rt-thread/bsp/dm365/platform/findbit.S

/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author        Notes
 * 2010-11-13     weety     first version
 */
//#include <rtthread.h>
                //.text

/*
 * Purpose  : Find a 'zero' bit
 * Prototype: int find_first_zero_bit(void *addr, unsigned int maxbit);
 */
.globl _find_first_zero_bit_le
_find_first_zero_bit_le:
        teq r1, #0
        beq 3f
        mov r2, #0
1:
        ldrb    r3, [r0, r2, lsr #3]
        lsr r3, r2, #3
        ldrb    r3, [r0, r3]
        eors    r3, r3, #0xff       @ invert bits
        bne .L_found        @ any now set - found zero bit
        add r2, r2, #8      @ next bit pointer
2:      cmp r2, r1          @ any more?
        blo 1b
3:      mov r0, r1          @ no free bits
        mov pc, lr
//ENDPROC(_find_first_zero_bit_le)

/*
 * Purpose  : Find next 'zero' bit
 * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
 */
.globl _find_next_zero_bit_le
_find_next_zero_bit_le:
        teq r1, #0
        beq 3b
        ands    ip, r2, #7
        beq 1b          @ If new byte, goto old routine
        ldrb    r3, [r0, r2, lsr #3]
        lsr r3, r2, #3
        ldrb    r3, [r0, r3]
        eor r3, r3, #0xff       @ now looking for a 1 bit
        movs    r3, r3, lsr ip      @ shift off unused bits
        bne .L_found
        orr r2, r2, #7      @ if zero, then no bits here
        add r2, r2, #1      @ align bit pointer
        b   2b          @ loop for next bit
//ENDPROC(_find_next_zero_bit_le)

/*
 * Purpose  : Find a 'one' bit
 * Prototype: int find_first_bit(const unsigned long *addr, unsigned int maxbit);
 */
.globl _find_first_bit_le
_find_first_bit_le:
        teq r1, #0
        beq 3f
        mov r2, #0
1:
        ldrb    r3, [r0, r2, lsr #3]
        lsr r3, r2, #3
        ldrb    r3, [r0, r3]
        movs    r3, r3
        bne .L_found        @ any now set - found zero bit
        add r2, r2, #8      @ next bit pointer
2:      cmp r2, r1          @ any more?
        blo 1b
3:      mov r0, r1          @ no free bits
        mov pc, lr
//ENDPROC(_find_first_bit_le)

/*
 * Purpose  : Find next 'one' bit
 * Prototype: int find_next_zero_bit(void *addr, unsigned int maxbit, int offset)
 */
.globl _find_next_bit_le
_find_next_bit_le:
        teq r1, #0
        beq 3b
        ands    ip, r2, #7
        beq 1b          @ If new byte, goto old routine
        ldrb    r3, [r0, r2, lsr #3]
        lsr r3, r2, #3
        ldrb    r3, [r0, r3]
        movs    r3, r3, lsr ip      @ shift off unused bits
        bne .L_found
        orr r2, r2, #7      @ if zero, then no bits here
        add r2, r2, #1      @ align bit pointer
        b   2b          @ loop for next bit
//ENDPROC(_find_next_bit_le)

#ifdef __ARMEB__

ENTRY(_find_first_zero_bit_be)
        teq r1, #0
        beq 3f
        mov r2, #0
1:      eor r3, r2, #0x18       @ big endian byte ordering
 ARM(       ldrb    r3, [r0, r3, lsr #3]    )
 THUMB(     lsr r3, #3          )
 THUMB(     ldrb    r3, [r0, r3]        )
        eors    r3, r3, #0xff       @ invert bits
        bne .L_found        @ any now set - found zero bit
        add r2, r2, #8      @ next bit pointer
2:      cmp r2, r1          @ any more?
        blo 1b
3:      mov r0, r1          @ no free bits
        mov pc, lr
ENDPROC(_find_first_zero_bit_be)

ENTRY(_find_next_zero_bit_be)
        teq r1, #0
        beq 3b
        ands    ip, r2, #7
        beq 1b          @ If new byte, goto old routine
        eor r3, r2, #0x18       @ big endian byte ordering
 ARM(       ldrb    r3, [r0, r3, lsr #3]    )
 THUMB(     lsr r3, #3          )
 THUMB(     ldrb    r3, [r0, r3]        )
        eor r3, r3, #0xff       @ now looking for a 1 bit
        movs    r3, r3, lsr ip      @ shift off unused bits
        bne .L_found
        orr r2, r2, #7      @ if zero, then no bits here
        add r2, r2, #1      @ align bit pointer
        b   2b          @ loop for next bit
ENDPROC(_find_next_zero_bit_be)

ENTRY(_find_first_bit_be)
        teq r1, #0
        beq 3f
        mov r2, #0
1:      eor r3, r2, #0x18       @ big endian byte ordering
 ARM(       ldrb    r3, [r0, r3, lsr #3]    )
 THUMB(     lsr r3, #3          )
 THUMB(     ldrb    r3, [r0, r3]        )
        movs    r3, r3
        bne .L_found        @ any now set - found zero bit
        add r2, r2, #8      @ next bit pointer
2:      cmp r2, r1          @ any more?
        blo 1b
3:      mov r0, r1          @ no free bits
        mov pc, lr
ENDPROC(_find_first_bit_be)

ENTRY(_find_next_bit_be)
        teq r1, #0
        beq 3b
        ands    ip, r2, #7
        beq 1b          @ If new byte, goto old routine
        eor r3, r2, #0x18       @ big endian byte ordering
 ARM(       ldrb    r3, [r0, r3, lsr #3]    )
 THUMB(     lsr r3, #3          )
 THUMB(     ldrb    r3, [r0, r3]        )
        movs    r3, r3, lsr ip      @ shift off unused bits
        bne .L_found
        orr r2, r2, #7      @ if zero, then no bits here
        add r2, r2, #1      @ align bit pointer
        b   2b          @ loop for next bit
ENDPROC(_find_next_bit_be)

#endif

/*
 * One or more bits in the LSB of r3 are assumed to be set.
 */
.L_found:
#if 1 //__LINUX_ARM_ARCH__ >= 5
        rsb r0, r3, #0
        and r3, r3, r0
        clz r3, r3
        rsb r3, r3, #31
        add r0, r2, r3
#else
        tst r3, #0x0f
        addeq   r2, r2, #4
        movne   r3, r3, lsl #4
        tst r3, #0x30
        addeq   r2, r2, #2
        movne   r3, r3, lsl #2
        tst r3, #0x40
        addeq   r2, r2, #1
        mov r0, r2
#endif
        cmp r1, r0          @ Clamp to maxbit
        movlo   r0, r1
        mov pc, lr