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

[Sodagudi Prasad]

On 2017-06-22 02:43, Mark Rutland wrote:
> On Tue, Jun 20, 2017 at 04:12:32PM -0700, David Rientjes wrote:
> > On Tue, 20 Jun 2017, Mark Rutland wrote:
> >
> > > As with my reply to David, my preference would be that we:
> > >
> > > 1) Align compiler-clang.h with the compiler-gcc.h inlining behaviour, so
> > >    that things work by default.
> > >
> > > 2) Fix up the arm64 core code (and drivers for architected / common
> > >    peripherals) to use __always_inline where we always require inlining.
> > >
> > > 3) Have arm64 select CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING, and have
> > >    people test-build configurations with CONFIG_OPTIMIZE_INLINING, with
> > >    both GCC and clang.
> > >
> > > 4) Fix up drivers, etc, as appropriate.
> > >
> > > 5) Once that's largely stable, and if there's a benefit, have arm64
> > >    select CONFIG_OPTIMIZE_INLINING by default.
> > >
> > > That should avoid undue breakage, while enabling this ASAP.
> > >
> >
> > Sounds good, but I think we should simply deal with the
> > __attribute__((unused)) needed for clang as part of compiler-gcc.h by
> > simply adding it to the inline override there to avoid duplicated 
> > code.
>
> Agreed. That looks much better.
>
> Thanks,
> Mark.
>
> > diff --git a/include/linux/compiler-clang.h 
> > b/include/linux/compiler-clang.h
> > --- a/include/linux/compiler-clang.h
> > +++ b/include/linux/compiler-clang.h
> > @@ -15,11 +15,3 @@
> >   * with any version that can compile the kernel
> >   */
> >  #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), 
> > __COUNTER__)
> > -
> > -/*
> > - * GCC does not warn about unused static inline functions for
> > - * -Wunused-function.  This turns out to avoid the need for complex 
> > #ifdef
> > - * directives.  Suppress the warning in clang as well.
> > - */
> > -#undef inline
> > -#define inline inline __attribute__((unused)) notrace
> > diff --git a/include/linux/compiler-gcc.h 
> > b/include/linux/compiler-gcc.h
> > index 0efef9cf014f..71fe0994cf1a 100644
> > --- a/include/linux/compiler-gcc.h
> > +++ b/include/linux/compiler-gcc.h
> > @@ -66,18 +66,22 @@
> >
> >  /*
> >   * Force always-inline if the user requests it so via the .config,
> > - * or if gcc is too old:
> > + * or if gcc is too old.
> > + * GCC does not warn about unused static inline functions for
> > + * -Wunused-function.  This turns out to avoid the need for complex 
> > #ifdef
> > + * directives.  Suppress the warning in clang as well by using 
> > "unused"
> > + * function attribute, which is redundant but not harmful for gcc.
> >   */
> >  #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
> >      !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
> > -#define inline		inline		__attribute__((always_inline)) notrace
> > -#define __inline__	__inline__	__attribute__((always_inline)) notrace
> > -#define __inline	__inline	__attribute__((always_inline)) notrace
> > +#define inline inline		__attribute__((always_inline,unused)) notrace
> > +#define __inline__ __inline__	__attribute__((always_inline,unused)) 
> > notrace
> > +#define __inline __inline	__attribute__((always_inline,unused)) 
> > notrace
> >  #else
> >  /* A lot of inline functions can cause havoc with function tracing */
> > -#define inline		inline		notrace
> > -#define __inline__	__inline__	notrace
> > -#define __inline	__inline	notrace
> > +#define inline inline		__attribute__((unused)) notrace
> > +#define __inline__ __inline__	__attribute__((unused)) notrace
> > +#define __inline __inline	__attribute__((unused)) notrace
> >  #endif
> >
> >  #define __always_inline	inline __attribute__((always_inline))
Hi David,

I just want to cross check with you.
Do you want me to update this change in next patch set ? Or are you 
going to add this ?

-Thanks, Prasad
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