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rustc_codegen_ssa: remove some unnecessary Box special-casing. #65448

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merged 1 commit into from
Oct 19, 2019
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rustc_codegen_ssa: remove some unnecessary Box special-casing. #65448

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46 changes: 19 additions & 27 deletions src/librustc_codegen_ssa/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -168,12 +168,6 @@ pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
let ptr_ty = bx.cx().type_ptr_to(bx.cx().backend_type(bx.cx().layout_of(b)));
(bx.pointercast(src, ptr_ty), unsized_info(bx.cx(), a, b, None))
}
(&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!(bx.cx().type_is_sized(a));
let ptr_ty = bx.cx().type_ptr_to(bx.cx().backend_type(bx.cx().layout_of(b)));
(bx.pointercast(src, ptr_ty), unsized_info(bx.cx(), a, b, None))
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
assert_eq!(def_a, def_b);

Expand All @@ -196,6 +190,8 @@ pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
}
let (lldata, llextra) = result.unwrap();
// HACK(eddyb) have to bitcast pointers until LLVM removes pointee types.
// FIXME(eddyb) move these out of this `match` arm, so they're always
// applied, uniformly, no matter the source/destination types.
(bx.bitcast(lldata, bx.cx().scalar_pair_element_backend_type(dst_layout, 0, true)),
bx.bitcast(llextra, bx.cx().scalar_pair_element_backend_type(dst_layout, 1, true)))
}
Expand All @@ -212,31 +208,27 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
) {
let src_ty = src.layout.ty;
let dst_ty = dst.layout.ty;
let mut coerce_ptr = || {
let (base, info) = match bx.load_operand(src).val {
OperandValue::Pair(base, info) => {
// fat-ptr to fat-ptr unsize preserves the vtable
// i.e., &'a fmt::Debug+Send => &'a fmt::Debug
// So we need to pointercast the base to ensure
// the types match up.
let thin_ptr = dst.layout.field(bx.cx(), FAT_PTR_ADDR);
(bx.pointercast(base, bx.cx().backend_type(thin_ptr)), info)
}
OperandValue::Immediate(base) => {
unsize_thin_ptr(bx, base, src_ty, dst_ty)
}
OperandValue::Ref(..) => bug!()
};
OperandValue::Pair(base, info).store(bx, dst);
};
match (&src_ty.kind, &dst_ty.kind) {
(&ty::Ref(..), &ty::Ref(..)) |
(&ty::Ref(..), &ty::RawPtr(..)) |
(&ty::RawPtr(..), &ty::RawPtr(..)) => {
coerce_ptr()
}
(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
coerce_ptr()
let (base, info) = match bx.load_operand(src).val {
OperandValue::Pair(base, info) => {
// fat-ptr to fat-ptr unsize preserves the vtable
// i.e., &'a fmt::Debug+Send => &'a fmt::Debug
// So we need to pointercast the base to ensure
// the types match up.
// FIXME(eddyb) use `scalar_pair_element_backend_type` here,
// like `unsize_thin_ptr` does.
let thin_ptr = dst.layout.field(bx.cx(), FAT_PTR_ADDR);
(bx.pointercast(base, bx.cx().backend_type(thin_ptr)), info)
}
OperandValue::Immediate(base) => {
unsize_thin_ptr(bx, base, src_ty, dst_ty)
}
OperandValue::Ref(..) => bug!()
};
OperandValue::Pair(base, info).store(bx, dst);
}

(&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
Expand Down