New modref/ipa_modref optimization passes

[Richard Biener]

On Thu, 29 Oct 2020, Jan Hubicka wrote:

> > 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?

OK.

Thanks,
Richard.

> 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"
>  
>  
>  #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)
>