src/base.rs

   1 use crate::prelude::*;
   2
   3 struct PrintOnPanic<F: Fn() -> String>(F);
   4 impl<F: Fn() -> String> Drop for PrintOnPanic<F> {
   5     fn drop(&mut self) {
   6         if ::std::thread::panicking() {
   7             println!("{}", (self.0)());
   8         }
   9     }
  10 }
  11
  12 pub fn trans_mono_item<'a, 'clif, 'tcx: 'a, B: Backend + 'static>(
  13     cx: &mut crate::CodegenCx<'a, 'clif, 'tcx, B>,
  14     mono_item: MonoItem<'tcx>,
  15     linkage: Linkage,
  16 ) {
  17     let tcx = cx.tcx;
  18     match mono_item {
  19         MonoItem::Fn(inst) => {
  20             let _inst_guard =
  21                 PrintOnPanic(|| format!("{:?} {}", inst, tcx.symbol_name(inst).as_str()));
  22             debug_assert!(!inst.substs.needs_infer());
  23             let _mir_guard = PrintOnPanic(|| {
  24                 match inst.def {
  25                     InstanceDef::Item(_)
  26                     | InstanceDef::DropGlue(_, _)
  27                     | InstanceDef::Virtual(_, _)
  28                         if inst.def_id().krate == LOCAL_CRATE =>
  29                     {
  30                         let mut mir = ::std::io::Cursor::new(Vec::new());
  31                         crate::rustc_mir::util::write_mir_pretty(
  32                             tcx,
  33                             Some(inst.def_id()),
  34                             &mut mir,
  35                         )
  36                         .unwrap();
  37                         String::from_utf8(mir.into_inner()).unwrap()
  38                     }
  39                     _ => {
  40                         // FIXME fix write_mir_pretty for these instances
  41                         format!("{:#?}", tcx.instance_mir(inst.def))
  42                     }
  43                 }
  44             });
  45
  46             trans_fn(cx, inst, linkage);
  47         }
  48         MonoItem::Static(def_id) => {
  49             crate::constant::codegen_static(&mut cx.ccx, def_id);
  50         }
  51         MonoItem::GlobalAsm(node_id) => tcx
  52             .sess
  53             .fatal(&format!("Unimplemented global asm mono item {:?}", node_id)),
  54     }
  55 }
  56
  57 fn trans_fn<'a, 'clif, 'tcx: 'a, B: Backend + 'static>(
  58     cx: &mut crate::CodegenCx<'a, 'clif, 'tcx, B>,
  59     instance: Instance<'tcx>,
  60     linkage: Linkage,
  61 ) {
  62     let tcx = cx.tcx;
  63
  64     // Step 1. Get mir
  65     let mir = tcx.instance_mir(instance.def);
  66
  67     // Step 2. Declare function
  68     let (name, sig) = get_function_name_and_sig(tcx, instance, false);
  69     let func_id = cx.module
  70         .declare_function(&name, linkage, &sig)
  71         .unwrap();
  72     let mut debug_context = cx.debug_context.as_mut().map(|debug_context| FunctionDebugContext::new(
  73         tcx,
  74         debug_context,
  75         mir,
  76         &name,
  77         &sig,
  78     ));
  79
  80     // Step 3. Make FunctionBuilder
  81     let mut func = Function::with_name_signature(ExternalName::user(0, 0), sig);
  82     let mut func_ctx = FunctionBuilderContext::new();
  83     let mut bcx = FunctionBuilder::new(&mut func, &mut func_ctx);
  84
  85     // Step 4. Predefine ebb's
  86     let start_ebb = bcx.create_ebb();
  87     let mut ebb_map: HashMap<BasicBlock, Ebb> = HashMap::new();
  88     for (bb, _bb_data) in mir.basic_blocks().iter_enumerated() {
  89         ebb_map.insert(bb, bcx.create_ebb());
  90     }
  91
  92     // Step 5. Make FunctionCx
  93     let pointer_type = cx.module.target_config().pointer_type();
  94     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  95
  96     let mut fx = FunctionCx {
  97         tcx,
  98         module: cx.module,
  99         pointer_type,
 100
 101         instance,
 102         mir,
 103
 104         bcx,
 105         ebb_map,
 106         local_map: HashMap::new(),
 107
 108         clif_comments,
 109         constants: &mut cx.ccx,
 110         caches: &mut cx.caches,
 111         source_info_set: indexmap::IndexSet::new(),
 112     };
 113
 114     // Step 6. Codegen function
 115     with_unimpl_span(fx.mir.span, || {
 116         crate::abi::codegen_fn_prelude(&mut fx, start_ebb);
 117         codegen_fn_content(&mut fx);
 118     });
 119     let source_info_set = fx.source_info_set.clone();
 120
 121     // Step 7. Write function to file for debugging
 122     #[cfg(debug_assertions)]
 123     fx.write_clif_file();
 124
 125     // Step 8. Verify function
 126     verify_func(tcx, fx.clif_comments, &func);
 127
 128     // Step 9. Define function
 129     cx.caches.context.func = func;
 130     cx.module
 131         .define_function_peek_compiled(func_id, &mut cx.caches.context, |size, context, isa| {
 132             debug_context.as_mut().map(|x| x.define(tcx, size, context, isa, &source_info_set));
 133         })
 134         .unwrap();
 135     //let module = &mut cx.module;
 136     //let caches = &cx.caches;
 137     cx.caches.context.clear();
 138 }
 139
 140 fn verify_func(tcx: TyCtxt, writer: crate::pretty_clif::CommentWriter, func: &Function) {
 141     let flags = settings::Flags::new(settings::builder());
 142     match ::cranelift::codegen::verify_function(&func, &flags) {
 143         Ok(_) => {}
 144         Err(err) => {
 145             tcx.sess.err(&format!("{:?}", err));
 146             let pretty_error = ::cranelift::codegen::print_errors::pretty_verifier_error(
 147                 &func,
 148                 None,
 149                 Some(Box::new(&writer)),
 150                 err,
 151             );
 152             tcx.sess
 153                 .fatal(&format!("cranelift verify error:\n{}", pretty_error));
 154         }
 155     }
 156 }
 157
 158 fn codegen_fn_content<'a, 'tcx: 'a>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>) {
 159     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 160         if bb_data.is_cleanup {
 161             // Unwinding after panicking is not supported
 162             continue;
 163         }
 164
 165         let ebb = fx.get_ebb(bb);
 166         fx.bcx.switch_to_block(ebb);
 167
 168         fx.bcx.ins().nop();
 169         for stmt in &bb_data.statements {
 170             fx.set_debug_loc(stmt.source_info);
 171             trans_stmt(fx, ebb, stmt);
 172         }
 173
 174         #[cfg(debug_assertions)]
 175         {
 176             let mut terminator_head = "\n".to_string();
 177             bb_data
 178                 .terminator()
 179                 .kind
 180                 .fmt_head(&mut terminator_head)
 181                 .unwrap();
 182             let inst = fx.bcx.func.layout.last_inst(ebb).unwrap();
 183             fx.add_comment(inst, terminator_head);
 184         }
 185
 186         fx.set_debug_loc(bb_data.terminator().source_info);
 187
 188         match &bb_data.terminator().kind {
