Add TYPE_EMPTY_RECORD for C++ empty classhjl/pr60336/x86

Empty record should be returned and passed the same way in C and C++.
This patch overloads a bit, side_effects_flag, in tree_base for C++
empty class.  Middle-end and x86 backend are updated to ignore empty
records for parameter passing and function value return.  Other targets
may need similar changes.

get_ref_base_and_extent is changed to set bitsize to 0 for empty records
so that when ref_maybe_used_by_call_p_1 calls get_ref_base_and_extent to
get 0 as the maximum size on empty record.  Otherwise, find_tail_calls
won't perform tail call optimization for functions with empty record
parameters, as shown in g++.dg/pr60336-1.C and g++.dg/pr60336-2.C.

A new cxx target hook, function_skip_empty_class_p, is added, which
defaults to return false.  This ABI change is enabled only if the ABI
level is at least 10, which is updated in GCC 6, and the target hook
TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P returns true.

gcc/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* calls.c (initialize_argument_information): Warn empty record
	if they are used in a variable argument list or aren't the last
	arguments.  Replace targetm.calls.function_arg,
	targetm.calls.function_incoming_arg and
	targetm.calls.function_arg_advance with function_arg,
	function_incoming_arg and function_arg_advance.
	(expand_call): Replace targetm.calls.function_arg,
	targetm.calls.function_incoming_arg and
	targetm.calls.function_arg_advance with function_arg,
	function_incoming_arg and function_arg_advance.
	(emit_library_call_value_1): Likewise.
	(store_one_arg): Use 0 for empty record size.  Don't
	push 0 size argument onto stack.
	(must_pass_in_stack_var_size_or_pad): Return false for empty
	record.
	* dse.c (get_call_args): Replace targetm.calls.function_arg
	and targetm.calls.function_arg_advance with function_arg and
	function_arg_advance.
	* explow.c (hard_function_value): Use 0 for empty record size.
	* expr.c (block_move_libcall_safe_for_call_parm): Replace
	targetm.calls.function_arg and targetm.calls.function_arg_advance
	with function_arg and function_arg_advance.
	(copy_blkmode_to_reg): Use 0 for empty record size.
	* function.c (aggregate_value_p): Replace
	targetm.calls.return_in_memory with return_in_memory.
	(assign_parm_data_all): Add warn_empty_record.
	(assign_parms_augmented_arg_list): Set warn_empty_record if
	empty records are used in a variable argument list or aren't
	the last arguments.
	(assign_parm_find_entry_rtl): Warn empty record if
	warn_empty_record is set.  Replace
	targetm.calls.function_incoming_arg with function_incoming_arg.
	(assign_parms): Only warn empty record once.  Replace
	targetm.calls.function_arg_advance with function_arg_advance.
	(gimplify_parameters): Replace targetm.calls.function_arg_advance
	with function_arg_advance.
	(locate_and_pad_parm): Use 0 for empty record size.
	(warn_empty_record): New function.
	(function_arg_advance): New wrapper function.
	(function_arg): Likewise.
	(function_incoming_arg): Likewise.
	(return_in_memory): Likewise.
	* lto-streamer-out.c (hash_tree): Call hstate.add_flag with
	TYPE_EMPTY_RECORD for types.
	* print-tree.c (print_node): Also handle TYPE_EMPTY_RECORD.
	* ubsan.c (ubsan_type_descriptor): Likewise.
	* target.def (cxx): Add function_skip_empty_class_p.
	* target.h (function_arg_advance): New prototype.
	(function_arg): Likewise.
	(function_incoming_arg): Likewise.
	(return_in_memory): Likewise.
	* targhooks.c (std_gimplify_va_arg_expr): Use 0 for empty record
	size.
	* tree-dfa.c (get_ref_base_and_extent): Likewise.
	* tree-core.h (tree_base): Mention TYPE_EMPTY_RECORD in comments
	for side_effects_flag.
	* tree-streamer-in.c (unpack_ts_base_value_fields): Stream in
	TYPE_EMPTY_RECORD for types.
	* tree-streamer-out.c (pack_ts_base_value_fields): Stream out
	TYPE_EMPTY_RECORD for types.
	* tree.h (TYPE_EMPTY_RECORD): New.
	(type_is_empty_record_p): New static inline function.
	* var-tracking.c (prepare_call_arguments): Replace
	targetm.calls.function_arg and targetm.calls.function_arg_advance
	with function_arg and function_arg_advance.
	* config/i386/i386.c (ix86_gimplify_va_arg): Use 0 for empty
	record size.
	(TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P): New hook to return true.
	* doc/tm.texi.in (TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P): New
	hook.
	* doc/tm.texi: Regenerated.

