src/value_and_place.rs

   1 use crate::prelude::*;
   2
   3 use cranelift_codegen::ir::immediates::Offset32;
   4
   5 fn codegen_field<'tcx>(
   6     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
   7     base: Pointer,
   8     extra: Option<Value>,
   9     layout: TyLayout<'tcx>,
  10     field: mir::Field,
  11 ) -> (Pointer, TyLayout<'tcx>) {
  12     let field_offset = layout.fields.offset(field.index());
  13     let field_layout = layout.field(&*fx, field.index());
  14
  15     let simple = |fx: &mut FunctionCx<_>| {
  16         (
  17             base.offset_i64(fx, i64::try_from(field_offset.bytes()).unwrap()),
  18             field_layout,
  19         )
  20     };
  21
  22     if let Some(extra) = extra {
  23         if !field_layout.is_unsized() {
  24             return simple(fx);
  25         }
  26         match field_layout.ty.kind {
  27             ty::Slice(..) | ty::Str | ty::Foreign(..) => return simple(fx),
  28             ty::Adt(def, _) if def.repr.packed() => {
  29                 assert_eq!(layout.align.abi.bytes(), 1);
  30                 return simple(fx);
  31             }
  32             _ => {
  33                 // We have to align the offset for DST's
  34                 let unaligned_offset = field_offset.bytes();
  35                 let (_, unsized_align) = crate::unsize::size_and_align_of_dst(fx, field_layout.ty, extra);
  36
  37                 let one = fx.bcx.ins().iconst(pointer_ty(fx.tcx), 1);
  38                 let align_sub_1 = fx.bcx.ins().isub(unsized_align, one);
  39                 let and_lhs = fx.bcx.ins().iadd_imm(align_sub_1, unaligned_offset as i64);
  40                 let zero = fx.bcx.ins().iconst(pointer_ty(fx.tcx), 0);
  41                 let and_rhs = fx.bcx.ins().isub(zero, unsized_align);
  42                 let offset = fx.bcx.ins().band(and_lhs, and_rhs);
  43
  44                 (
  45                     base.offset_value(fx, offset),
  46                     field_layout,
  47                 )
  48             }
  49         }
  50     } else {
  51         simple(fx)
  52     }
  53 }
  54
  55 fn scalar_pair_calculate_b_offset(tcx: TyCtxt<'_>, a_scalar: &Scalar, b_scalar: &Scalar) -> Offset32 {
  56     let b_offset = a_scalar
  57         .value
  58         .size(&tcx)
  59         .align_to(b_scalar.value.align(&tcx).abi);
  60     Offset32::new(b_offset.bytes().try_into().unwrap())
  61 }
  62
  63 /// A read-only value
  64 #[derive(Debug, Copy, Clone)]
  65 pub struct CValue<'tcx>(CValueInner, TyLayout<'tcx>);
  66
  67 #[derive(Debug, Copy, Clone)]
  68 enum CValueInner {
  69     ByRef(Pointer),
  70     ByVal(Value),
  71     ByValPair(Value, Value),
  72 }
  73
  74 impl<'tcx> CValue<'tcx> {
  75     pub fn by_ref(ptr: Pointer, layout: TyLayout<'tcx>) -> CValue<'tcx> {
  76         CValue(CValueInner::ByRef(ptr), layout)
  77     }
  78
  79     pub fn by_val(value: Value, layout: TyLayout<'tcx>) -> CValue<'tcx> {
  80         CValue(CValueInner::ByVal(value), layout)
  81     }
  82
  83     pub fn by_val_pair(value: Value, extra: Value, layout: TyLayout<'tcx>) -> CValue<'tcx> {
  84         CValue(CValueInner::ByValPair(value, extra), layout)
  85     }
  86
  87     pub fn layout(&self) -> TyLayout<'tcx> {
  88         self.1
  89     }
  90
  91     pub fn force_stack<'a>(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>) -> Pointer {
  92         let layout = self.1;
  93         match self.0 {
  94             CValueInner::ByRef(ptr) => ptr,
  95             CValueInner::ByVal(_) | CValueInner::ByValPair(_, _) => {
  96                 let cplace = CPlace::new_stack_slot(fx, layout.ty);
  97                 cplace.write_cvalue(fx, self);
  98                 cplace.to_ptr(fx)
  99             }
 100         }
 101     }
 102
 103     pub fn try_to_addr(self) -> Option<Value> {
 104         match self.0 {
 105             CValueInner::ByRef(ptr) => {
 106                 if let Some((base_addr, offset)) = ptr.try_get_addr_and_offset() {
 107                     if offset == Offset32::new(0) {
 108                         Some(base_addr)
