diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 21966a39d8e5..e444bf1c7c16 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2018-04-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/85414
+	* rtlhooks.c (gen_lowpart_if_possible): Don't call gen_lowpart_SUBREG
+	on a SUBREG.
+
 2018-04-17  Martin Jambor  <mjambor@suse.cz>
 
 	PR ipa/85421
diff --git a/gcc/rtlhooks.c b/gcc/rtlhooks.c
index ecdebbbeb814..59145506a25d 100644
--- a/gcc/rtlhooks.c
+++ b/gcc/rtlhooks.c
@@ -123,9 +123,9 @@ gen_lowpart_if_possible (machine_mode mode, rtx x)
 
       return new_rtx;
     }
-  else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode
+  else if (mode != GET_MODE (x) && GET_MODE (x) != VOIDmode && !SUBREG_P (x)
 	   && validate_subreg (mode, GET_MODE (x), x,
-			        subreg_lowpart_offset (mode, GET_MODE (x))))
+			       subreg_lowpart_offset (mode, GET_MODE (x))))
     return gen_lowpart_SUBREG (mode, x);
   else
     return 0;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9e44409cb7af..95bdc0349b4a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/85414
+	* gcc.dg/pr85414.c: New test.
+
 2018-04-17  Martin Jambor  <mjambor@suse.cz>
 
 	PR ipa/85421
diff --git a/gcc/testsuite/gcc.dg/pr85414.c b/gcc/testsuite/gcc.dg/pr85414.c
new file mode 100644
index 000000000000..d06132492425
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr85414.c
@@ -0,0 +1,10 @@
+/* PR middle-end/85414 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-Og -fgcse -Wno-uninitialized" } */
+
+int
+foo (void)
+{
+  unsigned __int128 c;
+  return __builtin_mul_overflow_p (59, -c, (short) 0);
+}