cvs commit: src/sys/kern init_main.c kern_malloc.c md5c.c subr_autoconf.c subr_mbuf.c subr_prf.c tty_subr.c vfs_cluster.c vfs_subr.c

[Peter Wemm]

Marcel Moolenaar wrote:
> On Tue, Jul 22, 2003 at 01:54:16PM -0500, Alan L. Cox wrote:
> > > 
> > > `-finline-limit=N'
> > >      By default, gcc limits the size of functions that can be inlined.
> > >      This flag allows the control of this limit for functions that are
> > >      explicitly marked as inline (i.e., marked with the inline keyword
> > >      or defined within the class definition in c++).  N is the size of
> > >      functions that can be inlined in number of pseudo instructions
> > >      (not counting parameter handling).  The default value of N is 600.
> > >      Increasing this value can result in more inlined code at the cost
> > >      of compilation time and memory consumption.  Decreasing usually
> > > 
> > 
> > There is another way.  The following example illustrates its use.
> > 
> > static int    vm_object_backing_scan(vm_object_t object, int op)
> > __attribute__((always_inline));
> 
> I hope we can come up with a scheme that allows us to control
> inlining on a per-platform basis. Current events demonstrate
> pretty good how people treat optimizations (which inlining is)
> as machine independent fodder and how easy it is to generalize
> beyond sensibility.
> Unfortunately, the use of an expression-like syntax (inline or
> __attribute__ keyword) makes this harder than with a statement-
> like syntax (like #pragma), because of the 2-D space (platforms
> vs functions).

Sure, but we're also limited by what the compiler provides.  gcc should
probably provide #pragma hooks as a way to set the equivalent of things
like 'cc --param max-inline-insns-single=2400', but as far as I'm aware,
it doesn't.

For what its worth, if we use __attribute__((always_inline)), it should
be #define __always_inline__ __attribute__((__always_inline__)) and
declare functions as  int foo(int bar) __always_inline__;  so that we
can avoid embedding more gcc-isms in such a way that isn't trivial to
#define away.

Cheers,
-Peter
--
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com
"All of this is for nothing if we don't go to the stars" - JMS/B5