[PATCH] Handle aggregate pass-through for self-recursive call (PR ipa/92794)

[Martin Jambor]

Hi,

On Tue, Dec 17 2019, Feng Xue OS wrote:
> If argument for a self-recursive call is a simple pass-through, the call
> edge is also considered as source of any value originated from
> non-recursive call to the function. Scalar pass-through and full aggregate
> pass-through due to pointer pass-through have also been handled.
> But we missed another kind of pass-through like below case,  partial
> aggregate pass-through. This patch is meant to fix the problem which
> caused ICE as in 92794.
>
>   void foo(struct T *val_ptr)
>   {
>     struct T new_val;
>     new_val.field = val_ptr->field;
>     foo (&temp);
>     ...
>   }
>
> Bootstrapped/regtested on x86_64-linux and aarch64-linux.
>
> 2019-12-17  Feng Xue  <fxue@os.amperecomputing.com>
>
>         PR ipa/92794
>         * ipa-cp.c (self_recursive_agg_pass_through_p): New function.
>         (intersect_with_plats): Use error_mark_node as place holder
>         when aggregate jump function is simple pass-through for
>         self-recursive call.
>         (intersect_with_agg_replacements): Likewise.
>         (intersect_aggregates_with_edge): Likewise.
>         (find_aggregate_values_for_callers_subset): Likewise.
>
> Thanks,
> Feng
> From 42ba553ebf80eadb62619c5570a4b406f8c90c49 Mon Sep 17 00:00:00 2001
> From: Feng Xue <fxue@os.amperecomputing.com>
> Date: Mon, 16 Dec 2019 20:33:36 +0800
> Subject: [PATCH] Handle aggregate simple pass-through for self-recursive call
>
> ---
>  gcc/ipa-cp.c                       | 97 +++++++++++++++++++++++++-----
>  gcc/testsuite/gcc.dg/ipa/pr92794.c | 30 +++++++++
>  2 files changed, 111 insertions(+), 16 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/ipa/pr92794.c
>
> diff --git a/gcc/ipa-cp.c b/gcc/ipa-cp.c
> index 1a80ccbde2d..0e17fedd649 100644
> --- a/gcc/ipa-cp.c
> +++ b/gcc/ipa-cp.c
> @@ -4564,6 +4564,23 @@ self_recursive_pass_through_p (cgraph_edge *cs, ipa_jump_func *jfunc, int i)
>    return false;
>  }
>  
> +/* Return true, if JFUNC, which describes a part of an aggregate represented
> +   or pointed to by the i-th parameter of call CS, is a simple no-operation
> +   pass-through function to itself.  */
> +
> +static bool
> +self_recursive_agg_pass_through_p (cgraph_edge *cs, ipa_agg_jf_item *jfunc,
> +				   int i)
> +{
> +  if (cs->caller == cs->callee->function_symbol ()

I don't know if self-recursive calls can be interposed at all, if yes
you need to add the availability check like we have in
self_recursive_pass_through_p (if not, we should probably remove it
there).

Apart from that, I believe the patch is probably the best thing we can
do to deal with these interesting situations.

Thanks for looking into the bug,

Martin


> +      && jfunc->jftype == IPA_JF_LOAD_AGG
> +      && jfunc->offset == jfunc->value.load_agg.offset
> +      && jfunc->value.pass_through.operation == NOP_EXPR
> +      && jfunc->value.pass_through.formal_id == i)
> +    return true;
> +  return false;
> +}