pigweed / third_party / github / STMicroelectronics / cmsis_core / cb6d9400754e6c9050487dfa573949b61152ac99 / . / DSP / Source / BasicMathFunctions / arm_negate_q7.c

/* ---------------------------------------------------------------------- | |

* Project: CMSIS DSP Library | |

* Title: arm_negate_q7.c | |

* Description: Negates Q7 vectors | |

* | |

* $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 | |

*/ | |

/** | |

* @addtogroup negate | |

* @{ | |

*/ | |

/** | |

* @brief Negates the elements of a Q7 vector. | |

* @param[in] *pSrc points to the input vector | |

* @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. | |

* The Q7 value -1 (0x80) will be saturated to the maximum allowable positive value 0x7F. | |

*/ | |

void arm_negate_q7( | |

q7_t * pSrc, | |

q7_t * pDst, | |

uint32_t blockSize) | |

{ | |

uint32_t blkCnt; /* loop counter */ | |

q7_t in; | |

#if defined (ARM_MATH_DSP) | |

/* Run the below code for Cortex-M4 and Cortex-M3 */ | |

q31_t input; /* Input values1-4 */ | |

q31_t zero = 0x00000000; | |

/*loop Unrolling */ | |

blkCnt = blockSize >> 2U; | |

/* 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 */ | |

/* Read four inputs */ | |

input = *__SIMD32(pSrc)++; | |

/* Store the Negated results in the destination buffer in a single cycle by packing the results */ | |

*__SIMD32(pDst)++ = __QSUB8(zero, input); | |

/* Decrement the loop counter */ | |

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 */ | |

/* Negate and then store the results in the destination buffer. */ \ | |

in = *pSrc++; | |

*pDst++ = (in == (q7_t) 0x80) ? 0x7f : -in; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

} | |

/** | |

* @} end of negate group | |

*/ |