 109                     } else {
 110                         None
 111                     }
 112                 } else {
 113                     None
 114                 }
 115             }
 116             CValueInner::ByVal(_) | CValueInner::ByValPair(_, _) => None,
 117         }
 118     }
 119
 120     /// Load a value with layout.abi of scalar
 121     pub fn load_scalar<'a>(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>) -> Value {
 122         let layout = self.1;
 123         match self.0 {
 124             CValueInner::ByRef(ptr) => {
 125                 let clif_ty = match layout.abi {
 126                     layout::Abi::Scalar(ref scalar) => scalar_to_clif_type(fx.tcx, scalar.clone()),
 127                     layout::Abi::Vector { ref element, count } => {
 128                         scalar_to_clif_type(fx.tcx, element.clone())
 129                             .by(u16::try_from(count).unwrap()).unwrap()
 130                     }
 131                     _ => unreachable!(),
 132                 };
 133                 ptr.load(fx, clif_ty, MemFlags::new())
 134             }
 135             CValueInner::ByVal(value) => value,
 136             CValueInner::ByValPair(_, _) => bug!("Please use load_scalar_pair for ByValPair"),
 137         }
 138     }
 139
 140     /// Load a value pair with layout.abi of scalar pair
 141     pub fn load_scalar_pair<'a>(
 142         self,
 143         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 144     ) -> (Value, Value) {
 145         let layout = self.1;
 146         match self.0 {
 147             CValueInner::ByRef(ptr) => {
 148                 let (a_scalar, b_scalar) = match &layout.abi {
 149                     layout::Abi::ScalarPair(a, b) => (a, b),
 150                     _ => unreachable!("load_scalar_pair({:?})", self),
 151                 };
 152                 let b_offset = scalar_pair_calculate_b_offset(fx.tcx, a_scalar, b_scalar);
 153                 let clif_ty1 = scalar_to_clif_type(fx.tcx, a_scalar.clone());
 154                 let clif_ty2 = scalar_to_clif_type(fx.tcx, b_scalar.clone());
 155                 let val1 = ptr.load(fx, clif_ty1, MemFlags::new());
 156                 let val2 = ptr.offset(fx, b_offset).load(fx, clif_ty2, MemFlags::new());
 157                 (val1, val2)
 158             }
 159             CValueInner::ByVal(_) => bug!("Please use load_scalar for ByVal"),
 160             CValueInner::ByValPair(val1, val2) => (val1, val2),
 161         }
 162     }
 163
 164     pub fn value_field<'a>(
 165         self,
 166         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 167         field: mir::Field,
 168     ) -> CValue<'tcx> {
 169         let layout = self.1;
 170         match self.0 {
 171             CValueInner::ByVal(val) => {
 172                 match layout.abi {
 173                     layout::Abi::Vector { element: _, count } => {
 174                         let count = u8::try_from(count).expect("SIMD type with more than 255 lanes???");
 175                         let field = u8::try_from(field.index()).unwrap();
 176                         assert!(field < count);
 177                         let lane = fx.bcx.ins().extractlane(val, field);
 178                         let field_layout = layout.field(&*fx, usize::from(field));
 179                         CValue::by_val(lane, field_layout)
 180                     }
 181                     _ => unreachable!("value_field for ByVal with abi {:?}", layout.abi),
 182                 }
 183             }
 184             CValueInner::ByRef(ptr) => {
 185                 let (field_ptr, field_layout) = codegen_field(fx, ptr, None, layout, field);
 186                 CValue::by_ref(field_ptr, field_layout)
 187             }
 188             _ => bug!("place_field for {:?}", self),
 189         }
 190     }
 191
 192     pub fn unsize_value<'a>(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>, dest: CPlace<'tcx>) {
 193         crate::unsize::coerce_unsized_into(fx, self, dest);
 194     }
 195
 196     /// If `ty` is signed, `const_val` must already be sign extended.
