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::{self, LayoutOf};
  15 use rustc::mir;
  16 use rustc::middle::lang_items::ExchangeMallocFnLangItem;
  17 use rustc_apfloat::{ieee, Float, Status, Round};
  18 use rustc_const_math::MAX_F32_PLUS_HALF_ULP;
  19 use std::{u128, i128};
  20
  21 use base;
  22 use builder::Builder;
  23 use callee;
  24 use common::{self, val_ty};
  25 use common::{C_bool, C_u8, C_i32, C_u32, C_u64, C_undef, C_null, C_usize, C_uint, C_uint_big};
  26 use consts;
  27 use monomorphize;
  28 use type_::Type;
  29 use type_of::LayoutLlvmExt;
  30 use value::Value;
  31
  32 use super::{FunctionCx, LocalRef};
  33 use super::operand::{OperandRef, OperandValue};
  34 use super::place::PlaceRef;
  35
  36 impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
  37     pub fn trans_rvalue(&mut self,
  38                         bx: Builder<'a, 'tcx>,
  39                         dest: PlaceRef<'tcx>,
  40                         rvalue: &mir::Rvalue<'tcx>)
  41                         -> Builder<'a, 'tcx>
  42     {
  43         debug!("trans_rvalue(dest.llval={:?}, rvalue={:?})",
  44                Value(dest.llval), rvalue);
  45
  46         match *rvalue {
  47            mir::Rvalue::Use(ref operand) => {
  48                let tr_operand = self.trans_operand(&bx, operand);
  49                // FIXME: consider not copying constants through stack. (fixable by translating
  50                // constants into OperandValue::Ref, why don’t we do that yet if we don’t?)
  51                tr_operand.val.store(&bx, dest);
  52                bx
  53            }
  54
  55             mir::Rvalue::Cast(mir::CastKind::Unsize, ref source, _) => {
  56                 // The destination necessarily contains a fat pointer, so if
  57                 // it's a scalar pair, it's a fat pointer or newtype thereof.
  58                 if dest.layout.is_llvm_scalar_pair() {
  59                     // into-coerce of a thin pointer to a fat pointer - just
  60                     // use the operand path.
  61                     let (bx, temp) = self.trans_rvalue_operand(bx, rvalue);
  62                     temp.val.store(&bx, dest);
  63                     return bx;
  64                 }
  65
  66                 // Unsize of a nontrivial struct. I would prefer for
  67                 // this to be eliminated by MIR translation, but
  68                 // `CoerceUnsized` can be passed by a where-clause,
  69                 // so the (generic) MIR may not be able to expand it.
  70                 let operand = self.trans_operand(&bx, source);
  71                 match operand.val {
  72                     OperandValue::Pair(..) |
  73                     OperandValue::Immediate(_) => {
  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 scratch = PlaceRef::alloca(&bx, operand.layout, "__unsize_temp");
  82                         scratch.storage_live(&bx);
  83                         operand.val.store(&bx, scratch);
  84                         base::coerce_unsized_into(&bx, scratch, dest);
  85                         scratch.storage_dead(&bx);
  86                     }
  87                     OperandValue::Ref(llref, align) => {
  88                         let source = PlaceRef::new_sized(llref, operand.layout, align);
  89                         base::coerce_unsized_into(&bx, source, dest);
  90                     }
  91                 }
  92                 bx
  93             }
  94
  95             mir::Rvalue::Repeat(ref elem, count) => {
  96                 let tr_elem = self.trans_operand(&bx, elem);
  97
  98                 // Do not generate the loop for zero-sized elements or empty arrays.
  99                 if dest.layout.is_zst() {
 100                     return bx;
 101                 }
 102
 103                 let start = dest.project_index(&bx, C_usize(bx.cx, 0)).llval;
 104
 105                 if let OperandValue::Immediate(v) = tr_elem.val {
 106                     let align = C_i32(bx.cx, dest.align.abi() as i32);
 107                     let size = C_usize(bx.cx, dest.layout.size.bytes());
 108
 109                     // Use llvm.memset.p0i8.* to initialize all zero arrays
 110                     if common::is_const_integral(v) && common::const_to_uint(v) == 0 {
 111                         let fill = C_u8(bx.cx, 0);
 112                         base::call_memset(&bx, start, fill, size, align, false);
 113                         return bx;
 114                     }
 115
 116                     // Use llvm.memset.p0i8.* to initialize byte arrays
 117                     let v = base::from_immediate(&bx, v);
 118                     if common::val_ty(v) == Type::i8(bx.cx) {
 119                         base::call_memset(&bx, start, v, size, align, false);
 120                         return bx;
 121                     }
 122                 }
 123
 124                 let count = C_usize(bx.cx, count);
 125                 let end = dest.project_index(&bx, count).llval;
 126
 127                 let header_bx = bx.build_sibling_block("repeat_loop_header");
 128                 let body_bx = bx.build_sibling_block("repeat_loop_body");
 129                 let next_bx = bx.build_sibling_block("repeat_loop_next");
 130
 131                 bx.br(header_bx.llbb());
 132                 let current = header_bx.phi(common::val_ty(start), &[start], &[bx.llbb()]);
 133
 134                 let keep_going = header_bx.icmp(llvm::IntNE, current, end);
 135                 header_bx.cond_br(keep_going, body_bx.llbb(), next_bx.llbb());
 136
 137                 tr_elem.val.store(&body_bx,
 138                     PlaceRef::new_sized(current, tr_elem.layout, dest.align));
 139
 140                 let next = body_bx.inbounds_gep(current, &[C_usize(bx.cx, 1)]);
 141                 body_bx.br(header_bx.llbb());
 142                 header_bx.add_incoming_to_phi(current, next, body_bx.llbb());
 143
 144                 next_bx
 145             }
 146
 147             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 148                 let (dest, active_field_index) = match **kind {
 149                     mir::AggregateKind::Adt(adt_def, variant_index, _, active_field_index) => {
 150                         dest.trans_set_discr(&bx, variant_index);
 151                         if adt_def.is_enum() {
 152                             (dest.project_downcast(&bx, variant_index), active_field_index)
 153                         } else {
 154                             (dest, active_field_index)
 155                         }
 156                     }
 157                     _ => (dest, None)
 158                 };
 159                 for (i, operand) in operands.iter().enumerate() {
 160                     let op = self.trans_operand(&bx, operand);
 161                     // Do not generate stores and GEPis for zero-sized fields.
