compiler/rustc_codegen_cranelift/src/value_and_place.rs

   1 //! Definition of [`CValue`] and [`CPlace`]
   2
   3 use crate::prelude::*;
   4
   5 use cranelift_codegen::ir::immediates::Offset32;
   6
   7 fn codegen_field<'tcx>(
   8     fx: &mut FunctionCx<'_, '_, 'tcx>,
   9     base: Pointer,
  10     extra: Option<Value>,
  11     layout: TyAndLayout<'tcx>,
  12     field: mir::Field,
  13 ) -> (Pointer, TyAndLayout<'tcx>) {
  14     let field_offset = layout.fields.offset(field.index());
  15     let field_layout = layout.field(&*fx, field.index());
  16
  17     let simple = |fx: &mut FunctionCx<'_, '_, '_>| {
  18         (base.offset_i64(fx, i64::try_from(field_offset.bytes()).unwrap()), field_layout)
  19     };
  20
  21     if let Some(extra) = extra {
  22         if !field_layout.is_unsized() {
  23             return simple(fx);
  24         }
  25         match field_layout.ty.kind() {
  26             ty::Slice(..) | ty::Str | ty::Foreign(..) => simple(fx),
  27             ty::Adt(def, _) if def.repr.packed() => {
  28                 assert_eq!(layout.align.abi.bytes(), 1);
  29                 simple(fx)
  30             }
  31             _ => {
  32                 // We have to align the offset for DST's
  33                 let unaligned_offset = field_offset.bytes();
  34                 let (_, unsized_align) =
  35                     crate::unsize::size_and_align_of_dst(fx, field_layout, 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                 (base.offset_value(fx, offset), field_layout)
  45             }
  46         }
  47     } else {
  48         simple(fx)
  49     }
  50 }
  51
  52 fn scalar_pair_calculate_b_offset(
  53     tcx: TyCtxt<'_>,
  54     a_scalar: &Scalar,
  55     b_scalar: &Scalar,
  56 ) -> Offset32 {
  57     let b_offset = a_scalar.value.size(&tcx).align_to(b_scalar.value.align(&tcx).abi);
  58     Offset32::new(b_offset.bytes().try_into().unwrap())
  59 }
  60
  61 /// A read-only value
  62 #[derive(Debug, Copy, Clone)]
  63 pub(crate) struct CValue<'tcx>(CValueInner, TyAndLayout<'tcx>);
  64
  65 #[derive(Debug, Copy, Clone)]
  66 enum CValueInner {
  67     ByRef(Pointer, Option<Value>),
  68     ByVal(Value),
  69     ByValPair(Value, Value),
  70 }
  71
  72 impl<'tcx> CValue<'tcx> {
  73     pub(crate) fn by_ref(ptr: Pointer, layout: TyAndLayout<'tcx>) -> CValue<'tcx> {
  74         CValue(CValueInner::ByRef(ptr, None), layout)
  75     }
  76
  77     pub(crate) fn by_ref_unsized(
  78         ptr: Pointer,
  79         meta: Value,
  80         layout: TyAndLayout<'tcx>,
  81     ) -> CValue<'tcx> {
  82         CValue(CValueInner::ByRef(ptr, Some(meta)), layout)
  83     }
  84
  85     pub(crate) fn by_val(value: Value, layout: TyAndLayout<'tcx>) -> CValue<'tcx> {
  86         CValue(CValueInner::ByVal(value), layout)
  87     }
  88
  89     pub(crate) fn by_val_pair(
  90         value: Value,
  91         extra: Value,
  92         layout: TyAndLayout<'tcx>,
  93     ) -> CValue<'tcx> {
  94         CValue(CValueInner::ByValPair(value, extra), layout)
  95     }
  96
  97     pub(crate) fn layout(&self) -> TyAndLayout<'tcx> {
  98         self.1
  99     }
 100
 101     // FIXME remove
 102     pub(crate) fn force_stack(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> (Pointer, Option<Value>) {
 103         let layout = self.1;
 104         match self.0 {
 105             CValueInner::ByRef(ptr, meta) => (ptr, meta),
 106             CValueInner::ByVal(_) | CValueInner::ByValPair(_, _) => {
 107                 let cplace = CPlace::new_stack_slot(fx, layout);
 108                 cplace.write_cvalue(fx, self);
 109                 (cplace.to_ptr(), None)
 110             }
 111         }
 112     }
 113
 114     pub(crate) fn try_to_ptr(self) -> Option<(Pointer, Option<Value>)> {
 115         match self.0 {
 116             CValueInner::ByRef(ptr, meta) => Some((ptr, meta)),
 117             CValueInner::ByVal(_) | CValueInner::ByValPair(_, _) => None,
 118         }
 119     }
 120
 121     /// Load a value with layout.abi of scalar
 122     pub(crate) fn load_scalar(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> Value {
 123         let layout = self.1;
 124         match self.0 {
 125             CValueInner::ByRef(ptr, None) => {
 126                 let clif_ty = match layout.abi {
