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, IntPredicate, RealPredicate};
  23 use context::CodegenCx;
  24 use consts;
  25 use monomorphize;
  26 use type_::Type;
  27 use type_of::LayoutLlvmExt;
  28 use value::Value;
  29
  30 use interfaces::{BuilderMethods, CommonMethods, CommonWriteMethods};
  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, bx.cx().c_usize(0)).llval;
 107
 108                 if let OperandValue::Immediate(v) = cg_elem.val {
 109                     let align = bx.cx().c_i32(dest.align.abi() as i32);
 110                     let size = bx.cx().c_usize(dest.layout.size.bytes());
 111
 112                     // Use llvm.memset.p0i8.* to initialize all zero arrays
 113                     if CodegenCx::is_const_integral(v) && CodegenCx::const_to_uint(v) == 0 {
 114                         let fill = bx.cx().c_u8(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 bx.cx().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 = bx.cx().c_usize(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(bx.cx().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, &[bx.cx().c_usize(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>,
 184                         indirect_dest: PlaceRef<'tcx, &'ll Value>,
 185                         rvalue: &mir::Rvalue<'tcx>)
 186                         -> Builder<'a, 'll, 'tcx>
 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>,
 205         rvalue: &mir::Rvalue<'tcx>
 206     ) -> (Builder<'a, 'll, 'tcx>, 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                             let val = OperandValue::Immediate(bx.cx().c_undef(ll_t_out));
 296                             return (bx, OperandRef {
 297                                 val,
 298                                 layout: cast,
 299                             });
 300                         }
 301                         let r_t_in = CastTy::from_ty(operand.layout.ty)
 302                             .expect("bad input type for cast");
 303                         let r_t_out = CastTy::from_ty(cast.ty).expect("bad output type for cast");
 304                         let ll_t_in = operand.layout.immediate_llvm_type(bx.cx());
 305                         match operand.layout.variants {
 306                             layout::Variants::Single { index } => {
 307                                 if let Some(def) = operand.layout.ty.ty_adt_def() {
 308                                     let discr_val = def
 309                                         .discriminant_for_variant(bx.cx().tcx, index)
 310                                         .val;
 311                                     let discr = bx.cx().c_uint_big(ll_t_out, discr_val);
 312                                     return (bx, OperandRef {
 313                                         val: OperandValue::Immediate(discr),
 314                                         layout: cast,
 315                                     });
 316                                 }
 317                             }
 318                             layout::Variants::Tagged { .. } |
 319                             layout::Variants::NicheFilling { .. } => {},
 320                         }
 321                         let llval = operand.immediate();
 322
 323                         let mut signed = false;
 324                         if let layout::Abi::Scalar(ref scalar) = operand.layout.abi {
 325                             if let layout::Int(_, s) = scalar.value {
 326                                 // We use `i1` for bytes that are always `0` or `1`,
 327                                 // e.g. `#[repr(i8)] enum E { A, B }`, but we can't
 328                                 // let LLVM interpret the `i1` as signed, because
 329                                 // then `i1 1` (i.e. E::B) is effectively `i8 -1`.
 330                                 signed = !scalar.is_bool() && s;
 331
 332                                 let er = scalar.valid_range_exclusive(bx.cx());
 333                                 if er.end != er.start &&
 334                                    scalar.valid_range.end() > scalar.valid_range.start() {
 335                                     // We want `table[e as usize]` to not
 336                                     // have bound checks, and this is the most
 337                                     // convenient place to put the `assume`.
