src/librustc_trans/trans/mir/rvalue.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use llvm::ValueRef;
  12 use rustc::middle::ty::{self, Ty};
  13 use middle::ty::cast::{CastTy, IntTy};
  14 use rustc::mir::repr as mir;
  15
  16 use trans::asm;
  17 use trans::base;
  18 use trans::common::{self, BlockAndBuilder, Result};
  19 use trans::debuginfo::DebugLoc;
  20 use trans::declare;
  21 use trans::expr;
  22 use trans::adt;
  23 use trans::machine;
  24 use trans::type_::Type;
  25 use trans::type_of;
  26 use trans::tvec;
  27 use trans::Disr;
  28
  29 use super::MirContext;
  30 use super::operand::{OperandRef, OperandValue};
  31 use super::lvalue::LvalueRef;
  32
  33 impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
  34     pub fn trans_rvalue(&mut self,
  35                         bcx: BlockAndBuilder<'bcx, 'tcx>,
  36                         dest: LvalueRef<'tcx>,
  37                         rvalue: &mir::Rvalue<'tcx>)
  38                         -> BlockAndBuilder<'bcx, 'tcx>
  39     {
  40         debug!("trans_rvalue(dest.llval={}, rvalue={:?})",
  41                bcx.val_to_string(dest.llval),
  42                rvalue);
  43
  44         match *rvalue {
  45             mir::Rvalue::Use(ref operand) => {
  46                 self.trans_operand_into(&bcx, dest.llval, operand);
  47                 bcx
  48             }
  49
  50             mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, cast_ty) => {
  51                 if common::type_is_fat_ptr(bcx.tcx(), cast_ty) {
  52                     // into-coerce of a thin pointer to a fat pointer - just
  53                     // use the operand path.
  54                     let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue);
  55                     self.store_operand(&bcx, dest.llval, temp);
  56                     return bcx;
  57                 }
  58
  59                 // Unsize of a nontrivial struct. I would prefer for
  60                 // this to be eliminated by MIR translation, but
  61                 // `CoerceUnsized` can be passed by a where-clause,
  62                 // so the (generic) MIR may not be able to expand it.
  63                 let operand = self.trans_operand(&bcx, operand);
  64                 bcx.with_block(|bcx| {
  65                     match operand.val {
  66                         OperandValue::FatPtr(..) => unreachable!(),
  67                         OperandValue::Immediate(llval) => {
  68                             // unsize from an immediate structure. We don't
  69                             // really need a temporary alloca here, but
  70                             // avoiding it would require us to have
  71                             // `coerce_unsized_into` use extractvalue to
  72                             // index into the struct, and this case isn't
  73                             // important enough for it.
  74                             debug!("trans_rvalue: creating ugly alloca");
  75                             let lltemp = base::alloc_ty(bcx, operand.ty, "__unsize_temp");
  76                             base::store_ty(bcx, llval, lltemp, operand.ty);
  77                             base::coerce_unsized_into(bcx,
  78                                                       lltemp, operand.ty,
  79                                                       dest.llval, cast_ty);
  80                         }
  81                         OperandValue::Ref(llref) => {
  82                             base::coerce_unsized_into(bcx,
  83                                                       llref, operand.ty,
  84                                                       dest.llval, cast_ty);
  85                         }
  86                     }
  87                 });
  88                 bcx
  89             }
  90
  91             mir::Rvalue::Repeat(ref elem, ref count) => {
  92                 let elem = self.trans_operand(&bcx, elem);
  93                 let size = self.trans_constval(&bcx, &count.value, count.ty).immediate();
  94                 bcx.map_block(|block| {
  95                     let base = expr::get_dataptr(block, dest.llval);
  96                     tvec::iter_vec_raw(block, base, elem.ty, size, |block, llslot, _| {
  97                         self.store_operand_direct(block, llslot, elem);
  98                         block
  99                     })
 100                 })
 101             }
 102
 103             mir::Rvalue::Aggregate(ref kind, ref operands) => {
 104                 match *kind {
 105                     mir::AggregateKind::Adt(adt_def, index, _) => {
 106                         let repr = adt::represent_type(bcx.ccx(), dest.ty.to_ty(bcx.tcx()));
 107                         let disr = Disr::from(adt_def.variants[index].disr_val);
 108                         bcx.with_block(|bcx| {
 109                             adt::trans_set_discr(bcx, &repr, dest.llval, Disr::from(disr));
 110                         });
 111                         for (i, operand) in operands.iter().enumerate() {
 112                             let op = self.trans_operand(&bcx, operand);
 113                             // Do not generate stores and GEPis for zero-sized fields.