 189             TerminatorKind::Goto { target } => {
 190                 let ebb = fx.get_ebb(*target);
 191                 fx.bcx.ins().jump(ebb, &[]);
 192             }
 193             TerminatorKind::Return => {
 194                 crate::abi::codegen_return(fx);
 195             }
 196             TerminatorKind::Assert {
 197                 cond,
 198                 expected,
 199                 msg: _,
 200                 target,
 201                 cleanup: _,
 202             } => {
 203                 let cond = trans_operand(fx, cond).load_scalar(fx);
 204                 // TODO HACK brz/brnz for i8/i16 is not yet implemented
 205                 let cond = fx.bcx.ins().uextend(types::I32, cond);
 206                 let target = fx.get_ebb(*target);
 207                 if *expected {
 208                     fx.bcx.ins().brnz(cond, target, &[]);
 209                 } else {
 210                     fx.bcx.ins().brz(cond, target, &[]);
 211                 };
 212                 trap_panic(&mut fx.bcx);
 213             }
 214
 215             TerminatorKind::SwitchInt {
 216                 discr,
 217                 switch_ty: _,
 218                 values,
 219                 targets,
 220             } => {
 221                 let discr = trans_operand(fx, discr).load_scalar(fx);
 222                 let mut switch = ::cranelift::frontend::Switch::new();
 223                 for (i, value) in values.iter().enumerate() {
 224                     let ebb = fx.get_ebb(targets[i]);
 225                     switch.set_entry(*value as u64, ebb);
 226                 }
 227                 let otherwise_ebb = fx.get_ebb(targets[targets.len() - 1]);
 228                 switch.emit(&mut fx.bcx, discr, otherwise_ebb);
 229             }
 230             TerminatorKind::Call {
 231                 func,
 232                 args,
 233                 destination,
 234                 cleanup: _,
 235                 from_hir_call: _,
 236             } => {
 237                 crate::abi::codegen_terminator_call(fx, func, args, destination);
 238             }
 239             TerminatorKind::Resume | TerminatorKind::Abort | TerminatorKind::Unreachable => {
 240                 trap_unreachable(&mut fx.bcx);
 241             }
 242             TerminatorKind::Yield { .. }
 243             | TerminatorKind::FalseEdges { .. }
 244             | TerminatorKind::FalseUnwind { .. }
 245             | TerminatorKind::DropAndReplace { .. }
 246             | TerminatorKind::GeneratorDrop => {
 247                 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
 248             }
 249             TerminatorKind::Drop {
 250                 location,
 251                 target,
 252                 unwind: _,
 253             } => {
 254                 let ty = location.ty(fx.mir, fx.tcx).to_ty(fx.tcx);
 255                 let ty = fx.monomorphize(&ty);
 256                 let drop_fn = crate::rustc_mir::monomorphize::resolve_drop_in_place(fx.tcx, ty);
 257
 258                 if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 259                     // we don't actually need to drop anything
 260                 } else {
 261                     let drop_place = trans_place(fx, location);
 262                     let drop_fn_ty = drop_fn.ty(fx.tcx);
 263                     match ty.sty {
 264                         ty::Dynamic(..) => {
 265                             crate::abi::codegen_drop(fx, drop_place, drop_fn_ty);
 266                         }
 267                         _ => {
 268                             let arg_place = CPlace::new_stack_slot(
 269                                 fx,
 270                                 fx.tcx.mk_ref(
 271                                     &ty::RegionKind::ReErased,
 272                                     TypeAndMut {
 273                                         ty,
 274                                         mutbl: crate::rustc::hir::Mutability::MutMutable,
 275                                     },
 276                                 ),
 277                             );
 278                             drop_place.write_place_ref(fx, arg_place);
 279                             let arg_value = arg_place.to_cvalue(fx);
 280                             crate::abi::codegen_call_inner(
 281                                 fx,
 282                                 None,
 283                                 drop_fn_ty,
 284                                 vec![arg_value],
 285                                 None,
 286                             );
 287                         }
 288                     }
 289                 }
 290
 291                 let target_ebb = fx.get_ebb(*target);
 292                 fx.bcx.ins().jump(target_ebb, &[]);
 293             }
 294         };
 295     }
 296
 297     fx.bcx.seal_all_blocks();
 298     fx.bcx.finalize();
 299 }
 300
 301 fn trans_stmt<'a, 'tcx: 'a>(
 302     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 303     cur_ebb: Ebb,
 304     stmt: &Statement<'tcx>,
 305 ) {
 306     let _print_guard = PrintOnPanic(|| format!("stmt {:?}", stmt));
 307
 308     fx.set_debug_loc(stmt.source_info);
 309
 310     #[cfg(debug_assertions)]
 311     match &stmt.kind {
 312         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 313         _ => {
 314             let inst = fx.bcx.func.layout.last_inst(cur_ebb).unwrap();
 315             fx.add_comment(inst, format!("{:?}", stmt));
 316         }
 317     }
 318
 319     match &stmt.kind {
 320         StatementKind::SetDiscriminant {
 321             place,
 322             variant_index,
 323         } => {
 324             let place = trans_place(fx, place);
 325             let layout = place.layout();
 326             if layout.for_variant(&*fx, *variant_index).abi == layout::Abi::Uninhabited {
 327                 return;
 328             }
 329             match layout.variants {
 330                 layout::Variants::Single { index } => {
 331                     assert_eq!(index, *variant_index);
 332                 }
 333                 layout::Variants::Tagged { .. } => {
 334                     let ptr = place.place_field(fx, mir::Field::new(0));
 335                     let to = layout
 336                         .ty
 337                         .ty_adt_def()
 338                         .unwrap()
 339                         .discriminant_for_variant(fx.tcx, *variant_index)
 340                         .val;
 341                     let discr = CValue::const_val(fx, ptr.layout().ty, to as u64 as i64);
 342                     ptr.write_cvalue(fx, discr);
 343                 }
 344                 layout::Variants::NicheFilling {
 345                     dataful_variant,
 346                     ref niche_variants,
 347                     niche_start,
 348                     ..