 338
 339                                     base::call_assume(&bx, bx.icmp(
 340                                         IntPredicate::IntULE,
 341                                         llval,
 342                                         bx.cx().c_uint_big(ll_t_in, *scalar.valid_range.end())
 343                                     ));
 344                                 }
 345                             }
 346                         }
 347
 348                         let newval = match (r_t_in, r_t_out) {
 349                             (CastTy::Int(_), CastTy::Int(_)) => {
 350                                 bx.intcast(llval, ll_t_out, signed)
 351                             }
 352                             (CastTy::Float, CastTy::Float) => {
 353                                 let srcsz = ll_t_in.float_width();
 354                                 let dstsz = ll_t_out.float_width();
 355                                 if dstsz > srcsz {
 356                                     bx.fpext(llval, ll_t_out)
 357                                 } else if srcsz > dstsz {
 358                                     bx.fptrunc(llval, ll_t_out)
 359                                 } else {
 360                                     llval
 361                                 }
 362                             }
 363                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 364                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 365                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 366                                 bx.pointercast(llval, ll_t_out),
 367                             (CastTy::Ptr(_), CastTy::Int(_)) |
 368                             (CastTy::FnPtr, CastTy::Int(_)) =>
 369                                 bx.ptrtoint(llval, ll_t_out),
 370                             (CastTy::Int(_), CastTy::Ptr(_)) => {
 371                                 let usize_llval = bx.intcast(llval, bx.cx().isize_ty, signed);
 372                                 bx.inttoptr(usize_llval, ll_t_out)
 373                             }
 374                             (CastTy::Int(_), CastTy::Float) =>
 375                                 cast_int_to_float(&bx, signed, llval, ll_t_in, ll_t_out),
 376                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 377                                 cast_float_to_int(&bx, true, llval, ll_t_in, ll_t_out),
 378                             (CastTy::Float, CastTy::Int(_)) =>
 379                                 cast_float_to_int(&bx, false, llval, ll_t_in, ll_t_out),
 380                             _ => bug!("unsupported cast: {:?} to {:?}", operand.layout.ty, cast.ty)
 381                         };
 382                         OperandValue::Immediate(newval)
 383                     }
 384                 };
 385                 (bx, OperandRef {
 386                     val,
 387                     layout: cast
 388                 })
 389             }
 390
 391             mir::Rvalue::Ref(_, bk, ref place) => {
 392                 let cg_place = self.codegen_place(&bx, place);
 393
 394                 let ty = cg_place.layout.ty;
 395
 396                 // Note: places are indirect, so storing the `llval` into the
 397                 // destination effectively creates a reference.
 398                 let val = if !bx.cx().type_has_metadata(ty) {
 399                     OperandValue::Immediate(cg_place.llval)
 400                 } else {
 401                     OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
 402                 };
 403                 (bx, OperandRef {
 404                     val,
 405                     layout: self.cx.layout_of(self.cx.tcx.mk_ref(
 406                         self.cx.tcx.types.re_erased,
 407                         ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
 408                     )),
 409                 })
 410             }
 411
 412             mir::Rvalue::Len(ref place) => {
 413                 let size = self.evaluate_array_len(&bx, place);
 414                 let operand = OperandRef {
 415                     val: OperandValue::Immediate(size),
 416                     layout: bx.cx().layout_of(bx.tcx().types.usize),
 417                 };
 418                 (bx, operand)
 419             }
 420
 421             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 422                 let lhs = self.codegen_operand(&bx, lhs);
 423                 let rhs = self.codegen_operand(&bx, rhs);
 424                 let llresult = match (lhs.val, rhs.val) {
 425                     (OperandValue::Pair(lhs_addr, lhs_extra),
 426                      OperandValue::Pair(rhs_addr, rhs_extra)) => {
 427                         self.codegen_fat_ptr_binop(&bx, op,
 428                                                  lhs_addr, lhs_extra,
 429                                                  rhs_addr, rhs_extra,
 430                                                  lhs.layout.ty)
 431                     }
 432
 433                     (OperandValue::Immediate(lhs_val),
 434                      OperandValue::Immediate(rhs_val)) => {
 435                         self.codegen_scalar_binop(&bx, op, lhs_val, rhs_val, lhs.layout.ty)
 436                     }
