[-fcompare-debug] find jump before debug insns in expand

A debug insn after the final jump of a basic block may cause the
expander to emit a dummy move where the non-debug compile won't
because it finds the jump insn at the end of the insn stream.

Fix the condition so that, instead of requiring the jump as the last
insn, it also matches a jump followed by debug insns.

This fixes the compilation of libgcc/libgcov-profiler.c with
-fcompare-debug on i686-linux-gnu.

for  gcc/ChangeLog

	* cfgexpand.c (expand_gimple_basic_block): Disregard debug
	insns after final jump in test to emit dummy move.

From-SVN: r244089

gcc/ChangeLog

 2017-01-04  Alexandre Oliva <aoliva@redhat.com>
 
+	* cfgexpand.c (expand_gimple_basic_block): Disregard debug
+	insns after final jump in test to emit dummy move.
+
+2017-01-04  Alexandre Oliva <aoliva@redhat.com>
+
 	* gimple-iterator.h (gsi_one_nondebug_before_end_p): New.
 	* tree-eh.c (cleanup_empty_eh): Skip more debug stmts.
 

gcc/cfgexpand.c

@@ -5767,7 +5767,9 @@ expand_gimple_basic_block (basic_block bb, bool disable_tail_calls)
   if (single_succ_p (bb)
       && (single_succ_edge (bb)->flags & EDGE_FALLTHRU)
       && (last = get_last_insn ())
-      && JUMP_P (last))
+      && (JUMP_P (last)
+	  || (DEBUG_INSN_P (last)
+	      && JUMP_P (prev_nondebug_insn (last)))))
     {
       rtx dummy = gen_reg_rtx (SImode);
       emit_insn_after_noloc (gen_move_insn (dummy, dummy), last, NULL);