cfgrtl: Don't crash in rtl_dump_bb if BB_END(bb) is NULL

Currently rtl_dump_bb crashes if BB_END(bb) is NULL, like it can be
during expand (rtl_dump_bb can be called at any time, by the emergency
dump added recently for example).

This fixes it.


	* cfgrtl.c (rtl_dump_bb): Don't call NEXT_INSN on NULL.

From-SVN: r250480

gcc/ChangeLog

+2017-07-24  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* cfgrtl.c (rtl_dump_bb): Don't call NEXT_INSN on NULL.
+
 2017-07-24  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	PR target/79041

gcc/cfgrtl.c

@@ -2109,8 +2109,6 @@ commit_edge_insertions (void)
 static void
 rtl_dump_bb (FILE *outf, basic_block bb, int indent, dump_flags_t flags)
 {
-  rtx_insn *insn;
-  rtx_insn *last;
   char *s_indent;
 
   s_indent = (char *) alloca ((size_t) indent + 1);
@@ -2124,18 +2122,22 @@ rtl_dump_bb (FILE *outf, basic_block bb, int indent, dump_flags_t flags)
     }
 
   if (bb->index != ENTRY_BLOCK && bb->index != EXIT_BLOCK)
-    for (insn = BB_HEAD (bb), last = NEXT_INSN (BB_END (bb)); insn != last;
-	 insn = NEXT_INSN (insn))
-      {
-	if (flags & TDF_DETAILS)
-	  df_dump_insn_top (insn, outf);
-	if (! (flags & TDF_SLIM))
-	  print_rtl_single (outf, insn);
-	else
-	  dump_insn_slim (outf, insn);
-	if (flags & TDF_DETAILS)
-	  df_dump_insn_bottom (insn, outf);
-      }
+    {
+      rtx_insn *last = BB_END (bb);
+      if (last)
+	last = NEXT_INSN (last);
+      for (rtx_insn *insn = BB_HEAD (bb); insn != last; insn = NEXT_INSN (insn))
+	{
+	  if (flags & TDF_DETAILS)
+	    df_dump_insn_top (insn, outf);
+	  if (! (flags & TDF_SLIM))
+	    print_rtl_single (outf, insn);
+	  else
+	    dump_insn_slim (outf, insn);
+	  if (flags & TDF_DETAILS)
+	    df_dump_insn_bottom (insn, outf);
+	}
+    }
 
   if (df && (flags & TDF_DETAILS))
     {