1 use crate::abi::{FnType, FnTypeExt};
3 use crate::type_::Type;
5 use rustc::ty::{self, Ty, TypeFoldable};
6 use rustc::ty::layout::{self, Align, LayoutOf, Size, TyLayout};
7 use rustc_target::abi::FloatTy;
8 use rustc_mir::monomorphize::item::DefPathBasedNames;
9 use rustc_codegen_ssa::traits::*;
13 fn uncached_llvm_type<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
14 layout: TyLayout<'tcx>,
15 defer: &mut Option<(&'a Type, TyLayout<'tcx>)>)
18 layout::Abi::Scalar(_) => bug!("handled elsewhere"),
19 layout::Abi::Vector { ref element, count } => {
20 // LLVM has a separate type for 64-bit SIMD vectors on X86 called
21 // `x86_mmx` which is needed for some SIMD operations. As a bit of a
22 // hack (all SIMD definitions are super unstable anyway) we
23 // recognize any one-element SIMD vector as "this should be an
24 // x86_mmx" type. In general there shouldn't be a need for other
25 // one-element SIMD vectors, so it's assumed this won't clash with
27 let use_x86_mmx = count == 1 && layout.size.bits() == 64 &&
28 (cx.sess().target.target.arch == "x86" ||
29 cx.sess().target.target.arch == "x86_64");
31 return cx.type_x86_mmx()
33 let element = layout.scalar_llvm_type_at(cx, element, Size::ZERO);
34 return cx.type_vector(element, count);
37 layout::Abi::ScalarPair(..) => {
38 return cx.type_struct( &[
39 layout.scalar_pair_element_llvm_type(cx, 0, false),
40 layout.scalar_pair_element_llvm_type(cx, 1, false),
43 layout::Abi::Uninhabited |
44 layout::Abi::Aggregate { .. } => {}
47 let name = match layout.ty.sty {
51 // FIXME(eddyb) producing readable type names for trait objects can result
52 // in problematically distinct types due to HRTB and subtyping (see #47638).
56 let mut name = String::with_capacity(32);
57 let printer = DefPathBasedNames::new(cx.tcx, true, true);
58 printer.push_type_name(layout.ty, &mut name, false);
59 if let (&ty::Adt(def, _), &layout::Variants::Single { index })
60 = (&layout.ty.sty, &layout.variants)
62 if def.is_enum() && !def.variants.is_empty() {
63 write!(&mut name, "::{}", def.variants[index].ident).unwrap();
72 layout::FieldPlacement::Union(_) => {
73 let fill = cx.type_padding_filler(layout.size, layout.align.abi);
77 cx.type_struct(&[fill], packed)
80 let llty = cx.type_named_struct(name);
81 cx.set_struct_body(llty, &[fill], packed);
86 layout::FieldPlacement::Array { count, .. } => {
87 cx.type_array(layout.field(cx, 0).llvm_type(cx), count)
89 layout::FieldPlacement::Arbitrary { .. } => {
92 let (llfields, packed) = struct_llfields(cx, layout);
93 cx.type_struct( &llfields, packed)
96 let llty = cx.type_named_struct( name);
97 *defer = Some((llty, layout));
105 fn struct_llfields<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
106 layout: TyLayout<'tcx>)
107 -> (Vec<&'a Type>, bool) {
108 debug!("struct_llfields: {:#?}", layout);
109 let field_count = layout.fields.count();
111 let mut packed = false;
112 let mut offset = Size::ZERO;
113 let mut prev_effective_align = layout.align.abi;
114 let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2);
115 for i in layout.fields.index_by_increasing_offset() {
116 let target_offset = layout.fields.offset(i as usize);
117 let field = layout.field(cx, i);
118 let effective_field_align = layout.align.abi
119 .min(field.align.abi)
120 .restrict_for_offset(target_offset);
121 packed |= effective_field_align < field.align.abi;
123 debug!("struct_llfields: {}: {:?} offset: {:?} target_offset: {:?} \
124 effective_field_align: {}",
