Re: [RFA][PATCH] Use SCEV conditionally within vr-values and evrp range analysis

[Richard Biener <richard.guenther@gmail.com>]

On Thu, Nov 23, 2017 at 1:16 AM, Jeff Law <law@redhat.com> wrote:
>
> Clients of the evrp range analysis may not have initialized the SCEV
> infrastructure, and in fact my not want to (DOM for example).
>
> Yet inside both vr-values.c and gimple-ssa-evrp-analyze.c we have calls
> into SCEV (that will fault/abort if SCEV is not properly initialized).
>
> This patch allows clients of vr-values.c and gimple-ssa-evrp-analyze.c
> to indicate if they want SCEV analysis.
>
> Bootstrapped and regression tested by itself as well as with the DOM
> patches to use EVRP analysis  (which test the "don't want SCEV path).
>
> OK for the trunk?

There's also scev_initialized_p () which you could conveniently use.

Richard.

>
> Jeff
>
>         * gimple-ssa-evrp-analyze.h (class evrp_range_analyzer): New data
>         member USE_SCEV.
>         * gimple-ssa-evrp-analyze.c
>         (evrp_range_analyzer::evrp_range_analyzer): Add new use_scev argument.
>         Pass it to the vr_values ctor.
>         (evrp_range_analyzer::record_ranges_from_phis): Conditionally use
>         SCEV to refine ranges for PHIs.
>         * gimple-ssa-evrp (evrp_dom_walker::evrp_dom_walker): Ask for
>         SCEV analysis in the vr-values engine.
>         * vr-values.h (class vr_values): New data meber USE_SCEV.
>         * vr-values.c (vr_values::vr_values): Add new use_scev argument.
>         (vr_values::extract_range_from_phi_node): Conditionally use
>         SCEV to refine ranges for PHIs.
>
>
> diff --git a/gcc/gimple-ssa-evrp-analyze.c b/gcc/gimple-ssa-evrp-analyze.c
> index 68a2cdc..bc41be1 100644
> --- a/gcc/gimple-ssa-evrp-analyze.c
> +++ b/gcc/gimple-ssa-evrp-analyze.c
> @@ -42,7 +42,8 @@ along with GCC; see the file COPYING3.  If not see
>  #include "vr-values.h"
>  #include "gimple-ssa-evrp-analyze.h"
>
> -evrp_range_analyzer::evrp_range_analyzer () : stack (10)
> +evrp_range_analyzer::evrp_range_analyzer (bool use_scev_)
> +  : vr_values (use_scev_), stack (10), use_scev (use_scev_)
>  {
>    edge e;
>    edge_iterator ei;
> @@ -176,7 +177,8 @@ evrp_range_analyzer::record_ranges_from_phis (basic_block bb)
>              to use VARYING for them.  But we can still resort to
>              SCEV for loop header PHIs.  */
>           struct loop *l;
> -         if (interesting
> +         if (use_scev
> +             && interesting
>               && (l = loop_containing_stmt (phi))
>               && l->header == gimple_bb (phi))
>           vr_values.adjust_range_with_scev (&vr_result, l, phi, lhs);
> @@ -341,3 +343,4 @@ evrp_range_analyzer::pop_value_range (tree var)
>    stack.pop ();
>    return vr;
>  }
> +
> diff --git a/gcc/gimple-ssa-evrp-analyze.h b/gcc/gimple-ssa-evrp-analyze.h
> index 3d64c50..18f5b8c 100644
> --- a/gcc/gimple-ssa-evrp-analyze.h
> +++ b/gcc/gimple-ssa-evrp-analyze.h
> @@ -23,7 +23,7 @@ along with GCC; see the file COPYING3.  If not see
>  class evrp_range_analyzer
>  {
>   public:
> -  evrp_range_analyzer (void);
> +  evrp_range_analyzer (bool);
>    ~evrp_range_analyzer (void) { stack.release (); }
>
>    void enter (basic_block);
