d: Add `@visibility' and `@hidden' attributes.

The `@visibility' attribute is functionality the same as
`__attribute__((visibility))', and `@hidden' is a convenience alias to
`@visibility("hidden")' defined in the `gcc.attributes' module.

As the visibility of a symbol is also indirectly controlled by the
`export' keyword, the handling of this in the code generation pass has
been improved so that conflicts will be appropriately diagnosed.

gcc/d/ChangeLog:

	* d-attribs.cc (d_langhook_attribute_table): Add visibility.
	(insert_type_attribute): Use decl_attributes instead of
	merge_attributes.
	(insert_decl_attribute): Likewise.
	(apply_user_attributes): Do nothing when no UDAs applied.
	(d_handle_visibility_attribute): New function.
	* d-gimplify.cc (d_gimplify_binary_expr): Adjust.
	* d-tree.h (set_visibility_for_decl): Declare.
	* decl.cc (get_symbol_decl): Move setting of visibility flags to...
	(set_visibility_for_decl): ... here.  New function.
	* types.cc (TypeVisitor::visit (TypeStruct *)): Call
	set_visibility_for_decl().
	(TypeVisitor::visit (TypeClass *)): Likewise.

gcc/testsuite/ChangeLog:

	* gdc.dg/attr_visibility1.d: New test.
	* gdc.dg/attr_visibility2.d: New test.
	* gdc.dg/attr_visibility3.d: New test.

libphobos/ChangeLog:

	* libdruntime/gcc/attributes.d (visibility): Define.
	(hidden): Define.

3 files changed, 80 insertions, 0 deletions

diff --git a/gcc/testsuite/gdc.dg/attr_visibility1.d b/gcc/testsuite/gdc.dg/attr_visibility1.d
new file mode 100644
index 0000000..a7ed406
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/attr_visibility1.d
@@ -0,0 +1,25 @@
+// { dg-do compile }
+// { dg-require-visibility "" }
+
+import gcc.attributes;
+
+void nested()
+{
+    @attribute("visibility", "default")
+    struct nested_struct { } // { dg-warning ".visibility. attribute ignored" }
+
+    @attribute("visibility", "default")
+    void nested_func() { } // { dg-warning ".visibility. attribute ignored" }
+}
+
+@attribute("visibility", 123)
+int not_a_string(); // { dg-error "visibility argument not a string" }
+
+@attribute("visibility", "invalid argument")
+int invalid_argument(); // { dg-error ".visibility. argument must be one of" }
+
+@attribute("visibility", "default")
+int redeclared_visibility();
+
+@attribute("visibility", "internal")
+int redeclared_visibility(); // { dg-error "redeclared with different visibility" }
diff --git a/gcc/testsuite/gdc.dg/attr_visibility2.d b/gcc/testsuite/gdc.dg/attr_visibility2.d
new file mode 100644
index 0000000..a339882
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/attr_visibility2.d
@@ -0,0 +1,26 @@
+// { dg-do compile }
+// { dg-require-visibility "" }
+
+module attr_visibility2;
+
+import gcc.attributes;
+
+// { dg-final { scan-hidden "_D16attr_visibility25func1FZv" } }
+
+@hidden void func1() { }
+
+// { dg-final { scan-hidden "_D16attr_visibility25func2FZv" } }
+
+@hidden void func2();
+
+void func2() { }
+
+// { dg-final { scan-hidden "_D16attr_visibility25func3FZv" } }
+
+void func3();
+
+@hidden void func3() { }
+
+// { dg-final { scan-hidden "_D16attr_visibility210globalvar1i" } }
+
+@hidden __gshared int globalvar1 = 5;
diff --git a/gcc/testsuite/gdc.dg/attr_visibility3.d b/gcc/testsuite/gdc.dg/attr_visibility3.d
new file mode 100644
index 0000000..3298428
--- /dev/null
+++ b/gcc/testsuite/gdc.dg/attr_visibility3.d
@@ -0,0 +1,29 @@
+// { dg-do compile }
+// { dg-require-visibility "" }
+// { dg-require-dll "" }
+
+import gcc.attributes;
+
+@visibility("hidden")
+export void func1(); // { dg-error ".func1. was declared .export." }
+
+@visibility("hidden")
+export void func2() { } // { dg-error ".func2. was declared .export." }
+
+@visibility("default")
+export void func3();
+
+@visibility("default")
+export void func4() { };
+
+@visibility("hidden")
+export struct type1 { } // { dg-error ".type1. was declared .export." }
+
+@visibility("default")
+export struct type2 { }
+
+@visibility("hidden")
+export class type3 { } // { dg-error ".type3. was declared .export." }
+
+@visibility("default")
+export class type4 { }