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authorRussell King (Oracle) <rmk+kernel@armlinux.org.uk>2022-07-27 02:27:38 +0300
committerRussell King (Oracle) <rmk+kernel@armlinux.org.uk>2022-11-14 15:00:58 +0300
commit2511d032f02e6426b0bd87d225b4b322a7154d15 (patch)
tree70946cd6a64e14f3ab6c79f4d8d21d88be2a621b /arch/arm/lib/findbit.S
parent2953a3e187e054a4cfba4190a2037dc16b327372 (diff)
downloadlinux-2511d032f02e6426b0bd87d225b4b322a7154d15.tar.xz
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>
Diffstat (limited to 'arch/arm/lib/findbit.S')
-rw-r--r--arch/arm/lib/findbit.S78
1 files changed, 44 insertions, 34 deletions
diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 8280f66d38a5..6ec584d16d46 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -14,32 +14,32 @@
#include <asm/assembler.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)
teq r1, #0
beq 3f
mov r2, #0
-1:
- .ifc \endian, be
- eor r3, r2, #0x18
- ARM( ldrb r3, [r0, r3, lsr #3] )
- THUMB( lsr r3, #3 )
- THUMB( ldrb r3, [r0, r3] )
+1: ldr r3, [r0], #4
+ .ifeq \set
+ mvns r3, r3 @ invert/test bits
.else
- ARM( ldrb r3, [r0, r2, lsr #3] )
- THUMB( lsr r3, r2, #3 )
- THUMB( ldrb r3, [r0, r3] )
+ movs r3, r3 @ test bits
.endif
- .ifeq \set
- eors r3, r3, #0xff @ invert bits
+ .ifc \endian, SWAB_ENDIAN
+ bne .L_found_swab
.else
- movs r3, r3
+ bne .L_found @ found the bit?
.endif
- bne .L_found @ any now set - found zero bit
- add r2, r2, #8 @ next bit pointer
+ add r2, r2, #32 @ next index
2: cmp r2, r1 @ any more?
blo 1b
-3: mov r0, r1 @ no free bits
+3: mov r0, r1 @ no more bits
ret lr
ENDPROC(_find_first_\name\()bit_\endian)
.endm
@@ -48,24 +48,25 @@ ENDPROC(_find_first_\name\()bit_\endian)
ENTRY(_find_next_\name\()bit_\endian)
cmp r2, r1
bhs 3b
- ands ip, r2, #7
- beq 1b @ If new byte, goto old routine
- .ifc \endian, be
- eor r3, r2, #0x18
- ARM( ldrb r3, [r0, r3, lsr #3] )
- THUMB( lsr r3, #3 )
- THUMB( ldrb r3, [r0, r3] )
- .else
- ARM( ldrb r3, [r0, r2, lsr #3] )
- THUMB( lsr r3, r2, #3 )
- THUMB( ldrb r3, [r0, r3] )
+ 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
- .ifeq \set
- eor r3, r3, #0xff @ now looking for a 1 bit
.endif
movs r3, r3, lsr ip @ shift off unused bits
bne .L_found
- orr r2, r2, #7 @ if zero, then no bits here
+ orr r2, r2, #31 @ no zero bits
add r2, r2, #1 @ align bit pointer
b 2b @ loop for next bit
ENDPROC(_find_next_\name\()bit_\endian)
@@ -95,6 +96,8 @@ ENDPROC(_find_next_\name\()bit_\endian)
/*
* One or more bits in the LSB of r3 are assumed to be set.
*/
+.L_found_swab:
+ rev_l r3, ip
.L_found:
#if __LINUX_ARM_ARCH__ >= 7
rbit r3, r3 @ reverse bits
@@ -107,13 +110,20 @@ ENDPROC(_find_next_\name\()bit_\endian)
rsb r3, r3, #31 @ offset of first set bit
add r0, r2, r3 @ add offset of first set bit
#else
- tst r3, #0x0f
+ 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
- movne r3, r3, lsl #4
- tst r3, #0x30
+ moveq r3, r3, lsr #4
+ tst r3, #0x0003
addeq r2, r2, #2
- movne r3, r3, lsl #2
- tst r3, #0x40
+ moveq r3, r3, lsr #2
+ tst r3, #0x0001
addeq r2, r2, #1
mov r0, r2
#endif