 114                             if !common::type_is_zero_size(bcx.ccx(), op.ty) {
 115                                 let val = adt::MaybeSizedValue::sized(dest.llval);
 116                                 let lldest_i = bcx.with_block(|bcx| {
 117                                     adt::trans_field_ptr(bcx, &repr, val, disr, i)
 118                                 });
 119                                 self.store_operand(&bcx, lldest_i, op);
 120                             }
 121                         }
 122                     },
 123                     _ => {
 124                         for (i, operand) in operands.iter().enumerate() {
 125                             let op = self.trans_operand(&bcx, operand);
 126                             // Do not generate stores and GEPis for zero-sized fields.
 127                             if !common::type_is_zero_size(bcx.ccx(), op.ty) {
 128                                 // Note: perhaps this should be StructGep, but
 129                                 // note that in some cases the values here will
 130                                 // not be structs but arrays.
 131                                 let dest = bcx.gepi(dest.llval, &[0, i]);
 132                                 self.store_operand(&bcx, dest, op);
 133                             }
 134                         }
 135                     }
 136                 }
 137                 bcx
 138             }
 139
 140             mir::Rvalue::Slice { ref input, from_start, from_end } => {
 141                 let ccx = bcx.ccx();
 142                 let input = self.trans_lvalue(&bcx, input);
 143                 let (llbase, lllen) = bcx.with_block(|bcx| {
 144                     tvec::get_base_and_len(bcx,
 145                                            input.llval,
 146                                            input.ty.to_ty(bcx.tcx()))
 147                 });
 148                 let llbase1 = bcx.gepi(llbase, &[from_start]);
 149                 let adj = common::C_uint(ccx, from_start + from_end);
 150                 let lllen1 = bcx.sub(lllen, adj);
 151                 let (lladdrdest, llmetadest) = bcx.with_block(|bcx| {
 152                     (expr::get_dataptr(bcx, dest.llval), expr::get_meta(bcx, dest.llval))
 153                 });
 154                 bcx.store(llbase1, lladdrdest);
 155                 bcx.store(lllen1, llmetadest);
 156                 bcx
 157             }
 158
 159             mir::Rvalue::InlineAsm(ref inline_asm) => {
 160                 bcx.map_block(|bcx| {
 161                     asm::trans_inline_asm(bcx, inline_asm)
 162                 })
 163             }
 164
 165             _ => {
 166                 assert!(rvalue_creates_operand(rvalue));
 167                 let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue);
 168                 self.store_operand(&bcx, dest.llval, temp);
 169                 bcx
 170             }
 171         }
 172     }
 173
 174     pub fn trans_rvalue_operand(&mut self,
 175                                 bcx: BlockAndBuilder<'bcx, 'tcx>,
 176                                 rvalue: &mir::Rvalue<'tcx>)
 177                                 -> (BlockAndBuilder<'bcx, 'tcx>, OperandRef<'tcx>)
 178     {
 179         assert!(rvalue_creates_operand(rvalue), "cannot trans {:?} to operand", rvalue);
 180
 181         match *rvalue {
 182             mir::Rvalue::Use(ref operand) => {
 183                 let operand = self.trans_operand(&bcx, operand);
 184                 (bcx, operand)
 185             }
 186
 187             mir::Rvalue::Cast(ref kind, ref operand, cast_ty) => {
 188                 let operand = self.trans_operand(&bcx, operand);
 189                 debug!("cast operand is {}", operand.repr(&bcx));
 190                 let cast_ty = bcx.monomorphize(&cast_ty);
 191
 192                 let val = match *kind {
 193                     mir::CastKind::ReifyFnPointer |
 194                     mir::CastKind::UnsafeFnPointer => {
 195                         // these are no-ops at the LLVM level
 196                         operand.val
 197                     }
 198                     mir::CastKind::Unsize => {
 199                         // unsize targets other than to a fat pointer currently
 200                         // can't be operands.
