[PATCH] Copy over TREE_THIS_VOLATILE during forwprop (PR tree-optimization/50078)

[Jakub Jelinek]

On Mon, Nov 28, 2011 at 12:16:45PM -0700, Jeff Law wrote:
> > On the following testcase the volatile load/store are optimized
> > away. IMHO this is a bug in forwprop, which replaces tmp_Y =
> > &nonvolvar[arg_X]; MEM[(volatile ...*)tmp_Y] ={v} ...; with 
> > MEM[(volatile ...*)&nonvolvar][tmp_Y] ={v} ...; where the LHS is no
> > longer TREE_THIS_VOLATILE like before, TREE_THIS_VOLATILE is newly
> > only the MEM_REF operand of the non-volatile ARRAY_REF.  This patch
> > copies the TREE_THIS_VOLATILE bit to the ARRAY_REF.
> > 
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> > trunk?
> > 
> > 2011-11-28  Jakub Jelinek  <jakub@redhat.com>
> > 
> > PR tree-optimization/50078 * tree-ssa-forwprop.c
> > (forward_propagate_addr_expr_1): Copy over TREE_THIS_VOLATILE also
> > from the old to new lhs resp. rhs.
> > 
> > * gcc.dg/pr50078.c: New test.
> Do we need to copy NOTRAP or any of the other flags?
> 
> OK, assuming we don't need to copy NOTRAP, etc.  If those need to be
> copied too, preapproved with those changes.

I had there TREE_THIS_NOTRAP as well in the first iteration, but
it ICEd, as TREE_THIS_NOTRAP is not valid e.g. on COMPONENT_REF.

	Jakub