From ff5fdafc9e9702846480e0cea55ba861f72140a2 Mon Sep 17 00:00:00 2001 From: Nicolas Pitre Date: Fri, 19 Jan 2018 18:17:46 +0100 Subject: ARM: 8745/1: get rid of __memzero() 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 Signed-off-by: Nicolas Pitre Acked-by: Ard Biesheuvel Acked-by: Arnd Bergmann Signed-off-by: Russell King --- arch/arm/include/asm/string.h | 14 -------------- 1 file changed, 14 deletions(-) (limited to 'arch/arm/include/asm/string.h') diff --git a/arch/arm/include/asm/string.h b/arch/arm/include/asm/string.h index f54a3136aac6..111a1d8a41dd 100644 --- a/arch/arm/include/asm/string.h +++ b/arch/arm/include/asm/string.h @@ -39,18 +39,4 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n) return __memset64(p, v, n * 8, v >> 32); } -extern void __memzero(void *ptr, __kernel_size_t n); - -#define memset(p,v,n) \ - ({ \ - void *__p = (p); size_t __n = n; \ - if ((__n) != 0) { \ - if (__builtin_constant_p((v)) && (v) == 0) \ - __memzero((__p),(__n)); \ - else \ - memset((__p),(v),(__n)); \ - } \ - (__p); \ - }) - #endif -- cgit