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src/Cortex-M4-M3/BasicMathFunctions/arm_shift_q7.c@0:1014af42efd9, 2011-03-10 (annotated)

Committer:: simon
Date:: Thu Mar 10 15:07:50 2011 +0000
Revision:: 0:1014af42efd9

Who changed what in which revision?

User	Revision	Line number	New contents of line
simon	0:1014af42efd9	1	/* ----------------------------------------------------------------------
simon	0:1014af42efd9	2	* Copyright (C) 2010 ARM Limited. All rights reserved.
simon	0:1014af42efd9	3	*
simon	0:1014af42efd9	4	* $Date: 29. November 2010
simon	0:1014af42efd9	5	* $Revision: V1.0.3
simon	0:1014af42efd9	6	*
simon	0:1014af42efd9	7	* Project: CMSIS DSP Library
simon	0:1014af42efd9	8	* Title: arm_shift_q7.c
simon	0:1014af42efd9	9	*
simon	0:1014af42efd9	10	* Description: Processing function for the Q7 Shifting
simon	0:1014af42efd9	11	*
simon	0:1014af42efd9	12	* Target Processor: Cortex-M4/Cortex-M3
simon	0:1014af42efd9	13	*
simon	0:1014af42efd9	14	* Version 1.0.3 2010/11/29
simon	0:1014af42efd9	15	* Re-organized the CMSIS folders and updated documentation.
simon	0:1014af42efd9	16	*
simon	0:1014af42efd9	17	* Version 1.0.2 2010/11/11
simon	0:1014af42efd9	18	* Documentation updated.
simon	0:1014af42efd9	19	*
simon	0:1014af42efd9	20	* Version 1.0.1 2010/10/05
simon	0:1014af42efd9	21	* Production release and review comments incorporated.
simon	0:1014af42efd9	22	*
simon	0:1014af42efd9	23	* Version 1.0.0 2010/09/20
simon	0:1014af42efd9	24	* Production release and review comments incorporated.
simon	0:1014af42efd9	25	*
simon	0:1014af42efd9	26	* Version 0.0.7 2010/06/10
simon	0:1014af42efd9	27	* Misra-C changes done
simon	0:1014af42efd9	28	* -------------------------------------------------------------------- */
simon	0:1014af42efd9	29
simon	0:1014af42efd9	30	#include "arm_math.h"
simon	0:1014af42efd9	31
simon	0:1014af42efd9	32	/**
simon	0:1014af42efd9	33	* @ingroup groupMath
simon	0:1014af42efd9	34	*/
simon	0:1014af42efd9	35
simon	0:1014af42efd9	36	/**
simon	0:1014af42efd9	37	* @addtogroup shift
simon	0:1014af42efd9	38	* @{
simon	0:1014af42efd9	39	*/
simon	0:1014af42efd9	40
simon	0:1014af42efd9	41
simon	0:1014af42efd9	42	/**
simon	0:1014af42efd9	43	* @brief Shifts the elements of a Q7 vector a specified number of bits.
simon	0:1014af42efd9	44	* @param *pSrc points to the input vector
simon	0:1014af42efd9	45	* @param shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right.
simon	0:1014af42efd9	46	* @param *pDst points to the output vector
simon	0:1014af42efd9	47	* @param blockSize number of samples in the vector
simon	0:1014af42efd9	48	* @return none.
simon	0:1014af42efd9	49	*
simon	0:1014af42efd9	50	* <b>Scaling and Overflow Behavior:</b>
simon	0:1014af42efd9	51	* \par
simon	0:1014af42efd9	52	* The function uses saturating arithmetic.
simon	0:1014af42efd9	53	* Results outside of the allowable Q7 range [0x8 0x7F] will be saturated.
simon	0:1014af42efd9	54	*/
simon	0:1014af42efd9	55
simon	0:1014af42efd9	56	void arm_shift_q7(
simon	0:1014af42efd9	57	q7_t * pSrc,
simon	0:1014af42efd9	58	int8_t shiftBits,
simon	0:1014af42efd9	59	q7_t * pDst,
simon	0:1014af42efd9	60	uint32_t blockSize)
simon	0:1014af42efd9	61	{
simon	0:1014af42efd9	62	uint32_t blkCnt; /* loop counter */
simon	0:1014af42efd9	63	uint8_t sign; /* Sign of shiftBits */
simon	0:1014af42efd9	64	q7_t in1; /* Input value1 */
simon	0:1014af42efd9	65	q7_t in2; /* Input value2 */
simon	0:1014af42efd9	66	q7_t in3; /* Input value3 */
simon	0:1014af42efd9	67	q7_t in4; /* Input value4 */
simon	0:1014af42efd9	68
simon	0:1014af42efd9	69
simon	0:1014af42efd9	70	/loop Unrolling /
simon	0:1014af42efd9	71	blkCnt = blockSize >> 2u;
simon	0:1014af42efd9	72
simon	0:1014af42efd9	73	/* Getting the sign of shiftBits */
simon	0:1014af42efd9	74	sign = (shiftBits & 0x80);