 349                 } => {
 350                     if *variant_index != dataful_variant {
 351                         let niche = place.place_field(fx, mir::Field::new(0));
 352                         //let niche_llty = niche.layout.immediate_llvm_type(bx.cx);
 353                         let niche_value =
 354                             ((variant_index.as_u32() - niche_variants.start().as_u32()) as u128)
 355                                 .wrapping_add(niche_start);
 356                         // FIXME(eddyb) Check the actual primitive type here.
 357                         let niche_llval = if niche_value == 0 {
 358                             CValue::const_val(fx, niche.layout().ty, 0)
 359                         } else {
 360                             CValue::const_val(fx, niche.layout().ty, niche_value as u64 as i64)
 361                         };
 362                         niche.write_cvalue(fx, niche_llval);
 363                     }
 364                 }
 365             }
 366         }
 367         StatementKind::Assign(to_place, rval) => {
 368             let lval = trans_place(fx, to_place);
 369             let dest_layout = lval.layout();
 370             match &**rval {
 371                 Rvalue::Use(operand) => {
 372                     let val = trans_operand(fx, operand);
 373                     lval.write_cvalue(fx, val);
 374                 }
 375                 Rvalue::Ref(_, _, place) => {
 376                     let place = trans_place(fx, place);
 377                     place.write_place_ref(fx, lval);
 378                 }
 379                 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
 380                     let ty = fx.monomorphize(&lhs.ty(fx.mir, fx.tcx));
 381                     let lhs = trans_operand(fx, lhs);
 382                     let rhs = trans_operand(fx, rhs);
 383
 384                     let res = match ty.sty {
 385                         ty::Bool => trans_bool_binop(fx, *bin_op, lhs, rhs, lval.layout().ty),
 386                         ty::Uint(_) => {
 387                             trans_int_binop(fx, *bin_op, lhs, rhs, lval.layout().ty, false)
 388                         }
 389                         ty::Int(_) => {
 390                             trans_int_binop(fx, *bin_op, lhs, rhs, lval.layout().ty, true)
 391                         }
 392                         ty::Float(_) => trans_float_binop(fx, *bin_op, lhs, rhs, lval.layout().ty),
 393                         ty::Char => trans_char_binop(fx, *bin_op, lhs, rhs, lval.layout().ty),
 394                         ty::RawPtr(..) => trans_ptr_binop(fx, *bin_op, lhs, rhs, lval.layout().ty),
 395                         ty::FnPtr(..) => trans_ptr_binop(fx, *bin_op, lhs, rhs, lval.layout().ty),
 396                         _ => unimplemented!("binop {:?} for {:?}", bin_op, ty),
 397                     };
 398                     lval.write_cvalue(fx, res);
 399                 }
 400                 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
 401                     let ty = fx.monomorphize(&lhs.ty(fx.mir, fx.tcx));
 402                     let lhs = trans_operand(fx, lhs);
 403                     let rhs = trans_operand(fx, rhs);
 404
 405                     let res = match ty.sty {
 406                         ty::Uint(_) => {
 407                             trans_checked_int_binop(fx, *bin_op, lhs, rhs, lval.layout().ty, false)
 408                         }
 409                         ty::Int(_) => {
 410                             trans_checked_int_binop(fx, *bin_op, lhs, rhs, lval.layout().ty, true)
 411                         }
 412                         _ => unimplemented!("checked binop {:?} for {:?}", bin_op, ty),
 413                     };
 414                     lval.write_cvalue(fx, res);
 415                 }
 416                 Rvalue::UnaryOp(un_op, operand) => {
 417                     let operand = trans_operand(fx, operand);
 418                     let layout = operand.layout();
 419                     let val = operand.load_scalar(fx);
 420                     let res = match un_op {
 421                         UnOp::Not => {
 422                             match layout.ty.sty {
 423                                 ty::Bool => {
 424                                     let val = fx.bcx.ins().uextend(types::I32, val); // WORKAROUND for CraneStation/cranelift#466
 425                                     let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 426                                     fx.bcx.ins().bint(types::I8, res)
 427                                 }
 428                                 ty::Uint(_) | ty::Int(_) => fx.bcx.ins().bnot(val),
 429                                 _ => unimplemented!("un op Not for {:?}", layout.ty),
 430                             }
 431                         }
 432                         UnOp::Neg => match layout.ty.sty {
 433                             ty::Int(_) => {
 434                                 let clif_ty = fx.clif_type(layout.ty).unwrap();
 435                                 let zero = fx.bcx.ins().iconst(clif_ty, 0);
 436                                 fx.bcx.ins().isub(zero, val)
 437                             }
 438                             ty::Float(_) => fx.bcx.ins().fneg(val),
 439                             _ => unimplemented!("un op Neg for {:?}", layout.ty),
 440                         },
 441                     };
 442                     lval.write_cvalue(fx, CValue::ByVal(res, layout));
 443                 }
 444                 Rvalue::Cast(CastKind::ReifyFnPointer, operand, ty) => {
 445                     let layout = fx.layout_of(ty);
 446                     match fx.monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx)).sty {
 447                         ty::FnDef(def_id, substs) => {
 448                             let func_ref = fx.get_function_ref(
 449                                 Instance::resolve(fx.tcx, ParamEnv::reveal_all(), def_id, substs).unwrap(),
 450                             );
 451                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 452                             lval.write_cvalue(fx, CValue::ByVal(func_addr, layout));
 453                         }
 454                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", ty),
 455                     }
 456                 }
 457                 Rvalue::Cast(CastKind::UnsafeFnPointer, operand, ty) => {
 458                     let operand = trans_operand(fx, operand);
 459                     let layout = fx.layout_of(ty);
 460                     lval.write_cvalue(fx, operand.unchecked_cast_to(layout));
 461                 }
 462                 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
 463                     let operand = trans_operand(fx, operand);
 464                     let from_ty = operand.layout().ty;
 465                     match (&from_ty.sty, &to_ty.sty) {
 466                         (ty::Ref(..), ty::Ref(..))