 201                         assert!(common::type_is_fat_ptr(bcx.tcx(), cast_ty));
 202
 203                         match operand.val {
 204                             OperandValue::FatPtr(..) => {
 205                                 // unsize from a fat pointer - this is a
 206                                 // "trait-object-to-supertrait" coercion, for
 207                                 // example,
 208                                 //   &'a fmt::Debug+Send => &'a fmt::Debug,
 209                                 // and is a no-op at the LLVM level
 210                                 operand.val
 211                             }
 212                             OperandValue::Immediate(lldata) => {
 213                                 // "standard" unsize
 214                                 let (lldata, llextra) = bcx.with_block(|bcx| {
 215                                     base::unsize_thin_ptr(bcx, lldata,
 216                                                           operand.ty, cast_ty)
 217                                 });
 218                                 OperandValue::FatPtr(lldata, llextra)
 219                             }
 220                             OperandValue::Ref(_) => {
 221                                 bcx.sess().bug(
 222                                     &format!("by-ref operand {} in trans_rvalue_operand",
 223                                              operand.repr(&bcx)));
 224                             }
 225                         }
 226                     }
 227                     mir::CastKind::Misc if common::type_is_immediate(bcx.ccx(), operand.ty) => {
 228                         debug_assert!(common::type_is_immediate(bcx.ccx(), cast_ty));
 229                         let r_t_in = CastTy::from_ty(operand.ty).expect("bad input type for cast");
 230                         let r_t_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
 231                         let ll_t_in = type_of::arg_type_of(bcx.ccx(), operand.ty);
 232                         let ll_t_out = type_of::arg_type_of(bcx.ccx(), cast_ty);
 233                         let (llval, ll_t_in, signed) = if let CastTy::Int(IntTy::CEnum) = r_t_in {
 234                             let repr = adt::represent_type(bcx.ccx(), operand.ty);
 235                             let llval = operand.immediate();
 236                             let discr = bcx.with_block(|bcx| {
 237                                 adt::trans_get_discr(bcx, &repr, llval, None, true)
 238                             });
 239                             (discr, common::val_ty(discr), adt::is_discr_signed(&repr))
 240                         } else {
 241                             (operand.immediate(), ll_t_in, operand.ty.is_signed())
 242                         };
 243
 244                         let newval = match (r_t_in, r_t_out) {
 245                             (CastTy::Int(_), CastTy::Int(_)) => {
 246                                 let srcsz = ll_t_in.int_width();
 247                                 let dstsz = ll_t_out.int_width();
 248                                 if srcsz == dstsz {
 249                                     bcx.bitcast(llval, ll_t_out)
 250                                 } else if srcsz > dstsz {
 251                                     bcx.trunc(llval, ll_t_out)
 252                                 } else if signed {
 253                                     bcx.sext(llval, ll_t_out)
 254                                 } else {
 255                                     bcx.zext(llval, ll_t_out)
 256                                 }
 257                             }
 258                             (CastTy::Float, CastTy::Float) => {
 259                                 let srcsz = ll_t_in.float_width();
 260                                 let dstsz = ll_t_out.float_width();
 261                                 if dstsz > srcsz {
 262                                     bcx.fpext(llval, ll_t_out)
 263                                 } else if srcsz > dstsz {
 264                                     bcx.fptrunc(llval, ll_t_out)
 265                                 } else {
 266                                     llval
 267                                 }
 268                             }
 269                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
 270                             (CastTy::FnPtr, CastTy::Ptr(_)) |
 271                             (CastTy::RPtr(_), CastTy::Ptr(_)) =>
 272                                 bcx.pointercast(llval, ll_t_out),
 273                             (CastTy::Ptr(_), CastTy::Int(_)) |
 274                             (CastTy::FnPtr, CastTy::Int(_)) =>
 275                                 bcx.ptrtoint(llval, ll_t_out),
 276                             (CastTy::Int(_), CastTy::Ptr(_)) =>
 277                                 bcx.inttoptr(llval, ll_t_out),
 278                             (CastTy::Int(_), CastTy::Float) if signed =>
 279                                 bcx.sitofp(llval, ll_t_out),
 280                             (CastTy::Int(_), CastTy::Float) =>
 281                                 bcx.uitofp(llval, ll_t_out),
 282                             (CastTy::Float, CastTy::Int(IntTy::I)) =>
 283                                 bcx.fptosi(llval, ll_t_out),
 284                             (CastTy::Float, CastTy::Int(_)) =>
 285                                 bcx.fptoui(llval, ll_t_out),
 286                             _ => bcx.ccx().sess().bug(
 287                                 &format!("unsupported cast: {:?} to {:?}", operand.ty, cast_ty)
 288                             )
 289                         };
 290                         OperandValue::Immediate(newval)
 291                     }
 292                     mir::CastKind::Misc => { // Casts from a fat-ptr.
