src/librustc_codegen_llvm/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 rustc::ty::{self, Ty};
  12 use rustc::ty::cast::{CastTy, IntTy};
  13 use rustc::ty::layout::{self, LayoutOf};
  14 use rustc::mir;
  15 use rustc::middle::lang_items::ExchangeMallocFnLangItem;
  16 use rustc_apfloat::{ieee, Float, Status, Round};
  17 use std::{u128, i128};
  18
  19 use base;
  20 use builder::Builder;
  21 use callee;
  22 use common::{self, val_ty};
  23 use common::{C_bool, C_u8, C_i32, C_u32, C_u64, C_undef, C_null, C_usize, C_uint, C_uint_big};
  24 use consts;
  25 use monomorphize;
  26 use type_::Type;
  27 use type_of::LayoutLlvmExt;
  28 use value::Value;
  29
  30 use traits::{IntPredicate, RealPredicate, BuilderMethods};
  31
  32 use super::{FunctionCx, LocalRef};
  33 use super::operand::{OperandRef, OperandValue};
  34 use super::place::PlaceRef;
  35
  36 impl FunctionCx<'a, 'll, 'tcx, &'ll Value> {
  37     pub fn codegen_rvalue(&mut self,
  38                         bx: Builder<'a, 'll, 'tcx>,
  39                         dest: PlaceRef<'tcx, &'ll Value>,
  40                         rvalue: &mir::Rvalue<'tcx>)
  41                         -> Builder<'a, 'll, 'tcx>
  42     {
  43         debug!("codegen_rvalue(dest.llval={:?}, rvalue={:?})",
  44                dest.llval, rvalue);
  45
  46         match *rvalue {
  47            mir::Rvalue::Use(ref operand) => {
  48                let cg_operand = self.codegen_operand(&bx, operand);
  49                // FIXME: consider not copying constants through stack. (fixable by codegenning
  50                // constants into OperandValue::Ref, why don’t we do that yet if we don’t?)
  51                cg_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.codegen_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 building, 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.codegen_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!("codegen_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, None, align) => {
  88                         let source = PlaceRef::new_sized(llref, operand.layout, align);
  89                         base::coerce_unsized_into(&bx, source, dest);
  90                     }
  91                     OperandValue::Ref(_, Some(_), _) => {
  92                         bug!("unsized coercion on an unsized rvalue")
  93                     }
  94                 }
  95                 bx
  96             }
  97
  98             mir::Rvalue::Repeat(ref elem, count) => {
  99                 let cg_elem = self.codegen_operand(&bx, elem);
 100
 101                 // Do not generate the loop for zero-sized elements or empty arrays.
 102                 if dest.layout.is_zst() {
 103                     return bx;
 104                 }
 105
 106                 let start = dest.project_index(&bx, C_usize(bx.cx, 0)).llval;
 107
 108                 if let OperandValue::Immediate(v) = cg_elem.val {
 109                     let align = C_i32(bx.cx, dest.align.abi() as i32);
 110                     let size = C_usize(bx.cx, dest.layout.size.bytes());
 111
 112                     // Use llvm.memset.p0i8.* to initialize all zero arrays
 113                     if common::is_const_integral(v) && common::const_to_uint(v) == 0 {
 114                         let fill = C_u8(bx.cx, 0);
 115                         base::call_memset(&bx, start, fill, size, align, false);
 116                         return bx;
 117                     }
 118
 119                     // Use llvm.memset.p0i8.* to initialize byte arrays
 120                     let v = base::from_immediate(&bx, v);
 121                     if common::val_ty(v) == Type::i8(bx.cx) {
 122                         base::call_memset(&bx, start, v, size, align, false);
 123                         return bx;
 124                     }
 125                 }
 126
 127                 let count = C_usize(bx.cx, count);
 128                 let end = dest.project_index(&bx, count).llval;
 129
 130                 let header_bx = bx.build_sibling_block("repeat_loop_header");
 131                 let body_bx = bx.build_sibling_block("repeat_loop_body");
 132                 let next_bx = bx.build_sibling_block("repeat_loop_next");
 133
 134                 bx.br(header_bx.llbb());
 135                 let current = header_bx.phi(common::val_ty(start), &[start], &[bx.llbb()]);
 136
 137                 let keep_going = header_bx.icmp(IntPredicate::IntNE, current, end);
 138                 header_bx.cond_br(keep_going, body_bx.llbb(), next_bx.llbb());
 139
 140                 cg_elem.val.store(&body_bx,
 141                     PlaceRef::new_sized(current, cg_elem.layout, dest.align));
 142
 143                 let next = body_bx.inbounds_gep(current, &[C_usize(bx.cx, 1)]);
 144                 body_bx.br(header_bx.llbb());
 145                 header_bx.add_incoming_to_phi(current, next, body_bx.llbb());
 146
 147                 next_bx
 148             }
 149
 150             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 151                 let (dest, active_field_index) = match **kind {
 152                     mir::AggregateKind::Adt(adt_def, variant_index, _, _, active_field_index) => {
 153                         dest.codegen_set_discr(&bx, variant_index);
 154                         if adt_def.is_enum() {
 155                             (dest.project_downcast(&bx, variant_index), active_field_index)
 156                         } else {
 157                             (dest, active_field_index)
 158                         }
 159                     }
 160                     _ => (dest, None)
 161                 };
 162                 for (i, operand) in operands.iter().enumerate() {
 163                     let op = self.codegen_operand(&bx, operand);
 164                     // Do not generate stores and GEPis for zero-sized fields.
