RFA: M32C: Do not enable PCC_BITFIELD_TYPE_MATTERS

[Nick Clifton]

Hi DJ,

  Here is another small m32c patch for your consideration.

  This time the problem is that several gcc tests are reporting a
  warning message along the lines of:

    Offset of packed bit-field [...] has changed in GCC 4.4

  This warning is only significant for targets which use PCC style
  bitfield alignment where the type of the field affects the alignment
  of the field.  Since the M32C only uses 8-bit alignment for all
  types, the type of a bitfield is not actually significant and it is
  safe for PCC_BITFIELD_TYPE_MATTERS to be set to 0.  (It is set to 1
  by default in gcc/config/elfos.h).

  Note - in theory this warning message is expected in the gcc tests
  since they check the pcc_bitfield_type_matters proc.  Eg from
  gcc.dg/bitfld-15.c:

    /* { dg-message "note: Offset of packed bit-field 'b' has changed in GCC 4.4" "" { target pcc_bitfield_type_matters } } */

  In practice however this does not work for the M32C port because the
  pcc_bitfield_type_matters proc does not detect that the M32C port
  (currently) has PCC_BITFIELD_TYPE_MATTERS enabled.  This is because
  the test in the proc:

    struct foo1 { char x; char :0; char y; };
    struct foo2 { char x; int :0; char y; };
    int s[sizeof (struct foo1) != sizeof (struct foo2) ? 1 : -1];

  Assumes that the alignment of the "int" type is greater than the
  alignment of the "char" type.

  So - another way to fix the gcc testsuite failures would be to
  extend the pcc_bitfield_type_matters proc to add a special check for
  the m32c target.  I think that this is a lesser solution because a)
  there is no need for PCC_BITFIELD_TYPE_MATTERS to be defined for the
  M32C and b) if it remains defined then users might run into these
  warning messages themselves.

  OK to apply ?

Cheers
  Nick

gcc/ChangeLog
2009-02-05  Nick Clifton  <nickc@redhat.com>

	* config/m32c/m32c.h (PCC_BITFIELD_TYPE_MATTERS): Define to
	zero.
  
Index: gcc/config/m32c/m32c.h
===================================================================
--- gcc/config/m32c/m32c.h	(revision 143953)
+++ gcc/config/m32c/m32c.h	(working copy)
@@ -154,6 +165,11 @@
 #define FUNCTION_BOUNDARY 8
 #define BIGGEST_ALIGNMENT 8
 
+/* Since we have a maximum structure alignment of 8 there
+   is no need to enforce any alignment of bitfield types.  */
+#undef  PCC_BITFIELD_TYPE_MATTERS
+#define PCC_BITFIELD_TYPE_MATTERS 0
+
 #define STRICT_ALIGNMENT 0
 #define SLOW_BYTE_ACCESS 1