112 lines
3.9 KiB
Rust
112 lines
3.9 KiB
Rust
use crate::traits::*;
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use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
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use rustc_session::config::Lto;
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use rustc_symbol_mangling::typeid_for_trait_ref;
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use rustc_target::abi::call::FnAbi;
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#[derive(Copy, Clone, Debug)]
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pub struct VirtualIndex(u64);
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impl<'a, 'tcx> VirtualIndex {
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pub fn from_index(index: usize) -> Self {
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VirtualIndex(index as u64)
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}
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pub fn get_fn<Bx: BuilderMethods<'a, 'tcx>>(
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self,
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bx: &mut Bx,
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llvtable: Bx::Value,
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ty: Ty<'tcx>,
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fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
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) -> Bx::Value {
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// Load the data pointer from the object.
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debug!("get_fn({llvtable:?}, {ty:?}, {self:?})");
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let llty = bx.fn_ptr_backend_type(fn_abi);
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let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
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if bx.cx().sess().opts.unstable_opts.virtual_function_elimination
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&& bx.cx().sess().lto() == Lto::Fat
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{
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let typeid =
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bx.typeid_metadata(typeid_for_trait_ref(bx.tcx(), expect_dyn_trait_in_self(ty)));
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let vtable_byte_offset = self.0 * bx.data_layout().pointer_size.bytes();
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let type_checked_load = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
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let func = bx.extract_value(type_checked_load, 0);
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bx.pointercast(func, llty)
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} else {
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let ptr_align = bx.tcx().data_layout.pointer_align.abi;
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let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
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let ptr = bx.load(llty, gep, ptr_align);
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bx.nonnull_metadata(ptr);
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// VTable loads are invariant.
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bx.set_invariant_load(ptr);
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ptr
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}
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}
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pub fn get_usize<Bx: BuilderMethods<'a, 'tcx>>(
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self,
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bx: &mut Bx,
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llvtable: Bx::Value,
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) -> Bx::Value {
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// Load the data pointer from the object.
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debug!("get_int({:?}, {:?})", llvtable, self);
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let llty = bx.type_isize();
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let llvtable = bx.pointercast(llvtable, bx.type_ptr_to(llty));
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let usize_align = bx.tcx().data_layout.pointer_align.abi;
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let gep = bx.inbounds_gep(llty, llvtable, &[bx.const_usize(self.0)]);
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let ptr = bx.load(llty, gep, usize_align);
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// VTable loads are invariant.
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bx.set_invariant_load(ptr);
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ptr
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}
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}
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/// This takes a valid `self` receiver type and extracts the principal trait
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/// ref of the type.
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fn expect_dyn_trait_in_self<'tcx>(ty: Ty<'tcx>) -> ty::PolyExistentialTraitRef<'tcx> {
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for arg in ty.peel_refs().walk() {
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if let GenericArgKind::Type(ty) = arg.unpack() {
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if let ty::Dynamic(data, _, _) = ty.kind() {
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return data.principal().expect("expected principal trait object");
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}
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}
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}
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bug!("expected a `dyn Trait` ty, found {ty:?}")
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}
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/// Creates a dynamic vtable for the given type and vtable origin.
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/// This is used only for objects.
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///
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/// The vtables are cached instead of created on every call.
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///
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/// The `trait_ref` encodes the erased self type. Hence if we are
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/// making an object `Foo<dyn Trait>` from a value of type `Foo<T>`, then
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/// `trait_ref` would map `T: Trait`.
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#[instrument(level = "debug", skip(cx))]
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pub fn get_vtable<'tcx, Cx: CodegenMethods<'tcx>>(
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cx: &Cx,
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ty: Ty<'tcx>,
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trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
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) -> Cx::Value {
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let tcx = cx.tcx();
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// Check the cache.
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if let Some(&val) = cx.vtables().borrow().get(&(ty, trait_ref)) {
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return val;
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}
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let vtable_alloc_id = tcx.vtable_allocation((ty, trait_ref));
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let vtable_allocation = tcx.global_alloc(vtable_alloc_id).unwrap_memory();
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let vtable_const = cx.const_data_from_alloc(vtable_allocation);
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let align = cx.data_layout().pointer_align.abi;
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let vtable = cx.static_addr_of(vtable_const, align, Some("vtable"));
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cx.create_vtable_debuginfo(ty, trait_ref, vtable);
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cx.vtables().borrow_mut().insert((ty, trait_ref), vtable);
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vtable
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}
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