Re: [PATCH 3/12] phiopt: Fix phiopt ICE on vops [PR102989]

[Andrew Pinski <pinskia@gmail.com>]

On Wed, Aug 9, 2023 at 11:17 AM Jakub Jelinek via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Hi!
>
> I've ran into ICE on gcc.dg/torture/bitint-42.c with -O1 or -Os
> when enabling expensive tests, and unfortunately I can't reproduce without
> _BitInt.  The IL before phiopt3 has:
>   <bb 87> [local count: 203190070]:
>   # .MEM_428 = VDEF <.MEM_367>
>   bitint.159 = VIEW_CONVERT_EXPR<unsigned long[8]>(*.LC3);
>   goto <bb 89>; [100.00%]
>
>   <bb 88> [local count: 203190070]:
>   # .MEM_427 = VDEF <.MEM_367>
>   bitint.159 = VIEW_CONVERT_EXPR<unsigned long[8]>(*.LC4);
>
>   <bb 89> [local count: 406380139]:
>   # .MEM_368 = PHI <.MEM_428(87), .MEM_427(88)>
>   # VUSE <.MEM_368>
>   _123 = VIEW_CONVERT_EXPR<unsigned long[8]>(r495[i_107].D.2780)[0];
> and factor_out_conditional_operation is called on the vop PHI, it
> sees it has exactly two operands and defining statements of both
> PHI arguments are converts (VCEs in this case), so it thinks it is
> a good idea to try to optimize that and while doing that it constructs
> void type SSA_NAMEs and the like.

Maybe it is better to punt for VOPS after the call to
single_non_singleton_phi_for_edges since none of functions called
afterwards support VOPs.
That is something like:
diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
index ff36bb0119b..d0b659042a7 100644
--- a/gcc/tree-ssa-phiopt.cc
+++ b/gcc/tree-ssa-phiopt.cc
@@ -4165,6 +4165,10 @@ pass_phiopt::execute (function *)
       arg0 = gimple_phi_arg_def (phi, e1->dest_idx);
       arg1 = gimple_phi_arg_def (phi, e2->dest_idx);

+      /* Can't do anything with a VOP here.  */
+      if (SSA_NAME_IS_VIRTUAL_OPERAND (arg0))
+       continue;
+
       /* Something is wrong if we cannot find the arguments in the PHI
          node.  */
       gcc_assert (arg0 != NULL_TREE && arg1 != NULL_TREE);

Thanks,
Andrew Pinski

>
> 2023-08-09  <jakub@redhat.com>
>
>         PR c/102989
>         * tree-ssa-phiopt.cc (factor_out_conditional_operation): Punt for
>         vops.
>
> --- gcc/tree-ssa-phiopt.cc.jj   2023-08-08 15:55:09.508122417 +0200
> +++ gcc/tree-ssa-phiopt.cc      2023-08-09 15:55:23.762314103 +0200
> @@ -241,6 +241,7 @@ factor_out_conditional_operation (edge e
>      }
>
>    if (TREE_CODE (arg0) != SSA_NAME
> +      || SSA_NAME_IS_VIRTUAL_OPERAND (arg0)
>        || (TREE_CODE (arg1) != SSA_NAME
>           && TREE_CODE (arg1) != INTEGER_CST))
>      return NULL;
>
>         Jakub
>