 127                     Abi::Scalar(ref scalar) => scalar_to_clif_type(fx.tcx, scalar.clone()),
 128                     Abi::Vector { ref element, count } => {
 129                         scalar_to_clif_type(fx.tcx, element.clone())
 130                             .by(u16::try_from(count).unwrap())
 131                             .unwrap()
 132                     }
 133                     _ => unreachable!("{:?}", layout.ty),
 134                 };
 135                 let mut flags = MemFlags::new();
 136                 flags.set_notrap();
 137                 ptr.load(fx, clif_ty, flags)
 138             }
 139             CValueInner::ByVal(value) => value,
 140             CValueInner::ByRef(_, Some(_)) => bug!("load_scalar for unsized value not allowed"),
 141             CValueInner::ByValPair(_, _) => bug!("Please use load_scalar_pair for ByValPair"),
 142         }
 143     }
 144
 145     /// Load a value pair with layout.abi of scalar pair
 146     pub(crate) fn load_scalar_pair(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> (Value, Value) {
 147         let layout = self.1;
 148         match self.0 {
 149             CValueInner::ByRef(ptr, None) => {
 150                 let (a_scalar, b_scalar) = match &layout.abi {
 151                     Abi::ScalarPair(a, b) => (a, b),
 152                     _ => unreachable!("load_scalar_pair({:?})", self),
 153                 };
 154                 let b_offset = scalar_pair_calculate_b_offset(fx.tcx, a_scalar, b_scalar);
 155                 let clif_ty1 = scalar_to_clif_type(fx.tcx, a_scalar.clone());
 156                 let clif_ty2 = scalar_to_clif_type(fx.tcx, b_scalar.clone());
 157                 let mut flags = MemFlags::new();
 158                 flags.set_notrap();
 159                 let val1 = ptr.load(fx, clif_ty1, flags);
 160                 let val2 = ptr.offset(fx, b_offset).load(fx, clif_ty2, flags);
 161                 (val1, val2)
 162             }
 163             CValueInner::ByRef(_, Some(_)) => {
 164                 bug!("load_scalar_pair for unsized value not allowed")
 165             }
 166             CValueInner::ByVal(_) => bug!("Please use load_scalar for ByVal"),
 167             CValueInner::ByValPair(val1, val2) => (val1, val2),
 168         }
 169     }
 170
 171     pub(crate) fn value_field(
 172         self,
 173         fx: &mut FunctionCx<'_, '_, 'tcx>,
 174         field: mir::Field,
 175     ) -> CValue<'tcx> {
 176         let layout = self.1;
 177         match self.0 {
 178             CValueInner::ByVal(val) => match layout.abi {
 179                 Abi::Vector { element: _, count } => {
 180                     let count = u8::try_from(count).expect("SIMD type with more than 255 lanes???");
 181                     let field = u8::try_from(field.index()).unwrap();
 182                     assert!(field < count);
 183                     let lane = fx.bcx.ins().extractlane(val, field);
 184                     let field_layout = layout.field(&*fx, usize::from(field));
 185                     CValue::by_val(lane, field_layout)
 186                 }
 187                 _ => unreachable!("value_field for ByVal with abi {:?}", layout.abi),
 188             },
 189             CValueInner::ByValPair(val1, val2) => match layout.abi {
 190                 Abi::ScalarPair(_, _) => {
 191                     let val = match field.as_u32() {
 192                         0 => val1,
 193                         1 => val2,
 194                         _ => bug!("field should be 0 or 1"),
 195                     };
 196                     let field_layout = layout.field(&*fx, usize::from(field));
 197                     CValue::by_val(val, field_layout)
 198                 }
 199                 _ => unreachable!("value_field for ByValPair with abi {:?}", layout.abi),
 200             },
 201             CValueInner::ByRef(ptr, None) => {
 202                 let (field_ptr, field_layout) = codegen_field(fx, ptr, None, layout, field);
 203                 CValue::by_ref(field_ptr, field_layout)
 204             }
 205             CValueInner::ByRef(_, Some(_)) => todo!(),
 206         }
 207     }
 208
 209     pub(crate) fn unsize_value(self, fx: &mut FunctionCx<'_, '_, 'tcx>, dest: CPlace<'tcx>) {
 210         crate::unsize::coerce_unsized_into(fx, self, dest);
 211     }
 212
 213     /// If `ty` is signed, `const_val` must already be sign extended.
