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::ty::layout::{Layout, LayoutTyper};
  15 use rustc::mir::tcx::LvalueTy;
  16 use rustc::mir;
  17 use middle::lang_items::ExchangeMallocFnLangItem;
  18
  19 use base;
  20 use builder::Builder;
  21 use callee;
  22 use common::{self, val_ty, C_bool, C_null, C_uint};
  23 use common::{C_integral};
  24 use adt;
  25 use machine;
  26 use monomorphize;
  27 use type_::Type;
  28 use type_of;
  29 use tvec;
  30 use value::Value;
  31 use Disr;
  32
  33 use super::MirContext;
  34 use super::constant::const_scalar_checked_binop;
  35 use super::operand::{OperandRef, OperandValue};
  36 use super::lvalue::LvalueRef;
  37
  38 impl<'a, 'tcx> MirContext<'a, 'tcx> {
  39     pub fn trans_rvalue(&mut self,
  40                         bcx: Builder<'a, 'tcx>,
  41                         dest: LvalueRef<'tcx>,
  42                         rvalue: &mir::Rvalue<'tcx>)
  43                         -> Builder<'a, 'tcx>
  44     {
  45         debug!("trans_rvalue(dest.llval={:?}, rvalue={:?})",
  46                Value(dest.llval), rvalue);
  47
  48         match *rvalue {
  49            mir::Rvalue::Use(ref operand) => {
  50                let tr_operand = self.trans_operand(&bcx, operand);
  51                // FIXME: consider not copying constants through stack. (fixable by translating
  52                // constants into OperandValue::Ref, why don’t we do that yet if we don’t?)
  53                self.store_operand(&bcx, dest.llval, dest.alignment.to_align(), tr_operand);
  54                bcx
  55            }
  56
  57             mir::Rvalue::Cast(mir::CastKind::Unsize, ref source, cast_ty) => {
  58                 let cast_ty = self.monomorphize(&cast_ty);
  59
  60                 if common::type_is_fat_ptr(bcx.ccx, cast_ty) {
  61                     // into-coerce of a thin pointer to a fat pointer - just
  62                     // use the operand path.
  63                     let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue);
  64                     self.store_operand(&bcx, dest.llval, dest.alignment.to_align(), temp);
  65                     return bcx;
  66                 }
  67
  68                 // Unsize of a nontrivial struct. I would prefer for
  69                 // this to be eliminated by MIR translation, but
  70                 // `CoerceUnsized` can be passed by a where-clause,
  71                 // so the (generic) MIR may not be able to expand it.
  72                 let operand = self.trans_operand(&bcx, source);
  73                 let operand = operand.pack_if_pair(&bcx);
  74                 let llref = match operand.val {
  75                     OperandValue::Pair(..) => bug!(),
  76                     OperandValue::Immediate(llval) => {
  77                         // unsize from an immediate structure. We don't
  78                         // really need a temporary alloca here, but
  79                         // avoiding it would require us to have
  80                         // `coerce_unsized_into` use extractvalue to
  81                         // index into the struct, and this case isn't
  82                         // important enough for it.
  83                         debug!("trans_rvalue: creating ugly alloca");
  84                         let scratch = LvalueRef::alloca(&bcx, operand.ty, "__unsize_temp");
  85                         base::store_ty(&bcx, llval, scratch.llval, scratch.alignment, operand.ty);
  86                         scratch
  87                     }
  88                     OperandValue::Ref(llref, align) => {
  89                         LvalueRef::new_sized_ty(llref, operand.ty, align)
  90                     }
  91                 };
  92                 base::coerce_unsized_into(&bcx, &llref, &dest);
  93                 bcx
  94             }
  95
  96             mir::Rvalue::Repeat(ref elem, ref count) => {
  97                 let tr_elem = self.trans_operand(&bcx, elem);
  98                 let size = count.as_u64(bcx.tcx().sess.target.uint_type);
  99                 let size = C_uint(bcx.ccx, size);
 100                 let base = base::get_dataptr(&bcx, dest.llval);
 101                 tvec::slice_for_each(&bcx, base, tr_elem.ty, size, |bcx, llslot, loop_bb| {
 102                     self.store_operand(bcx, llslot, dest.alignment.to_align(), tr_elem);
 103                     bcx.br(loop_bb);
 104                 })
 105             }
 106
 107             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 108                 match *kind {
 109                     mir::AggregateKind::Adt(adt_def, variant_index, substs, active_field_index) => {
 110                         let disr = Disr::for_variant(bcx.tcx(), adt_def, variant_index);
 111                         let dest_ty = dest.ty.to_ty(bcx.tcx());
 112                         adt::trans_set_discr(&bcx, dest_ty, dest.llval, disr);
 113                         for (i, operand) in operands.iter().enumerate() {
 114                             let op = self.trans_operand(&bcx, operand);
 115                             // Do not generate stores and GEPis for zero-sized fields.