 165                     if !op.layout.is_zst() {
 166                         let field_index = active_field_index.unwrap_or(i);
 167                         op.val.store(&bx, dest.project_field(&bx, field_index));
 168                     }
 169                 }
 170                 bx
 171             }
 172
 173             _ => {
 174                 assert!(self.rvalue_creates_operand(rvalue));
 175                 let (bx, temp) = self.codegen_rvalue_operand(bx, rvalue);
 176                 temp.val.store(&bx, dest);
 177                 bx
 178             }
 179         }
 180     }
 181
 182     pub fn codegen_rvalue_unsized(&mut self,
 183                         bx: Builder<'a, 'll, 'tcx, &'ll Value>,
 184                         indirect_dest: PlaceRef<'tcx, &'ll Value>,
 185                         rvalue: &mir::Rvalue<'tcx>)
 186                         -> Builder<'a, 'll, 'tcx, &'ll Value>
 187     {
 188         debug!("codegen_rvalue_unsized(indirect_dest.llval={:?}, rvalue={:?})",
 189                indirect_dest.llval, rvalue);
 190
 191         match *rvalue {
 192             mir::Rvalue::Use(ref operand) => {
 193                 let cg_operand = self.codegen_operand(&bx, operand);
 194                 cg_operand.val.store_unsized(&bx, indirect_dest);
 195                 bx
 196             }
 197
 198             _ => bug!("unsized assignment other than Rvalue::Use"),
 199         }
 200     }
 201
 202     pub fn codegen_rvalue_operand(
 203         &mut self,
 204         bx: Builder<'a, 'll, 'tcx, &'ll Value>,
 205         rvalue: &mir::Rvalue<'tcx>
 206     ) -> (Builder<'a, 'll, 'tcx, &'ll Value>, OperandRef<'tcx, &'ll Value>) {
 207         assert!(self.rvalue_creates_operand(rvalue), "cannot codegen {:?} to operand", rvalue);
 208
 209         match *rvalue {
 210             mir::Rvalue::Cast(ref kind, ref source, mir_cast_ty) => {
 211                 let operand = self.codegen_operand(&bx, source);
 212                 debug!("cast operand is {:?}", operand);
 213                 let cast = bx.cx.layout_of(self.monomorphize(&mir_cast_ty));
 214
 215                 let val = match *kind {
 216                     mir::CastKind::ReifyFnPointer => {
 217                         match operand.layout.ty.sty {
 218                             ty::FnDef(def_id, substs) => {
 219                                 if bx.cx.tcx.has_attr(def_id, "rustc_args_required_const") {
 220                                     bug!("reifying a fn ptr that requires \
 221                                           const arguments");
 222                                 }
 223                                 OperandValue::Immediate(
 224                                     callee::resolve_and_get_fn(bx.cx, def_id, substs))
 225                             }
 226                             _ => {
 227                                 bug!("{} cannot be reified to a fn ptr", operand.layout.ty)
 228                             }
 229                         }
 230                     }
 231                     mir::CastKind::ClosureFnPointer => {
 232                         match operand.layout.ty.sty {
 233                             ty::Closure(def_id, substs) => {
 234                                 let instance = monomorphize::resolve_closure(
 235                                     bx.cx.tcx, def_id, substs, ty::ClosureKind::FnOnce);
 236                                 OperandValue::Immediate(callee::get_fn(bx.cx, instance))
 237                             }
 238                             _ => {
 239                                 bug!("{} cannot be cast to a fn ptr", operand.layout.ty)
 240                             }
 241                         }
 242                     }
 243                     mir::CastKind::UnsafeFnPointer => {
 244                         // this is a no-op at the LLVM level
 245                         operand.val
 246                     }
 247                     mir::CastKind::Unsize => {
 248                         assert!(cast.is_llvm_scalar_pair());
 249                         match operand.val {
 250                             OperandValue::Pair(lldata, llextra) => {
 251                                 // unsize from a fat pointer - this is a
 252                                 // "trait-object-to-supertrait" coercion, for
 253                                 // example,
 254                                 //   &'a fmt::Debug+Send => &'a fmt::Debug,
 255
 256                                 // HACK(eddyb) have to bitcast pointers
 257                                 // until LLVM removes pointee types.
 258                                 let lldata = bx.pointercast(lldata,
 259                                     cast.scalar_pair_element_llvm_type(bx.cx, 0, true));
 260                                 OperandValue::Pair(lldata, llextra)
 261                             }
 262                             OperandValue::Immediate(lldata) => {
 263                                 // "standard" unsize
 264                                 let (lldata, llextra) = base::unsize_thin_ptr(&bx, lldata,
 265                                     operand.layout.ty, cast.ty);
 266                                 OperandValue::Pair(lldata, llextra)
 267                             }
 268                             OperandValue::Ref(..) => {
 269                                 bug!("by-ref operand {:?} in codegen_rvalue_operand",
 270                                      operand);
 271                             }
 272                         }
 273                     }
 274                     mir::CastKind::Misc if operand.layout.is_llvm_scalar_pair() => {
 275                         if let OperandValue::Pair(data_ptr, meta) = operand.val {
 276                             if cast.is_llvm_scalar_pair() {
 277                                 let data_cast = bx.pointercast(data_ptr,
 278                                     cast.scalar_pair_element_llvm_type(bx.cx, 0, true));
 279                                 OperandValue::Pair(data_cast, meta)
 280                             } else { // cast to thin-ptr
 281                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 282                                 // pointer-cast of that pointer to desired pointer type.