gcc/c

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* c-aux-info.c (gen_type): Add TYPE_EMPTY_RECORD check.

gcc/cp/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* class.c (is_empty_collection): New function.
	(is_empty_record): Likewise.
	(finish_struct_1): Set TYPE_EMPTY_RECORD with return value from
	is_empty_record () if the ABI level is at least 10.

gcc/lto/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* lto.c (compare_tree_sccs_1): Call compare_values with
	TYPE_EMPTY_RECORD for types.

gcc/testsuite/

	PR c++/60336
	PR middle-end/67239
	PR target/68355
	* g++.dg/abi/empty12.C: New test.
	* g++.dg/abi/empty12.h: Likewise.
	* g++.dg/abi/empty12a.c: Likewise.
	* g++.dg/abi/empty13.C: Likewise.
	* g++.dg/abi/empty13.h: Likewise.
	* g++.dg/abi/empty13a.c: Likewise.
	* g++.dg/abi/empty14.C: Likewise.
	* g++.dg/abi/empty14.h: Likewise.
	* g++.dg/abi/empty14a.c: Likewise.
	* g++.dg/abi/empty15.C: Likewise.
	* g++.dg/abi/empty15.h: Likewise.
	* g++.dg/abi/empty15a.c: Likewise.
	* g++.dg/abi/empty16.C: Likewise.
	* g++.dg/abi/empty16.h: Likewise.
	* g++.dg/abi/empty16a.c: Likewise.
	* g++.dg/abi/empty17.C: Likewise.
	* g++.dg/abi/empty17.h: Likewise.
	* g++.dg/abi/empty17a.c: Likewise.
	* g++.dg/pr60336-1.C: Likewise.
	* g++.dg/pr60336-2.C: Likewise.
	* g++.dg/pr60336-3.C: Likewise.
	* g++.dg/pr60336-4.C: Likewise.
	* g++.dg/pr60336-5.C: Likewise.
	* g++.dg/pr60336-6.C: Likewise.
	* g++.dg/pr60336-7.C: Likewise.
	* g++.dg/pr60336-8.C: Likewise.
	* g++.dg/pr60336-9.C: Likewise.
	* g++.dg/pr60336-10.C: Likewise.
	* g++.dg/pr60336-11.C: Likewise.
	* g++.dg/pr60336-12.C: Likewise.
	* g++.dg/pr68355.C: Likewise.

23 files changed, 42 insertions, 18 deletions

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 2a9cda619ae..4d4150f7c10 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -54598,6 +54598,9 @@ ix86_addr_space_zero_address_valid (addr_space_t as)
 #undef TARGET_PROMOTE_FUNCTION_MODE
 #define TARGET_PROMOTE_FUNCTION_MODE ix86_promote_function_mode
 
+#undef TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P
+#define TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P hook_bool_void_true
+
 #undef  TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE
 #define TARGET_OVERRIDE_OPTIONS_AFTER_CHANGE ix86_override_options_after_change
 
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index f34b1ef647f..b674208ef8f 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -6885,6 +6885,9 @@ is_empty_type (tree type)
 static bool
 is_really_empty_type (tree type)
 {
+  if (!targetm.cxx.function_skip_empty_class_p ())
+    return false;
+
   if (type == error_mark_node)
     return false;
 
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 8b3bccda967..32639565bc5 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -10238,6 +10238,12 @@ modified value and perform any other actions necessary to support the
 backend's targeted operating system.
 @end deftypefn
 
+@deftypefn {Target Hook} bool TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P (void)
+This hook should return true if no memory slot nor register should be
+used to pass or return an object of empty C++ class.  The default is to
+return @code{false}.
+@end deftypefn
+
 @deftypefn {Target Hook} bool TARGET_CXX_CDTOR_RETURNS_THIS (void)
 This hook should return @code{true} if constructors and destructors return
 the address of the object created/destroyed.  The default is to return
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index f31c763991c..8d82175c7b7 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -7392,6 +7392,8 @@ floating-point support; they are not included in this mechanism.
 