simon	0:1014af42efd9	75
simon	0:1014af42efd9	76	/* If the shift value is positive then do right shift else left shift */
simon	0:1014af42efd9	77	if(sign == 0u)
simon	0:1014af42efd9	78	{
simon	0:1014af42efd9	79	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	80	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	81	while(blkCnt > 0u)
simon	0:1014af42efd9	82	{
simon	0:1014af42efd9	83	/* C = A << shiftBits */
simon	0:1014af42efd9	84	/* Read 4 inputs */
simon	0:1014af42efd9	85	in1 = *pSrc++;
simon	0:1014af42efd9	86	in2 = *pSrc++;
simon	0:1014af42efd9	87	in3 = *pSrc++;
simon	0:1014af42efd9	88	in4 = *pSrc++;
simon	0:1014af42efd9	89
simon	0:1014af42efd9	90	/* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
simon	0:1014af42efd9	91	*__SIMD32(pDst)++ = __PACKq7(__SSAT((in1 << shiftBits), 8),
simon	0:1014af42efd9	92	__SSAT((in2 << shiftBits), 8),
simon	0:1014af42efd9	93	__SSAT((in3 << shiftBits), 8),
simon	0:1014af42efd9	94	__SSAT((in4 << shiftBits), 8));
simon	0:1014af42efd9	95
simon	0:1014af42efd9	96	/* Decrement the loop counter */
simon	0:1014af42efd9	97	blkCnt--;
simon	0:1014af42efd9	98	}
simon	0:1014af42efd9	99
simon	0:1014af42efd9	100	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	101	** No loop unrolling is used. */
simon	0:1014af42efd9	102	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	103
simon	0:1014af42efd9	104	while(blkCnt > 0u)
simon	0:1014af42efd9	105	{
simon	0:1014af42efd9	106	/* C = A << shiftBits */
simon	0:1014af42efd9	107	/* Shift the input and then store the result in the destination buffer. */
simon	0:1014af42efd9	108	pDst++ = (q7_t) __SSAT((pSrc++ << shiftBits), 8);
simon	0:1014af42efd9	109
simon	0:1014af42efd9	110	/* Decrement the loop counter */
simon	0:1014af42efd9	111	blkCnt--;
simon	0:1014af42efd9	112	}
simon	0:1014af42efd9	113	}
simon	0:1014af42efd9	114	else
simon	0:1014af42efd9	115	{
simon	0:1014af42efd9	116	/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
simon	0:1014af42efd9	117	** a second loop below computes the remaining 1 to 3 samples. */
simon	0:1014af42efd9	118	while(blkCnt > 0u)
simon	0:1014af42efd9	119	{
simon	0:1014af42efd9	120	/* C = A >> shiftBits */
simon	0:1014af42efd9	121	/* Read 4 inputs */
simon	0:1014af42efd9	122	in1 = *pSrc++;
simon	0:1014af42efd9	123	in2 = *pSrc++;
simon	0:1014af42efd9	124	in3 = *pSrc++;
simon	0:1014af42efd9	125	in4 = *pSrc++;
simon	0:1014af42efd9	126
simon	0:1014af42efd9	127	/* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
simon	0:1014af42efd9	128	*__SIMD32(pDst)++ = __PACKq7((in1 >> -shiftBits), (in2 >> -shiftBits),
simon	0:1014af42efd9	129	(in3 >> -shiftBits), (in4 >> -shiftBits));
simon	0:1014af42efd9	130
simon	0:1014af42efd9	131	/* Decrement the loop counter */
simon	0:1014af42efd9	132	blkCnt--;
simon	0:1014af42efd9	133	}
simon	0:1014af42efd9	134
simon	0:1014af42efd9	135	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
simon	0:1014af42efd9	136	** No loop unrolling is used. */
simon	0:1014af42efd9	137	blkCnt = blockSize % 0x4u;
simon	0:1014af42efd9	138
simon	0:1014af42efd9	139	while(blkCnt > 0u)
simon	0:1014af42efd9	140	{
simon	0:1014af42efd9	141	/* C = A >> shiftBits */
simon	0:1014af42efd9	142	/* Shift the input and then store the result in the destination buffer. */
simon	0:1014af42efd9	143	pDst++ = (pSrc++ >> -shiftBits);
simon	0:1014af42efd9	144
simon	0:1014af42efd9	145	/* Decrement the loop counter */
simon	0:1014af42efd9	146	blkCnt--;
simon	0:1014af42efd9	147	}
simon	0:1014af42efd9	148	}
simon	0:1014af42efd9	149	}
simon	0:1014af42efd9	150
simon	0:1014af42efd9	151	/**
simon	0:1014af42efd9	152	* @} end of shift group
simon	0:1014af42efd9	153	*/

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Created:	29 Jun 2017
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