 197     pub fn const_val<'a>(
 198         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 199         ty: Ty<'tcx>,
 200         const_val: u128,
 201     ) -> CValue<'tcx> {
 202         let clif_ty = fx.clif_type(ty).unwrap();
 203         let layout = fx.layout_of(ty);
 204
 205         let val = match ty.kind {
 206             ty::TyKind::Uint(UintTy::U128) | ty::TyKind::Int(IntTy::I128) => {
 207                 let lsb = fx.bcx.ins().iconst(types::I64, const_val as u64 as i64);
 208                 let msb = fx
 209                     .bcx
 210                     .ins()
 211                     .iconst(types::I64, (const_val >> 64) as u64 as i64);
 212                 fx.bcx.ins().iconcat(lsb, msb)
 213             }
 214             ty::TyKind::Bool => {
 215                 assert!(
 216                     const_val == 0 || const_val == 1,
 217                     "Invalid bool 0x{:032X}",
 218                     const_val
 219                 );
 220                 fx.bcx.ins().iconst(types::I8, const_val as i64)
 221             }
 222             ty::TyKind::Uint(_) | ty::TyKind::Ref(..) | ty::TyKind::RawPtr(..) => fx
 223                 .bcx
 224                 .ins()
 225                 .iconst(clif_ty, u64::try_from(const_val).expect("uint") as i64),
 226             ty::TyKind::Int(_) => fx.bcx.ins().iconst(clif_ty, const_val as i128 as i64),
 227             _ => panic!(
 228                 "CValue::const_val for non bool/integer/pointer type {:?} is not allowed",
 229                 ty
 230             ),
 231         };
 232
 233         CValue::by_val(val, layout)
 234     }
 235
 236     pub fn unchecked_cast_to(self, layout: TyLayout<'tcx>) -> Self {
 237         CValue(self.0, layout)
 238     }
 239 }
 240
 241 /// A place where you can write a value to or read a value from
 242 #[derive(Debug, Copy, Clone)]
 243 pub struct CPlace<'tcx> {
 244     inner: CPlaceInner,
 245     layout: TyLayout<'tcx>,
 246 }
 247
 248 #[derive(Debug, Copy, Clone)]
 249 pub enum CPlaceInner {
 250     Var(Local),
 251     Addr(Pointer, Option<Value>),
 252     NoPlace,
 253 }
 254
 255 impl<'tcx> CPlace<'tcx> {
 256     pub fn layout(&self) -> TyLayout<'tcx> {
 257         self.layout
 258     }
 259
 260     pub fn inner(&self) -> &CPlaceInner {
 261         &self.inner
 262     }
 263
 264     pub fn no_place(layout: TyLayout<'tcx>) -> CPlace<'tcx> {
 265         CPlace {
 266             inner: CPlaceInner::NoPlace,
 267             layout,
 268         }
 269     }
 270
 271     pub fn new_stack_slot(
 272         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 273         ty: Ty<'tcx>,
 274     ) -> CPlace<'tcx> {
 275         let layout = fx.layout_of(ty);
 276         assert!(!layout.is_unsized());
 277         if layout.size.bytes() == 0 {
 278             return CPlace {
 279                 inner: CPlaceInner::NoPlace,
 280                 layout,
 281             };
 282         }
 283
 284         let stack_slot = fx.bcx.create_stack_slot(StackSlotData {
 285             kind: StackSlotKind::ExplicitSlot,
 286             size: layout.size.bytes() as u32,
 287             offset: None,
 288         });
 289         CPlace {
 290             inner: CPlaceInner::Addr(Pointer::stack_slot(stack_slot), None),
 291             layout,
 292         }
 293     }
 294
 295     pub fn new_var(
 296         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 297         local: Local,
 298         layout: TyLayout<'tcx>,
 299     ) -> CPlace<'tcx> {
 300         fx.bcx
 301             .declare_var(mir_var(local), fx.clif_type(layout.ty).unwrap());
 302         CPlace {
 303             inner: CPlaceInner::Var(local),
 304             layout,
 305         }
 306     }
 307
 308     pub fn for_ptr(ptr: Pointer, layout: TyLayout<'tcx>) -> CPlace<'tcx> {
 309         CPlace {
