ifcvt: Don't make invalid insns for a cond trap (PR78751)

As shown in the PR, ifcvt will happily make invalid insns when given the
chance.  This patch teaches it some manners.


	PR rtl-optimization/78751
	* ifcvt.c (find_cond_trap): If we generated a non-existing insn,
	give up.

From-SVN: r244476

gcc/ChangeLog

+2017-01-15  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/78751
+	* ifcvt.c (find_cond_trap): If we generated a non-existing insn,
+	give up.
+
 2017-01-14  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/79090

gcc/ifcvt.c

@@ -4686,6 +4686,11 @@ find_cond_trap (basic_block test_bb, edge then_edge, edge else_edge)
   if (seq == NULL)
     return FALSE;
 
+  /* If that results in an invalid insn, back out.  */
+  for (rtx_insn *x = seq; x; x = NEXT_INSN (x))
+    if (recog_memoized (x) < 0)
+      return FALSE;
+
   /* Emit the new insns before cond_earliest.  */
   emit_insn_before_setloc (seq, cond_earliest, INSN_LOCATION (trap));