 214     pub(crate) fn const_val(
 215         fx: &mut FunctionCx<'_, '_, 'tcx>,
 216         layout: TyAndLayout<'tcx>,
 217         const_val: ty::ScalarInt,
 218     ) -> CValue<'tcx> {
 219         assert_eq!(const_val.size(), layout.size, "{:#?}: {:?}", const_val, layout);
 220         use cranelift_codegen::ir::immediates::{Ieee32, Ieee64};
 221
 222         let clif_ty = fx.clif_type(layout.ty).unwrap();
 223
 224         if let ty::Bool = layout.ty.kind() {
 225             assert!(
 226                 const_val == ty::ScalarInt::FALSE || const_val == ty::ScalarInt::TRUE,
 227                 "Invalid bool 0x{:032X}",
 228                 const_val
 229             );
 230         }
 231
 232         let val = match layout.ty.kind() {
 233             ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
 234                 let const_val = const_val.to_bits(layout.size).unwrap();
 235                 let lsb = fx.bcx.ins().iconst(types::I64, const_val as u64 as i64);
 236                 let msb = fx.bcx.ins().iconst(types::I64, (const_val >> 64) as u64 as i64);
 237                 fx.bcx.ins().iconcat(lsb, msb)
 238             }
 239             ty::Bool | ty::Char | ty::Uint(_) | ty::Int(_) | ty::Ref(..) | ty::RawPtr(..) => {
 240                 fx.bcx.ins().iconst(clif_ty, const_val.to_bits(layout.size).unwrap() as i64)
 241             }
 242             ty::Float(FloatTy::F32) => {
 243                 fx.bcx.ins().f32const(Ieee32::with_bits(u32::try_from(const_val).unwrap()))
 244             }
 245             ty::Float(FloatTy::F64) => {
 246                 fx.bcx.ins().f64const(Ieee64::with_bits(u64::try_from(const_val).unwrap()))
 247             }
 248             _ => panic!(
 249                 "CValue::const_val for non bool/char/float/integer/pointer type {:?} is not allowed",
 250                 layout.ty
 251             ),
 252         };
 253
 254         CValue::by_val(val, layout)
 255     }
 256
 257     pub(crate) fn cast_pointer_to(self, layout: TyAndLayout<'tcx>) -> Self {
 258         assert!(matches!(self.layout().ty.kind(), ty::Ref(..) | ty::RawPtr(..) | ty::FnPtr(..)));
 259         assert!(matches!(layout.ty.kind(), ty::Ref(..) | ty::RawPtr(..) | ty::FnPtr(..)));
 260         assert_eq!(self.layout().abi, layout.abi);
 261         CValue(self.0, layout)
 262     }
 263 }
 264
 265 /// A place where you can write a value to or read a value from
 266 #[derive(Debug, Copy, Clone)]
 267 pub(crate) struct CPlace<'tcx> {
 268     inner: CPlaceInner,
 269     layout: TyAndLayout<'tcx>,
 270 }
 271
 272 #[derive(Debug, Copy, Clone)]
 273 pub(crate) enum CPlaceInner {
 274     Var(Local, Variable),
 275     VarPair(Local, Variable, Variable),
 276     VarLane(Local, Variable, u8),
 277     Addr(Pointer, Option<Value>),
 278 }
 279
 280 impl<'tcx> CPlace<'tcx> {
 281     pub(crate) fn layout(&self) -> TyAndLayout<'tcx> {
 282         self.layout
 283     }
 284
 285     pub(crate) fn inner(&self) -> &CPlaceInner {
 286         &self.inner
 287     }
 288
 289     pub(crate) fn no_place(layout: TyAndLayout<'tcx>) -> CPlace<'tcx> {
 290         CPlace { inner: CPlaceInner::Addr(Pointer::dangling(layout.align.pref), None), layout }
 291     }
 292
 293     pub(crate) fn new_stack_slot(
 294         fx: &mut FunctionCx<'_, '_, 'tcx>,
 295         layout: TyAndLayout<'tcx>,
 296     ) -> CPlace<'tcx> {
 297         assert!(!layout.is_unsized());
 298         if layout.size.bytes() == 0 {
 299             return CPlace::no_place(layout);
 300         }
 301
 302         let stack_slot = fx.bcx.create_stack_slot(StackSlotData {
 303             kind: StackSlotKind::ExplicitSlot,
 304             // FIXME Don't force the size to a multiple of 16 bytes once Cranelift gets a way to
 305             // specify stack slot alignment.
