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    Subject[PATCH v7] arm: use built-in byte swap function
    Enable the compiler intrinsic for byte swapping on arch ARM.  This
    allows the compiler to detect and be able to optimize out byte
    swappings, and has a very modest benefit on vmlinux size (Linaro gcc
    4.8):

    text data bss dec hex filename
    2840310 123932 61960 3026202 2e2d1a vmlinux-lart #orig
    2840152 123932 61960 3026044 2e2c7c vmlinux-lart #builtin-bswap

    6473120 314840 5616016 12403976 bd4508 vmlinux-mxs #orig
    6472586 314848 5616016 12403450 bd42fa vmlinux-mxs #builtin-bswap

    7419872 318372 379556 8117800 7bde28 vmlinux-imx_v6_v7 #orig
    7419170 318364 379556 8117090 7bdb62 vmlinux-imx_v6_v7 #builtin-bswap

    Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
    Reviewed-by: Nicolas Pitre <nico@linaro.org>
    Acked-by: David Woodhouse <David.Woodhouse@intel.com>
    ---
    resending as v6 appears to have fallen though the cracks. Russell?

    v7: rebased onto next-20130521, re-ran above vmlinux sizes with
    Linaro gcc 4.8, added Nicolas' Reviewed-by, and David's Acked-by.
    v6 and prior version information:
    https://lkml.org/lkml/2013/2/22/475

    arch/arm/Kconfig | 1 +
    arch/arm/boot/compressed/Makefile | 15 +++++++++++----
    arch/arm/kernel/armksyms.c | 4 ++++
    arch/arm/lib/Makefile | 2 +-
    arch/arm/lib/bswapsdi2.S | 36 ++++++++++++++++++++++++++++++++++++
    5 files changed, 53 insertions(+), 5 deletions(-)
    create mode 100644 arch/arm/lib/bswapsdi2.S

    diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
    index a7fc5ea..c2fe04d 100644
    --- a/arch/arm/Kconfig
    +++ b/arch/arm/Kconfig
    @@ -63,6 +63,7 @@ config ARM
    select OLD_SIGSUSPEND3
    select OLD_SIGACTION
    select HAVE_CONTEXT_TRACKING
    + select ARCH_USE_BUILTIN_BSWAP
    help
    The ARM series is a line of low-power-consumption RISC chip designs
    licensed by ARM Ltd and targeted at embedded applications and
    diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
    index 198a4ad..bd8a176 100644
    --- a/arch/arm/boot/compressed/Makefile
    +++ b/arch/arm/boot/compressed/Makefile
    @@ -112,12 +112,12 @@ endif

    targets := vmlinux vmlinux.lds \
    piggy.$(suffix_y) piggy.$(suffix_y).o \
    - lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S \
    - font.o font.c head.o misc.o $(OBJS)
    + lib1funcs.o lib1funcs.S ashldi3.o ashldi3.S bswapsdi2.o \
    + bswapsdi2.S font.o font.c head.o misc.o $(OBJS)

    # Make sure files are removed during clean
    extra-y += piggy.gzip piggy.lzo piggy.lzma piggy.xzkern piggy.lz4 \
    - lib1funcs.S ashldi3.S $(libfdt) $(libfdt_hdrs)
    + lib1funcs.S ashldi3.S bswapsdi2.S $(libfdt) $(libfdt_hdrs)

    ifeq ($(CONFIG_FUNCTION_TRACER),y)
    ORIG_CFLAGS := $(KBUILD_CFLAGS)
    @@ -159,6 +159,12 @@ ashldi3 = $(obj)/ashldi3.o
    $(obj)/ashldi3.S: $(srctree)/arch/$(SRCARCH)/lib/ashldi3.S
    $(call cmd,shipped)

