Re: [RFA][PATCH] Refactor duplicated code used by various dom walkers

[Jeff Law <law at redhat dot com>]

On 11/03/2017 09:01 AM, Jeff Law wrote:
> On 11/03/2017 04:05 AM, Richard Biener wrote:
> > On Fri, Nov 3, 2017 at 4:49 AM, Jeff Law <law@redhat.com> wrote:
> > > Several passes which perform dominator walks want to identify when 
> > > block has
> > > a single incoming edge, ignoring loop backedges.
> > >
> > > I'm aware of 4 implementations of this code.  3 of the 4 are 
> > > identical in
> > > function.  The 4th (tree-ssa-dom.c) has an additional twist that it also
> > > ignores edges that are not marked as executable.
> > >
> > > So I've taken the more general implementation from tree-ssa-dom.c and
> > > conditionalized the handling of unexecutable edges on a flag and 
> > > moved the
> > > implementation into cfganal.c where it more naturally belongs.
> > >
> > > Bootstrapped and regression tested on x86_64.  OK for the trunk?
> >
> > Minor nits (sorry...)
> No need to apologize.  I'm always appreciative of feedback as it 
> consistently improves what ultimately lands in the tree.
>
>
> > > Jeff
> > >
> > >          * cfganal.c (single_incoming_edge_ignoring_loop_edges): New 
> > > function
> > >          extracted from tree-ssa-dom.c.
> > >          * cfganal.h (single_incoming_edge_ignoring_loop_edges): 
> > > Prototype.
> > >          * tree-ssa-dom.c (single_incoming_edge_ignoring_loop_edges): 
> > > Remove.
> > >          (record_equivalences_from_incoming_edge): Add additional 
> > > argument
> > >          to single_incoming_edge_ignoring_loop_edges call.
> > >          * tree-ssa-uncprop.c 
> > > (single_incoming_edge_ignoring_loop_edges):
> > > Remove.
> > >          (uncprop_dom_walker::before_dom_children): Add additional 
> > > argument
> > >          to single_incoming_edge_ignoring_loop_edges call.
> > >          * tree-ssa-sccvn.c (sccvn_dom_walker::before_dom_children): Use
> > >          single_incoming_edge_ignoring_loop_edges rather than open 
> > > coding.
> > >          * tree-vrp.c (evrp_dom_walker::before_dom_children): Similarly.
> > >
> > >
> > >
> > >
> > >
> > > diff --git a/gcc/cfganal.c b/gcc/cfganal.c
> > > index c506067..14d94b2 100644
> > > --- a/gcc/cfganal.c
> > > +++ b/gcc/cfganal.c
> > > @@ -1554,3 +1554,38 @@ single_pred_before_succ_order (void)
> > >   #undef MARK_VISITED
> > >   #undef VISITED_P
> > >   }
> > > +
> > > +/* Ignoring loop backedges, if BB has precisely one incoming edge then
> > > +   return that edge.  Otherwise return NULL.  */
> > > +edge
> > > +single_incoming_edge_ignoring_loop_edges (basic_block bb,
> > > +                                         bool ignore_unreachable)
> >
> > single_pred_edge_ignoring_loop_edges and ignore_not_executable
> >
> > to better match existing CFG functions and actual edge flag use.
> >
> > Ok with that change.
> Sure.  Easy to change.
Final patch attached for archival purposes.  I took the liberty of also 
documenting the new IGNORE_NOT_EXECUTABLE argument.

Jeff

commit 1477a5a7a0a0a93cb8b1c79581134b8ccdca072b
Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Fri Nov 3 16:28:28 2017 +0000

            * cfganal.c (single_pred_edge_ignoring_loop_edges): New function
            extracted from tree-ssa-dom.c.
            * cfganal.h (single_pred_edge_ignoring_loop_edges): Prototype.
            * tree-ssa-dom.c (single_incoming_edge_ignoring_loop_edges): Remove.
            (record_equivalences_from_incoming_edge): Add additional argument
            to single_pred_edge_ignoring_loop_edges call.
            * tree-ssa-uncprop.c (single_incoming_edge_ignoring_loop_edges): Remove.
            (uncprop_dom_walker::before_dom_children): Add additional argument
            to single_pred_edge_ignoring_loop_edges call.
            * tree-ssa-sccvn.c (sccvn_dom_walker::before_dom_children): Use
            single_pred_edge_ignoring_loop_edges rather than open coding.
            * tree-vrp.c (evrp_dom_walker::before_dom_children): Similarly.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@254383 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 83dbaaaa8bf..2fc7db44f7b 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,18 @@
+2017-11-03  Jeff Law  <law@redhat.com>
+
+	* cfganal.c (single_pred_edge_ignoring_loop_edges): New function
+	extracted from tree-ssa-dom.c.
+	* cfganal.h (single_pred_edge_ignoring_loop_edges): Prototype.
+	* tree-ssa-dom.c (single_incoming_edge_ignoring_loop_edges): Remove.
+	(record_equivalences_from_incoming_edge): Add additional argument
+	to single_pred_edge_ignoring_loop_edges call.
+	* tree-ssa-uncprop.c (single_incoming_edge_ignoring_loop_edges): Remove.
+	(uncprop_dom_walker::before_dom_children): Add additional argument
+	to single_pred_edge_ignoring_loop_edges call.
+	* tree-ssa-sccvn.c (sccvn_dom_walker::before_dom_children): Use
+	single_pred_edge_ignoring_loop_edges rather than open coding.
+	* tree-vrp.c (evrp_dom_walker::before_dom_children): Similarly.
+
 2017-11-03  Marc Glisse  <marc.glisse@inria.fr>
 
