if-conv: Fix -fcompare-debug bugs in ifcvt_local_dce [PR94283]

The following testcase shows -fcompare-debug bugs in ifcvt_local_dce,
where the decisions what statements are needed is based also on debug stmt
operands, which is wrong.
So, this patch makes sure to never add debug stmt to the worklist, or never
add an assign to worklist just because it is used in a debug stmt in another
bb.

2020-03-24  Jakub Jelinek  <jakub@redhat.com>

	PR debug/94283
	* tree-if-conv.c (ifcvt_local_dce): For gimple debug stmts, just set
	GF_PLF_2, but don't add them to worklist.  Don't add an assigment to
	worklist or set GF_PLF_2 just because it is used in a debug stmt in
	another bb.  Formatting improvements.

	* gcc.target/i386/pr94283.c: New test.

gcc/ChangeLog

 2020-03-24  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/94283
+	* tree-if-conv.c (ifcvt_local_dce): For gimple debug stmts, just set
+	GF_PLF_2, but don't add them to worklist.  Don't add an assigment to
+	worklist or set GF_PLF_2 just because it is used in a debug stmt in
+	another bb.  Formatting improvements.
+
 	PR debug/94277
 	* cgraphunit.c (check_global_declaration): For DECL_EXTERNAL and
 	non-TREE_PUBLIC non-DECL_ARTIFICIAL FUNCTION_DECLs, set TREE_PUBLIC

gcc/testsuite/ChangeLog

 2020-03-24  Jakub Jelinek  <jakub@redhat.com>
 
+	PR debug/94283
+	* gcc.target/i386/pr94283.c: New test.
+
 	PR debug/94277
 	* gcc.dg/pr94277.c: New test.
 

gcc/testsuite/gcc.target/i386/pr94283.c

+/* PR debug/94283 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fcompare-debug -mavx2" } */
+
+#include "../../gcc.dg/fold-bopcond-1.c"

gcc/tree-if-conv.c

@@ -2917,9 +2917,12 @@ ifcvt_local_dce (class loop *loop)
   for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
     {
       stmt = gsi_stmt (gsi);
-      if (gimple_store_p (stmt)
-	  || gimple_assign_load_p (stmt)
-	  || is_gimple_debug (stmt))
+      if (is_gimple_debug (stmt))
+	{
+	  gimple_set_plf (stmt, GF_PLF_2, true);
+	  continue;
+	}
+      if (gimple_store_p (stmt) || gimple_assign_load_p (stmt))
 	{
 	  gimple_set_plf (stmt, GF_PLF_2, true);
 	  worklist.safe_push (stmt);
@@ -2940,7 +2943,7 @@ ifcvt_local_dce (class loop *loop)
 	  FOR_EACH_IMM_USE_FAST (use_p, imm_iter, lhs)
 	    {
 	      stmt1 = USE_STMT (use_p);
-	      if (gimple_bb (stmt1) != bb)
+	      if (!is_gimple_debug (stmt1) && gimple_bb (stmt1) != bb)
 		{
 		  gimple_set_plf (stmt, GF_PLF_2, true);
 		  worklist.safe_push (stmt);
@@ -2963,8 +2966,7 @@ ifcvt_local_dce (class loop *loop)
 	  if (TREE_CODE (use) != SSA_NAME)
 	    continue;
 	  stmt1 = SSA_NAME_DEF_STMT (use);
-	  if (gimple_bb (stmt1) != bb
-	      || gimple_plf (stmt1, GF_PLF_2))
+	  if (gimple_bb (stmt1) != bb || gimple_plf (stmt1, GF_PLF_2))
 	    continue;
 	  gimple_set_plf (stmt1, GF_PLF_2, true);
 	  worklist.safe_push (stmt1);