 116                             if !common::type_is_zero_size(bcx.ccx, op.ty) {
 117                                 let mut val = LvalueRef::new_sized(
 118                                     dest.llval, dest.ty, dest.alignment);
 119                                 let field_index = active_field_index.unwrap_or(i);
 120                                 val.ty = LvalueTy::Downcast {
 121                                     adt_def: adt_def,
 122                                     substs: self.monomorphize(&substs),
 123                                     variant_index: variant_index,
 124                                 };
 125                                 let (lldest_i, align) = val.trans_field_ptr(&bcx, field_index);
 126                                 self.store_operand(&bcx, lldest_i, align.to_align(), op);
 127                             }
 128                         }
 129                     },
 130                     _ => {
 131                         // If this is a tuple or closure, we need to translate GEP indices.
 132                         let layout = bcx.ccx.layout_of(dest.ty.to_ty(bcx.tcx()));
 133                         let translation = if let Layout::Univariant { ref variant, .. } = *layout {
 134                             Some(&variant.memory_index)
 135                         } else {
 136                             None
 137                         };
 138                         let alignment = dest.alignment;
 139                         for (i, operand) in operands.iter().enumerate() {
 140                             let op = self.trans_operand(&bcx, operand);
 141                             // Do not generate stores and GEPis for zero-sized fields.
 142                             if !common::type_is_zero_size(bcx.ccx, op.ty) {
 143                                 // Note: perhaps this should be StructGep, but
 144                                 // note that in some cases the values here will
 145                                 // not be structs but arrays.
 146                                 let i = if let Some(ref t) = translation {
 147                                     t[i] as usize
 148                                 } else {
 149                                     i
 150                                 };
 151                                 let dest = bcx.gepi(dest.llval, &[0, i]);
 152                                 self.store_operand(&bcx, dest, alignment.to_align(), op);
 153                             }
 154                         }
 155                     }
 156                 }
 157                 bcx
 158             }
 159
 160             _ => {
 161                 assert!(rvalue_creates_operand(rvalue));
 162                 let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue);
 163                 self.store_operand(&bcx, dest.llval, dest.alignment.to_align(), temp);
 164                 bcx
 165             }
 166         }
 167     }
 168
 169     pub fn trans_rvalue_operand(&mut self,
 170                                 bcx: Builder<'a, 'tcx>,
 171                                 rvalue: &mir::Rvalue<'tcx>)
 172                                 -> (Builder<'a, 'tcx>, OperandRef<'tcx>)
 173     {
 174         assert!(rvalue_creates_operand(rvalue), "cannot trans {:?} to operand", rvalue);
 175
 176         match *rvalue {
 177             mir::Rvalue::Cast(ref kind, ref source, cast_ty) => {
 178                 let operand = self.trans_operand(&bcx, source);
 179                 debug!("cast operand is {:?}", operand);
 180                 let cast_ty = self.monomorphize(&cast_ty);
 181
 182                 let val = match *kind {
 183                     mir::CastKind::ReifyFnPointer => {
 184                         match operand.ty.sty {
 185                             ty::TyFnDef(def_id, substs, _) => {
 186                                 OperandValue::Immediate(
 187                                     callee::resolve_and_get_fn(bcx.ccx, def_id, substs))
 188                             }
 189                             _ => {
 190                                 bug!("{} cannot be reified to a fn ptr", operand.ty)
 191                             }
 192                         }
 193                     }
 194                     mir::CastKind::ClosureFnPointer => {
 195                         match operand.ty.sty {
 196                             ty::TyClosure(def_id, substs) => {
 197                                 let instance = monomorphize::resolve_closure(
 198                                     bcx.ccx.shared(), def_id, substs, ty::ClosureKind::FnOnce);
 199                                 OperandValue::Immediate(callee::get_fn(bcx.ccx, instance))
 200                             }
 201                             _ => {
 202                                 bug!("{} cannot be cast to a fn ptr", operand.ty)
 203                             }
 204                         }
 205                     }
 206                     mir::CastKind::UnsafeFnPointer => {
 207                         // this is a no-op at the LLVM level
 208                         operand.val
 209                     }
 210                     mir::CastKind::Unsize => {
 211                         // unsize targets other than to a fat pointer currently
 212                         // can't be operands.
