[PATCH] i386: Always set cfun->machine->max_used_stack_alignment

[H.J. Lu]

We should always set cfun->machine->max_used_stack_alignment if the
maximum stack slot alignment may be greater than 64 bits.

Tested on i686 and x86-64.  OK for master and backport for GCC 8?

Thanks.

H.J.
----
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.
---
 gcc/config/i386/i386.c                  |  6 +++---
 gcc/testsuite/gcc.target/i386/pr86386.c | 26 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr86386.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index ee409cfe7e4..4a0a050b3a2 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -13281,12 +13281,12 @@ ix86_finalize_stack_frame_flags (void)
          recompute_frame_layout_p = true;
        }
     }
-  else if (crtl->max_used_stack_slot_alignment
-          > crtl->preferred_stack_boundary)
+  else if (crtl->max_used_stack_slot_alignment > 64)
     {
       /* 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.  */
+        of stack slots if the maximum stack slot alignment may be
+        greater than 64 bits.  */
       if (ix86_find_max_used_stack_alignment (stack_alignment, true))
        cfun->machine->max_used_stack_alignment
          = stack_alignment / BITS_PER_UNIT;
diff --git a/gcc/testsuite/gcc.target/i386/pr86386.c 
b/gcc/testsuite/gcc.target/i386/pr86386.c
new file mode 100644
index 00000000000..a67cf45444e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr86386.c
@@ -0,0 +1,26 @@
+/* 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;
+}
-- 
2.17.1