Avoid repeating calculations in threader.

We already attempt to resolve the current path on entry to
find_paths_to_name(), so there's no need to do so again for each
exported range since nothing has changed.

Removing this redundant calculation avoids 22% of calls into the path
solver.

Tested on x86-64 and ppc64le Linux with the usual regstrap.  I also
verified that the before and after number of threads was the same
in a suite of .ii files from a bootstrap.

gcc/ChangeLog:

	PR tree-optimization/102943
	* tree-ssa-threadbackward.c (back_threader::find_paths_to_names):
	Avoid duplicate calculation of paths.

diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 29e9d6a..b7eaff9 100644 (file)
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -443,18 +443,6 @@ back_threader::find_paths_to_names (basic_block bb, bitmap interesting)
              goto leave_bb;
            }
        }
-      // Examine blocks that define or export an interesting SSA,
-      // since they may compute a range which resolve this path.
-      if ((def_bb == bb
-          || bitmap_bit_p (m_ranger->gori ().exports (bb), i))
-         && m_path.length () > 1)
-       {
-         if (maybe_register_path ())
-           {
-             done = true;
-             goto leave_bb;
-           }
-       }
     }
 
   // If there are interesting names not yet processed, keep looking.