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ARC: Always use SWAPE instructions for __arch_swab32()

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Since commit 67a697e7576 ("ARC: retire ARC750 support") all supported
CPUs have the 'swape' instruction.

Always use the implementation of __arch_swabe() which uses 'swape'.
ARCH_USE_BUILTIN_BSWAP can not be used as that results on libcalls on
-mcpu=arc700.

As as side-effect, remove a leak of an internal kconfig symbol through
the UAPI headers.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/lkml/0ae2688a-5a22-405b-adaf-9b5ad712b245@app.fastmail.com/
Suggested-by: Vineet Gupta <vgupta@kernel.org>
Link: https://lore.kernel.org/lkml/a033a402-e3c5-4982-9fff-b6a4c55817ae@kernel.org/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Thomas Weißschuh 2026-01-14 08:28:13 +01:00 • committed by Arnd Bergmann
parent eed444d025
commit b4171fd0b0
4 changed files with 1 additions and 71 deletions
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5
arch/arc/Kconfig
View file

@ -121,7 +121,6 @@ choice
config ARC_CPU_770
bool "ARC770"
depends on ISA_ARCOMPACT
select ARC_HAS_SWAPE
help
Support for ARC770 core introduced with Rel 4.10 (Summer 2011)
This core has a bunch of cool new features:
@ -340,10 +339,6 @@ config ARC_HAS_LLSC
default y
depends on !ARC_CANT_LLSC
config ARC_HAS_SWAPE
bool "Insn: SWAPE (endian-swap)"
default y
if ISA_ARCV2
config ARC_USE_UNALIGNED_MEM_ACCESS

3
arch/arc/Makefile
View file

@ -9,7 +9,7 @@ ifeq ($(CROSS_COMPILE),)
CROSS_COMPILE := $(call cc-cross-prefix, arc-linux- arceb-linux- arc-linux-gnu-)
endif
cflags-y += -fno-common -pipe -fno-builtin -mmedium-calls -D__linux__
cflags-y += -fno-common -pipe -fno-builtin -mmedium-calls -mswape -D__linux__
tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT) := -mcpu=arc700
tune-mcpu-def-$(CONFIG_ISA_ARCV2) := -mcpu=hs38
@ -41,7 +41,6 @@ endif
cflags-y += -fsection-anchors
cflags-$(CONFIG_ARC_HAS_LLSC) += -mlock
cflags-$(CONFIG_ARC_HAS_SWAPE) += -mswape
ifdef CONFIG_ISA_ARCV2

63
arch/arc/include/uapi/asm/swab.h
View file

@ -19,9 +19,6 @@
#include <linux/types.h>
/* Native single cycle endian swap insn */
#ifdef CONFIG_ARC_HAS_SWAPE
#define __arch_swab32(x) \
({ \
unsigned int tmp = x; \
@ -32,66 +29,6 @@
tmp; \
})
#else
/* Several ways of Endian-Swap Emulation for ARC
* 0: kernel generic
* 1: ARC optimised "C"
* 2: ARC Custom instruction
*/
#define ARC_BSWAP_TYPE 1
#if (ARC_BSWAP_TYPE == 1) /******* Software only ********/
/* The kernel default implementation of htonl is
* return x<<24 | x>>24 |
* (x & (__u32)0x0000ff00UL)<<8 | (x & (__u32)0x00ff0000UL)>>8;
*
* This generates 9 instructions on ARC (excluding the ld/st)
*
* 8051fd8c: ld r3,[r7,20] ; Mem op : Get the value to be swapped
* 8051fd98: asl r5,r3,24 ; get 3rd Byte
* 8051fd9c: lsr r2,r3,24 ; get 0th Byte
* 8051fda0: and r4,r3,0xff00
* 8051fda8: asl r4,r4,8 ; get 1st Byte
* 8051fdac: and r3,r3,0x00ff0000
* 8051fdb4: or r2,r2,r5 ; combine 0th and 3rd Bytes
* 8051fdb8: lsr r3,r3,8 ; 2nd Byte at correct place in Dst Reg
* 8051fdbc: or r2,r2,r4 ; combine 0,3 Bytes with 1st Byte
* 8051fdc0: or r2,r2,r3 ; combine 0,3,1 Bytes with 2nd Byte
* 8051fdc4: st r2,[r1,20] ; Mem op : save result back to mem
*
* Joern suggested a better "C" algorithm which is great since
* (1) It is portable to any architecture
* (2) At the same time it takes advantage of ARC ISA (rotate intrns)
*/
#define __arch_swab32(x) \
({ unsigned long __in = (x), __tmp; \
__tmp = __in << 8 | __in >> 24; /* ror tmp,in,24 */ \
__in = __in << 24 | __in >> 8; /* ror in,in,8 */ \
__tmp ^= __in; \
__tmp &= 0xff00ff; \
__tmp ^ __in; \
})
#elif (ARC_BSWAP_TYPE == 2) /* Custom single cycle bswap instruction */
#define __arch_swab32(x) \
({ \
unsigned int tmp = x; \
__asm__( \
" .extInstruction bswap, 7, 0x00, SUFFIX_NONE, SYNTAX_2OP \n"\
" bswap %0, %1 \n"\
: "=r" (tmp) \
: "r" (tmp)); \
tmp; \
})
#endif /* ARC_BSWAP_TYPE=zzz */
#endif /* CONFIG_ARC_HAS_SWAPE */
#if !defined(__STRICT_ANSI__) || defined(__KERNEL__)
#define __SWAB_64_THRU_32__
#endif

1
scripts/headers_install.sh
View file

@ -70,7 +70,6 @@ configs=$(sed -e '
#
# The format is <file-name>:<CONFIG-option> in each line.
config_leak_ignores="
arch/arc/include/uapi/asm/swab.h:CONFIG_ARC_HAS_SWAPE
arch/arm/include/uapi/asm/ptrace.h:CONFIG_CPU_ENDIAN_BE8
arch/nios2/include/uapi/asm/swab.h:CONFIG_NIOS2_CI_SWAB_NO
arch/nios2/include/uapi/asm/swab.h:CONFIG_NIOS2_CI_SWAB_SUPPORT