 437
 438                     _ => bug!()
 439                 };
 440                 let operand = OperandRef {
 441                     val: OperandValue::Immediate(llresult),
 442                     layout: bx.cx().layout_of(
 443                         op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty)),
 444                 };
 445                 (bx, operand)
 446             }
 447             mir::Rvalue::CheckedBinaryOp(op, ref lhs, ref rhs) => {
 448                 let lhs = self.codegen_operand(&bx, lhs);
 449                 let rhs = self.codegen_operand(&bx, rhs);
 450                 let result = self.codegen_scalar_checked_binop(&bx, op,
 451                                                              lhs.immediate(), rhs.immediate(),
 452                                                              lhs.layout.ty);
 453                 let val_ty = op.ty(bx.tcx(), lhs.layout.ty, rhs.layout.ty);
 454                 let operand_ty = bx.tcx().intern_tup(&[val_ty, bx.tcx().types.bool]);
 455                 let operand = OperandRef {
 456                     val: result,
 457                     layout: bx.cx().layout_of(operand_ty)
 458                 };
 459
 460                 (bx, operand)
 461             }
 462
 463             mir::Rvalue::UnaryOp(op, ref operand) => {
 464                 let operand = self.codegen_operand(&bx, operand);
 465                 let lloperand = operand.immediate();
 466                 let is_float = operand.layout.ty.is_fp();
 467                 let llval = match op {
 468                     mir::UnOp::Not => bx.not(lloperand),
 469                     mir::UnOp::Neg => if is_float {
 470                         bx.fneg(lloperand)
 471                     } else {
 472                         bx.neg(lloperand)
 473                     }
 474                 };
 475                 (bx, OperandRef {
 476                     val: OperandValue::Immediate(llval),
 477                     layout: operand.layout,
 478                 })
 479             }
 480
 481             mir::Rvalue::Discriminant(ref place) => {
 482                 let discr_ty = rvalue.ty(&*self.mir, bx.tcx());
 483                 let discr =  self.codegen_place(&bx, place)
 484                     .codegen_get_discr(&bx, discr_ty);
 485                 (bx, OperandRef {
 486                     val: OperandValue::Immediate(discr),
 487                     layout: self.cx.layout_of(discr_ty)
 488                 })
 489             }
 490
 491             mir::Rvalue::NullaryOp(mir::NullOp::SizeOf, ty) => {
 492                 assert!(bx.cx().type_is_sized(ty));
 493                 let val = bx.cx().c_usize(bx.cx().size_of(ty).bytes());
 494                 let tcx = bx.tcx();
 495                 (bx, OperandRef {
 496                     val: OperandValue::Immediate(val),
 497                     layout: self.cx.layout_of(tcx.types.usize),
 498                 })
 499             }
 500
 501             mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
 502                 let content_ty: Ty<'tcx> = self.monomorphize(&content_ty);
 503                 let (size, align) = bx.cx().size_and_align_of(content_ty);
 504                 let llsize = bx.cx().c_usize(size.bytes());
 505                 let llalign = bx.cx().c_usize(align.abi());
 506                 let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
 507                 let llty_ptr = box_layout.llvm_type(bx.cx());
 508
 509                 // Allocate space:
 510                 let def_id = match bx.tcx().lang_items().require(ExchangeMallocFnLangItem) {
 511                     Ok(id) => id,
 512                     Err(s) => {
 513                         bx.sess().fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 514                     }
 515                 };
 516                 let instance = ty::Instance::mono(bx.tcx(), def_id);
 517                 let r = callee::get_fn(bx.cx(), instance);
 518                 let val = bx.pointercast(bx.call(r, &[llsize, llalign], None), llty_ptr);
 519
 520                 let operand = OperandRef {
 521                     val: OperandValue::Immediate(val),
 522                     layout: box_layout,
 523                 };
 524                 (bx, operand)
 525             }
 526             mir::Rvalue::Use(ref operand) => {
 527                 let operand = self.codegen_operand(&bx, operand);
 528                 (bx, operand)
 529             }
 530             mir::Rvalue::Repeat(..) |
 531             mir::Rvalue::Aggregate(..) => {
 532                 // According to `rvalue_creates_operand`, only ZST
 533                 // aggregate rvalues are allowed to be operands.
 534                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 535                 (bx, OperandRef::new_zst(self.cx,
 536                     self.cx.layout_of(self.monomorphize(&ty))))
 537             }
 538         }
 539     }
 540
 541     fn evaluate_array_len(
 542         &mut self,
 543         bx: &Builder<'a, 'll, 'tcx>,
 544         place: &mir::Place<'tcx>,
 545     ) -> &'ll Value {
 546         // ZST are passed as operands and require special handling
 547         // because codegen_place() panics if Local is operand.
