pigweed / third_party / github / STMicroelectronics / cmsis_core / refs/heads/cm4 / . / DSP / Source / BasicMathFunctions / arm_negate_q7.c

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

* Project: CMSIS DSP Library | |

* Title: arm_negate_q7.c | |

* Description: Negates Q7 vectors | |

* | |

* $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 | |

*/ | |

/** | |

@addtogroup BasicNegate | |

@{ | |

*/ | |

/** | |

@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 each vector. | |

@return none | |

@par Scaling and Overflow Behavior | |

The function uses saturating arithmetic. | |

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

*/ | |

void arm_negate_q7( | |

const q7_t * pSrc, | |

q7_t * pDst, | |

uint32_t blockSize) | |

{ | |

uint32_t blkCnt; /* Loop counter */ | |

q7_t in; /* Temporary input variable */ | |

#if defined (ARM_MATH_LOOPUNROLL) | |

#if defined (ARM_MATH_DSP) | |

q31_t in1; /* Temporary input variable */ | |

#endif | |

/* Loop unrolling: Compute 4 outputs at a time */ | |

blkCnt = blockSize >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* C = -A */ | |

#if defined (ARM_MATH_DSP) | |

/* Negate and store result in destination buffer (4 samples at a time). */ | |

in1 = read_q7x4_ia ((q7_t **) &pSrc); | |

write_q7x4_ia (&pDst, __QSUB8(0, in1)); | |

#else | |

in = *pSrc++; | |

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

in = *pSrc++; | |

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

in = *pSrc++; | |

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

in = *pSrc++; | |

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

#endif | |

/* 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) */ | |

while (blkCnt > 0U) | |

{ | |

/* C = -A */ | |

/* Negate and store result in destination buffer. */ | |

in = *pSrc++; | |

#if defined (ARM_MATH_DSP) | |

*pDst++ = (q7_t) __QSUB(0, in); | |

#else | |

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

#endif | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

} | |

/** | |

@} end of BasicNegate group | |

*/ |