 213                         assert!(common::type_is_fat_ptr(bcx.ccx, cast_ty));
 214
 215                         match operand.val {
 216                             OperandValue::Pair(lldata, llextra) => {
 217                                 // unsize from a fat pointer - this is a
 218                                 // "trait-object-to-supertrait" coercion, for
 219                                 // example,
 220                                 //   &'a fmt::Debug+Send => &'a fmt::Debug,
 221                                 // So we need to pointercast the base to ensure
 222                                 // the types match up.
 223                                 let llcast_ty = type_of::fat_ptr_base_ty(bcx.ccx, cast_ty);
 224                                 let lldata = bcx.pointercast(lldata, llcast_ty);
 225                                 OperandValue::Pair(lldata, llextra)
 226                             }
 227                             OperandValue::Immediate(lldata) => {
 228                                 // "standard" unsize
 229                                 let (lldata, llextra) = base::unsize_thin_ptr(&bcx, lldata,
 230                                     operand.ty, cast_ty);
 231                                 OperandValue::Pair(lldata, llextra)
 232                             }
 233                             OperandValue::Ref(..) => {
 234                                 bug!("by-ref operand {:?} in trans_rvalue_operand",
 235                                      operand);
 236                             }
 237                         }
 238                     }
 239                     mir::CastKind::Misc if common::type_is_fat_ptr(bcx.ccx, operand.ty) => {
 240                         let ll_cast_ty = type_of::immediate_type_of(bcx.ccx, cast_ty);
 241                         let ll_from_ty = type_of::immediate_type_of(bcx.ccx, operand.ty);
 242                         if let OperandValue::Pair(data_ptr, meta_ptr) = operand.val {
 243                             if common::type_is_fat_ptr(bcx.ccx, cast_ty) {
 244                                 let ll_cft = ll_cast_ty.field_types();
 245                                 let ll_fft = ll_from_ty.field_types();
 246                                 let data_cast = bcx.pointercast(data_ptr, ll_cft[0]);
 247                                 assert_eq!(ll_cft[1].kind(), ll_fft[1].kind());
 248                                 OperandValue::Pair(data_cast, meta_ptr)
 249                             } else { // cast to thin-ptr
 250                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 251                                 // pointer-cast of that pointer to desired pointer type.
 252                                 let llval = bcx.pointercast(data_ptr, ll_cast_ty);
 253                                 OperandValue::Immediate(llval)
 254                             }
 255                         } else {
 256                             bug!("Unexpected non-Pair operand")
 257                         }
 258                     }
 259                     mir::CastKind::Misc => {
 260                         debug_assert!(common::type_is_immediate(bcx.ccx, cast_ty));
 261                         let r_t_in = CastTy::from_ty(operand.ty).expect("bad input type for cast");
 262                         let r_t_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
 263                         let ll_t_in = type_of::immediate_type_of(bcx.ccx, operand.ty);
 264                         let ll_t_out = type_of::immediate_type_of(bcx.ccx, cast_ty);
 265                         let llval = operand.immediate();
 266                         let l = bcx.ccx.layout_of(operand.ty);
 267                         let signed = if let Layout::CEnum { signed, min, max, .. } = *l {
 268                             if max > min {
 269                                 // We want `table[e as usize]` to not
 270                                 // have bound checks, and this is the most
 271                                 // convenient place to put the `assume`.
