src/librustc_codegen_llvm/type_of.rs

   1 use crate::abi::FnAbi;
   2 use crate::common::*;
   3 use crate::type_::Type;
   4 use rustc_codegen_ssa::traits::*;
   5 use rustc_middle::bug;
   6 use rustc_middle::ty::layout::{FnAbiExt, TyAndLayout};
   7 use rustc_middle::ty::print::obsolete::DefPathBasedNames;
   8 use rustc_middle::ty::{self, Ty, TypeFoldable};
   9 use rustc_target::abi::{Abi, AddressSpace, Align, FieldsShape};
  10 use rustc_target::abi::{Int, Pointer, F32, F64};
  11 use rustc_target::abi::{LayoutOf, PointeeInfo, Scalar, Size, TyAndLayoutMethods, Variants};
  12 use tracing::debug;
  13
  14 use std::fmt::Write;
  15
  16 fn uncached_llvm_type<'a, 'tcx>(
  17     cx: &CodegenCx<'a, 'tcx>,
  18     layout: TyAndLayout<'tcx>,
  19     defer: &mut Option<(&'a Type, TyAndLayout<'tcx>)>,
  20 ) -> &'a Type {
  21     match layout.abi {
  22         Abi::Scalar(_) => bug!("handled elsewhere"),
  23         Abi::Vector { ref element, count } => {
  24             // LLVM has a separate type for 64-bit SIMD vectors on X86 called
  25             // `x86_mmx` which is needed for some SIMD operations. As a bit of a
  26             // hack (all SIMD definitions are super unstable anyway) we
  27             // recognize any one-element SIMD vector as "this should be an
  28             // x86_mmx" type. In general there shouldn't be a need for other
  29             // one-element SIMD vectors, so it's assumed this won't clash with
  30             // much else.
  31             let use_x86_mmx = count == 1
  32                 && layout.size.bits() == 64
  33                 && (cx.sess().target.target.arch == "x86"
  34                     || cx.sess().target.target.arch == "x86_64");
  35             if use_x86_mmx {
  36                 return cx.type_x86_mmx();
  37             } else {
  38                 let element = layout.scalar_llvm_type_at(cx, element, Size::ZERO);
  39                 return cx.type_vector(element, count);
  40             }
  41         }
  42         Abi::ScalarPair(..) => {
  43             return cx.type_struct(
  44                 &[
  45                     layout.scalar_pair_element_llvm_type(cx, 0, false),
  46                     layout.scalar_pair_element_llvm_type(cx, 1, false),
  47                 ],
  48                 false,
  49             );
  50         }
  51         Abi::Uninhabited | Abi::Aggregate { .. } => {}
  52     }
  53
  54     let name = match layout.ty.kind {
  55         ty::Closure(..) |
  56         ty::Generator(..) |
  57         ty::Adt(..) |
  58         // FIXME(eddyb) producing readable type names for trait objects can result
  59         // in problematically distinct types due to HRTB and subtyping (see #47638).
  60         // ty::Dynamic(..) |
  61         ty::Foreign(..) |
  62         ty::Str => {
  63             let mut name = String::with_capacity(32);
  64             let printer = DefPathBasedNames::new(cx.tcx, true, true);
  65             printer.push_type_name(layout.ty, &mut name, false);
  66             if let (&ty::Adt(def, _), &Variants::Single { index })
  67                  = (&layout.ty.kind, &layout.variants)
  68             {
  69                 if def.is_enum() && !def.variants.is_empty() {
  70                     write!(&mut name, "::{}", def.variants[index].ident).unwrap();
  71                 }
  72             }
  73             if let (&ty::Generator(_, _, _), &Variants::Single { index })
  74                  = (&layout.ty.kind, &layout.variants)
  75             {
  76                 write!(&mut name, "::{}", ty::GeneratorSubsts::variant_name(index)).unwrap();
  77             }
  78             Some(name)
  79         }
  80         _ => None
  81     };
  82
  83     match layout.fields {
  84         FieldsShape::Primitive | FieldsShape::Union(_) => {
  85             let fill = cx.type_padding_filler(layout.size, layout.align.abi);
  86             let packed = false;
  87             match name {
  88                 None => cx.type_struct(&[fill], packed),
  89                 Some(ref name) => {
  90                     let llty = cx.type_named_struct(name);
  91                     cx.set_struct_body(llty, &[fill], packed);
  92                     llty
  93                 }
  94             }
  95         }
  96         FieldsShape::Array { count, .. } => cx.type_array(layout.field(cx, 0).llvm_type(cx), count),
  97         FieldsShape::Arbitrary { .. } => match name {
  98             None => {
  99                 let (llfields, packed) = struct_llfields(cx, layout);
 100                 cx.type_struct(&llfields, packed)
 101             }
 102             Some(ref name) => {
