Re: [PATCH] Fix -fcompare-debug issue in tree profiler (PR debug/46255)

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Nov 01, 2010 at 11:29:57PM +0100, Richard Guenther wrote:
> On Mon, Nov 1, 2010 at 8:21 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> > While debug stmts are never considered to need fake edges, it currently
> > (incorrectly) makes a difference whether a stmt that needs fake edges
> > was the last one or not.  Fixed by disregarding any debug stmts
> > at the end of bb.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux.  Ok for trunk?
> 
> Hmm, you mean that the stmt needing fake edges doesn't end the BB?

Yes.

> So your patch fixes that by splitting the BB at the appropriate point?

No, that was what the code was doing before and that caused the
-fcompare-debug differences, because without -g the bb was not split, with
-g it was split.
profile.c uses block_ends_with_call_p, which for gimple uses
/* Return true if BB ends with a call, possibly followed by some
   instructions that must stay with the call.  Return false,
   otherwise.  */

static bool
gimple_block_ends_with_call_p (basic_block bb)
{
  gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
  return !gsi_end_p (gsi) && is_gimple_call (gsi_stmt (gsi));
}

Having the fake edge gong not immediately from the call, but
from the end of bb where the call is followed only by debug stmts,
seems to work just fine, all it means is the profiling stuff
gets emitted before or after those debug stmts which really result in
no code being generated.

	Jakub