use crate::traits::*; use rustc_middle::ty::{self, subst::GenericArgKind, Ty}; use rustc_session::config::Lto; use rustc_symbol_mangling::typeid_for_trait_ref; 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>( self, bx: &mut Bx, llvtable: Bx::Value, ty: Ty<'tcx>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, ) -> Bx::Value { // Load the data pointer from the object. debug!("get_fn({llvtable:?}, {ty:?}, {self:?})"); let llty = bx.fn_ptr_backend_type(fn_abi); let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty)); if bx.cx().sess().opts.unstable_opts.virtual_function_elimination && bx.cx().sess().lto() == Lto::Fat { let typeid = bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), expect_dyn_trait_in_self(ty))); let vtable_byte_offset = self.0 * bx.data_layout().pointer_size.bytes(); let type_checked_load = bx.type_checked_load(llvtable, vtable_byte_offset, typeid); let func = bx.extract_value(type_checked_load, 0); bx.pointercast(func, llty) } else { 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>( 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 } } /// This takes a valid `self` receiver type and extracts the principal trait /// ref of the type. fn expect_dyn_trait_in_self<'tcx>(ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'tcx> { for arg in ty.peel_refs().walk() { if let GenericArgKind::Type(ty) = arg.unpack() { if let ty::Dynamic(data, _, _) = ty.kind() { return data.principal().expect("expected principal trait object"); } } } bug!("expected a `dyn Trait` ty, found {ty:?}") } /// 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` from a value of type `Foo`, then /// `trait_ref` would map `T: Trait`. #[instrument(level = "debug", skip(cx))] pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>( cx: &Cx, ty: Ty<'tcx>, trait_ref: Option>, ) -> Cx::Value { let tcx = cx.tcx(); // 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_debuginfo(ty, trait_ref, vtable); cx.vtables().borrow_mut().insert((ty, trait_ref), vtable); vtable }