1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use abi::{FnType, FnTypeExt};
14 use rustc::ty::{self, Ty, TypeFoldable};
15 use rustc::ty::layout::{self, Align, LayoutOf, Size, TyLayout};
16 use rustc_target::abi::FloatTy;
17 use rustc_mir::monomorphize::item::DefPathBasedNames;
19 use interfaces::TypeMethods;
23 fn uncached_llvm_type<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
24 layout: TyLayout<'tcx>,
25 defer: &mut Option<(&'a Type, TyLayout<'tcx>)>)
28 layout::Abi::Scalar(_) => bug!("handled elsewhere"),
29 layout::Abi::Vector { ref element, count } => {
30 // LLVM has a separate type for 64-bit SIMD vectors on X86 called
31 // `x86_mmx` which is needed for some SIMD operations. As a bit of a
32 // hack (all SIMD definitions are super unstable anyway) we
33 // recognize any one-element SIMD vector as "this should be an
34 // x86_mmx" type. In general there shouldn't be a need for other
35 // one-element SIMD vectors, so it's assumed this won't clash with
37 let use_x86_mmx = count == 1 && layout.size.bits() == 64 &&
38 (cx.sess().target.target.arch == "x86" ||
39 cx.sess().target.target.arch == "x86_64");
41 return cx.type_x86_mmx()
43 let element = layout.scalar_llvm_type_at(cx, element, Size::ZERO);
44 return cx.type_vector(element, count);
47 layout::Abi::ScalarPair(..) => {
48 return cx.type_struct( &[
49 layout.scalar_pair_element_llvm_type(cx, 0, false),
50 layout.scalar_pair_element_llvm_type(cx, 1, false),
53 layout::Abi::Uninhabited |
54 layout::Abi::Aggregate { .. } => {}
57 let name = match layout.ty.sty {
61 // FIXME(eddyb) producing readable type names for trait objects can result
62 // in problematically distinct types due to HRTB and subtyping (see #47638).
66 let mut name = String::with_capacity(32);
67 let printer = DefPathBasedNames::new(cx.tcx, true, true);
68 printer.push_type_name(layout.ty, &mut name);
69 if let (&ty::Adt(def, _), &layout::Variants::Single { index })
70 = (&layout.ty.sty, &layout.variants)
72 if def.is_enum() && !def.variants.is_empty() {
73 write!(&mut name, "::{}", def.variants[index].name).unwrap();
82 layout::FieldPlacement::Union(_) => {
83 let fill = cx.type_padding_filler( layout.size, layout.align);
87 cx.type_struct( &[fill], packed)
90 let llty = cx.type_named_struct( name);
91 cx.set_struct_body(llty, &[fill], packed);
96 layout::FieldPlacement::Array { count, .. } => {
97 cx.type_array(layout.field(cx, 0).llvm_type(cx), count)
99 layout::FieldPlacement::Arbitrary { .. } => {
102 let (llfields, packed) = struct_llfields(cx, layout);
103 cx.type_struct( &llfields, packed)
106 let llty = cx.type_named_struct( name);
107 *defer = Some((llty, layout));
115 fn struct_llfields<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
116 layout: TyLayout<'tcx>)
117 -> (Vec<&'a Type>, bool) {
118 debug!("struct_llfields: {:#?}", layout);
119 let field_count = layout.fields.count();
121 let mut packed = false;
122 let mut offset = Size::ZERO;
123 let mut prev_effective_align = layout.align;
124 let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2);
125 for i in layout.fields.index_by_increasing_offset() {
126 let target_offset = layout.fields.offset(i as usize);
127 let field = layout.field(cx, i);
128 let effective_field_align = layout.align
130 .restrict_for_offset(target_offset);
131 packed |= effective_field_align.abi() < field.align.abi();
133 debug!("struct_llfields: {}: {:?} offset: {:?} target_offset: {:?} \
134 effective_field_align: {}",
135 i, field, offset, target_offset, effective_field_align.abi());