125 i, field, offset, target_offset, effective_field_align.bytes());
126 assert!(target_offset >= offset);
127 let padding = target_offset - offset;
128 let padding_align = prev_effective_align.min(effective_field_align);
129 assert_eq!(offset.align_to(padding_align) + padding, target_offset);
130 result.push(cx.type_padding_filler( padding, padding_align));
131 debug!(" padding before: {:?}", padding);
133 result.push(field.llvm_type(cx));
134 offset = target_offset + field.size;
135 prev_effective_align = effective_field_align;
137 if !layout.is_unsized() && field_count > 0 {
138 if offset > layout.size {
139 bug!("layout: {:#?} stride: {:?} offset: {:?}",
140 layout, layout.size, offset);
142 let padding = layout.size - offset;
143 let padding_align = prev_effective_align;
144 assert_eq!(offset.align_to(padding_align) + padding, layout.size);
145 debug!("struct_llfields: pad_bytes: {:?} offset: {:?} stride: {:?}",
146 padding, offset, layout.size);
147 result.push(cx.type_padding_filler(padding, padding_align));
148 assert_eq!(result.len(), 1 + field_count * 2);
150 debug!("struct_llfields: offset: {:?} stride: {:?}",
151 offset, layout.size);
157 impl<'a, 'tcx> CodegenCx<'a, 'tcx> {
158 pub fn align_of(&self, ty: Ty<'tcx>) -> Align {
159 self.layout_of(ty).align.abi
162 pub fn size_of(&self, ty: Ty<'tcx>) -> Size {
163 self.layout_of(ty).size
166 pub fn size_and_align_of(&self, ty: Ty<'tcx>) -> (Size, Align) {
167 let layout = self.layout_of(ty);
168 (layout.size, layout.align.abi)
172 #[derive(Copy, Clone, PartialEq, Eq)]
173 pub enum PointerKind {
174 /// Most general case, we know no restrictions to tell LLVM.
177 /// `&T` where `T` contains no `UnsafeCell`, is `noalias` and `readonly`.
180 /// `&mut T`, when we know `noalias` is safe for LLVM.
183 /// `Box<T>`, unlike `UniqueBorrowed`, it also has `noalias` on returns.
187 #[derive(Copy, Clone)]
188 pub struct PointeeInfo {
191 pub safe: Option<PointerKind>,
194 pub trait LayoutLlvmExt<'tcx> {
195 fn is_llvm_immediate(&self) -> bool;
196 fn is_llvm_scalar_pair<'a>(&self) -> bool;
197 fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
198 fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
199 fn scalar_llvm_type_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
200 scalar: &layout::Scalar, offset: Size) -> &'a Type;
201 fn scalar_pair_element_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
202 index: usize, immediate: bool) -> &'a Type;
203 fn llvm_field_index(&self, index: usize) -> u64;
204 fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size)
205 -> Option<PointeeInfo>;
208 impl<'tcx> LayoutLlvmExt<'tcx> for TyLayout<'tcx> {
209 fn is_llvm_immediate(&self) -> bool {
211 layout::Abi::Scalar(_) |
212 layout::Abi::Vector { .. } => true,
213 layout::Abi::ScalarPair(..) => false,
214 layout::Abi::Uninhabited |
215 layout::Abi::Aggregate { .. } => self.is_zst()
219 fn is_llvm_scalar_pair<'a>(&self) -> bool {
221 layout::Abi::ScalarPair(..) => true,
222 layout::Abi::Uninhabited |
223 layout::Abi::Scalar(_) |
224 layout::Abi::Vector { .. } |
225 layout::Abi::Aggregate { .. } => false
229 /// Gets the LLVM type corresponding to a Rust type, i.e., `rustc::ty::Ty`.
230 /// The pointee type of the pointer in `PlaceRef` is always this type.
231 /// For sized types, it is also the right LLVM type for an `alloca`
232 /// containing a value of that type, and most immediates (except `bool`).
233 /// Unsized types, however, are represented by a "minimal unit", e.g.
