rs6000: Small varargs for BE SVR4 (PR61729, PR77850)

The varargs code for SVR4 puts all (integer) arguments in 4-byte slots.
When it then reads an item from there as something not a multiple of 4
bytes, it needs to adjust the address if big endian.  We didn't yet do
that.

This fixes the g++.dg/abi/scoped1.C, gcc.dg/compat/scalar-by-value-4,
and gcc.dg/compat/scalar-return-4 testcases.


	PR target/61729
	PR target/77850
	* config/rs6000/rs6000.c (rs6000_gimplify_va_arg): Adjust address to
	read from, for big endian.

From-SVN: r244740

gcc/ChangeLog

+2017-01-20  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/61729
+	PR target/77850
+	* config/rs6000/rs6000.c (rs6000_gimplify_va_arg): Adjust address to
+	read from, for big endian.
+
 2017-01-20  Jiong Wang  <jiong.wang@arm.com>
 
 	* config/aarch64/aarch64-builtins.c (aarch64_init_builtins): Register

gcc/config/rs6000/rs6000.c

@@ -13684,6 +13684,7 @@ rs6000_gimplify_va_arg (tree valist, tree type, gimple_seq *pre_p,
 
   size = int_size_in_bytes (type);
   rsize = (size + 3) / 4;
+  int pad = 4 * rsize - size;
   align = 1;
 
   machine_mode mode = TYPE_MODE (type);
@@ -13765,6 +13766,10 @@ rs6000_gimplify_va_arg (tree valist, tree type, gimple_seq *pre_p,
 	  && mode == SDmode)
 	t = fold_build_pointer_plus_hwi (t, size);
 
+      /* Args are passed right-aligned.  */
+      if (BYTES_BIG_ENDIAN)
+	t = fold_build_pointer_plus_hwi (t, pad);
+
       gimplify_assign (addr, t, pre_p);
 
       gimple_seq_add_stmt (pre_p, gimple_build_goto (lab_over));
@@ -13790,6 +13795,11 @@ rs6000_gimplify_va_arg (tree valist, tree type, gimple_seq *pre_p,
       t = build2 (BIT_AND_EXPR, TREE_TYPE (t), t,
 		  build_int_cst (TREE_TYPE (t), -align));
     }
+
+  /* Args are passed right-aligned.  */
+  if (BYTES_BIG_ENDIAN)
+    t = fold_build_pointer_plus_hwi (t, pad);
+
   gimplify_expr (&t, pre_p, NULL, is_gimple_val, fb_rvalue);
 
   gimplify_assign (unshare_expr (addr), t, pre_p);