 162                     if !op.layout.is_zst() {
 163                         let field_index = active_field_index.unwrap_or(i);
 164                         op.val.store(&bx, dest.project_field(&bx, field_index));
 165                     }
 166                 }
 167                 bx
 168             }
 169
 170             _ => {
 171                 assert!(self.rvalue_creates_operand(rvalue));
 172                 let (bx, temp) = self.trans_rvalue_operand(bx, rvalue);
 173                 temp.val.store(&bx, dest);
 174                 bx
 175             }
 176         }
 177     }
 178
 179     pub fn trans_rvalue_operand(&mut self,
 180                                 bx: Builder<'a, 'tcx>,
 181                                 rvalue: &mir::Rvalue<'tcx>)
 182                                 -> (Builder<'a, 'tcx>, OperandRef<'tcx>)
 183     {
 184         assert!(self.rvalue_creates_operand(rvalue), "cannot trans {:?} to operand", rvalue);
 185
 186         match *rvalue {
 187             mir::Rvalue::Cast(ref kind, ref source, mir_cast_ty) => {
 188                 let operand = self.trans_operand(&bx, source);
 189                 debug!("cast operand is {:?}", operand);
 190                 let cast = bx.cx.layout_of(self.monomorphize(&mir_cast_ty));
 191
 192                 let val = match *kind {
 193                     mir::CastKind::ReifyFnPointer => {
 194                         match operand.layout.ty.sty {
 195                             ty::TyFnDef(def_id, substs) => {
 196                                 if bx.cx.tcx.has_attr(def_id, "rustc_args_required_const") {
 197                                     bug!("reifying a fn ptr that requires \
 198                                           const arguments");
 199                                 }
 200                                 OperandValue::Immediate(
 201                                     callee::resolve_and_get_fn(bx.cx, def_id, substs))
 202                             }
 203                             _ => {
 204                                 bug!("{} cannot be reified to a fn ptr", operand.layout.ty)
 205                             }
 206                         }
 207                     }
 208                     mir::CastKind::ClosureFnPointer => {
 209                         match operand.layout.ty.sty {
 210                             ty::TyClosure(def_id, substs) => {
 211                                 let instance = monomorphize::resolve_closure(
 212                                     bx.cx.tcx, def_id, substs, ty::ClosureKind::FnOnce);
 213                                 OperandValue::Immediate(callee::get_fn(bx.cx, instance))
 214                             }
 215                             _ => {
 216                                 bug!("{} cannot be cast to a fn ptr", operand.layout.ty)
 217                             }
 218                         }
 219                     }
 220                     mir::CastKind::UnsafeFnPointer => {
 221                         // this is a no-op at the LLVM level
 222                         operand.val
 223                     }
 224                     mir::CastKind::Unsize => {
 225                         assert!(cast.is_llvm_scalar_pair());
 226                         match operand.val {
 227                             OperandValue::Pair(lldata, llextra) => {
 228                                 // unsize from a fat pointer - this is a
 229                                 // "trait-object-to-supertrait" coercion, for
 230                                 // example,
 231                                 //   &'a fmt::Debug+Send => &'a fmt::Debug,
 232
 233                                 // HACK(eddyb) have to bitcast pointers
 234                                 // until LLVM removes pointee types.
 235                                 let lldata = bx.pointercast(lldata,
 236                                     cast.scalar_pair_element_llvm_type(bx.cx, 0));
 237                                 OperandValue::Pair(lldata, llextra)
 238                             }
 239                             OperandValue::Immediate(lldata) => {
 240                                 // "standard" unsize
 241                                 let (lldata, llextra) = base::unsize_thin_ptr(&bx, lldata,
 242                                     operand.layout.ty, cast.ty);
 243                                 OperandValue::Pair(lldata, llextra)
 244                             }
 245                             OperandValue::Ref(..) => {
 246                                 bug!("by-ref operand {:?} in trans_rvalue_operand",
 247                                      operand);
 248                             }
 249                         }
 250                     }
 251                     mir::CastKind::Misc if operand.layout.is_llvm_scalar_pair() => {
 252                         if let OperandValue::Pair(data_ptr, meta) = operand.val {
 253                             if cast.is_llvm_scalar_pair() {
 254                                 let data_cast = bx.pointercast(data_ptr,
 255                                     cast.scalar_pair_element_llvm_type(bx.cx, 0));
 256                                 OperandValue::Pair(data_cast, meta)
 257                             } else { // cast to thin-ptr
 258                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 259                                 // pointer-cast of that pointer to desired pointer type.