234 /// `[T]` becomes `T`, while `str` and `Trait` turn into `i8` - this
235 /// is useful for indexing slices, as `&[T]`'s data pointer is `T*`.
236 /// If the type is an unsized struct, the regular layout is generated,
237 /// with the inner-most trailing unsized field using the "minimal unit"
238 /// of that field's type - this is useful for taking the address of
239 /// that field and ensuring the struct has the right alignment.
240 fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
241 if let layout::Abi::Scalar(ref scalar) = self.abi {
242 // Use a different cache for scalars because pointers to DSTs
243 // can be either fat or thin (data pointers of fat pointers).
244 if let Some(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
247 let llty = match self.ty.sty {
249 ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
250 cx.type_ptr_to(cx.layout_of(ty).llvm_type(cx))
252 ty::Adt(def, _) if def.is_box() => {
253 cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).llvm_type(cx))
256 let sig = cx.tcx.normalize_erasing_late_bound_regions(
257 ty::ParamEnv::reveal_all(),
260 cx.fn_ptr_backend_type(&FnType::new(cx, sig, &[]))
262 _ => self.scalar_llvm_type_at(cx, scalar, Size::ZERO)
264 cx.scalar_lltypes.borrow_mut().insert(self.ty, llty);
270 let variant_index = match self.variants {
271 layout::Variants::Single { index } => Some(index),
274 if let Some(&llty) = cx.lltypes.borrow().get(&(self.ty, variant_index)) {
278 debug!("llvm_type({:#?})", self);
280 assert!(!self.ty.has_escaping_bound_vars(), "{:?} has escaping bound vars", self.ty);
282 // Make sure lifetimes are erased, to avoid generating distinct LLVM
283 // types for Rust types that only differ in the choice of lifetimes.
284 let normal_ty = cx.tcx.erase_regions(&self.ty);
286 let mut defer = None;
287 let llty = if self.ty != normal_ty {
288 let mut layout = cx.layout_of(normal_ty);
289 if let Some(v) = variant_index {
290 layout = layout.for_variant(cx, v);
294 uncached_llvm_type(cx, *self, &mut defer)
296 debug!("--> mapped {:#?} to llty={:?}", self, llty);
298 cx.lltypes.borrow_mut().insert((self.ty, variant_index), llty);
300 if let Some((llty, layout)) = defer {
301 let (llfields, packed) = struct_llfields(cx, layout);
302 cx.set_struct_body(llty, &llfields, packed)
308 fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
309 if let layout::Abi::Scalar(ref scalar) = self.abi {
310 if scalar.is_bool() {
317 fn scalar_llvm_type_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
318 scalar: &layout::Scalar, offset: Size) -> &'a Type {
320 layout::Int(i, _) => cx.type_from_integer( i),
321 layout::Float(FloatTy::F32) => cx.type_f32(),
322 layout::Float(FloatTy::F64) => cx.type_f64(),
324 // If we know the alignment, pick something better than i8.
325 let pointee = if let Some(pointee) = self.pointee_info_at(cx, offset) {
326 cx.type_pointee_for_align(pointee.align)
330 cx.type_ptr_to(pointee)
335 fn scalar_pair_element_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
336 index: usize, immediate: bool) -> &'a Type {
337 // HACK(eddyb) special-case fat pointers until LLVM removes
338 // pointee types, to avoid bitcasting every `OperandRef::deref`.
342 return self.field(cx, index).llvm_type(cx);
344 ty::Adt(def, _) if def.is_box() => {
345 let ptr_ty = cx.tcx.mk_mut_ptr(self.ty.boxed_ty());
346 return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
351 let (a, b) = match self.abi {
352 layout::Abi::ScalarPair(ref a, ref b) => (a, b),
353 _ => bug!("TyLayout::scalar_pair_element_llty({:?}): not applicable", self)
355 let scalar = [a, b][index];
357 // Make sure to return the same type `immediate_llvm_type` would when
358 // dealing with an immediate pair. This means that `(bool, bool)` is
359 // effectively represented as `{i8, i8}` in memory and two `i1`s as an
360 // immediate, just like `bool` is typically `i8` in memory and only `i1`
361 // when immediate. We need to load/store `bool` as `i8` to avoid
362 // crippling LLVM optimizations or triggering other LLVM bugs with `i1`.
