compiler/rustc_codegen_ssa/src/mir/rvalue.rs

   1 use super::operand::{OperandRef, OperandValue};
   2 use super::place::PlaceRef;
   3 use super::{FunctionCx, LocalRef};
   4
   5 use crate::base;
   6 use crate::common::{self, IntPredicate};
   7 use crate::traits::*;
   8 use crate::MemFlags;
   9
  10 use rustc_middle::mir;
  11 use rustc_middle::ty::cast::{CastTy, IntTy};
  12 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
  13 use rustc_middle::ty::{self, adjustment::PointerCast, Instance, Ty, TyCtxt};
  14 use rustc_span::source_map::{Span, DUMMY_SP};
  15 use rustc_target::abi::{Abi, Int, Variants};
  16
  17 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  18     pub fn codegen_rvalue(
  19         &mut self,
  20         mut bx: Bx,
  21         dest: PlaceRef<'tcx, Bx::Value>,
  22         rvalue: &mir::Rvalue<'tcx>,
  23     ) -> Bx {
  24         debug!("codegen_rvalue(dest.llval={:?}, rvalue={:?})", dest.llval, rvalue);
  25
  26         match *rvalue {
  27             mir::Rvalue::Use(ref operand) => {
  28                 let cg_operand = self.codegen_operand(&mut bx, operand);
  29                 // FIXME: consider not copying constants through stack. (Fixable by codegen'ing
  30                 // constants into `OperandValue::Ref`; why don’t we do that yet if we don’t?)
  31                 cg_operand.val.store(&mut bx, dest);
  32                 bx
  33             }
  34
  35             mir::Rvalue::Cast(mir::CastKind::Pointer(PointerCast::Unsize), ref source, _) => {
  36                 // The destination necessarily contains a fat pointer, so if
  37                 // it's a scalar pair, it's a fat pointer or newtype thereof.
  38                 if bx.cx().is_backend_scalar_pair(dest.layout) {
  39                     // Into-coerce of a thin pointer to a fat pointer -- just
  40                     // use the operand path.
  41                     let (mut bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
  42                     temp.val.store(&mut bx, dest);
  43                     return bx;
  44                 }
  45
  46                 // Unsize of a nontrivial struct. I would prefer for
  47                 // this to be eliminated by MIR building, but
  48                 // `CoerceUnsized` can be passed by a where-clause,
  49                 // so the (generic) MIR may not be able to expand it.
  50                 let operand = self.codegen_operand(&mut bx, source);
  51                 match operand.val {
  52                     OperandValue::Pair(..) | OperandValue::Immediate(_) => {
  53                         // Unsize from an immediate structure. We don't
  54                         // really need a temporary alloca here, but
  55                         // avoiding it would require us to have
  56                         // `coerce_unsized_into` use `extractvalue` to
  57                         // index into the struct, and this case isn't
  58                         // important enough for it.
  59                         debug!("codegen_rvalue: creating ugly alloca");
  60                         let scratch = PlaceRef::alloca(&mut bx, operand.layout);
  61                         scratch.storage_live(&mut bx);
  62                         operand.val.store(&mut bx, scratch);
  63                         base::coerce_unsized_into(&mut bx, scratch, dest);
  64                         scratch.storage_dead(&mut bx);
  65                     }
  66                     OperandValue::Ref(llref, None, align) => {
  67                         let source = PlaceRef::new_sized_aligned(llref, operand.layout, align);
  68                         base::coerce_unsized_into(&mut bx, source, dest);
  69                     }
  70                     OperandValue::Ref(_, Some(_), _) => {
  71                         bug!("unsized coercion on an unsized rvalue");
  72                     }
  73                 }
  74                 bx
  75             }
  76
  77             mir::Rvalue::Repeat(ref elem, count) => {
  78                 let cg_elem = self.codegen_operand(&mut bx, elem);
  79
  80                 // Do not generate the loop for zero-sized elements or empty arrays.
