[PATCH 4/6] ARM: zImage: gather some string functions into string.c
Dave Martin
dave.martin at linaro.org
Wed Sep 14 09:13:14 EDT 2011
On Wed, Sep 14, 2011 at 01:41:44AM -0400, Nicolas Pitre wrote:
> From: Nicolas Pitre <nicolas.pitre at linaro.org>
>
> This is a small subset of string functions needed by commits to come.
> Except for memcpy() which is unchanged from its original location, their
> implementation is meant to be small, and -Os is enforced to prevent gcc
> from doing pointless loop unrolling.
>
> Signed-off-by: Nicolas Pitre <nicolas.pitre at linaro.org>
> ---
> arch/arm/boot/compressed/Makefile | 4 +
> arch/arm/boot/compressed/misc.c | 42 +------------
> arch/arm/boot/compressed/string.c | 127 +++++++++++++++++++++++++++++++++++++
> 3 files changed, 132 insertions(+), 41 deletions(-)
> create mode 100644 arch/arm/boot/compressed/string.c
>
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 4867647b97..c20ddc69d9 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -26,6 +26,10 @@ HEAD = head.o
> OBJS += misc.o decompress.o
> FONTC = $(srctree)/drivers/video/console/font_acorn_8x8.c
>
> +# string library code (-Os is enforced to keep it much smaller)
> +OBJS += string.o
> +CFLAGS_string.o := -Os
> +
> #
> # Architecture dependencies
> #
> diff --git a/arch/arm/boot/compressed/misc.c b/arch/arm/boot/compressed/misc.c
> index 832d37236c..8e2a8fca5e 100644
> --- a/arch/arm/boot/compressed/misc.c
> +++ b/arch/arm/boot/compressed/misc.c
> @@ -18,14 +18,9 @@
>
> unsigned int __machine_arch_type;
>
> -#define _LINUX_STRING_H_
> -
> #include <linux/compiler.h> /* for inline */
> -#include <linux/types.h> /* for size_t */
> -#include <linux/stddef.h> /* for NULL */
> +#include <linux/types.h>
> #include <linux/linkage.h>
> -#include <asm/string.h>
> -
>
> static void putstr(const char *ptr);
> extern void error(char *x);
> @@ -101,41 +96,6 @@ static void putstr(const char *ptr)
> flush();
> }
>
> -
> -void *memcpy(void *__dest, __const void *__src, size_t __n)
> -{
> - int i = 0;
> - unsigned char *d = (unsigned char *)__dest, *s = (unsigned char *)__src;
> -
> - for (i = __n >> 3; i > 0; i--) {
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - }
> -
> - if (__n & 1 << 2) {
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - *d++ = *s++;
> - }
> -
> - if (__n & 1 << 1) {
> - *d++ = *s++;
> - *d++ = *s++;
> - }
> -
> - if (__n & 1)
> - *d++ = *s++;
> -
> - return __dest;
> -}
Have you seen this?
http://en.wikipedia.org/wiki/Duff%27s_device
Once I finished vomiting, this actually struck be as rather neat.
If I've understood right, it seems a good fit for the manual unrolling
you do here.
Cheers
---Dave
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