src/base.rs

   1 use rustc::ty::adjustment::PointerCast;
   2
   3 use crate::prelude::*;
   4
   5 pub fn trans_fn<'a, 'clif, 'tcx: 'a, B: Backend + 'static>(
   6     cx: &mut crate::CodegenCx<'clif, 'tcx, B>,
   7     instance: Instance<'tcx>,
   8     linkage: Linkage,
   9 ) {
  10     let tcx = cx.tcx;
  11
  12     let mir = tcx.instance_mir(instance.def);
  13
  14     // Declare function
  15     let (name, sig) = get_function_name_and_sig(tcx, instance, false);
  16     let func_id = cx.module.declare_function(&name, linkage, &sig).unwrap();
  17     let mut debug_context = cx
  18         .debug_context
  19         .as_mut()
  20         .map(|debug_context| FunctionDebugContext::new(tcx, debug_context, mir, &name, &sig));
  21
  22     // Make FunctionBuilder
  23     let mut func = Function::with_name_signature(ExternalName::user(0, 0), sig);
  24     let mut func_ctx = FunctionBuilderContext::new();
  25     let mut bcx = FunctionBuilder::new(&mut func, &mut func_ctx);
  26
  27     // Predefine ebb's
  28     let start_ebb = bcx.create_ebb();
  29     let mut ebb_map: HashMap<BasicBlock, Ebb> = HashMap::new();
  30     for (bb, _bb_data) in mir.basic_blocks().iter_enumerated() {
  31         ebb_map.insert(bb, bcx.create_ebb());
  32     }
  33
  34     // Make FunctionCx
  35     let pointer_type = cx.module.target_config().pointer_type();
  36     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  37
  38     let mut fx = FunctionCx {
  39         tcx,
  40         module: cx.module,
  41         pointer_type,
  42
  43         instance,
  44         mir,
  45
  46         bcx,
  47         ebb_map,
  48         local_map: HashMap::new(),
  49
  50         clif_comments,
  51         constants: &mut cx.ccx,
  52         caches: &mut cx.caches,
  53         source_info_set: indexmap::IndexSet::new(),
  54     };
  55
  56     with_unimpl_span(fx.mir.span, || {
  57         crate::abi::codegen_fn_prelude(&mut fx, start_ebb);
  58         codegen_fn_content(&mut fx);
  59     });
  60
  61     // Recover all necessary data from fx, before accessing func will prevent future access to it.
  62     let instance = fx.instance;
  63     let clif_comments = fx.clif_comments;
  64     let source_info_set = fx.source_info_set;
  65
  66     #[cfg(debug_assertions)]
  67     crate::pretty_clif::write_clif_file(cx.tcx, "unopt", instance, &func, &clif_comments, None);
  68
  69     // Verify function
  70     verify_func(tcx, &clif_comments, &func);
  71
  72     // Define function
  73     let context = &mut cx.caches.context;
  74     context.func = func;
  75     cx.module
  76         .define_function(func_id, context)
  77         .unwrap();
  78
  79     let value_ranges = context.build_value_labels_ranges(cx.module.isa()).expect("value location ranges");
  80
  81     // Write optimized function to file for debugging
  82     #[cfg(debug_assertions)]
  83     crate::pretty_clif::write_clif_file(cx.tcx, "opt", instance, &context.func, &clif_comments, Some(&value_ranges));
  84
  85     // Define debuginfo for function
  86     let isa = cx.module.isa();
  87     debug_context
  88         .as_mut()
  89         .map(|x| x.define(tcx, context, isa, &source_info_set));
  90
  91     // Clear context to make it usable for the next function
  92     context.clear();
  93 }
  94
  95 fn verify_func(tcx: TyCtxt, writer: &crate::pretty_clif::CommentWriter, func: &Function) {
  96     let flags = settings::Flags::new(settings::builder());
  97     match ::cranelift::codegen::verify_function(&func, &flags) {
  98         Ok(_) => {}
  99         Err(err) => {
 100             tcx.sess.err(&format!("{:?}", err));
 101             let pretty_error = ::cranelift::codegen::print_errors::pretty_verifier_error(
 102                 &func,
 103                 None,
 104                 Some(Box::new(writer)),
 105                 err,
 106             );
 107             tcx.sess
 108                 .fatal(&format!("cranelift verify error:\n{}", pretty_error));
 109         }
 110     }
 111 }
 112
 113 fn codegen_fn_content<'a, 'tcx: 'a>(fx: &mut FunctionCx<'a, 'tcx, impl Backend>) {
 114     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 115         if bb_data.is_cleanup {
 116             // Unwinding after panicking is not supported
 117             continue;
 118         }
 119
 120         let ebb = fx.get_ebb(bb);
 121         fx.bcx.switch_to_block(ebb);
 122
 123         fx.bcx.ins().nop();
 124         for stmt in &bb_data.statements {
 125             fx.set_debug_loc(stmt.source_info);
 126             trans_stmt(fx, ebb, stmt);
 127         }
 128
 129         #[cfg(debug_assertions)]
 130         {
 131             let mut terminator_head = "\n".to_string();
 132             bb_data
 133                 .terminator()
 134                 .kind
 135                 .fmt_head(&mut terminator_head)
 136                 .unwrap();