 260                                 let llcast_ty = cast.immediate_llvm_type(bx.cx);
 261                                 let llval = bx.pointercast(data_ptr, llcast_ty);
 262                                 OperandValue::Immediate(llval)
 263                             }
 264                         } else {
 265                             bug!("Unexpected non-Pair operand")
 266                         }
 267                     }
 268                     mir::CastKind::Misc => {
 269                         assert!(cast.is_llvm_immediate());
 270                         let ll_t_out = cast.immediate_llvm_type(bx.cx);
 271                         if operand.layout.abi == layout::Abi::Uninhabited {
 272                             return (bx, OperandRef {
 273                                 val: OperandValue::Immediate(C_undef(ll_t_out)),
 274                                 layout: cast,
 275                             });
 276                         }
 277                         let r_t_in = CastTy::from_ty(operand.layout.ty)
 278                             .expect("bad input type for cast");
 279                         let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
 280                         let ll_t_in = operand.layout.immediate_llvm_type(bx.cx);
 281                         match operand.layout.variants {
 282                             layout::Variants::Single { index } => {
 283                                 if let Some(def) = operand.layout.ty.ty_adt_def() {
 284                                     let discr_val = def
 285                                         .discriminant_for_variant(bx.cx.tcx, index)
 286                                         .val;
 287                                     let discr = C_uint_big(ll_t_out, discr_val);
 288                                     return (bx, OperandRef {
 289                                         val: OperandValue::Immediate(discr),
 290                                         layout: cast,
 291                                     });
 292                                 }
 293                             }
 294                             layout::Variants::Tagged { .. } |
 295                             layout::Variants::NicheFilling { .. } => {},
 296                         }
 297                         let llval = operand.immediate();
 298
 299                         let mut signed = false;
 300                         if let layout::Abi::Scalar(ref scalar) = operand.layout.abi {
 301                             if let layout::Int(_, s) = scalar.value {
 302                                 signed = s;
 303
 304                                 if scalar.valid_range.end > scalar.valid_range.start {
 305                                     // We want `table[e as usize]` to not
 306                                     // have bound checks, and this is the most
 307                                     // convenient place to put the `assume`.
 308
 309                                     base::call_assume(&bx, bx.icmp(
 310                                         llvm::IntULE,
 311                                         llval,
 312                                         C_uint_big(ll_t_in, scalar.valid_range.end)
 313                                     ));
 314                                 }
 315                             }
 316                         }
 317
 318                         let newval = match (r_t_in, r_t_out) {
 319                             (CastTy::Int(_), CastTy::Int(_)) => {
 320                                 bx.intcast(llval, ll_t_out, signed)
 321                             }
 322                             (CastTy::Float, CastTy::Float) => {
 323                                 let srcsz = ll_t_in.float_width();
 324                                 let dstsz = ll_t_out.float_width();
 325                                 if dstsz > srcsz {
 326                                     bx.fpext(llval, ll_t_out)
 327                                 } else if srcsz > dstsz {
 328                                     bx.fptrunc(llval, ll_t_out)
 329                                 } else {
 330                                     llval
 331                                 }
 332                             }
 333                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 334                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 335                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 336                                 bx.pointercast(llval, ll_t_out),
 337                             (CastTy::Ptr(_), CastTy::Int(_)) |
 338                             (CastTy::FnPtr, CastTy::Int(_)) =>
 339                                 bx.ptrtoint(llval, ll_t_out),
 340                             (CastTy::Int(_), CastTy::Ptr(_)) => {
 341                                 let usize_llval = bx.intcast(llval, bx.cx.isize_ty, signed);
 342                                 bx.inttoptr(usize_llval, ll_t_out)
 343                             }
 344                             (CastTy::Int(_), CastTy::Float) =>
 345                                 cast_int_to_float(&bx, signed, llval, ll_t_in, ll_t_out),
 346                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 347                                 cast_float_to_int(&bx, true, llval, ll_t_in, ll_t_out),
 348                             (CastTy::Float, CastTy::Int(_)) =>
 349                                 cast_float_to_int(&bx, false, llval, ll_t_in, ll_t_out),
 350                             _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty)
 351                         };
 352                         OperandValue::Immediate(newval)
 353                     }
 354                 };
 355                 (bx, OperandRef {
 356                     val,
 357                     layout: cast
 358                 })
 359             }
 360
 361             mir::Rvalue::Ref(_, bk, ref place) => {
 362                 let tr_place = self.trans_place(&bx, place);
 363
 364                 let ty = tr_place.layout.ty;
 365
 366                 // Note: places are indirect, so storing the `llval` into the
 367                 // destination effectively creates a reference.
