mirror of https://gitee.com/openkylin/linux.git
ff5fdafc9e
The __memzero assembly code is almost identical to memset's except for two orr instructions. The runtime performance of __memset(p, n) and memset(p, 0, n) is accordingly almost identical. However, the memset() macro used to guard against a zero length and to call __memzero at compile time when the fill value is a constant zero interferes with compiler optimizations. Arnd found tha the test against a zero length brings up some new warnings with gcc v8: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82103 And successively rremoving the test against a zero length and the call to __memzero optimization produces the following kernel sizes for defconfig with gcc 6: text data bss dec hex filename 12248142 6278960 413588 18940690 1210312 vmlinux.orig 12244474 6278960 413588 18937022 120f4be vmlinux.no_zero_test 12239160 6278960 413588 18931708 120dffc vmlinux.no_memzero So it is probably not worth keeping __memzero around given that the compiler can do a better job at inlining trivial memset(p,0,n) on its own. And the memset code already handles a zero length just fine. Suggested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> |
||
|---|---|---|
| .. | ||
| .gitignore | ||
| Makefile | ||
| atags_to_fdt.c | ||
| big-endian.S | ||
| debug.S | ||
| decompress.c | ||
| efi-header.S | ||
| head-sa1100.S | ||
| head-sharpsl.S | ||
| head-xscale.S | ||
| head.S | ||
| libfdt_env.h | ||
| ll_char_wr.S | ||
| misc.c | ||
| piggy.S | ||
| string.c | ||
| vmlinux.lds.S | ||