 137             let inst = fx.bcx.func.layout.last_inst(ebb).unwrap();
 138             fx.add_comment(inst, terminator_head);
 139         }
 140
 141         fx.set_debug_loc(bb_data.terminator().source_info);
 142
 143         match &bb_data.terminator().kind {
 144             TerminatorKind::Goto { target } => {
 145                 let ebb = fx.get_ebb(*target);
 146                 fx.bcx.ins().jump(ebb, &[]);
 147             }
 148             TerminatorKind::Return => {
 149                 crate::abi::codegen_return(fx);
 150             }
 151             TerminatorKind::Assert {
 152                 cond,
 153                 expected,
 154                 msg,
 155                 target,
 156                 cleanup: _,
 157             } => {
 158                 let cond = trans_operand(fx, cond).load_scalar(fx);
 159                 // TODO HACK brz/brnz for i8/i16 is not yet implemented
 160                 let cond = fx.bcx.ins().uextend(types::I32, cond);
 161                 let target = fx.get_ebb(*target);
 162                 if *expected {
 163                     fx.bcx.ins().brnz(cond, target, &[]);
 164                 } else {
 165                     fx.bcx.ins().brz(cond, target, &[]);
 166                 };
 167                 trap_panic(fx, format!("[panic] Assert {:?} at {:?} failed.", msg, bb_data.terminator().source_info.span));
 168             }
 169
 170             TerminatorKind::SwitchInt {
 171                 discr,
 172                 switch_ty: _,
 173                 values,
 174                 targets,
 175             } => {
 176                 let discr = trans_operand(fx, discr).load_scalar(fx);
 177                 let mut switch = ::cranelift::frontend::Switch::new();
 178                 for (i, value) in values.iter().enumerate() {
 179                     let ebb = fx.get_ebb(targets[i]);
 180                     switch.set_entry(*value as u64, ebb);
 181                 }
 182                 let otherwise_ebb = fx.get_ebb(targets[targets.len() - 1]);
 183                 switch.emit(&mut fx.bcx, discr, otherwise_ebb);
 184             }
 185             TerminatorKind::Call {
 186                 func,
 187                 args,
 188                 destination,
 189                 cleanup: _,
 190                 from_hir_call: _,
 191             } => {
 192                 crate::abi::codegen_terminator_call(fx, func, args, destination);
 193             }
 194             TerminatorKind::Resume | TerminatorKind::Abort => {
 195                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 196             }
 197             TerminatorKind::Unreachable => {
 198                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 199             }
 200             TerminatorKind::Yield { .. }
 201             | TerminatorKind::FalseEdges { .. }
 202             | TerminatorKind::FalseUnwind { .. }
 203             | TerminatorKind::DropAndReplace { .. }
 204             | TerminatorKind::GeneratorDrop => {
 205                 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
 206             }
 207             TerminatorKind::Drop {
 208                 location,
 209                 target,
 210                 unwind: _,
 211             } => {
 212                 let drop_place = trans_place(fx, location);
 213                 crate::abi::codegen_drop(fx, drop_place);
 214
 215                 let target_ebb = fx.get_ebb(*target);
 216                 fx.bcx.ins().jump(target_ebb, &[]);
 217             }
 218         };
 219     }
 220
 221     fx.bcx.seal_all_blocks();
 222     fx.bcx.finalize();
 223 }
 224
 225 fn trans_stmt<'a, 'tcx: 'a>(
 226     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 227     cur_ebb: Ebb,
 228     stmt: &Statement<'tcx>,
 229 ) {
 230     let _print_guard = PrintOnPanic(|| format!("stmt {:?}", stmt));
 231
 232     fx.set_debug_loc(stmt.source_info);
 233
 234     #[cfg(debug_assertions)]
 235     match &stmt.kind {
 236         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 237         _ => {
 238             let inst = fx.bcx.func.layout.last_inst(cur_ebb).unwrap();
 239             fx.add_comment(inst, format!("{:?}", stmt));
 240         }
 241     }
 242
 243     match &stmt.kind {
 244         StatementKind::SetDiscriminant {
 245             place,
 246             variant_index,
 247         } => {
 248             let place = trans_place(fx, place);
 249             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 250         }
 251         StatementKind::Assign(to_place, rval) => {
 252             let lval = trans_place(fx, to_place);
 253             let dest_layout = lval.layout();
 254             match &**rval {
 255                 Rvalue::Use(operand) => {
 256                     let val = trans_operand(fx, operand);
 257                     lval.write_cvalue(fx, val);
 258                 }
 259                 Rvalue::Ref(_, _, place) => {