 467                         | (ty::Ref(..), ty::RawPtr(..))
 468                         | (ty::RawPtr(..), ty::Ref(..))
 469                         | (ty::RawPtr(..), ty::RawPtr(..))
 470                         | (ty::FnPtr(..), ty::RawPtr(..)) => {
 471                             lval.write_cvalue(fx, operand.unchecked_cast_to(dest_layout));
 472                         }
 473                         (ty::RawPtr(..), ty::Uint(_))
 474                         | (ty::RawPtr(..), ty::Int(_))
 475                         | (ty::FnPtr(..), ty::Uint(_))
 476                             if to_ty.sty == fx.tcx.types.usize.sty
 477                                 || to_ty.sty == fx.tcx.types.isize.sty
 478                                 || fx.clif_type(to_ty).unwrap() == pointer_ty(fx.tcx) =>
 479                         {
 480                             lval.write_cvalue(fx, operand.unchecked_cast_to(dest_layout));
 481                         }
 482                         (ty::Uint(_), ty::RawPtr(..)) if from_ty.sty == fx.tcx.types.usize.sty => {
 483                             lval.write_cvalue(fx, operand.unchecked_cast_to(dest_layout));
 484                         }
 485                         (ty::Char, ty::Uint(_))
 486                         | (ty::Uint(_), ty::Char)
 487                         | (ty::Uint(_), ty::Int(_))
 488                         | (ty::Uint(_), ty::Uint(_)) => {
 489                             let from = operand.load_scalar(fx);
 490                             let res = crate::common::clif_intcast(
 491                                 fx,
 492                                 from,
 493                                 fx.clif_type(to_ty).unwrap(),
 494                                 false,
 495                             );
 496                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 497                         }
 498                         (ty::Int(_), ty::Int(_)) | (ty::Int(_), ty::Uint(_)) => {
 499                             let from = operand.load_scalar(fx);
 500                             let res = crate::common::clif_intcast(
 501                                 fx,
 502                                 from,
 503                                 fx.clif_type(to_ty).unwrap(),
 504                                 true,
 505                             );
 506                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 507                         }
 508                         (ty::Float(from_flt), ty::Float(to_flt)) => {
 509                             let from = operand.load_scalar(fx);
 510                             let res = match (from_flt, to_flt) {
 511                                 (FloatTy::F32, FloatTy::F64) => {
 512                                     fx.bcx.ins().fpromote(types::F64, from)
 513                                 }
 514                                 (FloatTy::F64, FloatTy::F32) => {
 515                                     fx.bcx.ins().fdemote(types::F32, from)
 516                                 }
 517                                 _ => from,
 518                             };
 519                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 520                         }
 521                         (ty::Float(_), ty::Int(_)) => {
 522                             let from = operand.load_scalar(fx);
 523                             let i_type = fx.clif_type(to_ty).unwrap();
 524                             let res = fx.bcx.ins().fcvt_to_sint_sat(i_type, from);
 525                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 526                         }
 527                         (ty::Float(_), ty::Uint(_)) => {
 528                             let from = operand.load_scalar(fx);
 529                             let i_type = fx.clif_type(to_ty).unwrap();
 530                             let res = fx.bcx.ins().fcvt_to_uint_sat(i_type, from);
 531                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 532                         }
 533                         (ty::Int(_), ty::Float(_)) => {
 534                             let from_ty = fx.clif_type(from_ty).unwrap();
 535                             let from = operand.load_scalar(fx);
 536                             // FIXME missing encoding for fcvt_from_sint.f32.i8
 537                             let from = if from_ty == types::I8 || from_ty == types::I16 {
 538                                 fx.bcx.ins().sextend(types::I32, from)
 539                             } else {
 540                                 from
 541                             };
 542                             let f_type = fx.clif_type(to_ty).unwrap();
 543                             let res = fx.bcx.ins().fcvt_from_sint(f_type, from);
 544                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 545                         }
 546                         (ty::Uint(_), ty::Float(_)) => {
 547                             let from_ty = fx.clif_type(from_ty).unwrap();
 548                             let from = operand.load_scalar(fx);
 549                             // FIXME missing encoding for fcvt_from_uint.f32.i8
 550                             let from = if from_ty == types::I8 || from_ty == types::I16 {
 551                                 fx.bcx.ins().uextend(types::I32, from)
 552                             } else {
 553                                 from
 554                             };
 555                             let f_type = fx.clif_type(to_ty).unwrap();
 556                             let res = fx.bcx.ins().fcvt_from_uint(f_type, from);
 557                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 558                         }
 559                         (ty::Bool, ty::Uint(_)) | (ty::Bool, ty::Int(_)) => {
 560                             let to_ty = fx.clif_type(to_ty).unwrap();
 561                             let from = operand.load_scalar(fx);
 562                             let res = if to_ty != types::I8 {
 563                                 fx.bcx.ins().uextend(to_ty, from)
 564                             } else {
 565                                 from
 566                             };
 567                             lval.write_cvalue(fx, CValue::ByVal(res, dest_layout));
 568                         }
 569                         (ty::Adt(adt_def, _substs), ty::Uint(_)) | (ty::Adt(adt_def, _substs), ty::Int(_)) if adt_def.is_enum() => {
 570                             let discr = trans_get_discriminant(fx, operand, fx.layout_of(to_ty));
 571                             lval.write_cvalue(fx, discr);
 572                         }
 573                         _ => unimpl!("rval misc {:?} {:?}", from_ty, to_ty),
 574                     }
 575                 }
