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kernel
os
linux
ARM: findbit: operate by words
Convert the implementations to operate on words rather than bytes
which makes bitmap searching faster.
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
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arch/arm/include/asm/assembler.h
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arch/arm/include/asm/assembler.h
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-34
arch/arm/lib/findbit.S
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arch/arm/lib/findbit.S
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#include <asm/assembler.h>
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.text
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#ifdef __ARMEB__
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#define SWAB_ENDIAN le
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#else
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#define SWAB_ENDIAN be
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#endif
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.macro find_first, endian, set, name
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ENTRY(_find_first_\name\()bit_\endian)
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teq r1, #0
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beq 3f
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mov r2, #0
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1:
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.ifc \endian, be
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eor r3, r2, #0x18
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ARM( ldrb r3, [r0, r3, lsr #3] )
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THUMB( lsr r3, #3 )
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THUMB( ldrb r3, [r0, r3] )
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1: ldr r3, [r0], #4
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.ifeq \set
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mvns r3, r3 @ invert/test bits
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.else
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ARM( ldrb r3, [r0, r2, lsr #3] )
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THUMB( lsr r3, r2, #3 )
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THUMB( ldrb r3, [r0, r3] )
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movs r3, r3 @ test bits
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.endif
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.ifeq \set
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eors r3, r3, #0xff @ invert bits
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.ifc \endian, SWAB_ENDIAN
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bne .L_found_swab
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.else
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movs r3, r3
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bne .L_found @ found the bit?
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.endif
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bne .L_found @ any now set - found zero bit
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add r2, r2, #8 @ next bit pointer
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add r2, r2, #32 @ next index
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2: cmp r2, r1 @ any more?
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blo 1b
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3: mov r0, r1 @ no free bits
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3: mov r0, r1 @ no more bits
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ret lr
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ENDPROC(_find_first_\name\()bit_\endian)
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.endm
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ENTRY(_find_next_\name\()bit_\endian)
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cmp r2, r1
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bhs 3b
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ands ip, r2, #7
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beq 1b @ If new byte, goto old routine
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.ifc \endian, be
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eor r3, r2, #0x18
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ARM( ldrb r3, [r0, r3, lsr #3] )
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THUMB( lsr r3, #3 )
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THUMB( ldrb r3, [r0, r3] )
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.else
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ARM( ldrb r3, [r0, r2, lsr #3] )
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THUMB( lsr r3, r2, #3 )
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THUMB( ldrb r3, [r0, r3] )
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mov ip, r2, lsr #5 @ word index
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add r0, r0, ip, lsl #2
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ands ip, r2, #31 @ bit position
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beq 1b
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ldr r3, [r0], #4
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.ifeq \set
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mvn r3, r3 @ invert bits
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.endif
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.ifeq \set
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eor r3, r3, #0xff @ now looking for a 1 bit
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.ifc \endian, SWAB_ENDIAN
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rev_l r3, ip
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.if .Lrev_l_uses_tmp
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@ we need to recompute ip because rev_l will have overwritten
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@ it.
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and ip, r2, #31 @ bit position
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.endif
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.endif
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movs r3, r3, lsr ip @ shift off unused bits
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bne .L_found
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orr r2, r2, #7 @ if zero, then no bits here
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orr r2, r2, #31 @ no zero bits
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add r2, r2, #1 @ align bit pointer
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b 2b @ loop for next bit
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ENDPROC(_find_next_\name\()bit_\endian)
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/*
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* One or more bits in the LSB of r3 are assumed to be set.
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*/
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.L_found_swab:
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rev_l r3, ip
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.L_found:
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#if __LINUX_ARM_ARCH__ >= 7
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rbit r3, r3 @ reverse bits
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rsb r3, r3, #31 @ offset of first set bit
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add r0, r2, r3 @ add offset of first set bit
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#else
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tst r3, #0x0f
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mov ip, #~0
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tst r3, ip, lsr #16 @ test bits 0-15
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addeq r2, r2, #16
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moveq r3, r3, lsr #16
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tst r3, #0x00ff
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addeq r2, r2, #8
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moveq r3, r3, lsr #8
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tst r3, #0x000f
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addeq r2, r2, #4
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movne r3, r3, lsl #4
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tst r3, #0x30
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moveq r3, r3, lsr #4
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tst r3, #0x0003
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addeq r2, r2, #2
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movne r3, r3, lsl #2
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tst r3, #0x40
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moveq r3, r3, lsr #2
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tst r3, #0x0001
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addeq r2, r2, #1
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mov r0, r2
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#endif