 260                     let place = trans_place(fx, place);
 261                     place.write_place_ref(fx, lval);
 262                 }
 263                 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
 264                     let lhs = trans_operand(fx, lhs);
 265                     let rhs = trans_operand(fx, rhs);
 266
 267                     let res = crate::num::codegen_binop(fx, *bin_op, lhs, rhs);
 268                     lval.write_cvalue(fx, res);
 269                 }
 270                 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
 271                     let lhs = trans_operand(fx, lhs);
 272                     let rhs = trans_operand(fx, rhs);
 273
 274                     let res = if !fx.tcx.sess.overflow_checks() {
 275                         let val = crate::num::trans_int_binop(fx, *bin_op, lhs, rhs).load_scalar(fx);
 276                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 277                         CValue::by_val_pair(val, is_overflow, lval.layout())
 278                     } else {
 279                         crate::num::trans_checked_int_binop(fx, *bin_op, lhs, rhs)
 280                     };
 281
 282                     lval.write_cvalue(fx, res);
 283                 }
 284                 Rvalue::UnaryOp(un_op, operand) => {
 285                     let operand = trans_operand(fx, operand);
 286                     let layout = operand.layout();
 287                     let val = operand.load_scalar(fx);
 288                     let res = match un_op {
 289                         UnOp::Not => {
 290                             match layout.ty.sty {
 291                                 ty::Bool => {
 292                                     let val = fx.bcx.ins().uextend(types::I32, val); // WORKAROUND for CraneStation/cranelift#466
 293                                     let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 294                                     fx.bcx.ins().bint(types::I8, res)
 295                                 }
 296                                 ty::Uint(_) | ty::Int(_) => {
 297                                     fx.bcx.ins().bnot(val)
 298                                 }
 299                                 _ => unimplemented!("un op Not for {:?}", layout.ty),
 300                             }
 301                         }
 302                         UnOp::Neg => match layout.ty.sty {
 303                             ty::Int(_) => {
 304                                 let clif_ty = fx.clif_type(layout.ty).unwrap();
 305                                 if clif_ty == types::I128 {
 306                                     // FIXME implement it
 307                                     crate::trap::trap_unreachable_ret_value(fx, layout, "i128 neg is not yet supported").load_scalar(fx)
 308                                 } else {
 309                                     let zero = fx.bcx.ins().iconst(clif_ty, 0);
 310                                     fx.bcx.ins().isub(zero, val)
 311                                 }
 312                             }
 313                             ty::Float(_) => fx.bcx.ins().fneg(val),
 314                             _ => unimplemented!("un op Neg for {:?}", layout.ty),
 315                         },
 316                     };
 317                     lval.write_cvalue(fx, CValue::by_val(res, layout));
 318                 }
 319                 Rvalue::Cast(CastKind::Pointer(PointerCast::ReifyFnPointer), operand, ty) => {
 320                     let layout = fx.layout_of(ty);
 321                     match fx
 322                         .monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx))
 323                         .sty
 324                     {
 325                         ty::FnDef(def_id, substs) => {
 326                             let func_ref = fx.get_function_ref(
 327                                 Instance::resolve(fx.tcx, ParamEnv::reveal_all(), def_id, substs)
 328                                     .unwrap(),
 329                             );
 330                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 331                             lval.write_cvalue(fx, CValue::by_val(func_addr, layout));
 332                         }
 333                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", ty),
 334                     }
 335                 }
 336                 Rvalue::Cast(CastKind::Pointer(PointerCast::UnsafeFnPointer), operand, ty)
 337                 | Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer), operand, ty) => {
 338                     let operand = trans_operand(fx, operand);
 339                     let layout = fx.layout_of(ty);
 340                     lval.write_cvalue(fx, operand.unchecked_cast_to(layout));
 341                 }
 342                 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
