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use crate::traits::*;
use rustc_middle::ty::{self, 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<Bx: BuilderMethods<'a, 'tcx>>(
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);
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)))
.unwrap();
let vtable_byte_offset = self.0 * bx.data_layout().pointer_size.bytes();
let func = bx.type_checked_load(llvtable, vtable_byte_offset, typeid);
func
} 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<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 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(ty: Ty<'_>) -> ty::PolyExistentialTraitRef<'_> {
for arg in ty.peel_refs().walk() {
if let GenericArgKind::Type(ty) = arg.unpack()
&& 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<dyn Trait>` from a value of type `Foo<T>`, 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<ty::PolyExistentialTraitRef<'tcx>>,
) -> 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
}
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