Re: [PATCH, 4/16] Implement -foffload-alias

[Jakub Jelinek <jakub@redhat.com>]

On Fri, Nov 27, 2015 at 01:03:52PM +0100, Tom de Vries wrote:
> Handle non-declared variables in kernels alias analysis
> 
> 2015-11-27  Tom de Vries  <tom@codesourcery.com>
> 
> 	* gimplify.c (gimplify_scan_omp_clauses): Initialize
> 	OMP_CLAUSE_ORIG_DECL.
> 	* omp-low.c (install_var_field_1): Handle base_pointers_restrict for
> 	pointers.
> 	(map_ptr_clause_points_to_clause_p)
> 	(nr_map_ptr_clauses_pointing_to_clause): New function.
> 	(omp_target_base_pointers_restrict_p): Handle GOMP_MAP_POINTER.
> 	* tree-pretty-print.c (dump_omp_clause): Print OMP_CLAUSE_ORIG_DECL.
> 	* tree.c (omp_clause_num_ops): Set num_ops for OMP_CLAUSE_MAP to 3.
> 	* tree.h (OMP_CLAUSE_ORIG_DECL): New macro.
> 
> 	* c-c++-common/goacc/kernels-alias-10.c: New test.
> 	* c-c++-common/goacc/kernels-alias-9.c: New test.

I don't like this (mainly the addition of OMP_CLAUSE_ORIG_DECL),
but it also sounds wrong to me.
The primary question is how do you handle GOMP_MAP_POINTER
(which is something we don't use for C/C++ OpenMP anymore,
and Fortran OpenMP will stop using it in GCC 7 or 6.2?) on the OpenACC
libgomp side, does it work like GOMP_MAP_ALLOC or GOMP_MAP_FORCE_ALLOC?
Similarly GOMP_MAP_TO_PSET.  If it works like GOMP_MAP_ALLOC (it does
on the OpenMP side in target.c, so if something is already mapped, no
further pointer assignment happens), then your change looks wrong.
If it works like GOMP_MAP_FORCE_ALLOC, then you just should treat
GOMP_MAP_POINTER on all OpenACC constructs as opcode that allows the
restrict operation.  If it should behave differently depending on
if the corresponding array section has been mapped with GOMP_MAP_FORCE_*
or without it, then supposedly you should use a different code for
those two.

	Jakub