 293                         let ll_cast_ty = type_of::arg_type_of(bcx.ccx(), cast_ty);
 294                         let ll_from_ty = type_of::arg_type_of(bcx.ccx(), operand.ty);
 295                         if let OperandValue::FatPtr(data_ptr, meta_ptr) = operand.val {
 296                             if common::type_is_fat_ptr(bcx.tcx(), cast_ty) {
 297                                 let ll_cft = ll_cast_ty.field_types();
 298                                 let ll_fft = ll_from_ty.field_types();
 299                                 let data_cast = bcx.pointercast(data_ptr, ll_cft[0]);
 300                                 assert_eq!(ll_cft[1].kind(), ll_fft[1].kind());
 301                                 OperandValue::FatPtr(data_cast, meta_ptr)
 302                             } else { // cast to thin-ptr
 303                                 // Cast of fat-ptr to thin-ptr is an extraction of data-ptr and
 304                                 // pointer-cast of that pointer to desired pointer type.
 305                                 let llval = bcx.pointercast(data_ptr, ll_cast_ty);
 306                                 OperandValue::Immediate(llval)
 307                             }
 308                         } else {
 309                             panic!("Unexpected non-FatPtr operand")
 310                         }
 311                     }
 312                 };
 313                 let operand = OperandRef {
 314                     val: val,
 315                     ty: cast_ty
 316                 };
 317                 (bcx, operand)
 318             }
 319
 320             mir::Rvalue::Ref(_, bk, ref lvalue) => {
 321                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 322
 323                 let ty = tr_lvalue.ty.to_ty(bcx.tcx());
 324                 let ref_ty = bcx.tcx().mk_ref(
 325                     bcx.tcx().mk_region(ty::ReStatic),
 326                     ty::TypeAndMut { ty: ty, mutbl: bk.to_mutbl_lossy() }
 327                 );
 328
 329                 // Note: lvalues are indirect, so storing the `llval` into the
 330                 // destination effectively creates a reference.
 331                 let operand = if common::type_is_sized(bcx.tcx(), ty) {
 332                     OperandRef {
 333                         val: OperandValue::Immediate(tr_lvalue.llval),
 334                         ty: ref_ty,
 335                     }
 336                 } else {
 337                     OperandRef {
 338                         val: OperandValue::FatPtr(tr_lvalue.llval,
 339                                                   tr_lvalue.llextra),
 340                         ty: ref_ty,
 341                     }
 342                 };
 343                 (bcx, operand)
 344             }
 345
 346             mir::Rvalue::Len(ref lvalue) => {
 347                 let tr_lvalue = self.trans_lvalue(&bcx, lvalue);
 348                 let operand = OperandRef {
 349                     val: OperandValue::Immediate(self.lvalue_len(&bcx, tr_lvalue)),
 350                     ty: bcx.tcx().types.usize,
 351                 };
 352                 (bcx, operand)
 353             }
 354
 355             mir::Rvalue::BinaryOp(op, ref lhs, ref rhs) => {
 356                 let lhs = self.trans_operand(&bcx, lhs);
 357                 let rhs = self.trans_operand(&bcx, rhs);
 358                 let llresult = if common::type_is_fat_ptr(bcx.tcx(), lhs.ty) {
 359                     match (lhs.val, rhs.val) {
 360                         (OperandValue::FatPtr(lhs_addr, lhs_extra),
 361                          OperandValue::FatPtr(rhs_addr, rhs_extra)) => {
 362                             bcx.with_block(|bcx| {
 363                                 base::compare_fat_ptrs(bcx,
 364                                                        lhs_addr, lhs_extra,
 365                                                        rhs_addr, rhs_extra,
 366                                                        lhs.ty, op.to_hir_binop(),
 367                                                        DebugLoc::None)
 368                             })
 369                         }
 370                         _ => unreachable!()
 371                     }
 372
 373                 } else {
 374                     self.trans_scalar_binop(&bcx, op,
 375                                             lhs.immediate(), rhs.immediate(),
 376                                             lhs.ty)
 377                 };
 378                 let operand = OperandRef {