 548         if let mir::Place::Local(index) = *place {
 549             if let LocalRef::Operand(Some(op)) = self.locals[index] {
 550                 if let ty::Array(_, n) = op.layout.ty.sty {
 551                     let n = n.unwrap_usize(bx.cx().tcx);
 552                     return bx.cx().c_usize(n);
 553                 }
 554             }
 555         }
 556         // use common size calculation for non zero-sized types
 557         let cg_value = self.codegen_place(&bx, place);
 558         return cg_value.len(bx.cx());
 559     }
 560
 561     pub fn codegen_scalar_binop(
 562         &mut self,
 563         bx: &Builder<'a, 'll, 'tcx>,
 564         op: mir::BinOp,
 565         lhs: &'ll Value,
 566         rhs: &'ll Value,
 567         input_ty: Ty<'tcx>,
 568     ) -> &'ll Value {
 569         let is_float = input_ty.is_fp();
 570         let is_signed = input_ty.is_signed();
 571         let is_unit = input_ty.is_unit();
 572         match op {
 573             mir::BinOp::Add => if is_float {
 574                 bx.fadd(lhs, rhs)
 575             } else {
 576                 bx.add(lhs, rhs)
 577             },
 578             mir::BinOp::Sub => if is_float {
 579                 bx.fsub(lhs, rhs)
 580             } else {
 581                 bx.sub(lhs, rhs)
 582             },
 583             mir::BinOp::Mul => if is_float {
 584                 bx.fmul(lhs, rhs)
 585             } else {
 586                 bx.mul(lhs, rhs)
 587             },
 588             mir::BinOp::Div => if is_float {
 589                 bx.fdiv(lhs, rhs)
 590             } else if is_signed {
 591                 bx.sdiv(lhs, rhs)
 592             } else {
 593                 bx.udiv(lhs, rhs)
 594             },
 595             mir::BinOp::Rem => if is_float {
 596                 bx.frem(lhs, rhs)
 597             } else if is_signed {
 598                 bx.srem(lhs, rhs)
 599             } else {
 600                 bx.urem(lhs, rhs)
 601             },
 602             mir::BinOp::BitOr => bx.or(lhs, rhs),
 603             mir::BinOp::BitAnd => bx.and(lhs, rhs),
 604             mir::BinOp::BitXor => bx.xor(lhs, rhs),
 605             mir::BinOp::Offset => bx.inbounds_gep(lhs, &[rhs]),
 606             mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
 607             mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
 608             mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
 609             mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_unit {
 610                 bx.cx().c_bool(match op {
 611                     mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
 612                     mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,
 613                     _ => unreachable!()
 614                 })
 615             } else if is_float {
 616                 bx.fcmp(
 617                     base::bin_op_to_fcmp_predicate(op.to_hir_binop()),
 618                     lhs, rhs
 619                 )
 620             } else {
 621                 bx.icmp(
 622                     base::bin_op_to_icmp_predicate(op.to_hir_binop(), is_signed),
 623                     lhs, rhs
 624                 )
 625             }
 626         }
 627     }
 628
 629     pub fn codegen_fat_ptr_binop(
 630         &mut self,
 631         bx: &Builder<'a, 'll, 'tcx>,
 632         op: mir::BinOp,
 633         lhs_addr: &'ll Value,
 634         lhs_extra: &'ll Value,
 635         rhs_addr: &'ll Value,
 636         rhs_extra: &'ll Value,
 637         _input_ty: Ty<'tcx>,
 638     ) -> &'ll Value {
 639         match op {
 640             mir::BinOp::Eq => {
 641                 bx.and(
 642                     bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
 643                     bx.icmp(IntPredicate::IntEQ, lhs_extra, rhs_extra)
 644                 )
 645             }
 646             mir::BinOp::Ne => {
 647                 bx.or(
 648                     bx.icmp(IntPredicate::IntNE, lhs_addr, rhs_addr),
 649                     bx.icmp(IntPredicate::IntNE, lhs_extra, rhs_extra)
 650                 )
