src/base.rs

   1 use rustc::ty::adjustment::PointerCast;
   2
   3 use crate::prelude::*;
   4
   5 pub fn trans_fn<'clif, 'tcx, 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(debug_context, instance, func_id, &name));
  21
  22     // Make FunctionBuilder
  23     let mut func = Function::with_name_signature(ExternalName::user(0, 0), sig);
  24     func.collect_debug_info();
  25     let mut func_ctx = FunctionBuilderContext::new();
  26     let mut bcx = FunctionBuilder::new(&mut func, &mut func_ctx);
  27
  28     // Predefine ebb's
  29     let start_ebb = bcx.create_ebb();
  30     let mut ebb_map: HashMap<BasicBlock, Ebb> = HashMap::new();
  31     for (bb, _bb_data) in mir.basic_blocks().iter_enumerated() {
  32         ebb_map.insert(bb, bcx.create_ebb());
  33     }
  34
  35     // Make FunctionCx
  36     let pointer_type = cx.module.target_config().pointer_type();
  37     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  38
  39     let mut fx = FunctionCx {
  40         tcx,
  41         module: cx.module,
  42         pointer_type,
  43
  44         instance,
  45         mir,
  46
  47         bcx,
  48         ebb_map,
  49         local_map: HashMap::new(),
  50
  51         clif_comments,
  52         constants_cx: &mut cx.constants_cx,
  53         caches: &mut cx.caches,
  54         source_info_set: indexmap::IndexSet::new(),
  55     };
  56
  57     crate::abi::codegen_fn_prelude(&mut fx, start_ebb);
  58     codegen_fn_content(&mut fx);
  59
  60     // Recover all necessary data from fx, before accessing func will prevent future access to it.
  61     let instance = fx.instance;
  62     let clif_comments = fx.clif_comments;
  63     let source_info_set = fx.source_info_set;
  64     let local_map = fx.local_map;
  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.define_function(func_id, context).unwrap();
  76
  77     // Write optimized function to file for debugging
  78     #[cfg(debug_assertions)]
  79     {
  80         let value_ranges = context
  81             .build_value_labels_ranges(cx.module.isa())
  82             .expect("value location ranges");
  83
  84         crate::pretty_clif::write_clif_file(
  85             cx.tcx,
  86             "opt",
  87             instance,
  88             &context.func,
  89             &clif_comments,
  90             Some(&value_ranges),
  91         );
  92     }
  93
  94     // Define debuginfo for function
  95     let isa = cx.module.isa();
  96     debug_context
  97         .as_mut()
  98         .map(|x| x.define(context, isa, &source_info_set, local_map));
  99
 100     // Clear context to make it usable for the next function
 101     context.clear();
 102 }
 103
 104 fn verify_func(tcx: TyCtxt, writer: &crate::pretty_clif::CommentWriter, func: &Function) {
 105     let flags = settings::Flags::new(settings::builder());
 106     match ::cranelift::codegen::verify_function(&func, &flags) {
 107         Ok(_) => {}
 108         Err(err) => {
 109             tcx.sess.err(&format!("{:?}", err));
 110             let pretty_error = ::cranelift::codegen::print_errors::pretty_verifier_error(
 111                 &func,
 112                 None,
 113                 Some(Box::new(writer)),
 114                 err,
 115             );
 116             tcx.sess
 117                 .fatal(&format!("cranelift verify error:\n{}", pretty_error));
 118         }
 119     }
 120 }
 121
 122 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Backend>) {
 123     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 124         if bb_data.is_cleanup {
 125             // Unwinding after panicking is not supported
 126             continue;
 127         }
 128
 129         let ebb = fx.get_ebb(bb);
 130         fx.bcx.switch_to_block(ebb);
 131
 132         fx.bcx.ins().nop();
 133         for stmt in &bb_data.statements {
 134             fx.set_debug_loc(stmt.source_info);
 135             trans_stmt(fx, ebb, stmt);
 136         }
 137
 138         #[cfg(debug_assertions)]
 139         {
 140             let mut terminator_head = "\n".to_string();
 141             bb_data
 142                 .terminator()
 143                 .kind
 144                 .fmt_head(&mut terminator_head)
 145                 .unwrap();
 146             let inst = fx.bcx.func.layout.last_inst(ebb).unwrap();
 147             fx.add_comment(inst, terminator_head);
 148         }
 149
 150         fx.set_debug_loc(bb_data.terminator().source_info);
 151
 152         match &bb_data.terminator().kind {
 153             TerminatorKind::Goto { target } => {
 154                 let ebb = fx.get_ebb(*target);
 155                 fx.bcx.ins().jump(ebb, &[]);
 156             }
 157             TerminatorKind::Return => {
 158                 crate::abi::codegen_return(fx);
 159             }
 160             TerminatorKind::Assert {
 161                 cond,
 162                 expected,
 163                 msg,
 164                 target,
 165                 cleanup: _,
 166             } => {
 167                 if !fx.tcx.sess.overflow_checks() {
 168                     if let mir::interpret::PanicInfo::OverflowNeg = *msg {
 169                         let target = fx.get_ebb(*target);
 170                         fx.bcx.ins().jump(target, &[]);
 171                         continue;
 172                     }
 173                 }
 174                 let cond = trans_operand(fx, cond).load_scalar(fx);
 175                 let target = fx.get_ebb(*target);
 176                 if *expected {
 177                     fx.bcx.ins().brnz(cond, target, &[]);
