[gcc r12-1546] Add recomputation to outgoing_edge_range.

[Andrew Macleod <amacleod@gcc.gnu.org>]

https://gcc.gnu.org/g:786188e8b8cab47cb31177c6f4ab1a1578a607c3

commit r12-1546-g786188e8b8cab47cb31177c6f4ab1a1578a607c3
Author: Andrew MacLeod <amacleod@redhat.com>
Date:   Wed Jun 16 18:08:03 2021 -0400

    Add recomputation to outgoing_edge_range.
    
    The gori engine can calculate outgoing ranges for exported values.  This
    change allows 1st degree recomputation.  If a name is not exported from a
    block, but one of the ssa_names used directly in computing it is, then
    we can recompute the ssa_name on the edge using the edge values for its
    operands.
    
            * gimple-range-gori.cc (gori_compute::has_edge_range_p): Check with
            may_recompute_p.
            (gori_compute::may_recompute_p): New.
            (gori_compute::outgoing_edge_range_p): Perform recomputations.
            * gimple-range-gori.h (class gori_compute): Add prototype.

Diff:
---
 gcc/gimple-range-gori.cc | 59 ++++++++++++++++++++++++++++++++++++++++++++----
 gcc/gimple-range-gori.h  |  1 +
 2 files changed, 55 insertions(+), 5 deletions(-)

diff --git a/gcc/gimple-range-gori.cc b/gcc/gimple-range-gori.cc
index 09dcd694319..647f4964769 100644
--- a/gcc/gimple-range-gori.cc
+++ b/gcc/gimple-range-gori.cc
@@ -972,16 +972,18 @@ gori_compute::compute_operand1_and_operand2_range (irange &r,
   r.intersect (op_range);
   return true;
 }
-// Return TRUE if a range can be calcalated for NAME on edge E.
+// Return TRUE if a range can be calculated or recomputed for NAME on edge E.
 
 bool
 gori_compute::has_edge_range_p (tree name, edge e)
 {
-  // If no edge is specified, check if NAME is an export on any edge.
-  if (!e)
-    return is_export_p (name);
+  // Check if NAME is an export or can be recomputed.
+  if (e)
+    return is_export_p (name, e->src) || may_recompute_p (name, e);
 
-  return is_export_p (name, e->src);
+  // If no edge is specified, check if NAME can have a range calculated
+  // on any edge.
+  return is_export_p (name) || may_recompute_p (name);
 }
 
 // Dump what is known to GORI computes to listing file F.
@@ -992,6 +994,32 @@ gori_compute::dump (FILE *f)
   gori_map::dump (f);
 }
 
+// Return TRUE if NAME can be recomputed on edge E.  If any direct dependant
+// is exported on edge E, it may change the computed value of NAME.
+
+bool
+gori_compute::may_recompute_p (tree name, edge e)
+{
+  tree dep1 = depend1 (name);
+  tree dep2 = depend2 (name);
+
+  // If the first dependency is not set, there is no recompuation.
+  if (!dep1)
+    return false;
+
+  // Don't recalculate PHIs or statements with side_effects.
+  gimple *s = SSA_NAME_DEF_STMT (name);
+  if (is_a<gphi *> (s) || gimple_has_side_effects (s))
+    return false;
+
+  // If edge is specified, check if NAME can be recalculated on that edge.
+  if (e)
+    return ((is_export_p (dep1, e->src))
+	    || (dep2 && is_export_p (dep2, e->src)));
+
+  return (is_export_p (dep1)) || (dep2 && is_export_p (dep2));
+}
+
 // Calculate a range on edge E and return it in R.  Try to evaluate a
 // range for NAME on this edge.  Return FALSE if this is either not a
 // control edge or NAME is not defined by this edge.
@@ -1026,6 +1054,27 @@ gori_compute::outgoing_edge_range_p (irange &r, edge e, tree name,
 	  return true;
 	}
     }
+  // If NAME isn't exported, check if it can be recomputed.
+  else if (may_recompute_p (name, e))
+    {
+      gimple *def_stmt = SSA_NAME_DEF_STMT (name);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "recomputation attempt on edge %d->%d for ",
+		   e->src->index, e->dest->index);
+	  print_generic_expr (dump_file, name, TDF_SLIM);
+	}
+      // Simply calculate DEF_STMT on edge E usng the range query Q.
+      fold_range (r, def_stmt, e, &q);
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, " : Calculated :");
+	  r.dump (dump_file);
+	  fputc ('\n', dump_file);
+	}
+      return true;
+    }
   return false;
 }
 
diff --git a/gcc/gimple-range-gori.h b/gcc/gimple-range-gori.h
index 06f3b791359..6f187db08cb 100644
--- a/gcc/gimple-range-gori.h
+++ b/gcc/gimple-range-gori.h
@@ -157,6 +157,7 @@ public:
   bool has_edge_range_p (tree name, edge e = NULL);
   void dump (FILE *f);
 private:
+  bool may_recompute_p (tree name, edge e = NULL);
   bool compute_operand_range (irange &r, gimple *stmt, const irange &lhs,
 			      tree name, class fur_source &src);
   bool compute_operand_range_switch (irange &r, gswitch *s, const irange &lhs,