 306             size: (u32::try_from(layout.size.bytes()).unwrap() + 15) / 16 * 16,
 307             offset: None,
 308         });
 309         CPlace { inner: CPlaceInner::Addr(Pointer::stack_slot(stack_slot), None), layout }
 310     }
 311
 312     pub(crate) fn new_var(
 313         fx: &mut FunctionCx<'_, '_, 'tcx>,
 314         local: Local,
 315         layout: TyAndLayout<'tcx>,
 316     ) -> CPlace<'tcx> {
 317         let var = Variable::with_u32(fx.next_ssa_var);
 318         fx.next_ssa_var += 1;
 319         fx.bcx.declare_var(var, fx.clif_type(layout.ty).unwrap());
 320         CPlace { inner: CPlaceInner::Var(local, var), layout }
 321     }
 322
 323     pub(crate) fn new_var_pair(
 324         fx: &mut FunctionCx<'_, '_, 'tcx>,
 325         local: Local,
 326         layout: TyAndLayout<'tcx>,
 327     ) -> CPlace<'tcx> {
 328         let var1 = Variable::with_u32(fx.next_ssa_var);
 329         fx.next_ssa_var += 1;
 330         let var2 = Variable::with_u32(fx.next_ssa_var);
 331         fx.next_ssa_var += 1;
 332
 333         let (ty1, ty2) = fx.clif_pair_type(layout.ty).unwrap();
 334         fx.bcx.declare_var(var1, ty1);
 335         fx.bcx.declare_var(var2, ty2);
 336         CPlace { inner: CPlaceInner::VarPair(local, var1, var2), layout }
 337     }
 338
 339     pub(crate) fn for_ptr(ptr: Pointer, layout: TyAndLayout<'tcx>) -> CPlace<'tcx> {
 340         CPlace { inner: CPlaceInner::Addr(ptr, None), layout }
 341     }
 342
 343     pub(crate) fn for_ptr_with_extra(
 344         ptr: Pointer,
 345         extra: Value,
 346         layout: TyAndLayout<'tcx>,
 347     ) -> CPlace<'tcx> {
 348         CPlace { inner: CPlaceInner::Addr(ptr, Some(extra)), layout }
 349     }
 350
 351     pub(crate) fn to_cvalue(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> CValue<'tcx> {
 352         let layout = self.layout();
 353         match self.inner {
 354             CPlaceInner::Var(_local, var) => {
 355                 let val = fx.bcx.use_var(var);
 356                 //fx.bcx.set_val_label(val, cranelift_codegen::ir::ValueLabel::new(var.index()));
 357                 CValue::by_val(val, layout)
 358             }
 359             CPlaceInner::VarPair(_local, var1, var2) => {
 360                 let val1 = fx.bcx.use_var(var1);
 361                 //fx.bcx.set_val_label(val1, cranelift_codegen::ir::ValueLabel::new(var1.index()));
 362                 let val2 = fx.bcx.use_var(var2);
 363                 //fx.bcx.set_val_label(val2, cranelift_codegen::ir::ValueLabel::new(var2.index()));
 364                 CValue::by_val_pair(val1, val2, layout)
 365             }
 366             CPlaceInner::VarLane(_local, var, lane) => {
 367                 let val = fx.bcx.use_var(var);
 368                 //fx.bcx.set_val_label(val, cranelift_codegen::ir::ValueLabel::new(var.index()));
 369                 let val = fx.bcx.ins().extractlane(val, lane);
 370                 CValue::by_val(val, layout)
 371             }
 372             CPlaceInner::Addr(ptr, extra) => {
 373                 if let Some(extra) = extra {
