From eb111869301e15b737315a46c913ae82bd19eb9d Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 13 Sep 2019 00:19:25 +0200 Subject: compiler-types.h: add asm_inline definition This adds an asm_inline macro which expands to "asm inline" [1] when the compiler supports it. This is currently gcc 9.1+, gcc 8.3 and (once released) gcc 7.5 [2]. It expands to just "asm" for other compilers. Using asm inline("foo") instead of asm("foo") overrules gcc's heuristic estimate of the size of the code represented by the asm() statement, and makes gcc use the minimum possible size instead. That can in turn affect gcc's inlining decisions. I wasn't sure whether to make this a function-like macro or not - this way, it can be combined with volatile as asm_inline volatile() but perhaps we'd prefer to spell that asm_inline_volatile() anyway. The Kconfig logic is taken from an RFC patch by Masahiro Yamada [3]. [1] Technically, asm __inline, since both inline and __inline__ are macros that attach various attributes, making gcc barf if one literally does "asm inline()". However, the third spelling __inline is available for referring to the bare keyword. [2] https://lore.kernel.org/lkml/20190907001411.GG9749@gate.crashing.org/ [3] https://lore.kernel.org/lkml/1544695154-15250-1-git-send-email-yamada.masahiro@socionext.com/ Signed-off-by: Rasmus Villemoes Signed-off-by: Miguel Ojeda --- init/Kconfig | 3 +++ 1 file changed, 3 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index bd7d650d4a99..7fee5978dd73 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -30,6 +30,9 @@ config CC_CAN_LINK config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) +config CC_HAS_ASM_INLINE + def_bool $(success,echo 'void foo(void) { asm inline (""); }' | $(CC) -x c - -c -o /dev/null) + config CC_HAS_WARN_MAYBE_UNINITIALIZED def_bool $(cc-option,-Wmaybe-uninitialized) help -- cgit v1.2.3-59-g8ed1b