136 assert!(target_offset >= offset);
137 let padding = target_offset - offset;
138 let padding_align = prev_effective_align.min(effective_field_align);
139 assert_eq!(offset.abi_align(padding_align) + padding, target_offset);
140 result.push(cx.type_padding_filler( padding, padding_align));
141 debug!(" padding before: {:?}", padding);
143 result.push(field.llvm_type(cx));
144 offset = target_offset + field.size;
145 prev_effective_align = effective_field_align;
147 if !layout.is_unsized() && field_count > 0 {
148 if offset > layout.size {
149 bug!("layout: {:#?} stride: {:?} offset: {:?}",
150 layout, layout.size, offset);
152 let padding = layout.size - offset;
153 let padding_align = prev_effective_align;
154 assert_eq!(offset.abi_align(padding_align) + padding, layout.size);
155 debug!("struct_llfields: pad_bytes: {:?} offset: {:?} stride: {:?}",
156 padding, offset, layout.size);
157 result.push(cx.type_padding_filler(padding, padding_align));
158 assert_eq!(result.len(), 1 + field_count * 2);
160 debug!("struct_llfields: offset: {:?} stride: {:?}",
161 offset, layout.size);
167 impl<'a, 'tcx> CodegenCx<'a, 'tcx> {
168 pub fn align_of(&self, ty: Ty<'tcx>) -> Align {
169 self.layout_of(ty).align
172 pub fn size_of(&self, ty: Ty<'tcx>) -> Size {
173 self.layout_of(ty).size
176 pub fn size_and_align_of(&self, ty: Ty<'tcx>) -> (Size, Align) {
177 self.layout_of(ty).size_and_align()
181 #[derive(Copy, Clone, PartialEq, Eq)]
182 pub enum PointerKind {
183 /// Most general case, we know no restrictions to tell LLVM.
186 /// `&T` where `T` contains no `UnsafeCell`, is `noalias` and `readonly`.
189 /// `&mut T`, when we know `noalias` is safe for LLVM.
192 /// `Box<T>`, unlike `UniqueBorrowed`, it also has `noalias` on returns.
196 #[derive(Copy, Clone)]
197 pub struct PointeeInfo {
200 pub safe: Option<PointerKind>,
203 pub trait LayoutLlvmExt<'tcx> {
204 fn is_llvm_immediate(&self) -> bool;
205 fn is_llvm_scalar_pair<'a>(&self) -> bool;
206 fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
207 fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
208 fn scalar_llvm_type_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
209 scalar: &layout::Scalar, offset: Size) -> &'a Type;
210 fn scalar_pair_element_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
211 index: usize, immediate: bool) -> &'a Type;
212 fn llvm_field_index(&self, index: usize) -> u64;
213 fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size)
214 -> Option<PointeeInfo>;
217 impl<'tcx> LayoutLlvmExt<'tcx> for TyLayout<'tcx> {
218 fn is_llvm_immediate(&self) -> bool {
220 layout::Abi::Scalar(_) |
221 layout::Abi::Vector { .. } => true,
222 layout::Abi::ScalarPair(..) => false,
223 layout::Abi::Uninhabited |
224 layout::Abi::Aggregate { .. } => self.is_zst()
228 fn is_llvm_scalar_pair<'a>(&self) -> bool {
230 layout::Abi::ScalarPair(..) => true,
231 layout::Abi::Uninhabited |
232 layout::Abi::Scalar(_) |
233 layout::Abi::Vector { .. } |
234 layout::Abi::Aggregate { .. } => false
238 /// Get the LLVM type corresponding to a Rust type, i.e. `rustc::ty::Ty`.
239 /// The pointee type of the pointer in `PlaceRef` is always this type.
240 /// For sized types, it is also the right LLVM type for an `alloca`
241 /// containing a value of that type, and most immediates (except `bool`).
242 /// Unsized types, however, are represented by a "minimal unit", e.g.
243 /// `[T]` becomes `T`, while `str` and `Trait` turn into `i8` - this
244 /// is useful for indexing slices, as `&[T]`'s data pointer is `T*`.
