string: Provide a slimmed-down memset()

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>

diff --git a/lib/Kconfig b/lib/Kconfig
index 65c01573e194e13b0d4a9c64923c840525782312..5115d047f86f6c192440705c645d7d4d02140181 100644 (file)
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -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

diff --git a/lib/string.c b/lib/string.c
index 67d5f6a4213a4c9e3dcdfe067724e4a7885baad6..c1a28c14ced51dd58424a10d2af0e1444207a80a 100644 (file)
--- 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;