> @@ -65,6 +65,9 @@ class evrp_range_analyzer
>
>    /* STACK holds the old VR.  */
>    auto_vec<std::pair <tree, value_range*> > stack;
> +
> +  /* Whether or not to use SCEV to refine ranges.  */
> +  bool use_scev;
>  };
>
>  #endif /* GCC_GIMPLE_SSA_EVRP_ANALYZE_H */
> diff --git a/gcc/gimple-ssa-evrp.c b/gcc/gimple-ssa-evrp.c
> index f56d67f..13e4e16 100644
> --- a/gcc/gimple-ssa-evrp.c
> +++ b/gcc/gimple-ssa-evrp.c
> @@ -69,6 +69,7 @@ class evrp_dom_walker : public dom_walker
>  public:
>    evrp_dom_walker ()
>      : dom_walker (CDI_DOMINATORS),
> +      evrp_range_analyzer (true),
>        evrp_folder (evrp_range_analyzer.get_vr_values ())
>      {
>        need_eh_cleanup = BITMAP_ALLOC (NULL);
> diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
> index 838822d..46be749 100644
> --- a/gcc/tree-vrp.c
> +++ b/gcc/tree-vrp.c
> @@ -4737,6 +4737,7 @@ insert_range_assertions (void)
>  class vrp_prop : public ssa_propagation_engine
>  {
>   public:
> +  vrp_prop (bool use_scev_) : vr_values (use_scev_) { }
>    enum ssa_prop_result visit_stmt (gimple *, edge *, tree *) FINAL OVERRIDE;
>    enum ssa_prop_result visit_phi (gphi *) FINAL OVERRIDE;
>
> @@ -6862,7 +6863,7 @@ execute_vrp (bool warn_array_bounds_p)
>    /* For visiting PHI nodes we need EDGE_DFS_BACK computed.  */
>    mark_dfs_back_edges ();
>
> -  class vrp_prop vrp_prop;
> +  class vrp_prop vrp_prop (true);
>    vrp_prop.vrp_initialize ();
>    vrp_prop.ssa_propagate ();
>    vrp_prop.vrp_finalize (warn_array_bounds_p);
> diff --git a/gcc/vr-values.c b/gcc/vr-values.c
> index 2d11861..54b0be5 100644
> --- a/gcc/vr-values.c
> +++ b/gcc/vr-values.c
> @@ -1907,7 +1907,8 @@ vr_values::dump_all_value_ranges (FILE *file)
>
>  /* Initialize VRP lattice.  */
>
> -vr_values::vr_values () : vrp_value_range_pool ("Tree VRP value ranges")
> +vr_values::vr_values (bool use_scev_)
> +  : vrp_value_range_pool ("Tree VRP value ranges"), use_scev (use_scev_)
>  {
>    values_propagated = false;
>    num_vr_values = num_ssa_names;
> @@ -2935,7 +2936,8 @@ scev_check:
>       scev_check can be reached from two paths, one is a fall through from above
>       "varying" label, the other is direct goto from code block which tries to
>       avoid infinite simulation.  */
> -  if ((l = loop_containing_stmt (phi))
> +  if (use_scev
> +      && (l = loop_containing_stmt (phi))
>        && l->header == gimple_bb (phi))
>      adjust_range_with_scev (vr_result, l, phi, lhs);
>
> diff --git a/gcc/vr-values.h b/gcc/vr-values.h
> index 124ee6f..bfeb1e4 100644
> --- a/gcc/vr-values.h
> +++ b/gcc/vr-values.h
> @@ -37,7 +37,7 @@ along with GCC; see the file COPYING3.  If not see
>  class vr_values
>  {
>   public:
> -  vr_values (void);
> +  vr_values (bool);
>    ~vr_values (void);
>
>    value_range *get_value_range (const_tree);
> @@ -115,6 +115,9 @@ class vr_values
>    /* Allocations for equivalences all come from this obstack.  */
>    bitmap_obstack vrp_equiv_obstack;
>
> +  /* Whether or not to use SCEV to refine ranges.  */
> +  bool use_scev;
> +
>    /* Value range array.  After propagation, VR_VALUE[I] holds the range
>       of values that SSA name N_I may take.  */
>    unsigned int num_vr_values;
>