245 /// If the type is an unsized struct, the regular layout is generated,
246 /// with the inner-most trailing unsized field using the "minimal unit"
247 /// of that field's type - this is useful for taking the address of
248 /// that field and ensuring the struct has the right alignment.
249 fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
250 if let layout::Abi::Scalar(ref scalar) = self.abi {
251 // Use a different cache for scalars because pointers to DSTs
252 // can be either fat or thin (data pointers of fat pointers).
253 if let Some(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
256 let llty = match self.ty.sty {
258 ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
259 cx.type_ptr_to(cx.layout_of(ty).llvm_type(cx))
261 ty::Adt(def, _) if def.is_box() => {
262 cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).llvm_type(cx))
265 let sig = cx.tcx.normalize_erasing_late_bound_regions(
266 ty::ParamEnv::reveal_all(),
269 FnType::new(cx, sig, &[]).ptr_to_llvm_type(cx)
271 _ => self.scalar_llvm_type_at(cx, scalar, Size::ZERO)
273 cx.scalar_lltypes.borrow_mut().insert(self.ty, llty);
279 let variant_index = match self.variants {
280 layout::Variants::Single { index } => Some(index),
283 if let Some(&llty) = cx.lltypes.borrow().get(&(self.ty, variant_index)) {
287 debug!("llvm_type({:#?})", self);
289 assert!(!self.ty.has_escaping_bound_vars(), "{:?} has escaping bound vars", self.ty);
291 // Make sure lifetimes are erased, to avoid generating distinct LLVM
292 // types for Rust types that only differ in the choice of lifetimes.
293 let normal_ty = cx.tcx.erase_regions(&self.ty);
295 let mut defer = None;
296 let llty = if self.ty != normal_ty {
297 let mut layout = cx.layout_of(normal_ty);
298 if let Some(v) = variant_index {
299 layout = layout.for_variant(cx, v);
303 uncached_llvm_type(cx, *self, &mut defer)
305 debug!("--> mapped {:#?} to llty={:?}", self, llty);
307 cx.lltypes.borrow_mut().insert((self.ty, variant_index), llty);
309 if let Some((llty, layout)) = defer {
310 let (llfields, packed) = struct_llfields(cx, layout);
311 cx.set_struct_body(llty, &llfields, packed)
317 fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
318 if let layout::Abi::Scalar(ref scalar) = self.abi {
319 if scalar.is_bool() {
326 fn scalar_llvm_type_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
327 scalar: &layout::Scalar, offset: Size) -> &'a Type {
329 layout::Int(i, _) => cx.type_from_integer( i),
330 layout::Float(FloatTy::F32) => cx.type_f32(),
331 layout::Float(FloatTy::F64) => cx.type_f64(),
333 // If we know the alignment, pick something better than i8.
334 let pointee = if let Some(pointee) = self.pointee_info_at(cx, offset) {
335 cx.type_pointee_for_abi_align( pointee.align)
339 cx.type_ptr_to(pointee)
344 fn scalar_pair_element_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>,
345 index: usize, immediate: bool) -> &'a Type {
346 // HACK(eddyb) special-case fat pointers until LLVM removes
347 // pointee types, to avoid bitcasting every `OperandRef::deref`.
351 return self.field(cx, index).llvm_type(cx);
353 ty::Adt(def, _) if def.is_box() => {
354 let ptr_ty = cx.tcx.mk_mut_ptr(self.ty.boxed_ty());
355 return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
360 let (a, b) = match self.abi {
361 layout::Abi::ScalarPair(ref a, ref b) => (a, b),
362 _ => bug!("TyLayout::scalar_pair_element_llty({:?}): not applicable", self)
364 let scalar = [a, b][index];
366 // Make sure to return the same type `immediate_llvm_type` would when
367 // dealing with an immediate pair. This means that `(bool, bool)` is
368 // effectively represented as `{i8, i8}` in memory and two `i1`s as an
369 // immediate, just like `bool` is typically `i8` in memory and only `i1`
370 // when immediate. We need to load/store `bool` as `i8` to avoid
371 // crippling LLVM optimizations or triggering other LLVM bugs with `i1`.