 283                                 let llcast_ty = cast.immediate_llvm_type(bx.cx);
 284                                 let llval = bx.pointercast(data_ptr, llcast_ty);
 285                                 OperandValue::Immediate(llval)
 286                             }
 287                         } else {
 288                             bug!("Unexpected non-Pair operand")
 289                         }
 290                     }
 291                     mir::CastKind::Misc => {
 292                         assert!(cast.is_llvm_immediate());
 293                         let ll_t_out = cast.immediate_llvm_type(bx.cx);
 294                         if operand.layout.abi.is_uninhabited() {
 295                             return (bx, OperandRef {
 296                                 val: OperandValue::Immediate(C_undef(ll_t_out)),
 297                                 layout: cast,
 298                             });
 299                         }
 300                         let r_t_in = CastTy::from_ty(operand.layout.ty)
 301                             .expect("bad input type for cast");
 302                         let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
 303                         let ll_t_in = operand.layout.immediate_llvm_type(bx.cx);
 304                         match operand.layout.variants {
 305                             layout::Variants::Single { index } => {
 306                                 if let Some(def) = operand.layout.ty.ty_adt_def() {
 307                                     let discr_val = def
 308                                         .discriminant_for_variant(bx.cx.tcx, index)
 309                                         .val;
 310                                     let discr = C_uint_big(ll_t_out, discr_val);
 311                                     return (bx, OperandRef {
 312                                         val: OperandValue::Immediate(discr),
 313                                         layout: cast,
 314                                     });
 315                                 }
 316                             }
 317                             layout::Variants::Tagged { .. } |
 318                             layout::Variants::NicheFilling { .. } => {},
 319                         }
 320                         let llval = operand.immediate();
 321
 322                         let mut signed = false;
 323                         if let layout::Abi::Scalar(ref scalar) = operand.layout.abi {
 324                             if let layout::Int(_, s) = scalar.value {
 325                                 // We use `i1` for bytes that are always `0` or `1`,
 326                                 // e.g. `#[repr(i8)] enum E { A, B }`, but we can't
 327                                 // let LLVM interpret the `i1` as signed, because
 328                                 // then `i1 1` (i.e. E::B) is effectively `i8 -1`.
 329                                 signed = !scalar.is_bool() && s;
 330
 331                                 let er = scalar.valid_range_exclusive(bx.cx);
 332                                 if er.end != er.start &&
 333                                    scalar.valid_range.end() > scalar.valid_range.start() {
 334                                     // We want `table[e as usize]` to not
 335                                     // have bound checks, and this is the most
 336                                     // convenient place to put the `assume`.
 337
 338                                     base::call_assume(&bx, bx.icmp(
 339                                         IntPredicate::IntULE,
 340                                         llval,
 341                                         C_uint_big(ll_t_in, *scalar.valid_range.end())
 342                                     ));
 343                                 }
 344                             }
 345                         }
 346
 347                         let newval = match (r_t_in, r_t_out) {
 348                             (CastTy::Int(_), CastTy::Int(_)) => {
 349                                 bx.intcast(llval, ll_t_out, signed)
 350                             }
 351                             (CastTy::Float, CastTy::Float) => {
 352                                 let srcsz = ll_t_in.float_width();
 353                                 let dstsz = ll_t_out.float_width();
 354                                 if dstsz > srcsz {
 355                                     bx.fpext(llval, ll_t_out)
 356                                 } else if srcsz > dstsz {
 357                                     bx.fptrunc(llval, ll_t_out)
 358                                 } else {
 359                                     llval
 360                                 }
 361                             }
 362                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 363                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 364                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 365                                 bx.pointercast(llval, ll_t_out),
 366                             (CastTy::Ptr(_), CastTy::Int(_)) |
 367                             (CastTy::FnPtr, CastTy::Int(_)) =>
 368                                 bx.ptrtoint(llval, ll_t_out),
 369                             (CastTy::Int(_), CastTy::Ptr(_)) => {
 370                                 let usize_llval = bx.intcast(llval, bx.cx.isize_ty, signed);
 371                                 bx.inttoptr(usize_llval, ll_t_out)
 372                             }
 373                             (CastTy::Int(_), CastTy::Float) =>
 374                                 cast_int_to_float(&bx, signed, llval, ll_t_in, ll_t_out),
 375                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 376                                 cast_float_to_int(&bx, true, llval, ll_t_in, ll_t_out),
 377                             (CastTy::Float, CastTy::Int(_)) =>
 378                                 cast_float_to_int(&bx, false, llval, ll_t_in, ll_t_out),
 379                             _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty)
 380                         };
 381                         OperandValue::Immediate(newval)
 382                     }
 383                 };
 384                 (bx, OperandRef {
 385                     val,
 386                     layout: cast
 387                 })
 388             }
 389
 390             mir::Rvalue::Ref(_, bk, ref place) => {
 391                 let cg_place = self.codegen_place(&bx, place);
 392
 393                 let ty = cg_place.layout.ty;
 394
 395                 // Note: places are indirect, so storing the `llval` into the
 396                 // destination effectively creates a reference.
