[gcc(refs/users/pheeck/heads/sccp)] fixed crashing on 20090917-1.c

[gcc(refs/users/pheeck/heads/sccp)] fixed crashing on 20090917-1.c

[Filip Kastl]

https://gcc.gnu.org/g:4894c7738e555630329e04100af6ffcb7265bb85

commit 4894c7738e555630329e04100af6ffcb7265bb85
Author: Filip Kastl <filip.kastl@gmail.com>
Date:   Tue Nov 29 12:49:22 2022 +0100

    fixed crashing on 20090917-1.c

Diff:
---
 gcc/sccp.cc | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/gcc/sccp.cc b/gcc/sccp.cc
index c8c24fca2cf..5079b6e10df 100644
--- a/gcc/sccp.cc
+++ b/gcc/sccp.cc
@@ -309,10 +309,12 @@ static void
 replace_scc_by_value (vec<gimple *> scc, tree replace_by)
 {
   // DEBUG
+  /*
   if (scc.length () >= 5)
     {
       std::cerr << "Replacing SCC of length " << scc.length () << std::endl;
     }
+  */
 
   for (gimple *stmt : scc)
     {
@@ -335,6 +337,30 @@ replace_scc_by_value (vec<gimple *> scc, tree replace_by)
     }
 }
 
+/* Remove all PHIs with zero uses.  */
+
+static void
+remove_zero_uses_phis ()
+{
+  basic_block bb;
+  FOR_EACH_BB_FN (bb, cfun)
+    {
+      gphi_iterator pi;
+      for (pi = gsi_start_phis (bb); !gsi_end_p (pi);)
+	{
+	  gphi *phi = pi.phi ();
+	  tree ssa_name = gimple_phi_result (phi);
+	  if (has_zero_uses (ssa_name))
+	    {
+	      /* Note that remove_phi_node() also frees SSA name.  */
+	      remove_phi_node (&pi, true);
+	    }
+	  else
+	    gsi_next (&pi);
+	}
+    }
+}
+
 /* Apply Braun et al.'s algorithm on a given set of statements. Treat copy
    statements as PHI functions with a single argument.
    Main function of this pass.  */
@@ -427,6 +453,8 @@ sccp_propagate (auto_vec<gimple *> &copy_stmts)
 
       scc.release ();
     }
+
+  remove_zero_uses_phis ();
 }
 
 /* Return all statements in cfun that may be useful.  */
@@ -515,8 +543,39 @@ unsigned
 pass_sccp::execute (function *)
 {
   init_sccp ();
+
+  // DEBUG
+  /*
+  std::cerr << "Before:" << std::endl;
+  basic_block bb;
+  FOR_EACH_BB_FN (bb, cfun)
+    {
+      gphi_iterator pi;
+      for (pi = gsi_start_phis (bb); !gsi_end_p (pi); gsi_next (&pi))
+	{
+	  gphi *phi = pi.phi ();
+	  debug_gimple_stmt (phi);
+	}
+    }
+  */
+
   auto_vec<gimple *> stmts = get_all_may_generate_useful_copy ();
   sccp_propagate (stmts);
+
+  // DEBUG
+  /*
+  std::cerr << "After:" << std::endl;
+  FOR_EACH_BB_FN (bb, cfun)
+    {
+      gphi_iterator pi;
+      for (pi = gsi_start_phis (bb); !gsi_end_p (pi); gsi_next (&pi))
+	{
+	  gphi *phi = pi.phi ();
+	  debug_gimple_stmt (phi);
+	}
+    }
+  */
+
   finalize_sccp ();
 
   return 0;