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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());
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(),
)
})
});
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
}
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