 368                 let val = if !bx.cx.type_has_metadata(ty) {
 369                     OperandValue::Immediate(tr_place.llval)
 370                 } else {
 371                     OperandValue::Pair(tr_place.llval, tr_place.llextra)
 372                 };
 373                 (bx, OperandRef {
 374                     val,
 375                     layout: self.cx.layout_of(self.cx.tcx.mk_ref(
 376                         self.cx.tcx.types.re_erased,
 377                         ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
 378                     )),
 379                 })
 380             }
 381
 382             mir::Rvalue::Len(ref place) => {
 383                 let size = self.evaluate_array_len(&bx, place);
 384                 let operand = OperandRef {
 385                     val: OperandValue::Immediate(size),
 386                     layout: bx.cx.layout_of(bx.tcx().types.usize),
 387                 };
 388                 (bx, operand)
 389             }
 390
 391             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 392                 let lhs = self.trans_operand(&bx, lhs);
 393                 let rhs = self.trans_operand(&bx, rhs);
 394                 let llresult = match (lhs.val, rhs.val) {
 395                     (OperandValue::Pair(lhs_addr, lhs_extra),
 396                      OperandValue::Pair(rhs_addr, rhs_extra)) => {
 397                         self.trans_fat_ptr_binop(&bx, op,
 398                                                  lhs_addr, lhs_extra,
 399                                                  rhs_addr, rhs_extra,
 400                                                  lhs.layout.ty)
 401                     }
 402
 403                     (OperandValue::Immediate(lhs_val),
 404                      OperandValue::Immediate(rhs_val)) => {
 405                         self.trans_scalar_binop(&bx, op, lhs_val, rhs_val, lhs.layout.ty)
 406                     }
 407
 408                     _ => bug!()
 409                 };
 410                 let operand = OperandRef {
 411                     val: OperandValue::Immediate(llresult),
 412                     layout: bx.cx.layout_of(
 413                         op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
 414                 };
 415                 (bx, operand)
 416             }
 417             mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
 418                 let lhs = self.trans_operand(&bx, lhs);
 419                 let rhs = self.trans_operand(&bx, rhs);
 420                 let result = self.trans_scalar_checked_binop(&bx, op,
 421                                                              lhs.immediate(), rhs.immediate(),
 422                                                              lhs.layout.ty);
 423                 let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
 424                 let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
 425                 let operand = OperandRef {
 426                     val: result,
 427                     layout: bx.cx.layout_of(operand_ty)
 428                 };
 429
 430                 (bx, operand)
 431             }
 432
 433             mir::Rvalue::UnaryOp(op, ref operand) => {
 434                 let operand = self.trans_operand(&bx, operand);
 435                 let lloperand = operand.immediate();
 436                 let is_float = operand.layout.ty.is_fp();
 437                 let llval = match op {
 438                     mir::UnOp::Not => bx.not(lloperand),
 439                     mir::UnOp::Neg => if is_float {
 440                         bx.fneg(lloperand)
 441                     } else {
 442                         bx.neg(lloperand)
 443                     }
 444                 };
 445                 (bx, OperandRef {
 446                     val: OperandValue::Immediate(llval),
 447                     layout: operand.layout,
 448                 })
 449             }
 450
 451             mir::Rvalue::Discriminant(ref place) => {
 452                 let discr_ty = rvalue.ty(&*self.mir, bx.tcx());
 453                 let discr =  self.trans_place(&bx, place)
 454                     .trans_get_discr(&bx, discr_ty);
 455                 (bx, OperandRef {
 456                     val: OperandValue::Immediate(discr),
 457                     layout: self.cx.layout_of(discr_ty)
 458                 })
 459             }
 460
 461             mir::Rvalue::NullaryOp(mir::NullOp::SizeOf, ty) => {
 462                 assert!(bx.cx.type_is_sized(ty));
 463                 let val = C_usize(bx.cx, bx.cx.size_of(ty).bytes());
 464                 let tcx = bx.tcx();
 465                 (bx, OperandRef {
 466                     val: OperandValue::Immediate(val),
 467                     layout: self.cx.layout_of(tcx.types.usize),
 468                 })
 469             }
 470
 471             mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
 472                 let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
 473                 let (size, align) = bx.cx.size_and_align_of(content_ty);
 474                 let llsize = C_usize(bx.cx, size.bytes());
 475                 let llalign = C_usize(bx.cx, align.abi());
 476                 let box_layout = bx.cx.layout_of(bx.tcx().mk_box(content_ty));
 477                 let llty_ptr = box_layout.llvm_type(bx.cx);
 478
 479                 // Allocate space:
 480                 let def_id = match bx.tcx().lang_items().require(ExchangeMallocFnLangItem) {
 481                     Ok(id) => id,
 482                     Err(s) => {
 483                         bx.sess().fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 484                     }
 485                 };
 486                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 487                 let r = callee::get_fn(bx.cx, instance);
 488                 let val = bx.pointercast(bx.call(r, &[llsize, llalign], None), llty_ptr);
 489
 490                 let operand = OperandRef {
 491                     val: OperandValue::Immediate(val),
 492                     layout: box_layout,
 493                 };
 494                 (bx, operand)
 495             }
 496             mir::Rvalue::Use(ref operand) => {
 497                 let operand = self.trans_operand(&bx, operand);
 498                 (bx, operand)
 499             }
 500             mir::Rvalue::Repeat(..) |
 501             mir::Rvalue::Aggregate(..) => {
 502                 // According to `rvalue_creates_operand`, only ZST
 503                 // aggregate rvalues are allowed to be operands.
