Re: [PATCH] middle-end, v4: IFN_ASSUME support [PR106654]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

On Tue, Oct 18, 2022 at 05:31:58PM -0400, Andrew MacLeod wrote:
> Anyway, gives you something to experiement with.   If you would find a
> different interface useful, let me know, or if there are limitations or
> other expansions we might need.   This seems like something reasonable for
> you to start working with?

Thanks for working on this.

> +  // Look for ASSUME calls, and call query_assume_call for each argument
> +  // to determine if there is any inferred range to be had.
> +  if (is_a<gcall *> (s) && gimple_call_internal_p (s)
> +      && gimple_call_internal_fn (s) == IFN_ASSUME)
> +    {
> +      tree assume_id = gimple_call_arg (s, 0);
> +      for (unsigned i = 1; i < gimple_call_num_args (s); i++)
> +	{
> +	  tree op = gimple_call_arg (s, i);
> +	  tree type = TREE_TYPE (op);
> +	  if (gimple_range_ssa_p (op) && Value_Range::supports_type_p (type))
> +	    {
> +	      Value_Range assume_range (type);
> +	      if (query_assume_call (assume_range, assume_id, op))
> +		{
> +		  add_range (op, assume_range);
> +		  if (dump_file)
> +		    {
> +		      print_generic_expr (dump_file, assume_id, TDF_SLIM);
> +		      fprintf (dump_file, " assume inferred range of ");
> +		      print_generic_expr (dump_file, op, TDF_SLIM);
> +		      fprintf (dump_file, " to ");
> +		      assume_range.dump (dump_file);
> +		      fputc ('\n', dump_file);
> +		    }
> +		}

Not sure I understand this part.  op is whatever we pass as the ith
argument to IFN_ASSUME.  I'd expect that at this point one needs to
remap that to the (i-1)th PARM_DECL of assume_id (so e.g. when you
have the above loop you could as well start with DECL_ARGUMENTS and move
that to DECL_CHAIN at the end of every iteration.  And then
query ssa_default_def (DECL_STRUCT_FUNCTION (assume_id), parm)
in each case and get global range of what that returns.

> +  for (unsigned  x= 0; x < gimple_phi_num_args (phi); x++)

  for (unsigned x = 0; ...
?

> @@ -4345,6 +4345,30 @@ execute_ranger_vrp (struct function *fun, bool warn_array_bounds_p)
>    scev_initialize ();
>    calculate_dominance_info (CDI_DOMINATORS);
>  
> +  assume_query *r2 = new assume_query ();
> +  for (unsigned i = 0; i < num_ssa_names; i++)
> +    {
> +      tree name = ssa_name (i);
> +      if (!name || !gimple_range_ssa_p (name))
> +	continue;
> +      tree type = TREE_TYPE (name);
> +      if (!Value_Range::supports_type_p (type))
> +	continue;
> +      Value_Range assume_range (type);
> +      if (r2->assume_range_p (assume_range, name))
> +	{
> +	  if (dump_file)
> +	    {
> +	      fprintf (dump_file, "for an assume function, ");
> +	      print_generic_expr (dump_file, name, TDF_SLIM);
> +	      fprintf (dump_file, " would have a range of ");
> +	      assume_range.dump (dump_file);
> +	      fputc ('\n', dump_file);
> +	    }
> +	}
> +    }
> +  delete r2;

I have expected (but tell me if that isn't possible) this could be something
done in the new pass_assumptions::execute () rather than vrp and you'd
create the assume_query there (i.e. just for assume_functions) and then
query it solely for ssa_default_def of the parameters and save in
SSA_NAME_RANGE_INFO.

But my knowledge about ranger is fairly limited...

	Jakub