 103                 let llty = cx.type_named_struct(name);
 104                 *defer = Some((llty, layout));
 105                 llty
 106             }
 107         },
 108     }
 109 }
 110
 111 fn struct_llfields<'a, 'tcx>(
 112     cx: &CodegenCx<'a, 'tcx>,
 113     layout: TyAndLayout<'tcx>,
 114 ) -> (Vec<&'a Type>, bool) {
 115     debug!("struct_llfields: {:#?}", layout);
 116     let field_count = layout.fields.count();
 117
 118     let mut packed = false;
 119     let mut offset = Size::ZERO;
 120     let mut prev_effective_align = layout.align.abi;
 121     let mut result: Vec<_> = Vec::with_capacity(1 + field_count * 2);
 122     for i in layout.fields.index_by_increasing_offset() {
 123         let target_offset = layout.fields.offset(i as usize);
 124         let field = layout.field(cx, i);
 125         let effective_field_align =
 126             layout.align.abi.min(field.align.abi).restrict_for_offset(target_offset);
 127         packed |= effective_field_align < field.align.abi;
 128
 129         debug!(
 130             "struct_llfields: {}: {:?} offset: {:?} target_offset: {:?} \
 131                 effective_field_align: {}",
 132             i,
 133             field,
 134             offset,
 135             target_offset,
 136             effective_field_align.bytes()
 137         );
 138         assert!(target_offset >= offset);
 139         let padding = target_offset - offset;
 140         let padding_align = prev_effective_align.min(effective_field_align);
 141         assert_eq!(offset.align_to(padding_align) + padding, target_offset);
 142         result.push(cx.type_padding_filler(padding, padding_align));
 143         debug!("    padding before: {:?}", padding);
 144
 145         result.push(field.llvm_type(cx));
 146         offset = target_offset + field.size;
 147         prev_effective_align = effective_field_align;
 148     }
 149     if !layout.is_unsized() && field_count > 0 {
 150         if offset > layout.size {
 151             bug!("layout: {:#?} stride: {:?} offset: {:?}", layout, layout.size, offset);
 152         }
 153         let padding = layout.size - offset;
 154         let padding_align = prev_effective_align;
 155         assert_eq!(offset.align_to(padding_align) + padding, layout.size);
 156         debug!(
 157             "struct_llfields: pad_bytes: {:?} offset: {:?} stride: {:?}",
 158             padding, offset, layout.size
 159         );
 160         result.push(cx.type_padding_filler(padding, padding_align));
 161         assert_eq!(result.len(), 1 + field_count * 2);
 162     } else {
 163         debug!("struct_llfields: offset: {:?} stride: {:?}", offset, layout.size);
 164     }
 165
 166     (result, packed)
 167 }
 168
 169 impl<'a, 'tcx> CodegenCx<'a, 'tcx> {
 170     pub fn align_of(&self, ty: Ty<'tcx>) -> Align {
 171         self.layout_of(ty).align.abi
 172     }
 173
 174     pub fn size_of(&self, ty: Ty<'tcx>) -> Size {
 175         self.layout_of(ty).size
 176     }
 177
 178     pub fn size_and_align_of(&self, ty: Ty<'tcx>) -> (Size, Align) {
 179         let layout = self.layout_of(ty);
 180         (layout.size, layout.align.abi)
 181     }
 182 }
 183
 184 pub trait LayoutLlvmExt<'tcx> {
 185     fn is_llvm_immediate(&self) -> bool;
 186     fn is_llvm_scalar_pair(&self) -> bool;
 187     fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
 188     fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type;
 189     fn scalar_llvm_type_at<'a>(
 190         &self,
 191         cx: &CodegenCx<'a, 'tcx>,
 192         scalar: &Scalar,
 193         offset: Size,
 194     ) -> &'a Type;
 195     fn scalar_pair_element_llvm_type<'a>(
 196         &self,
 197         cx: &CodegenCx<'a, 'tcx>,
 198         index: usize,
 199         immediate: bool,
 200     ) -> &'a Type;
 201     fn llvm_field_index(&self, index: usize) -> u64;
 202     fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size) -> Option<PointeeInfo>;
 203 }
 204
 205 impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
 206     fn is_llvm_immediate(&self) -> bool {
 207         match self.abi {
 208             Abi::Scalar(_) | Abi::Vector { .. } => true,
 209             Abi::ScalarPair(..) => false,
 210             Abi::Uninhabited | Abi::Aggregate { .. } => self.is_zst(),
 211         }
 212     }
 213
 214     fn is_llvm_scalar_pair(&self) -> bool {
 215         match self.abi {
 216             Abi::ScalarPair(..) => true,
 217             Abi::Uninhabited | Abi::Scalar(_) | Abi::Vector { .. } | Abi::Aggregate { .. } => false,
 218         }
 219     }
 220
 221     /// Gets the LLVM type corresponding to a Rust type, i.e., `rustc_middle::ty::Ty`.