 504                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 505                 (bx, OperandRef::new_zst(self.cx,
 506                     self.cx.layout_of(self.monomorphize(&ty))))
 507             }
 508         }
 509     }
 510
 511     fn evaluate_array_len(&mut self,
 512                           bx: &Builder<'a, 'tcx>,
 513                           place: &mir::Place<'tcx>) -> ValueRef
 514     {
 515         // ZST are passed as operands and require special handling
 516         // because trans_place() panics if Local is operand.
 517         if let mir::Place::Local(index) = *place {
 518             if let LocalRef::Operand(Some(op)) = self.locals[index] {
 519                 if let ty::TyArray(_, n) = op.layout.ty.sty {
 520                     let n = n.val.unwrap_u64();
 521                     return common::C_usize(bx.cx, n);
 522                 }
 523             }
 524         }
 525         // use common size calculation for non zero-sized types
 526         let tr_value = self.trans_place(&bx, place);
 527         return tr_value.len(bx.cx);
 528     }
 529
 530     pub fn trans_scalar_binop(&mut self,
 531                               bx: &Builder<'a, 'tcx>,
 532                               op: mir::BinOp,
 533                               lhs: ValueRef,
 534                               rhs: ValueRef,
 535                               input_ty: Ty<'tcx>) -> ValueRef {
 536         let is_float = input_ty.is_fp();
 537         let is_signed = input_ty.is_signed();
 538         let is_nil = input_ty.is_nil();
 539         match op {
 540             mir::BinOp::Add => if is_float {
 541                 bx.fadd(lhs, rhs)
 542             } else {
 543                 bx.add(lhs, rhs)
 544             },
 545             mir::BinOp::Sub => if is_float {
 546                 bx.fsub(lhs, rhs)
 547             } else {
 548                 bx.sub(lhs, rhs)
 549             },
 550             mir::BinOp::Mul => if is_float {
 551                 bx.fmul(lhs, rhs)
 552             } else {
 553                 bx.mul(lhs, rhs)
 554             },
 555             mir::BinOp::Div => if is_float {
 556                 bx.fdiv(lhs, rhs)
 557             } else if is_signed {
 558                 bx.sdiv(lhs, rhs)
 559             } else {
 560                 bx.udiv(lhs, rhs)
 561             },
 562             mir::BinOp::Rem => if is_float {
 563                 bx.frem(lhs, rhs)
 564             } else if is_signed {
 565                 bx.srem(lhs, rhs)
 566             } else {
 567                 bx.urem(lhs, rhs)
 568             },
 569             mir::BinOp::BitOr => bx.or(lhs, rhs),
 570             mir::BinOp::BitAnd => bx.and(lhs, rhs),
 571             mir::BinOp::BitXor => bx.xor(lhs, rhs),
 572             mir::BinOp::Offset => bx.inbounds_gep(lhs, &[rhs]),
 573             mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
 574             mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
 575             mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
 576             mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_nil {
 577                 C_bool(bx.cx, match op {
 578                     mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
 579                     mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,
 580                     _ => unreachable!()
 581                 })
 582             } else if is_float {
 583                 bx.fcmp(
 584                     base::bin_op_to_fcmp_predicate(op.to_hir_binop()),
 585                     lhs, rhs
 586                 )
 587             } else {
 588                 bx.icmp(
 589                     base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed),
 590                     lhs, rhs
 591                 )
 592             }
 593         }
 594     }
 595
 596     pub fn trans_fat_ptr_binop(&mut self,
 597                                bx: &Builder<'a, 'tcx>,
 598                                op: mir::BinOp,
 599                                lhs_addr: ValueRef,
 600                                lhs_extra: ValueRef,
 601                                rhs_addr: ValueRef,
 602                                rhs_extra: ValueRef,
 603                                _input_ty: Ty<'tcx>)
 604                                -> ValueRef {
 605         match op {
 606             mir::BinOp::Eq => {
 607                 bx.and(
 608                     bx.icmp(llvm::IntEQ, lhs_addr, rhs_addr),
 609                     bx.icmp(llvm::IntEQ, lhs_extra, rhs_extra)
 610                 )
 611             }
 612             mir::BinOp::Ne => {
 613                 bx.or(
 614                     bx.icmp(llvm::IntNE, lhs_addr, rhs_addr),
 615                     bx.icmp(llvm::IntNE, lhs_extra, rhs_extra)
 616                 )
 617             }
 618             mir::BinOp::Le | mir::BinOp::Lt |
 619             mir::BinOp::Ge | mir::BinOp::Gt => {
 620                 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
 621                 let (op, strict_op) = match op {
 622                     mir::BinOp::Lt => (llvm::IntULT, llvm::IntULT),
 623                     mir::BinOp::Le => (llvm::IntULE, llvm::IntULT),
 624                     mir::BinOp::Gt => (llvm::IntUGT, llvm::IntUGT),
 625                     mir::BinOp::Ge => (llvm::IntUGE, llvm::IntUGT),
 626                     _ => bug!(),
 627                 };
 628
 629                 bx.or(
 630                     bx.icmp(strict_op, lhs_addr, rhs_addr),
 631                     bx.and(
 632                         bx.icmp(llvm::IntEQ, lhs_addr, rhs_addr),
 633                         bx.icmp(op, lhs_extra, rhs_extra)
 634                     )
 635                 )
 636             }
 637             _ => {
 638                 bug!("unexpected fat ptr binop");
 639             }
 640         }
 641     }
 642
 643     pub fn trans_scalar_checked_binop(&mut self,
 644                                       bx: &Builder<'a, 'tcx>,
 645                                       op: mir::BinOp,
 646                                       lhs: ValueRef,
 647                                       rhs: ValueRef,
 648                                       input_ty: Ty<'tcx>) -> OperandValue {
 649         // This case can currently arise only from functions marked
 650         // with #[rustc_inherit_overflow_checks] and inlined from
 651         // another crate (mostly core::num generic/#[inline] fns),
 652         // while the current crate doesn't use overflow checks.
