[PATCH] Reset root oracle from path_oracle::reset_path.

[Andrew MacLeod]

works for me.

On 8/17/22 12:09, Aldy Hernandez wrote:
> When we cross a backedge in the path solver, we reset the path
> relations and nuke the root oracle.  However, we forget to reset it
> for the next path.  This is causing us to miss threads because
> subsequent paths will have no root oracle to use.
>
> With this patch we get 201 more threads in the threadfull passes in my
> .ii files and 118 more overall (DOM gets less because threadfull runs
> before).
>
> Normally, I'd recommend this for the GCC 12 branch, but considering
> how sensitive other passes are to jump threading, and that there is no
> PR associated with this, perhaps we should leave this out.  Up to the
> release maintainers of course.
>
> Andrew, you OK with this for trunk?
>
> gcc/ChangeLog:
>
> 	* gimple-range-path.cc
> 	(path_range_query::compute_ranges_in_block): Remove
> 	set_root_oracle call.
> 	(path_range_query::compute_ranges): Pass ranger oracle to
> 	reset_path.
> 	* value-relation.cc (path_oracle::reset_path): Set root oracle.
> 	* value-relation.h (path_oracle::reset_path): Add root oracle
> 	argument.
> ---
>   gcc/gimple-range-path.cc | 8 +++++---
>   gcc/value-relation.cc    | 6 ++++--
>   gcc/value-relation.h     | 2 +-
>   3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
> index c99d77dd340..73e248b7e0b 100644
> --- a/gcc/gimple-range-path.cc
> +++ b/gcc/gimple-range-path.cc
> @@ -435,11 +435,10 @@ path_range_query::compute_ranges_in_block (basic_block bb)
>   		 e->src->index, e->dest->index);
>   
>         path_oracle *p = get_path_oracle ();
> -      p->reset_path ();
>         // ?? Instead of nuking the root oracle altogether, we could
>         // reset the path oracle to search for relations from the top of
>         // the loop with the root oracle.  Something for future development.
> -      p->set_root_oracle (nullptr);
> +      p->reset_path ();
>       }
>   
>     gori_compute &g = m_ranger->gori ();
> @@ -615,7 +614,10 @@ path_range_query::compute_ranges (const vec<basic_block> &path,
>       compute_exit_dependencies (m_exit_dependencies, m_path);
>   
>     if (m_resolve)
> -    get_path_oracle ()->reset_path ();
> +    {
> +      path_oracle *p = get_path_oracle ();
> +      p->reset_path (m_ranger->oracle ());
> +    }
>   
>     if (DEBUG_SOLVER)
>       {
> diff --git a/gcc/value-relation.cc b/gcc/value-relation.cc
> index 3f0957ccdd6..7fc22d30126 100644
> --- a/gcc/value-relation.cc
> +++ b/gcc/value-relation.cc
> @@ -1513,11 +1513,13 @@ path_oracle::query_relation (basic_block bb, tree ssa1, tree ssa2)
>     return query_relation (bb, equiv_1, equiv_2);
>   }
>   
> -// Reset any relations registered on this path.
> +// Reset any relations registered on this path.  ORACLE is the root
> +// oracle to use.
>   
>   void
> -path_oracle::reset_path ()
> +path_oracle::reset_path (relation_oracle *oracle)
>   {
> +  set_root_oracle (oracle);
>     m_equiv.m_next = NULL;
>     bitmap_clear (m_equiv.m_names);
>     m_relations.m_head = NULL;
> diff --git a/gcc/value-relation.h b/gcc/value-relation.h
> index 77e12085eea..64884a8eea2 100644
> --- a/gcc/value-relation.h
> +++ b/gcc/value-relation.h
> @@ -242,7 +242,7 @@ public:
>     relation_kind query_relation (basic_block, tree, tree) final override;
>     relation_kind query_relation (basic_block, const_bitmap, const_bitmap)
>       final override;
> -  void reset_path ();
> +  void reset_path (relation_oracle *oracle = NULL);
>     void set_root_oracle (relation_oracle *oracle) { m_root = oracle; }
>     void dump (FILE *, basic_block) const final override;
>     void dump (FILE *) const final override;