 272
 273                                 base::call_assume(&bcx, bcx.icmp(
 274                                     llvm::IntULE,
 275                                     llval,
 276                                     C_integral(common::val_ty(llval), max, false)
 277                                 ));
 278                             }
 279
 280                             signed
 281                         } else {
 282                             operand.ty.is_signed()
 283                         };
 284
 285                         let newval = match (r_t_in, r_t_out) {
 286                             (CastTy::Int(_), CastTy::Int(_)) => {
 287                                 bcx.intcast(llval, ll_t_out, signed)
 288                             }
 289                             (CastTy::Float, CastTy::Float) => {
 290                                 let srcsz = ll_t_in.float_width();
 291                                 let dstsz = ll_t_out.float_width();
 292                                 if dstsz > srcsz {
 293                                     bcx.fpext(llval, ll_t_out)
 294                                 } else if srcsz > dstsz {
 295                                     bcx.fptrunc(llval, ll_t_out)
 296                                 } else {
 297                                     llval
 298                                 }
 299                             }
 300                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 301                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 302                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 303                                 bcx.pointercast(llval, ll_t_out),
 304                             (CastTy::Ptr(_), CastTy::Int(_)) |
 305                             (CastTy::FnPtr, CastTy::Int(_)) =>
 306                                 bcx.ptrtoint(llval, ll_t_out),
 307                             (CastTy::Int(_), CastTy::Ptr(_)) =>
 308                                 bcx.inttoptr(llval, ll_t_out),
 309                             (CastTy::Int(_), CastTy::Float) if signed =>
 310                                 bcx.sitofp(llval, ll_t_out),
 311                             (CastTy::Int(_), CastTy::Float) =>
 312                                 bcx.uitofp(llval, ll_t_out),
 313                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 314                                 bcx.fptosi(llval, ll_t_out),
 315                             (CastTy::Float, CastTy::Int(_)) =>
 316                                 bcx.fptoui(llval, ll_t_out),
 317                             _ => bug!("unsupported cast: {:?} to {:?}", operand.ty, cast_ty)
 318                         };
 319                         OperandValue::Immediate(newval)
 320                     }
 321                 };
 322                 let operand = OperandRef {
 323                     val: val,
 324                     ty: cast_ty
 325                 };
 326                 (bcx, operand)
 327             }
 328
 329             mir::Rvalue::Ref(_, bk, ref lvalue) => {
 330                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 331
 332                 let ty = tr_lvalue.ty.to_ty(bcx.tcx());
 333                 let ref_ty = bcx.tcx().mk_ref(
 334                     bcx.tcx().mk_region(ty::ReErased),
 335                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() }
 336                 );
 337
 338                 // Note: lvalues are indirect, so storing the `llval` into the
 339                 // destination effectively creates a reference.
 340                 let operand = if bcx.ccx.shared().type_is_sized(ty) {
 341                     OperandRef {
 342                         val: OperandValue::Immediate(tr_lvalue.llval),
 343                         ty: ref_ty,
 344                     }
 345                 } else {
 346                     OperandRef {
 347                         val: OperandValue::Pair(tr_lvalue.llval,
 348                                                 tr_lvalue.llextra),
 349                         ty: ref_ty,
 350                     }
 351                 };
 352                 (bcx, operand)
 353             }
 354
 355             mir::Rvalue::Len(ref lvalue) => {
 356                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 357                 let operand = OperandRef {
 358                     val: OperandValue::Immediate(tr_lvalue.len(bcx.ccx)),