 178                 } else {
 179                     fx.bcx.ins().brz(cond, target, &[]);
 180                 };
 181                 trap_panic(
 182                     fx,
 183                     format!(
 184                         "[panic] Assert {:?} at {:?} failed.",
 185                         msg,
 186                         bb_data.terminator().source_info.span
 187                     ),
 188                 );
 189             }
 190
 191             TerminatorKind::SwitchInt {
 192                 discr,
 193                 switch_ty: _,
 194                 values,
 195                 targets,
 196             } => {
 197                 let discr = trans_operand(fx, discr).load_scalar(fx);
 198                 let mut switch = ::cranelift::frontend::Switch::new();
 199                 for (i, value) in values.iter().enumerate() {
 200                     let ebb = fx.get_ebb(targets[i]);
 201                     switch.set_entry(*value as u64, ebb);
 202                 }
 203                 let otherwise_ebb = fx.get_ebb(targets[targets.len() - 1]);
 204                 switch.emit(&mut fx.bcx, discr, otherwise_ebb);
 205             }
 206             TerminatorKind::Call {
 207                 func,
 208                 args,
 209                 destination,
 210                 cleanup: _,
 211                 from_hir_call: _,
 212             } => {
 213                 crate::abi::codegen_terminator_call(
 214                     fx,
 215                     func,
 216                     args,
 217                     destination,
 218                     bb_data.terminator().source_info.span,
 219                 );
 220             }
 221             TerminatorKind::Resume | TerminatorKind::Abort => {
 222                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 223             }
 224             TerminatorKind::Unreachable => {
 225                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 226             }
 227             TerminatorKind::Yield { .. }
 228             | TerminatorKind::FalseEdges { .. }
 229             | TerminatorKind::FalseUnwind { .. }
 230             | TerminatorKind::DropAndReplace { .. }
 231             | TerminatorKind::GeneratorDrop => {
 232                 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
 233             }
 234             TerminatorKind::Drop {
 235                 location,
 236                 target,
 237                 unwind: _,
 238             } => {
 239                 let drop_place = trans_place(fx, location);
 240                 crate::abi::codegen_drop(fx, drop_place);
 241
 242                 let target_ebb = fx.get_ebb(*target);
 243                 fx.bcx.ins().jump(target_ebb, &[]);
 244             }
 245         };
 246     }
 247
 248     fx.bcx.seal_all_blocks();
 249     fx.bcx.finalize();
 250 }
 251
 252 fn trans_stmt<'tcx>(
 253     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 254     cur_ebb: Ebb,
 255     stmt: &Statement<'tcx>,
 256 ) {
 257     let _print_guard = PrintOnPanic(|| format!("stmt {:?}", stmt));
 258
 259     fx.set_debug_loc(stmt.source_info);
 260
 261     #[cfg(debug_assertions)]
 262     match &stmt.kind {
 263         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 264         _ => {
 265             let inst = fx.bcx.func.layout.last_inst(cur_ebb).unwrap();
 266             fx.add_comment(inst, format!("{:?}", stmt));
 267         }
 268     }
 269
 270     match &stmt.kind {
 271         StatementKind::SetDiscriminant {
 272             place,
 273             variant_index,
 274         } => {
 275             let place = trans_place(fx, place);
 276             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 277         }
 278         StatementKind::Assign(to_place_and_rval) => {
 279             let lval = trans_place(fx, &to_place_and_rval.0);
 280             let dest_layout = lval.layout();
 281             match &to_place_and_rval.1 {
 282                 Rvalue::Use(operand) => {
 283                     let val = trans_operand(fx, operand);
 284                     lval.write_cvalue(fx, val);
 285                 }
 286                 Rvalue::Ref(_, _, place) => {
 287                     let place = trans_place(fx, place);
 288                     place.write_place_ref(fx, lval);
 289                 }
 290                 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
 291                     let lhs = trans_operand(fx, lhs);
 292                     let rhs = trans_operand(fx, rhs);
 293
 294                     let res = crate::num::codegen_binop(fx, *bin_op, lhs, rhs);
 295                     lval.write_cvalue(fx, res);
 296                 }
 297                 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
 298                     let lhs = trans_operand(fx, lhs);
 299                     let rhs = trans_operand(fx, rhs);
 300
 301                     let res = if !fx.tcx.sess.overflow_checks() {
 302                         let val =
 303                             crate::num::trans_int_binop(fx, *bin_op, lhs, rhs).load_scalar(fx);
 304                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 305                         CValue::by_val_pair(val, is_overflow, lval.layout())
 306                     } else {
 307                         crate::num::trans_checked_int_binop(fx, *bin_op, lhs, rhs)
 308                     };
 309
 310                     lval.write_cvalue(fx, res);
 311                 }
 312                 Rvalue::UnaryOp(un_op, operand) => {
 313                     let operand = trans_operand(fx, operand);
