diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b144a538bef..9ec0a530f3f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,7 +1,12 @@
+2017-05-13  Uros Bizjak  <ubizjak@gmail.com>
+
+	* compare-elim.c (equivalent_reg_at_start): Return NULL_RTX
+	when returned register mode doesn't match original mode.
+
 2017-05-12  Jeff Law  <law@redhat.com>
 	    Jakub Jelinek  <jakub@redhat.com>
 
-	* config/mn10300/mn10300.c (mn10300_match_ccmode): Fix where	
+	* config/mn10300/mn10300.c (mn10300_match_ccmode): Fix where
 	we look for cc setter after the compare-elim changes.
 	* config/mn10300/mn10300.md (addsi3_flags): Fix order of patterns
 	within the vector to match what compare-elim now expects.
diff --git a/gcc/compare-elim.c b/gcc/compare-elim.c
index 69b1de73ba8..b5ce99341f6 100644
--- a/gcc/compare-elim.c
+++ b/gcc/compare-elim.c
@@ -526,6 +526,7 @@ maybe_select_cc_mode (struct comparison *cmp, rtx a ATTRIBUTE_UNUSED,
 static rtx
 equivalent_reg_at_start (rtx reg, rtx_insn *end, rtx_insn *start)
 {
+  machine_mode orig_mode = GET_MODE (reg);
   rtx_insn *bb_head = BB_HEAD (BLOCK_FOR_INSN (end));
 
   for (rtx_insn *insn = PREV_INSN (end);
@@ -572,6 +573,9 @@ equivalent_reg_at_start (rtx reg, rtx_insn *end, rtx_insn *start)
 	return NULL_RTX;
     }
 
+  if (GET_MODE (reg) != orig_mode)
+    return NULL_RTX;
+
   return reg;
 }