1 use super::operand::OperandValue;
2 use super::{FunctionCx, LocalRef};
4 use crate::common::IntPredicate;
10 use rustc::mir::tcx::PlaceTy;
11 use rustc::ty::layout::{self, Align, HasTyCtxt, LayoutOf, TyLayout, VariantIdx};
12 use rustc::ty::{self, Ty};
14 #[derive(Copy, Clone, Debug)]
15 pub struct PlaceRef<'tcx, V> {
16 /// A pointer to the contents of the place.
19 /// This place's extra data if it is unsized, or `None` if null.
20 pub llextra: Option<V>,
22 /// The monomorphized type of this place, including variant information.
23 pub layout: TyLayout<'tcx>,
25 /// The alignment we know for this place.
29 impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
30 pub fn new_sized(llval: V, layout: TyLayout<'tcx>) -> PlaceRef<'tcx, V> {
31 assert!(!layout.is_unsized());
32 PlaceRef { llval, llextra: None, layout, align: layout.align.abi }
35 pub fn new_sized_aligned(llval: V, layout: TyLayout<'tcx>, align: Align) -> PlaceRef<'tcx, V> {
36 assert!(!layout.is_unsized());
37 PlaceRef { llval, llextra: None, layout, align }
40 // FIXME(eddyb) pass something else for the name so no work is done
41 // unless LLVM IR names are turned on (e.g. for `--emit=llvm-ir`).
42 pub fn alloca<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
44 layout: TyLayout<'tcx>,
46 assert!(!layout.is_unsized(), "tried to statically allocate unsized place");
47 let tmp = bx.alloca(bx.cx().backend_type(layout), layout.align.abi);
48 Self::new_sized(tmp, layout)
51 /// Returns a place for an indirect reference to an unsized place.
52 // FIXME(eddyb) pass something else for the name so no work is done
53 // unless LLVM IR names are turned on (e.g. for `--emit=llvm-ir`).
54 pub fn alloca_unsized_indirect<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
56 layout: TyLayout<'tcx>,
58 assert!(layout.is_unsized(), "tried to allocate indirect place for sized values");
59 let ptr_ty = bx.cx().tcx().mk_mut_ptr(layout.ty);
60 let ptr_layout = bx.cx().layout_of(ptr_ty);
61 Self::alloca(bx, ptr_layout)
64 pub fn len<Cx: ConstMethods<'tcx, Value = V>>(&self, cx: &Cx) -> V {
65 if let layout::FieldPlacement::Array { count, .. } = self.layout.fields {
66 if self.layout.is_unsized() {
73 bug!("unexpected layout `{:#?}` in PlaceRef::len", self.layout)
78 impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
79 /// Access a field, at a point when the value's case is known.
80 pub fn project_field<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
85 let field = self.layout.field(bx.cx(), ix);
86 let offset = self.layout.fields.offset(ix);
87 let effective_field_align = self.align.restrict_for_offset(offset);
90 // Unions and newtypes only use an offset of 0.
91 let llval = if offset.bytes() == 0 {
93 } else if let layout::Abi::ScalarPair(ref a, ref b) = self.layout.abi {
94 // Offsets have to match either first or second field.
95 assert_eq!(offset, a.value.size(bx.cx()).align_to(b.value.align(bx.cx()).abi));
96 bx.struct_gep(self.llval, 1)
98 bx.struct_gep(self.llval, bx.cx().backend_field_index(self.layout, ix))
101 // HACK(eddyb): have to bitcast pointers until LLVM removes pointee types.
102 llval: bx.pointercast(llval, bx.cx().type_ptr_to(bx.cx().backend_type(field))),
103 llextra: if bx.cx().type_has_metadata(field.ty) { self.llextra } else { None },
105 align: effective_field_align,
109 // Simple cases, which don't need DST adjustment:
110 // * no metadata available - just log the case
111 // * known alignment - sized types, `[T]`, `str` or a foreign type
112 // * packed struct - there is no alignment padding
113 match field.ty.kind {
114 _ if self.llextra.is_none() => {
116 "unsized field `{}`, of `{:?}` has no metadata for adjustment",
121 _ if !field.is_unsized() => return simple(),
122 ty::Slice(..) | ty::Str | ty::Foreign(..) => return simple(),
124 if def.repr.packed() {
125 // FIXME(eddyb) generalize the adjustment when we
126 // start supporting packing to larger alignments.