 314                     let layout = operand.layout();
 315                     let val = operand.load_scalar(fx);
 316                     let res = match un_op {
 317                         UnOp::Not => {
 318                             match layout.ty.kind {
 319                                 ty::Bool => {
 320                                     let val = fx.bcx.ins().uextend(types::I32, val); // WORKAROUND for CraneStation/cranelift#466
 321                                     let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 322                                     CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 323                                 }
 324                                 ty::Uint(_) | ty::Int(_) => {
 325                                     CValue::by_val(fx.bcx.ins().bnot(val), layout)
 326                                 }
 327                                 _ => unimplemented!("un op Not for {:?}", layout.ty),
 328                             }
 329                         }
 330                         UnOp::Neg => match layout.ty.kind {
 331                             ty::Int(_) => {
 332                                 let zero = CValue::const_val(fx, layout.ty, 0);
 333                                 crate::num::trans_int_binop(fx, BinOp::Sub, zero, operand)
 334                             }
 335                             ty::Float(_) => {
 336                                 CValue::by_val(fx.bcx.ins().fneg(val), layout)
 337                             }
 338                             _ => unimplemented!("un op Neg for {:?}", layout.ty),
 339                         },
 340                     };
 341                     lval.write_cvalue(fx, res);
 342                 }
 343                 Rvalue::Cast(CastKind::Pointer(PointerCast::ReifyFnPointer), operand, ty) => {
 344                     let layout = fx.layout_of(ty);
 345                     match fx
 346                         .monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx))
 347                         .kind
 348                     {
 349                         ty::FnDef(def_id, substs) => {
 350                             let func_ref = fx.get_function_ref(
 351                                 Instance::resolve(fx.tcx, ParamEnv::reveal_all(), def_id, substs)
 352                                     .unwrap(),
 353                             );
 354                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 355                             lval.write_cvalue(fx, CValue::by_val(func_addr, layout));
 356                         }
 357                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", ty),
 358                     }
 359                 }
 360                 Rvalue::Cast(CastKind::Pointer(PointerCast::UnsafeFnPointer), operand, ty)
 361                 | Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer), operand, ty)
 362                 | Rvalue::Cast(CastKind::Pointer(PointerCast::ArrayToPointer), operand, ty) => {
 363                     let operand = trans_operand(fx, operand);
 364                     let layout = fx.layout_of(ty);
 365                     lval.write_cvalue(fx, operand.unchecked_cast_to(layout));
 366                 }
 367                 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
 368                     let operand = trans_operand(fx, operand);
 369                     let from_ty = operand.layout().ty;
 370                     let to_ty = fx.monomorphize(to_ty);
 371
 372                     fn is_fat_ptr<'tcx>(
 373                         fx: &FunctionCx<'_, 'tcx, impl Backend>,
 374                         ty: Ty<'tcx>,
 375                     ) -> bool {
 376                         ty.builtin_deref(true)
 377                             .map(
 378                                 |ty::TypeAndMut {
 379                                      ty: pointee_ty,
 380                                      mutbl: _,
 381                                  }| has_ptr_meta(fx.tcx, pointee_ty),
 382                             )
 383                             .unwrap_or(false)
 384                     }
 385
 386                     if is_fat_ptr(fx, from_ty) {
 387                         if is_fat_ptr(fx, to_ty) {
 388                             // fat-ptr -> fat-ptr
 389                             lval.write_cvalue(fx, operand.unchecked_cast_to(dest_layout));
 390                         } else {
 391                             // fat-ptr -> thin-ptr
 392                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 393                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 394                         }
 395                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind {
 396                         // enum -> discriminant value
 397                         assert!(adt_def.is_enum());
 398                         match to_ty.kind {
 399                             ty::Uint(_) | ty::Int(_) => {}
 400                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 401                         }
 402
 403                         let discr = crate::discriminant::codegen_get_discriminant(
 404                             fx,
 405                             operand,
 406                             fx.layout_of(to_ty),
 407                         );
 408                         lval.write_cvalue(fx, discr);
 409                     } else {
 410                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 411                         let from = operand.load_scalar(fx);