 @hook TARGET_CXX_IMPORT_EXPORT_CLASS
 
+@hook TARGET_CXX_FUNCTION_SKIP_EMPTY_CLASS_P
+
 @hook TARGET_CXX_CDTOR_RETURNS_THIS
 
 @hook TARGET_CXX_KEY_METHOD_MAY_BE_INLINE
diff --git a/gcc/target.def b/gcc/target.def
index 5c8e4e16cc1..9e21696f791 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -5393,6 +5393,16 @@ modified value and perform any other actions necessary to support the\n\
 backend's targeted operating system.",
  int, (tree type, int import_export), NULL)
 
+/* Returns true if no memory slot nor register should be used to pass
+   or return an object of empty C++ class.  */
+DEFHOOK
+(function_skip_empty_class_p,
+ "This hook should return true if no memory slot nor register should be\n\
+used to pass or return an object of empty C++ class.  The default is to\n\
+return @code{false}.",
+ bool, (void),
+ hook_bool_void_false)
+
 /* Returns true if constructors and destructors return "this".  */
 DEFHOOK
 (cdtor_returns_this,
diff --git a/gcc/testsuite/g++.dg/abi/empty12.C b/gcc/testsuite/g++.dg/abi/empty12.C
index db2fd24f6db..c2e4dc7461c 100644
--- a/gcc/testsuite/g++.dg/abi/empty12.C
+++ b/gcc/testsuite/g++.dg/abi/empty12.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c" }
 // { dg-additional-sources "empty12a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/abi/empty13.C b/gcc/testsuite/g++.dg/abi/empty13.C
index d1e094685de..d2e297edbb2 100644
--- a/gcc/testsuite/g++.dg/abi/empty13.C
+++ b/gcc/testsuite/g++.dg/abi/empty13.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c -fabi-version=9" }
 // { dg-additional-sources "empty13a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/abi/empty14.C b/gcc/testsuite/g++.dg/abi/empty14.C
index d32eed77d66..48ee1f845e6 100644
--- a/gcc/testsuite/g++.dg/abi/empty14.C
+++ b/gcc/testsuite/g++.dg/abi/empty14.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c" }
 // { dg-additional-sources "empty14a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/abi/empty15.C b/gcc/testsuite/g++.dg/abi/empty15.C
index 507a0cd2345..7bb6055ef7c 100644
--- a/gcc/testsuite/g++.dg/abi/empty15.C
+++ b/gcc/testsuite/g++.dg/abi/empty15.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c" }
 // { dg-additional-sources "empty15a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/abi/empty16.C b/gcc/testsuite/g++.dg/abi/empty16.C
index 42705137475..a4e7870e14b 100644
--- a/gcc/testsuite/g++.dg/abi/empty16.C
+++ b/gcc/testsuite/g++.dg/abi/empty16.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c" }
 // { dg-additional-sources "empty16a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/abi/empty17.C b/gcc/testsuite/g++.dg/abi/empty17.C
index 472708365ac..bfcd7c915cd 100644
--- a/gcc/testsuite/g++.dg/abi/empty17.C
+++ b/gcc/testsuite/g++.dg/abi/empty17.C
@@ -1,5 +1,5 @@
 // PR c++/60336
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-x c" }
 // { dg-additional-sources "empty17a.c" }
 // { dg-prune-output "command line option" }
diff --git a/gcc/testsuite/g++.dg/pr60336-1.C b/gcc/testsuite/g++.dg/pr60336-1.C
index af0863887a0..946f8accda2 100644
--- a/gcc/testsuite/g++.dg/pr60336-1.C
+++ b/gcc/testsuite/g++.dg/pr60336-1.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }
 