 397                 let val = if !bx.cx.type_has_metadata(ty) {
 398                     OperandValue::Immediate(cg_place.llval)
 399                 } else {
 400                     OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
 401                 };
 402                 (bx, OperandRef {
 403                     val,
 404                     layout: self.cx.layout_of(self.cx.tcx.mk_ref(
 405                         self.cx.tcx.types.re_erased,
 406                         ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
 407                     )),
 408                 })
 409             }
 410
 411             mir::Rvalue::Len(ref place) => {
 412                 let size = self.evaluate_array_len(&bx, place);
 413                 let operand = OperandRef {
 414                     val: OperandValue::Immediate(size),
 415                     layout: bx.cx.layout_of(bx.tcx().types.usize),
 416                 };
 417                 (bx, operand)
 418             }
 419
 420             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 421                 let lhs = self.codegen_operand(&bx, lhs);
 422                 let rhs = self.codegen_operand(&bx, rhs);
 423                 let llresult = match (lhs.val, rhs.val) {
 424                     (OperandValue::Pair(lhs_addr, lhs_extra),
 425                      OperandValue::Pair(rhs_addr, rhs_extra)) => {
 426                         self.codegen_fat_ptr_binop(&bx, op,
 427                                                  lhs_addr, lhs_extra,
 428                                                  rhs_addr, rhs_extra,
 429                                                  lhs.layout.ty)
 430                     }
 431
 432                     (OperandValue::Immediate(lhs_val),
 433                      OperandValue::Immediate(rhs_val)) => {
 434                         self.codegen_scalar_binop(&bx, op, lhs_val, rhs_val, lhs.layout.ty)
 435                     }
 436
 437                     _ => bug!()
 438                 };
 439                 let operand = OperandRef {
 440                     val: OperandValue::Immediate(llresult),
 441                     layout: bx.cx.layout_of(
 442                         op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
 443                 };
 444                 (bx, operand)
 445             }
 446             mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
 447                 let lhs = self.codegen_operand(&bx, lhs);
 448                 let rhs = self.codegen_operand(&bx, rhs);
 449                 let result = self.codegen_scalar_checked_binop(&bx, op,
 450                                                              lhs.immediate(), rhs.immediate(),
 451                                                              lhs.layout.ty);
 452                 let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
 453                 let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
 454                 let operand = OperandRef {
 455                     val: result,
 456                     layout: bx.cx.layout_of(operand_ty)
 457                 };
 458
 459                 (bx, operand)
 460             }
 461
 462             mir::Rvalue::UnaryOp(op, ref operand) => {
 463                 let operand = self.codegen_operand(&bx, operand);
 464                 let lloperand = operand.immediate();
 465                 let is_float = operand.layout.ty.is_fp();
 466                 let llval = match op {
 467                     mir::UnOp::Not => bx.not(lloperand),
 468                     mir::UnOp::Neg => if is_float {
 469                         bx.fneg(lloperand)
 470                     } else {
 471                         bx.neg(lloperand)
 472                     }
 473                 };
 474                 (bx, OperandRef {
 475                     val: OperandValue::Immediate(llval),
 476                     layout: operand.layout,
 477                 })
 478             }
 479
 480             mir::Rvalue::Discriminant(ref place) => {
 481                 let discr_ty = rvalue.ty(&*self.mir, bx.tcx());
 482                 let discr =  self.codegen_place(&bx, place)
 483                     .codegen_get_discr(&bx, discr_ty);
 484                 (bx, OperandRef {
 485                     val: OperandValue::Immediate(discr),
 486                     layout: self.cx.layout_of(discr_ty)
 487                 })
 488             }
 489
 490             mir::Rvalue::NullaryOp(mir::NullOp::SizeOf, ty) => {
 491                 assert!(bx.cx.type_is_sized(ty));
 492                 let val = C_usize(bx.cx, bx.cx.size_of(ty).bytes());
 493                 let tcx = bx.tcx();
 494                 (bx, OperandRef {
 495                     val: OperandValue::Immediate(val),
 496                     layout: self.cx.layout_of(tcx.types.usize),
 497                 })
 498             }
 499
 500             mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
 501                 let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
 502                 let (size, align) = bx.cx.size_and_align_of(content_ty);
 503                 let llsize = C_usize(bx.cx, size.bytes());
 504                 let llalign = C_usize(bx.cx, align.abi());
 505                 let box_layout = bx.cx.layout_of(bx.tcx().mk_box(content_ty));
 506                 let llty_ptr = box_layout.llvm_type(bx.cx);
 507
 508                 // Allocate space:
 509                 let def_id = match bx.tcx().lang_items().require(ExchangeMallocFnLangItem) {
 510                     Ok(id) => id,
 511                     Err(s) => {
 512                         bx.sess().fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 513                     }
 514                 };
 515                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 516                 let r = callee::get_fn(bx.cx, instance);
 517                 let val = bx.pointercast(bx.call(r, &[llsize, llalign], None), llty_ptr);
 518
 519                 let operand = OperandRef {
 520                     val: OperandValue::Immediate(val),
 521                     layout: box_layout,
 522                 };
 523                 (bx, operand)
 524             }
 525             mir::Rvalue::Use(ref operand) => {
 526                 let operand = self.codegen_operand(&bx, operand);
 527                 (bx, operand)
 528             }
 529             mir::Rvalue::Repeat(..) |
 530             mir::Rvalue::Aggregate(..) => {
 531                 // According to `rvalue_creates_operand`, only ZST
 532                 // aggregate rvalues are allowed to be operands.
