Finish removing struct layout dependencies from glue.

Author: jld

src/librustc/middle/trans/adt.rs

@@ -266,6 +266,14 @@ fn struct_GEP(bcx: block, st: &Struct, val: ValueRef, ix: uint,
     GEPi(bcx, val, [0, ix])
 }
 
+pub fn trans_drop_flag_ptr(bcx: block, r: &Repr, val: ValueRef) -> ValueRef {
+    match *r {
+        Univariant(_, DtorPresent) => GEPi(bcx, val, [0, 1]),
+        _ => bcx.ccx().sess.bug(~"tried to get drop flag of non-droppable \
+                                  type")
+    }
+}
+
 pub fn trans_const(ccx: @CrateContext, r: &Repr, discr: int,
                    vals: &[ValueRef]) -> ValueRef {
     match *r {

src/librustc/middle/trans/glue.rs

@@ -468,7 +468,8 @@ pub fn trans_struct_drop(bcx: block,
                          substs: &ty::substs,
                          take_ref: bool)
                       -> block {
-    let drop_flag = GEPi(bcx, v0, struct_dtor());
+    let repr = adt::represent_type(bcx.ccx(), t);
+    let drop_flag = adt::trans_drop_flag_ptr(bcx, &repr, v0);
     do with_cond(bcx, IsNotNull(bcx, Load(bcx, drop_flag))) |cx| {
         let mut bcx = cx;
 
@@ -502,7 +503,6 @@ pub fn trans_struct_drop(bcx: block,
         Call(bcx, dtor_addr, args);
 
         // Drop the fields
-        let repr = adt::represent_type(bcx.ccx(), t);
         let field_tys =
             ty::struct_mutable_fields(bcx.tcx(), class_did,
                                               substs);