 222     /// The pointee type of the pointer in `PlaceRef` is always this type.
 223     /// For sized types, it is also the right LLVM type for an `alloca`
 224     /// containing a value of that type, and most immediates (except `bool`).
 225     /// Unsized types, however, are represented by a "minimal unit", e.g.
 226     /// `[T]` becomes `T`, while `str` and `Trait` turn into `i8` - this
 227     /// is useful for indexing slices, as `&[T]`'s data pointer is `T*`.
 228     /// If the type is an unsized struct, the regular layout is generated,
 229     /// with the inner-most trailing unsized field using the "minimal unit"
 230     /// of that field's type - this is useful for taking the address of
 231     /// that field and ensuring the struct has the right alignment.
 232     fn llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
 233         if let Abi::Scalar(ref scalar) = self.abi {
 234             // Use a different cache for scalars because pointers to DSTs
 235             // can be either fat or thin (data pointers of fat pointers).
 236             if let Some(&llty) = cx.scalar_lltypes.borrow().get(&self.ty) {
 237                 return llty;
 238             }
 239             let llty = match self.ty.kind {
 240                 ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
 241                     cx.type_ptr_to(cx.layout_of(ty).llvm_type(cx))
 242                 }
 243                 ty::Adt(def, _) if def.is_box() => {
 244                     cx.type_ptr_to(cx.layout_of(self.ty.boxed_ty()).llvm_type(cx))
 245                 }
 246                 ty::FnPtr(sig) => cx.fn_ptr_backend_type(&FnAbi::of_fn_ptr(cx, sig, &[])),
 247                 _ => self.scalar_llvm_type_at(cx, scalar, Size::ZERO),
 248             };
 249             cx.scalar_lltypes.borrow_mut().insert(self.ty, llty);
 250             return llty;
 251         }
 252
 253         // Check the cache.
 254         let variant_index = match self.variants {
 255             Variants::Single { index } => Some(index),
 256             _ => None,
 257         };
 258         if let Some(&llty) = cx.lltypes.borrow().get(&(self.ty, variant_index)) {
 259             return llty;
 260         }
 261
 262         debug!("llvm_type({:#?})", self);
 263
 264         assert!(!self.ty.has_escaping_bound_vars(), "{:?} has escaping bound vars", self.ty);
 265
 266         // Make sure lifetimes are erased, to avoid generating distinct LLVM
 267         // types for Rust types that only differ in the choice of lifetimes.
 268         let normal_ty = cx.tcx.erase_regions(&self.ty);
 269
 270         let mut defer = None;
 271         let llty = if self.ty != normal_ty {
 272             let mut layout = cx.layout_of(normal_ty);
 273             if let Some(v) = variant_index {
 274                 layout = layout.for_variant(cx, v);
 275             }
 276             layout.llvm_type(cx)
 277         } else {
 278             uncached_llvm_type(cx, *self, &mut defer)
 279         };
 280         debug!("--> mapped {:#?} to llty={:?}", self, llty);
 281
 282         cx.lltypes.borrow_mut().insert((self.ty, variant_index), llty);
 283
 284         if let Some((llty, layout)) = defer {
 285             let (llfields, packed) = struct_llfields(cx, layout);
 286             cx.set_struct_body(llty, &llfields, packed)
 287         }
 288
 289         llty
 290     }
 291
 292     fn immediate_llvm_type<'a>(&self, cx: &CodegenCx<'a, 'tcx>) -> &'a Type {
 293         if let Abi::Scalar(ref scalar) = self.abi {
 294             if scalar.is_bool() {
 295                 return cx.type_i1();
 296             }
 297         }
 298         self.llvm_type(cx)
 299     }
 300
 301     fn scalar_llvm_type_at<'a>(
 302         &self,
 303         cx: &CodegenCx<'a, 'tcx>,
 304         scalar: &Scalar,
 305         offset: Size,
 306     ) -> &'a Type {
 307         match scalar.value {
 308             Int(i, _) => cx.type_from_integer(i),
 309             F32 => cx.type_f32(),
 310             F64 => cx.type_f64(),
 311             Pointer => {
 312                 // If we know the alignment, pick something better than i8.