 343                     let operand = trans_operand(fx, operand);
 344                     let from_ty = operand.layout().ty;
 345
 346                     fn is_fat_ptr<'a, 'tcx: 'a>(fx: &FunctionCx<'a, 'tcx, impl Backend>, ty: Ty<'tcx>) -> bool {
 347                         ty
 348                             .builtin_deref(true)
 349                             .map(|ty::TypeAndMut {ty: pointee_ty, mutbl: _ }| fx.layout_of(pointee_ty).is_unsized())
 350                             .unwrap_or(false)
 351                     }
 352
 353                     if is_fat_ptr(fx, from_ty) {
 354                         if is_fat_ptr(fx, to_ty) {
 355                             // fat-ptr -> fat-ptr
 356                             lval.write_cvalue(fx, operand.unchecked_cast_to(dest_layout));
 357                         } else {
 358                             // fat-ptr -> thin-ptr
 359                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 360                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 361                         }
 362                     } else if let ty::Adt(adt_def, _substs) = from_ty.sty {
 363                         // enum -> discriminant value
 364                         assert!(adt_def.is_enum());
 365                         match to_ty.sty {
 366                             ty::Uint(_) | ty::Int(_) => {},
 367                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 368                         }
 369
 370                         // FIXME avoid forcing to stack
 371                         let place =
 372                             CPlace::for_addr(operand.force_stack(fx), operand.layout());
 373                         let discr = crate::discriminant::codegen_get_discriminant(fx, place, fx.layout_of(to_ty));
 374                         lval.write_cvalue(fx, discr);
 375                     } else {
 376                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 377                         let from = operand.load_scalar(fx);
 378
 379                         let res = clif_int_or_float_cast(fx, from, type_sign(from_ty), to_clif_ty, type_sign(to_ty));
 380                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 381                     }
 382                 }
 383                 Rvalue::Cast(CastKind::Pointer(PointerCast::ClosureFnPointer(_)), operand, _ty) => {
 384                     let operand = trans_operand(fx, operand);
 385                     match operand.layout().ty.sty {
 386                         ty::Closure(def_id, substs) => {
 387                             let instance = Instance::resolve_closure(
 388                                 fx.tcx,
 389                                 def_id,
 390                                 substs,
 391                                 ty::ClosureKind::FnOnce,
 392                             );
 393                             let func_ref = fx.get_function_ref(instance);
 394                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 395                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 396                         }
 397                         _ => {
 398                             bug!("{} cannot be cast to a fn ptr", operand.layout().ty)
 399                         }
 400                     }
 401                 }
 402                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), operand, _ty) => {
 403                     let operand = trans_operand(fx, operand);
 404                     operand.unsize_value(fx, lval);
 405                 }
 406                 Rvalue::Discriminant(place) => {
 407                     let place = trans_place(fx, place);
 408                     let discr = crate::discriminant::codegen_get_discriminant(fx, place, dest_layout);
 409                     lval.write_cvalue(fx, discr);
 410                 }
 411                 Rvalue::Repeat(operand, times) => {
 412                     let operand = trans_operand(fx, operand);
 413                     for i in 0..*times {
 414                         let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 415                         let to = lval.place_index(fx, index);
 416                         to.write_cvalue(fx, operand);
 417                     }
 418                 }
 419                 Rvalue::Len(place) => {
 420                     let place = trans_place(fx, place);
 421                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 422                     let len = codegen_array_len(fx, place);
 423                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 424                 }
 425                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 426                     use rustc::middle::lang_items::ExchangeMallocFnLangItem;
 427
 428                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 429                     let layout = fx.layout_of(content_ty);
