1 files changed, 84 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..efeec5b7284
--- /dev/null
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -0,0 +1,84 @@
+use crate::traits::*;
+
+use rustc_middle::ty::{self, Ty};
+use rustc_target::abi::call::FnAbi;
+
+#[derive(Copy, Clone, Debug)]
+pub struct VirtualIndex(u64);
+
+impl<'a, 'tcx> VirtualIndex {
+    pub fn from_index(index: usize) -> Self {
+        VirtualIndex(index as u64)
+    }
+
+    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 llty = bx.fn_ptr_backend_type(fn_abi);
+        let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
+        let ptr_align = bx.tcx().data_layout.pointer_align.abi;
+        let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
+        let ptr = bx.load(llty, 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 llty = bx.type_isize();
+        let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
+        let usize_align = bx.tcx().data_layout.pointer_align.abi;
+        let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
+        let ptr = bx.load(llty, 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;
+    }
+
+    let vtable_alloc_id = tcx.vtable_allocation(ty, trait_ref);
+    let vtable_allocation = tcx.global_alloc(vtable_alloc_id).unwrap_memory();
+    let vtable_const = cx.const_data_from_alloc(vtable_allocation);
+    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
+}