 653         if !bx.cx.check_overflow {
 654             let val = self.trans_scalar_binop(bx, op, lhs, rhs, input_ty);
 655             return OperandValue::Pair(val, C_bool(bx.cx, false));
 656         }
 657
 658         let (val, of) = match op {
 659             // These are checked using intrinsics
 660             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 661                 let oop = match op {
 662                     mir::BinOp::Add => OverflowOp::Add,
 663                     mir::BinOp::Sub => OverflowOp::Sub,
 664                     mir::BinOp::Mul => OverflowOp::Mul,
 665                     _ => unreachable!()
 666                 };
 667                 let intrinsic = get_overflow_intrinsic(oop, bx, input_ty);
 668                 let res = bx.call(intrinsic, &[lhs, rhs], None);
 669
 670                 (bx.extract_value(res, 0),
 671                  bx.extract_value(res, 1))
 672             }
 673             mir::BinOp::Shl | mir::BinOp::Shr => {
 674                 let lhs_llty = val_ty(lhs);
 675                 let rhs_llty = val_ty(rhs);
 676                 let invert_mask = common::shift_mask_val(&bx, lhs_llty, rhs_llty, true);
 677                 let outer_bits = bx.and(rhs, invert_mask);
 678
 679                 let of = bx.icmp(llvm::IntNE, outer_bits, C_null(rhs_llty));
 680                 let val = self.trans_scalar_binop(bx, op, lhs, rhs, input_ty);
 681
 682                 (val, of)
 683             }
 684             _ => {
 685                 bug!("Operator `{:?}` is not a checkable operator", op)
 686             }
 687         };
 688
 689         OperandValue::Pair(val, of)
 690     }
 691
 692     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>) -> bool {
 693         match *rvalue {
 694             mir::Rvalue::Ref(..) |
 695             mir::Rvalue::Len(..) |
 696             mir::Rvalue::Cast(..) | // (*)
 697             mir::Rvalue::BinaryOp(..) |
 698             mir::Rvalue::CheckedBinaryOp(..) |
 699             mir::Rvalue::UnaryOp(..) |
 700             mir::Rvalue::Discriminant(..) |
 701             mir::Rvalue::NullaryOp(..) |
 702             mir::Rvalue::Use(..) => // (*)
 703                 true,
 704             mir::Rvalue::Repeat(..) |
 705             mir::Rvalue::Aggregate(..) => {
 706                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 707                 let ty = self.monomorphize(&ty);
 708                 self.cx.layout_of(ty).is_zst()
 709             }
 710         }
 711
 712         // (*) this is only true if the type is suitable
 713     }
 714 }
 715
 716 #[derive(Copy, Clone)]
 717 enum OverflowOp {
 718     Add, Sub, Mul
 719 }
 720
 721 fn get_overflow_intrinsic(oop: OverflowOp, bx: &Builder, ty: Ty) -> ValueRef {
 722     use syntax::ast::IntTy::*;
 723     use syntax::ast::UintTy::*;
 724     use rustc::ty::{TyInt, TyUint};
 725
 726     let tcx = bx.tcx();
 727
 728     let new_sty = match ty.sty {
 729         TyInt(Isize) => match &tcx.sess.target.target.target_pointer_width[..] {
 730             "16" => TyInt(I16),
 731             "32" => TyInt(I32),
 732             "64" => TyInt(I64),
 733             _ => panic!("unsupported target word size")
 734         },
 735         TyUint(Usize) => match &tcx.sess.target.target.target_pointer_width[..] {
 736             "16" => TyUint(U16),
 737             "32" => TyUint(U32),
 738             "64" => TyUint(U64),
 739             _ => panic!("unsupported target word size")
 740         },
 741         ref t @ TyUint(_) | ref t @ TyInt(_) => t.clone(),
 742         _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
 743     };
 744
 745     let name = match oop {
 746         OverflowOp::Add => match new_sty {
 747             TyInt(I8) => "llvm.sadd.with.overflow.i8",
 748             TyInt(I16) => "llvm.sadd.with.overflow.i16",
 749             TyInt(I32) => "llvm.sadd.with.overflow.i32",
 750             TyInt(I64) => "llvm.sadd.with.overflow.i64",
 751             TyInt(I128) => "llvm.sadd.with.overflow.i128",
 752
 753             TyUint(U8) => "llvm.uadd.with.overflow.i8",
 754             TyUint(U16) => "llvm.uadd.with.overflow.i16",
 755             TyUint(U32) => "llvm.uadd.with.overflow.i32",
 756             TyUint(U64) => "llvm.uadd.with.overflow.i64",
 757             TyUint(U128) => "llvm.uadd.with.overflow.i128",
 758
 759             _ => unreachable!(),
 760         },
 761         OverflowOp::Sub => match new_sty {
 762             TyInt(I8) => "llvm.ssub.with.overflow.i8",
 763             TyInt(I16) => "llvm.ssub.with.overflow.i16",
 764             TyInt(I32) => "llvm.ssub.with.overflow.i32",
 765             TyInt(I64) => "llvm.ssub.with.overflow.i64",