 374                     CValue::by_ref_unsized(ptr, extra, layout)
 375                 } else {
 376                     CValue::by_ref(ptr, layout)
 377                 }
 378             }
 379         }
 380     }
 381
 382     pub(crate) fn to_ptr(self) -> Pointer {
 383         match self.to_ptr_maybe_unsized() {
 384             (ptr, None) => ptr,
 385             (_, Some(_)) => bug!("Expected sized cplace, found {:?}", self),
 386         }
 387     }
 388
 389     pub(crate) fn to_ptr_maybe_unsized(self) -> (Pointer, Option<Value>) {
 390         match self.inner {
 391             CPlaceInner::Addr(ptr, extra) => (ptr, extra),
 392             CPlaceInner::Var(_, _)
 393             | CPlaceInner::VarPair(_, _, _)
 394             | CPlaceInner::VarLane(_, _, _) => bug!("Expected CPlace::Addr, found {:?}", self),
 395         }
 396     }
 397
 398     pub(crate) fn write_cvalue(self, fx: &mut FunctionCx<'_, '_, 'tcx>, from: CValue<'tcx>) {
 399         assert_assignable(fx, from.layout().ty, self.layout().ty);
 400
 401         self.write_cvalue_maybe_transmute(fx, from, "write_cvalue");
 402     }
 403
 404     pub(crate) fn write_cvalue_transmute(
 405         self,
 406         fx: &mut FunctionCx<'_, '_, 'tcx>,
 407         from: CValue<'tcx>,
 408     ) {
 409         self.write_cvalue_maybe_transmute(fx, from, "write_cvalue_transmute");
 410     }
 411
 412     fn write_cvalue_maybe_transmute(
 413         self,
 414         fx: &mut FunctionCx<'_, '_, 'tcx>,
 415         from: CValue<'tcx>,
 416         method: &'static str,
 417     ) {
 418         fn transmute_value<'tcx>(
 419             fx: &mut FunctionCx<'_, '_, 'tcx>,
 420             var: Variable,
 421             data: Value,
 422             dst_ty: Type,
 423         ) {
 424             let src_ty = fx.bcx.func.dfg.value_type(data);
 425             assert_eq!(
 426                 src_ty.bytes(),
 427                 dst_ty.bytes(),
 428                 "write_cvalue_transmute: {:?} -> {:?}",
 429                 src_ty,
 430                 dst_ty,
 431             );
 432             let data = match (src_ty, dst_ty) {
 433                 (_, _) if src_ty == dst_ty => data,
 434
 435                 // This is a `write_cvalue_transmute`.
 436                 (types::I32, types::F32)
 437                 | (types::F32, types::I32)
 438                 | (types::I64, types::F64)
 439                 | (types::F64, types::I64) => fx.bcx.ins().bitcast(dst_ty, data),
 440                 _ if src_ty.is_vector() && dst_ty.is_vector() => {
 441                     fx.bcx.ins().raw_bitcast(dst_ty, data)
 442                 }
 443                 _ if src_ty.is_vector() || dst_ty.is_vector() => {
 444                     // FIXME do something more efficient for transmutes between vectors and integers.
 445                     let stack_slot = fx.bcx.create_stack_slot(StackSlotData {
 446                         kind: StackSlotKind::ExplicitSlot,
 447                         // FIXME Don't force the size to a multiple of 16 bytes once Cranelift gets a way to
 448                         // specify stack slot alignment.
