d: Add `@register' attribute to compiler and library.

The `@register` attribute specifies that a local or `__gshared` variable
is to be given a register storage-class in the C sense of the term, and
will be placed into a register named `registerName`.

The variable needs to boiled down to a data type that fits the target
register.  It also cannot have either thread-local or `extern` storage.
It is an error to take the address of a register variable.

	PR d/105413

gcc/d/ChangeLog:

	* d-attribs.cc (d_handle_register_attribute): New function.
	(d_langhook_attribute_table): Add register attribute.
	* d-codegen.cc (d_mark_addressable): Error if taken address of
	register variable.
	(build_frame_type): Error if register variable has non-local
	references.
	* d-tree.h (d_mark_addressable): Add complain parameter.
	* decl.cc (get_symbol_decl): Mark register varibles DECL_REGISTER.
	Error when register variable declared thread-local or extern.
	* expr.cc (ExprVisitor::visit (IndexExp *)): Don't complain about
	marking register vectors as addressable in an ARRAY_REF.

libphobos/ChangeLog:

	* libdruntime/gcc/attributes.d (register): Define.

gcc/testsuite/ChangeLog:

	* gdc.dg/attr_register1.d: New test.
	* gdc.dg/attr_register2.d: New test.
	* gdc.dg/attr_register3.d: New test.

1 files changed, 28 insertions, 0 deletions

diff --git a/libphobos/libdruntime/gcc/attributes.d b/libphobos/libdruntime/gcc/attributes.d
index 710e8ab8a59..40a18bfa947 100644
--- a/libphobos/libdruntime/gcc/attributes.d
+++ b/libphobos/libdruntime/gcc/attributes.d
@@ -302,6 +302,34 @@ auto optimize(A...)(A arguments)
 }
 
 /**
+ * The `@register` attribute specifies that a local or `__gshared` variable
+ * is to be given a register storage-class in the C99 sense of the term, and
+ * will be placed into a register named `registerName`.
+ *
+ * The variable needs to boiled down to a data type that fits the target
+ * register.  It also cannot have either thread-local or `extern` storage.
+ * It is an error to take the address of a register variable.
+ *
+ * Example:
+ * ---
+ * import gcc.attributes;
+ *
+ * @register("ebx") __gshared int ebx = void;
+ *
+ * void func() { @register("r10") long r10 = 0x2a; }
+ * ---
+ */
+auto register(string registerName)
+{
+    return attribute("register", registerName);
+}
+
+auto register(A...)(A arguments)
+{
+    assert(false, "register attribute argument not a string constant");
+}
+
+/**
  * The `@restrict` attribute specifies that a function parameter is to be
  * restrict-qualified in the C99 sense of the term.  The parameter needs to
  * boil down to either a pointer or reference type, such as a D pointer,