[U-Boot] [PATCH v2 1/5] string: Provide a slimmed-down memset()

Simon Glass
2017-04-02T15:50:28Z

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>
---

Changes in v2:
- Adjust the option to be SPL-only
- Change the option to default to off (name it CONFIG_SPL_TINY_MEMSET)

lib/Kconfig | 8 ++++++++
lib/string.c | 6 ++++--
2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/Kconfig b/lib/Kconfig
index 65c01573e1..58b5717dcd 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -52,6 +52,14 @@ 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 write a word at a time. Enable 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..c1a28c14ce 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;
+
+#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;
--
2.12.2.564.g063fe858b8-goog