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

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Oct 19, 2022 at 07:39:05PM +0200, Jakub Jelinek via Gcc-patches wrote:
> On Wed, Oct 19, 2022 at 12:55:12PM -0400, Andrew MacLeod via Gcc-patches wrote:
> > > 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.
> > 
> > OK, this is the bit of code I dont know how to write :-)
> > 
> > yes, op is the name of the value within this current function, and yes, that
> > needs to be mapped to the argument decl in the assume function.   Then we
> > need to query what range was given to that name during the assume pass. 
> > when that is returned, the add_range (op, range) will inject it as a side
> > effect.
> > 
> > Can you write that loop?
> 
> I meant something like (untested code):
>        && 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 parm = DECL_ARGUMENTS (assume_id);
> +      struct function *fun = DECL_STRUCT_FUNCTION (assume_id);
> +      for (unsigned i = 1;
> +	   i < gimple_call_num_args (s) && parm;
> +	   i++, parm = DECL_CHAIN (parm))
>  	{
>  	  tree op = gimple_call_arg (s, i);
>  	  tree type = TREE_TYPE (op);
> +	  tree arg = ssa_default_def (fun, parm);
> +	  if (arg == NULL_TREE)
> +	    continue;
>  	  if (gimple_range_ssa_p (op) && Value_Range::supports_type_p (type))
>  	    {
>  	      Value_Range assume_range (type);
> and querying SSA_NAME_RANGE_INFO of arg rather than op.

Oops, the tree arg = ... stuff would need to be moved into the if (gimple_range...)
body, it won't work for aggregate PARM_DECLs etc., only PARM_DECLs with
is_gimple_reg_type (TREE_TYPE (arg)).

	Jakub