 412
 413                         let res = clif_int_or_float_cast(
 414                             fx,
 415                             from,
 416                             type_sign(from_ty),
 417                             to_clif_ty,
 418                             type_sign(to_ty),
 419                         );
 420                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 421                     }
 422                 }
 423                 Rvalue::Cast(CastKind::Pointer(PointerCast::ClosureFnPointer(_)), operand, _ty) => {
 424                     let operand = trans_operand(fx, operand);
 425                     match operand.layout().ty.kind {
 426                         ty::Closure(def_id, substs) => {
 427                             let instance = Instance::resolve_closure(
 428                                 fx.tcx,
 429                                 def_id,
 430                                 substs,
 431                                 ty::ClosureKind::FnOnce,
 432                             );
 433                             let func_ref = fx.get_function_ref(instance);
 434                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 435                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 436                         }
 437                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 438                     }
 439                 }
 440                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), operand, _ty) => {
 441                     let operand = trans_operand(fx, operand);
 442                     operand.unsize_value(fx, lval);
 443                 }
 444                 Rvalue::Discriminant(place) => {
 445                     let place = trans_place(fx, place);
 446                     let value = place.to_cvalue(fx);
 447                     let discr =
 448                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 449                     lval.write_cvalue(fx, discr);
 450                 }
 451                 Rvalue::Repeat(operand, times) => {
 452                     let operand = trans_operand(fx, operand);
 453                     for i in 0..*times {
 454                         let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 455                         let to = lval.place_index(fx, index);
 456                         to.write_cvalue(fx, operand);
 457                     }
 458                 }
 459                 Rvalue::Len(place) => {
 460                     let place = trans_place(fx, place);
 461                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 462                     let len = codegen_array_len(fx, place);
 463                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 464                 }
 465                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 466                     use rustc::middle::lang_items::ExchangeMallocFnLangItem;
 467
 468                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 469                     let layout = fx.layout_of(content_ty);
 470                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 471                     let llalign = fx
 472                         .bcx
 473                         .ins()
 474                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 475                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 476
 477                     // Allocate space:
 478                     let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
 479                         Ok(id) => id,
 480                         Err(s) => {
 481                             fx.tcx
 482                                 .sess
 483                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 484                         }
 485                     };
 486                     let instance = ty::Instance::mono(fx.tcx, def_id);
 487                     let func_ref = fx.get_function_ref(instance);
 488                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 489                     let ptr = fx.bcx.inst_results(call)[0];
 490                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 491                 }
 492                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 493                     assert!(lval
 494                         .layout()
 495                         .ty
 496                         .is_sized(fx.tcx.at(DUMMY_SP), ParamEnv::reveal_all()));
 497                     let ty_size = fx.layout_of(ty).size.bytes();
 498                     let val = CValue::const_val(fx, fx.tcx.types.usize, ty_size.into());
 499                     lval.write_cvalue(fx, val);
 500                 }
 501                 Rvalue::Aggregate(kind, operands) => match **kind {
 502                     AggregateKind::Array(_ty) => {
 503                         for (i, operand) in operands.into_iter().enumerate() {
 504                             let operand = trans_operand(fx, operand);
 505                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 506                             let to = lval.place_index(fx, index);
 507                             to.write_cvalue(fx, operand);
 508                         }
 509                     }
 510                     _ => unreachable!("shouldn't exist at trans {:?}", to_place_and_rval.1),
 511                 },
 512             }
 513         }
 514         StatementKind::StorageLive(_)
 515         | StatementKind::StorageDead(_)
 516         | StatementKind::Nop
 517         | StatementKind::FakeRead(..)