 313                 let (pointee, address_space) =
 314                     if let Some(pointee) = self.pointee_info_at(cx, offset) {
 315                         (cx.type_pointee_for_align(pointee.align), pointee.address_space)
 316                     } else {
 317                         (cx.type_i8(), AddressSpace::DATA)
 318                     };
 319                 cx.type_ptr_to_ext(pointee, address_space)
 320             }
 321         }
 322     }
 323
 324     fn scalar_pair_element_llvm_type<'a>(
 325         &self,
 326         cx: &CodegenCx<'a, 'tcx>,
 327         index: usize,
 328         immediate: bool,
 329     ) -> &'a Type {
 330         // HACK(eddyb) special-case fat pointers until LLVM removes
 331         // pointee types, to avoid bitcasting every `OperandRef::deref`.
 332         match self.ty.kind {
 333             ty::Ref(..) | ty::RawPtr(_) => {
 334                 return self.field(cx, index).llvm_type(cx);
 335             }
 336             ty::Adt(def, _) if def.is_box() => {
 337                 let ptr_ty = cx.tcx.mk_mut_ptr(self.ty.boxed_ty());
 338                 return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
 339             }
 340             _ => {}
 341         }
 342
 343         let (a, b) = match self.abi {
 344             Abi::ScalarPair(ref a, ref b) => (a, b),
 345             _ => bug!("TyAndLayout::scalar_pair_element_llty({:?}): not applicable", self),
 346         };
 347         let scalar = [a, b][index];
 348
 349         // Make sure to return the same type `immediate_llvm_type` would when
 350         // dealing with an immediate pair.  This means that `(bool, bool)` is
 351         // effectively represented as `{i8, i8}` in memory and two `i1`s as an
 352         // immediate, just like `bool` is typically `i8` in memory and only `i1`
 353         // when immediate.  We need to load/store `bool` as `i8` to avoid
 354         // crippling LLVM optimizations or triggering other LLVM bugs with `i1`.
 355         if immediate && scalar.is_bool() {
 356             return cx.type_i1();
 357         }
 358
 359         let offset =
 360             if index == 0 { Size::ZERO } else { a.value.size(cx).align_to(b.value.align(cx).abi) };
 361         self.scalar_llvm_type_at(cx, scalar, offset)
 362     }
 363
 364     fn llvm_field_index(&self, index: usize) -> u64 {
 365         match self.abi {
 366             Abi::Scalar(_) | Abi::ScalarPair(..) => {
 367                 bug!("TyAndLayout::llvm_field_index({:?}): not applicable", self)
 368             }
 369             _ => {}
 370         }
 371         match self.fields {
 372             FieldsShape::Primitive | FieldsShape::Union(_) => {
 373                 bug!("TyAndLayout::llvm_field_index({:?}): not applicable", self)
 374             }
 375
 376             FieldsShape::Array { .. } => index as u64,
 377
 378             FieldsShape::Arbitrary { .. } => 1 + (self.fields.memory_index(index) as u64) * 2,
 379         }
 380     }
 381
 382     fn pointee_info_at<'a>(&self, cx: &CodegenCx<'a, 'tcx>, offset: Size) -> Option<PointeeInfo> {
 383         if let Some(&pointee) = cx.pointee_infos.borrow().get(&(self.ty, offset)) {
 384             return pointee;
 385         }
 386
 387         let result = Ty::pointee_info_at(*self, cx, offset);
 388
 389         cx.pointee_infos.borrow_mut().insert((self.ty, offset), result);
 390         result
 391     }
 392 }