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| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2019-09-13 00:19:25 +0200 |
|---|---|---|
| committer | Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> | 2019-09-15 20:14:15 +0200 |
| commit | eb111869301e15b737315a46c913ae82bd19eb9d (patch) | |
| tree | 318b0dbee699f3c007fc0a3c6fce072a103f45d1 /init | |
| parent | c30724e9a061135f8c7b925c0fcdf742510a3bc5 (diff) | |
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 <linux@rasmusvillemoes.dk>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Diffstat (limited to 'init')
| -rw-r--r-- | init/Kconfig | 3 |
1 files changed, 3 insertions, 0 deletions
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 |