+//! Codegen of the [`PointerCast::Unsize`] operation.
+//!
+//! [`PointerCast::Unsize`]: `rustc_middle::ty::adjustment::PointerCast::Unsize`
+
use crate::prelude::*;
// Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/base.rs#L159-L307
/// The `old_info` argument is a bit funny. It is intended for use
/// in an upcast, where the new vtable for an object will be derived
/// from the old one.
-pub fn unsized_info<'tcx>(
- fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+pub(crate) fn unsized_info<'tcx>(
+ fx: &mut FunctionCx<'_, '_, 'tcx>,
source: Ty<'tcx>,
target: Ty<'tcx>,
old_info: Option<Value>,
) -> Value {
let (source, target) =
- fx.tcx
- .struct_lockstep_tails_erasing_lifetimes(source, target, ParamEnv::reveal_all());
- match (&source.sty, &target.sty) {
- (&ty::Array(_, len), &ty::Slice(_)) => fx.bcx.ins().iconst(
- fx.pointer_type,
- len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64,
- ),
- (&ty::Dynamic(..), &ty::Dynamic(..)) => {
- // For now, upcasts are limited to changes in marker
- // traits, and hence never actually require an actual
- // change to the vtable.
- old_info.expect("unsized_info: missing old info for trait upcast")
+ fx.tcx.struct_lockstep_tails_erasing_lifetimes(source, target, ParamEnv::reveal_all());
+ match (&source.kind(), &target.kind()) {
+ (&ty::Array(_, len), &ty::Slice(_)) => fx
+ .bcx
+ .ins()
+ .iconst(fx.pointer_type, len.eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64),
+ (&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
+ let old_info =
+ old_info.expect("unsized_info: missing old info for trait upcasting coercion");
+ if data_a.principal_def_id() == data_b.principal_def_id() {
+ return old_info;
+ }
+
+ // trait upcasting coercion
+ let vptr_entry_idx =
+ fx.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((source, target));
+
+ if let Some(entry_idx) = vptr_entry_idx {
+ let entry_idx = u32::try_from(entry_idx).unwrap();
+ let entry_offset = entry_idx * fx.pointer_type.bytes();
+ let vptr_ptr = Pointer::new(old_info).offset_i64(fx, entry_offset.into()).load(
+ fx,
+ fx.pointer_type,
+ crate::vtable::vtable_memflags(),
+ );
+ vptr_ptr
+ } else {
+ old_info
+ }
}
(_, &ty::Dynamic(ref data, ..)) => crate::vtable::get_vtable(fx, source, data.principal()),
- _ => bug!(
- "unsized_info: invalid unsizing {:?} -> {:?}",
- source,
- target
- ),
+ _ => bug!("unsized_info: invalid unsizing {:?} -> {:?}", source, target),
}
}
-/// Coerce `src` to `dst_ty`. `src_ty` must be a thin pointer.
-pub fn unsize_thin_ptr<'tcx>(
- fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+/// Coerce `src` to `dst_ty`.
+fn unsize_ptr<'tcx>(
+ fx: &mut FunctionCx<'_, '_, 'tcx>,
src: Value,
- src_ty: Ty<'tcx>,
- dst_ty: Ty<'tcx>,
+ src_layout: TyAndLayout<'tcx>,
+ dst_layout: TyAndLayout<'tcx>,
+ old_info: Option<Value>,
) -> (Value, Value) {
- match (&src_ty.sty, &dst_ty.sty) {
+ match (&src_layout.ty.kind(), &dst_layout.ty.kind()) {
(&ty::Ref(_, a, _), &ty::Ref(_, b, _))
| (&ty::Ref(_, a, _), &ty::RawPtr(ty::TypeAndMut { ty: b, .. }))
| (&ty::RawPtr(ty::TypeAndMut { ty: a, .. }), &ty::RawPtr(ty::TypeAndMut { ty: b, .. })) => {
- assert!(!fx.layout_of(a).is_unsized());
- (src, unsized_info(fx, a, b, None))
+ (src, unsized_info(fx, *a, *b, old_info))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
- let (a, b) = (src_ty.boxed_ty(), dst_ty.boxed_ty());
- assert!(!fx.layout_of(a).is_unsized());
- (src, unsized_info(fx, a, b, None))
+ let (a, b) = (src_layout.ty.boxed_ty(), dst_layout.ty.boxed_ty());
+ (src, unsized_info(fx, a, b, old_info))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
assert_eq!(def_a, def_b);
- let src_layout = fx.layout_of(src_ty);
- let dst_layout = fx.layout_of(dst_ty);
+ if src_layout == dst_layout {
+ return (src, old_info.unwrap());
+ }
+
let mut result = None;
for i in 0..src_layout.fields.count() {
let src_f = src_layout.field(fx, i);
let dst_f = dst_layout.field(fx, i);
assert_ne!(src_f.ty, dst_f.ty);
assert_eq!(result, None);
- result = Some(unsize_thin_ptr(fx, src, src_f.ty, dst_f.ty));
+ result = Some(unsize_ptr(fx, src, src_f, dst_f, old_info));
}
result.unwrap()
}
- _ => bug!("unsize_thin_ptr: called on bad types"),
+ _ => bug!("unsize_ptr: called on bad types"),
}
}
/// Coerce `src`, which is a reference to a value of type `src_ty`,
/// to a value of type `dst_ty` and store the result in `dst`
-pub fn coerce_unsized_into<'tcx>(
- fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
+pub(crate) fn coerce_unsized_into<'tcx>(
+ fx: &mut FunctionCx<'_, '_, 'tcx>,
src: CValue<'tcx>,
dst: CPlace<'tcx>,
) {
let src_ty = src.layout().ty;
let dst_ty = dst.layout().ty;
let mut coerce_ptr = || {
- let (base, info) = if fx
- .layout_of(src.layout().ty.builtin_deref(true).unwrap().ty)
- .is_unsized()
- {
- // fat-ptr to fat-ptr unsize preserves the vtable
- // i.e., &'a fmt::Debug+Send => &'a fmt::Debug
- src.load_scalar_pair(fx)
- } else {
- let base = src.load_scalar(fx);
- unsize_thin_ptr(fx, base, src_ty, dst_ty)
- };
+ let (base, info) =
+ if fx.layout_of(src.layout().ty.builtin_deref(true).unwrap().ty).is_unsized() {
+ let (old_base, old_info) = src.load_scalar_pair(fx);
+ unsize_ptr(fx, old_base, src.layout(), dst.layout(), Some(old_info))
+ } else {
+ let base = src.load_scalar(fx);
+ unsize_ptr(fx, base, src.layout(), dst.layout(), None)
+ };
dst.write_cvalue(fx, CValue::by_val_pair(base, info, dst.layout()));
};
- match (&src_ty.sty, &dst_ty.sty) {
+ match (&src_ty.kind(), &dst_ty.kind()) {
(&ty::Ref(..), &ty::Ref(..))
