forwprop: Don't add uses to dce list if debug statement [PR116156]
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Commit Message
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.
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_apinski@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
Comments
On Thu, Aug 1, 2024 at 10:40 PM Andrew Pinski <quic_apinski@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_apinski@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
>
On Thu, Aug 1, 2024 at 11:55 PM Richard Biener
<richard.guenther@gmail.com> wrote:
>
> On Thu, Aug 1, 2024 at 10:40 PM Andrew Pinski <quic_apinski@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
Thanks Applied to the trunk and GCC 14 branch (since it is a regression there).
Thanks,
Andrew Pinski
>
> > 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_apinski@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
> >
new file mode 100644
@@ -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;
+}
@@ -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)