src/librustc_trans/meth.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::ValueRef;
  12 use callee;
  13 use common::*;
  14 use builder::Builder;
  15 use consts;
  16 use machine;
  17 use monomorphize;
  18 use type_::Type;
  19 use value::Value;
  20 use rustc::ty::{self, Ty};
  21 use debuginfo;
  22
  23 #[derive(Copy, Clone, Debug)]
  24 pub struct VirtualIndex(usize);
  25
  26 pub const DESTRUCTOR: VirtualIndex = VirtualIndex(0);
  27 pub const SIZE: VirtualIndex = VirtualIndex(1);
  28 pub const ALIGN: VirtualIndex = VirtualIndex(2);
  29
  30 impl<'a, 'tcx> VirtualIndex {
  31     pub fn from_index(index: usize) -> Self {
  32         VirtualIndex(index + 3)
  33     }
  34
  35     pub fn get_fn(self, bcx: &Builder<'a, 'tcx>, llvtable: ValueRef) -> ValueRef {
  36         // Load the data pointer from the object.
  37         debug!("get_fn({:?}, {:?})", Value(llvtable), self);
  38
  39         let ptr = bcx.load_nonnull(bcx.gepi(llvtable, &[self.0]), None);
  40         // Vtable loads are invariant
  41         bcx.set_invariant_load(ptr);
  42         ptr
  43     }
  44
  45     pub fn get_usize(self, bcx: &Builder<'a, 'tcx>, llvtable: ValueRef) -> ValueRef {
  46         // Load the data pointer from the object.
  47         debug!("get_int({:?}, {:?})", Value(llvtable), self);
  48
  49         let llvtable = bcx.pointercast(llvtable, Type::isize(bcx.ccx).ptr_to());
  50         let ptr = bcx.load(bcx.gepi(llvtable, &[self.0]), None);
  51         // Vtable loads are invariant
  52         bcx.set_invariant_load(ptr);
  53         ptr
  54     }
  55 }
  56
  57 /// Creates a dynamic vtable for the given type and vtable origin.
  58 /// This is used only for objects.
  59 ///
  60 /// The vtables are cached instead of created on every call.
  61 ///
  62 /// The `trait_ref` encodes the erased self type. Hence if we are
  63 /// making an object `Foo<Trait>` from a value of type `Foo<T>`, then
  64 /// `trait_ref` would map `T:Trait`.
  65 pub fn get_vtable<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
  66                             ty: Ty<'tcx>,
  67                             trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>)
  68                             -> ValueRef
  69 {
  70     let tcx = ccx.tcx();
  71
  72     debug!("get_vtable(ty={:?}, trait_ref={:?})", ty, trait_ref);
  73
  74     // Check the cache.
  75     if let Some(&val) = ccx.vtables().borrow().get(&(ty, trait_ref)) {
  76         return val;
  77     }
  78
  79     // Not in the cache. Build it.
  80     let nullptr = C_null(Type::nil(ccx).ptr_to());
  81
  82     let mut components: Vec<_> = [
  83         callee::get_fn(ccx, monomorphize::resolve_drop_in_place(ccx.tcx(), ty)),
  84         C_usize(ccx, ccx.size_of(ty)),
  85         C_usize(ccx, ccx.align_of(ty) as u64)
  86     ].iter().cloned().collect();
  87
  88     if let Some(trait_ref) = trait_ref {
  89         let trait_ref = trait_ref.with_self_ty(tcx, ty);
  90         let methods = tcx.vtable_methods(trait_ref);
  91         let methods = methods.iter().cloned().map(|opt_mth| {
  92             opt_mth.map_or(nullptr, |(def_id, substs)| {
  93                 callee::resolve_and_get_fn(ccx, def_id, substs)
  94             })
  95         });
  96         components.extend(methods);
  97     }
  98
  99     let vtable_const = C_struct(ccx, &components, false);
 100     let align = machine::llalign_of_pref(ccx, val_ty(vtable_const));
 101     let vtable = consts::addr_of(ccx, vtable_const, align, "vtable");
 102
 103     debuginfo::create_vtable_metadata(ccx, ty, vtable);
 104
 105     ccx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
 106     vtable
 107 }