On Thu, Aug 1, 2024 at 10:40 PM Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> The problem here is that when forwprop does a copy prop, into a statement,
> we mark the uses of that statement as possibly need to be removed. But it just
> happened that statement was a debug statement, there will be a difference when
> compiling with debuging info turned on vs off; this is not expected.
> So the fix is not to add the old use to dce list to process if it was a debug
> statement.
>
> Bootstrapped and tested on x86_64-linux-gnu with no regressions.
OK
> PR tree-optimization/116156
>
> gcc/ChangeLog:
>
> * tree-ssa-forwprop.cc (pass_forwprop::execute): Don't add
> uses if the statement was a debug statement.
>
> gcc/testsuite/ChangeLog:
>
> * c-c++-common/torture/pr116156-1.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> .../c-c++-common/torture/pr116156-1.c | 30 +++++++++++++++++++
> gcc/tree-ssa-forwprop.cc | 16 +++++-----
> 2 files changed, 39 insertions(+), 7 deletions(-)
> create mode 100644 gcc/testsuite/c-c++-common/torture/pr116156-1.c
>
> diff --git a/gcc/testsuite/c-c++-common/torture/pr116156-1.c
> b/gcc/testsuite/c-c++-common/torture/pr116156-1.c
> new file mode 100644
> index 00000000000..10f938ef4e5
> --- /dev/null
> +++ b/gcc/testsuite/c-c++-common/torture/pr116156-1.c
> @@ -0,0 +1,30 @@
> +/* { dg-additional-options "-fcompare-debug" } */
> +/* PR tree-optimization/116156 */
> +
> +/* Forwprop used to delete an unused statement
> + but only with debug statements around. */
> +
> +struct jpeg_compress_struct {
> + int X_density;
> +};
> +void gg();
> +int h(const char*,const char*) __attribute((pure));
> +int h1(const char*) __attribute((pure));
> +int f1() __attribute__((returns_twice));
> +void real_save_jpeg(char **keys, char *values) {
> + struct jpeg_compress_struct cinfo;
> + int x_density = 0;
> + while (*keys)
> + {
> + if (h1(*keys) == 0)
> + gg();
> + if (h1(*keys) == 0) {
> + if (!*values)
> + x_density = -1;
> + if (x_density <= 0)
> + gg();
> + }
> + }
> + if (f1())
> + cinfo.X_density = x_density;
> +}
> diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
> index 44a6b5d39aa..2e37642359c 100644
> --- a/gcc/tree-ssa-forwprop.cc
> +++ b/gcc/tree-ssa-forwprop.cc
> @@ -3923,7 +3923,8 @@ pass_forwprop::execute (function *fun)
> tree val = fwprop_ssa_val (use);
> if (val && val != use)
> {
> - bitmap_set_bit (simple_dce_worklist, SSA_NAME_VERSION
> (use));
> + if (!is_gimple_debug (stmt))
> + bitmap_set_bit (simple_dce_worklist, SSA_NAME_VERSION
> (use));
> if (may_propagate_copy (use, val))
> {
> propagate_value (usep, val);
> @@ -3963,12 +3964,13 @@ pass_forwprop::execute (function *fun)
> if (gimple_cond_true_p (cond)
> || gimple_cond_false_p (cond))
> cfg_changed = true;
> - /* Queue old uses for simple DCE. */
> - for (tree use : uses)
> - if (TREE_CODE (use) == SSA_NAME
> - && !SSA_NAME_IS_DEFAULT_DEF (use))
> - bitmap_set_bit (simple_dce_worklist,
> - SSA_NAME_VERSION (use));
> + /* Queue old uses for simple DCE if not debug statement. */
> + if (!is_gimple_debug (stmt))
> + for (tree use : uses)
> + if (TREE_CODE (use) == SSA_NAME
> + && !SSA_NAME_IS_DEFAULT_DEF (use))
> + bitmap_set_bit (simple_dce_worklist,
> + SSA_NAME_VERSION (use));
> }
>
> if (changed || substituted_p)
> --
> 2.43.0
>
