rustc: Beginnings of a "shape" module to convert types to shapes

1 files changed, 98 insertions, 0 deletions

diff --git a/src/comp/middle/shape.rs b/src/comp/middle/shape.rs
new file mode 100644
index 00000000..c11431e7
--- /dev/null
+++ b/src/comp/middle/shape.rs
@@ -0,0 +1,98 @@
+// 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; }
+        }
+    }
+}
+