| (&ty::Ref(..), &ty::RawPtr(..))
| (&ty::RawPtr(..), &ty::RawPtr(..)) => coerce_ptr(),
}
}
}
- _ => bug!(
- "coerce_unsized_into: invalid coercion {:?} -> {:?}",
- src_ty,
- dst_ty
- ),
+ _ => bug!("coerce_unsized_into: invalid coercion {:?} -> {:?}", src_ty, dst_ty),
}
}
// Adapted from https://github.com/rust-lang/rust/blob/2a663555ddf36f6b041445894a8c175cd1bc718c/src/librustc_codegen_ssa/glue.rs
-pub fn size_and_align_of_dst<'tcx>(
- fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
- ty: Ty<'tcx>,
+pub(crate) fn size_and_align_of_dst<'tcx>(
+ fx: &mut FunctionCx<'_, '_, 'tcx>,
+ layout: TyAndLayout<'tcx>,
info: Value,
) -> (Value, Value) {
- let layout = fx.layout_of(ty);
if !layout.is_unsized() {
- let size = fx
- .bcx
- .ins()
- .iconst(fx.pointer_type, layout.size.bytes() as i64);
- let align = fx
- .bcx
- .ins()
- .iconst(fx.pointer_type, layout.align.abi.bytes() as i64);
+ let size = fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64);
+ let align = fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64);
return (size, align);
}
- match ty.sty {
+ match layout.ty.kind() {
ty::Dynamic(..) => {
// load size/align from vtable
- (
- crate::vtable::size_of_obj(fx, info),
- crate::vtable::min_align_of_obj(fx, info),
- )
+ (crate::vtable::size_of_obj(fx, info), crate::vtable::min_align_of_obj(fx, info))
}
ty::Slice(_) | ty::Str => {
let unit = layout.field(fx, 0);
// times the unit size.
(
fx.bcx.ins().imul_imm(info, unit.size.bytes() as i64),
- fx.bcx
- .ins()
- .iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
+ fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
)
}
_ => {
// First get the size of all statically known fields.
// Don't use size_of because it also rounds up to alignment, which we
// want to avoid, as the unsized field's alignment could be smaller.
- assert!(!ty.is_simd());
+ assert!(!layout.ty.is_simd());
let i = layout.fields.count() - 1;
let sized_size = layout.fields.offset(i).bytes();
// Recurse to get the size of the dynamically sized field (must be
// the last field).
- let field_ty = layout.field(fx, i).ty;
- let (unsized_size, mut unsized_align) = size_and_align_of_dst(fx, field_ty, info);
+ let field_layout = layout.field(fx, i);
+ let (unsized_size, mut unsized_align) = size_and_align_of_dst(fx, field_layout, info);
// FIXME (#26403, #27023): We should be adding padding
// to `sized_size` (to accommodate the `unsized_align`
let size = fx.bcx.ins().iadd_imm(unsized_size, sized_size as i64);
// Packed types ignore the alignment of their fields.
- if let ty::Adt(def, _) = ty.sty {
+ if let ty::Adt(def, _) = layout.ty.kind() {
if def.repr.packed() {
unsized_align = sized_align;
}
// Choose max of two known alignments (combined value must
// be aligned according to more restrictive of the two).
- let cmp = fx
- .bcx
- .ins()
- .icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
+ let cmp = fx.bcx.ins().icmp(IntCC::UnsignedGreaterThan, sized_align, unsized_align);
let align = fx.bcx.ins().select(cmp, sized_align, unsized_align);
// Issue #27023: must add any necessary padding to `size`
// `(size + (align-1)) & -align`
let addend = fx.bcx.ins().iadd_imm(align, -1);
let add = fx.bcx.ins().iadd(size, addend);
- let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
- let neg = fx.bcx.ins().isub(zero, align);
+ let neg = fx.bcx.ins().ineg(align);
let size = fx.bcx.ins().band(add, neg);
(size, align)
projects / rust.git / blobdiff