 449                         size: (src_ty.bytes() + 15) / 16 * 16,
 450                         offset: None,
 451                     });
 452                     let ptr = Pointer::stack_slot(stack_slot);
 453                     ptr.store(fx, data, MemFlags::trusted());
 454                     ptr.load(fx, dst_ty, MemFlags::trusted())
 455                 }
 456
 457                 // `CValue`s should never contain SSA-only types, so if you ended
 458                 // up here having seen an error like `B1 -> I8`, then before
 459                 // calling `write_cvalue` you need to add a `bint` instruction.
 460                 _ => unreachable!("write_cvalue_transmute: {:?} -> {:?}", src_ty, dst_ty),
 461             };
 462             //fx.bcx.set_val_label(data, cranelift_codegen::ir::ValueLabel::new(var.index()));
 463             fx.bcx.def_var(var, data);
 464         }
 465
 466         assert_eq!(self.layout().size, from.layout().size);
 467
 468         if fx.clif_comments.enabled() {
 469             use cranelift_codegen::cursor::{Cursor, CursorPosition};
 470             let cur_block = match fx.bcx.cursor().position() {
 471                 CursorPosition::After(block) => block,
 472                 _ => unreachable!(),
 473             };
 474             fx.add_comment(
 475                 fx.bcx.func.layout.last_inst(cur_block).unwrap(),
 476                 format!(
 477                     "{}: {:?}: {:?} <- {:?}: {:?}",
 478                     method,
 479                     self.inner(),
 480                     self.layout().ty,
 481                     from.0,
 482                     from.layout().ty
 483                 ),
 484             );
 485         }
 486
 487         let dst_layout = self.layout();
 488         let to_ptr = match self.inner {
 489             CPlaceInner::Var(_local, var) => {
 490                 let data = CValue(from.0, dst_layout).load_scalar(fx);
 491                 let dst_ty = fx.clif_type(self.layout().ty).unwrap();
 492                 transmute_value(fx, var, data, dst_ty);
 493                 return;
 494             }
 495             CPlaceInner::VarPair(_local, var1, var2) => {
 496                 let (data1, data2) = CValue(from.0, dst_layout).load_scalar_pair(fx);
 497                 let (dst_ty1, dst_ty2) = fx.clif_pair_type(self.layout().ty).unwrap();
 498                 transmute_value(fx, var1, data1, dst_ty1);
 499                 transmute_value(fx, var2, data2, dst_ty2);
 500                 return;
 501             }
 502             CPlaceInner::VarLane(_local, var, lane) => {
 503                 let data = from.load_scalar(fx);
 504
 505                 // First get the old vector
 506                 let vector = fx.bcx.use_var(var);
 507                 //fx.bcx.set_val_label(vector, cranelift_codegen::ir::ValueLabel::new(var.index()));
 508
 509                 // Next insert the written lane into the vector
 510                 let vector = fx.bcx.ins().insertlane(vector, data, lane);
 511
 512                 // Finally write the new vector
 513                 //fx.bcx.set_val_label(vector, cranelift_codegen::ir::ValueLabel::new(var.index()));
 514                 fx.bcx.def_var(var, vector);
 515
 516                 return;
 517             }
 518             CPlaceInner::Addr(ptr, None) => {
 519                 if dst_layout.size == Size::ZERO || dst_layout.abi == Abi::Uninhabited {
 520                     return;
 521                 }
 522                 ptr
 523             }
 524             CPlaceInner::Addr(_, Some(_)) => bug!("Can't write value to unsized place {:?}", self),
 525         };
 526
 527         let mut flags = MemFlags::new();
 528         flags.set_notrap();
 529         match from.layout().abi {
 530             // FIXME make Abi::Vector work too
 531             Abi::Scalar(_) => {
 532                 let val = from.load_scalar(fx);
 533                 to_ptr.store(fx, val, flags);
 534                 return;
 535             }
 536             Abi::ScalarPair(ref a_scalar, ref b_scalar) => {
 537                 let (value, extra) = from.load_scalar_pair(fx);
