From 0a571b085ff6dadf946b248133533d3ba68f6e31 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 15 Dec 2020 20:42:45 -0800 Subject: [PATCH] asm-generic: force inlining of get_order() to work around gcc10 poor decision When building mpc885_ads_defconfig with gcc 10.1, the function get_order() appears 50 times in vmlinux: [linux]# ppc-linux-objdump -x vmlinux | grep get_order | wc -l 50 [linux]# size vmlinux text data bss dec hex filename 3842620 675624 135160 4653404 47015c vmlinux In the old days, marking a function 'static inline' was forcing GCC to inline, but since commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly") GCC may decide to not inline a function. It looks like GCC 10 is taking poor decisions on this. get_order() compiles into the following tiny function, occupying 20 bytes of text. 0000007c : 7c: 38 63 ff ff addi r3,r3,-1 80: 54 63 a3 3e rlwinm r3,r3,20,12,31 84: 7c 63 00 34 cntlzw r3,r3 88: 20 63 00 20 subfic r3,r3,32 8c: 4e 80 00 20 blr By forcing get_order() to be __always_inline, the size of text is reduced by 1940 bytes, that is almost twice the space occupied by 50 times get_order() [linux-powerpc]# size vmlinux text data bss dec hex filename 3840680 675588 135176 4651444 46f9b4 vmlinux Link: https://lkml.kernel.org/r/96c6172d619c51acc5c1c4884b80785c59af4102.1602949927.git.christophe.leroy@csgroup.eu Signed-off-by: Christophe Leroy Reviewed-by: Joel Stanley Cc: Segher Boessenkool Cc: Arnd Bergmann Cc: Masahiro Yamada Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/getorder.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/asm-generic/getorder.h b/include/asm-generic/getorder.h index e9f20b813a69..f2979e3a96b6 100644 --- a/include/asm-generic/getorder.h +++ b/include/asm-generic/getorder.h @@ -26,7 +26,7 @@ * * The result is undefined if the size is 0. */ -static inline __attribute_const__ int get_order(unsigned long size) +static __always_inline __attribute_const__ int get_order(unsigned long size) { if (__builtin_constant_p(size)) { if (!size)