 533                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 534                 (bx, OperandRef::new_zst(self.cx,
 535                     self.cx.layout_of(self.monomorphize(&ty))))
 536             }
 537         }
 538     }
 539
 540     fn evaluate_array_len(
 541         &mut self,
 542         bx: &Builder<'a, 'll, 'tcx>,
 543         place: &mir::Place<'tcx>,
 544     ) -> &'ll Value {
 545         // ZST are passed as operands and require special handling
 546         // because codegen_place() panics if Local is operand.
 547         if let mir::Place::Local(index) = *place {
 548             if let LocalRef::Operand(Some(op)) = self.locals[index] {
 549                 if let ty::Array(_, n) = op.layout.ty.sty {
 550                     let n = n.unwrap_usize(bx.cx.tcx);
 551                     return common::C_usize(bx.cx, n);
 552                 }
 553             }
 554         }
 555         // use common size calculation for non zero-sized types
 556         let cg_value = self.codegen_place(&bx, place);
 557         return cg_value.len(bx.cx);
 558     }
 559
 560     pub fn codegen_scalar_binop(
 561         &mut self,
 562         bx: &Builder<'a, 'll, 'tcx>,
 563         op: mir::BinOp,
 564         lhs: &'ll Value,
 565         rhs: &'ll Value,
 566         input_ty: Ty<'tcx>,
 567     ) -> &'ll Value {
 568         let is_float = input_ty.is_fp();
 569         let is_signed = input_ty.is_signed();
 570         let is_unit = input_ty.is_unit();
 571         match op {
 572             mir::BinOp::Add => if is_float {
 573                 bx.fadd(lhs, rhs)
 574             } else {
 575                 bx.add(lhs, rhs)
 576             },
 577             mir::BinOp::Sub => if is_float {
 578                 bx.fsub(lhs, rhs)
 579             } else {
 580                 bx.sub(lhs, rhs)
 581             },
 582             mir::BinOp::Mul => if is_float {
 583                 bx.fmul(lhs, rhs)
 584             } else {
 585                 bx.mul(lhs, rhs)
 586             },
 587             mir::BinOp::Div => if is_float {
 588                 bx.fdiv(lhs, rhs)
 589             } else if is_signed {
 590                 bx.sdiv(lhs, rhs)
 591             } else {
 592                 bx.udiv(lhs, rhs)
 593             },
 594             mir::BinOp::Rem => if is_float {
 595                 bx.frem(lhs, rhs)
 596             } else if is_signed {
 597                 bx.srem(lhs, rhs)
 598             } else {
 599                 bx.urem(lhs, rhs)
 600             },
 601             mir::BinOp::BitOr => bx.or(lhs, rhs),
 602             mir::BinOp::BitAnd => bx.and(lhs, rhs),
 603             mir::BinOp::BitXor => bx.xor(lhs, rhs),
 604             mir::BinOp::Offset => bx.inbounds_gep(lhs, &[rhs]),
 605             mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
 606             mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
 607             mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
 608             mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_unit {
 609                 C_bool(bx.cx, match op {
 610                     mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
 611                     mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,
 612                     _ => unreachable!()
 613                 })
 614             } else if is_float {
 615                 bx.fcmp(
 616                     base::bin_op_to_fcmp_predicate(op.to_hir_binop()),
 617                     lhs, rhs
 618                 )
 619             } else {
 620                 bx.icmp(
 621                     base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed),
 622                     lhs, rhs
 623                 )
 624             }
 625         }
 626     }
 627
 628     pub fn codegen_fat_ptr_binop(
 629         &mut self,
 630         bx: &Builder<'a, 'll, 'tcx>,
 631         op: mir::BinOp,
 632         lhs_addr: &'ll Value,
 633         lhs_extra: &'ll Value,
 634         rhs_addr: &'ll Value,
 635         rhs_extra: &'ll Value,
 636         _input_ty: Ty<'tcx>,
 637     ) -> &'ll Value {
 638         match op {
 639             mir::BinOp::Eq => {
 640                 bx.and(
 641                     bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
 642                     bx.icmp(IntPredicate::IntEQ, lhs_extra, rhs_extra)
 643                 )
 644             }
 645             mir::BinOp::Ne => {
 646                 bx.or(
 647                     bx.icmp(IntPredicate::IntNE, lhs_addr, rhs_addr),
 648                     bx.icmp(IntPredicate::IntNE, lhs_extra, rhs_extra)
 649                 )
 650             }
 651             mir::BinOp::Le | mir::BinOp::Lt |
 652             mir::BinOp::Ge | mir::BinOp::Gt => {
 653                 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
 654                 let (op, strict_op) = match op {
 655                     mir::BinOp::Lt => (IntPredicate::IntULT, IntPredicate::IntULT),
 656                     mir::BinOp::Le => (IntPredicate::IntULE, IntPredicate::IntULT),
 657                     mir::BinOp::Gt => (IntPredicate::IntUGT, IntPredicate::IntUGT),
 658                     mir::BinOp::Ge => (IntPredicate::IntUGE, IntPredicate::IntUGT),
 659                     _ => bug!(),
 660                 };
 661
 662                 bx.or(
 663                     bx.icmp(strict_op, lhs_addr, rhs_addr),
 664                     bx.and(
 665                         bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
 666                         bx.icmp(op, lhs_extra, rhs_extra)
 667                     )
 668                 )
 669             }
 670             _ => {
 671                 bug!("unexpected fat ptr binop");
 672             }
 673         }
 674     }
 675
 676     pub fn codegen_scalar_checked_binop(&mut self,
 677                                       bx: &Builder<'a, 'll, 'tcx>,
 678                                       op: mir::BinOp,
 679                                       lhs: &'ll Value,
 680                                       rhs: &'ll Value,
 681                                       input_ty: Ty<'tcx>) -> OperandValue<&'ll Value> {
 682         // This case can currently arise only from functions marked
 683         // with #[rustc_inherit_overflow_checks] and inlined from
 684         // another crate (mostly core::num generic/#[inline] fns),
 685         // while the current crate doesn't use overflow checks.
