destination buffer. */ |
| in = *pSrc++; |
| out = in << shiftBits; |
| if (in != (out >> shiftBits)) |
| out = 0x7FFFFFFF ^ (in >> 31); |
| *pDst++ = out; |
| |
| in = *pSrc++; |
| out = in << shiftBits; |
| if (in != (out >> shiftBits)) |
| out = 0x7FFFFFFF ^ (in >> 31); |
| *pDst++ = out; |
| |
| in = *pSrc++; |
| out = in << shiftBits; |
| if (in != (out >> shiftBits)) |
| out = 0x7FFFFFFF ^ (in >> 31); |
| *pDst++ = out; |
| |
| in = *pSrc++; |
| out = in << shiftBits; |
| if (in != (out >> shiftBits)) |
| out = 0x7FFFFFFF ^ (in >> 31); |
| *pDst++ = out; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| } |
| else |
| { |
| while (blkCnt > 0U) |
| { |
| /* C = A >> shiftBits */ |
| |
| /* Shift input and store results in destination buffer. */ |
| *pDst++ = (*pSrc++ >> -shiftBits); |
| *pDst++ = (*pSrc++ >> -shiftBits); |
| *pDst++ = (*pSrc++ >> -shiftBits); |
| *pDst++ = (*pSrc++ >> -shiftBits); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| /* If the shift value is positive then do right shift else left shift */ |
| if (sign == 0U) |
| { |
| while (blkCnt > 0U) |
| { |
| /* C = A << shiftBits */ |
| |
| /* Shift input and store result in destination buffer. */ |
| *pDst++ = clip_q63_to_q31((q63_t) *pSrc++ << shiftBits); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| } |
| else |
| { |
| while (blkCnt > 0U) |
| { |
| /* C = A >> shiftBits */ |
| |
| /* Shift input and store result in destination buffer. */ |
| *pDst++ = (*pSrc++ >> -shiftBits); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| } |
| |
| } |
| |
| /** |
| @} end of BasicShift group |
| */ |