 518         | StatementKind::Retag { .. }
 519         | StatementKind::AscribeUserType(..) => {}
 520
 521         StatementKind::InlineAsm(asm) => {
 522             use syntax::ast::Name;
 523             let InlineAsm {
 524                 asm,
 525                 outputs: _,
 526                 inputs: _,
 527             } = &**asm;
 528             let rustc::hir::InlineAsmInner {
 529                 asm: asm_code, // Name
 530                 outputs,       // Vec<Name>
 531                 inputs,        // Vec<Name>
 532                 clobbers,      // Vec<Name>
 533                 volatile,      // bool
 534                 alignstack,    // bool
 535                 dialect: _,    // syntax::ast::AsmDialect
 536                 asm_str_style: _,
 537             } = asm;
 538             match &*asm_code.as_str() {
 539                 "" => {
 540                     assert_eq!(inputs, &[Name::intern("r")]);
 541                     assert!(outputs.is_empty(), "{:?}", outputs);
 542
 543                     // Black box
 544                 }
 545                 "cpuid" | "cpuid\n" => {
 546                     assert_eq!(inputs, &[Name::intern("{eax}"), Name::intern("{ecx}")]);
 547
 548                     assert_eq!(outputs.len(), 4);
 549                     for (i, c) in (&["={eax}", "={ebx}", "={ecx}", "={edx}"])
 550                         .iter()
 551                         .enumerate()
 552                     {
 553                         assert_eq!(&outputs[i].constraint.as_str(), c);
 554                         assert!(!outputs[i].is_rw);
 555                         assert!(!outputs[i].is_indirect);
 556                     }
 557
 558                     assert_eq!(clobbers, &[Name::intern("rbx")]);
 559
 560                     assert!(!volatile);
 561                     assert!(!alignstack);
 562
 563                     crate::trap::trap_unimplemented(
 564                         fx,
 565                         "__cpuid_count arch intrinsic is not supported",
 566                     );
 567                 }
 568                 "xgetbv" => {
 569                     assert_eq!(inputs, &[Name::intern("{ecx}")]);
 570
 571                     assert_eq!(outputs.len(), 2);
 572                     for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
 573                         assert_eq!(&outputs[i].constraint.as_str(), c);
 574                         assert!(!outputs[i].is_rw);
 575                         assert!(!outputs[i].is_indirect);
 576                     }
 577
 578                     assert_eq!(clobbers, &[]);
 579
 580                     assert!(!volatile);
 581                     assert!(!alignstack);
 582
 583                     crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
 584                 }
 585                 _ if fx.tcx.symbol_name(fx.instance).name.as_str() == "__rust_probestack" => {
 586                     crate::trap::trap_unimplemented(fx, "__rust_probestack is not supported");
 587                 }
 588                 _ => unimpl!("Inline assembly is not supported"),
 589             }
 590         }
 591     }
 592 }
 593
 594 fn codegen_array_len<'tcx>(
 595     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 596     place: CPlace<'tcx>,
 597 ) -> Value {
 598     match place.layout().ty.kind {
 599         ty::Array(_elem_ty, len) => {
 600             let len = crate::constant::force_eval_const(fx, len)
 601                 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 602             fx.bcx.ins().iconst(fx.pointer_type, len)
 603         }
 604         ty::Slice(_elem_ty) => place
 605             .to_addr_maybe_unsized(fx)
 606             .1
 607             .expect("Length metadata for slice place"),
 608         _ => bug!("Rvalue::Len({:?})", place),
 609     }
 610 }
 611
 612 pub fn trans_place<'tcx>(
 613     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 614     place: &Place<'tcx>,
 615 ) -> CPlace<'tcx> {
 616     let mut cplace = match &place.base {
 617         PlaceBase::Local(local) => fx.get_local_place(*local),
