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Re: [PATCH] Fix PR55833 + cheaper checking
Hi,
> On Thu, Jan 10, 2013 at 11:19:43PM +0100, Zdenek Dvorak wrote:
> > I agree -- at the very least, unswitch_single_loop should check whether there
> > is any possiblity it could have affected irreducible loops information (this
> > should only be the case when some already existing irreducible loop is altered
> > in the progress). Which is what it (or more precisely, remove_path function
> > used by it) tries to do -- so is should be sufficient to check why this fails
> > for the considered testcase, and make sure the situation is correctly detected,
>
> Actually, in this case, we don't call remove_path from unswitch_single_loop
> at all.
I am not quite sure what you mean by that -- remove_path is called unconditionally
in unswitch_loop (and fix_loop_placement is only called through remove_path).
> So, here's another stab at it. In this version, we will call
> mark_irreducible_loops only in case where we're removing a loop
> from loop hierarchy tree. Because when we do that (and we're in some
> irreducible region), the edge that connects those two loops
> should be marked as EDGE_IRREDUCIBLE_LOOP. And the preheader BB
> eventually as BB_IRREDUCIBLE_LOOP. Does this look any better?
> I'm not actually checking whether we really are in a irreducible
> region, should that be done (how?)?
Yes, you should check whether you are in an irreducible loop. This is done by
testing EDGE_IRREDUCIBLE_LOOP flag,
Zdenek