i386: Add a test for PR target/78585

PR target/78585 has been fixed for GCC 7 by

commit 7ed04d053eead43d87dff40fb4e2904219afc4d5
Author: jakub <jakub@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Wed Nov 30 13:02:07 2016 +0000

	* config/i386/i386.c (dimode_scalar_chain::convert_op): Avoid
	sharing the SUBREG rtx between move and following insn.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@243018 138bc75d-0d04-0410-961f-82ee72b054a4

	PR target/78585:
	* gcc.target/i386/pr78585.c: New test.

From-SVN: r256402

gcc/testsuite/ChangeLog

+2018-01-09  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/78585:
+	* gcc.target/i386/pr78585.c: New test.
+
 2018-01-09  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/83734

gcc/testsuite/gcc.target/i386/pr78585.c

+/* { dg-do run } */
+/* { dg-require-effective-target avx } */
+/* { dg-options "-Os -fno-ipa-cp -fschedule-insns -mavx" } */
+
+#include "avx-check.h"
+
+typedef unsigned int u32;
+typedef unsigned long long u64;
+
+u32 x0, x1, x2, x3, x4;
+u64 x5, x6;
+
+static u64 __attribute__ ((noinline, noclone))
+foo (u64 x7)
+{
+  x6 = x2;
+  x6 *= 5;
+  x6--;
+  return x0 + x5 + x1 + x7 + 1 + x3 + x4;
+}
+
+static void
+__attribute__ ((noinline))
+avx_test ()
+{
+  u64 x = foo (0);
+  __builtin_printf ("%016llx", (unsigned long long) (x >> 0));
+  __builtin_printf ("\n");
+}