Re: New modref/ipa_modref optimization passes

[Jan Hubicka <hubicka@ucw.cz>]

> Hi,
> this is patch I am using to fix the assumed_alias_type.f90 failure by
> simply arranging alias set 0 for the problematic array descriptor.
> 
> I am not sure this is the best option, but I suppose it is better than
> setting all array descritors to have same canonical type (as done by
> LTO)?
> 
Hi,
here is updated patch which used TYPELESS_STORAGE instead of alias set
0, so it is LTO safe.  Unforunately I also had to enable it for all
array descriptors otherwise I still get misopitmizations with modref
extended to handle bulitins, for example:

FAIL: gfortran.dg/class_array_20.f03   -Os  execution test
FAIL: gfortran.dg/coindexed_1.f90   -O2  execution test
FAIL: gfortran.dg/coindexed_1.f90   -O3 -fomit-frame-pointer
FAIL: gfortran.dg/coindexed_1.f90   -O3 -g  execution test

This is not a perfect solution (we really want to track array
descriptors), but it fixes wrong code and would let me to move forward.
Is it OK for mainline?

With extended modref I still get infinite loop on pdt_14 testcase.
ipa-modref only performs disambiguation on
__vtab_link_module_Pdtlink_8._deallocate this global variable is
readonly (and is detected as such with LTO) so it must be just
uncovering some latent problem there.  I am however not familiar enough
with Fortran to tell what is wrong there.

The testcase fail different way with -flto for me.

Bootstrapped/regtested x86_64-linux, OK?

Honza

	* trans-types.c: Include alias.h
	(gfc_get_array_type_bounds): Set typeless storage.
diff --git a/gcc/fortran/trans-types.c b/gcc/fortran/trans-types.c
index b15ea667411..b7129dcbe6d 100644
--- a/gcc/fortran/trans-types.c
+++ b/gcc/fortran/trans-types.c
@@ -38,6 +38,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "trans-array.h"
 #include "dwarf2out.h"	/* For struct array_descr_info.  */
 #include "attribs.h"
+#include "alias.h"
 \f
 
 #if (GFC_MAX_DIMENSIONS < 10)
@@ -1903,6 +1904,10 @@ gfc_get_array_type_bounds (tree etype, int dimen, int codimen, tree * lbound,
   base_type = gfc_get_array_descriptor_base (dimen, codimen, false);
   TYPE_CANONICAL (fat_type) = base_type;
   TYPE_STUB_DECL (fat_type) = TYPE_STUB_DECL (base_type);
+  /* Arrays of unknown type must alias with all array descriptors.  */
+  TYPE_TYPELESS_STORAGE (base_type) = 1;
+  TYPE_TYPELESS_STORAGE (fat_type) = 1;
+  gcc_checking_assert (!get_alias_set (base_type) && !get_alias_set (fat_type));
 
   tmp = TYPE_NAME (etype);
   if (tmp && TREE_CODE (tmp) == TYPE_DECL)