  81                 if dest.layout.is_zst() {
  82                     return bx;
  83                 }
  84
  85                 if let OperandValue::Immediate(v) = cg_elem.val {
  86                     let zero = bx.const_usize(0);
  87                     let start = dest.project_index(&mut bx, zero).llval;
  88                     let size = bx.const_usize(dest.layout.size.bytes());
  89
  90                     // Use llvm.memset.p0i8.* to initialize all zero arrays
  91                     if bx.cx().const_to_opt_uint(v) == Some(0) {
  92                         let fill = bx.cx().const_u8(0);
  93                         bx.memset(start, fill, size, dest.align, MemFlags::empty());
  94                         return bx;
  95                     }
  96
  97                     // Use llvm.memset.p0i8.* to initialize byte arrays
  98                     let v = bx.from_immediate(v);
  99                     if bx.cx().val_ty(v) == bx.cx().type_i8() {
 100                         bx.memset(start, v, size, dest.align, MemFlags::empty());
 101                         return bx;
 102                     }
 103                 }
 104
 105                 let count =
 106                     self.monomorphize(count).eval_usize(bx.cx().tcx(), ty::ParamEnv::reveal_all());
 107
 108                 bx.write_operand_repeatedly(cg_elem, count, dest)
 109             }
 110
 111             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 112                 let (dest, active_field_index) = match **kind {
 113                     mir::AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
 114                         dest.codegen_set_discr(&mut bx, variant_index);
 115                         if bx.tcx().adt_def(adt_did).is_enum() {
 116                             (dest.project_downcast(&mut bx, variant_index), active_field_index)
 117                         } else {
 118                             (dest, active_field_index)
 119                         }
 120                     }
 121                     _ => (dest, None),
 122                 };
 123                 for (i, operand) in operands.iter().enumerate() {
 124                     let op = self.codegen_operand(&mut bx, operand);
 125                     // Do not generate stores and GEPis for zero-sized fields.
 126                     if !op.layout.is_zst() {
 127                         let field_index = active_field_index.unwrap_or(i);
 128                         let field = dest.project_field(&mut bx, field_index);
 129                         op.val.store(&mut bx, field);
 130                     }
 131                 }
 132                 bx
 133             }
 134
 135             _ => {
 136                 assert!(self.rvalue_creates_operand(rvalue, DUMMY_SP));
 137                 let (mut bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
 138                 temp.val.store(&mut bx, dest);
 139                 bx
 140             }
 141         }
 142     }
 143
 144     pub fn codegen_rvalue_unsized(
 145         &mut self,
 146         mut bx: Bx,
 147         indirect_dest: PlaceRef<'tcx, Bx::Value>,
 148         rvalue: &mir::Rvalue<'tcx>,
 149     ) -> Bx {
 150         debug!(
 151             "codegen_rvalue_unsized(indirect_dest.llval={:?}, rvalue={:?})",
 152             indirect_dest.llval, rvalue
 153         );
 154
 155         match *rvalue {
 156             mir::Rvalue::Use(ref operand) => {
 157                 let cg_operand = self.codegen_operand(&mut bx, operand);
 158                 cg_operand.val.store_unsized(&mut bx, indirect_dest);
 159                 bx
 160             }
 161
 162             _ => bug!("unsized assignment other than `Rvalue::Use`"),
 163         }
 164     }
 165
 166     pub fn codegen_rvalue_operand(
 167         &mut self,
 168         mut bx: Bx,
 169         rvalue: &mir::Rvalue<'tcx>,
 170     ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
 171         assert!(
 172             self.rvalue_creates_operand(rvalue, DUMMY_SP),
 173             "cannot codegen {:?} to operand",
 174             rvalue,
 175         );
 176
 177         match *rvalue {
 178             mir::Rvalue::Cast(ref kind, ref source, mir_cast_ty) => {
 179                 let operand = self.codegen_operand(&mut bx, source);
 180                 debug!("cast operand is {:?}", operand);
 181                 let cast = bx.cx().layout_of(self.monomorphize(mir_cast_ty));
 182
 183                 let val = match *kind {
 184                     mir::CastKind::PointerExposeAddress => {
 185                         assert!(bx.cx().is_backend_immediate(cast));
 186                         let llptr = operand.immediate();
 187                         let llcast_ty = bx.cx().immediate_backend_type(cast);
 188                         let lladdr = bx.ptrtoint(llptr, llcast_ty);
 189                         OperandValue::Immediate(lladdr)
 190                     }
 191                     mir::CastKind::Pointer(PointerCast::ReifyFnPointer) => {
 192                         match *operand.layout.ty.kind() {
 193                             ty::FnDef(def_id, substs) => {
 194                                 let instance = ty::Instance::resolve_for_fn_ptr(
 195                                     bx.tcx(),
 196                                     ty::ParamEnv::reveal_all(),
 197                                     def_id,
 198                                     substs,
 199                                 )
 200                                 .unwrap()
 201                                 .polymorphize(bx.cx().tcx());
 202                                 OperandValue::Immediate(bx.get_fn_addr(instance))
 203                             }
 204                             _ => bug!("{} cannot be reified to a fn ptr", operand.layout.ty),
 205                         }
 206                     }
 207                     mir::CastKind::Pointer(PointerCast::ClosureFnPointer(_)) => {
 208                         match *operand.layout.ty.kind() {
 209                             ty::Closure(def_id, substs) => {
 210                                 let instance = Instance::resolve_closure(
 211                                     bx.cx().tcx(),
 212                                     def_id,
 213                                     substs,
 214                                     ty::ClosureKind::FnOnce,
 215                                 )
 216                                 .polymorphize(bx.cx().tcx());
 217                                 OperandValue::Immediate(bx.cx().get_fn_addr(instance))
 218                             }
 219                             _ => bug!("{} cannot be cast to a fn ptr", operand.layout.ty),
 220                         }
 221                     }
 222                     mir::CastKind::Pointer(PointerCast::UnsafeFnPointer) => {
 223                         // This is a no-op at the LLVM level.
 224                         operand.val
 225                     }
 226                     mir::CastKind::Pointer(PointerCast::Unsize) => {
 227                         assert!(bx.cx().is_backend_scalar_pair(cast));
 228                         let (lldata, llextra) = match operand.val {
 229                             OperandValue::Pair(lldata, llextra) => {
 230                                 // unsize from a fat pointer -- this is a
 231                                 // "trait-object-to-supertrait" coercion.
 232                                 (lldata, Some(llextra))
 233                             }
 234                             OperandValue::Immediate(lldata) => {
 235                                 // "standard" unsize
 236                                 (lldata, None)
 237                             }
 238                             OperandValue::Ref(..) => {
 239                                 bug!("by-ref operand {:?} in `codegen_rvalue_operand`", operand);
 240                             }
 241                         };
 242                         let (lldata, llextra) =
 243                             base::unsize_ptr(&mut bx, lldata, operand.layout.ty, cast.ty, llextra);
 244                         OperandValue::Pair(lldata, llextra)
 245                     }
 246                     mir::CastKind::Pointer(PointerCast::MutToConstPointer)
 247                     | mir::CastKind::Misc
 248                         if bx.cx().is_backend_scalar_pair(operand.layout) =>
 249                     {
 250                         if let OperandValue::Pair(data_ptr, meta) = operand.val {
 251                             if bx.cx().is_backend_scalar_pair(cast) {
 252                                 let data_cast = bx.pointercast(
 253                                     data_ptr,
 254                                     bx.cx().scalar_pair_element_backend_type(cast, 0, true),
 255                                 );
 256                                 OperandValue::Pair(data_cast, meta)
 257                             } else {
 258                                 // cast to thin-ptr
 259                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 260                                 // pointer-cast of that pointer to desired pointer type.
 261                                 let llcast_ty = bx.cx().immediate_backend_type(cast);
 262                                 let llval = bx.pointercast(data_ptr, llcast_ty);
 263                                 OperandValue::Immediate(llval)
 264                             }
 265                         } else {
 266                             bug!("unexpected non-pair operand");
 267                         }
 268                     }
 269                     mir::CastKind::Pointer(
 270                         PointerCast::MutToConstPointer | PointerCast::ArrayToPointer,
 271                     )
 272                     | mir::CastKind::Misc
 273                     // Since int2ptr can have arbitrary integer types as input (so we have to do
 274                     // sign extension and all that), it is currently best handled in the same code
 275                     // path as the other integer-to-X casts.
 276                     | mir::CastKind::PointerFromExposedAddress => {
 277                         assert!(bx.cx().is_backend_immediate(cast));
 278                         let ll_t_out = bx.cx().immediate_backend_type(cast);
 279                         if operand.layout.abi.is_uninhabited() {
 280                             let val = OperandValue::Immediate(bx.cx().const_undef(ll_t_out));
 281                             return (bx, OperandRef { val, layout: cast });
 282                         }
 283                         let r_t_in =
 284                             CastTy::from_ty(operand.layout.ty).expect("bad input type for cast");
 285                         let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
 286                         let ll_t_in = bx.cx().immediate_backend_type(operand.layout);
 287                         match operand.layout.variants {
 288                             Variants::Single { index } => {
 289                                 if let Some(discr) =
 290                                     operand.layout.ty.discriminant_for_variant(bx.tcx(), index)
 291                                 {
 292                                     let discr_layout = bx.cx().layout_of(discr.ty);
 293                                     let discr_t = bx.cx().immediate_backend_type(discr_layout);
 294                                     let discr_val = bx.cx().const_uint_big(discr_t, discr.val);
 295                                     let discr_val =
 296                                         bx.intcast(discr_val, ll_t_out, discr.ty.is_signed());
 297
 298                                     return (
 299                                         bx,
 300                                         OperandRef {
 301                                             val: OperandValue::Immediate(discr_val),
 302                                             layout: cast,
 303                                         },
 304                                     );
 305                                 }
 306                             }
 307                             Variants::Multiple { .. } => {}
 308                         }
 309                         let llval = operand.immediate();
 310
 311                         let mut signed = false;
 312                         if let Abi::Scalar(scalar) = operand.layout.abi {
 313                             if let Int(_, s) = scalar.primitive() {
 314                                 // We use `i1` for bytes that are always `0` or `1`,
 315                                 // e.g., `#[repr(i8)] enum E { A, B }`, but we can't
 316                                 // let LLVM interpret the `i1` as signed, because
 317                                 // then `i1 1` (i.e., E::B) is effectively `i8 -1`.
 318                                 signed = !scalar.is_bool() && s;
 319
 320                                 if !scalar.is_always_valid(bx.cx())
 321                                     && scalar.valid_range(bx.cx()).end
 322                                         >= scalar.valid_range(bx.cx()).start
 323                                 {
 324                                     // We want `table[e as usize ± k]` to not
 325                                     // have bound checks, and this is the most
 326                                     // convenient place to put the `assume`s.
 327                                     if scalar.valid_range(bx.cx()).start > 0 {
 328                                         let enum_value_lower_bound = bx.cx().const_uint_big(
 329                                             ll_t_in,
 330                                             scalar.valid_range(bx.cx()).start,
 331                                         );
 332                                         let cmp_start = bx.icmp(
 333                                             IntPredicate::IntUGE,
 334                                             llval,
 335                                             enum_value_lower_bound,
 336                                         );
 337                                         bx.assume(cmp_start);
 338                                     }
 339
 340                                     let enum_value_upper_bound = bx
 341                                         .cx()
 342                                         .const_uint_big(ll_t_in, scalar.valid_range(bx.cx()).end);
 343                                     let cmp_end = bx.icmp(
 344                                         IntPredicate::IntULE,
 345                                         llval,
 346                                         enum_value_upper_bound,
 347                                     );
 348                                     bx.assume(cmp_end);
 349                                 }
 350                             }
 351                         }
 352
 353                         let newval = match (r_t_in, r_t_out) {
 354                             (CastTy::Int(_), CastTy::Int(_)) => bx.intcast(llval, ll_t_out, signed),
 355                             (CastTy::Float, CastTy::Float) => {
 356                                 let srcsz = bx.cx().float_width(ll_t_in);
 357                                 let dstsz = bx.cx().float_width(ll_t_out);
 358                                 if dstsz > srcsz {
 359                                     bx.fpext(llval, ll_t_out)
 360                                 } else if srcsz > dstsz {
 361                                     bx.fptrunc(llval, ll_t_out)
 362                                 } else {
 363                                     llval
 364                                 }
 365                             }
 366                             (CastTy::Int(_), CastTy::Float) => {
 367                                 if signed {
 368                                     bx.sitofp(llval, ll_t_out)
 369                                 } else {
 370                                     bx.uitofp(llval, ll_t_out)
 371                                 }
 372                             }
 373                             (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Ptr(_)) => {
 374                                 bx.pointercast(llval, ll_t_out)
 375                             }
 376                             (CastTy::Int(_), CastTy::Ptr(_)) => {
 377                                 let usize_llval = bx.intcast(llval, bx.cx().type_isize(), signed);
 378                                 bx.inttoptr(usize_llval, ll_t_out)
 379                             }
 380                             (CastTy::Float, CastTy::Int(IntTy::I)) => {
 381                                 bx.cast_float_to_int(true, llval, ll_t_out)
 382                             }
 383                             (CastTy::Float, CastTy::Int(_)) => {
 384                                 bx.cast_float_to_int(false, llval, ll_t_out)
 385                             }
 386                             _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty),
 387                         };
 388                         OperandValue::Immediate(newval)
 389                     }
 390                 };
 391                 (bx, OperandRef { val, layout: cast })
 392             }
 393
 394             mir::Rvalue::Ref(_, bk, place) => {
 395                 let mk_ref = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| {
 396                     tcx.mk_ref(
 397                         tcx.lifetimes.re_erased,
 398                         ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() },
 399                     )
 400                 };
 401                 self.codegen_place_to_pointer(bx, place, mk_ref)
 402             }
 403
 404             mir::Rvalue::AddressOf(mutability, place) => {
 405                 let mk_ptr = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| {
 406                     tcx.mk_ptr(ty::TypeAndMut { ty, mutbl: mutability })
 407                 };
 408                 self.codegen_place_to_pointer(bx, place, mk_ptr)
 409             }
 410
 411             mir::Rvalue::Len(place) => {
 412                 let size = self.evaluate_array_len(&mut bx, place);
 413                 let operand = OperandRef {
 414                     val: OperandValue::Immediate(size),
 415                     layout: bx.cx().layout_of(bx.tcx().types.usize),
 416                 };
 417                 (bx, operand)
 418             }
 419
 420             mir::Rvalue::BinaryOp(op, box (ref lhs, ref rhs)) => {
 421                 let lhs = self.codegen_operand(&mut bx, lhs);
 422                 let rhs = self.codegen_operand(&mut bx, rhs);
 423                 let llresult = match (lhs.val, rhs.val) {
 424                     (
 425                         OperandValue::Pair(lhs_addr, lhs_extra),
 426                         OperandValue::Pair(rhs_addr, rhs_extra),
 427                     ) => self.codegen_fat_ptr_binop(
 428                         &mut bx,
 429                         op,
 430                         lhs_addr,
 431                         lhs_extra,
 432                         rhs_addr,
 433                         rhs_extra,
 434                         lhs.layout.ty,
 435                     ),
 436
 437                     (OperandValue::Immediate(lhs_val), OperandValue::Immediate(rhs_val)) => {
 438                         self.codegen_scalar_binop(&mut bx, op, lhs_val, rhs_val, lhs.layout.ty)
 439                     }
 440
 441                     _ => bug!(),
 442                 };
 443                 let operand = OperandRef {
 444                     val: OperandValue::Immediate(llresult),
 445                     layout: bx.cx().layout_of(op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
 446                 };
 447                 (bx, operand)
 448             }
 449             mir::Rvalue::CheckedBinaryOp(op, box (ref lhs, ref rhs)) => {
 450                 let lhs = self.codegen_operand(&mut bx, lhs);
 451                 let rhs = self.codegen_operand(&mut bx, rhs);
 452                 let result = self.codegen_scalar_checked_binop(
 453                     &mut bx,
 454                     op,
 455                     lhs.immediate(),
 456                     rhs.immediate(),
 457                     lhs.layout.ty,
 458                 );
 459                 let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
 460                 let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
 461                 let operand = OperandRef { val: result, layout: bx.cx().layout_of(operand_ty) };
 462
 463                 (bx, operand)
 464             }
 465
 466             mir::Rvalue::UnaryOp(op, ref operand) => {
 467                 let operand = self.codegen_operand(&mut bx, operand);
 468                 let lloperand = operand.immediate();
 469                 let is_float = operand.layout.ty.is_floating_point();
 470                 let llval = match op {
 471                     mir::UnOp::Not => bx.not(lloperand),
 472                     mir::UnOp::Neg => {
 473                         if is_float {
 474                             bx.fneg(lloperand)
 475                         } else {
 476                             bx.neg(lloperand)
 477                         }
 478                     }
 479                 };
 480                 (bx, OperandRef { val: OperandValue::Immediate(llval), layout: operand.layout })
 481             }
 482
 483             mir::Rvalue::Discriminant(ref place) => {
 484                 let discr_ty = rvalue.ty(self.mir, bx.tcx());
 485                 let discr_ty = self.monomorphize(discr_ty);
 486                 let discr = self
 487                     .codegen_place(&mut bx, place.as_ref())
 488                     .codegen_get_discr(&mut bx, discr_ty);
 489                 (
 490                     bx,
 491                     OperandRef {
 492                         val: OperandValue::Immediate(discr),
 493                         layout: self.cx.layout_of(discr_ty),
 494                     },
 495                 )
 496             }
 497
 498             mir::Rvalue::NullaryOp(null_op, ty) => {
 499                 let ty = self.monomorphize(ty);
 500                 assert!(bx.cx().type_is_sized(ty));
 501                 let layout = bx.cx().layout_of(ty);
 502                 let val = match null_op {
 503                     mir::NullOp::SizeOf => layout.size.bytes(),
 504                     mir::NullOp::AlignOf => layout.align.abi.bytes(),
 505                 };
 506                 let val = bx.cx().const_usize(val);
 507                 let tcx = self.cx.tcx();
 508                 (
 509                     bx,
 510                     OperandRef {
 511                         val: OperandValue::Immediate(val),
 512                         layout: self.cx.layout_of(tcx.types.usize),
 513                     },
 514                 )
 515             }
 516
 517             mir::Rvalue::ThreadLocalRef(def_id) => {
 518                 assert!(bx.cx().tcx().is_static(def_id));
 519                 let static_ = bx.get_static(def_id);
 520                 let layout = bx.layout_of(bx.cx().tcx().static_ptr_ty(def_id));
 521                 let operand = OperandRef::from_immediate_or_packed_pair(&mut bx, static_, layout);
 522                 (bx, operand)
 523             }
 524             mir::Rvalue::Use(ref operand) => {
 525                 let operand = self.codegen_operand(&mut bx, operand);
 526                 (bx, operand)
 527             }
 528             mir::Rvalue::Repeat(..) | mir::Rvalue::Aggregate(..) => {
 529                 // According to `rvalue_creates_operand`, only ZST
 530                 // aggregate rvalues are allowed to be operands.
 531                 let ty = rvalue.ty(self.mir, self.cx.tcx());
 532                 let operand =
 533                     OperandRef::new_zst(&mut bx, self.cx.layout_of(self.monomorphize(ty)));
 534                 (bx, operand)
 535             }
 536             mir::Rvalue::ShallowInitBox(ref operand, content_ty) => {
 537                 let operand = self.codegen_operand(&mut bx, operand);
 538                 let lloperand = operand.immediate();
 539
 540                 let content_ty = self.monomorphize(content_ty);
 541                 let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
 542                 let llty_ptr = bx.cx().backend_type(box_layout);
 543
 544                 let val = bx.pointercast(lloperand, llty_ptr);
 545                 let operand = OperandRef { val: OperandValue::Immediate(val), layout: box_layout };
 546                 (bx, operand)
 547             }
 548         }
 549     }
 550
 551     fn evaluate_array_len(&mut self, bx: &mut Bx, place: mir::Place<'tcx>) -> Bx::Value {
 552         // ZST are passed as operands and require special handling
 553         // because codegen_place() panics if Local is operand.
 554         if let Some(index) = place.as_local() {
 555             if let LocalRef::Operand(Some(op)) = self.locals[index] {
 556                 if let ty::Array(_, n) = op.layout.ty.kind() {
 557                     let n = n.eval_usize(bx.cx().tcx(), ty::ParamEnv::reveal_all());
 558                     return bx.cx().const_usize(n);
 559                 }
 560             }
 561         }
 562         // use common size calculation for non zero-sized types
 563         let cg_value = self.codegen_place(bx, place.as_ref());
 564         cg_value.len(bx.cx())
 565     }
 566
 567     /// Codegen an `Rvalue::AddressOf` or `Rvalue::Ref`
 568     fn codegen_place_to_pointer(
 569         &mut self,
 570         mut bx: Bx,
 571         place: mir::Place<'tcx>,
 572         mk_ptr_ty: impl FnOnce(TyCtxt<'tcx>, Ty<'tcx>) -> Ty<'tcx>,
 573     ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
 574         let cg_place = self.codegen_place(&mut bx, place.as_ref());
 575
 576         let ty = cg_place.layout.ty;
 577
 578         // Note: places are indirect, so storing the `llval` into the
 579         // destination effectively creates a reference.
 580         let val = if !bx.cx().type_has_metadata(ty) {
 581             OperandValue::Immediate(cg_place.llval)
 582         } else {
 583             OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
 584         };
 585         (bx, OperandRef { val, layout: self.cx.layout_of(mk_ptr_ty(self.cx.tcx(), ty)) })
 586     }
 587
 588     pub fn codegen_scalar_binop(
 589         &mut self,
 590         bx: &mut Bx,
 591         op: mir::BinOp,
 592         lhs: Bx::Value,
 593         rhs: Bx::Value,
 594         input_ty: Ty<'tcx>,
 595     ) -> Bx::Value {
 596         let is_float = input_ty.is_floating_point();
 597         let is_signed = input_ty.is_signed();
 598         match op {
 599             mir::BinOp::Add => {
 600                 if is_float {
 601                     bx.fadd(lhs, rhs)
 602                 } else {
 603                     bx.add(lhs, rhs)
 604                 }
 605             }
 606             mir::BinOp::Sub => {
 607                 if is_float {
 608                     bx.fsub(lhs, rhs)
 609                 } else {
 610                     bx.sub(lhs, rhs)
 611                 }
 612             }
 613             mir::BinOp::Mul => {
 614                 if is_float {
 615                     bx.fmul(lhs, rhs)
 616                 } else {
 617                     bx.mul(lhs, rhs)
 618                 }
 619             }
 620             mir::BinOp::Div => {
 621                 if is_float {
 622                     bx.fdiv(lhs, rhs)
 623                 } else if is_signed {
 624                     bx.sdiv(lhs, rhs)
 625                 } else {
 626                     bx.udiv(lhs, rhs)
 627                 }
 628             }
 629             mir::BinOp::Rem => {
 630                 if is_float {
 631                     bx.frem(lhs, rhs)
 632                 } else if is_signed {
 633                     bx.srem(lhs, rhs)
 634                 } else {
 635                     bx.urem(lhs, rhs)
 636                 }
 637             }
 638             mir::BinOp::BitOr => bx.or(lhs, rhs),
 639             mir::BinOp::BitAnd => bx.and(lhs, rhs),
 640             mir::BinOp::BitXor => bx.xor(lhs, rhs),
 641             mir::BinOp::Offset => {
 642                 let pointee_type = input_ty
 643                     .builtin_deref(true)
 644                     .unwrap_or_else(|| bug!("deref of non-pointer {:?}", input_ty))
 645                     .ty;
 646                 let llty = bx.cx().backend_type(bx.cx().layout_of(pointee_type));
 647                 bx.inbounds_gep(llty, lhs, &[rhs])
 648             }
 649             mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
 650             mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
 651             mir::BinOp::Ne
 652             | mir::BinOp::Lt
 653             | mir::BinOp::Gt
 654             | mir::BinOp::Eq
 655             | mir::BinOp::Le
 656             | mir::BinOp::Ge => {
 657                 if is_float {
 658                     bx.fcmp(base::bin_op_to_fcmp_predicate(op.to_hir_binop()), lhs, rhs)
 659                 } else {
 660                     bx.icmp(base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed), lhs, rhs)
 661                 }
 662             }
 663         }
 664     }
 665
 666     pub fn codegen_fat_ptr_binop(
 667         &mut self,
 668         bx: &mut Bx,
 669         op: mir::BinOp,
 670         lhs_addr: Bx::Value,
 671         lhs_extra: Bx::Value,
 672         rhs_addr: Bx::Value,
 673         rhs_extra: Bx::Value,
 674         _input_ty: Ty<'tcx>,
 675     ) -> Bx::Value {
 676         match op {
 677             mir::BinOp::Eq => {
 678                 let lhs = bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr);
 679                 let rhs = bx.icmp(IntPredicate::IntEQ, lhs_extra, rhs_extra);
 680                 bx.and(lhs, rhs)
 681             }
 682             mir::BinOp::Ne => {
 683                 let lhs = bx.icmp(IntPredicate::IntNE, lhs_addr, rhs_addr);
 684                 let rhs = bx.icmp(IntPredicate::IntNE, lhs_extra, rhs_extra);
 685                 bx.or(lhs, rhs)
 686             }
 687             mir::BinOp::Le | mir::BinOp::Lt | mir::BinOp::Ge | mir::BinOp::Gt => {