 576                 Rvalue::Cast(CastKind::ClosureFnPointer, operand, ty) => {
 577                     unimplemented!("rval closure_fn_ptr {:?} {:?}", operand, ty)
 578                 }
 579                 Rvalue::Cast(CastKind::Unsize, operand, _ty) => {
 580                     let operand = trans_operand(fx, operand);
 581                     operand.unsize_value(fx, lval);
 582                 }
 583                 Rvalue::Discriminant(place) => {
 584                     let place = trans_place(fx, place).to_cvalue(fx);
 585                     let discr = trans_get_discriminant(fx, place, dest_layout);
 586                     lval.write_cvalue(fx, discr);
 587                 }
 588                 Rvalue::Repeat(operand, times) => {
 589                     let operand = trans_operand(fx, operand);
 590                     for i in 0..*times {
 591                         let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 592                         let to = lval.place_index(fx, index);
 593                         to.write_cvalue(fx, operand);
 594                     }
 595                 }
 596                 Rvalue::Len(place) => {
 597                     let place = trans_place(fx, place);
 598                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 599                     let len = codegen_array_len(fx, place);
 600                     lval.write_cvalue(fx, CValue::ByVal(len, usize_layout));
 601                 }
 602                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 603                     use rustc::middle::lang_items::ExchangeMallocFnLangItem;
 604
 605                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 606                     let layout = fx.layout_of(content_ty);
 607                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 608                     let llalign = fx
 609                         .bcx
 610                         .ins()
 611                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 612                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 613
 614                     // Allocate space:
 615                     let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
 616                         Ok(id) => id,
 617                         Err(s) => {
 618                             fx.tcx
 619                                 .sess
 620                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 621                         }
 622                     };
 623                     let instance = ty::Instance::mono(fx.tcx, def_id);
 624                     let func_ref = fx.get_function_ref(instance);
 625                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 626                     let ptr = fx.bcx.inst_results(call)[0];
 627                     lval.write_cvalue(fx, CValue::ByVal(ptr, box_layout));
 628                 }
 629                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 630                     assert!(lval
 631                         .layout()
 632                         .ty
 633                         .is_sized(fx.tcx.at(DUMMY_SP), ParamEnv::reveal_all()));
 634                     let ty_size = fx.layout_of(ty).size.bytes();
 635                     let val = CValue::const_val(fx, fx.tcx.types.usize, ty_size as i64);
 636                     lval.write_cvalue(fx, val);
 637                 }
 638                 Rvalue::Aggregate(kind, operands) => match **kind {
 639                     AggregateKind::Array(_ty) => {
 640                         for (i, operand) in operands.into_iter().enumerate() {
 641                             let operand = trans_operand(fx, operand);
 642                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 643                             let to = lval.place_index(fx, index);
 644                             to.write_cvalue(fx, operand);
 645                         }
 646                     }
 647                     _ => unimpl!("shouldn't exist at trans {:?}", rval),
 648                 },
 649             }
 650         }
 651         StatementKind::StorageLive(_)
 652         | StatementKind::StorageDead(_)
 653         | StatementKind::Nop
 654         | StatementKind::FakeRead(..)
 655         | StatementKind::Retag { .. }
 656         | StatementKind::AscribeUserType(..) => {}
 657
 658         StatementKind::InlineAsm { .. } => unimpl!("Inline assembly is not supported"),
 659     }
 660 }
 661
 662 fn codegen_array_len<'a, 'tcx: 'a>(
 663     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 664     place: CPlace<'tcx>,
 665 ) -> Value {
 666     match place.layout().ty.sty {
 667         ty::Array(_elem_ty, len) => {
 668             let len = crate::constant::force_eval_const(fx, len).unwrap_usize(fx.tcx) as i64;
 669             fx.bcx.ins().iconst(fx.pointer_type, len)
 670         }
 671         ty::Slice(_elem_ty) => {
 672             place.to_addr_maybe_unsized(fx).1.expect("Length metadata for slice place")
 673         }
 674         _ => bug!("Rvalue::Len({:?})", place),
 675     }
 676 }
 677
 678 pub fn trans_get_discriminant<'a, 'tcx: 'a>(
 679     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 680     value: CValue<'tcx>,
 681     dest_layout: TyLayout<'tcx>,
 682 ) -> CValue<'tcx> {
 683     let layout = value.layout();
 684
 685     if layout.abi == layout::Abi::Uninhabited {
 686         trap_unreachable(&mut fx.bcx);
 687     }
 688     match layout.variants {
 689         layout::Variants::Single { index } => {
 690             let discr_val = layout
 691                 .ty
 692                 .ty_adt_def()
 693                 .map_or(index.as_u32() as u128, |def| {
 694                     def.discriminant_for_variant(fx.tcx, index).val
 695                 });
 696             return CValue::const_val(fx, dest_layout.ty, discr_val as u64 as i64);
 697         }
 698         layout::Variants::Tagged { .. } | layout::Variants::NicheFilling { .. } => {}
 699     }
 700
 701     let discr = value.value_field(fx, mir::Field::new(0));
 702     let discr_ty = discr.layout().ty;
 703     let lldiscr = discr.load_scalar(fx);
 704     match layout.variants {
 705         layout::Variants::Single { .. } => bug!(),
 706         layout::Variants::Tagged { ref tag, .. } => {
 707             let signed = match tag.value {
 708                 layout::Int(_, signed) => signed,
 709                 _ => false,
 710             };
 711             let val = clif_intcast(fx, lldiscr, fx.clif_type(dest_layout.ty).unwrap(), signed);
 712             return CValue::ByVal(val, dest_layout);
 713         }
 714         layout::Variants::NicheFilling {
 715             dataful_variant,
 716             ref niche_variants,
 717             niche_start,
 718             ..