 651             }
 652             mir::BinOp::Le | mir::BinOp::Lt |
 653             mir::BinOp::Ge | mir::BinOp::Gt => {
 654                 // a OP b ~ a.0 STRICT(OP) b.0 | (a.0 == b.0 && a.1 OP a.1)
 655                 let (op, strict_op) = match op {
 656                     mir::BinOp::Lt => (IntPredicate::IntULT, IntPredicate::IntULT),
 657                     mir::BinOp::Le => (IntPredicate::IntULE, IntPredicate::IntULT),
 658                     mir::BinOp::Gt => (IntPredicate::IntUGT, IntPredicate::IntUGT),
 659                     mir::BinOp::Ge => (IntPredicate::IntUGE, IntPredicate::IntUGT),
 660                     _ => bug!(),
 661                 };
 662
 663                 bx.or(
 664                     bx.icmp(strict_op, lhs_addr, rhs_addr),
 665                     bx.and(
 666                         bx.icmp(IntPredicate::IntEQ, lhs_addr, rhs_addr),
 667                         bx.icmp(op, lhs_extra, rhs_extra)
 668                     )
 669                 )
 670             }
 671             _ => {
 672                 bug!("unexpected fat ptr binop");
 673             }
 674         }
 675     }
 676
 677     pub fn codegen_scalar_checked_binop(&mut self,
 678                                       bx: &Builder<'a, 'll, 'tcx>,
 679                                       op: mir::BinOp,
 680                                       lhs: &'ll Value,
 681                                       rhs: &'ll Value,
 682                                       input_ty: Ty<'tcx>) -> OperandValue<&'ll Value> {
 683         // This case can currently arise only from functions marked
 684         // with #[rustc_inherit_overflow_checks] and inlined from
 685         // another crate (mostly core::num generic/#[inline] fns),
 686         // while the current crate doesn't use overflow checks.
 687         if !bx.cx().check_overflow {
 688             let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 689             return OperandValue::Pair(val, bx.cx().c_bool(false));
 690         }
 691
 692         let (val, of) = match op {
 693             // These are checked using intrinsics
 694             mir::BinOp::Add | mir::BinOp::Sub | mir::BinOp::Mul => {
 695                 let oop = match op {
 696                     mir::BinOp::Add => OverflowOp::Add,
 697                     mir::BinOp::Sub => OverflowOp::Sub,
 698                     mir::BinOp::Mul => OverflowOp::Mul,
 699                     _ => unreachable!()
 700                 };
 701                 let intrinsic = get_overflow_intrinsic(oop, bx, input_ty);
 702                 let res = bx.call(intrinsic, &[lhs, rhs], None);
 703
 704                 (bx.extract_value(res, 0),
 705                  bx.extract_value(res, 1))
 706             }
 707             mir::BinOp::Shl | mir::BinOp::Shr => {
 708                 let lhs_llty = bx.cx().val_ty(lhs);
 709                 let rhs_llty = bx.cx().val_ty(rhs);
 710                 let invert_mask = common::shift_mask_val(&bx, lhs_llty, rhs_llty, true);
 711                 let outer_bits = bx.and(rhs, invert_mask);
 712
 713                 let of = bx.icmp(IntPredicate::IntNE, outer_bits, bx.cx().c_null(rhs_llty));
 714                 let val = self.codegen_scalar_binop(bx, op, lhs, rhs, input_ty);
 715
 716                 (val, of)
 717             }
 718             _ => {
 719                 bug!("Operator `{:?}` is not a checkable operator", op)
 720             }
 721         };
 722
 723         OperandValue::Pair(val, of)
 724     }
 725
 726     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>) -> bool {
 727         match *rvalue {
 728             mir::Rvalue::Ref(..) |
 729             mir::Rvalue::Len(..) |
 730             mir::Rvalue::Cast(..) | // (*)
 731             mir::Rvalue::BinaryOp(..) |
 732             mir::Rvalue::CheckedBinaryOp(..) |
 733             mir::Rvalue::UnaryOp(..) |
 734             mir::Rvalue::Discriminant(..) |
 735             mir::Rvalue::NullaryOp(..) |
 736             mir::Rvalue::Use(..) => // (*)
 737                 true,
