Re: [PATCH][ldist] Don't add lib calls with -fno-tree-loop-distribute-patterns

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Jan 31, 2022 at 5:26 PM Tom de Vries <tdevries@suse.de> wrote:
>
> [ was: Re: [RFC] ldist: Recognize rawmemchr loop patterns ]
>
> On 1/31/22 16:00, Richard Biener wrote:
> >> I'm running into PR56888 (
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888 ) on nvptx due to
> >> this, f.i. in gcc/testsuite/gcc.c-torture/execute/builtins/strlen.c,
> >> where gcc/testsuite/gcc.c-torture/execute/builtins/lib/strlen.c contains
> >> a strlen function, with a strlen loop, which is transformed by
> >> pass_loop_distribution into a __builtin_strlen, which is then expanded
> >> into a strlen call, creating a self-recursive function. [ And on nvptx,
> >> that happens to result in a compilation failure, which is how I found
> >> this. ]
> >>
> >> According to this (
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888#c21 ) comment:
> >> ...
> >> -fno-tree-loop-distribute-patterns is the reliable way to not
> >> transform loops into library calls.
> >> ...
> >>
> >> Then should we have something along the lines of:
> >> ...
> >> $ git diff
> >> diff --git a/gcc/tree-loop-distribution.c b/gcc/tree-loop-distribution.c
> >> index 6fe59cd56855..9a211d30cd7e 100644
> >> --- a/gcc/tree-loop-distribution.c
> >> +++ b/gcc/tree-loop-distribution.c
> >> @@ -3683,7 +3683,11 @@ loop_distribution::transform_reduction_loop
> >>                  && TYPE_PRECISION (ptr_type_node) >= 32)
> >>                 || (TYPE_OVERFLOW_UNDEFINED (reduction_var_type)
> >>                     && TYPE_PRECISION (reduction_var_type) <=
> >> TYPE_PRECISION (sizetype)))
> >> -         && builtin_decl_implicit (BUILT_IN_STRLEN))
> >> +         && builtin_decl_implicit (BUILT_IN_STRLEN)
> >> +         && flag_tree_loop_distribute_patterns)
> >>           generate_strlen_builtin (loop, reduction_var, load_iv.base,
> >>                                    reduction_iv.base, loc);
> >>          else if (direct_optab_handler (rawmemchr_optab, TYPE_MODE
> >> (load_type))
> >> ...
> >> ?
> >>
> >> Or is the comment no longer valid?
> >
> > It is still valid - and yes, I think we need to guard it with this flag
> > but please do it in the caller to transform_reduction_loop.
>
> Done.
>
> Ok for trunk?

OK.

> Thanks,
> - Tom