 359                     ty: bcx.tcx().types.usize,
 360                 };
 361                 (bcx, operand)
 362             }
 363
 364             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 365                 let lhs = self.trans_operand(&bcx, lhs);
 366                 let rhs = self.trans_operand(&bcx, rhs);
 367                 let llresult = if common::type_is_fat_ptr(bcx.ccx, lhs.ty) {
 368                     match (lhs.val, rhs.val) {
 369                         (OperandValue::Pair(lhs_addr, lhs_extra),
 370                          OperandValue::Pair(rhs_addr, rhs_extra)) => {
 371                             self.trans_fat_ptr_binop(&bcx, op,
 372                                                      lhs_addr, lhs_extra,
 373                                                      rhs_addr, rhs_extra,
 374                                                      lhs.ty)
 375                         }
 376                         _ => bug!()
 377                     }
 378
 379                 } else {
 380                     self.trans_scalar_binop(&bcx, op,
 381                                             lhs.immediate(), rhs.immediate(),
 382                                             lhs.ty)
 383                 };
 384                 let operand = OperandRef {
 385                     val: OperandValue::Immediate(llresult),
 386                     ty: op.ty(bcx.tcx(), lhs.ty, rhs.ty),
 387                 };
 388                 (bcx, operand)
 389             }
 390             mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
 391                 let lhs = self.trans_operand(&bcx, lhs);
 392                 let rhs = self.trans_operand(&bcx, rhs);
 393                 let result = self.trans_scalar_checked_binop(&bcx, op,
 394                                                              lhs.immediate(), rhs.immediate(),
 395                                                              lhs.ty);
 396                 let val_ty = op.ty(bcx.tcx(), lhs.ty, rhs.ty);
 397                 let operand_ty = bcx.tcx().intern_tup(&[val_ty, bcx.tcx().types.bool], false);
 398                 let operand = OperandRef {
 399                     val: result,
 400                     ty: operand_ty
 401                 };
 402
 403                 (bcx, operand)
 404             }
 405
 406             mir::Rvalue::UnaryOp(op, ref operand) => {
 407                 let operand = self.trans_operand(&bcx, operand);
 408                 let lloperand = operand.immediate();
 409                 let is_float = operand.ty.is_fp();
 410                 let llval = match op {
 411                     mir::UnOp::Not => bcx.not(lloperand),
 412                     mir::UnOp::Neg => if is_float {
 413                         bcx.fneg(lloperand)
 414                     } else {
 415                         bcx.neg(lloperand)
 416                     }
 417                 };
 418                 (bcx, OperandRef {
 419                     val: OperandValue::Immediate(llval),
 420                     ty: operand.ty,
 421                 })
 422             }
 423
 424             mir::Rvalue::Discriminant(ref lvalue) => {
 425                 let discr_lvalue = self.trans_lvalue(&bcx, lvalue);
 426                 let enum_ty = discr_lvalue.ty.to_ty(bcx.tcx());
 427                 let discr_ty = rvalue.ty(&*self.mir, bcx.tcx());
 428                 let discr_type = type_of::immediate_type_of(bcx.ccx, discr_ty);
 429                 let discr = adt::trans_get_discr(&bcx, enum_ty, discr_lvalue.llval,
 430                                                   discr_lvalue.alignment, Some(discr_type), true);
 431                 (bcx, OperandRef {
 432                     val: OperandValue::Immediate(discr),
 433                     ty: discr_ty
 434                 })
 435             }
 436
 437             mir::Rvalue::Box(content_ty) => {
 438                 let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
 439                 let llty = type_of::type_of(bcx.ccx, content_ty);
 440                 let llsize = machine::llsize_of(bcx.ccx, llty);
 441                 let align = bcx.ccx.align_of(content_ty);
 442                 let llalign = C_uint(bcx.ccx, align);
 443                 let llty_ptr = llty.ptr_to();
 444                 let box_ty = bcx.tcx().mk_box(content_ty);
 445
 446                 // Allocate space:
