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));
