From patchwork Sat Jul 24 08:36:14 2010
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [Darwin,2/2] fix PPC64 ABI
Date: Fri, 23 Jul 2010 22:36:14 -0000
From: IainS <developer@sandoe-acoustics.co.uk>
X-Patchwork-Id: 59852
Message-Id: <9C2B0543-065F-4BFB-B3E1-C2E138A54927@sandoe-acoustics.co.uk>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: mrs@gcc.gnu.org, David Edelsohn <dje.gcc@gmail.com>

Hi,

We need to deal with the fact that the darwin ppc64 ABI is defined by an
earlier version of gcc, with the property that it always applied  
alignment
adjustments to the va-args (even for zero-sized types).  The cheapest  
way
to deal with this is to replicate the effect of the part of  
std_gimplify_va_arg_expr ()
that carries out the align adjust, for the case  of relevance.

I've made it such that there is no impact at all for non-darwin.
The impact for darwin is restricted to the single m64 ABI case.

OK for trunk and 4.5 when it re-opens?
Iain

gcc/

	PR target/29090
	* config/rs6000/rs6000.c (rs6000_gimplify_va_arg): Special-case the
	Darwin64 ABI, for zero-sized objects.


+      valist_tmp = fold_convert (build_pointer_type (type),  
valist_tmp);
+      return build_va_arg_indirect_ref (valist_tmp);
+    }
+#endif
+
    if (DEFAULT_ABI != ABI_V4)
      {
        if (targetm.calls.split_complex_arg && TREE_CODE (type) ==  
COMPLEX_TYPE)


Index: gcc/config/rs6000/rs6000.c
===================================================================
--- gcc/config/rs6000/rs6000.c	(revision 162457)
+++ gcc/config/rs6000/rs6000.c	(working copy)
@@ -8931,6 +8995,51 @@ rs6000_gimplify_va_arg (tree valist, tree type,  
gi
        return build_va_arg_indirect_ref (t);
      }

+#if TARGET_MACHO
+  /* We need to deal with the fact that the darwin ppc64 ABI is  
defined by an
+     earlier version of gcc, with the property that it always applied  
alignment
+     adjustments to the va-args (even for zero-sized types).  The  
cheapest way
+     to deal with this is to replicate the effect of the part of
+     std_gimplify_va_arg_expr that carries out the align adjust, for  
the case
+     of relevance.
+     We don't need to check for pass-by-reference because of the test  
above.
+     We can return a simplifed answer, since we know there's no  
offset to add.  */
+
+  if (rs6000_darwin64_abi
+      && integer_zerop (TYPE_SIZE (type)))
+    {
+      unsigned HOST_WIDE_INT align, boundary;
+      tree valist_tmp = get_initialized_tmp_var (valist, pre_p, NULL);
+      align = PARM_BOUNDARY / BITS_PER_UNIT;
+      boundary = FUNCTION_ARG_BOUNDARY (TYPE_MODE (type), type);
+      if (boundary > MAX_SUPPORTED_STACK_ALIGNMENT)
+	boundary = MAX_SUPPORTED_STACK_ALIGNMENT;
+      boundary /= BITS_PER_UNIT;
+      if (boundary > align)
+	{
+	  tree t ;
+	  /* This updates arg ptr by the amount that would be necessary
+	     to align the zero-sized (but not zero-alignment) item.  */
+	  t = build2 (MODIFY_EXPR, TREE_TYPE (valist), valist_tmp,
+		  fold_build2 (POINTER_PLUS_EXPR,
+			       TREE_TYPE (valist),
+			       valist_tmp, size_int (boundary - 1)));
+	  gimplify_and_add (t, pre_p);
+
+	  t = fold_convert (sizetype, valist_tmp);
+	  t = build2 (MODIFY_EXPR, TREE_TYPE (valist), valist_tmp,
+		  fold_convert (TREE_TYPE (valist),
+				fold_build2 (BIT_AND_EXPR, sizetype, t,
+					     size_int (-boundary))));
+	  t = build2 (MODIFY_EXPR, TREE_TYPE (valist), valist, t);
+	  gimplify_and_add (t, pre_p);
+	}
+      /* Since it is zero-sized there's no increment for the item  
itself. */