127 assert_eq!(self.layout.align.abi.bytes(), 1);
134 // We need to get the pointer manually now.
135 // We do this by casting to a `*i8`, then offsetting it by the appropriate amount.
136 // We do this instead of, say, simply adjusting the pointer from the result of a GEP
137 // because the field may have an arbitrary alignment in the LLVM representation
142 // struct Foo<T: ?Sized> {
147 // The type `Foo<Foo<Trait>>` is represented in LLVM as `{ u16, { u16, u8 }}`, meaning that
148 // the `y` field has 16-bit alignment.
150 let meta = self.llextra;
152 let unaligned_offset = bx.cx().const_usize(offset.bytes());
154 // Get the alignment of the field
155 let (_, unsized_align) = glue::size_and_align_of_dst(bx, field.ty, meta);
157 // Bump the unaligned offset up to the appropriate alignment using the
158 // following expression:
160 // (unaligned offset + (align - 1)) & -align
163 let align_sub_1 = bx.sub(unsized_align, bx.cx().const_usize(1u64));
164 let and_lhs = bx.add(unaligned_offset, align_sub_1);
165 let and_rhs = bx.neg(unsized_align);
166 let offset = bx.and(and_lhs, and_rhs);
168 debug!("struct_field_ptr: DST field offset: {:?}", offset);
170 // Cast and adjust pointer.
171 let byte_ptr = bx.pointercast(self.llval, bx.cx().type_i8p());
172 let byte_ptr = bx.gep(byte_ptr, &[offset]);
174 // Finally, cast back to the type expected.
175 let ll_fty = bx.cx().backend_type(field);
176 debug!("struct_field_ptr: Field type is {:?}", ll_fty);
179 llval: bx.pointercast(byte_ptr, bx.cx().type_ptr_to(ll_fty)),
180 llextra: self.llextra,
182 align: effective_field_align,
186 /// Obtain the actual discriminant of a value.
187 pub fn codegen_get_discr<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
192 let cast_to = bx.cx().immediate_backend_type(bx.cx().layout_of(cast_to));
193 if self.layout.abi.is_uninhabited() {
194 return bx.cx().const_undef(cast_to);
196 let (discr_scalar, discr_kind, discr_index) = match self.layout.variants {
197 layout::Variants::Single { index } => {
201 .discriminant_for_variant(bx.cx().tcx(), index)
202 .map_or(index.as_u32() as u128, |discr| discr.val);
203 return bx.cx().const_uint_big(cast_to, discr_val);
205 layout::Variants::Multiple { ref discr, ref discr_kind, discr_index, .. } => {
206 (discr, discr_kind, discr_index)
210 // Read the tag/niche-encoded discriminant from memory.
211 let encoded_discr = self.project_field(bx, discr_index);
212 let encoded_discr = bx.load_operand(encoded_discr);
214 // Decode the discriminant (specifically if it's niche-encoded).
216 layout::DiscriminantKind::Tag => {
217 let signed = match discr_scalar.value {
218 // We use `i1` for bytes that are always `0` or `1`,
219 // e.g., `#[repr(i8)] enum E { A, B }`, but we can't
220 // let LLVM interpret the `i1` as signed, because
221 // then `i1 1` (i.e., `E::B`) is effectively `i8 -1`.
222 layout::Int(_, signed) => !discr_scalar.is_bool() && signed,
225 bx.intcast(encoded_discr.immediate(), cast_to, signed)
227 layout::DiscriminantKind::Niche {
232 // Rebase from niche values to discriminants, and check
233 // whether the result is in range for the niche variants.
234 let niche_llty = bx.cx().immediate_backend_type(encoded_discr.layout);
235 let encoded_discr = encoded_discr.immediate();
237 // We first compute the "relative discriminant" (wrt `niche_variants`),
238 // that is, if `n = niche_variants.end() - niche_variants.start()`,
239 // we remap `niche_start..=niche_start + n` (which may wrap around)
240 // to (non-wrap-around) `0..=n`, to be able to check whether the
241 // discriminant corresponds to a niche variant with one comparison.
