Revert "Drop excess size used for run time allocated stack variables."

This patch caused a bootstrap failure on AIX.

2016-08-24  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	Revert
	2016-08-23  Dominik Vogt  <vogt@linux.vnet.ibm.com>

	* explow.c (get_dynamic_stack_size): Take known alignment of stack
	pointer + STACK_DYNAMIC_OFFSET into account when calculating the
	size needed.

From-SVN: r239735

gcc/ChangeLog

+2016-08-24  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>
+
+	Revert
+	2016-08-23  Dominik Vogt  <vogt@linux.vnet.ibm.com>
+
+	* explow.c (get_dynamic_stack_size): Take known alignment of stack
+	pointer + STACK_DYNAMIC_OFFSET into account when calculating the size
+	needed.
+
 2016-08-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* doc/fragments.texi (MULTILIB_REUSE): Mention that only options in

gcc/explow.c

@@ -1224,15 +1224,9 @@ get_dynamic_stack_size (rtx *psize, unsigned size_align,
      example), so we must preventively align the value.  We leave space
      in SIZE for the hole that might result from the alignment operation.  */
 
-  unsigned known_align = REGNO_POINTER_ALIGN (VIRTUAL_STACK_DYNAMIC_REGNUM);
-  if (known_align == 0)
-    known_align = BITS_PER_UNIT;
-  if (required_align > known_align)
-    {
-      extra = (required_align - known_align) / BITS_PER_UNIT;
-      size = plus_constant (Pmode, size, extra);
-      size = force_operand (size, NULL_RTX);
-    }
+  extra = (required_align - BITS_PER_UNIT) / BITS_PER_UNIT;
+  size = plus_constant (Pmode, size, extra);
+  size = force_operand (size, NULL_RTX);
 
   if (flag_stack_usage_info && pstack_usage_size)
     *pstack_usage_size += extra;