 738             mir::Rvalue::Repeat(..) |
 739             mir::Rvalue::Aggregate(..) => {
 740                 let ty = rvalue.ty(self.mir, self.cx.tcx);
 741                 let ty = self.monomorphize(&ty);
 742                 self.cx.layout_of(ty).is_zst()
 743             }
 744         }
 745
 746         // (*) this is only true if the type is suitable
 747     }
 748 }
 749
 750 #[derive(Copy, Clone)]
 751 enum OverflowOp {
 752     Add, Sub, Mul
 753 }
 754
 755 fn get_overflow_intrinsic(
 756     oop: OverflowOp,
 757     bx: &Builder<'_, 'll, '_>,
 758     ty: Ty
 759 ) -> &'ll Value {
 760     use syntax::ast::IntTy::*;
 761     use syntax::ast::UintTy::*;
 762     use rustc::ty::{Int, Uint};
 763
 764     let tcx = bx.tcx();
 765
 766     let new_sty = match ty.sty {
 767         Int(Isize) => Int(tcx.sess.target.isize_ty),
 768         Uint(Usize) => Uint(tcx.sess.target.usize_ty),
 769         ref t @ Uint(_) | ref t @ Int(_) => t.clone(),
 770         _ => panic!("tried to get overflow intrinsic for op applied to non-int type")
 771     };
 772
 773     let name = match oop {
 774         OverflowOp::Add => match new_sty {
 775             Int(I8) => "llvm.sadd.with.overflow.i8",
 776             Int(I16) => "llvm.sadd.with.overflow.i16",
 777             Int(I32) => "llvm.sadd.with.overflow.i32",
 778             Int(I64) => "llvm.sadd.with.overflow.i64",
 779             Int(I128) => "llvm.sadd.with.overflow.i128",
 780
 781             Uint(U8) => "llvm.uadd.with.overflow.i8",
 782             Uint(U16) => "llvm.uadd.with.overflow.i16",
 783             Uint(U32) => "llvm.uadd.with.overflow.i32",
 784             Uint(U64) => "llvm.uadd.with.overflow.i64",
 785             Uint(U128) => "llvm.uadd.with.overflow.i128",
 786
 787             _ => unreachable!(),
 788         },
 789         OverflowOp::Sub => match new_sty {
 790             Int(I8) => "llvm.ssub.with.overflow.i8",
 791             Int(I16) => "llvm.ssub.with.overflow.i16",
 792             Int(I32) => "llvm.ssub.with.overflow.i32",
 793             Int(I64) => "llvm.ssub.with.overflow.i64",
 794             Int(I128) => "llvm.ssub.with.overflow.i128",
 795
 796             Uint(U8) => "llvm.usub.with.overflow.i8",
 797             Uint(U16) => "llvm.usub.with.overflow.i16",
 798             Uint(U32) => "llvm.usub.with.overflow.i32",
 799             Uint(U64) => "llvm.usub.with.overflow.i64",
 800             Uint(U128) => "llvm.usub.with.overflow.i128",
 801
 802             _ => unreachable!(),
 803         },
 804         OverflowOp::Mul => match new_sty {
 805             Int(I8) => "llvm.smul.with.overflow.i8",
 806             Int(I16) => "llvm.smul.with.overflow.i16",
 807             Int(I32) => "llvm.smul.with.overflow.i32",
 808             Int(I64) => "llvm.smul.with.overflow.i64",
 809             Int(I128) => "llvm.smul.with.overflow.i128",
 810
 811             Uint(U8) => "llvm.umul.with.overflow.i8",
 812             Uint(U16) => "llvm.umul.with.overflow.i16",
 813             Uint(U32) => "llvm.umul.with.overflow.i32",
 814             Uint(U64) => "llvm.umul.with.overflow.i64",
 815             Uint(U128) => "llvm.umul.with.overflow.i128",
 816
 817             _ => unreachable!(),
 818         },
 819     };
 820
 821     bx.cx().get_intrinsic(&name)
 822 }
 823
 824 fn cast_int_to_float(bx: &Builder<'_, 'll, '_>,
 825                      signed: bool,
 826                      x: &'ll Value,
 827                      int_ty: &'ll Type,
 828                      float_ty: &'ll Type) -> &'ll Value {
 829     // Most integer types, even i128, fit into [-f32::MAX, f32::MAX] after rounding.
 830     // It's only u128 -> f32 that can cause overflows (i.e., should yield infinity).
 831     // LLVM's uitofp produces undef in those cases, so we manually check for that case.
 832     let is_u128_to_f32 = !signed && int_ty.int_width() == 128 && float_ty.float_width() == 32;
 833     if is_u128_to_f32 {
 834         // All inputs greater or equal to (f32::MAX + 0.5 ULP) are rounded to infinity,
 835         // and for everything else LLVM's uitofp works just fine.
