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

Am Sonntag, 2. April 2017, 09:50:28 CEST schrieb 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@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.
  

Wording sounds off, I guess we could do something like

[...better performance by] writing a word at a time. In very size-constrained environments even this may be to big though. [Enable this option...]

Otherwise Reviewed-by: Heiko Stuebner heiko@sntech.de

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;