On Wed, Nov 13, 2013 at 11:27:10AM +0100, Richard Biener wrote:
> > Also, I wonder if we couldn't defer the expensive ira_init, if the info
> > computed by it is used only during RTL optimization passes (haven't verified
> > it yet), then supposedly we could just remember using some target hook
> > what the last state was when we did ira_init last time, and call ira_init
> > again at the start of expansion or so if it is different from the last time.
> > For i?86/x86_64/ppc* this would be whether the current function's
> > DECL_FUNCTION_SPECIFIC_TARGET is the same as one for which ira_init has been
> > called, for rx whether interrupt attribute is the same and for mips whatever
> > is needed.
>
> I wonder why we cannot move all the stuff we re-init to a member
> of struct function (or rather have a pointer to that info there
> to cache it across functions with the same options). That is,
> get rid of more global state? That would make switching back
> and forth cheaper.
Isn't that what the SWITCHABLE_TARGET stuff is all about?
So, perhaps we should just define SWITCHABLE_TARGET on i?86/x86_64/powerpc*
(and rx if maintainer cares) and tweak it to attach somehow
struct target_globals * to TARGET_OPTION_NODE somehow.
A problem might be that lots of the save_target_globals
allocated structures are heap allocated rather than GC, so we might leak
memory. Wonder if save_target_globals couldn't just compute the
aggregate size of all the structures it allocates with XCNEW right now
(plus required alignment if needed) and just allocate them together
with the ggc_alloc_target_globals after the target_globals structure
itself.
Jakub
