Merged / updated old alias.c patch; current testcase is

gcc.dg/torture/stackalign/vararg-1.c  -O2
(and higher optimization levels, too).

(orig date 2009-09-23)
2013-07-30  Joern Rennecke <joern.rennecke@embecosm.com>

        * alias.c (base_alias_check): Allow for aliases between stack-
        and frame-pointer referenced memory.

git-svn-id: svn+ssh://thomas.embecosm.com/embecosm/Customer-Projects/adapteva/branches/epiphany-20120120@2349 8ad889b4-764b-0410-b193-d8a7b30fb157

Conflicts:
	gcc/ChangeLog.epiphany
	gcc/alias.c

gcc/ChangeLog.epiphany

@@ -1,3 +1,8 @@
+2013-07-30  Joern Rennecke <joern.rennecke@embecosm.com>
+
+	* alias.c (base_alias_check): Allow for aliases between stack-
+	and frame-pointer referenced memory.
+
 2013-07-29  Joern Rennecke <joern.rennecke@embecosm.com>
 	merged from trunk:
 

gcc/alias.c

@@ -190,6 +190,7 @@ static void memory_modified_1 (rtx, const_rtx, void *);
 	Each of these rtxes has a separate ADDRESS associated with it,
 	each with a negative id.
 
+	Before register elimination / prologue/epilogue generation,
 	GCC is (and is required to be) precise in which register it
 	chooses to access a particular region of stack.  We can therefore
 	assume that accesses based on one of these rtxes do not alias
@@ -1794,6 +1795,17 @@ base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
   if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
     return 0;
 
+  /* If both are stack references, one via the stack pointer, the other via
+     the frame pointer, there can be an alias.
+     E.g.: gcc.c-torture/execute/20041113-1.c -O3 -g,
+           gcc.dg/torture/stackalign/vararg-1.c  -O2  */
+  if (reload_completed
+      && (x_base == static_reg_base_value[STACK_POINTER_REGNUM]
+	  || x_base == static_reg_base_value[HARD_FRAME_POINTER_REGNUM])
+      && (y_base == static_reg_base_value[STACK_POINTER_REGNUM]
+	  || y_base == static_reg_base_value[HARD_FRAME_POINTER_REGNUM]))
+    return 1;
+
   if (unique_base_value_p (x_base) || unique_base_value_p (y_base))
     return 0;