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

[Simon Glass]

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 at 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