 686         if !bx.cx.check_overflow {
 687             let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 688             return OperandValue::Pair(val, C_bool(bx.cx, false));
 689         }
 690
 691         let (val, of) = match op {
 692             // These are checked using intrinsics
 693             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 694                 let oop = match op {
 695                     mir::BinOp::Add => OverflowOp::Add,
 696                     mir::BinOp::Sub => OverflowOp::Sub,
 697                     mir::BinOp::Mul => OverflowOp::Mul,
 698                     _ => unreachable!()
 699                 };
 700                 let intrinsic = get_overflow_intrinsic(oop, bx, input_ty);
 701                 let res = bx.call(intrinsic, &[lhs, rhs], None);
 702
 703                 (bx.extract_value(res, 0),
 704                  bx.extract_value(res, 1))
 705             }
 706             mir::BinOp::Shl | mir::BinOp::Shr => {
 707                 let lhs_llty = val_ty(lhs);
 708                 let rhs_llty = val_ty(rhs);
 709                 let invert_mask = common::shift_mask_val(&bx, lhs_llty, rhs_llty, true);
 710                 let outer_bits = bx.and(rhs, invert_mask);
 711
 712                 let of = bx.icmp(IntPredicate::IntNE, outer_bits, C_null(rhs_llty));
 713                 let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 714
 715                 (val, of)
 716             }
 717             _ => {
 718                 bug!("Operator `{:?}` is not a checkable operator", op)
 719             }
 720         };
 721
 722         OperandValue::Pair(val, of)
 723     }
 724
 725     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>) -> bool {
 726         match *rvalue {
 727             mir::Rvalue::Ref(..) |
 728             mir::Rvalue::Len(..) |
 729             mir::Rvalue::Cast(..) | // (*)
 730             mir::Rvalue::BinaryOp(..) |
 731             mir::Rvalue::CheckedBinaryOp(..) |
 732             mir::Rvalue::UnaryOp(..) |
 733             mir::Rvalue::Discriminant(..) |
 734             mir::Rvalue::NullaryOp(..) |
 735             mir::Rvalue::Use(..) => // (*)
 736                 true,
 737             mir::Rvalue::Repeat(..) |
 738             mir::Rvalue::Aggregate(..) => {
 739                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 740                 let ty = self.monomorphize(&ty);
 741                 self.cx.layout_of(ty).is_zst()
 742             }
 743         }
 744
 745         // (*) this is only true if the type is suitable
 746     }
 747 }
 748
 749 #[derive(Copy, Clone)]
 750 enum OverflowOp {
 751     Add, Sub, Mul
 752 }
 753
 754 fn get_overflow_intrinsic(
 755     oop: OverflowOp,
 756     bx: &Builder<'_, 'll, '_, &'ll Value>,
 757     ty: Ty
 758 ) -> &'ll Value {
 759     use syntax::ast::IntTy::*;
 760     use syntax::ast::UintTy::*;
 761     use rustc::ty::{Int, Uint};
 762
 763     let tcx = bx.tcx();
 764
 765     let new_sty = match ty.sty {
 766         Int(Isize) => Int(tcx.sess.target.isize_ty),
 767         Uint(Usize) => Uint(tcx.sess.target.usize_ty),
 768         ref t @ Uint(_) | ref t @ Int(_) => t.clone(),
 769         _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
 770     };
 771
 772     let name = match oop {
 773         OverflowOp::Add => match new_sty {
 774             Int(I8) => "llvm.sadd.with.overflow.i8",
 775             Int(I16) => "llvm.sadd.with.overflow.i16",
 776             Int(I32) => "llvm.sadd.with.overflow.i32",
 777             Int(I64) => "llvm.sadd.with.overflow.i64",
 778             Int(I128) => "llvm.sadd.with.overflow.i128",
 779
 780             Uint(U8) => "llvm.uadd.with.overflow.i8",
 781             Uint(U16) => "llvm.uadd.with.overflow.i16",
 782             Uint(U32) => "llvm.uadd.with.overflow.i32",
 783             Uint(U64) => "llvm.uadd.with.overflow.i64",
 784             Uint(U128) => "llvm.uadd.with.overflow.i128",
 785
 786             _ => unreachable!(),
 787         },
 788         OverflowOp::Sub => match new_sty {
 789             Int(I8) => "llvm.ssub.with.overflow.i8",
 790             Int(I16) => "llvm.ssub.with.overflow.i16",
 791             Int(I32) => "llvm.ssub.with.overflow.i32",
 792             Int(I64) => "llvm.ssub.with.overflow.i64",
 793             Int(I128) => "llvm.ssub.with.overflow.i128",
 794
 795             Uint(U8) => "llvm.usub.with.overflow.i8",
 796             Uint(U16) => "llvm.usub.with.overflow.i16",
 797             Uint(U32) => "llvm.usub.with.overflow.i32",
 798             Uint(U64) => "llvm.usub.with.overflow.i64",
