Re: [PATCH] compiler, clang: Add always_inline attribute to inline

From: Sodagudi Prasad
Date: Mon Jun 19 2017 - 17:14:32 EST

On 2017-06-19 13:25, David Rientjes wrote:
On Mon, 19 Jun 2017, Prasad Sodagudi wrote:

Commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused
static inline functions") re-defining the 'inline' macro but
__attribute__((always_inline)) is missing. Some compilers may
not honor inline hint if always_iniline attribute not there.
So add always_inline attribute to inline as done by
compiler-gcc.h file.

IIUC, __attribute__((always_inline)) was only needed for gcc versions < 4
and that the inlining decision making is improved in >= 4. To make a
change like this, I would think that we would need to show that clang is
making suboptimal decisions. I don't think there's a downside to making
CONFIG_OPTIMIZE_INLINING specific only to gcc.

If it is shown that __attribute__((always_inline)) is needed for clang as
well, this should be done as part of compiler-gcc.h to avoid duplicated

Hi David,

Here is the discussion about this change -
Please check mark and will's comments.

-Thanks, Prasad

Signed-off-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
include/linux/compiler-clang.h | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index d614c5e..deb65b3 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -22,4 +22,9 @@
* directives. Suppress the warning in clang as well.
#undef inline
+#define inline inline __attribute__((always_inline)) __attribute__((unused)) notrace
#define inline inline __attribute__((unused)) notrace

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