 310             inner: CPlaceInner::Addr(ptr, None),
 311             layout,
 312         }
 313     }
 314
 315     pub fn for_ptr_with_extra(ptr: Pointer, extra: Value, layout: TyLayout<'tcx>) -> CPlace<'tcx> {
 316         CPlace {
 317             inner: CPlaceInner::Addr(ptr, Some(extra)),
 318             layout,
 319         }
 320     }
 321
 322     pub fn to_cvalue(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>) -> CValue<'tcx> {
 323         let layout = self.layout();
 324         match self.inner {
 325             CPlaceInner::Var(var) => {
 326                 let val = fx.bcx.use_var(mir_var(var));
 327                 fx.bcx.set_val_label(val, cranelift_codegen::ir::ValueLabel::from_u32(var.as_u32()));
 328                 CValue::by_val(val, layout)
 329             }
 330             CPlaceInner::Addr(ptr, extra) => {
 331                 assert!(extra.is_none(), "unsized values are not yet supported");
 332                 CValue::by_ref(ptr, layout)
 333             }
 334             CPlaceInner::NoPlace => CValue::by_ref(
 335                 Pointer::const_addr(fx, i64::try_from(self.layout.align.pref.bytes()).unwrap()),
 336                 layout,
 337             ),
 338         }
 339     }
 340
 341     pub fn to_ptr(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>) -> Pointer {
 342         match self.to_ptr_maybe_unsized(fx) {
 343             (ptr, None) => ptr,
 344             (_, Some(_)) => bug!("Expected sized cplace, found {:?}", self),
 345         }
 346     }
 347
 348     pub fn to_ptr_maybe_unsized(
 349         self,
 350         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 351     ) -> (Pointer, Option<Value>) {
 352         match self.inner {
 353             CPlaceInner::Addr(ptr, extra) => (ptr, extra),
 354             CPlaceInner::NoPlace => {
 355                 (
 356                     Pointer::const_addr(fx, i64::try_from(self.layout.align.pref.bytes()).unwrap()),
 357                     None,
 358                 )
 359             }
 360             CPlaceInner::Var(_) => bug!("Expected CPlace::Addr, found CPlace::Var"),
 361         }
 362     }
 363
 364     pub fn write_cvalue(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>, from: CValue<'tcx>) {
 365         #[cfg(debug_assertions)]
 366         {
 367             use cranelift_codegen::cursor::{Cursor, CursorPosition};
 368             let cur_ebb = match fx.bcx.cursor().position() {
 369                 CursorPosition::After(ebb) => ebb,
 370                 _ => unreachable!(),
 371             };
 372             fx.add_comment(
 373                 fx.bcx.func.layout.last_inst(cur_ebb).unwrap(),
 374                 format!("write_cvalue: {:?} <- {:?}",self, from),
 375             );
 376         }
 377
 378         let from_ty = from.layout().ty;
 379         let to_ty = self.layout().ty;
 380
 381         fn assert_assignable<'tcx>(
 382             fx: &FunctionCx<'_, 'tcx, impl Backend>,
 383             from_ty: Ty<'tcx>,
 384             to_ty: Ty<'tcx>,
 385         ) {
 386             match (&from_ty.kind, &to_ty.kind) {
 387                 (ty::Ref(_, t, Mutability::Not), ty::Ref(_, u, Mutability::Not))
 388                 | (ty::Ref(_, t, Mutability::Mut), ty::Ref(_, u, Mutability::Not))
 389                 | (ty::Ref(_, t, Mutability::Mut), ty::Ref(_, u, Mutability::Mut)) => {
 390                     assert_assignable(fx, t, u);
 391                     // &mut T -> &T is allowed
 392                     // &'a T -> &'b T is allowed
 393                 }
 394                 (ty::Ref(_, _, Mutability::Not), ty::Ref(_, _, Mutability::Mut)) => panic!(
 395                     "Cant assign value of type {} to place of type {}",
 396                     from_ty, to_ty
 397                 ),
 398                 (ty::FnPtr(_), ty::FnPtr(_)) => {
