[COMMITTED] Do not call range_on_path_entry for SSAs defined within the path

  In the path solver, when requesting the range of an SSA for which we
know nothing, we ask the ranger for the range incoming to the path.
We do this by asking for all the incoming ranges to the path entry
block and unioning them.

The problem here is that we're asking for a range on path entry for an
SSA which *is* defined in the path, but for which we know nothing
about:

	some_global.1_2 = some_global;
	_3 = (char) some_global.1_2;

This request is causing us to ask for range_on_edge of _3 on the
incoming edges to the path.  This is a bit of nonsensical request
because _3 isn't live on entry to the path, so ranger correctly
returns UNDEFINED.  The proper thing is to avoid asking this in the
first place.

I have added a relevant assert, since it doesn't make sense to call
range_on_path_entry for SSAs defined within the path.

Tested on x86-64 Linux.

	PR 102736

gcc/ChangeLog:

	PR tree/optimization/102736
	* gimple-range-path.cc (path_range_query::range_on_path_entry):
	Assert that the requested range is defined outside the path.
	(path_range_query::ssa_range_in_phi): Do not call
	range_on_path_entry for SSA names that are defined within the
	path.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr102736.c: New test.
---
 gcc/gimple-range-path.cc                 |  6 +++++-
 gcc/testsuite/gcc.dg/tree-ssa/pr102736.c | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
  

On 14/10/2021 14:21, Aldy Hernandez via Gcc-patches wrote:
> In the path solver, when requesting the range of an SSA for which we
> know nothing, we ask the ranger for the range incoming to the path.
> We do this by asking for all the incoming ranges to the path entry
> block and unioning them.
>
> The problem here is that we're asking for a range on path entry for an
> SSA which *is* defined in the path, but for which we know nothing
> about:
>
> 	some_global.1_2 = some_global;
> 	_3 = (char) some_global.1_2;
>
> This request is causing us to ask for range_on_edge of _3 on the
> incoming edges to the path.  This is a bit of nonsensical request
> because _3 isn't live on entry to the path, so ranger correctly
> returns UNDEFINED.  The proper thing is to avoid asking this in the
> first place.
>
> I have added a relevant assert, since it doesn't make sense to call
> range_on_path_entry for SSAs defined within the path.
>
> Tested on x86-64 Linux.
>
> 	PR 102736
>
> gcc/ChangeLog:
>
> 	PR tree/optimization/102736
> 	* gimple-range-path.cc (path_range_query::range_on_path_entry):
> 	Assert that the requested range is defined outside the path.
> 	(path_range_query::ssa_range_in_phi): Do not call
> 	range_on_path_entry for SSA names that are defined within the
> 	path.
>
> gcc/testsuite/ChangeLog:
>
> 	* gcc.dg/tree-ssa/pr102736.c: New test.
> ---
>   gcc/gimple-range-path.cc                 |  6 +++++-
>   gcc/testsuite/gcc.dg/tree-ssa/pr102736.c | 21 +++++++++++++++++++++
>   2 files changed, 26 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
>
> diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
> index 422abfddb8f..694271306a7 100644
> --- a/gcc/gimple-range-path.cc
> +++ b/gcc/gimple-range-path.cc
> @@ -134,6 +134,7 @@ path_range_query::defined_outside_path (tree name)
>   void
>   path_range_query::range_on_path_entry (irange &r, tree name)
>   {
> +  gcc_checking_assert (defined_outside_path (name));
>     int_range_max tmp;
>     basic_block entry = entry_bb ();
>     bool changed = false;
> @@ -258,7 +259,10 @@ path_range_query::ssa_range_in_phi (irange &r, gphi *phi)
>   		// Using both the range on entry to the path, and the
>   		// range on this edge yields significantly better
>   		// results.
> -		range_on_path_entry (r, arg);
> +		if (defined_outside_path (arg))
> +		  range_on_path_entry (r, arg);
> +		else
> +		  r.set_varying (TREE_TYPE (name));
>   		m_ranger.range_on_edge (tmp, e_in, arg);
>   		r.intersect (tmp);
>   		return;
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c b/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> new file mode 100644
> index 00000000000..7e556f01a86
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> @@ -0,0 +1,21 @@
> +// { dg-do run }
> +// { dg-options "-O1 -ftree-vrp" }
> +
> +int a, b = -1, c;
> +int d = 1;
> +static inline char e(char f, int g) { return g ? f : 0; }
> +static inline char h(char f) { return f < a ? f : f < a; }
> +static inline unsigned char i(unsigned char f, int g) { return g ? f : f > g; }
> +void j() {
> +L:
> +  c = e(1, i(h(b), d));
> +  if (b)
> +    return;
> +  goto L;
> +}
> +int main() {
> +  j();
> +  if (c != 1)
> +    __builtin_abort ();
> +  return 0;
> +}

Hi,


The new test fails at execution on arm / aarch64, not sure if you are 
aware of that already?