 766             TyInt(I128) => "llvm.ssub.with.overflow.i128",
 767
 768             TyUint(U8) => "llvm.usub.with.overflow.i8",
 769             TyUint(U16) => "llvm.usub.with.overflow.i16",
 770             TyUint(U32) => "llvm.usub.with.overflow.i32",
 771             TyUint(U64) => "llvm.usub.with.overflow.i64",
 772             TyUint(U128) => "llvm.usub.with.overflow.i128",
 773
 774             _ => unreachable!(),
 775         },
 776         OverflowOp::Mul => match new_sty {
 777             TyInt(I8) => "llvm.smul.with.overflow.i8",
 778             TyInt(I16) => "llvm.smul.with.overflow.i16",
 779             TyInt(I32) => "llvm.smul.with.overflow.i32",
 780             TyInt(I64) => "llvm.smul.with.overflow.i64",
 781             TyInt(I128) => "llvm.smul.with.overflow.i128",
 782
 783             TyUint(U8) => "llvm.umul.with.overflow.i8",
 784             TyUint(U16) => "llvm.umul.with.overflow.i16",
 785             TyUint(U32) => "llvm.umul.with.overflow.i32",
 786             TyUint(U64) => "llvm.umul.with.overflow.i64",
 787             TyUint(U128) => "llvm.umul.with.overflow.i128",
 788
 789             _ => unreachable!(),
 790         },
 791     };
 792
 793     bx.cx.get_intrinsic(&name)
 794 }
 795
 796 fn cast_int_to_float(bx: &Builder,
 797                      signed: bool,
 798                      x: ValueRef,
 799                      int_ty: Type,
 800                      float_ty: Type) -> ValueRef {
 801     // Most integer types, even i128, fit into [-f32::MAX, f32::MAX] after rounding.
 802     // It's only u128 -> f32 that can cause overflows (i.e., should yield infinity).
 803     // LLVM's uitofp produces undef in those cases, so we manually check for that case.
 804     let is_u128_to_f32 = !signed && int_ty.int_width() == 128 && float_ty.float_width() == 32;
 805     if is_u128_to_f32 {
 806         // All inputs greater or equal to (f32::MAX + 0.5 ULP) are rounded to infinity,
 807         // and for everything else LLVM's uitofp works just fine.
 808         let max = C_uint_big(int_ty, MAX_F32_PLUS_HALF_ULP);
 809         let overflow = bx.icmp(llvm::IntUGE, x, max);
 810         let infinity_bits = C_u32(bx.cx, ieee::Single::INFINITY.to_bits() as u32);
 811         let infinity = consts::bitcast(infinity_bits, float_ty);
 812         bx.select(overflow, infinity, bx.uitofp(x, float_ty))
 813     } else {
 814         if signed {
 815             bx.sitofp(x, float_ty)
 816         } else {
 817             bx.uitofp(x, float_ty)
 818         }
 819     }
 820 }
 821
 822 fn cast_float_to_int(bx: &Builder,
 823                      signed: bool,
 824                      x: ValueRef,
 825                      float_ty: Type,
 826                      int_ty: Type) -> ValueRef {
 827     let fptosui_result = if signed {
 828         bx.fptosi(x, int_ty)
 829     } else {
 830         bx.fptoui(x, int_ty)
 831     };
 832
 833     if !bx.sess().opts.debugging_opts.saturating_float_casts {
 834         return fptosui_result;
 835     }
 836     // LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the
 837     // destination integer type after rounding towards zero. This `undef` value can cause UB in
 838     // safe code (see issue #10184), so we implement a saturating conversion on top of it:
 839     // Semantically, the mathematical value of the input is rounded towards zero to the next
 840     // mathematical integer, and then the result is clamped into the range of the destination
 841     // integer type. Positive and negative infinity are mapped to the maximum and minimum value of
 842     // the destination integer type. NaN is mapped to 0.
 843     //
 844     // Define f_min and f_max as the largest and smallest (finite) floats that are exactly equal to
 845     // a value representable in int_ty.
 846     // They are exactly equal to int_ty::{MIN,MAX} if float_ty has enough significand bits.
 847     // Otherwise, int_ty::MAX must be rounded towards zero, as it is one less than a power of two.
 848     // int_ty::MIN, however, is either zero or a negative power of two and is thus exactly
 849     // representable. Note that this only works if float_ty's exponent range is sufficiently large.
 850     // f16 or 256 bit integers would break this property. Right now the smallest float type is f32
 851     // with exponents ranging up to 127, which is barely enough for i128::MIN = -2^127.
 852     // On the other hand, f_max works even if int_ty::MAX is greater than float_ty::MAX. Because
 853     // we're rounding towards zero, we just get float_ty::MAX (which is always an integer).
 854     // This already happens today with u128::MAX = 2^128 - 1 > f32::MAX.
