Fix -Wimplicit-fallthrough in combine.c

2017-10-18  Martin Liska  <mliska@suse.cz>

	* combine.c (simplify_compare_const): Add gcc_fallthrough.

From-SVN: r253853

gcc/ChangeLog

+2017-10-18  Martin Liska  <mliska@suse.cz>
+
+	* combine.c (simplify_compare_const): Add gcc_fallthrough.
+
 2017-10-18  Robin Dapp  <rdapp@linux.vnet.ibm.com>
 
 	* config/s390/s390.c (s390_bb_fallthru_entry_likely): New function.

gcc/combine.c

@@ -11791,6 +11791,7 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
 	  const_op -= 1;
 	  code = LEU;
 	  /* ... fall through ...  */
+	  gcc_fallthrough ();
 	}
       /* (unsigned) < 0x80000000 is equivalent to >= 0.  */
       else if (is_a <scalar_int_mode> (mode, &int_mode)
@@ -11828,6 +11829,7 @@ simplify_compare_const (enum rtx_code code, machine_mode mode,
 	  const_op -= 1;
 	  code = GTU;
 	  /* ... fall through ...  */
+	  gcc_fallthrough ();
 	}
 
       /* (unsigned) >= 0x80000000 is equivalent to < 0.  */