 719         } => {
 720             let niche_llty = fx.clif_type(discr_ty).unwrap();
 721             let dest_clif_ty = fx.clif_type(dest_layout.ty).unwrap();
 722             if niche_variants.start() == niche_variants.end() {
 723                 let b = fx
 724                     .bcx
 725                     .ins()
 726                     .icmp_imm(IntCC::Equal, lldiscr, niche_start as u64 as i64);
 727                 let if_true = fx
 728                     .bcx
 729                     .ins()
 730                     .iconst(dest_clif_ty, niche_variants.start().as_u32() as i64);
 731                 let if_false = fx
 732                     .bcx
 733                     .ins()
 734                     .iconst(dest_clif_ty, dataful_variant.as_u32() as i64);
 735                 let val = fx.bcx.ins().select(b, if_true, if_false);
 736                 return CValue::ByVal(val, dest_layout);
 737             } else {
 738                 // Rebase from niche values to discriminant values.
 739                 let delta = niche_start.wrapping_sub(niche_variants.start().as_u32() as u128);
 740                 let delta = fx.bcx.ins().iconst(niche_llty, delta as u64 as i64);
 741                 let lldiscr = fx.bcx.ins().isub(lldiscr, delta);
 742                 let b = fx.bcx.ins().icmp_imm(
 743                     IntCC::UnsignedLessThanOrEqual,
 744                     lldiscr,
 745                     niche_variants.end().as_u32() as i64,
 746                 );
 747                 let if_true =
 748                     clif_intcast(fx, lldiscr, fx.clif_type(dest_layout.ty).unwrap(), false);
 749                 let if_false = fx
 750                     .bcx
 751                     .ins()
 752                     .iconst(dest_clif_ty, dataful_variant.as_u32() as i64);
 753                 let val = fx.bcx.ins().select(b, if_true, if_false);
 754                 return CValue::ByVal(val, dest_layout);
 755             }
 756         }
 757     }
 758 }
 759
 760 macro_rules! binop_match {
 761     (@single $fx:expr, $bug_fmt:expr, $var:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, bug) => {
 762         bug!("binop {} on {} lhs: {:?} rhs: {:?}", stringify!($var), $bug_fmt, $lhs, $rhs)
 763     };
 764     (@single $fx:expr, $bug_fmt:expr, $var:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, icmp($cc:ident)) => {{
 765         assert_eq!($fx.tcx.types.bool, $ret_ty);
 766         let ret_layout = $fx.layout_of($ret_ty);
 767
 768         let b = $fx.bcx.ins().icmp(IntCC::$cc, $lhs, $rhs);
 769         CValue::ByVal($fx.bcx.ins().bint(types::I8, b), ret_layout)
 770     }};
 771     (@single $fx:expr, $bug_fmt:expr, $var:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, fcmp($cc:ident)) => {{
 772         assert_eq!($fx.tcx.types.bool, $ret_ty);
 773         let ret_layout = $fx.layout_of($ret_ty);
 774         let b = $fx.bcx.ins().fcmp(FloatCC::$cc, $lhs, $rhs);
 775         CValue::ByVal($fx.bcx.ins().bint(types::I8, b), ret_layout)
 776     }};
 777     (@single $fx:expr, $bug_fmt:expr, $var:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, custom(|| $body:expr)) => {{
 778         $body
 779     }};
 780     (@single $fx:expr, $bug_fmt:expr, $var:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, $name:ident) => {{
 781         let ret_layout = $fx.layout_of($ret_ty);
 782         CValue::ByVal($fx.bcx.ins().$name($lhs, $rhs), ret_layout)
 783     }};
 784     (
 785         $fx:expr, $bin_op:expr, $signed:expr, $lhs:expr, $rhs:expr, $ret_ty:expr, $bug_fmt:expr;
 786         $(
 787             $var:ident ($sign:pat) $name:tt $( ( $($next:tt)* ) )? ;
 788         )*
 789     ) => {{
 790         let lhs = $lhs.load_scalar($fx);
 791         let rhs = $rhs.load_scalar($fx);
 792         match ($bin_op, $signed) {
 793             $(
 794                 (BinOp::$var, $sign) => binop_match!(@single $fx, $bug_fmt, $var, $signed, lhs, rhs, $ret_ty, $name $( ( $($next)* ) )?),
 795             )*
 796         }
 797     }}
 798 }
 799
 800 fn trans_bool_binop<'a, 'tcx: 'a>(
 801     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 802     bin_op: BinOp,
 803     lhs: CValue<'tcx>,
 804     rhs: CValue<'tcx>,
 805     ty: Ty<'tcx>,
 806 ) -> CValue<'tcx> {
 807     let res = binop_match! {
 808         fx, bin_op, false, lhs, rhs, ty, "bool";
 809         Add (_) bug;
 810         Sub (_) bug;
 811         Mul (_) bug;
 812         Div (_) bug;
 813         Rem (_) bug;
 814         BitXor (_) bxor;
 815         BitAnd (_) band;
 816         BitOr (_) bor;
 817         Shl (_) bug;
 818         Shr (_) bug;
 819
 820         Eq (_) icmp(Equal);
 821         Lt (_) icmp(UnsignedLessThan);
 822         Le (_) icmp(UnsignedLessThanOrEqual);
 823         Ne (_) icmp(NotEqual);
 824         Ge (_) icmp(UnsignedGreaterThanOrEqual);
 825         Gt (_) icmp(UnsignedGreaterThan);
 826
 827         Offset (_) bug;
 828     };
 829
 830     res
 831 }
 832
 833 pub fn trans_int_binop<'a, 'tcx: 'a>(
 834     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 835     bin_op: BinOp,
 836     lhs: CValue<'tcx>,
 837     rhs: CValue<'tcx>,
 838     out_ty: Ty<'tcx>,
 839     signed: bool,
 840 ) -> CValue<'tcx> {