 447                 let def_id = match bcx.tcx().lang_items.require(ExchangeMallocFnLangItem) {
 448                     Ok(id) => id,
 449                     Err(s) => {
 450                         bcx.sess().fatal(&format!("allocation of `{}` {}", box_ty, s));
 451                     }
 452                 };
 453                 let instance = ty::Instance::mono(bcx.tcx(), def_id);
 454                 let r = callee::get_fn(bcx.ccx, instance);
 455                 let val = bcx.pointercast(bcx.call(r, &[llsize, llalign], None), llty_ptr);
 456
 457                 let operand = OperandRef {
 458                     val: OperandValue::Immediate(val),
 459                     ty: box_ty,
 460                 };
 461                 (bcx, operand)
 462             }
 463             mir::Rvalue::Use(ref operand) => {
 464                 let operand = self.trans_operand(&bcx, operand);
 465                 (bcx, operand)
 466             }
 467             mir::Rvalue::Repeat(..) |
 468             mir::Rvalue::Aggregate(..) => {
 469                 bug!("cannot generate operand from rvalue {:?}", rvalue);
 470
 471             }
 472         }
 473     }
 474
 475     pub fn trans_scalar_binop(&mut self,
 476                               bcx: &Builder<'a, 'tcx>,
 477                               op: mir::BinOp,
 478                               lhs: ValueRef,
 479                               rhs: ValueRef,
 480                               input_ty: Ty<'tcx>) -> ValueRef {
 481         let is_float = input_ty.is_fp();
 482         let is_signed = input_ty.is_signed();
 483         let is_nil = input_ty.is_nil();
 484         let is_bool = input_ty.is_bool();
 485         match op {
 486             mir::BinOp::Add => if is_float {
 487                 bcx.fadd(lhs, rhs)
 488             } else {
 489                 bcx.add(lhs, rhs)
 490             },
 491             mir::BinOp::Sub => if is_float {
 492                 bcx.fsub(lhs, rhs)
 493             } else {
 494                 bcx.sub(lhs, rhs)
 495             },
 496             mir::BinOp::Mul => if is_float {
 497                 bcx.fmul(lhs, rhs)
 498             } else {
 499                 bcx.mul(lhs, rhs)
 500             },
 501             mir::BinOp::Div => if is_float {
 502                 bcx.fdiv(lhs, rhs)
 503             } else if is_signed {
 504                 bcx.sdiv(lhs, rhs)
 505             } else {
 506                 bcx.udiv(lhs, rhs)
 507             },
 508             mir::BinOp::Rem => if is_float {
 509                 bcx.frem(lhs, rhs)
 510             } else if is_signed {
 511                 bcx.srem(lhs, rhs)
 512             } else {
 513                 bcx.urem(lhs, rhs)
 514             },
 515             mir::BinOp::BitOr => bcx.or(lhs, rhs),
 516             mir::BinOp::BitAnd => bcx.and(lhs, rhs),
 517             mir::BinOp::BitXor => bcx.xor(lhs, rhs),
 518             mir::BinOp::Shl => common::build_unchecked_lshift(bcx, lhs, rhs),
 519             mir::BinOp::Shr => common::build_unchecked_rshift(bcx, input_ty, lhs, rhs),
 520             mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
 521             mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_nil {
 522                 C_bool(bcx.ccx, match op {
 523                     mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
 524                     mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,
 525                     _ => unreachable!()
 526                 })
 527             } else if is_float {
 528                 bcx.fcmp(
 529                     base::bin_op_to_fcmp_predicate(op.to_hir_binop()),
 530                     lhs, rhs
 531                 )
 532             } else {
 533                 let (lhs, rhs) = if is_bool {
 534                     // FIXME(#36856) -- extend the bools into `i8` because
 535                     // LLVM's i1 comparisons are broken.
 536                     (bcx.zext(lhs, Type::i8(bcx.ccx)),
 537                      bcx.zext(rhs, Type::i8(bcx.ccx)))
 538                 } else {
 539                     (lhs, rhs)
 540                 };
 541
 542                 bcx.icmp(
 543                     base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed),
 544                     lhs, rhs
 545                 )
 546             }
 547         }
 548     }
 549
 550     pub fn trans_fat_ptr_binop(&mut self,
