[Patch libobjc] Fix Darwin powerpc m64 breakage.

[IainS]

it's nice when 4 lines of code fixes 4 dozen test-suite fails ..
.. and disappointing that it's probably taken more than 4 years for  
someone to have time to look ..

Andrew, I realize that this doesn't in any way alter the 'broken-ness'  
of the current design - but, on the other hand, it does make powerpc- 
apple-darwin9 work @m64 within that current design.  [... and gets rid  
of a bunch of test-suite fail output for those of us who test powerpc  
@m64].

FWIW, actually fixing m32 might be somewhat more taxing since that  
involves replication of the xxx_special_round_type_align () functions  
(which have drifted away from the implementation in encode.c.).

I had a quick scan but didn't see any specific PR to put this against...

OK for trunk?
Iain

libobjc/Changelog:

	* encoding.c: Add TARGET_ALIGN_NATURAL definition for m64 powerpc  
darwin.
	Add a comment as to why, update FIXME comments.

testsuite/ChangeLog:
	
	* objc.dg/gnu-encoding/struct-layout-encoding-1_generate.c: Update  
XFAILs.


Index: libobjc/encoding.c
===================================================================
--- libobjc/encoding.c	(revision 161768)
+++ libobjc/encoding.c	(working copy)
@@ -105,10 +105,22 @@ static int __attribute__ ((__unused__)) not_target
  #undef ALTIVEC_VECTOR_MODE
  #define ALTIVEC_VECTOR_MODE(MODE) (0)

+/* Furthermore, some (powerpc) targets also use TARGET_ALIGN_NATURAL
+   in their alignment macros.  Currently[4.5/6], rs6000.h points this
+   to a static variable, initialized by target overrides.  This is  
reset
+   in linux64.h but not in darwin64.h and therefore, all the darwin64
+   stuff is broken.  This echoes the comments above and below about
+   the badness of the approach.  Other powerpc64 targets might also
+   be affected.  */
+
+#if defined(DEFAULT_ABI) && (DEFAULT_ABI==ABI_DARWIN) && __LP64__
+#  undef TARGET_ALIGN_NATURAL
+#  define TARGET_ALIGN_NATURAL 1
+#endif

  /*  FIXME: while this file has no business including tm.h, this
      definitely has no business defining this macro but it
-    is only way around without really rewritting this file,
+    is only way around without really rewriting this file,
      should look after the branch of 3.4 to fix this.  */
  #define rs6000_special_round_type_align(STRUCT, COMPUTED, SPECIFIED)	\
    ({ const char *_fields = TYPE_FIELDS (STRUCT);				\
@@ -116,8 +128,12 @@ static int __attribute__ ((__unused__)) not_target
      && TYPE_MODE (strip_array_types (TREE_TYPE (_fields))) ==  
DFmode)	\
     ? MAX (MAX (COMPUTED, SPECIFIED), 64)				\
     : MAX (COMPUTED, SPECIFIED));})
+
  /* FIXME: The word 'fixme' is insufficient to explain the wrong-ness
-   of this next macro definition.  */
+   of this next macro definition.
+   FIXME1: It's also out of date, darwin no longer has the same  
alignment
+   'special' as aix - this is probably the origin of the m32  
breakage, since
+   the 'special' routine is not used at m64 with  
TARGET_ALIGN_NATURAL=1.  */
  #define darwin_rs6000_special_round_type_align(S,C,S2) \
    rs6000_special_round_type_align(S,C,S2)

Index: gcc/testsuite/objc.dg/gnu-encoding/struct-layout- 
encoding-1_generate.c
===================================================================
--- gcc/testsuite/objc.dg/gnu-encoding/struct-layout- 
encoding-1_generate.c	(revision 161768)
+++ gcc/testsuite/objc.dg/gnu-encoding/struct-layout- 
encoding-1_generate.c	(working copy)
@@ -236,7 +236,7 @@ switchfiles (int fields)
        || filecnt == 22)
       {
        fprintf (outfile, "\
-/* { dg-do run { xfail powerpc*-*-darwin* powerpc*-*-aix* } } */\n\
+/* { dg-do run { xfail { { \"powerpc*-*-darwin*\" && { ! lp64 } } ||  
{ \"powerpc*-*-aix*\" } } } } */\n\
  /* { dg-options \"-w -I%s -fgnu-runtime\" } */\n", srcdir);
       }
    /* FIXME: these should not be xfailed but they are because