 841     if bin_op != BinOp::Shl && bin_op != BinOp::Shr {
 842         assert_eq!(
 843             lhs.layout().ty,
 844             rhs.layout().ty,
 845             "int binop requires lhs and rhs of same type"
 846         );
 847     }
 848     binop_match! {
 849         fx, bin_op, signed, lhs, rhs, out_ty, "int/uint";
 850         Add (_) iadd;
 851         Sub (_) isub;
 852         Mul (_) imul;
 853         Div (false) udiv;
 854         Div (true) sdiv;
 855         Rem (false) urem;
 856         Rem (true) srem;
 857         BitXor (_) bxor;
 858         BitAnd (_) band;
 859         BitOr (_) bor;
 860         Shl (_) ishl;
 861         Shr (false) ushr;
 862         Shr (true) sshr;
 863
 864         Eq (_) icmp(Equal);
 865         Lt (false) icmp(UnsignedLessThan);
 866         Lt (true) icmp(SignedLessThan);
 867         Le (false) icmp(UnsignedLessThanOrEqual);
 868         Le (true) icmp(SignedLessThanOrEqual);
 869         Ne (_) icmp(NotEqual);
 870         Ge (false) icmp(UnsignedGreaterThanOrEqual);
 871         Ge (true) icmp(SignedGreaterThanOrEqual);
 872         Gt (false) icmp(UnsignedGreaterThan);
 873         Gt (true) icmp(SignedGreaterThan);
 874
 875         Offset (_) bug;
 876     }
 877 }
 878
 879 pub fn trans_checked_int_binop<'a, 'tcx: 'a>(
 880     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 881     bin_op: BinOp,
 882     in_lhs: CValue<'tcx>,
 883     in_rhs: CValue<'tcx>,
 884     out_ty: Ty<'tcx>,
 885     signed: bool,
 886 ) -> CValue<'tcx> {
 887     if bin_op != BinOp::Shl && bin_op != BinOp::Shr {
 888         assert_eq!(
 889             in_lhs.layout().ty,
 890             in_rhs.layout().ty,
 891             "checked int binop requires lhs and rhs of same type"
 892         );
 893     }
 894
 895     let lhs = in_lhs.load_scalar(fx);
 896     let rhs = in_rhs.load_scalar(fx);
 897     let res = match bin_op {
 898         BinOp::Add => fx.bcx.ins().iadd(lhs, rhs),
 899         BinOp::Sub => fx.bcx.ins().isub(lhs, rhs),
 900         BinOp::Mul => fx.bcx.ins().imul(lhs, rhs),
 901         BinOp::Shl => fx.bcx.ins().ishl(lhs, rhs),
 902         BinOp::Shr => {
 903             if !signed {
 904                 fx.bcx.ins().ushr(lhs, rhs)
 905             } else {
 906                 fx.bcx.ins().sshr(lhs, rhs)
 907             }
 908         }
 909         _ => bug!(
 910             "binop {:?} on checked int/uint lhs: {:?} rhs: {:?}",
 911             bin_op,
 912             in_lhs,
 913             in_rhs
 914         ),
 915     };
 916
 917     // TODO: check for overflow
 918     let has_overflow = fx.bcx.ins().iconst(types::I8, 0);
 919
 920     let out_place = CPlace::new_stack_slot(fx, out_ty);
 921     let out_layout = out_place.layout();
 922     out_place.write_cvalue(fx, CValue::ByValPair(res, has_overflow, out_layout));
 923
 924     out_place.to_cvalue(fx)
 925 }
 926
 927 fn trans_float_binop<'a, 'tcx: 'a>(
 928     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 929     bin_op: BinOp,
 930     lhs: CValue<'tcx>,
 931     rhs: CValue<'tcx>,
 932     ty: Ty<'tcx>,
 933 ) -> CValue<'tcx> {
 934     let res = binop_match! {
 935         fx, bin_op, false, lhs, rhs, ty, "float";
 936         Add (_) fadd;
 937         Sub (_) fsub;
 938         Mul (_) fmul;
 939         Div (_) fdiv;
 940         Rem (_) custom(|| {
 941             assert_eq!(lhs.layout().ty, ty);
 942             assert_eq!(rhs.layout().ty, ty);
 943             match ty.sty {
 944                 ty::Float(FloatTy::F32) => fx.easy_call("fmodf", &[lhs, rhs], ty),
 945                 ty::Float(FloatTy::F64) => fx.easy_call("fmod", &[lhs, rhs], ty),
 946                 _ => bug!(),
 947             }
 948         });
 949         BitXor (_) bxor;
 950         BitAnd (_) band;
 951         BitOr (_) bor;
 952         Shl (_) bug;
 953         Shr (_) bug;
 954
 955         Eq (_) fcmp(Equal);
 956         Lt (_) fcmp(LessThan);
 957         Le (_) fcmp(LessThanOrEqual);
 958         Ne (_) fcmp(NotEqual);
 959         Ge (_) fcmp(GreaterThanOrEqual);
 960         Gt (_) fcmp(GreaterThan);
 961
 962         Offset (_) bug;
 963     };
 964
 965     res
 966 }
 967
 968 fn trans_char_binop<'a, 'tcx: 'a>(
 969     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 970     bin_op: BinOp,
 971     lhs: CValue<'tcx>,
 972     rhs: CValue<'tcx>,
 973     ty: Ty<'tcx>,
 974 ) -> CValue<'tcx> {
 975     let res = binop_match! {
 976         fx, bin_op, false, lhs, rhs, ty, "char";
 977         Add (_) bug;
 978         Sub (_) bug;
 979         Mul (_) bug;
 980         Div (_) bug;
 981         Rem (_) bug;
 982         BitXor (_) bug;
 983         BitAnd (_) bug;
 984         BitOr (_) bug;
 985         Shl (_) bug;
 986         Shr (_) bug;
 987
 988         Eq (_) icmp(Equal);
 989         Lt (_) icmp(UnsignedLessThan);
 990         Le (_) icmp(UnsignedLessThanOrEqual);
 991         Ne (_) icmp(NotEqual);
 992         Ge (_) icmp(UnsignedGreaterThanOrEqual);
 993         Gt (_) icmp(UnsignedGreaterThan);
 994
 995         Offset (_) bug;
 996     };
 997
 998     res
 999 }
1000
1001 fn trans_ptr_binop<'a, 'tcx: 'a>(
1002     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
1003     bin_op: BinOp,
1004     lhs: CValue<'tcx>,
