Off-topic:
Это с DSP для STM32F4 (CMSIS-DSP library)
Код:
;/* ----------------------------------------------------------------------
;* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
;*
;* $Date: 12. March 2014
;* $Revision: V1.4.4
;*
;* 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