 551                                bcx: &Builder<'a, 'tcx>,
 552                                op: mir::BinOp,
 553                                lhs_addr: ValueRef,
 554                                lhs_extra: ValueRef,
 555                                rhs_addr: ValueRef,
 556                                rhs_extra: ValueRef,
 557                                _input_ty: Ty<'tcx>)
 558                                -> ValueRef {
 559         match op {
 560             mir::BinOp::Eq => {
 561                 bcx.and(
 562                     bcx.icmp(llvm::IntEQ, lhs_addr, rhs_addr),
 563                     bcx.icmp(llvm::IntEQ, lhs_extra, rhs_extra)
 564                 )
 565             }
 566             mir::BinOp::Ne => {
 567                 bcx.or(
 568                     bcx.icmp(llvm::IntNE, lhs_addr, rhs_addr),
 569                     bcx.icmp(llvm::IntNE, lhs_extra, rhs_extra)
 570                 )
 571             }
 572             mir::BinOp::Le | mir::BinOp::Lt |
 573             mir::BinOp::Ge | mir::BinOp::Gt => {
 574                 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
 575                 let (op, strict_op) = match op {
 576                     mir::BinOp::Lt => (llvm::IntULT, llvm::IntULT),
 577                     mir::BinOp::Le => (llvm::IntULE, llvm::IntULT),
 578                     mir::BinOp::Gt => (llvm::IntUGT, llvm::IntUGT),
 579                     mir::BinOp::Ge => (llvm::IntUGE, llvm::IntUGT),
 580                     _ => bug!(),
 581                 };
 582
 583                 bcx.or(
 584                     bcx.icmp(strict_op, lhs_addr, rhs_addr),
 585                     bcx.and(
 586                         bcx.icmp(llvm::IntEQ, lhs_addr, rhs_addr),
 587                         bcx.icmp(op, lhs_extra, rhs_extra)
 588                     )
 589                 )
 590             }
 591             _ => {
 592                 bug!("unexpected fat ptr binop");
 593             }
 594         }
 595     }
 596
 597     pub fn trans_scalar_checked_binop(&mut self,
 598                                       bcx: &Builder<'a, 'tcx>,
 599                                       op: mir::BinOp,
 600                                       lhs: ValueRef,
 601                                       rhs: ValueRef,
 602                                       input_ty: Ty<'tcx>) -> OperandValue {
 603         // This case can currently arise only from functions marked
 604         // with #[rustc_inherit_overflow_checks] and inlined from
 605         // another crate (mostly core::num generic/#[inline] fns),
 606         // while the current crate doesn't use overflow checks.
 607         if !bcx.ccx.check_overflow() {
 608             let val = self.trans_scalar_binop(bcx, op, lhs, rhs, input_ty);
 609             return OperandValue::Pair(val, C_bool(bcx.ccx, false));
 610         }
 611
 612         // First try performing the operation on constants, which
 613         // will only succeed if both operands are constant.
 614         // This is necessary to determine when an overflow Assert
 615         // will always panic at runtime, and produce a warning.
 616         if let Some((val, of)) = const_scalar_checked_binop(bcx.tcx(), op, lhs, rhs, input_ty) {
 617             return OperandValue::Pair(val, C_bool(bcx.ccx, of));
 618         }
 619
 620         let (val, of) = match op {
 621             // These are checked using intrinsics
 622             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 623                 let oop = match op {
 624                     mir::BinOp::Add => OverflowOp::Add,
 625                     mir::BinOp::Sub => OverflowOp::Sub,
 626                     mir::BinOp::Mul => OverflowOp::Mul,
 627                     _ => unreachable!()
 628                 };
 629                 let intrinsic = get_overflow_intrinsic(oop, bcx, input_ty);
 630                 let res = bcx.call(intrinsic, &[lhs, rhs], None);
 631
 632                 (bcx.extract_value(res, 0),
 633                  bcx.extract_value(res, 1))
 634             }
 635             mir::BinOp::Shl | mir::BinOp::Shr => {
 636                 let lhs_llty = val_ty(lhs);
 637                 let rhs_llty = val_ty(rhs);
 638                 let invert_mask = common::shift_mask_val(&bcx, lhs_llty, rhs_llty, true);
 639                 let outer_bits = bcx.and(rhs, invert_mask);
 640
