[COMMITTED] Move import population from threader to path solver.

diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
index 6da01c7067f..4843c133e62 100644
--- a/gcc/gimple-range-path.cc
+++ b/gcc/gimple-range-path.cc
@@ -439,26 +439,32 @@  path_range_query::add_to_imports (tree name, bitmap imports)
   return false;
 }
 
-// Add the copies of any SSA names in IMPORTS to IMPORTS.
+// Compute the imports to the path ending in EXIT.  These are
+// essentially the SSA names used to calculate the final conditional
+// along the path.
 //
-// These are hints for the solver.  Adding more elements (within
-// reason) doesn't slow us down, because we don't solve anything that
-// doesn't appear in the path.  On the other hand, not having enough
-// imports will limit what we can solve.
+// They are hints for the solver.  Adding more elements doesn't slow
+// us down, because we don't solve anything that doesn't appear in the
+// path.  On the other hand, not having enough imports will limit what
+// we can solve.
 
 void
-path_range_query::add_copies_to_imports ()
+path_range_query::compute_imports (bitmap imports, basic_block exit)
 {
-  auto_vec<tree> worklist (bitmap_count_bits (m_imports));
+  // Start with the imports from the exit block...
+  bitmap r_imports = m_ranger.gori ().imports (exit);
+  bitmap_copy (imports, r_imports);
+
+  auto_vec<tree> worklist (bitmap_count_bits (imports));
   bitmap_iterator bi;
   unsigned i;
-
-  EXECUTE_IF_SET_IN_BITMAP (m_imports, 0, i, bi)
+  EXECUTE_IF_SET_IN_BITMAP (imports, 0, i, bi)
     {
       tree name = ssa_name (i);
       worklist.quick_push (name);
     }
 
+  // ...and add any operands used to define these imports.
   while (!worklist.is_empty ())
     {
       tree name = worklist.pop ();
@@ -466,15 +472,12 @@  path_range_query::add_copies_to_imports ()
 
       if (is_gimple_assign (def_stmt))
 	{
-	  // ?? Adding assignment copies doesn't get us much.  At the
-	  // time of writing, we got 63 more threaded paths across the
-	  // .ii files from a bootstrap.
-	  add_to_imports (gimple_assign_rhs1 (def_stmt), m_imports);
+	  add_to_imports (gimple_assign_rhs1 (def_stmt), imports);
 	  tree rhs = gimple_assign_rhs2 (def_stmt);
-	  if (rhs && add_to_imports (rhs, m_imports))
+	  if (rhs && add_to_imports (rhs, imports))
 	    worklist.safe_push (rhs);
 	  rhs = gimple_assign_rhs3 (def_stmt);
-	  if (rhs && add_to_imports (rhs, m_imports))
+	  if (rhs && add_to_imports (rhs, imports))
 	    worklist.safe_push (rhs);
 	}
       else if (gphi *phi = dyn_cast <gphi *> (def_stmt))
@@ -486,7 +489,7 @@  path_range_query::add_copies_to_imports ()
 
 	      if (TREE_CODE (arg) == SSA_NAME
 		  && m_path.contains (e->src)
-		  && bitmap_set_bit (m_imports, SSA_NAME_VERSION (arg)))
+		  && bitmap_set_bit (imports, SSA_NAME_VERSION (arg)))
 		worklist.safe_push (arg);
 	    }
 	}
@@ -512,16 +515,10 @@  path_range_query::compute_ranges (const vec<basic_block> &path,
   if (imports)
     bitmap_copy (m_imports, imports);
   else
-    {
-      bitmap imports = m_ranger.gori ().imports (exit_bb ());
-      bitmap_copy (m_imports, imports);
-    }
+    compute_imports (m_imports, exit_bb ());
 
   if (m_resolve)
-    {
-      add_copies_to_imports ();
-      get_path_oracle ()->reset_path ();
-    }
+    get_path_oracle ()->reset_path ();
 
   if (DEBUG_SOLVER)
     {
diff --git a/gcc/gimple-range-path.h b/gcc/gimple-range-path.h
index b73549f01a5..b5a054359ad 100644
--- a/gcc/gimple-range-path.h
+++ b/gcc/gimple-range-path.h
@@ -36,6 +36,7 @@  public:
   virtual ~path_range_query ();
   void compute_ranges (const vec<basic_block> &, const bitmap_head *imports = NULL);
   void compute_ranges (edge e);
+  void compute_imports (bitmap imports, basic_block exit);
   bool range_of_expr (irange &r, tree name, gimple * = NULL) override;
   bool range_of_stmt (irange &r, gimple *, tree name = NULL) override;
   bool unreachable_path_p ();
@@ -61,7 +62,6 @@  private:
   void compute_outgoing_relations (basic_block bb, basic_block next);
   void compute_phi_relations (basic_block bb, basic_block prev);
   void maybe_register_phi_relation (gphi *, tree arg);
-  void add_copies_to_imports ();
   bool add_to_imports (tree name, bitmap imports);
   inline bool import_p (tree name);
 