 379                     val: OperandValue::Immediate(llresult),
 380                     ty: self.mir.binop_ty(bcx.tcx(), op, lhs.ty, rhs.ty),
 381                 };
 382                 (bcx, operand)
 383             }
 384
 385             mir::Rvalue::UnaryOp(op, ref operand) => {
 386                 let operand = self.trans_operand(&bcx, operand);
 387                 let lloperand = operand.immediate();
 388                 let is_float = operand.ty.is_fp();
 389                 let llval = match op {
 390                     mir::UnOp::Not => bcx.not(lloperand),
 391                     mir::UnOp::Neg => if is_float {
 392                         bcx.fneg(lloperand)
 393                     } else {
 394                         bcx.neg(lloperand)
 395                     }
 396                 };
 397                 (bcx, OperandRef {
 398                     val: OperandValue::Immediate(llval),
 399                     ty: operand.ty,
 400                 })
 401             }
 402
 403             mir::Rvalue::Box(content_ty) => {
 404                 let content_ty: Ty<'tcx> = bcx.monomorphize(&content_ty);
 405                 let llty = type_of::type_of(bcx.ccx(), content_ty);
 406                 let llsize = machine::llsize_of(bcx.ccx(), llty);
 407                 let align = type_of::align_of(bcx.ccx(), content_ty);
 408                 let llalign = common::C_uint(bcx.ccx(), align);
 409                 let llty_ptr = llty.ptr_to();
 410                 let box_ty = bcx.tcx().mk_box(content_ty);
 411                 let mut llval = None;
 412                 let bcx = bcx.map_block(|bcx| {
 413                     let Result { bcx, val } = base::malloc_raw_dyn(bcx,
 414                                                                    llty_ptr,
 415                                                                    box_ty,
 416                                                                    llsize,
 417                                                                    llalign,
 418                                                                    DebugLoc::None);
 419                     llval = Some(val);
 420                     bcx
 421                 });
 422                 let operand = OperandRef {
 423                     val: OperandValue::Immediate(llval.unwrap()),
 424                     ty: box_ty,
 425                 };
 426                 (bcx, operand)
 427             }
 428
 429             mir::Rvalue::Repeat(..) |
 430             mir::Rvalue::Aggregate(..) |
 431             mir::Rvalue::Slice { .. } |
 432             mir::Rvalue::InlineAsm(..) => {
 433                 bcx.tcx().sess.bug(&format!("cannot generate operand from rvalue {:?}", rvalue));
 434             }
 435         }
 436     }
 437
 438     pub fn trans_scalar_binop(&mut self,
 439                               bcx: &BlockAndBuilder<'bcx, 'tcx>,
 440                               op: mir::BinOp,
 441                               lhs: ValueRef,
 442                               rhs: ValueRef,
 443                               input_ty: Ty<'tcx>) -> ValueRef {
 444         let is_float = input_ty.is_fp();
 445         let is_signed = input_ty.is_signed();
 446         match op {
 447             mir::BinOp::Add => if is_float {
 448                 bcx.fadd(lhs, rhs)
 449             } else {
 450                 bcx.add(lhs, rhs)
 451             },
 452             mir::BinOp::Sub => if is_float {
 453                 bcx.fsub(lhs, rhs)
 454             } else {
 455                 bcx.sub(lhs, rhs)
 456             },
 457             mir::BinOp::Mul => if is_float {
 458                 bcx.fmul(lhs, rhs)
 459             } else {
 460                 bcx.mul(lhs, rhs)
 461             },
 462             mir::BinOp::Div => if is_float {
 463                 bcx.fdiv(lhs, rhs)
 464             } else if is_signed {
 465                 bcx.sdiv(lhs, rhs)
 466             } else {
 467                 bcx.udiv(lhs, rhs)
 468             },
 469             mir::BinOp::Rem => if is_float {
 470                 // LLVM currently always lowers the `frem` instructions appropriate
 471                 // library calls typically found in libm. Notably f64 gets wired up
 472                 // to `fmod` and f32 gets wired up to `fmodf`. Inconveniently for
 473                 // us, 32-bit MSVC does not actually have a `fmodf` symbol, it's
 474                 // instead just an inline function in a header that goes up to a
 475                 // f64, uses `fmod`, and then comes back down to a f32.
