[PATCH] s390: Implement 'type_align' gdbarch method

[Andreas Arnez <arnez@linux.ibm.com>]

The align.exp test case yields many FAILs on s390x, since GDB's _Alignoff
doesn't always agree with the compiler's.  On s390x, the maximum alignment
is 8, but GDB returns an alignment of 16 for 16-byte data types such as
"long double".

This is fixed by implementing the type_align gdbarch method.  The new
method returns an alignment of 8 for all integer, floating-point, and
vector types larger than 8 bytes.  With this change, all align.exp tests
pass.

gdb/ChangeLog:

	* s390-tdep.c (s390_type_align): New function.
	(s390_gdbarch_init): Set it as type_align gdbarch method.
---
 gdb/s390-tdep.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/gdb/s390-tdep.c b/gdb/s390-tdep.c
index 4b931017a8..871efc59bc 100644
--- a/gdb/s390-tdep.c
+++ b/gdb/s390-tdep.c
@@ -52,6 +52,37 @@ constexpr gdb_byte s390_break_insn[] = { 0x0, 0x1 };
 
 typedef BP_MANIPULATION (s390_break_insn) s390_breakpoint;
 
+/* Types.  */
+
+/* Implement the gdbarch type alignment method.  */
+
+static ULONGEST
+s390_type_align (gdbarch *gdbarch, struct type *t)
+{
+  t = check_typedef (t);
+
+  if (TYPE_LENGTH (t) > 8)
+    {
+      switch (TYPE_CODE (t))
+	{
+	case TYPE_CODE_INT:
+	case TYPE_CODE_RANGE:
+	case TYPE_CODE_FLT:
+	case TYPE_CODE_ENUM:
+	case TYPE_CODE_CHAR:
+	case TYPE_CODE_BOOL:
+	case TYPE_CODE_DECFLOAT:
+	  return 8;
+
+	case TYPE_CODE_ARRAY:
+	  if (TYPE_VECTOR (t))
+	    return 8;
+	  break;
+	}
+    }
+  return 0;
+}
+
 /* Decoding S/390 instructions.  */
 
 /* Read a single instruction from address AT.  */
@@ -6944,6 +6975,8 @@ s390_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_long_double_bit (gdbarch, 128);
   set_gdbarch_long_double_format (gdbarch, floatformats_ia64_quad);
 
+  set_gdbarch_type_align (gdbarch, s390_type_align);
+
   /* Breakpoints.  */
   /* Amount PC must be decremented by after a breakpoint.  This is
      often the number of bytes returned by gdbarch_breakpoint_from_pc but not
-- 
2.17.0