i386: Set cfun->machine->max_used_stack_alignment if needed

cfun->machine->max_used_stack_alignment is used to decide how stack frame
should be aligned.  This is independent of any psABIs nor 32-bit vs 64-bit.
It is always safe to compute max_used_stack_alignment.  We compute it only
if 128-bit aligned load/store may be generated on misaligned stack slot
which will lead to segfault.

gcc/

	PR target/86386
	* config/i386/i386.c (ix86_finalize_stack_frame_flags): Set
	cfun->machine->max_used_stack_alignment if needed.

gcc/testsuite/

	PR target/86386
	* gcc.target/i386/pr86386.c: New file.

From-SVN: r263317

gcc/ChangeLog

+2018-08-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/86386
+	* config/i386/i386.c (ix86_finalize_stack_frame_flags): Set
+	cfun->machine->max_used_stack_alignment if needed.
+
 2018-08-04  Martin Sebor  <msebor@redhat.com>
 
 	PR tree-optimization/86571

gcc/config/i386/i386.c

@@ -13281,12 +13281,14 @@ ix86_finalize_stack_frame_flags (void)
 	  recompute_frame_layout_p = true;
 	}
     }
-  else if (crtl->max_used_stack_slot_alignment
-	   > crtl->preferred_stack_boundary)
-    {
-      /* We don't need to realign stack.  But we still need to keep
-	 stack frame properly aligned to satisfy the largest alignment
-	 of stack slots.  */
+  else if (crtl->max_used_stack_slot_alignment >= 128)
+    {
+      /* We don't need to realign stack.  max_used_stack_alignment is
+	 used to decide how stack frame should be aligned.  This is
+	 independent of any psABIs nor 32-bit vs 64-bit.  It is always
+	 safe to compute max_used_stack_alignment.  We compute it only
+	 if 128-bit aligned load/store may be generated on misaligned
+	 stack slot which will lead to segfault.   */
       if (ix86_find_max_used_stack_alignment (stack_alignment, true))
 	cfun->machine->max_used_stack_alignment
 	  = stack_alignment / BITS_PER_UNIT;

gcc/testsuite/ChangeLog

+2018-08-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/86386
+	* gcc.target/i386/pr86386.c: New file.
+
 2018-08-04  Tom de Vries  <tdevries@suse.de>
 
 	* lib/gcc-gdb-test.exp: Use absolute line number in pass/fail line.

gcc/testsuite/gcc.target/i386/pr86386.c

+/* PR target/86386 */
+/* { dg-do run { target { avx_runtime && int128 } } } */
+/* { dg-options "-Os -fno-tree-dce -mstringop-strategy=vector_loop -mavx" } */
+
+unsigned c, d, e, f;
+
+unsigned __attribute__((noipa))
+foo (unsigned char g, unsigned short h, unsigned i, unsigned long long j,
+     unsigned char k, unsigned short l, unsigned m, unsigned __int128 n)
+{
+  __builtin_memset (&e, 0, 3);
+  n <<= m;
+  __builtin_memcpy (&m, 2 + (char *) &n, 1);
+  m >>= 0;
+  d ^= __builtin_mul_overflow (l, n, &m);
+  return m;
+}
+
+int
+main ()
+{
+  unsigned __int128 x = foo (0, 0, 0, 0, 0, 4, 1, 3);
+  if (x != 24)
+    __builtin_abort ();
+  return 0;
+}