 399                     let from_sig = fx.tcx.normalize_erasing_late_bound_regions(
 400                         ParamEnv::reveal_all(),
 401                         &from_ty.fn_sig(fx.tcx),
 402                     );
 403                     let to_sig = fx.tcx.normalize_erasing_late_bound_regions(
 404                         ParamEnv::reveal_all(),
 405                         &to_ty.fn_sig(fx.tcx),
 406                     );
 407                     assert_eq!(
 408                         from_sig, to_sig,
 409                         "Can't write fn ptr with incompatible sig {:?} to place with sig {:?}\n\n{:#?}",
 410                         from_sig, to_sig, fx,
 411                     );
 412                     // fn(&T) -> for<'l> fn(&'l T) is allowed
 413                 }
 414                 (ty::Dynamic(from_traits, _), ty::Dynamic(to_traits, _)) => {
 415                     let from_traits = fx
 416                         .tcx
 417                         .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from_traits);
 418                     let to_traits = fx
 419                         .tcx
 420                         .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to_traits);
 421                     assert_eq!(
 422                         from_traits, to_traits,
 423                         "Can't write trait object of incompatible traits {:?} to place with traits {:?}\n\n{:#?}",
 424                         from_traits, to_traits, fx,
 425                     );
 426                     // dyn for<'r> Trait<'r> -> dyn Trait<'_> is allowed
 427                 }
 428                 _ => {
 429                     assert_eq!(
 430                         from_ty,
 431                         to_ty,
 432                         "Can't write value with incompatible type {:?} to place with type {:?}\n\n{:#?}",
 433                         from_ty,
 434                         to_ty,
 435                         fx,
 436                     );
 437                 }
 438             }
 439         }
 440
 441         assert_assignable(fx, from_ty, to_ty);
 442
 443         let dst_layout = self.layout();
 444         let to_ptr = match self.inner {
 445             CPlaceInner::Var(var) => {
 446                 let data = from.load_scalar(fx);
 447                 fx.bcx.set_val_label(data, cranelift_codegen::ir::ValueLabel::from_u32(var.as_u32()));
 448                 fx.bcx.def_var(mir_var(var), data);
 449                 return;
 450             }
 451             CPlaceInner::Addr(ptr, None) => ptr,
 452             CPlaceInner::NoPlace => {
 453                 if dst_layout.abi != Abi::Uninhabited {
 454                     assert_eq!(dst_layout.size.bytes(), 0, "{:?}", dst_layout);
 455                 }
 456                 return;
 457             }
 458             CPlaceInner::Addr(_, Some(_)) => bug!("Can't write value to unsized place {:?}", self),
 459         };
 460
 461         match from.0 {
 462             CValueInner::ByVal(val) => {
 463                 to_ptr.store(fx, val, MemFlags::new());
 464             }
 465             CValueInner::ByValPair(value, extra) => match dst_layout.abi {
 466                 Abi::ScalarPair(ref a_scalar, ref b_scalar) => {
 467                     let b_offset = scalar_pair_calculate_b_offset(fx.tcx, a_scalar, b_scalar);
 468                     to_ptr.store(fx, value, MemFlags::new());
 469                     to_ptr.offset(fx, b_offset).store(fx, extra, MemFlags::new());
 470                 }
 471                 _ => bug!(
 472                     "Non ScalarPair abi {:?} for ByValPair CValue",
 473                     dst_layout.abi
 474                 ),
 475             },
 476             CValueInner::ByRef(from_ptr) => {
 477                 let from_addr = from_ptr.get_addr(fx);
 478                 let to_addr = to_ptr.get_addr(fx);