242 // We also can't go directly to the (variant index) discriminant
243 // and check that it is in the range `niche_variants`, because
244 // that might not fit in the same type, on top of needing an extra
245 // comparison (see also the comment on `let niche_discr`).
246 let relative_discr = if niche_start == 0 {
247 // Avoid subtracting `0`, which wouldn't work for pointers.
248 // FIXME(eddyb) check the actual primitive type here.
251 bx.sub(encoded_discr, bx.cx().const_uint_big(niche_llty, niche_start))
253 let relative_max = niche_variants.end().as_u32() - niche_variants.start().as_u32();
255 let relative_max = if relative_max == 0 {
256 // Avoid calling `const_uint`, which wouldn't work for pointers.
257 // FIXME(eddyb) check the actual primitive type here.
258 bx.cx().const_null(niche_llty)
260 bx.cx().const_uint(niche_llty, relative_max as u64)
262 bx.icmp(IntPredicate::IntULE, relative_discr, relative_max)
265 // NOTE(eddyb) this addition needs to be performed on the final
266 // type, in case the niche itself can't represent all variant
267 // indices (e.g. `u8` niche with more than `256` variants,
268 // but enough uninhabited variants so that the remaining variants
269 // fit in the niche).
270 // In other words, `niche_variants.end - niche_variants.start`
271 // is representable in the niche, but `niche_variants.end`
272 // might not be, in extreme cases.
274 let relative_discr = if relative_max == 0 {
275 // HACK(eddyb) since we have only one niche, we know which
276 // one it is, and we can avoid having a dynamic value here.
277 bx.cx().const_uint(cast_to, 0)
279 bx.intcast(relative_discr, cast_to, false)
283 bx.cx().const_uint(cast_to, niche_variants.start().as_u32() as u64),
290 bx.cx().const_uint(cast_to, dataful_variant.as_u32() as u64),
296 /// Sets the discriminant for a new value of the given case of the given
298 pub fn codegen_set_discr<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
301 variant_index: VariantIdx,
303 if self.layout.for_variant(bx.cx(), variant_index).abi.is_uninhabited() {
304 // We play it safe by using a well-defined `abort`, but we could go for immediate UB
305 // if that turns out to be helpful.
309 match self.layout.variants {
310 layout::Variants::Single { index } => {
311 assert_eq!(index, variant_index);
313 layout::Variants::Multiple {
314 discr_kind: layout::DiscriminantKind::Tag,
318 let ptr = self.project_field(bx, discr_index);
320 self.layout.ty.discriminant_for_variant(bx.tcx(), variant_index).unwrap().val;
322 bx.cx().const_uint_big(bx.cx().backend_type(ptr.layout), to),
327 layout::Variants::Multiple {
329 layout::DiscriminantKind::Niche { dataful_variant, ref niche_variants, niche_start },
333 if variant_index != dataful_variant {
334 if bx.cx().sess().target.target.arch == "arm"
335 || bx.cx().sess().target.target.arch == "aarch64"
337 // FIXME(#34427): as workaround for LLVM bug on ARM,
338 // use memset of 0 before assigning niche value.
339 let fill_byte = bx.cx().const_u8(0);
340 let size = bx.cx().const_usize(self.layout.size.bytes());
341 bx.memset(self.llval, fill_byte, size, self.align, MemFlags::empty());
344 let niche = self.project_field(bx, discr_index);
345 let niche_llty = bx.cx().immediate_backend_type(niche.layout);
346 let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
347 let niche_value = (niche_value as u128).wrapping_add(niche_start);
348 // FIXME(eddyb): check the actual primitive type here.
349 let niche_llval = if niche_value == 0 {
350 // HACK(eddyb): using `c_null` as it works on all types.
351 bx.cx().const_null(niche_llty)
353 bx.cx().const_uint_big(niche_llty, niche_value)
355 OperandValue::Immediate(niche_llval).store(bx, niche);
361 pub fn project_index<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
366 // Statically compute the offset if we can, otherwise just use the element size,
367 // as this will yield the lowest alignment.