363 if immediate && scalar.is_bool() {
367 let offset = if index == 0 {
370 a.value.size(cx).align_to(b.value.align(cx).abi)
372 self.scalar_llvm_type_at(cx, scalar, offset)
375 fn llvm_field_index(&self, index: usize) -> u64 {
377 layout::Abi::Scalar(_) |
378 layout::Abi::ScalarPair(..) => {
379 bug!("TyLayout::llvm_field_index({:?}): not applicable", self)
384 layout::FieldPlacement::Union(_) => {
385 bug!("TyLayout::llvm_field_index({:?}): not applicable", self)
388 layout::FieldPlacement::Array { .. } => {
392 layout::FieldPlacement::Arbitrary { .. } => {
393 1 + (self.fields.memory_index(index) as u64) * 2
398 fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size)
399 -> Option<PointeeInfo> {
400 if let Some(&pointee) = cx.pointee_infos.borrow().get(&(self.ty, offset)) {
404 let mut result = None;
406 ty::RawPtr(mt) if offset.bytes() == 0 => {
407 let (size, align) = cx.size_and_align_of(mt.ty);
408 result = Some(PointeeInfo {
415 ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
416 let (size, align) = cx.size_and_align_of(ty);
418 let kind = match mt {
419 hir::MutImmutable => if cx.type_is_freeze(ty) {
425 // Previously we would only emit noalias annotations for LLVM >= 6 or in
426 // panic=abort mode. That was deemed right, as prior versions had many bugs
427 // in conjunction with unwinding, but later versions didn’t seem to have
428 // said issues. See issue #31681.
430 // Alas, later on we encountered a case where noalias would generate wrong
431 // code altogether even with recent versions of LLVM in *safe* code with no
432 // unwinding involved. See #54462.
434 // For now, do not enable mutable_noalias by default at all, while the
435 // issue is being figured out.
436 let mutable_noalias = cx.tcx.sess.opts.debugging_opts.mutable_noalias
439 PointerKind::UniqueBorrowed
446 result = Some(PointeeInfo {
454 let mut data_variant = match self.variants {
455 layout::Variants::NicheFilling { dataful_variant, .. } => {
456 // Only the niche itself is always initialized,
457 // so only check for a pointer at its offset.
459 // If the niche is a pointer, it's either valid
460 // (according to its type), or null (which the
461 // niche field's scalar validity range encodes).
462 // This allows using `dereferenceable_or_null`
463 // for e.g., `Option<&T>`, and this will continue
464 // to work as long as we don't start using more
465 // niches than just null (e.g., the first page
466 // of the address space, or unaligned pointers).
467 if self.fields.offset(0) == offset {
468 Some(self.for_variant(cx, dataful_variant))
476 if let Some(variant) = data_variant {
477 // We're not interested in any unions.
478 if let layout::FieldPlacement::Union(_) = variant.fields {
483 if let Some(variant) = data_variant {
484 let ptr_end = offset + layout::Pointer.size(cx);
485 for i in 0..variant.fields.count() {
486 let field_start = variant.fields.offset(i);
487 if field_start <= offset {
488 let field = variant.field(cx, i);
489 if ptr_end <= field_start + field.size {
490 // We found the right field, look inside it.
491 result = field.pointee_info_at(cx, offset - field_start);
498 // FIXME(eddyb) This should be for `ptr::Unique<T>`, not `Box<T>`.
499 if let Some(ref mut pointee) = result {
500 if let ty::Adt(def, _) = self.ty.sty {
501 if def.is_box() && offset.bytes() == 0 {
502 pointee.safe = Some(PointerKind::UniqueOwned);
509 cx.pointee_infos.borrow_mut().insert((self.ty, offset), result);