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string: Provide a slimmed-down memset()

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Most of the time the optimised memset() is what we want. For extreme
situations such as TPL it may be too large. For example on the 'rock'
board, using a simple loop saves a useful 48 bytes. With gcc 4.9 and
the rodata bug, this patch is enough to reduce the TPL image below the
limit.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
This commit is contained in:
Simon Glass 2017-04-02 09:50:28 -06:00
parent 3c00a2c8b5
commit ab4458bdb5
2 changed files with 13 additions and 2 deletions
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9
lib/Kconfig
View file

@ -52,6 +52,15 @@ config LIB_RAND
help
This library provides pseudo-random number generator functions.
config SPL_TINY_MEMSET
bool "Use a very small memset() in SPL"
help
The faster memset() is the arch-specific one (if available) enabled
by CONFIG_USE_ARCH_MEMSET. If that is not enabled, we can still get
better performance by writing a word at a time. But in very
size-constrained envrionments even this may be too big. Enable this
option to reduce code size slightly at the cost of some speed.
source lib/dhry/Kconfig
source lib/rsa/Kconfig

6
lib/string.c
View file

@ -437,8 +437,10 @@ char *strswab(const char *s)
void * memset(void * s,int c,size_t count)
{
unsigned long *sl = (unsigned long *) s;
unsigned long cl = 0;
char *s8;
#if !CONFIG_IS_ENABLED(TINY_MEMSET)
unsigned long cl = 0;
int i;
/* do it one word at a time (32 bits or 64 bits) while possible */
@ -452,7 +454,7 @@ void * memset(void * s,int c,size_t count)
count -= sizeof(*sl);
}
}
/* fill 8 bits at a time */
#endif /* fill 8 bits at a time */
s8 = (char *)sl;
while (count--)
*s8++ = c;