diff options
Diffstat (limited to 'arch/arm/lib/findbit.S')
| -rw-r--r-- | arch/arm/lib/findbit.S | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S new file mode 100644 index 0000000000..b7ac2d3c07 --- /dev/null +++ b/arch/arm/lib/findbit.S @@ -0,0 +1,139 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/arm/lib/findbit.S + * + * Copyright (C) 1995-2000 Russell King + * + * 16th March 2001 - John Ripley <jripley@sonicblue.com> + * Fixed so that "size" is an exclusive not an inclusive quantity. + * All users of these functions expect exclusive sizes, and may + * also call with zero size. + * Reworked by rmk. + */ +#include <linux/linkage.h> +#include <asm/assembler.h> +#include <asm/unwind.h> + .text + +#ifdef __ARMEB__ +#define SWAB_ENDIAN le +#else +#define SWAB_ENDIAN be +#endif + + .macro find_first, endian, set, name +ENTRY(_find_first_\name\()bit_\endian) + UNWIND( .fnstart) + teq r1, #0 + beq 3f + mov r2, #0 +1: ldr r3, [r0], #4 + .ifeq \set + mvns r3, r3 @ invert/test bits + .else + movs r3, r3 @ test bits + .endif + .ifc \endian, SWAB_ENDIAN + bne .L_found_swab + .else + bne .L_found @ found the bit? + .endif + add r2, r2, #32 @ next index +2: cmp r2, r1 @ any more? + blo 1b +3: mov r0, r1 @ no more bits + ret lr + UNWIND( .fnend) +ENDPROC(_find_first_\name\()bit_\endian) + .endm + + .macro find_next, endian, set, name +ENTRY(_find_next_\name\()bit_\endian) + UNWIND( .fnstart) + cmp r2, r1 + bhs 3b + mov ip, r2, lsr #5 @ word index + add r0, r0, ip, lsl #2 + ands ip, r2, #31 @ bit position + beq 1b + ldr r3, [r0], #4 + .ifeq \set + mvn r3, r3 @ invert bits + .endif + .ifc \endian, SWAB_ENDIAN + rev_l r3, ip + .if .Lrev_l_uses_tmp + @ we need to recompute ip because rev_l will have overwritten + @ it. + and ip, r2, #31 @ bit position + .endif + .endif + movs r3, r3, lsr ip @ shift off unused bits + bne .L_found + orr r2, r2, #31 @ no zero bits + add r2, r2, #1 @ align bit pointer + b 2b @ loop for next bit + UNWIND( .fnend) +ENDPROC(_find_next_\name\()bit_\endian) + .endm + + .macro find_bit, endian, set, name + find_first \endian, \set, \name + find_next \endian, \set, \name + .endm + +/* _find_first_zero_bit_le and _find_next_zero_bit_le */ + find_bit le, 0, zero_ + +/* _find_first_bit_le and _find_next_bit_le */ + find_bit le, 1 + +#ifdef __ARMEB__ + +/* _find_first_zero_bit_be and _find_next_zero_bit_be */ + find_bit be, 0, zero_ + +/* _find_first_bit_be and _find_next_bit_be */ + find_bit be, 1 + +#endif + +/* + * One or more bits in the LSB of r3 are assumed to be set. + */ +.L_found_swab: + UNWIND( .fnstart) + rev_l r3, ip +.L_found: +#if __LINUX_ARM_ARCH__ >= 7 + rbit r3, r3 @ reverse bits + clz r3, r3 @ count high zero bits + add r0, r2, r3 @ add offset of first set bit +#elif __LINUX_ARM_ARCH__ >= 5 + rsb r0, r3, #0 + and r3, r3, r0 @ mask out lowest bit set + clz r3, r3 @ count high zero bits + rsb r3, r3, #31 @ offset of first set bit + add r0, r2, r3 @ add offset of first set bit +#else + mov ip, #~0 + tst r3, ip, lsr #16 @ test bits 0-15 + addeq r2, r2, #16 + moveq r3, r3, lsr #16 + tst r3, #0x00ff + addeq r2, r2, #8 + moveq r3, r3, lsr #8 + tst r3, #0x000f + addeq r2, r2, #4 + moveq r3, r3, lsr #4 + tst r3, #0x0003 + addeq r2, r2, #2 + moveq r3, r3, lsr #2 + tst r3, #0x0001 + addeq r2, r2, #1 + mov r0, r2 +#endif + cmp r1, r0 @ Clamp to maxbit + movlo r0, r1 + ret lr + UNWIND( .fnend) |