 641                 let of = bcx.icmp(llvm::IntNE, outer_bits, C_null(rhs_llty));
 642                 let val = self.trans_scalar_binop(bcx, op, lhs, rhs, input_ty);
 643
 644                 (val, of)
 645             }
 646             _ => {
 647                 bug!("Operator `{:?}` is not a checkable operator", op)
 648             }
 649         };
 650
 651         OperandValue::Pair(val, of)
 652     }
 653 }
 654
 655 pub fn rvalue_creates_operand(rvalue: &mir::Rvalue) -> bool {
 656     match *rvalue {
 657         mir::Rvalue::Ref(..) |
 658         mir::Rvalue::Len(..) |
 659         mir::Rvalue::Cast(..) | // (*)
 660         mir::Rvalue::BinaryOp(..) |
 661         mir::Rvalue::CheckedBinaryOp(..) |
 662         mir::Rvalue::UnaryOp(..) |
 663         mir::Rvalue::Discriminant(..) |
 664         mir::Rvalue::Box(..) |
 665         mir::Rvalue::Use(..) => // (*)
 666             true,
 667         mir::Rvalue::Repeat(..) |
 668         mir::Rvalue::Aggregate(..) =>
 669             false,
 670     }
 671
 672     // (*) this is only true if the type is suitable
 673 }
 674
 675 #[derive(Copy, Clone)]
 676 enum OverflowOp {
 677     Add, Sub, Mul
 678 }
 679
 680 fn get_overflow_intrinsic(oop: OverflowOp, bcx: &Builder, ty: Ty) -> ValueRef {
 681     use syntax::ast::IntTy::*;
 682     use syntax::ast::UintTy::*;
 683     use rustc::ty::{TyInt, TyUint};
 684
 685     let tcx = bcx.tcx();
 686
 687     let new_sty = match ty.sty {
 688         TyInt(Is) => match &tcx.sess.target.target.target_pointer_width[..] {
 689             "16" => TyInt(I16),
 690             "32" => TyInt(I32),
 691             "64" => TyInt(I64),
 692             _ => panic!("unsupported target word size")
 693         },
 694         TyUint(Us) => match &tcx.sess.target.target.target_pointer_width[..] {
 695             "16" => TyUint(U16),
 696             "32" => TyUint(U32),
 697             "64" => TyUint(U64),
 698             _ => panic!("unsupported target word size")
 699         },
 700         ref t @ TyUint(_) | ref t @ TyInt(_) => t.clone(),
 701         _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
 702     };
 703
 704     let name = match oop {
 705         OverflowOp::Add => match new_sty {
 706             TyInt(I8) => "llvm.sadd.with.overflow.i8",
 707             TyInt(I16) => "llvm.sadd.with.overflow.i16",
 708             TyInt(I32) => "llvm.sadd.with.overflow.i32",
 709             TyInt(I64) => "llvm.sadd.with.overflow.i64",
 710             TyInt(I128) => "llvm.sadd.with.overflow.i128",
 711
 712             TyUint(U8) => "llvm.uadd.with.overflow.i8",
 713             TyUint(U16) => "llvm.uadd.with.overflow.i16",
 714             TyUint(U32) => "llvm.uadd.with.overflow.i32",
 715             TyUint(U64) => "llvm.uadd.with.overflow.i64",
 716             TyUint(U128) => "llvm.uadd.with.overflow.i128",
 717
 718             _ => unreachable!(),
 719         },
 720         OverflowOp::Sub => match new_sty {
 721             TyInt(I8) => "llvm.ssub.with.overflow.i8",
 722             TyInt(I16) => "llvm.ssub.with.overflow.i16",
 723             TyInt(I32) => "llvm.ssub.with.overflow.i32",
 724             TyInt(I64) => "llvm.ssub.with.overflow.i64",
 725             TyInt(I128) => "llvm.ssub.with.overflow.i128",
 726
 727             TyUint(U8) => "llvm.usub.with.overflow.i8",
 728             TyUint(U16) => "llvm.usub.with.overflow.i16",
 729             TyUint(U32) => "llvm.usub.with.overflow.i32",
 730             TyUint(U64) => "llvm.usub.with.overflow.i64",
 731             TyUint(U128) => "llvm.usub.with.overflow.i128",
 732
 733             _ => unreachable!(),
 734         },
 735         OverflowOp::Mul => match new_sty {
 736             TyInt(I8) => "llvm.smul.with.overflow.i8",
 737             TyInt(I16) => "llvm.smul.with.overflow.i16",
 738             TyInt(I32) => "llvm.smul.with.overflow.i32",
 739             TyInt(I64) => "llvm.smul.with.overflow.i64",
 740             TyInt(I128) => "llvm.smul.with.overflow.i128",
 741
 742             TyUint(U8) => "llvm.umul.with.overflow.i8",
 743             TyUint(U16) => "llvm.umul.with.overflow.i16",
 744             TyUint(U32) => "llvm.umul.with.overflow.i32",
 745             TyUint(U64) => "llvm.umul.with.overflow.i64",
 746             TyUint(U128) => "llvm.umul.with.overflow.i128",
 747
 748             _ => unreachable!(),
 749         },
 750     };
 751
 752     bcx.ccx.get_intrinsic(&name)
 753 }