 430                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 431                     let llalign = fx
 432                         .bcx
 433                         .ins()
 434                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 435                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 436
 437                     // Allocate space:
 438                     let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
 439                         Ok(id) => id,
 440                         Err(s) => {
 441                             fx.tcx
 442                                 .sess
 443                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 444                         }
 445                     };
 446                     let instance = ty::Instance::mono(fx.tcx, def_id);
 447                     let func_ref = fx.get_function_ref(instance);
 448                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 449                     let ptr = fx.bcx.inst_results(call)[0];
 450                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 451                 }
 452                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 453                     assert!(lval
 454                         .layout()
 455                         .ty
 456                         .is_sized(fx.tcx.at(DUMMY_SP), ParamEnv::reveal_all()));
 457                     let ty_size = fx.layout_of(ty).size.bytes();
 458                     let val = CValue::const_val(fx, fx.tcx.types.usize, ty_size.into());
 459                     lval.write_cvalue(fx, val);
 460                 }
 461                 Rvalue::Aggregate(kind, operands) => match **kind {
 462                     AggregateKind::Array(_ty) => {
 463                         for (i, operand) in operands.into_iter().enumerate() {
 464                             let operand = trans_operand(fx, operand);
 465                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 466                             let to = lval.place_index(fx, index);
 467                             to.write_cvalue(fx, operand);
 468                         }
 469                     }
 470                     _ => unimpl!("shouldn't exist at trans {:?}", rval),
 471                 },
 472             }
 473         }
 474         StatementKind::StorageLive(_)
 475         | StatementKind::StorageDead(_)
 476         | StatementKind::Nop
 477         | StatementKind::FakeRead(..)
 478         | StatementKind::Retag { .. }
 479         | StatementKind::AscribeUserType(..) => {}
 480
 481         StatementKind::InlineAsm(asm) => {
 482             use syntax::ast::Name;
 483             let InlineAsm { asm, outputs: _, inputs: _ } = &**asm;
 484             let rustc::hir::InlineAsm {
 485                 asm: asm_code, // Name
 486                 outputs, // Vec<Name>
 487                 inputs, // Vec<Name>
 488                 clobbers, // Vec<Name>
 489                 volatile, // bool
 490                 alignstack, // bool
 491                 dialect: _, // syntax::ast::AsmDialect
 492                 asm_str_style: _,
 493             } = asm;
 494             match &*asm_code.as_str() {
 495                 "cpuid" | "cpuid\n" => {
 496                     assert_eq!(inputs, &[Name::intern("{eax}"), Name::intern("{ecx}")]);
 497
 498                     assert_eq!(outputs.len(), 4);
 499                     for (i, c) in (&["={eax}", "={ebx}", "={ecx}", "={edx}"]).iter().enumerate() {
 500                         assert_eq!(&outputs[i].constraint.as_str(), c);
 501                         assert!(!outputs[i].is_rw);
 502                         assert!(!outputs[i].is_indirect);
 503                     }
 504
 505                     assert_eq!(clobbers, &[Name::intern("rbx")]);
 506
 507                     assert!(!volatile);
 508                     assert!(!alignstack);
 509
 510                     crate::trap::trap_unimplemented(fx, "__cpuid_count arch intrinsic is not supported");
 511                 }
 512                 "xgetbv" => {
 513                     assert_eq!(inputs, &[Name::intern("{ecx}")]);
 514
 515                     assert_eq!(outputs.len(), 2);
 516                     for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
 517                         assert_eq!(&outputs[i].constraint.as_str(), c);
 518                         assert!(!outputs[i].is_rw);
 519                         assert!(!outputs[i].is_indirect);
 520                     }
 521
 522                     assert_eq!(clobbers, &[]);
 523
 524                     assert!(!volatile);
 525                     assert!(!alignstack);
 526
 527                     crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
 528                 }
 529                 _ if fx.tcx.symbol_name(fx.instance).as_str() == "__rust_probestack" => {
 530                     crate::trap::trap_unimplemented(fx, "__rust_probestack is not supported");