1005     rhs: CValue<'tcx>,
1006     ret_ty: Ty<'tcx>,
1007 ) -> CValue<'tcx> {
1008     let not_fat = match lhs.layout().ty.sty {
1009         ty::RawPtr(TypeAndMut { ty, mutbl: _ }) => ty.is_sized(fx.tcx.at(DUMMY_SP), ParamEnv::reveal_all()),
1010         ty::FnPtr(..) => true,
1011         _ => bug!("trans_ptr_binop on non ptr"),
1012     };
1013     if not_fat {
1014         if let BinOp::Offset = bin_op {
1015             let (base, offset) = (lhs, rhs.load_scalar(fx));
1016             let pointee_ty = base.layout().ty.builtin_deref(true).unwrap().ty;
1017             let pointee_size = fx.layout_of(pointee_ty).size.bytes();
1018             let ptr_diff = fx.bcx.ins().imul_imm(offset, pointee_size as i64);
1019             let base_val = base.load_scalar(fx);
1020             let res = fx.bcx.ins().iadd(base_val, ptr_diff);
1021             return CValue::ByVal(res, base.layout());
1022         }
1023
1024         binop_match! {
1025             fx, bin_op, false, lhs, rhs, ret_ty, "ptr";
1026             Add (_) bug;
1027             Sub (_) bug;
1028             Mul (_) bug;
1029             Div (_) bug;
1030             Rem (_) bug;
1031             BitXor (_) bug;
1032             BitAnd (_) bug;
1033             BitOr (_) bug;
1034             Shl (_) bug;
1035             Shr (_) bug;
1036
1037             Eq (_) icmp(Equal);
1038             Lt (_) icmp(UnsignedLessThan);
1039             Le (_) icmp(UnsignedLessThanOrEqual);
1040             Ne (_) icmp(NotEqual);
1041             Ge (_) icmp(UnsignedGreaterThanOrEqual);
1042             Gt (_) icmp(UnsignedGreaterThan);
1043
1044             Offset (_) bug; // Handled above
1045         }
1046     } else {
1047         let (lhs_ptr, lhs_extra) = lhs.load_value_pair(fx);
1048         let (rhs_ptr, rhs_extra) = rhs.load_value_pair(fx);
1049         let res = match bin_op {
1050             BinOp::Eq => {
1051                 let ptr_eq = fx.bcx.ins().icmp(IntCC::Equal, lhs_ptr, rhs_ptr);
1052                 let extra_eq = fx.bcx.ins().icmp(IntCC::Equal, lhs_extra, rhs_extra);
1053                 fx.bcx.ins().band(ptr_eq, extra_eq)
1054             }
1055             BinOp::Ne => {
1056                 let ptr_ne = fx.bcx.ins().icmp(IntCC::NotEqual, lhs_ptr, rhs_ptr);
1057                 let extra_ne = fx.bcx.ins().icmp(IntCC::NotEqual, lhs_extra, rhs_extra);
1058                 fx.bcx.ins().bor(ptr_ne, extra_ne)
1059             }
1060             _ => unimplemented!(
1061                 "trans_ptr_binop({:?}, <fat ptr>, <fat ptr>) not implemented",
1062                 bin_op
1063             ),
1064         };
1065
1066         assert_eq!(fx.tcx.types.bool, ret_ty);
1067         let ret_layout = fx.layout_of(ret_ty);
1068         CValue::ByVal(fx.bcx.ins().bint(types::I8, res), ret_layout)
1069     }
1070 }
1071
1072 pub fn trans_place<'a, 'tcx: 'a>(
1073     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
1074     place: &Place<'tcx>,
1075 ) -> CPlace<'tcx> {
1076     match place {
1077         Place::Local(local) => fx.get_local_place(*local),
1078         Place::Promoted(promoted) => crate::constant::trans_promoted(fx, promoted.0),
1079         Place::Static(static_) => crate::constant::codegen_static_ref(fx, static_),
1080         Place::Projection(projection) => {
1081             let base = trans_place(fx, &projection.base);
1082             match projection.elem {
1083                 ProjectionElem::Deref => base.place_deref(fx),
1084                 ProjectionElem::Field(field, _ty) => base.place_field(fx, field),
1085                 ProjectionElem::Index(local) => {
1086                     let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
1087                     base.place_index(fx, index)
1088                 }
1089                 ProjectionElem::ConstantIndex {
1090                     offset,
1091                     min_length: _,
1092                     from_end,
1093                 } => {
1094                     let index = if !from_end {
1095                         fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
1096                     } else {
1097                         let len = codegen_array_len(fx, base);
1098                         fx.bcx.ins().iadd_imm(len, -(offset as i64))
1099                     };
1100                     base.place_index(fx, index)
1101                 }
1102                 ProjectionElem::Subslice { from, to } => unimpl!(
1103                     "projection subslice {:?} from {} to {}",
1104                     projection.base,
1105                     from,
1106                     to
1107                 ),
1108                 ProjectionElem::Downcast(_adt_def, variant) => base.downcast_variant(fx, variant),
1109             }
1110         }
1111     }
1112 }
1113
1114 pub fn trans_operand<'a, 'tcx>(
1115     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
1116     operand: &Operand<'tcx>,
1117 ) -> CValue<'tcx> {
1118     match operand {
1119         Operand::Move(place) | Operand::Copy(place) => {
1120             let cplace = trans_place(fx, place);
1121             cplace.to_cvalue(fx)
1122         }
1123         Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),
1124     }
1125 }