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// The "shape" of a type is best defined as "how a value of a type looks from
// the standpoint of a certain built-in operation".
//
// This is used to collapse glues that would otherwise be separate. For
// instance, a boxed tuple of 3 ints and a boxed tuple of 3 uints look the
// same as far as reference count manipulation is concerned, so they get the
// same shape so that their reference count glues can be collapsed together.
// To give another example, an int and float have the same (nonexistent!) glue
// as far as reference counting is concerned, since they aren't reference
// counted.
import front::ast;
import middle::trans::variant_info;
import middle::ty;
type variant_getter = fn(&ast::def_id) -> vec[variant_info];
// Reference counting shapes.
mod rc {
// TODO: Re-export, so that users can just say shape::rc.
// FIXME: The bottom two should be just "vec[rc]", but that causes an
// infinite loop in trans.
tag rc {
rs_none; // No reference count.
rs_ref; // Reference counted box.
rs_tag(vec[@rc]); // Discriminated union.
rs_tup(vec[@rc]); // Tuple.
}
fn shape_of(&ty::ctxt tcx, variant_getter getter, ty::t t) -> rc {
alt (ty::struct(tcx, t)) {
// TODO: Or-patterns
case (ty::ty_nil) { ret rs_none; }
case (ty::ty_bool) { ret rs_none; }
case (ty::ty_int) { ret rs_none; }
case (ty::ty_uint) { ret rs_none; }
case (ty::ty_machine(_)) { ret rs_none; }
case (ty::ty_char) { ret rs_none; }
case (ty::ty_str) { ret rs_none; }
case (ty::ty_tag(?did, ?params)) {
let vec[@rc] result = vec();
auto vinfos = getter(did);
for (variant_info vinfo in vinfos) {
let vec[@rc] variant_rcs = vec();
for (ty::t typ in vinfo.args) {
auto ty_1 = ty::bind_params_in_type(tcx, typ);
ty_1 = ty::substitute_type_params(tcx, params, ty_1);
variant_rcs += vec(@shape_of(tcx, getter, ty_1));
}
result += vec(@rs_tup(variant_rcs));
}
ret rs_tag(result);
}
case (ty::ty_box(_)) { ret rs_ref; }
case (ty::ty_vec(_)) { ret rs_ref; }
case (ty::ty_port(_)) { ret rs_ref; }
case (ty::ty_chan(_)) { ret rs_ref; }
case (ty::ty_task) { ret rs_ref; }
case (ty::ty_tup(?mts)) {
let vec[@rc] result = vec();
for (ty::mt tm in mts) {
result += vec(@shape_of(tcx, getter, tm.ty));
}
ret rs_tup(result);
}
case (ty::ty_rec(?fields)) {
let vec[@rc] result = vec();
for (ty::field fld in fields) {
result += vec(@shape_of(tcx, getter, fld.mt.ty));
}
ret rs_tup(result);
}
case (ty::ty_fn(_, _, _)) { ret rs_ref; }
case (ty::ty_native_fn(_, _, _)) { ret rs_ref; }
case (ty::ty_obj(_)) { ret rs_ref; }
case (ty::ty_var(_)) { log_err "var in rc::shape_of()"; fail; }
case (ty::ty_local(_)) {
log_err "local in rc::shape_of()";
fail;
}
case (ty::ty_param(_)) {
log_err "param in rc::shape_of()";
fail;
}
case (ty::ty_bound_param(_)) {
log_err "bound param in rc::shape_of()";
fail;
}
case (ty::ty_type) { ret rs_ref; }
case (ty::ty_native) { ret rs_none; }
}
}
}
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