 836         use rustc_apfloat::ieee::Single;
 837         use rustc_apfloat::Float;
 838         const MAX_F32_PLUS_HALF_ULP: u128 = ((1 << (Single::PRECISION + 1)) - 1)
 839                                             << (Single::MAX_EXP - Single::PRECISION as i16);
 840         let max = bx.cx().c_uint_big(int_ty, MAX_F32_PLUS_HALF_ULP);
 841         let overflow = bx.icmp(IntPredicate::IntUGE, x, max);
 842         let infinity_bits = bx.cx().c_u32(ieee::Single::INFINITY.to_bits() as u32);
 843         let infinity = consts::bitcast(infinity_bits, float_ty);
 844         bx.select(overflow, infinity, bx.uitofp(x, float_ty))
 845     } else {
 846         if signed {
 847             bx.sitofp(x, float_ty)
 848         } else {
 849             bx.uitofp(x, float_ty)
 850         }
 851     }
 852 }
 853
 854 fn cast_float_to_int(bx: &Builder<'_, 'll, '_>,
 855                      signed: bool,
 856                      x: &'ll Value,
 857                      float_ty: &'ll Type,
 858                      int_ty: &'ll Type) -> &'ll Value {
 859     let fptosui_result = if signed {
 860         bx.fptosi(x, int_ty)
 861     } else {
 862         bx.fptoui(x, int_ty)
 863     };
 864
 865     if !bx.sess().opts.debugging_opts.saturating_float_casts {
 866         return fptosui_result;
 867     }
 868     // LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the
 869     // destination integer type after rounding towards zero. This `undef` value can cause UB in
 870     // safe code (see issue #10184), so we implement a saturating conversion on top of it:
 871     // Semantically, the mathematical value of the input is rounded towards zero to the next
 872     // mathematical integer, and then the result is clamped into the range of the destination
 873     // integer type. Positive and negative infinity are mapped to the maximum and minimum value of
 874     // the destination integer type. NaN is mapped to 0.
 875     //
 876     // Define f_min and f_max as the largest and smallest (finite) floats that are exactly equal to
 877     // a value representable in int_ty.
 878     // They are exactly equal to int_ty::{MIN,MAX} if float_ty has enough significand bits.
 879     // Otherwise, int_ty::MAX must be rounded towards zero, as it is one less than a power of two.
 880     // int_ty::MIN, however, is either zero or a negative power of two and is thus exactly
 881     // representable. Note that this only works if float_ty's exponent range is sufficiently large.
 882     // f16 or 256 bit integers would break this property. Right now the smallest float type is f32
 883     // with exponents ranging up to 127, which is barely enough for i128::MIN = -2^127.
 884     // On the other hand, f_max works even if int_ty::MAX is greater than float_ty::MAX. Because
 885     // we're rounding towards zero, we just get float_ty::MAX (which is always an integer).
 886     // This already happens today with u128::MAX = 2^128 - 1 > f32::MAX.
 887     fn compute_clamp_bounds<F: Float>(signed: bool, int_ty: &Type) -> (u128, u128) {
 888         let rounded_min = F::from_i128_r(int_min(signed, int_ty), Round::TowardZero);
 889         assert_eq!(rounded_min.status, Status::OK);
 890         let rounded_max = F::from_u128_r(int_max(signed, int_ty), Round::TowardZero);
 891         assert!(rounded_max.value.is_finite());
 892         (rounded_min.value.to_bits(), rounded_max.value.to_bits())
 893     }
 894     fn int_max(signed: bool, int_ty: &Type) -> u128 {
 895         let shift_amount = 128 - int_ty.int_width();
 896         if signed {
 897             i128::MAX as u128 >> shift_amount
 898         } else {
 899             u128::MAX >> shift_amount
 900         }
 901     }
 902     fn int_min(signed: bool, int_ty: &Type) -> i128 {
 903         if signed {
 904             i128::MIN >> (128 - int_ty.int_width())
 905         } else {
 906             0
 907         }
 908     }
 909     let float_bits_to_llval = |bits| {
 910         let bits_llval = match float_ty.float_width() {
 911             32 => bx.cx().c_u32(bits as u32),
 912             64 => bx.cx().c_u64(bits as u64),
 913             n => bug!("unsupported float width {}", n),
 914         };
 915         consts::bitcast(bits_llval, float_ty)
 916     };
 917     let (f_min, f_max) = match float_ty.float_width() {
 918         32 => compute_clamp_bounds::<ieee::Single>(signed, int_ty),
 919         64 => compute_clamp_bounds::<ieee::Double>(signed, int_ty),
 920         n => bug!("unsupported float width {}", n),
 921     };
 922     let f_min = float_bits_to_llval(f_min);
 923     let f_max = float_bits_to_llval(f_max);
 924     // To implement saturation, we perform the following steps:
 925     //
 926     // 1. Cast x to an integer with fpto[su]i. This may result in undef.
