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

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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 
code.

> Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
> ---
>  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
> +#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
> +    !defined(CONFIG_OPTIMIZE_INLINING)
> +#define inline inline __attribute__((always_inline)) __attribute__((unused)) notrace
> +#else
>  #define inline inline __attribute__((unused)) notrace
> +#endif

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Thread

Using __always_inline attribute Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-14 00:40 +0200
  Re: Using __always_inline attribute Will Deacon <will.deacon@arm.com> - 2017-06-14 12:20 +0200
    Re: Using __always_inline attribute Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-15 00:40 +0200
      Re: Using __always_inline attribute Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-15 03:00 +0200
      Re: Using __always_inline attribute Mark Rutland <mark.rutland@arm.com> - 2017-06-15 18:00 +0200
        [PATCH] compiler, clang: Add always_inline attribute to inline Prasad Sodagudi <psodagud@codeaurora.org> - 2017-06-19 18:00 +0200
          Re: [PATCH] compiler, clang: Add always_inline attribute to inline David Rientjes <rientjes@google.com> - 2017-06-19 22:30 +0200
            Re: [PATCH] compiler, clang: Add always_inline attribute to inline Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-19 23:20 +0200
              Re: [PATCH] compiler, clang: Add always_inline attribute to inline David Rientjes <rientjes@google.com> - 2017-06-19 23:50 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-20 00:20 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline Mark Rutland <mark.rutland@arm.com> - 2017-06-20 13:10 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline David Rientjes <rientjes@google.com> - 2017-06-21 01:20 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline Mark Rutland <mark.rutland@arm.com> - 2017-06-22 11:50 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline Sodagudi Prasad <psodagud@codeaurora.org> - 2017-06-23 08:50 +0200
                Re: [PATCH] compiler, clang: Add always_inline attribute to inline Mark Rutland <mark.rutland@arm.com> - 2017-06-20 13:00 +0200

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