 538                 let b_offset = scalar_pair_calculate_b_offset(fx.tcx, a_scalar, b_scalar);
 539                 to_ptr.store(fx, value, flags);
 540                 to_ptr.offset(fx, b_offset).store(fx, extra, flags);
 541                 return;
 542             }
 543             _ => {}
 544         }
 545
 546         match from.0 {
 547             CValueInner::ByVal(val) => {
 548                 to_ptr.store(fx, val, flags);
 549             }
 550             CValueInner::ByValPair(_, _) => {
 551                 bug!("Non ScalarPair abi {:?} for ByValPair CValue", dst_layout.abi);
 552             }
 553             CValueInner::ByRef(from_ptr, None) => {
 554                 let from_addr = from_ptr.get_addr(fx);
 555                 let to_addr = to_ptr.get_addr(fx);
 556                 let src_layout = from.1;
 557                 let size = dst_layout.size.bytes();
 558                 let src_align = src_layout.align.abi.bytes() as u8;
 559                 let dst_align = dst_layout.align.abi.bytes() as u8;
 560                 fx.bcx.emit_small_memory_copy(
 561                     fx.module.target_config(),
 562                     to_addr,
 563                     from_addr,
 564                     size,
 565                     dst_align,
 566                     src_align,
 567                     true,
 568                     MemFlags::trusted(),
 569                 );
 570             }
 571             CValueInner::ByRef(_, Some(_)) => todo!(),
 572         }
 573     }
 574
 575     pub(crate) fn place_field(
 576         self,
 577         fx: &mut FunctionCx<'_, '_, 'tcx>,
 578         field: mir::Field,
 579     ) -> CPlace<'tcx> {
 580         let layout = self.layout();
 581
 582         match self.inner {
 583             CPlaceInner::Var(local, var) => {
 584                 if let Abi::Vector { .. } = layout.abi {
 585                     return CPlace {
 586                         inner: CPlaceInner::VarLane(local, var, field.as_u32().try_into().unwrap()),
 587                         layout: layout.field(fx, field.as_u32().try_into().unwrap()),
 588                     };
 589                 }
 590             }
 591             CPlaceInner::VarPair(local, var1, var2) => {
 592                 let layout = layout.field(&*fx, field.index());
 593
 594                 match field.as_u32() {
 595                     0 => return CPlace { inner: CPlaceInner::Var(local, var1), layout },
 596                     1 => return CPlace { inner: CPlaceInner::Var(local, var2), layout },
 597                     _ => unreachable!("field should be 0 or 1"),
 598                 }
 599             }
 600             _ => {}
 601         }
 602
 603         let (base, extra) = self.to_ptr_maybe_unsized();
 604
 605         let (field_ptr, field_layout) = codegen_field(fx, base, extra, layout, field);
 606         if field_layout.is_unsized() {
 607             CPlace::for_ptr_with_extra(field_ptr, extra.unwrap(), field_layout)
 608         } else {
 609             CPlace::for_ptr(field_ptr, field_layout)
 610         }
 611     }
 612
 613     pub(crate) fn place_index(
 614         self,
 615         fx: &mut FunctionCx<'_, '_, 'tcx>,
 616         index: Value,
 617     ) -> CPlace<'tcx> {
 618         let (elem_layout, ptr) = match self.layout().ty.kind() {
 619             ty::Array(elem_ty, _) => (fx.layout_of(elem_ty), self.to_ptr()),
 620             ty::Slice(elem_ty) => (fx.layout_of(elem_ty), self.to_ptr_maybe_unsized().0),
 621             _ => bug!("place_index({:?})", self.layout().ty),
 622         };
 623
 624         let offset = fx.bcx.ins().imul_imm(index, elem_layout.size.bytes() as i64);
 625
 626         CPlace::for_ptr(ptr.offset_value(fx, offset), elem_layout)
 627     }
 628
 629     pub(crate) fn place_deref(self, fx: &mut FunctionCx<'_, '_, 'tcx>) -> CPlace<'tcx> {
 630         let inner_layout = fx.layout_of(self.layout().ty.builtin_deref(true).unwrap().ty);
 631         if has_ptr_meta(fx.tcx, inner_layout.ty) {
 632             let (addr, extra) = self.to_cvalue(fx).load_scalar_pair(fx);
 633             CPlace::for_ptr_with_extra(Pointer::new(addr), extra, inner_layout)
