[gomp4,11/23] A target hook for struct returns

There's code in function.c to set the return register to the address of
a returned structure even though the return really happens through the
struct pointer passed as an invisible argument. This is unwanted on ptx,
where having a return value does not match the declaration of the
function or the calls to it, causing inconsistencies that the assembler
complains about.

	gcc/
	* target.def (omit_struct_return_reg): New data hook.
	* doc/tm.texi.in: Add @hook TARGET_OMIT_STRUCT_RETURN_REG.
	* doc/tm.texi: Regenerate.
	* function.c (expand_function_end): Use it.

------------------------------------------------------------------------
Index: gcc/doc/tm.texi
===================================================================
--- gcc/doc/tm.texi	(revision 422355)
+++ gcc/doc/tm.texi	(revision 422356)
@@ -4560,6 +4560,14 @@  need more space than is implied by @code
 saving and restoring an arbitrary return value.
 @end defmac
 
+@deftypevr {Target Hook} bool TARGET_OMIT_STRUCT_RETURN_REG
+Normally, when a function returns a structure by memory, the address
+is passed as an invisible pointer argument, but the compiler also
+arranges to return the address from the function like it would a normal
+pointer return value.  Define this to true if that behaviour is
+undesirable on your target.
+@end deftypevr
+
 @deftypefn {Target Hook} bool TARGET_RETURN_IN_MSB (const_tree @var{type})
 This hook should return true if values of type @var{type} are returned
 at the most significant end of a register (in other words, if they are
Index: gcc/doc/tm.texi.in
===================================================================
--- gcc/doc/tm.texi.in	(revision 422355)
+++ gcc/doc/tm.texi.in	(revision 422356)
@@ -3769,6 +3769,8 @@  need more space than is implied by @code
 saving and restoring an arbitrary return value.
 @end defmac
 
+@hook TARGET_OMIT_STRUCT_RETURN_REG
+
 @hook TARGET_RETURN_IN_MSB
 
 @node Aggregate Return
Index: gcc/target.def
===================================================================
--- gcc/target.def	(revision 422355)
+++ gcc/target.def	(revision 422356)
@@ -3601,6 +3601,16 @@  structure value address at the beginning
 to emit adjusting code, you should do it at this point.",
  rtx, (tree fndecl, int incoming),
  hook_rtx_tree_int_null)
+
+DEFHOOKPOD
+(omit_struct_return_reg,
+ "Normally, when a function returns a structure by memory, the address\n\
+is passed as an invisible pointer argument, but the compiler also\n\
+arranges to return the address from the function like it would a normal\n\
+pointer return value.  Define this to true if that behaviour is\n\
+undesirable on your target.",
+ bool, false)
+
 DEFHOOK
 (return_in_memory,
  "This target hook should return a nonzero value to say to return the\n\
Index: gcc/function.c
===================================================================
--- gcc/function.c	(revision 422355)
+++ gcc/function.c	(revision 422356)
@@ -5179,8 +5179,8 @@  expand_function_end (void)
      If returning a structure PCC style,
      the caller also depends on this value.
      And cfun->returns_pcc_struct is not necessarily set.  */
-  if (cfun->returns_struct
-      || cfun->returns_pcc_struct)
+  if ((cfun->returns_struct || cfun->returns_pcc_struct)
+      && !targetm.calls.omit_struct_return_reg)
     {
       rtx value_address = DECL_RTL (DECL_RESULT (current_function_decl));
       tree type = TREE_TYPE (DECL_RESULT (current_function_decl));