 927     // 2. Compare x to f_min and f_max, and use the comparison results to select:
 928     //  a) int_ty::MIN if x < f_min or x is NaN
 929     //  b) int_ty::MAX if x > f_max
 930     //  c) the result of fpto[su]i otherwise
 931     // 3. If x is NaN, return 0.0, otherwise return the result of step 2.
 932     //
 933     // This avoids resulting undef because values in range [f_min, f_max] by definition fit into the
 934     // destination type. It creates an undef temporary, but *producing* undef is not UB. Our use of
 935     // undef does not introduce any non-determinism either.
 936     // More importantly, the above procedure correctly implements saturating conversion.
 937     // Proof (sketch):
 938     // If x is NaN, 0 is returned by definition.
 939     // Otherwise, x is finite or infinite and thus can be compared with f_min and f_max.
 940     // This yields three cases to consider:
 941     // (1) if x in [f_min, f_max], the result of fpto[su]i is returned, which agrees with
 942     //     saturating conversion for inputs in that range.
 943     // (2) if x > f_max, then x is larger than int_ty::MAX. This holds even if f_max is rounded
 944     //     (i.e., if f_max < int_ty::MAX) because in those cases, nextUp(f_max) is already larger
 945     //     than int_ty::MAX. Because x is larger than int_ty::MAX, the return value of int_ty::MAX
 946     //     is correct.
 947     // (3) if x < f_min, then x is smaller than int_ty::MIN. As shown earlier, f_min exactly equals
 948     //     int_ty::MIN and therefore the return value of int_ty::MIN is correct.
 949     // QED.
 950
 951     // Step 1 was already performed above.
 952
 953     // Step 2: We use two comparisons and two selects, with %s1 being the result:
 954     //     %less_or_nan = fcmp ult %x, %f_min
 955     //     %greater = fcmp olt %x, %f_max
 956     //     %s0 = select %less_or_nan, int_ty::MIN, %fptosi_result
 957     //     %s1 = select %greater, int_ty::MAX, %s0
 958     // Note that %less_or_nan uses an *unordered* comparison. This comparison is true if the
 959     // operands are not comparable (i.e., if x is NaN). The unordered comparison ensures that s1
 960     // becomes int_ty::MIN if x is NaN.
 961     // Performance note: Unordered comparison can be lowered to a "flipped" comparison and a
 962     // negation, and the negation can be merged into the select. Therefore, it not necessarily any
 963     // more expensive than a ordered ("normal") comparison. Whether these optimizations will be
 964     // performed is ultimately up to the backend, but at least x86 does perform them.
 965     let less_or_nan = bx.fcmp(RealPredicate::RealULT, x, f_min);
 966     let greater = bx.fcmp(RealPredicate::RealOGT, x, f_max);
 967     let int_max = bx.cx().c_uint_big(int_ty, int_max(signed, int_ty));
 968     let int_min = bx.cx().c_uint_big(int_ty, int_min(signed, int_ty) as u128);
 969     let s0 = bx.select(less_or_nan, int_min, fptosui_result);
 970     let s1 = bx.select(greater, int_max, s0);
 971
 972     // Step 3: NaN replacement.
 973     // For unsigned types, the above step already yielded int_ty::MIN == 0 if x is NaN.
 974     // Therefore we only need to execute this step for signed integer types.
 975     if signed {
 976         // LLVM has no isNaN predicate, so we use (x == x) instead
 977         bx.select(bx.fcmp(RealPredicate::RealOEQ, x, x), s1, bx.cx().c_uint(int_ty, 0))
 978     } else {
 979         s1
 980     }
 981 }