inlining default

[Joe Buck]

> >> It seems that Neil's 2001-11-15 changes to option parsing had a side
> >> effect of turning on tree inlining at -O0 for C and C++ unless suppressed
> >> with -fno-inline, because we now set flag_tree_inline from flag_no_inline
> >> before setting flag_no_inline from optimize.  Is this what we want?  I
> >> would prefer to leave it off by default with -O0, but many compilers turn
> >> it on unless specifically disabled.  What do other people think?
> 
> Mark> I think we should leave it off at -O0.  I can't see a compelling
> Mark> reason to change our historical practice.

David Edelsohn writes:

> 	Without inlining a -O0, GCC fundamentally uses a different source
> stream with and without optimization.  This makes debugging at -O0 more
> difficult. 

David, I've been debugging g++-emitted code for about 11 years now, and
it feels quite natural to me.  I'd be irritated if the default changed,
as every Makefile I have would need to be changed.  Debugging is much more
difficult if the functions specified inline are inlined.

However, now that inlining is possible at -O0, you have the option of
specifying a flag to make it happen.  But what's important is that we
should not ask the users to change their Makefiles to avoid a change in
behavior that many would find undesirable.