 476                 //
 477                 // Although LLVM knows that `fmodf` doesn't exist on MSVC, it will
 478                 // still unconditionally lower frem instructions over 32-bit floats
 479                 // to a call to `fmodf`. To work around this we special case MSVC
 480                 // 32-bit float rem instructions and instead do the call out to
 481                 // `fmod` ourselves.
 482                 //
 483                 // Note that this is currently duplicated with src/libcore/ops.rs
 484                 // which does the same thing, and it would be nice to perhaps unify
 485                 // these two implementations one day! Also note that we call `fmod`
 486                 // for both 32 and 64-bit floats because if we emit any FRem
 487                 // instruction at all then LLVM is capable of optimizing it into a
 488                 // 32-bit FRem (which we're trying to avoid).
 489                 let tcx = bcx.tcx();
 490                 let use_fmod = tcx.sess.target.target.options.is_like_msvc &&
 491                     tcx.sess.target.target.arch == "x86";
 492                 if use_fmod {
 493                     let f64t = Type::f64(bcx.ccx());
 494                     let fty = Type::func(&[f64t, f64t], &f64t);
 495                     let llfn = declare::declare_cfn(bcx.ccx(), "fmod", fty,
 496                                                     tcx.types.f64);
 497                     if input_ty == tcx.types.f32 {
 498                         let lllhs = bcx.fpext(lhs, f64t);
 499                         let llrhs = bcx.fpext(rhs, f64t);
 500                         let llres = bcx.call(llfn, &[lllhs, llrhs], None, None);
 501                         bcx.fptrunc(llres, Type::f32(bcx.ccx()))
 502                     } else {
 503                         bcx.call(llfn, &[lhs, rhs], None, None)
 504                     }
 505                 } else {
 506                     bcx.frem(lhs, rhs)
 507                 }
 508             } else if is_signed {
 509                 bcx.srem(lhs, rhs)
 510             } else {
 511                 bcx.urem(lhs, rhs)
 512             },
 513             mir::BinOp::BitOr => bcx.or(lhs, rhs),
 514             mir::BinOp::BitAnd => bcx.and(lhs, rhs),
 515             mir::BinOp::BitXor => bcx.xor(lhs, rhs),
 516             mir::BinOp::Shl => {
 517                 bcx.with_block(|bcx| {
 518                     common::build_unchecked_lshift(bcx,
 519                                                    lhs,
 520                                                    rhs,
 521                                                    DebugLoc::None)
 522                 })
 523             }
 524             mir::BinOp::Shr => {
 525                 bcx.with_block(|bcx| {
 526                     common::build_unchecked_rshift(bcx,
 527                                                    input_ty,
 528                                                    lhs,
 529                                                    rhs,
 530                                                    DebugLoc::None)
 531                 })
 532             }
 533             mir::BinOp::Eq | mir::BinOp::Lt | mir::BinOp::Gt |
 534             mir::BinOp::Ne | mir::BinOp::Le | mir::BinOp::Ge => {
 535                 bcx.with_block(|bcx| {
 536                     base::compare_scalar_types(bcx, lhs, rhs, input_ty,
 537                                                op.to_hir_binop(), DebugLoc::None)
 538                 })
 539             }
 540         }
 541     }
 542 }
 543
 544 pub fn rvalue_creates_operand<'tcx>(rvalue: &mir::Rvalue<'tcx>) -> bool {
 545     match *rvalue {
 546         mir::Rvalue::Use(..) | // (*)
 547         mir::Rvalue::Ref(..) |
 548         mir::Rvalue::Len(..) |
 549         mir::Rvalue::Cast(..) | // (*)
 550         mir::Rvalue::BinaryOp(..) |
 551         mir::Rvalue::UnaryOp(..) |
 552         mir::Rvalue::Box(..) =>
 553             true,
 554         mir::Rvalue::Repeat(..) |
 555         mir::Rvalue::Aggregate(..) |
 556         mir::Rvalue::Slice { .. } |
 557         mir::Rvalue::InlineAsm(..) =>
 558             false,
 559     }
 560
 561     // (*) this is only true if the type is suitable
 562 }