 618         PlaceBase::Static(static_) => match static_.kind {
 619             StaticKind::Static => {
 620                 crate::constant::codegen_static_ref(fx, static_.def_id, static_.ty)
 621             }
 622             StaticKind::Promoted(promoted, substs) => {
 623                 let instance = Instance::new(static_.def_id, fx.monomorphize(&substs));
 624                 crate::constant::trans_promoted(fx, instance, promoted, static_.ty)
 625             }
 626         },
 627     };
 628
 629     for elem in &*place.projection {
 630         match *elem {
 631             PlaceElem::Deref => {
 632                 cplace = cplace.place_deref(fx);
 633             }
 634             PlaceElem::Field(field, _ty) => {
 635                 cplace = cplace.place_field(fx, field);
 636             }
 637             PlaceElem::Index(local) => {
 638                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 639                 cplace = cplace.place_index(fx, index);
 640             }
 641             PlaceElem::ConstantIndex {
 642                 offset,
 643                 min_length: _,
 644                 from_end,
 645             } => {
 646                 let index = if !from_end {
 647                     fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 648                 } else {
 649                     let len = codegen_array_len(fx, cplace);
 650                     fx.bcx.ins().iadd_imm(len, -(offset as i64))
 651                 };
 652                 cplace = cplace.place_index(fx, index);
 653             }
 654             PlaceElem::Subslice { from, to, from_end } => {
 655                 // These indices are generated by slice patterns.
 656                 // slice[from:-to] in Python terms.
 657
 658                 match cplace.layout().ty.kind {
 659                     ty::Array(elem_ty, len) => {
 660                         let elem_layout = fx.layout_of(elem_ty);
 661                         let ptr = cplace.to_addr(fx);
 662                         let len = crate::constant::force_eval_const(fx, len)
 663                             .eval_usize(fx.tcx, ParamEnv::reveal_all());
 664                         cplace = CPlace::for_addr(
 665                             fx.bcx
 666                                 .ins()
 667                                 .iadd_imm(ptr, elem_layout.size.bytes() as i64 * from as i64),
 668                             fx.layout_of(fx.tcx.mk_array(elem_ty, len - from as u64 - to as u64)),
 669                         );
 670                     }
 671                     ty::Slice(elem_ty) => {
 672                         assert!(from_end, "slice subslices should be `from_end`");
 673                         let elem_layout = fx.layout_of(elem_ty);
 674                         let (ptr, len) = cplace.to_addr_maybe_unsized(fx);
 675                         let len = len.unwrap();
 676                         cplace = CPlace::for_addr_with_extra(
 677                             fx.bcx
 678                                 .ins()
 679                                 .iadd_imm(ptr, elem_layout.size.bytes() as i64 * from as i64),
 680                             fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
 681                             cplace.layout(),
 682                         );
 683                     }
 684                     _ => unreachable!(),
 685                 }
 686             }
 687             PlaceElem::Downcast(_adt_def, variant) => {
 688                 cplace = cplace.downcast_variant(fx, variant);
 689             }
 690         }
 691     }
 692
 693     cplace
 694 }
 695
 696 pub fn trans_operand<'tcx>(
 697     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 698     operand: &Operand<'tcx>,
 699 ) -> CValue<'tcx> {
 700     match operand {
 701         Operand::Move(place) | Operand::Copy(place) => {
 702             let cplace = trans_place(fx, place);
 703             cplace.to_cvalue(fx)
 704         }
 705         Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),
 706     }
 707 }