 634         } else {
 635             CPlace::for_ptr(Pointer::new(self.to_cvalue(fx).load_scalar(fx)), inner_layout)
 636         }
 637     }
 638
 639     pub(crate) fn place_ref(
 640         self,
 641         fx: &mut FunctionCx<'_, '_, 'tcx>,
 642         layout: TyAndLayout<'tcx>,
 643     ) -> CValue<'tcx> {
 644         if has_ptr_meta(fx.tcx, self.layout().ty) {
 645             let (ptr, extra) = self.to_ptr_maybe_unsized();
 646             CValue::by_val_pair(
 647                 ptr.get_addr(fx),
 648                 extra.expect("unsized type without metadata"),
 649                 layout,
 650             )
 651         } else {
 652             CValue::by_val(self.to_ptr().get_addr(fx), layout)
 653         }
 654     }
 655
 656     pub(crate) fn downcast_variant(
 657         self,
 658         fx: &FunctionCx<'_, '_, 'tcx>,
 659         variant: VariantIdx,
 660     ) -> Self {
 661         assert!(!self.layout().is_unsized());
 662         let layout = self.layout().for_variant(fx, variant);
 663         CPlace { inner: self.inner, layout }
 664     }
 665 }
 666
 667 #[track_caller]
 668 pub(crate) fn assert_assignable<'tcx>(
 669     fx: &FunctionCx<'_, '_, 'tcx>,
 670     from_ty: Ty<'tcx>,
 671     to_ty: Ty<'tcx>,
 672 ) {
 673     match (from_ty.kind(), to_ty.kind()) {
 674         (ty::Ref(_, a, _), ty::Ref(_, b, _))
 675         | (
 676             ty::RawPtr(TypeAndMut { ty: a, mutbl: _ }),
 677             ty::RawPtr(TypeAndMut { ty: b, mutbl: _ }),
 678         ) => {
 679             assert_assignable(fx, a, b);
 680         }
 681         (ty::Ref(_, a, _), ty::RawPtr(TypeAndMut { ty: b, mutbl: _ }))
 682         | (ty::RawPtr(TypeAndMut { ty: a, mutbl: _ }), ty::Ref(_, b, _)) => {
 683             assert_assignable(fx, a, b);
 684         }
 685         (ty::FnPtr(_), ty::FnPtr(_)) => {
 686             let from_sig = fx.tcx.normalize_erasing_late_bound_regions(
 687                 ParamEnv::reveal_all(),
 688                 from_ty.fn_sig(fx.tcx),
 689             );
 690             let to_sig = fx
 691                 .tcx
 692                 .normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to_ty.fn_sig(fx.tcx));
 693             assert_eq!(
 694                 from_sig, to_sig,
 695                 "Can't write fn ptr with incompatible sig {:?} to place with sig {:?}\n\n{:#?}",
 696                 from_sig, to_sig, fx,
 697             );
 698             // fn(&T) -> for<'l> fn(&'l T) is allowed
 699         }
 700         (&ty::Dynamic(from_traits, _), &ty::Dynamic(to_traits, _)) => {
 701             for (from, to) in from_traits.iter().zip(to_traits) {
 702                 let from =
 703                     fx.tcx.normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), from);
 704                 let to = fx.tcx.normalize_erasing_late_bound_regions(ParamEnv::reveal_all(), to);
 705                 assert_eq!(
 706                     from, to,
 707                     "Can't write trait object of incompatible traits {:?} to place with traits {:?}\n\n{:#?}",
 708                     from_traits, to_traits, fx,
 709                 );
 710             }
 711             // dyn for<'r> Trait<'r> -> dyn Trait<'_> is allowed
 712         }
 713         (&ty::Adt(adt_def_a, substs_a), &ty::Adt(adt_def_b, substs_b))
 714             if adt_def_a.did == adt_def_b.did =>
 715         {
 716             let mut types_a = substs_a.types();
 717             let mut types_b = substs_b.types();
 718             loop {
 719                 match (types_a.next(), types_b.next()) {
 720                     (Some(a), Some(b)) => assert_assignable(fx, a, b),
 721                     (None, None) => return,
 722                     (Some(_), None) | (None, Some(_)) => panic!("{:#?}/{:#?}", from_ty, to_ty),
 723                 }
 724             }
 725         }
 726         _ => {
 727             assert_eq!(
 728                 from_ty, to_ty,
 729                 "Can't write value with incompatible type {:?} to place with type {:?}\n\n{:#?}",
 730                 from_ty, to_ty, fx,
 731             );
 732         }
 733     }
 734 }