On Wed, Oct 2, 2024 at 5:13 AM Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> The problem here is remove_unused_var is called on a name that is
> defined by a phi node but it deletes it like removing a normal statement.
> remove_phi_node should be called rather than gsi_remove for phinodes.
>
> Note there is a possibility of using simple_dce_from_worklist instead
> but that is for another day.
>
> Bootstrapped and tested on x86_64-linux-gnu.
OK (not that I like the two conflicting APIs, maybe we can work towards removing
remove_phi_node and make PHI node handling in gsi_* better)
Thanks,
Richard.
> PR tree-optimization/116922
>
> gcc/ChangeLog:
>
> * gimple-ssa-backprop.cc (remove_unused_var): Handle phi
> nodes correctly.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/torture/pr116922.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/gimple-ssa-backprop.cc | 10 ++++++++--
> gcc/testsuite/gcc.dg/torture/pr116922.c | 19 +++++++++++++++++++
> 2 files changed, 27 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/torture/pr116922.c
>
> diff --git a/gcc/gimple-ssa-backprop.cc b/gcc/gimple-ssa-backprop.cc
> index fe27ef51cdf..e3374b18138 100644
> --- a/gcc/gimple-ssa-backprop.cc
> +++ b/gcc/gimple-ssa-backprop.cc
> @@ -663,8 +663,14 @@ remove_unused_var (tree var)
> print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
> }
> gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
> - gsi_remove (&gsi, true);
> - release_defs (stmt);
> + if (gimple_code (stmt) == GIMPLE_PHI)
> + remove_phi_node (&gsi, true);
> + else
> + {
> + unlink_stmt_vdef (stmt);
> + gsi_remove (&gsi, true);
> + release_defs (stmt);
> + }
> }
>
> /* Note that we're replacing OLD_RHS with NEW_RHS in STMT. */
> diff --git a/gcc/testsuite/gcc.dg/torture/pr116922.c
> b/gcc/testsuite/gcc.dg/torture/pr116922.c
> new file mode 100644
> index 00000000000..0fcf912930f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/torture/pr116922.c
> @@ -0,0 +1,19 @@
> +/* { dg-do compile } */
> +/* { dg-additional-options "-ffast-math" } */
> +/* PR tree-optimization/116922 */
> +
> +
> +static int g;
> +
> +void
> +foo (int c, double v, double *r)
> +{
> +b:
> + do
> + v /= g - v;
> + while (c);
> + *r = v;
> +
> + double x;
> + foo (5, (double)0, &x);
> +}
> --
> 2.43.0
>
