re PR middle-end/85414 (ICE: in ix86_expand_prologue, at config/i386/i386.c:13810 with -Og -fgcse)

	PR middle-end/85414
	* rtlhooks.c (gen_lowpart_if_possible): Don't call gen_lowpart_SUBREG
	on a SUBREG.

	* gcc.dg/pr85414.c: New test.

From-SVN: r259433

gcc/ChangeLog

+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

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;

gcc/testsuite/ChangeLog

+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

gcc/testsuite/gcc.dg/pr85414.c

+/* 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);
+}