    +# For __bswapsi2, __bswapdi2
    +bswapsdi2 = $(obj)/bswapsdi2.o
    +
    +$(obj)/bswapsdi2.S: $(srctree)/arch/$(SRCARCH)/lib/bswapsdi2.S
    + $(call cmd,shipped)
    +
    # We need to prevent any GOTOFF relocs being used with references
    # to symbols in the .bss section since we cannot relocate them
    # independently from the rest at run time. This can be achieved by
    @@ -180,7 +186,8 @@ if [ $(words $(ZRELADDR)) -gt 1 -a "$(CONFIG_AUTO_ZRELADDR)" = "" ]; then \
    fi

    $(obj)/vmlinux: $(obj)/vmlinux.lds $(obj)/$(HEAD) $(obj)/piggy.$(suffix_y).o \
    - $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) FORCE
    + $(addprefix $(obj)/, $(OBJS)) $(lib1funcs) $(ashldi3) \
    + $(bswapsdi2) FORCE
    @$(check_for_multiple_zreladdr)
    $(call if_changed,ld)
    @$(check_for_bad_syms)
    diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
    index 60d3b73..ba578f7 100644
    --- a/arch/arm/kernel/armksyms.c
    +++ b/arch/arm/kernel/armksyms.c
    @@ -35,6 +35,8 @@ extern void __ucmpdi2(void);
    extern void __udivsi3(void);
    extern void __umodsi3(void);
    extern void __do_div64(void);
    +extern void __bswapsi2(void);
    +extern void __bswapdi2(void);

    extern void __aeabi_idiv(void);
    extern void __aeabi_idivmod(void);
    @@ -114,6 +116,8 @@ EXPORT_SYMBOL(__ucmpdi2);
    EXPORT_SYMBOL(__udivsi3);
    EXPORT_SYMBOL(__umodsi3);
    EXPORT_SYMBOL(__do_div64);
    +EXPORT_SYMBOL(__bswapsi2);
    +EXPORT_SYMBOL(__bswapdi2);

    #ifdef CONFIG_AEABI
    EXPORT_SYMBOL(__aeabi_idiv);
    diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
    index af72969..5383df7 100644
    --- a/arch/arm/lib/Makefile
    +++ b/arch/arm/lib/Makefile
    @@ -13,7 +13,7 @@ lib-y := backtrace.o changebit.o csumipv6.o csumpartial.o \
    ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
    ucmpdi2.o lib1funcs.o div64.o \
    io-readsb.o io-writesb.o io-readsl.o io-writesl.o \
    - call_with_stack.o
    + call_with_stack.o bswapsdi2.o

    mmu-y := clear_user.o copy_page.o getuser.o putuser.o

    diff --git a/arch/arm/lib/bswapsdi2.S b/arch/arm/lib/bswapsdi2.S
    new file mode 100644
    index 0000000..2ba43a0
    --- /dev/null
    +++ b/arch/arm/lib/bswapsdi2.S
    @@ -0,0 +1,36 @@
    +#include <linux/linkage.h>
    +
    +#if __LINUX_ARM_ARCH__ >= 6
    +ENTRY(__bswapsi2)
    + rev r0, r0
    + bx lr
    +ENDPROC(__bswapsi2)
    +
    +ENTRY(__bswapdi2)
    + rev r3, r0
    + rev r0, r1
    + mov r1, r3
    + bx lr
    +ENDPROC(__bswapdi2)
    +#else
    +ENTRY(__bswapsi2)
    + eor r3, r0, r0, ror #16
    + mov r3, r3, lsr #8
    + bic r3, r3, #0xff00
    + eor r0, r3, r0, ror #8
    + mov pc, lr
    +ENDPROC(__bswapsi2)
    +
    +ENTRY(__bswapdi2)
    + mov ip, r1
    + eor r3, ip, ip, ror #16
    + eor r1, r0, r0, ror #16
    + mov r1, r1, lsr #8
    + mov r3, r3, lsr #8
    + bic r3, r3, #0xff00
    + bic r1, r1, #0xff00
    + eor r1, r1, r0, ror #8
    + eor r0, r3, ip, ror #8
    + mov pc, lr
    +ENDPROC(__bswapdi2)
    +#endif
    --
    1.8.1.5


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