 531                 }
 532                 _ => unimpl!("Inline assembly is not supported"),
 533             }
 534         }
 535     }
 536 }
 537
 538 fn codegen_array_len<'a, 'tcx: 'a>(
 539     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 540     place: CPlace<'tcx>,
 541 ) -> Value {
 542     match place.layout().ty.sty {
 543         ty::Array(_elem_ty, len) => {
 544             let len = crate::constant::force_eval_const(fx, len)
 545                 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 546             fx.bcx.ins().iconst(fx.pointer_type, len)
 547         }
 548         ty::Slice(_elem_ty) => place
 549             .to_addr_maybe_unsized(fx)
 550             .1
 551             .expect("Length metadata for slice place"),
 552         _ => bug!("Rvalue::Len({:?})", place),
 553     }
 554 }
 555
 556 pub fn trans_place<'a, 'tcx: 'a>(
 557     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 558     place: &Place<'tcx>,
 559 ) -> CPlace<'tcx> {
 560     let base = match &place.base {
 561         PlaceBase::Local(local) => fx.get_local_place(*local),
 562         PlaceBase::Static(static_) => match static_.kind {
 563             StaticKind::Static(def_id) => {
 564                 crate::constant::codegen_static_ref(fx, def_id, static_.ty)
 565             }
 566             StaticKind::Promoted(promoted) => {
 567                 crate::constant::trans_promoted(fx, promoted, static_.ty)
 568             }
 569         }
 570     };
 571
 572     trans_place_projection(fx, base, &place.projection)
 573 }
 574
 575 pub fn trans_place_projection<'a, 'tcx: 'a>(
 576     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 577     base: CPlace<'tcx>,
 578     projection: &Option<Box<Projection<'tcx>>>,
 579 ) -> CPlace<'tcx> {
 580     let projection = if let Some(projection) = projection {
 581         projection
 582     } else {
 583         return base;
 584     };
 585
 586     let base = trans_place_projection(fx, base, &projection.base);
 587
 588     match projection.elem {
 589         ProjectionElem::Deref => base.place_deref(fx),
 590         ProjectionElem::Field(field, _ty) => base.place_field(fx, field),
 591         ProjectionElem::Index(local) => {
 592             let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 593             base.place_index(fx, index)
 594         }
 595         ProjectionElem::ConstantIndex {
 596             offset,
 597             min_length: _,
 598             from_end,
 599         } => {
 600             let index = if !from_end {
 601                 fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 602             } else {
 603                 let len = codegen_array_len(fx, base);
 604                 fx.bcx.ins().iadd_imm(len, -(offset as i64))
 605             };
 606             base.place_index(fx, index)
 607         }
 608         ProjectionElem::Subslice { from, to } => {
 609             // These indices are generated by slice patterns.
 610             // slice[from:-to] in Python terms.
 611
 612             match base.layout().ty.sty {
 613                 ty::Array(elem_ty, len) => {
 614                     let elem_layout = fx.layout_of(elem_ty);
 615                     let ptr = base.to_addr(fx);
 616                     let len = crate::constant::force_eval_const(fx, len)
 617                         .eval_usize(fx.tcx, ParamEnv::reveal_all());
 618                     CPlace::for_addr(
 619                         fx.bcx.ins().iadd_imm(ptr, elem_layout.size.bytes() as i64 * from as i64),
 620                         fx.layout_of(fx.tcx.mk_array(elem_ty, len - from as u64 - to as u64)),
 621                     )
 622                 }
 623                 ty::Slice(elem_ty) => {
 624                     let elem_layout = fx.layout_of(elem_ty);
 625                     let (ptr, len) = base.to_addr_maybe_unsized(fx);
 626                     let len = len.unwrap();
 627                     CPlace::for_addr_with_extra(
 628                         fx.bcx.ins().iadd_imm(ptr, elem_layout.size.bytes() as i64 * from as i64),
 629                         fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
 630                         base.layout(),
 631                     )
 632                 }
 633                 _ => unreachable!(),
 634             }
 635         }
 636         ProjectionElem::Downcast(_adt_def, variant) => base.downcast_variant(fx, variant),
 637     }
 638 }
 639
 640 pub fn trans_operand<'a, 'tcx>(
 641     fx: &mut FunctionCx<'a, 'tcx, impl Backend>,
 642     operand: &Operand<'tcx>,
 643 ) -> CValue<'tcx> {
 644     match operand {
 645         Operand::Move(place) | Operand::Copy(place) => {
 646             let cplace = trans_place(fx, place);
 647             cplace.to_cvalue(fx)
 648         }
 649         Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),
 650     }
 651 }