 799             Uint(U128) => "llvm.usub.with.overflow.i128",
 800
 801             _ => unreachable!(),
 802         },
 803         OverflowOp::Mul => match new_sty {
 804             Int(I8) => "llvm.smul.with.overflow.i8",
 805             Int(I16) => "llvm.smul.with.overflow.i16",
 806             Int(I32) => "llvm.smul.with.overflow.i32",
 807             Int(I64) => "llvm.smul.with.overflow.i64",
 808             Int(I128) => "llvm.smul.with.overflow.i128",
 809
 810             Uint(U8) => "llvm.umul.with.overflow.i8",
 811             Uint(U16) => "llvm.umul.with.overflow.i16",
 812             Uint(U32) => "llvm.umul.with.overflow.i32",
 813             Uint(U64) => "llvm.umul.with.overflow.i64",
 814             Uint(U128) => "llvm.umul.with.overflow.i128",
 815
 816             _ => unreachable!(),
 817         },
 818     };
 819
 820     bx.cx.get_intrinsic(&name)
 821 }
 822
 823 fn cast_int_to_float(bx: &Builder<'_, 'll, '_>,
 824                      signed: bool,
 825                      x: &'ll Value,
 826                      int_ty: &'ll Type,
 827                      float_ty: &'ll Type) -> &'ll Value {
 828     // Most integer types, even i128, fit into [-f32::MAX, f32::MAX] after rounding.
 829     // It's only u128 -> f32 that can cause overflows (i.e., should yield infinity).
 830     // LLVM's uitofp produces undef in those cases, so we manually check for that case.
 831     let is_u128_to_f32 = !signed && int_ty.int_width() == 128 && float_ty.float_width() == 32;
 832     if is_u128_to_f32 {
 833         // All inputs greater or equal to (f32::MAX + 0.5 ULP) are rounded to infinity,
 834         // and for everything else LLVM's uitofp works just fine.
 835         use rustc_apfloat::ieee::Single;
 836         use rustc_apfloat::Float;
 837         const MAX_F32_PLUS_HALF_ULP: u128 = ((1 << (Single::PRECISION + 1)) - 1)
 838                                             << (Single::MAX_EXP - Single::PRECISION as i16);
 839         let max = C_uint_big(int_ty, MAX_F32_PLUS_HALF_ULP);
 840         let overflow = bx.icmp(IntPredicate::IntUGE, x, max);
 841         let infinity_bits = C_u32(bx.cx, ieee::Single::INFINITY.to_bits() as u32);
 842         let infinity = consts::bitcast(infinity_bits, float_ty);
 843         bx.select(overflow, infinity, bx.uitofp(x, float_ty))
 844     } else {
 845         if signed {
 846             bx.sitofp(x, float_ty)
 847         } else {
 848             bx.uitofp(x, float_ty)
 849         }
 850     }
 851 }
 852
 853 fn cast_float_to_int(bx: &Builder<'_, 'll, '_>,
 854                      signed: bool,
 855                      x: &'ll Value,
 856                      float_ty: &'ll Type,
 857                      int_ty: &'ll Type) -> &'ll Value {
 858     let fptosui_result = if signed {
 859         bx.fptosi(x, int_ty)
 860     } else {
 861         bx.fptoui(x, int_ty)
 862     };
 863
 864     if !bx.sess().opts.debugging_opts.saturating_float_casts {
 865         return fptosui_result;
 866     }
 867     // LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the
 868     // destination integer type after rounding towards zero. This `undef` value can cause UB in
 869     // safe code (see issue #10184), so we implement a saturating conversion on top of it:
 870     // Semantically, the mathematical value of the input is rounded towards zero to the next
 871     // mathematical integer, and then the result is clamped into the range of the destination
 872     // integer type. Positive and negative infinity are mapped to the maximum and minimum value of
 873     // the destination integer type. NaN is mapped to 0.
 874     //
 875     // Define f_min and f_max as the largest and smallest (finite) floats that are exactly equal to
 876     // a value representable in int_ty.
 877     // They are exactly equal to int_ty::{MIN,MAX} if float_ty has enough significand bits.
 878     // Otherwise, int_ty::MAX must be rounded towards zero, as it is one less than a power of two.
 879     // int_ty::MIN, however, is either zero or a negative power of two and is thus exactly
 880     // representable. Note that this only works if float_ty's exponent range is sufficiently large.
 881     // f16 or 256 bit integers would break this property. Right now the smallest float type is f32
 882     // with exponents ranging up to 127, which is barely enough for i128::MIN = -2^127.
 883     // On the other hand, f_max works even if int_ty::MAX is greater than float_ty::MAX. Because
 884     // we're rounding towards zero, we just get float_ty::MAX (which is always an integer).
 885     // This already happens today with u128::MAX = 2^128 - 1 > f32::MAX.