 	* match.pd (-(-A)): Rewrite.
diff --git a/gcc/cfganal.c b/gcc/cfganal.c
index c506067fdcd..8bf8a53fa58 100644
--- a/gcc/cfganal.c
+++ b/gcc/cfganal.c
@@ -1554,3 +1554,42 @@ single_pred_before_succ_order (void)
 #undef MARK_VISITED
 #undef VISITED_P
 }
+
+/* Ignoring loop backedges, if BB has precisely one incoming edge then
+   return that edge.  Otherwise return NULL.
+
+   When IGNORE_NOT_EXECUTABLE is true, also ignore edges that are not marked
+   as executable.  */
+
+edge
+single_pred_edge_ignoring_loop_edges (basic_block bb,
+				      bool ignore_not_executable)
+{
+  edge retval = NULL;
+  edge e;
+  edge_iterator ei;
+
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    {
+      /* A loop back edge can be identified by the destination of
+	 the edge dominating the source of the edge.  */
+      if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
+	continue;
+
+      /* We can safely ignore edges that are not executable.  */
+      if (ignore_not_executable
+	  && (e->flags & EDGE_EXECUTABLE) == 0)
+	continue;
+
+      /* If we have already seen a non-loop edge, then we must have
+	 multiple incoming non-loop edges and thus we return NULL.  */
+      if (retval)
+	return NULL;
+
+      /* This is the first non-loop incoming edge we have found.  Record
+	 it.  */
+      retval = e;
+    }
+
+  return retval;
+}
diff --git a/gcc/cfganal.h b/gcc/cfganal.h
index 39bb5e547a5..c5cb51d9cf8 100644
--- a/gcc/cfganal.h
+++ b/gcc/cfganal.h
@@ -77,5 +77,8 @@ extern void bitmap_intersection_of_preds (sbitmap, sbitmap *, basic_block);
 extern void bitmap_union_of_succs (sbitmap, sbitmap *, basic_block);
 extern void bitmap_union_of_preds (sbitmap, sbitmap *, basic_block);
 extern basic_block * single_pred_before_succ_order (void);
+extern edge single_incoming_edge_ignoring_loop_edges (basic_block, bool);
+extern edge single_pred_edge_ignoring_loop_edges (basic_block, bool);
+
 
 #endif /* GCC_CFGANAL_H */
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 06be69a530c..eb85b4a09ad 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -113,7 +113,6 @@ static void eliminate_redundant_computations (gimple_stmt_iterator *,
 					      class avail_exprs_stack *);
 static void record_equivalences_from_stmt (gimple *, int,
 					   class avail_exprs_stack *);
-static edge single_incoming_edge_ignoring_loop_edges (basic_block);
 static void dump_dominator_optimization_stats (FILE *file,
 					       hash_table<expr_elt_hasher> *);
 
@@ -1057,39 +1056,6 @@ record_equivalences_from_phis (basic_block bb)
     }
 }
 
-/* Ignoring loop backedges, if BB has precisely one incoming edge then
-   return that edge.  Otherwise return NULL.  */
-static edge
-single_incoming_edge_ignoring_loop_edges (basic_block bb)
-{
-  edge retval = NULL;
-  edge e;
-  edge_iterator ei;
-
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    {
-      /* A loop back edge can be identified by the destination of
-	 the edge dominating the source of the edge.  */
-      if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
-	continue;
-
-      /* We can safely ignore edges that are not executable.  */
-      if ((e->flags & EDGE_EXECUTABLE) == 0)
-	continue;
-
-      /* If we have already seen a non-loop edge, then we must have
-	 multiple incoming non-loop edges and thus we return NULL.  */
-      if (retval)
-	return NULL;
-
-      /* This is the first non-loop incoming edge we have found.  Record
-	 it.  */
-      retval = e;
-    }
-
-  return retval;
-}
-
 /* Record any equivalences created by the incoming edge to BB into
    CONST_AND_COPIES and AVAIL_EXPRS_STACK.  If BB has more than one
    incoming edge, then no equivalence is created.  */
@@ -1107,7 +1073,7 @@ record_equivalences_from_incoming_edge (basic_block bb,
      the parent was followed.  */
   parent = get_immediate_dominator (CDI_DOMINATORS, bb);
 
