Add hint if the fallthrough target of current BB isn't the one

placed closely next.

2019-07-12  Kewen Lin  <linkw@gcc.gnu.org>

    * gcc/cfgrtl.c (print_rtl_with_bb): Emit a hint if the
    fallthrough target of current basic block isn't the placed
    right next.

From-SVN: r273430

gcc/ChangeLog

+2019-07-12  Kewen Lin  <linkw@gcc.gnu.org>
+
+	* gcc/cfgrtl.c (print_rtl_with_bb): Emit a hint if the
+	fallthrough target of current basic block isn't the placed
+	right next.
+
 2019-07-11  Sunil K Pandey  <sunil.k.pandey@intel.com>
 
 	PR target/90980

gcc/cfgrtl.c

@@ -2198,7 +2198,7 @@ print_rtl_with_bb (FILE *outf, const rtx_insn *rtx_first, dump_flags_t flags)
       if (df)
 	df_dump_start (outf);
 
-      if (flags & TDF_BLOCKS)
+      if (cfun->curr_properties & PROP_cfg)
 	{
 	  FOR_EACH_BB_REVERSE_FN (bb, cfun)
 	    {
@@ -2206,6 +2206,8 @@ print_rtl_with_bb (FILE *outf, const rtx_insn *rtx_first, dump_flags_t flags)
 
 	      start[INSN_UID (BB_HEAD (bb))] = bb;
 	      end[INSN_UID (BB_END (bb))] = bb;
+	      if (flags & TDF_BLOCKS)
+		{
 		  for (x = BB_HEAD (bb); x != NULL_RTX; x = NEXT_INSN (x))
 		    {
 		      enum bb_state state = IN_MULTIPLE_BB;
@@ -2219,6 +2221,7 @@ print_rtl_with_bb (FILE *outf, const rtx_insn *rtx_first, dump_flags_t flags)
 		    }
 		}
 	    }
+	}
 
       for (tmp_rtx = rtx_first; tmp_rtx != NULL; tmp_rtx = NEXT_INSN (tmp_rtx))
 	{
@@ -2249,16 +2252,36 @@ print_rtl_with_bb (FILE *outf, const rtx_insn *rtx_first, dump_flags_t flags)
 	  if (flags & TDF_DETAILS)
 	    df_dump_insn_bottom (tmp_rtx, outf);
 
-	  if (flags & TDF_BLOCKS)
-	    {
 	  bb = end[INSN_UID (tmp_rtx)];
 	  if (bb != NULL)
 	    {
+	      if (flags & TDF_BLOCKS)
+		{
 		  dump_bb_info (outf, bb, 0, dump_flags, false, true);
 		  if (df && (flags & TDF_DETAILS))
 		    df_dump_bottom (bb, outf);
 		  putc ('\n', outf);
 		}
+	      /* Emit a hint if the fallthrough target of current basic block
+	         isn't the one placed right next.  */
+	      else if (EDGE_COUNT (bb->succs) > 0)
+		{
+		  gcc_assert (BB_END (bb) == tmp_rtx);
+		  const rtx_insn *ninsn = NEXT_INSN (tmp_rtx);
+		  /* Bypass intervening deleted-insn notes and debug insns.  */
+		  while (ninsn
+			 && !NONDEBUG_INSN_P (ninsn)
+			 && !start[INSN_UID (ninsn)])
+		    ninsn = NEXT_INSN (ninsn);
+		  edge e = find_fallthru_edge (bb->succs);
+		  if (e && ninsn)
+		    {
+		      basic_block dest = e->dest;
+		      if (start[INSN_UID (ninsn)] != dest)
+			fprintf (outf, "%s      ; pc falls through to BB %d\n",
+				 print_rtx_head, dest->index);
+		    }
+		}
 	    }
 	}