DSP_Lib/Source/TransformFunctions/arm_bitreversal2.S

;/* ----------------------------------------------------------------------
;* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
;*
;* $Date:       19. March 2015 
;* $Revision: 	V.1.4.5
;*
;* Project: 	CMSIS DSP Library
;* Title:	    arm_bitreversal2.S
;*
;* Description:	This is the arm_bitreversal_32 function done in
;*              assembly for maximum speed.  This function is called
;*              after doing an fft to reorder the output.  The function
;*              is loop unrolled by 2. arm_bitreversal_16 as well.
;*
;* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
;*
;* Redistribution and use in source and binary forms, with or without
;* modification, are permitted provided that the following conditions
;* are met:
;*   - Redistributions of source code must retain the above copyright
;*     notice, this list of conditions and the following disclaimer.
;*   - Redistributions in binary form must reproduce the above copyright
;*     notice, this list of conditions and the following disclaimer in
;*     the documentation and/or other materials provided with the
;*     distribution.
;*   - Neither the name of ARM LIMITED nor the names of its contributors
;*     may be used to endorse or promote products derived from this
;*     software without specific prior written permission.
;*
;* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
;* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
;* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
;* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
;* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
;* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
;* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
;* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
;* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
;* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
;* POSSIBILITY OF SUCH DAMAGE.
;* -------------------------------------------------------------------- */
#if defined(__CC_ARM)       // Keil
    #define CODESECT AREA     ||.text||, CODE, READONLY, ALIGN=2
    #define LABEL
#elif defined(__IASMARM__)  // IAR
    #define CODESECT SECTION `.text`:CODE
    #define PROC
    #define LABEL
    #define ENDP
    #define EXPORT PUBLIC
#elif defined(__CSMC__)		/* Cosmic */
	#define	CODESECT	switch .text
	#define THUMB
	#define EXPORT	xdef
	#define PROC	:
	#define LABEL	:
	#define ENDP
	#define arm_bitreversal_32 _arm_bitreversal_32
#elif defined (__GNUC__)    // GCC
    #define THUMB .thumb
    #define CODESECT .section .text
    #define EXPORT .global
    #define PROC :
    #define LABEL :
    #define ENDP
    #define END

    .syntax unified
#endif

	CODESECT
	THUMB

;/*
;* @brief  In-place bit reversal function.
;* @param[in, out] *pSrc        points to the in-place buffer of unknown 32-bit data type.
;* @param[in]      bitRevLen    bit reversal table length
;* @param[in]      *pBitRevTab  points to bit reversal table.
;* @return none.
;*/
	EXPORT arm_bitreversal_32
	EXPORT arm_bitreversal_16

#if defined(ARM_MATH_CM0) || defined(ARM_MATH_CM0PLUS)

arm_bitreversal_32 PROC
	ADDS     r3,r1,#1
	PUSH     {r4-r6}
	ADDS     r1,r2,#0
	LSRS     r3,r3,#1
arm_bitreversal_32_0 LABEL
	LDRH     r2,[r1,#2]
	LDRH     r6,[r1,#0]
	ADD      r2,r0,r2
	ADD      r6,r0,r6
	LDR      r5,[r2,#0]
	LDR      r4,[r6,#0]
	STR      r5,[r6,#0]
	STR      r4,[r2,#0]
	LDR      r5,[r2,#4]
	LDR      r4,[r6,#4]
	STR      r5,[r6,#4]
	STR      r4,[r2,#4]
	ADDS     r1,r1,#4
	SUBS     r3,r3,#1
	BNE      arm_bitreversal_32_0
	POP      {r4-r6}
	BX       lr
	ENDP

arm_bitreversal_16 PROC
	ADDS     r3,r1,#1
	PUSH     {r4-r6}
	ADDS     r1,r2,#0
	LSRS     r3,r3,#1
arm_bitreversal_16_0 LABEL
	LDRH     r2,[r1,#2]
	LDRH     r6,[r1,#0]
    LSRS     r2,r2,#1
    LSRS     r6,r6,#1
	ADD      r2,r0,r2
	ADD      r6,r0,r6
	LDR      r5,[r2,#0]
	LDR      r4,[r6,#0]
	STR      r5,[r6,#0]
	STR      r4,[r2,#0]
	ADDS     r1,r1,#4
	SUBS     r3,r3,#1
	BNE      arm_bitreversal_16_0
	POP      {r4-r6}
	BX       lr
	ENDP

#else

arm_bitreversal_32 PROC
	ADDS     r3,r1,#1
	CMP      r3,#1
	IT       LS
	BXLS     lr
	PUSH     {r4-r9}
	ADDS     r1,r2,#2
	LSRS     r3,r3,#2
arm_bitreversal_32_0 LABEL       ;/* loop unrolled by 2 */
	LDRH     r8,[r1,#4]
	LDRH     r9,[r1,#2]
	LDRH     r2,[r1,#0]
	LDRH     r12,[r1,#-2]
	ADD      r8,r0,r8
	ADD      r9,r0,r9
	ADD      r2,r0,r2
	ADD      r12,r0,r12
	LDR      r7,[r9,#0]
	LDR      r6,[r8,#0]
	LDR      r5,[r2,#0]
	LDR      r4,[r12,#0]
	STR      r6,[r9,#0]
	STR      r7,[r8,#0]
	STR      r5,[r12,#0]
	STR      r4,[r2,#0]
	LDR      r7,[r9,#4]
	LDR      r6,[r8,#4]
	LDR      r5,[r2,#4]
	LDR      r4,[r12,#4]
	STR      r6,[r9,#4]
	STR      r7,[r8,#4]
	STR      r5,[r12,#4]
	STR      r4,[r2,#4]
	ADDS     r1,r1,#8
	SUBS     r3,r3,#1
	BNE      arm_bitreversal_32_0
	POP      {r4-r9}
	BX       lr
	ENDP

arm_bitreversal_16 PROC
	ADDS     r3,r1,#1
	CMP      r3,#1
	IT       LS
	BXLS     lr
	PUSH     {r4-r9}
	ADDS     r1,r2,#2
	LSRS     r3,r3,#2
arm_bitreversal_16_0 LABEL       ;/* loop unrolled by 2 */
	LDRH     r8,[r1,#4]
	LDRH     r9,[r1,#2]
	LDRH     r2,[r1,#0]
	LDRH     r12,[r1,#-2]
	ADD      r8,r0,r8,LSR #1
	ADD      r9,r0,r9,LSR #1
	ADD      r2,r0,r2,LSR #1
	ADD      r12,r0,r12,LSR #1
	LDR      r7,[r9,#0]
	LDR      r6,[r8,#0]
	LDR      r5,[r2,#0]
	LDR      r4,[r12,#0]
	STR      r6,[r9,#0]
	STR      r7,[r8,#0]
	STR      r5,[r12,#0]
	STR      r4,[r2,#0]
	ADDS     r1,r1,#8
	SUBS     r3,r3,#1
	BNE      arm_bitreversal_16_0
	POP      {r4-r9}
	BX       lr
	ENDP

#endif

	END