Re: GCC 3.4 and broken inlining.

[Andi Kleen <ak@muc.de>]

On Sun, Jul 11, 2004 at 01:32:18AM -0700, Andrew Morton wrote:
> Andi Kleen <ak@muc.de> wrote:
> >
> > On Sat, Jul 10, 2004 at 11:55:36PM -0700, Andrew Morton wrote:
> > > Andi Kleen <ak@muc.de> wrote:
> > > >
> > > > I guess it could be readded if the inlining heuristics were fixed,
> > > >  but even in gcc 3.5 it still looks quite bleak.
> > > 
> > > It's very simple.  For use in the kernel we don't *want* any inlining
> > > heuristics.  What we want is:
> > > 
> > > a) If the programmer says "inline", then inline it.
> > 
> > The problem is that we have a lot of "stale" inlines. Inlines that 
> > made sense a long time ago, but then people added a lot more code
> > to the function and it would be better to out line it again.
> > You should know, you seem to do this kind of out-lining most ...
> 
> We've already fixed zillions of those, and patches are accepted.  I think
> someone wrote a tool to hunt those functions down, too.

Ok, we'll see.  Fixing that would be good of course.

> > > 
> > > b) If the programmer didn't say "inline" then don't inline it.
> > > 
> > > Surely it is not hard to add a new option to gcc to provide these semantics?
> > 
> > That option is -O2 -Dinline="__attribute__((always_inline))"
> > But for some reason it was turned off for 3.4/3.5.
> > 
> 
> Please tell me that was just a bug, and it will be fixed very soon.

compiler-gcc3.h: 

#if __GNUC_MINOR__ >= 1  && __GNUC_MINOR__ < 4
# define inline         __inline__ __attribute__((always_inline))
# define __inline__     __inline__ __attribute__((always_inline))
# define __inline       __inline__ __attribute__((always_inline))
#endif

iirc the problem was that gcc errors now out when a function
marked like this cannot be inlined for some reason.

-Andi