 479                 let src_layout = from.1;
 480                 let size = dst_layout.size.bytes();
 481                 let src_align = src_layout.align.abi.bytes() as u8;
 482                 let dst_align = dst_layout.align.abi.bytes() as u8;
 483                 fx.bcx.emit_small_memcpy(
 484                     fx.module.target_config(),
 485                     to_addr,
 486                     from_addr,
 487                     size,
 488                     dst_align,
 489                     src_align,
 490                 );
 491             }
 492         }
 493     }
 494
 495     pub fn place_field(
 496         self,
 497         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 498         field: mir::Field,
 499     ) -> CPlace<'tcx> {
 500         let layout = self.layout();
 501         let (base, extra) = self.to_ptr_maybe_unsized(fx);
 502
 503         let (field_ptr, field_layout) = codegen_field(fx, base, extra, layout, field);
 504         if field_layout.is_unsized() {
 505             CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
 506         } else {
 507             CPlace::for_ptr(field_ptr, field_layout)
 508         }
 509     }
 510
 511     pub fn place_index(
 512         self,
 513         fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 514         index: Value,
 515     ) -> CPlace<'tcx> {
 516         let (elem_layout, ptr) = match self.layout().ty.kind {
 517             ty::Array(elem_ty, _) => (fx.layout_of(elem_ty), self.to_ptr(fx)),
 518             ty::Slice(elem_ty) => (fx.layout_of(elem_ty), self.to_ptr_maybe_unsized(fx).0),
 519             _ => bug!("place_index({:?})", self.layout().ty),
 520         };
 521
 522         let offset = fx
 523             .bcx
 524             .ins()
 525             .imul_imm(index, elem_layout.size.bytes() as i64);
 526
 527         CPlace::for_ptr(ptr.offset_value(fx, offset), elem_layout)
 528     }
 529
 530     pub fn place_deref(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>) -> CPlace<'tcx> {
 531         let inner_layout = fx.layout_of(self.layout().ty.builtin_deref(true).unwrap().ty);
 532         if has_ptr_meta(fx.tcx, inner_layout.ty) {
 533             let (addr, extra) = self.to_cvalue(fx).load_scalar_pair(fx);
 534             CPlace::for_ptr_with_extra(Pointer::new(addr), extra, inner_layout)
 535         } else {
 536             CPlace::for_ptr(Pointer::new(self.to_cvalue(fx).load_scalar(fx)), inner_layout)
 537         }
 538     }
 539
 540     pub fn write_place_ref(self, fx: &mut FunctionCx<'_, 'tcx, impl Backend>, dest: CPlace<'tcx>) {
 541         if has_ptr_meta(fx.tcx, self.layout().ty) {
 542             let (ptr, extra) = self.to_ptr_maybe_unsized(fx);
 543             let ptr = CValue::by_val_pair(
 544                 ptr.get_addr(fx),
 545                 extra.expect("unsized type without metadata"),
 546                 dest.layout(),
 547             );
 548             dest.write_cvalue(fx, ptr);
 549         } else {
 550             let ptr = CValue::by_val(self.to_ptr(fx).get_addr(fx), dest.layout());
 551             dest.write_cvalue(fx, ptr);
 552         }
 553     }
 554
 555     pub fn unchecked_cast_to(self, layout: TyLayout<'tcx>) -> Self {
 556         assert!(!self.layout().is_unsized());
 557         match self.inner {
 558             CPlaceInner::NoPlace => {
 559                 assert!(layout.size.bytes() == 0);
 560             }
 561             _ => {}
 562         }
 563         CPlace {
 564             inner: self.inner,
 565             layout,
 566         }
 567     }
 568
 569     pub fn downcast_variant(
 570         self,
 571         fx: &FunctionCx<'_, 'tcx, impl Backend>,
 572         variant: VariantIdx,
 573     ) -> Self {
 574         let layout = self.layout().for_variant(fx, variant);
 575         self.unchecked_cast_to(layout)
 576     }
 577 }