[gcc r13-1924] tree-optimization/106495 - avoid threading to possibly never executed edge

[gcc r13-1924] tree-optimization/106495 - avoid threading to possibly never executed edge

[Richard Biener]

https://gcc.gnu.org/g:b9da686470d1c23929eefb401280ad8ba17e2a58

commit r13-1924-gb9da686470d1c23929eefb401280ad8ba17e2a58
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 1 14:59:08 2022 +0200

    tree-optimization/106495 - avoid threading to possibly never executed edge
    
    The following builds upon the logic of the PR105679 fix by avoiding
    to thread to a known edge that is predicted as probably never executed.
    
            PR tree-optimization/106495
            * tree-ssa-threadbackward.cc
            (back_threader_profitability::profitable_path_p): If known_edge
            is probably never executed avoid threading.

Diff:
---
 gcc/tree-ssa-threadbackward.cc | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/gcc/tree-ssa-threadbackward.cc b/gcc/tree-ssa-threadbackward.cc
index 90f5331c265..0519f2a8c4b 100644
--- a/gcc/tree-ssa-threadbackward.cc
+++ b/gcc/tree-ssa-threadbackward.cc
@@ -777,6 +777,13 @@ back_threader_profitability::profitable_path_p (const vec<basic_block> &m_path,
 		     "exceeds PARAM_MAX_FSM_THREAD_PATH_INSNS.\n");
 	  return false;
 	}
+      if (taken_edge && probably_never_executed_edge_p (cfun, taken_edge))
+	{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, "  FAIL: Jump-thread path not considered: "
+		     "path leads to probably never executed edge.\n");
+	  return false;
+	}
       edge entry = find_edge (m_path[m_path.length () - 1],
 			      m_path[m_path.length () - 2]);
       if (probably_never_executed_edge_p (cfun, entry))