Re: [PATCH] Fix PR 108582: ICE due to PHI-OPT removing a still in use ssa_name.

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

On Sat, Jan 28, 2023 at 11:25 PM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch adds a check in match_simplify_replacement to make sure the middlebb
> does not have any phi-nodes as we don't currently move those.
> This was just a thinko from before.
>
> Ok? Bootstrapped and tested on x86_64-linux-gnu with no regressions?

OK.

>         PR tree-optimization/108582
>
> gcc/ChangeLog:
>
>         * tree-ssa-phiopt.cc (match_simplify_replacement): Add check
>         for middlebb to have no phi nodes.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/pr108582-1.c: New test.
> ---
>  gcc/testsuite/gcc.dg/pr108582-1.c | 58 +++++++++++++++++++++++++++++++
>  gcc/tree-ssa-phiopt.cc            |  5 +++
>  2 files changed, 63 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/pr108582-1.c
>
> diff --git a/gcc/testsuite/gcc.dg/pr108582-1.c b/gcc/testsuite/gcc.dg/pr108582-1.c
> new file mode 100644
> index 00000000000..88c2de369ad
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr108582-1.c
> @@ -0,0 +1,58 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -fno-tree-ccp -fno-tree-dce" } */
> +
> +/*
> +  PHI-OPT via match_simplify_replacement used to transform:
> +  if (_25 != 0)
> +    goto <bb 8>; [25.00%]
> +  else
> +    goto <bb 9>; [75.00%]
> +
> +  <bb 8> [local count: 11649864]:
> +  # iftmp.5_13 = PHI <2(7)>
> +  k_22 = k_11 | iftmp.5_13;
> +
> +  <bb 9> [local count: 105655256]:
> +  # g_9 = PHI <1(2), 0(8), g_8(7)>
> +  # k_12 = PHI <k_20(D)(2), k_22(8), k_11(7)>
> +
> +into:
> +
> +  _15 = (int) _25;
> +  _28 = -_15;
> +  _4 = _13 & _28;
> +  _6 = _4 | k_11;
> +
> +  <bb 8> [local count: 105655256]:
> +  # g_9 = PHI <1(2), g_8(7)>
> +  # k_12 = PHI <k_20(D)(2), _6(7)>
> +
> +Removing the phi-node/assignment of _13.
> +
> + */
> +
> +int a, c, d, e, f;
> +char b;
> +int main() {
> +  int g = 1;
> +  char h[1] = {0};
> +  while (a) {
> +    if (f) {
> +      b = 0;
> +      if (d)
> +        continue;
> +    }
> +    if (a < 1) {
> +      g = 0;
> +      goto L;
> +    }
> +  }
> +  while (c) {
> +    char *j = h;
> +    int k;
> +  L:
> +    if (e && !g)
> +      k |= 2 | (*j < 0);
> +  }
> +  return 0;
> +}
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index c3a889dc593..a7ab6ce4ad9 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -1002,6 +1002,11 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
>        if (!single_pred_p (middle_bb))
>         return false;
>
> +      /* The middle bb cannot have phi nodes as we don't
> +        move those assignments yet. */
> +      if (!gimple_seq_empty_p (phi_nodes (middle_bb)))
> +       return false;
> +
>        stmt_to_move = last_and_only_stmt (middle_bb);
>        if (!stmt_to_move)
>         return false;
> --
> 2.31.1
>