1 files changed, 126 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_ssa/src/meth.rs b/compiler/rustc_codegen_ssa/src/meth.rs
new file mode 100644
index 00000000000..bcc19c6a44b
--- /dev/null
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -0,0 +1,126 @@
+use crate::traits::*;
+
+use rustc_middle::ty::{self, Instance, Ty};
+use rustc_target::abi::call::FnAbi;
+
+#[derive(Copy, Clone, Debug)]
+pub struct VirtualIndex(u64);
+
+pub const DESTRUCTOR: VirtualIndex = VirtualIndex(0);
+pub const SIZE: VirtualIndex = VirtualIndex(1);
+pub const ALIGN: VirtualIndex = VirtualIndex(2);
+
+impl<'a, 'tcx> VirtualIndex {
+    pub fn from_index(index: usize) -> Self {
+        VirtualIndex(index as u64 + 3)
+    }
+
+    pub fn get_fn<Bx: BuilderMethods<'a, 'tcx>>(
+        self,
+        bx: &mut Bx,
+        llvtable: Bx::Value,
+        fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
+    ) -> Bx::Value {
+        // Load the data pointer from the object.
+        debug!("get_fn({:?}, {:?})", llvtable, self);
+
+        let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(bx.fn_ptr_backend_type(fn_abi)));
+        let ptr_align = bx.tcx().data_layout.pointer_align.abi;
+        let gep = bx.inbounds_gep(llvtable, &[bx.const_usize(self.0)]);
+        let ptr = bx.load(gep, ptr_align);
+        bx.nonnull_metadata(ptr);
+        // Vtable loads are invariant.
+        bx.set_invariant_load(ptr);
+        ptr
+    }
+
+    pub fn get_usize<Bx: BuilderMethods<'a, 'tcx>>(
+        self,
+        bx: &mut Bx,
+        llvtable: Bx::Value,
+    ) -> Bx::Value {
+        // Load the data pointer from the object.
+        debug!("get_int({:?}, {:?})", llvtable, self);
+
+        let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(bx.type_isize()));
+        let usize_align = bx.tcx().data_layout.pointer_align.abi;
+        let gep = bx.inbounds_gep(llvtable, &[bx.const_usize(self.0)]);
+        let ptr = bx.load(gep, usize_align);
+        // Vtable loads are invariant.
+        bx.set_invariant_load(ptr);
+        ptr
+    }
+}
+
+/// Creates a dynamic vtable for the given type and vtable origin.
+/// This is used only for objects.
+///
+/// The vtables are cached instead of created on every call.
+///
+/// The `trait_ref` encodes the erased self type. Hence if we are
+/// making an object `Foo<dyn Trait>` from a value of type `Foo<T>`, then
+/// `trait_ref` would map `T: Trait`.
+pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
+    cx: &Cx,
+    ty: Ty<'tcx>,
+    trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
+) -> Cx::Value {
+    let tcx = cx.tcx();
+
+    debug!("get_vtable(ty={:?}, trait_ref={:?})", ty, trait_ref);
+
+    // Check the cache.
+    if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
+        return val;
+    }
+
+    // Not in the cache; build it.
+    let nullptr = cx.const_null(cx.type_i8p_ext(cx.data_layout().instruction_address_space));
+
+    let methods_root;
+    let methods = if let Some(trait_ref) = trait_ref {
+        methods_root = tcx.vtable_methods(trait_ref.with_self_ty(tcx, ty));
+        methods_root.iter()
+    } else {
+        (&[]).iter()
+    };
+
+    let methods = methods.cloned().map(|opt_mth| {
+        opt_mth.map_or(nullptr, |(def_id, substs)| {
+            cx.get_fn_addr(
+                ty::Instance::resolve_for_vtable(
+                    cx.tcx(),
+                    ty::ParamEnv::reveal_all(),
+                    def_id,
+                    substs,
+                )
+                .unwrap()
+                .polymorphize(cx.tcx()),
+            )
+        })
+    });
+
+    let layout = cx.layout_of(ty);
+    // /////////////////////////////////////////////////////////////////////////////////////////////
+    // If you touch this code, be sure to also make the corresponding changes to
+    // `get_vtable` in `rust_mir/interpret/traits.rs`.
+    // /////////////////////////////////////////////////////////////////////////////////////////////
+    let components: Vec<_> = [
+        cx.get_fn_addr(Instance::resolve_drop_in_place(cx.tcx(), ty)),
+        cx.const_usize(layout.size.bytes()),
+        cx.const_usize(layout.align.abi.bytes()),
+    ]
+    .iter()
+    .cloned()
+    .chain(methods)
+    .collect();
+
+    let vtable_const = cx.const_struct(&components, false);
+    let align = cx.data_layout().pointer_align.abi;
+    let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
+
+    cx.create_vtable_metadata(ty, vtable);
+
+    cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
+    vtable
+}