 886     fn compute_clamp_bounds<F: Float>(signed: bool, int_ty: &Type) -> (u128, u128) {
 887         let rounded_min = F::from_i128_r(int_min(signed, int_ty), Round::TowardZero);
 888         assert_eq!(rounded_min.status, Status::OK);
 889         let rounded_max = F::from_u128_r(int_max(signed, int_ty), Round::TowardZero);
 890         assert!(rounded_max.value.is_finite());
 891         (rounded_min.value.to_bits(), rounded_max.value.to_bits())
 892     }
 893     fn int_max(signed: bool, int_ty: &Type) -> u128 {
 894         let shift_amount = 128 - int_ty.int_width();
 895         if signed {
 896             i128::MAX as u128 >> shift_amount
 897         } else {
 898             u128::MAX >> shift_amount
 899         }
 900     }
 901     fn int_min(signed: bool, int_ty: &Type) -> i128 {
 902         if signed {
 903             i128::MIN >> (128 - int_ty.int_width())
 904         } else {
 905             0
 906         }
 907     }
 908     let float_bits_to_llval = |bits| {
 909         let bits_llval = match float_ty.float_width() {
 910             32 => C_u32(bx.cx, bits as u32),
 911             64 => C_u64(bx.cx, bits as u64),
 912             n => bug!("unsupported float width {}", n),
 913         };
 914         consts::bitcast(bits_llval, float_ty)
 915     };
 916     let (f_min, f_max) = match float_ty.float_width() {
 917         32 => compute_clamp_bounds::<ieee::Single>(signed, int_ty),
 918         64 => compute_clamp_bounds::<ieee::Double>(signed, int_ty),
 919         n => bug!("unsupported float width {}", n),
 920     };
 921     let f_min = float_bits_to_llval(f_min);
 922     let f_max = float_bits_to_llval(f_max);
 923     // To implement saturation, we perform the following steps:
 924     //
 925     // 1. Cast x to an integer with fpto[su]i. This may result in undef.
 926     // 2. Compare x to f_min and f_max, and use the comparison results to select:
 927     //  a) int_ty::MIN if x < f_min or x is NaN
 928     //  b) int_ty::MAX if x > f_max
 929     //  c) the result of fpto[su]i otherwise
 930     // 3. If x is NaN, return 0.0, otherwise return the result of step 2.
 931     //
 932     // This avoids resulting undef because values in range [f_min, f_max] by definition fit into the
 933     // destination type. It creates an undef temporary, but *producing* undef is not UB. Our use of
 934     // undef does not introduce any non-determinism either.
 935     // More importantly, the above procedure correctly implements saturating conversion.
 936     // Proof (sketch):
 937     // If x is NaN, 0 is returned by definition.
 938     // Otherwise, x is finite or infinite and thus can be compared with f_min and f_max.
 939     // This yields three cases to consider:
 940     // (1) if x in [f_min, f_max], the result of fpto[su]i is returned, which agrees with
 941     //     saturating conversion for inputs in that range.
 942     // (2) if x > f_max, then x is larger than int_ty::MAX. This holds even if f_max is rounded
 943     //     (i.e., if f_max < int_ty::MAX) because in those cases, nextUp(f_max) is already larger
 944     //     than int_ty::MAX. Because x is larger than int_ty::MAX, the return value of int_ty::MAX
 945     //     is correct.
 946     // (3) if x < f_min, then x is smaller than int_ty::MIN. As shown earlier, f_min exactly equals
 947     //     int_ty::MIN and therefore the return value of int_ty::MIN is correct.
 948     // QED.
 949
 950     // Step 1 was already performed above.
 951
 952     // Step 2: We use two comparisons and two selects, with %s1 being the result:
 953     //     %less_or_nan = fcmp ult %x, %f_min
 954     //     %greater = fcmp olt %x, %f_max
 955     //     %s0 = select %less_or_nan, int_ty::MIN, %fptosi_result
 956     //     %s1 = select %greater, int_ty::MAX, %s0
 957     // Note that %less_or_nan uses an *unordered* comparison. This comparison is true if the
 958     // operands are not comparable (i.e., if x is NaN). The unordered comparison ensures that s1
 959     // becomes int_ty::MIN if x is NaN.
 960     // Performance note: Unordered comparison can be lowered to a "flipped" comparison and a
 961     // negation, and the negation can be merged into the select. Therefore, it not necessarily any
 962     // more expensive than a ordered ("normal") comparison. Whether these optimizations will be
 963     // performed is ultimately up to the backend, but at least x86 does perform them.
 964     let less_or_nan = bx.fcmp(RealPredicate::RealULT, x, f_min);
 965     let greater = bx.fcmp(RealPredicate::RealOGT, x, f_max);
 966     let int_max = C_uint_big(int_ty, int_max(signed, int_ty));
 967     let int_min = C_uint_big(int_ty, int_min(signed, int_ty) as u128);
 968     let s0 = bx.select(less_or_nan, int_min, fptosui_result);
 969     let s1 = bx.select(greater, int_max, s0);
 970
 971     // Step 3: NaN replacement.
 972     // For unsigned types, the above step already yielded int_ty::MIN == 0 if x is NaN.
 973     // Therefore we only need to execute this step for signed integer types.
 974     if signed {
 975         // LLVM has no isNaN predicate, so we use (x == x) instead
 976         bx.select(bx.fcmp(RealPredicate::RealOEQ, x, x), s1, C_uint(int_ty, 0))
 977     } else {
 978         s1
 979     }
 980 }