[SFN] start rtl block with label, then markers

Emitting markers before labels turned out to not be worth the trouble.
The markers outside BBs confuse the ebb scheduler, and they don't add
any useful information.  I'll arrange for markers to be moved past
labels, even in gimple, but for now this will fix the two remaining
known problems on ia64.

for  gcc/ChangeLog

	PR bootstrap/83396
	* cfgexpand.c (expand_gimple_basic_block): Expand label first,
	even if there are markers before it.
	* cfgrtl.c (rtl_verify_bb_layout): Reject DEBUG_INSNs outside BBs.

From-SVN: r255833

gcc/ChangeLog

+2017-12-19  Alexandre Oliva <aoliva@redhat.com>
+
+	PR bootstrap/83396
+	* cfgexpand.c (expand_gimple_basic_block): Expand label first,
+	even if there are markers before it.
+	* cfgrtl.c (rtl_verify_bb_layout): Reject DEBUG_INSNs outside BBs.
+
 2017-12-19  Jakub Jelinek  <jakub@redhat.com>
 
 	* read-rtl.c (parse_reg_note_name): Replace Yoda conditions with

gcc/cfgexpand.c

@@ -5515,20 +5515,16 @@ expand_gimple_basic_block (basic_block bb, bool disable_tail_calls)
   gimple *label_stmt = stmt;
   rtx_code_label **elt = lab_rtx_for_bb->get (bb);
 
-  if (stmt)
-    /* We'll get to it in the loop below, and get back to
-       emit_label_and_note then.  */
-    ;
-  else if (stmt || elt)
+  if (stmt || elt)
     {
-    emit_label_and_note:
       gcc_checking_assert (!note);
       last = get_last_insn ();
 
       if (stmt)
 	{
 	  expand_gimple_stmt (stmt);
-	  gsi_next (&gsi);
+	  if (gsi_stmt (gsi) == stmt)
+	    gsi_next (&gsi);
 	}
 
       if (elt)
@@ -5555,7 +5551,7 @@ expand_gimple_basic_block (basic_block bb, bool disable_tail_calls)
       stmt = gsi_stmt (gsi);
 
       if (stmt == label_stmt)
-	goto emit_label_and_note;
+	continue;
 
       /* If this statement is a non-debug one, and we generate debug
 	 insns, then this one might be the last real use of a TERed

gcc/cfgrtl.c

@@ -2954,7 +2954,6 @@ rtl_verify_bb_layout (void)
 	    {
 	    case BARRIER:
 	    case NOTE:
-	    case DEBUG_INSN:
 	      break;
 
 	    case CODE_LABEL: