src/librustc_trans/mir/rvalue.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::{self, ValueRef};
  12 use rustc::ty::{self, Ty};
  13 use rustc::ty::cast::{CastTy, IntTy};
  14 use rustc::mir::repr as mir;
  15
  16 use asm;
  17 use base;
  18 use callee::Callee;
  19 use common::{self, val_ty, C_bool, C_null, C_uint, BlockAndBuilder, Result};
  20 use debuginfo::DebugLoc;
  21 use adt;
  22 use machine;
  23 use type_of;
  24 use tvec;
  25 use value::Value;
  26 use Disr;
  27
  28 use super::MirContext;
  29 use super::constant::const_scalar_checked_binop;
  30 use super::operand::{OperandRef, OperandValue};
  31 use super::lvalue::{LvalueRef, get_dataptr};
  32
  33 impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
  34     pub fn trans_rvalue(&mut self,
  35                         bcx: BlockAndBuilder<'bcx, 'tcx>,
  36                         dest: LvalueRef<'tcx>,
  37                         rvalue: &mir::Rvalue<'tcx>,
  38                         debug_loc: DebugLoc)
  39                         -> BlockAndBuilder<'bcx, 'tcx>
  40     {
  41         debug!("trans_rvalue(dest.llval={:?}, rvalue={:?})",
  42                Value(dest.llval), rvalue);
  43
  44         match *rvalue {
  45            mir::Rvalue::Use(ref operand) => {
  46                let tr_operand = self.trans_operand(&bcx, operand);
  47                // FIXME: consider not copying constants through stack. (fixable by translating
  48                // constants into OperandValue::Ref, why don’t we do that yet if we don’t?)
  49                self.store_operand(&bcx, dest.llval, tr_operand);
  50                bcx
  51            }
  52
  53             mir::Rvalue::Cast(mir::CastKind::Unsize, ref source, cast_ty) => {
  54                 let cast_ty = bcx.monomorphize(&cast_ty);
  55
  56                 if common::type_is_fat_ptr(bcx.tcx(), cast_ty) {
  57                     // into-coerce of a thin pointer to a fat pointer - just
  58                     // use the operand path.
  59                     let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue, debug_loc);
  60                     self.store_operand(&bcx, dest.llval, temp);
  61                     return bcx;
  62                 }
  63
  64                 // Unsize of a nontrivial struct. I would prefer for
  65                 // this to be eliminated by MIR translation, but
  66                 // `CoerceUnsized` can be passed by a where-clause,
  67                 // so the (generic) MIR may not be able to expand it.
  68                 let operand = self.trans_operand(&bcx, source);
  69                 let operand = operand.pack_if_pair(&bcx);
  70                 bcx.with_block(|bcx| {
  71                     match operand.val {
  72                         OperandValue::Pair(..) => bug!(),
  73                         OperandValue::Immediate(llval) => {
  74                             // unsize from an immediate structure. We don't
  75                             // really need a temporary alloca here, but
  76                             // avoiding it would require us to have
  77                             // `coerce_unsized_into` use extractvalue to
  78                             // index into the struct, and this case isn't
  79                             // important enough for it.
  80                             debug!("trans_rvalue: creating ugly alloca");
  81                             let lltemp = base::alloc_ty(bcx, operand.ty, "__unsize_temp");
  82                             base::store_ty(bcx, llval, lltemp, operand.ty);
  83                             base::coerce_unsized_into(bcx,
  84                                                       lltemp, operand.ty,
  85                                                       dest.llval, cast_ty);
  86                         }
  87                         OperandValue::Ref(llref) => {
  88                             base::coerce_unsized_into(bcx,
  89                                                       llref, operand.ty,
  90                                                       dest.llval, cast_ty);
  91                         }
  92                     }
  93                 });
  94                 bcx
  95             }
  96
  97             mir::Rvalue::Repeat(ref elem, ref count) => {
  98                 let tr_elem = self.trans_operand(&bcx, elem);
  99                 let size = count.value.as_u64(bcx.tcx().sess.target.uint_type);
 100                 let size = C_uint(bcx.ccx(), size);
 101                 let base = get_dataptr(&bcx, dest.llval);
 102                 let bcx = bcx.map_block(|block| {
 103                     tvec::slice_for_each(block, base, tr_elem.ty, size, |block, llslot| {
 104                         self.store_operand_direct(block, llslot, tr_elem);
 105                         block
 106                     })
 107                 });
 108                 bcx
 109             }
 110
 111             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 112                 match *kind {
 113                     mir::AggregateKind::Adt(adt_def, index, _) => {
 114                         let repr = adt::represent_type(bcx.ccx(), dest.ty.to_ty(bcx.tcx()));
 115                         let disr = Disr::from(adt_def.variants[index].disr_val);
 116                         bcx.with_block(|bcx| {
 117                             adt::trans_set_discr(bcx, &repr, dest.llval, Disr::from(disr));
 118                         });
 119                         for (i, operand) in operands.iter().enumerate() {
 120                             let op = self.trans_operand(&bcx, operand);
 121                             // Do not generate stores and GEPis for zero-sized fields.
 122                             if !common::type_is_zero_size(bcx.ccx(), op.ty) {
 123                                 let val = adt::MaybeSizedValue::sized(dest.llval);
 124                                 let lldest_i = adt::trans_field_ptr_builder(&bcx, &repr,
 125                                                                             val, disr, i);
 126                                 self.store_operand(&bcx, lldest_i, op);
 127                             }
 128                         }
 129                     },
 130                     _ => {
 131                         // FIXME Shouldn't need to manually trigger closure instantiations.
 132                         if let mir::AggregateKind::Closure(def_id, substs) = *kind {
 133                             use closure;
 134
 135                             closure::trans_closure_body_via_mir(bcx.ccx(),
 136                                                                 def_id,
 137                                                                 bcx.monomorphize(&substs));
 138                         }
 139
 140                         for (i, operand) in operands.iter().enumerate() {
 141                             let op = self.trans_operand(&bcx, operand);
 142                             // Do not generate stores and GEPis for zero-sized fields.
 143                             if !common::type_is_zero_size(bcx.ccx(), op.ty) {
 144                                 // Note: perhaps this should be StructGep, but
 145                                 // note that in some cases the values here will
 146                                 // not be structs but arrays.
 147                                 let dest = bcx.gepi(dest.llval, &[0, i]);
 148                                 self.store_operand(&bcx, dest, op);
 149                             }
 150                         }
 151                     }
 152                 }
 153                 bcx
 154             }
 155
 156             mir::Rvalue::InlineAsm { ref asm, ref outputs, ref inputs } => {
 157                 let outputs = outputs.iter().map(|output| {
 158                     let lvalue = self.trans_lvalue(&bcx, output);
 159                     (lvalue.llval, lvalue.ty.to_ty(bcx.tcx()))
 160                 }).collect();
 161
 162                 let input_vals = inputs.iter().map(|input| {
 163                     self.trans_operand(&bcx, input).immediate()
 164                 }).collect();
 165
 166                 bcx.with_block(|bcx| {
 167                     asm::trans_inline_asm(bcx, asm, outputs, input_vals);
 168                 });
 169
 170                 bcx
 171             }
 172
 173             _ => {
 174                 assert!(rvalue_creates_operand(&self.mir, &bcx, rvalue));
 175                 let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue, debug_loc);
 176                 self.store_operand(&bcx, dest.llval, temp);
 177                 bcx
 178             }
 179         }
 180     }
 181
 182     pub fn trans_rvalue_operand(&mut self,
 183                                 bcx: BlockAndBuilder<'bcx, 'tcx>,
 184                                 rvalue: &mir::Rvalue<'tcx>,
 185                                 debug_loc: DebugLoc)
 186                                 -> (BlockAndBuilder<'bcx, 'tcx>, OperandRef<'tcx>)
 187     {
 188         assert!(rvalue_creates_operand(&self.mir, &bcx, rvalue),
 189                 "cannot trans {:?} to operand", rvalue);
 190
 191         match *rvalue {
 192             mir::Rvalue::Cast(ref kind, ref source, cast_ty) => {
 193                 let operand = self.trans_operand(&bcx, source);
 194                 debug!("cast operand is {:?}", operand);
 195                 let cast_ty = bcx.monomorphize(&cast_ty);
 196
 197                 let val = match *kind {
 198                     mir::CastKind::ReifyFnPointer => {
 199                         match operand.ty.sty {
 200                             ty::TyFnDef(def_id, substs, _) => {
 201                                 OperandValue::Immediate(
 202                                     Callee::def(bcx.ccx(), def_id, substs)
 203                                         .reify(bcx.ccx()))
 204                             }
 205                             _ => {
 206                                 bug!("{} cannot be reified to a fn ptr", operand.ty)
 207                             }
 208                         }
 209                     }
 210                     mir::CastKind::UnsafeFnPointer => {
 211                         // this is a no-op at the LLVM level
 212                         operand.val
 213                     }
 214                     mir::CastKind::Unsize => {
 215                         // unsize targets other than to a fat pointer currently
 216                         // can't be operands.
 217                         assert!(common::type_is_fat_ptr(bcx.tcx(), cast_ty));
 218
 219                         match operand.val {
 220                             OperandValue::Pair(lldata, llextra) => {
 221                                 // unsize from a fat pointer - this is a
 222                                 // "trait-object-to-supertrait" coercion, for
 223                                 // example,
 224                                 //   &'a fmt::Debug+Send => &'a fmt::Debug,
 225                                 // So we need to pointercast the base to ensure
 226                                 // the types match up.
 227                                 let llcast_ty = type_of::fat_ptr_base_ty(bcx.ccx(), cast_ty);
 228                                 let lldata = bcx.pointercast(lldata, llcast_ty);
 229                                 OperandValue::Pair(lldata, llextra)
 230                             }
 231                             OperandValue::Immediate(lldata) => {
 232                                 // "standard" unsize
 233                                 let (lldata, llextra) = bcx.with_block(|bcx| {
 234                                     base::unsize_thin_ptr(bcx, lldata,
 235                                                           operand.ty, cast_ty)
 236                                 });
 237                                 OperandValue::Pair(lldata, llextra)
 238                             }
 239                             OperandValue::Ref(_) => {
 240                                 bug!("by-ref operand {:?} in trans_rvalue_operand",
 241                                      operand);
 242                             }
 243                         }
 244                     }
 245                     mir::CastKind::Misc if common::type_is_fat_ptr(bcx.tcx(), operand.ty) => {
 246                         let ll_cast_ty = type_of::immediate_type_of(bcx.ccx(), cast_ty);
 247                         let ll_from_ty = type_of::immediate_type_of(bcx.ccx(), operand.ty);
 248                         if let OperandValue::Pair(data_ptr, meta_ptr) = operand.val {
 249                             if common::type_is_fat_ptr(bcx.tcx(), cast_ty) {
 250                                 let ll_cft = ll_cast_ty.field_types();
 251                                 let ll_fft = ll_from_ty.field_types();
 252                                 let data_cast = bcx.pointercast(data_ptr, ll_cft[0]);
 253                                 assert_eq!(ll_cft[1].kind(), ll_fft[1].kind());
 254                                 OperandValue::Pair(data_cast, meta_ptr)
 255                             } else { // cast to thin-ptr
 256                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 257                                 // pointer-cast of that pointer to desired pointer type.
 258                                 let llval = bcx.pointercast(data_ptr, ll_cast_ty);
 259                                 OperandValue::Immediate(llval)
 260                             }
 261                         } else {
 262                             bug!("Unexpected non-Pair operand")
 263                         }
 264                     }
 265                     mir::CastKind::Misc => {
 266                         debug_assert!(common::type_is_immediate(bcx.ccx(), cast_ty));
 267                         let r_t_in = CastTy::from_ty(operand.ty).expect("bad input type for cast");
 268                         let r_t_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
 269                         let ll_t_in = type_of::immediate_type_of(bcx.ccx(), operand.ty);
 270                         let ll_t_out = type_of::immediate_type_of(bcx.ccx(), cast_ty);
 271                         let (llval, signed) = if let CastTy::Int(IntTy::CEnum) = r_t_in {
 272                             let repr = adt::represent_type(bcx.ccx(), operand.ty);
 273                             let discr = match operand.val {
 274                                 OperandValue::Immediate(llval) => llval,
 275                                 OperandValue::Ref(llptr) => {
 276                                     bcx.with_block(|bcx| {
 277                                         adt::trans_get_discr(bcx, &repr, llptr, None, true)
 278                                     })
 279                                 }
 280                                 OperandValue::Pair(..) => bug!("Unexpected Pair operand")
 281                             };
 282                             (discr, adt::is_discr_signed(&repr))
 283                         } else {
 284                             (operand.immediate(), operand.ty.is_signed())
 285                         };
 286
 287                         let newval = match (r_t_in, r_t_out) {
 288                             (CastTy::Int(_), CastTy::Int(_)) => {
 289                                 let srcsz = ll_t_in.int_width();
 290                                 let dstsz = ll_t_out.int_width();
 291                                 if srcsz == dstsz {
 292                                     bcx.bitcast(llval, ll_t_out)
 293                                 } else if srcsz > dstsz {
 294                                     bcx.trunc(llval, ll_t_out)
 295                                 } else if signed {
 296                                     bcx.sext(llval, ll_t_out)
 297                                 } else {
 298                                     bcx.zext(llval, ll_t_out)
 299                                 }
 300                             }
 301                             (CastTy::Float, CastTy::Float) => {
 302                                 let srcsz = ll_t_in.float_width();
 303                                 let dstsz = ll_t_out.float_width();
 304                                 if dstsz > srcsz {
 305                                     bcx.fpext(llval, ll_t_out)
 306                                 } else if srcsz > dstsz {
 307                                     bcx.fptrunc(llval, ll_t_out)
 308                                 } else {
 309                                     llval
 310                                 }
 311                             }
 312                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 313                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 314                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 315                                 bcx.pointercast(llval, ll_t_out),
 316                             (CastTy::Ptr(_), CastTy::Int(_)) |
 317                             (CastTy::FnPtr, CastTy::Int(_)) =>
 318                                 bcx.ptrtoint(llval, ll_t_out),
 319                             (CastTy::Int(_), CastTy::Ptr(_)) =>
 320                                 bcx.inttoptr(llval, ll_t_out),
 321                             (CastTy::Int(_), CastTy::Float) if signed =>
 322                                 bcx.sitofp(llval, ll_t_out),
 323                             (CastTy::Int(_), CastTy::Float) =>
 324                                 bcx.uitofp(llval, ll_t_out),
 325                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 326                                 bcx.fptosi(llval, ll_t_out),
 327                             (CastTy::Float, CastTy::Int(_)) =>
 328                                 bcx.fptoui(llval, ll_t_out),
 329                             _ => bug!("unsupported cast: {:?} to {:?}", operand.ty, cast_ty)
 330                         };
 331                         OperandValue::Immediate(newval)
 332                     }
 333                 };
 334                 let operand = OperandRef {
 335                     val: val,
 336                     ty: cast_ty
 337                 };
 338                 (bcx, operand)
 339             }
 340
 341             mir::Rvalue::Ref(_, bk, ref lvalue) => {
 342                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 343
 344                 let ty = tr_lvalue.ty.to_ty(bcx.tcx());
 345                 let ref_ty = bcx.tcx().mk_ref(
 346                     bcx.tcx().mk_region(ty::ReErased),
 347                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() }
 348                 );
 349
 350                 // Note: lvalues are indirect, so storing the `llval` into the
 351                 // destination effectively creates a reference.
 352                 let operand = if common::type_is_sized(bcx.tcx(), ty) {
 353                     OperandRef {
 354                         val: OperandValue::Immediate(tr_lvalue.llval),
 355                         ty: ref_ty,
 356                     }
 357                 } else {
 358                     OperandRef {
 359                         val: OperandValue::Pair(tr_lvalue.llval,
 360                                                 tr_lvalue.llextra),
 361                         ty: ref_ty,
 362                     }
 363                 };
 364                 (bcx, operand)
 365             }
 366
 367             mir::Rvalue::Len(ref lvalue) => {
 368                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 369                 let operand = OperandRef {
 370                     val: OperandValue::Immediate(tr_lvalue.len(bcx.ccx())),
 371                     ty: bcx.tcx().types.usize,
 372                 };
 373                 (bcx, operand)
 374             }
 375
 376             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 377                 let lhs = self.trans_operand(&bcx, lhs);
 378                 let rhs = self.trans_operand(&bcx, rhs);
 379                 let llresult = if common::type_is_fat_ptr(bcx.tcx(), lhs.ty) {
 380                     match (lhs.val, rhs.val) {
 381                         (OperandValue::Pair(lhs_addr, lhs_extra),
 382                          OperandValue::Pair(rhs_addr, rhs_extra)) => {
 383                             bcx.with_block(|bcx| {
 384                                 base::compare_fat_ptrs(bcx,
 385                                                        lhs_addr, lhs_extra,
 386                                                        rhs_addr, rhs_extra,
 387                                                        lhs.ty, op.to_hir_binop(),
 388                                                        debug_loc)
 389                             })
 390                         }
 391                         _ => bug!()
 392                     }
 393
 394                 } else {
 395                     self.trans_scalar_binop(&bcx, op,
 396                                             lhs.immediate(), rhs.immediate(),
 397                                             lhs.ty)
 398                 };
 399                 let operand = OperandRef {
 400                     val: OperandValue::Immediate(llresult),
 401                     ty: op.ty(bcx.tcx(), lhs.ty, rhs.ty),
 402                 };
 403                 (bcx, operand)
 404             }
 405             mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
 406                 let lhs = self.trans_operand(&bcx, lhs);
 407                 let rhs = self.trans_operand(&bcx, rhs);
 408                 let result = self.trans_scalar_checked_binop(&bcx, op,
 409                                                              lhs.immediate(), rhs.immediate(),
 410                                                              lhs.ty);
 411                 let val_ty = op.ty(bcx.tcx(), lhs.ty, rhs.ty);
 412                 let operand_ty = bcx.tcx().mk_tup(vec![val_ty, bcx.tcx().types.bool]);
 413                 let operand = OperandRef {
 414                     val: result,
 415                     ty: operand_ty
 416                 };
 417
 418                 (bcx, operand)
 419             }
 420
 421             mir::Rvalue::UnaryOp(op, ref operand) => {
 422                 let operand = self.trans_operand(&bcx, operand);
 423                 let lloperand = operand.immediate();
 424                 let is_float = operand.ty.is_fp();
 425                 let llval = match op {
 426                     mir::UnOp::Not => bcx.not(lloperand),
 427                     mir::UnOp::Neg => if is_float {
 428                         bcx.fneg(lloperand)
 429                     } else {
 430                         bcx.neg(lloperand)
 431                     }
 432                 };
 433                 (bcx, OperandRef {
 434                     val: OperandValue::Immediate(llval),
 435                     ty: operand.ty,
 436                 })
 437             }
 438
 439             mir::Rvalue::Box(content_ty) => {
 440                 let content_ty: Ty<'tcx> = bcx.monomorphize(&content_ty);
 441                 let llty = type_of::type_of(bcx.ccx(), content_ty);
 442                 let llsize = machine::llsize_of(bcx.ccx(), llty);
 443                 let align = type_of::align_of(bcx.ccx(), content_ty);
 444                 let llalign = C_uint(bcx.ccx(), align);
 445                 let llty_ptr = llty.ptr_to();
 446                 let box_ty = bcx.tcx().mk_box(content_ty);
 447                 let mut llval = None;
 448                 let bcx = bcx.map_block(|bcx| {
 449                     let Result { bcx, val } = base::malloc_raw_dyn(bcx,
 450                                                                    llty_ptr,
 451                                                                    box_ty,
 452                                                                    llsize,
 453                                                                    llalign,
 454                                                                    debug_loc);
 455                     llval = Some(val);
 456                     bcx
 457                 });
 458                 let operand = OperandRef {
 459                     val: OperandValue::Immediate(llval.unwrap()),
 460                     ty: box_ty,
 461                 };
 462                 (bcx, operand)
 463             }
 464
 465             mir::Rvalue::Use(ref operand) => {
 466                 let operand = self.trans_operand(&bcx, operand);
 467                 (bcx, operand)
 468             }
 469             mir::Rvalue::Repeat(..) |
 470             mir::Rvalue::Aggregate(..) |
 471             mir::Rvalue::InlineAsm { .. } => {
 472                 bug!("cannot generate operand from rvalue {:?}", rvalue);
 473
 474             }
 475         }
 476     }
 477
 478     pub fn trans_scalar_binop(&mut self,
 479                               bcx: &BlockAndBuilder<'bcx, 'tcx>,
 480                               op: mir::BinOp,
 481                               lhs: ValueRef,
 482                               rhs: ValueRef,
 483                               input_ty: Ty<'tcx>) -> ValueRef {
 484         let is_float = input_ty.is_fp();
 485         let is_signed = input_ty.is_signed();
 486         match op {
 487             mir::BinOp::Add => if is_float {
 488                 bcx.fadd(lhs, rhs)
 489             } else {
 490                 bcx.add(lhs, rhs)
 491             },
 492             mir::BinOp::Sub => if is_float {
 493                 bcx.fsub(lhs, rhs)
 494             } else {
 495                 bcx.sub(lhs, rhs)
 496             },
 497             mir::BinOp::Mul => if is_float {
 498                 bcx.fmul(lhs, rhs)
 499             } else {
 500                 bcx.mul(lhs, rhs)
 501             },
 502             mir::BinOp::Div => if is_float {
 503                 bcx.fdiv(lhs, rhs)
 504             } else if is_signed {
 505                 bcx.sdiv(lhs, rhs)
 506             } else {
 507                 bcx.udiv(lhs, rhs)
 508             },
 509             mir::BinOp::Rem => if is_float {
 510                 bcx.frem(lhs, rhs)
 511             } else if is_signed {
 512                 bcx.srem(lhs, rhs)
 513             } else {
 514                 bcx.urem(lhs, rhs)
 515             },
 516             mir::BinOp::BitOr => bcx.or(lhs, rhs),
 517             mir::BinOp::BitAnd => bcx.and(lhs, rhs),
 518             mir::BinOp::BitXor => bcx.xor(lhs, rhs),
 519             mir::BinOp::Shl => {
 520                 bcx.with_block(|bcx| {
 521                     common::build_unchecked_lshift(bcx,
 522                                                    lhs,
 523                                                    rhs,
 524                                                    DebugLoc::None)
 525                 })
 526             }
 527             mir::BinOp::Shr => {
 528                 bcx.with_block(|bcx| {
 529                     common::build_unchecked_rshift(bcx,
 530                                                    input_ty,
 531                                                    lhs,
 532                                                    rhs,
 533                                                    DebugLoc::None)
 534                 })
 535             }
 536             mir::BinOp::Eq | mir::BinOp::Lt | mir::BinOp::Gt |
 537             mir::BinOp::Ne | mir::BinOp::Le | mir::BinOp::Ge => {
 538                 bcx.with_block(|bcx| {
 539                     base::compare_scalar_types(bcx, lhs, rhs, input_ty,
 540                                                op.to_hir_binop(), DebugLoc::None)
 541                 })
 542             }
 543         }
 544     }
 545
 546     pub fn trans_scalar_checked_binop(&mut self,
 547                                       bcx: &BlockAndBuilder<'bcx, 'tcx>,
 548                                       op: mir::BinOp,
 549                                       lhs: ValueRef,
 550                                       rhs: ValueRef,
 551                                       input_ty: Ty<'tcx>) -> OperandValue {
 552         // This case can currently arise only from functions marked
 553         // with #[rustc_inherit_overflow_checks] and inlined from
 554         // another crate (mostly core::num generic/#[inline] fns),
 555         // while the current crate doesn't use overflow checks.
 556         if !bcx.ccx().check_overflow() {
 557             let val = self.trans_scalar_binop(bcx, op, lhs, rhs, input_ty);
 558             return OperandValue::Pair(val, C_bool(bcx.ccx(), false));
 559         }
 560
 561         // First try performing the operation on constants, which
 562         // will only succeed if both operands are constant.
 563         // This is necessary to determine when an overflow Assert
 564         // will always panic at runtime, and produce a warning.
 565         if let Some((val, of)) = const_scalar_checked_binop(bcx.tcx(), op, lhs, rhs, input_ty) {
 566             return OperandValue::Pair(val, C_bool(bcx.ccx(), of));
 567         }
 568
 569         let (val, of) = match op {
 570             // These are checked using intrinsics
 571             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 572                 let oop = match op {
 573                     mir::BinOp::Add => OverflowOp::Add,
 574                     mir::BinOp::Sub => OverflowOp::Sub,
 575                     mir::BinOp::Mul => OverflowOp::Mul,
 576                     _ => unreachable!()
 577                 };
 578                 let intrinsic = get_overflow_intrinsic(oop, bcx, input_ty);
 579                 let res = bcx.call(intrinsic, &[lhs, rhs], None);
 580
 581                 (bcx.extract_value(res, 0),
 582                  bcx.extract_value(res, 1))
 583             }
 584             mir::BinOp::Shl | mir::BinOp::Shr => {
 585                 let lhs_llty = val_ty(lhs);
 586                 let rhs_llty = val_ty(rhs);
 587                 let invert_mask = bcx.with_block(|bcx| {
 588                     common::shift_mask_val(bcx, lhs_llty, rhs_llty, true)
 589                 });
 590                 let outer_bits = bcx.and(rhs, invert_mask);
 591
 592                 let of = bcx.icmp(llvm::IntNE, outer_bits, C_null(rhs_llty));
 593                 let val = self.trans_scalar_binop(bcx, op, lhs, rhs, input_ty);
 594
 595                 (val, of)
 596             }
 597             _ => {
 598                 bug!("Operator `{:?}` is not a checkable operator", op)
 599             }
 600         };
 601
 602         OperandValue::Pair(val, of)
 603     }
 604 }
 605
 606 pub fn rvalue_creates_operand<'bcx, 'tcx>(_mir: &mir::Mir<'tcx>,
 607                                           _bcx: &BlockAndBuilder<'bcx, 'tcx>,
 608                                           rvalue: &mir::Rvalue<'tcx>) -> bool {
 609     match *rvalue {
 610         mir::Rvalue::Ref(..) |
 611         mir::Rvalue::Len(..) |
 612         mir::Rvalue::Cast(..) | // (*)
 613         mir::Rvalue::BinaryOp(..) |
 614         mir::Rvalue::CheckedBinaryOp(..) |
 615         mir::Rvalue::UnaryOp(..) |
 616         mir::Rvalue::Box(..) |
 617         mir::Rvalue::Use(..) =>
 618             true,
 619         mir::Rvalue::Repeat(..) |
 620         mir::Rvalue::Aggregate(..) |
 621         mir::Rvalue::InlineAsm { .. } =>
 622             false,
 623     }
 624
 625     // (*) this is only true if the type is suitable
 626 }
 627
 628 #[derive(Copy, Clone)]
 629 enum OverflowOp {
 630     Add, Sub, Mul
 631 }
 632
 633 fn get_overflow_intrinsic(oop: OverflowOp, bcx: &BlockAndBuilder, ty: Ty) -> ValueRef {
 634     use syntax::ast::IntTy::*;
 635     use syntax::ast::UintTy::*;
 636     use rustc::ty::{TyInt, TyUint};
 637
 638     let tcx = bcx.tcx();
 639
 640     let new_sty = match ty.sty {
 641         TyInt(Is) => match &tcx.sess.target.target.target_pointer_width[..] {
 642             "32" => TyInt(I32),
 643             "64" => TyInt(I64),
 644             _ => panic!("unsupported target word size")
 645         },
 646         TyUint(Us) => match &tcx.sess.target.target.target_pointer_width[..] {
 647             "32" => TyUint(U32),
 648             "64" => TyUint(U64),
 649             _ => panic!("unsupported target word size")
 650         },
 651         ref t @ TyUint(_) | ref t @ TyInt(_) => t.clone(),
 652         _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
 653     };
 654
 655     let name = match oop {
 656         OverflowOp::Add => match new_sty {
 657             TyInt(I8) => "llvm.sadd.with.overflow.i8",
 658             TyInt(I16) => "llvm.sadd.with.overflow.i16",
 659             TyInt(I32) => "llvm.sadd.with.overflow.i32",
 660             TyInt(I64) => "llvm.sadd.with.overflow.i64",
 661
 662             TyUint(U8) => "llvm.uadd.with.overflow.i8",
 663             TyUint(U16) => "llvm.uadd.with.overflow.i16",
 664             TyUint(U32) => "llvm.uadd.with.overflow.i32",
 665             TyUint(U64) => "llvm.uadd.with.overflow.i64",
 666
 667             _ => unreachable!(),
 668         },
 669         OverflowOp::Sub => match new_sty {
 670             TyInt(I8) => "llvm.ssub.with.overflow.i8",
 671             TyInt(I16) => "llvm.ssub.with.overflow.i16",
 672             TyInt(I32) => "llvm.ssub.with.overflow.i32",
 673             TyInt(I64) => "llvm.ssub.with.overflow.i64",
 674
 675             TyUint(U8) => "llvm.usub.with.overflow.i8",
 676             TyUint(U16) => "llvm.usub.with.overflow.i16",
 677             TyUint(U32) => "llvm.usub.with.overflow.i32",
 678             TyUint(U64) => "llvm.usub.with.overflow.i64",
 679
 680             _ => unreachable!(),
 681         },
 682         OverflowOp::Mul => match new_sty {
 683             TyInt(I8) => "llvm.smul.with.overflow.i8",
 684             TyInt(I16) => "llvm.smul.with.overflow.i16",
 685             TyInt(I32) => "llvm.smul.with.overflow.i32",
 686             TyInt(I64) => "llvm.smul.with.overflow.i64",
 687
 688             TyUint(U8) => "llvm.umul.with.overflow.i8",
 689             TyUint(U16) => "llvm.umul.with.overflow.i16",
 690             TyUint(U32) => "llvm.umul.with.overflow.i32",
 691             TyUint(U64) => "llvm.umul.with.overflow.i64",
 692
 693             _ => unreachable!(),
 694         },
 695     };
 696
 697     bcx.ccx().get_intrinsic(&name)
 698 }