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 0f7b4a732eb..d067c470c38 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -91,7 +91,6 @@  private:
   edge maybe_register_path ();
   void maybe_register_path_dump (edge taken_edge);
   void find_paths_to_names (basic_block bb, bitmap imports);
-  bool resolve_def (tree name, bitmap interesting, vec<tree> &worklist);
   void resolve_phi (gphi *phi, bitmap imports);
   edge find_taken_edge (const vec<basic_block> &path);
   edge find_taken_edge_cond (const vec<basic_block> &path, gcond *);
@@ -363,12 +362,8 @@  back_threader::resolve_phi (gphi *phi, bitmap interesting)
       edge e = gimple_phi_arg_edge (phi, i);
 
       // This is like path_crosses_loops in profitable_path_p but more
-      // restrictive, since profitable_path_p allows threading the
-      // first block because it would be redirected anyhow.
-      //
-      // If we loosened the restriction and used profitable_path_p()
-      // here instead, we would peel off the first iterations of loops
-      // in places like tree-ssa/pr14341.c.
+      // restrictive to avoid peeling off loop iterations (see
+      // tree-ssa/pr14341.c for an example).
       bool profitable_p = m_path[0]->loop_father == e->src->loop_father;
       if (!profitable_p)
 	{
@@ -404,33 +399,6 @@  back_threader::resolve_phi (gphi *phi, bitmap interesting)
     }
 }
 
-// If the definition of NAME causes the final conditional of the
-// current path to be constant, register the path, and return TRUE.
-
-bool
-back_threader::resolve_def (tree name, bitmap interesting, vec<tree> &worklist)
-{
-  gimple *def_stmt = SSA_NAME_DEF_STMT (name);
-
-  // Handle PHIs.
-  if (is_a<gphi *> (def_stmt))
-    {
-      resolve_phi (as_a<gphi *> (def_stmt), interesting);
-      return true;
-    }
-
-  // Defer copies of SSAs by adding the source to the worklist.
-  if (gimple_assign_single_p (def_stmt)
-      && TREE_CODE (gimple_assign_rhs1 (def_stmt)) == SSA_NAME)
-    {
-      tree rhs = gimple_assign_rhs1 (def_stmt);
-      bitmap_set_bit (m_imports, SSA_NAME_VERSION (rhs));
-      bitmap_set_bit (interesting, SSA_NAME_VERSION (rhs));
-      worklist.safe_push (rhs);
-    }
-  return false;
-}
-
 // Find jump threading paths to any of the SSA names in the
 // INTERESTING bitmap, and register any such paths.
 //
@@ -464,13 +432,15 @@  back_threader::find_paths_to_names (basic_block bb, bitmap interesting)
     {
       tree name = worklist.pop ();
       unsigned i = SSA_NAME_VERSION (name);
-      basic_block def_bb = gimple_bb (SSA_NAME_DEF_STMT (name));
+      gimple *def_stmt = SSA_NAME_DEF_STMT (name);
+      basic_block def_bb = gimple_bb (def_stmt);
 
-      // Process any names defined in this block.
+      // Process any PHIs defined in this block.
       if (def_bb == bb
 	  && bitmap_set_bit (processed, i)
-	  && resolve_def (name, interesting, worklist))
+	  && gimple_code (def_stmt) == GIMPLE_PHI)
 	{
+	  resolve_phi (as_a<gphi *> (def_stmt), interesting);
 	  done = true;
 	  break;
 	}
@@ -515,10 +485,9 @@  back_threader::find_paths (basic_block bb, tree name)
       m_visited_bbs.empty ();
       m_path.truncate (0);
       m_name = name;
-      bitmap_clear (m_imports);
+      m_solver->compute_imports (m_imports, bb);
 
       auto_bitmap interesting;
-      bitmap_copy (m_imports, m_ranger->gori ().imports (bb));
       bitmap_copy (interesting, m_imports);
       find_paths_to_names (bb, interesting);
     }