[U-Boot] [PATCH 2/3] string: Provide a slimmed-down memset()

Simon Glass
2017-03-26T23:38:16Z

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>
---

lib/Kconfig | 9 +++++++++
lib/string.c | 6 ++++--
2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig b/lib/Kconfig
index 65c01573e1..5bf512d8c0 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -52,6 +52,15 @@ config LIB_RAND
help
This library provides pseudo-random number generator functions.

+config FAST_MEMSET
+ bool "Use an optimised memset()"
+ default y
+ 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 write a word at a time. Disable this option
+ to reduce code size slightly at the cost of some speed.
+
source lib/dhry/Kconfig

source lib/rsa/Kconfig
diff --git a/lib/string.c b/lib/string.c
index 67d5f6a421..159493ed17 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -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;
+
+#ifdef CONFIG_FAST_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;
--
2.12.1.578.ge9c3154ca4-goog