-  e = single_incoming_edge_ignoring_loop_edges (bb);
+  e = single_pred_edge_ignoring_loop_edges (bb, true);
 
   /* If we had a single incoming edge from our parent block, then enter
      any data associated with the edge into our tables.  */
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 306080b6a41..f5bc28efa70 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -4847,34 +4847,18 @@ sccvn_dom_walker::after_dom_children (basic_block bb)
 edge
 sccvn_dom_walker::before_dom_children (basic_block bb)
 {
-  edge e;
-  edge_iterator ei;
-
   if (dump_file && (dump_flags & TDF_DETAILS))
     fprintf (dump_file, "Visiting BB %d\n", bb->index);
 
   /* If we have a single predecessor record the equivalence from a
      possible condition on the predecessor edge.  */
-  edge pred_e = NULL;
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    {
-      /* Ignore simple backedges from this to allow recording conditions
-         in loop headers.  */
-      if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
-	continue;
-      if (! pred_e)
-	pred_e = e;
-      else
-	{
-	  pred_e = NULL;
-	  break;
-	}
-    }
+  edge pred_e = single_pred_edge_ignoring_loop_edges (bb, false);
   if (pred_e)
     {
       /* Check if there are multiple executable successor edges in
 	 the source block.  Otherwise there is no additional info
 	 to be recorded.  */
+      edge_iterator ei;
       edge e2;
       FOR_EACH_EDGE (e2, ei, pred_e->src->succs)
 	if (e2 != pred_e
diff --git a/gcc/tree-ssa-uncprop.c b/gcc/tree-ssa-uncprop.c
index 200ec70c9b7..35a49d28420 100644
--- a/gcc/tree-ssa-uncprop.c
+++ b/gcc/tree-ssa-uncprop.c
@@ -408,40 +408,10 @@ uncprop_into_successor_phis (basic_block bb)
     }
 }
 
-/* Ignoring loop backedges, if BB has precisely one incoming edge then
-   return that edge.  Otherwise return NULL.  */
-static edge
-single_incoming_edge_ignoring_loop_edges (basic_block bb)
-{
-  edge retval = NULL;
-  edge e;
-  edge_iterator ei;
-
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    {
-      /* A loop back edge can be identified by the destination of
-	 the edge dominating the source of the edge.  */
-      if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
-	continue;
-
-      /* If we have already seen a non-loop edge, then we must have
-	 multiple incoming non-loop edges and thus we return NULL.  */
-      if (retval)
-	return NULL;
-
-      /* This is the first non-loop incoming edge we have found.  Record
-	 it.  */
-      retval = e;
-    }
-
-  return retval;
-}
-
 edge
 uncprop_dom_walker::before_dom_children (basic_block bb)
 {
   basic_block parent;
-  edge e;
   bool recorded = false;
 
   /* If this block is dominated by a single incoming edge and that edge
@@ -450,7 +420,7 @@ uncprop_dom_walker::before_dom_children (basic_block bb)
   parent = get_immediate_dominator (CDI_DOMINATORS, bb);
   if (parent)
     {
-      e = single_incoming_edge_ignoring_loop_edges (bb);
+      edge e = single_pred_edge_ignoring_loop_edges (bb, false);
 
       if (e && e->src == parent && e->aux)
 	{
diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index 63ee1568990..541c5c4eaf9 100644
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -10970,33 +10970,17 @@ evrp_dom_walker::try_find_new_range (tree name,
 edge
 evrp_dom_walker::before_dom_children (basic_block bb)
 {
-  tree op0 = NULL_TREE;
-  edge_iterator ei;
-  edge e;
-
   if (dump_file && (dump_flags & TDF_DETAILS))
     fprintf (dump_file, "Visiting BB%d\n", bb->index);
 
   stack.safe_push (std::make_pair (NULL_TREE, (value_range *)NULL));
 
-  edge pred_e = NULL;
-  FOR_EACH_EDGE (e, ei, bb->preds)
-    {
-      /* Ignore simple backedges from this to allow recording conditions
-	 in loop headers.  */
-      if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
-	continue;
-      if (! pred_e)
-	pred_e = e;
-      else
-	{
-	  pred_e = NULL;
-	  break;
-	}
-    }
+  edge pred_e = single_pred_edge_ignoring_loop_edges (bb, false);
   if (pred_e)
     {
       gimple *stmt = last_stmt (pred_e->src);
+      tree op0 = NULL_TREE;
+
       if (stmt
 	  && gimple_code (stmt) == GIMPLE_COND
 	  && (op0 = gimple_cond_lhs (stmt))
@@ -11040,6 +11024,8 @@ evrp_dom_walker::before_dom_children (basic_block bb)
 
   /* Visit PHI stmts and discover any new VRs possible.  */
   bool has_unvisited_preds = false;
+  edge_iterator ei;
+  edge e;
   FOR_EACH_EDGE (e, ei, bb->preds)
     if (e->flags & EDGE_EXECUTABLE
 	&& !(e->src->flags & BB_VISITED))