Re: PA specifies invalid T_ADAFLAGS

[law@redhat.com]

In message <200204261635.g3QGZ7bW026408@hiauly1.hia.nrc.ca>, "John David Anglin
" writes:
 > >  > I suspect using "-mdisable-indexing" dates from a time when indexing
 > >  > didn't work very well.  This was reworked a year or two ago.
 > > No.  The semantics of Ada don't play well with the funky implicit space 
 > > register
 > > selection done on PAs.  -mdisable-indexing is really needed for Ada.
 > 
 > Yes.  I am testing a patch to correct the configuration regression
 > introduced last fall.  I had my first successful build of ada last
 > night under hpux with gcc 3.1.
Actually, I forgot, there is a way we could get rid of -mdisable-indexing
completely (without totally removing indexing :-)

Basically we would only do indexing when we can prove that we have a 
"pure pointer"; where "pure pointer" means that we have a pointer that
we know points to a location within its object.  We largely have this
with REGNO_POINTER_FLAG, but if I recall properly it gets set sometimes when
it shouldn't.  We'd also need a reasonable way to propagage REGNO_POINTER_FLAG
to other pointer references (the code in regclass is painfully inadequate).

Anyway, once we have "pure pointers" identified & marked, then we only 
allow indexing on the pure pointer.

Moving REGNO_POINTER_FLAG out of its separate array and into the register RTL
structure itself was one of the key first steps (so that we can safely examine
it during assembly output).

The next step would be to review generation of REGNO_POINTER_FLAG to ensure
it's only generated for pure pointers.  Then we can twiddle the backend to 
use it, then we can write a pass to propagage REGNO_POINTER_FLAG so that it's
more aggressively set.

jeff