372 if immediate && scalar.is_bool() {
376 let offset = if index == 0 {
379 a.value.size(cx).abi_align(b.value.align(cx))
381 self.scalar_llvm_type_at(cx, scalar, offset)
384 fn llvm_field_index(&self, index: usize) -> u64 {
386 layout::Abi::Scalar(_) |
387 layout::Abi::ScalarPair(..) => {
388 bug!("TyLayout::llvm_field_index({:?}): not applicable", self)
393 layout::FieldPlacement::Union(_) => {
394 bug!("TyLayout::llvm_field_index({:?}): not applicable", self)
397 layout::FieldPlacement::Array { .. } => {
401 layout::FieldPlacement::Arbitrary { .. } => {
402 1 + (self.fields.memory_index(index) as u64) * 2
407 fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size)
408 -> Option<PointeeInfo> {
409 if let Some(&pointee) = cx.pointee_infos.borrow().get(&(self.ty, offset)) {
413 let mut result = None;
415 ty::RawPtr(mt) if offset.bytes() == 0 => {
416 let (size, align) = cx.size_and_align_of(mt.ty);
417 result = Some(PointeeInfo {
424 ty::Ref(_, ty, mt) if offset.bytes() == 0 => {
425 let (size, align) = cx.size_and_align_of(ty);
427 let kind = match mt {
428 hir::MutImmutable => if cx.type_is_freeze(ty) {
434 // Previously we would only emit noalias annotations for LLVM >= 6 or in
435 // panic=abort mode. That was deemed right, as prior versions had many bugs
436 // in conjunction with unwinding, but later versions didn’t seem to have
437 // said issues. See issue #31681.
439 // Alas, later on we encountered a case where noalias would generate wrong
440 // code altogether even with recent versions of LLVM in *safe* code with no
441 // unwinding involved. See #54462.
443 // For now, do not enable mutable_noalias by default at all, while the
444 // issue is being figured out.
445 let mutable_noalias = cx.tcx.sess.opts.debugging_opts.mutable_noalias
448 PointerKind::UniqueBorrowed
455 result = Some(PointeeInfo {
463 let mut data_variant = match self.variants {
464 layout::Variants::NicheFilling { dataful_variant, .. } => {
465 // Only the niche itself is always initialized,
466 // so only check for a pointer at its offset.
468 // If the niche is a pointer, it's either valid
469 // (according to its type), or null (which the
470 // niche field's scalar validity range encodes).
471 // This allows using `dereferenceable_or_null`
472 // for e.g. `Option<&T>`, and this will continue
473 // to work as long as we don't start using more
474 // niches than just null (e.g. the first page
475 // of the address space, or unaligned pointers).
476 if self.fields.offset(0) == offset {
477 Some(self.for_variant(cx, dataful_variant))
485 if let Some(variant) = data_variant {
486 // We're not interested in any unions.
487 if let layout::FieldPlacement::Union(_) = variant.fields {
492 if let Some(variant) = data_variant {
493 let ptr_end = offset + layout::Pointer.size(cx);
494 for i in 0..variant.fields.count() {
495 let field_start = variant.fields.offset(i);
496 if field_start <= offset {
497 let field = variant.field(cx, i);
498 if ptr_end <= field_start + field.size {
499 // We found the right field, look inside it.
500 result = field.pointee_info_at(cx, offset - field_start);
507 // FIXME(eddyb) This should be for `ptr::Unique<T>`, not `Box<T>`.
508 if let Some(ref mut pointee) = result {
509 if let ty::Adt(def, _) = self.ty.sty {
510 if def.is_box() && offset.bytes() == 0 {
511 pointee.safe = Some(PointerKind::UniqueOwned);
518 cx.pointee_infos.borrow_mut().insert((self.ty, offset), result);