diff --git a/gcc/testsuite/g++.dg/pr60336-10.C b/gcc/testsuite/g++.dg/pr60336-10.C
index 6c9c990dad6..57707fca749 100644
--- a/gcc/testsuite/g++.dg/pr60336-10.C
+++ b/gcc/testsuite/g++.dg/pr60336-10.C
@@ -1,4 +1,4 @@
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 #include <stdarg.h>
diff --git a/gcc/testsuite/g++.dg/pr60336-11.C b/gcc/testsuite/g++.dg/pr60336-11.C
index c92f3d43a5b..32000b2ebe5 100644
--- a/gcc/testsuite/g++.dg/pr60336-11.C
+++ b/gcc/testsuite/g++.dg/pr60336-11.C
@@ -1,4 +1,4 @@
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 #include <stdarg.h>
diff --git a/gcc/testsuite/g++.dg/pr60336-12.C b/gcc/testsuite/g++.dg/pr60336-12.C
index 83a7bb0cfa0..febcc6fcf2e 100644
--- a/gcc/testsuite/g++.dg/pr60336-12.C
+++ b/gcc/testsuite/g++.dg/pr60336-12.C
@@ -1,4 +1,4 @@
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 #include <stdarg.h>
diff --git a/gcc/testsuite/g++.dg/pr60336-2.C b/gcc/testsuite/g++.dg/pr60336-2.C
index 386c82a68c4..8ec5bae7d77 100644
--- a/gcc/testsuite/g++.dg/pr60336-2.C
+++ b/gcc/testsuite/g++.dg/pr60336-2.C
@@ -1,4 +1,4 @@
-// { dg-do run }
+// { dg-do run { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 #include <stdarg.h>
diff --git a/gcc/testsuite/g++.dg/pr60336-3.C b/gcc/testsuite/g++.dg/pr60336-3.C
index 3afdc8d81ca..d39d84c96d7 100644
--- a/gcc/testsuite/g++.dg/pr60336-3.C
+++ b/gcc/testsuite/g++.dg/pr60336-3.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 struct dummy { struct{}__attribute__((aligned (4))) a[7]; };
diff --git a/gcc/testsuite/g++.dg/pr60336-5.C b/gcc/testsuite/g++.dg/pr60336-5.C
index b0c76ad5aa2..a051f6e6105 100644
--- a/gcc/testsuite/g++.dg/pr60336-5.C
+++ b/gcc/testsuite/g++.dg/pr60336-5.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }
 
diff --git a/gcc/testsuite/g++.dg/pr60336-6.C b/gcc/testsuite/g++.dg/pr60336-6.C
index 58796519334..22728d364fd 100644
--- a/gcc/testsuite/g++.dg/pr60336-6.C
+++ b/gcc/testsuite/g++.dg/pr60336-6.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }
 
diff --git a/gcc/testsuite/g++.dg/pr60336-7.C b/gcc/testsuite/g++.dg/pr60336-7.C
index 0e5d2ef2f11..5fc8320c7de 100644
--- a/gcc/testsuite/g++.dg/pr60336-7.C
+++ b/gcc/testsuite/g++.dg/pr60336-7.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }
 
diff --git a/gcc/testsuite/g++.dg/pr60336-8.C b/gcc/testsuite/g++.dg/pr60336-8.C
index e4487cf8f25..7b02039ef48 100644
--- a/gcc/testsuite/g++.dg/pr60336-8.C
+++ b/gcc/testsuite/g++.dg/pr60336-8.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2" }
 
 struct dummy { struct{} a[7][3]; };
diff --git a/gcc/testsuite/g++.dg/pr60336-9.C b/gcc/testsuite/g++.dg/pr60336-9.C
index 4ad333f6b9c..3d768c06f14 100644
--- a/gcc/testsuite/g++.dg/pr60336-9.C
+++ b/gcc/testsuite/g++.dg/pr60336-9.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }
 
diff --git a/gcc/testsuite/g++.dg/pr68355.C b/gcc/testsuite/g++.dg/pr68355.C
index 1354fc497b5..5c2f0da3fd3 100644
--- a/gcc/testsuite/g++.dg/pr68355.C
+++ b/gcc/testsuite/g++.dg/pr68355.C
@@ -1,4 +1,4 @@
-// { dg-do compile }
+// { dg-do compile { target i?86-*-* x86_64-*-* } }
 // { dg-options "-O2 -std=c++11 -fno-pic" }
 // { dg-require-effective-target fpic }