368 let layout = self.layout.field(bx, 0);
369 let offset = if let Some(llindex) = bx.const_to_opt_uint(llindex) {
370 layout.size.checked_mul(llindex, bx).unwrap_or(layout.size)
376 llval: bx.inbounds_gep(self.llval, &[bx.cx().const_usize(0), llindex]),
379 align: self.align.restrict_for_offset(offset),
383 pub fn project_downcast<Bx: BuilderMethods<'a, 'tcx, Value = V>>(
386 variant_index: VariantIdx,
388 let mut downcast = *self;
389 downcast.layout = self.layout.for_variant(bx.cx(), variant_index);
391 // Cast to the appropriate variant struct type.
392 let variant_ty = bx.cx().backend_type(downcast.layout);
393 downcast.llval = bx.pointercast(downcast.llval, bx.cx().type_ptr_to(variant_ty));
398 pub fn storage_live<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
399 bx.lifetime_start(self.llval, self.layout.size);
402 pub fn storage_dead<Bx: BuilderMethods<'a, 'tcx, Value = V>>(&self, bx: &mut Bx) {
403 bx.lifetime_end(self.llval, self.layout.size);
407 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
408 pub fn codegen_place(
411 place_ref: &mir::PlaceRef<'_, 'tcx>,
412 ) -> PlaceRef<'tcx, Bx::Value> {
413 debug!("codegen_place(place_ref={:?})", place_ref);
415 let tcx = self.cx.tcx();
417 let result = match place_ref {
418 mir::PlaceRef { local, projection: [] } => match self.locals[**local] {
419 LocalRef::Place(place) => {
422 LocalRef::UnsizedPlace(place) => {
423 return bx.load_operand(place).deref(cx);
425 LocalRef::Operand(..) => {
426 bug!("using operand local {:?} as place", place_ref);
429 mir::PlaceRef { local, projection: [proj_base @ .., mir::ProjectionElem::Deref] } => {
430 // Load the pointer from its location.
431 self.codegen_consume(bx, &mir::PlaceRef { local, projection: proj_base })
434 mir::PlaceRef { local, projection: [proj_base @ .., elem] } => {
435 // FIXME turn this recursion into iteration
437 self.codegen_place(bx, &mir::PlaceRef { local, projection: proj_base });
440 mir::ProjectionElem::Deref => bug!(),
441 mir::ProjectionElem::Field(ref field, _) => {
442 cg_base.project_field(bx, field.index())
444 mir::ProjectionElem::Index(index) => {
445 let index = &mir::Operand::Copy(mir::Place::from(*index));
446 let index = self.codegen_operand(bx, index);
447 let llindex = index.immediate();
448 cg_base.project_index(bx, llindex)
450 mir::ProjectionElem::ConstantIndex {
455 let lloffset = bx.cx().const_usize(*offset as u64);
456 cg_base.project_index(bx, lloffset)
458 mir::ProjectionElem::ConstantIndex {
463 let lloffset = bx.cx().const_usize(*offset as u64);
464 let lllen = cg_base.len(bx.cx());
465 let llindex = bx.sub(lllen, lloffset);
466 cg_base.project_index(bx, llindex)
468 mir::ProjectionElem::Subslice { from, to, from_end } => {
470 cg_base.project_index(bx, bx.cx().const_usize(*from as u64));
472 PlaceTy::from_ty(cg_base.layout.ty).projection_ty(tcx, elem).ty;
473 subslice.layout = bx.cx().layout_of(self.monomorphize(&projected_ty));
475 if subslice.layout.is_unsized() {
476 assert!(from_end, "slice subslices should be `from_end`");
477 subslice.llextra = Some(bx.sub(
478 cg_base.llextra.unwrap(),
479 bx.cx().const_usize((*from as u64) + (*to as u64)),
483 // Cast the place pointer type to the new
484 // array or slice type (`*[%_; new_len]`).
485 subslice.llval = bx.pointercast(
487 bx.cx().type_ptr_to(bx.cx().backend_type(subslice.layout)),
492 mir::ProjectionElem::Downcast(_, v) => cg_base.project_downcast(bx, *v),
496 debug!("codegen_place(place={:?}) => {:?}", place_ref, result);
500 pub fn monomorphized_place_ty(&self, place_ref: &mir::PlaceRef<'_, 'tcx>) -> Ty<'tcx> {
501 let tcx = self.cx.tcx();
502 let place_ty = mir::Place::ty_from(place_ref.local, place_ref.projection, *self.mir, tcx);
503 self.monomorphize(&place_ty.ty)