 688                 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
 689                 let (op, strict_op) = match op {
 690                     mir::BinOp::Lt => (IntPredicate::IntULT, IntPredicate::IntULT),
 691                     mir::BinOp::Le => (IntPredicate::IntULE, IntPredicate::IntULT),
 692                     mir::BinOp::Gt => (IntPredicate::IntUGT, IntPredicate::IntUGT),
 693                     mir::BinOp::Ge => (IntPredicate::IntUGE, IntPredicate::IntUGT),
 694                     _ => bug!(),
 695                 };
 696                 let lhs = bx.icmp(strict_op, lhs_addr, rhs_addr);
 697                 let and_lhs = bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr);
 698                 let and_rhs = bx.icmp(op, lhs_extra, rhs_extra);
 699                 let rhs = bx.and(and_lhs, and_rhs);
 700                 bx.or(lhs, rhs)
 701             }
 702             _ => {
 703                 bug!("unexpected fat ptr binop");
 704             }
 705         }
 706     }
 707
 708     pub fn codegen_scalar_checked_binop(
 709         &mut self,
 710         bx: &mut Bx,
 711         op: mir::BinOp,
 712         lhs: Bx::Value,
 713         rhs: Bx::Value,
 714         input_ty: Ty<'tcx>,
 715     ) -> OperandValue<Bx::Value> {
 716         // This case can currently arise only from functions marked
 717         // with #[rustc_inherit_overflow_checks] and inlined from
 718         // another crate (mostly core::num generic/#[inline] fns),
 719         // while the current crate doesn't use overflow checks.
 720         if !bx.cx().check_overflow() {
 721             let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 722             return OperandValue::Pair(val, bx.cx().const_bool(false));
 723         }
 724
 725         let (val, of) = match op {
 726             // These are checked using intrinsics
 727             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 728                 let oop = match op {
 729                     mir::BinOp::Add => OverflowOp::Add,
 730                     mir::BinOp::Sub => OverflowOp::Sub,
 731                     mir::BinOp::Mul => OverflowOp::Mul,
 732                     _ => unreachable!(),
 733                 };
 734                 bx.checked_binop(oop, input_ty, lhs, rhs)
 735             }
 736             mir::BinOp::Shl | mir::BinOp::Shr => {
 737                 let lhs_llty = bx.cx().val_ty(lhs);
 738                 let rhs_llty = bx.cx().val_ty(rhs);
 739                 let invert_mask = common::shift_mask_val(bx, lhs_llty, rhs_llty, true);
 740                 let outer_bits = bx.and(rhs, invert_mask);
 741
 742                 let of = bx.icmp(IntPredicate::IntNE, outer_bits, bx.cx().const_null(rhs_llty));
 743                 let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 744
 745                 (val, of)
 746             }
 747             _ => bug!("Operator `{:?}` is not a checkable operator", op),
 748         };
 749
 750         OperandValue::Pair(val, of)
 751     }
 752 }
 753
 754 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 755     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) -> bool {
 756         match *rvalue {
 757             mir::Rvalue::Ref(..) |
 758             mir::Rvalue::AddressOf(..) |
 759             mir::Rvalue::Len(..) |
 760             mir::Rvalue::Cast(..) | // (*)
 761             mir::Rvalue::ShallowInitBox(..) | // (*)
 762             mir::Rvalue::BinaryOp(..) |
 763             mir::Rvalue::CheckedBinaryOp(..) |
 764             mir::Rvalue::UnaryOp(..) |
 765             mir::Rvalue::Discriminant(..) |
 766             mir::Rvalue::NullaryOp(..) |
 767             mir::Rvalue::ThreadLocalRef(_) |
 768             mir::Rvalue::Use(..) => // (*)
 769                 true,
 770             mir::Rvalue::Repeat(..) |
 771             mir::Rvalue::Aggregate(..) => {
 772                 let ty = rvalue.ty(self.mir, self.cx.tcx());
 773                 let ty = self.monomorphize(ty);
 774                 self.cx.spanned_layout_of(ty, span).is_zst()
 775             }
 776         }
 777
 778         // (*) this is only true if the type is suitable
 779     }
 780 }