Thanks,

Christophe
  

It's been fixed on trunk.

Aldy

On Fri, Oct 15, 2021, 09:52 Christophe LYON via Gcc-patches <
gcc-patches@gcc.gnu.org> wrote:

>
> On 14/10/2021 14:21, Aldy Hernandez via Gcc-patches wrote:
> > In the path solver, when requesting the range of an SSA for which we
> > know nothing, we ask the ranger for the range incoming to the path.
> > We do this by asking for all the incoming ranges to the path entry
> > block and unioning them.
> >
> > The problem here is that we're asking for a range on path entry for an
> > SSA which *is* defined in the path, but for which we know nothing
> > about:
> >
> >       some_global.1_2 = some_global;
> >       _3 = (char) some_global.1_2;
> >
> > This request is causing us to ask for range_on_edge of _3 on the
> > incoming edges to the path.  This is a bit of nonsensical request
> > because _3 isn't live on entry to the path, so ranger correctly
> > returns UNDEFINED.  The proper thing is to avoid asking this in the
> > first place.
> >
> > I have added a relevant assert, since it doesn't make sense to call
> > range_on_path_entry for SSAs defined within the path.
> >
> > Tested on x86-64 Linux.
> >
> >       PR 102736
> >
> > gcc/ChangeLog:
> >
> >       PR tree/optimization/102736
> >       * gimple-range-path.cc (path_range_query::range_on_path_entry):
> >       Assert that the requested range is defined outside the path.
> >       (path_range_query::ssa_range_in_phi): Do not call
> >       range_on_path_entry for SSA names that are defined within the
> >       path.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * gcc.dg/tree-ssa/pr102736.c: New test.
> > ---
> >   gcc/gimple-range-path.cc                 |  6 +++++-
> >   gcc/testsuite/gcc.dg/tree-ssa/pr102736.c | 21 +++++++++++++++++++++
> >   2 files changed, 26 insertions(+), 1 deletion(-)
> >   create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> >
> > diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
> > index 422abfddb8f..694271306a7 100644
> > --- a/gcc/gimple-range-path.cc
> > +++ b/gcc/gimple-range-path.cc
> > @@ -134,6 +134,7 @@ path_range_query::defined_outside_path (tree name)
> >   void
> >   path_range_query::range_on_path_entry (irange &r, tree name)
> >   {
> > +  gcc_checking_assert (defined_outside_path (name));
> >     int_range_max tmp;
> >     basic_block entry = entry_bb ();
> >     bool changed = false;
> > @@ -258,7 +259,10 @@ path_range_query::ssa_range_in_phi (irange &r, gphi
> *phi)
> >               // Using both the range on entry to the path, and the
> >               // range on this edge yields significantly better
> >               // results.
> > -             range_on_path_entry (r, arg);
> > +             if (defined_outside_path (arg))
> > +               range_on_path_entry (r, arg);
> > +             else
> > +               r.set_varying (TREE_TYPE (name));
> >               m_ranger.range_on_edge (tmp, e_in, arg);
> >               r.intersect (tmp);
> >               return;
> > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> > new file mode 100644
> > index 00000000000..7e556f01a86
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr102736.c
> > @@ -0,0 +1,21 @@
> > +// { dg-do run }
> > +// { dg-options "-O1 -ftree-vrp" }
> > +
> > +int a, b = -1, c;
> > +int d = 1;
> > +static inline char e(char f, int g) { return g ? f : 0; }
> > +static inline char h(char f) { return f < a ? f : f < a; }
> > +static inline unsigned char i(unsigned char f, int g) { return g ? f :
> f > g; }
> > +void j() {
> > +L:
> > +  c = e(1, i(h(b), d));
> > +  if (b)
> > +    return;
> > +  goto L;
> > +}
> > +int main() {
> > +  j();
> > +  if (c != 1)
> > +    __builtin_abort ();
> > +  return 0;
> > +}
>
> Hi,
>
>
> The new test fails at execution on arm / aarch64, not sure if you are
> aware of that already?
>
>
> Thanks,
>
> Christophe
>
>
>