 855     fn compute_clamp_bounds<F: Float>(signed: bool, int_ty: Type) -> (u128, u128) {
 856         let rounded_min = F::from_i128_r(int_min(signed, int_ty), Round::TowardZero);
 857         assert_eq!(rounded_min.status, Status::OK);
 858         let rounded_max = F::from_u128_r(int_max(signed, int_ty), Round::TowardZero);
 859         assert!(rounded_max.value.is_finite());
 860         (rounded_min.value.to_bits(), rounded_max.value.to_bits())
 861     }
 862     fn int_max(signed: bool, int_ty: Type) -> u128 {
 863         let shift_amount = 128 - int_ty.int_width();
 864         if signed {
 865             i128::MAX as u128 >> shift_amount
 866         } else {
 867             u128::MAX >> shift_amount
 868         }
 869     }
 870     fn int_min(signed: bool, int_ty: Type) -> i128 {
 871         if signed {
 872             i128::MIN >> (128 - int_ty.int_width())
 873         } else {
 874             0
 875         }
 876     }
 877     let float_bits_to_llval = |bits| {
 878         let bits_llval = match float_ty.float_width() {
 879             32 => C_u32(bx.cx, bits as u32),
 880             64 => C_u64(bx.cx, bits as u64),
 881             n => bug!("unsupported float width {}", n),
 882         };
 883         consts::bitcast(bits_llval, float_ty)
 884     };
 885     let (f_min, f_max) = match float_ty.float_width() {
 886         32 => compute_clamp_bounds::<ieee::Single>(signed, int_ty),
 887         64 => compute_clamp_bounds::<ieee::Double>(signed, int_ty),
 888         n => bug!("unsupported float width {}", n),
 889     };
 890     let f_min = float_bits_to_llval(f_min);
 891     let f_max = float_bits_to_llval(f_max);
 892     // To implement saturation, we perform the following steps:
 893     //
 894     // 1. Cast x to an integer with fpto[su]i. This may result in undef.
 895     // 2. Compare x to f_min and f_max, and use the comparison results to select:
 896     //  a) int_ty::MIN if x < f_min or x is NaN
 897     //  b) int_ty::MAX if x > f_max
 898     //  c) the result of fpto[su]i otherwise
 899     // 3. If x is NaN, return 0.0, otherwise return the result of step 2.
 900     //
 901     // This avoids resulting undef because values in range [f_min, f_max] by definition fit into the
 902     // destination type. It creates an undef temporary, but *producing* undef is not UB. Our use of
 903     // undef does not introduce any non-determinism either.
 904     // More importantly, the above procedure correctly implements saturating conversion.
 905     // Proof (sketch):
 906     // If x is NaN, 0 is returned by definition.
 907     // Otherwise, x is finite or infinite and thus can be compared with f_min and f_max.
 908     // This yields three cases to consider:
 909     // (1) if x in [f_min, f_max], the result of fpto[su]i is returned, which agrees with
 910     //     saturating conversion for inputs in that range.
 911     // (2) if x > f_max, then x is larger than int_ty::MAX. This holds even if f_max is rounded
 912     //     (i.e., if f_max < int_ty::MAX) because in those cases, nextUp(f_max) is already larger
 913     //     than int_ty::MAX. Because x is larger than int_ty::MAX, the return value of int_ty::MAX
 914     //     is correct.
 915     // (3) if x < f_min, then x is smaller than int_ty::MIN. As shown earlier, f_min exactly equals
 916     //     int_ty::MIN and therefore the return value of int_ty::MIN is correct.
 917     // QED.
 918
 919     // Step 1 was already performed above.
 920
 921     // Step 2: We use two comparisons and two selects, with %s1 being the result:
 922     //     %less_or_nan = fcmp ult %x, %f_min
 923     //     %greater = fcmp olt %x, %f_max
 924     //     %s0 = select %less_or_nan, int_ty::MIN, %fptosi_result
 925     //     %s1 = select %greater, int_ty::MAX, %s0
 926     // Note that %less_or_nan uses an *unordered* comparison. This comparison is true if the
 927     // operands are not comparable (i.e., if x is NaN). The unordered comparison ensures that s1
 928     // becomes int_ty::MIN if x is NaN.
 929     // Performance note: Unordered comparison can be lowered to a "flipped" comparison and a
 930     // negation, and the negation can be merged into the select. Therefore, it not necessarily any
 931     // more expensive than a ordered ("normal") comparison. Whether these optimizations will be
 932     // performed is ultimately up to the backend, but at least x86 does perform them.
 933     let less_or_nan = bx.fcmp(llvm::RealULT, x, f_min);
 934     let greater = bx.fcmp(llvm::RealOGT, x, f_max);
 935     let int_max = C_uint_big(int_ty, int_max(signed, int_ty));
 936     let int_min = C_uint_big(int_ty, int_min(signed, int_ty) as u128);
 937     let s0 = bx.select(less_or_nan, int_min, fptosui_result);
 938     let s1 = bx.select(greater, int_max, s0);
 939
 940     // Step 3: NaN replacement.
 941     // For unsigned types, the above step already yielded int_ty::MIN == 0 if x is NaN.
 942     // Therefore we only need to execute this step for signed integer types.
 943     if signed {
 944         // LLVM has no isNaN predicate, so we use (x == x) instead
 945         bx.select(bx.fcmp(llvm::RealOEQ, x, x), s1, C_uint(int_ty, 0))
 946     } else {
 947         s1
 948     }
 949 }