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Allow a target to skip an unnecssary register return value for a struct return.

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* 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.

From-SVN: r217123
This commit is contained in:
Bernd Schmidt 2014-11-05 12:14:36 +00:00 committed by Bernd Schmidt
parent a50fa76a9d
commit e0d14c396a
5 changed files with 27 additions and 2 deletions
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5
gcc/ChangeLog
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@ -1,5 +1,10 @@
2014-11-05 Bernd Schmidt <bernds@codesourcery.com>
* 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.
* target.def (no_register_allocation): New data hook.
* doc/tm.texi.in: Add @hook TARGET_NO_REGISTER_ALLOCATION.
* doc/tm.texi: Regenerate.

8
gcc/doc/tm.texi
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@ -4371,6 +4371,14 @@ need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
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

2
gcc/doc/tm.texi.in
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@ -3567,6 +3567,8 @@ need more space than is implied by @code{FUNCTION_VALUE_REGNO_P} for
saving and restoring an arbitrary return value.
@end defmac
@hook TARGET_OMIT_STRUCT_RETURN_REG
@hook TARGET_RETURN_IN_MSB
@node Aggregate Return

4
gcc/function.c
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@ -5177,8 +5177,8 @@ 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));

10
gcc/target.def
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@ -3731,6 +3731,16 @@ structure value address at the beginning of a function. If you need\n\
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\