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