src/base.rs

   1 use rustc_middle::ty::adjustment::PointerCast;
   2 use rustc_index::vec::IndexVec;
   3
   4 use crate::prelude::*;
   5
   6 pub(crate) fn trans_fn<'tcx, B: Backend + 'static>(
   7     cx: &mut crate::CodegenCx<'tcx, B>,
   8     instance: Instance<'tcx>,
   9     linkage: Linkage,
  10 ) {
  11     let tcx = cx.tcx;
  12
  13     let mir = tcx.instance_mir(instance.def);
  14
  15     // Declare function
  16     let (name, sig) = get_function_name_and_sig(tcx, cx.module.isa().triple(), instance, false);
  17     let func_id = cx.module.declare_function(&name, linkage, &sig).unwrap();
  18
  19     // Make FunctionBuilder
  20     let context = &mut cx.cached_context;
  21     context.clear();
  22     context.func.name = ExternalName::user(0, func_id.as_u32());
  23     context.func.signature = sig;
  24     context.func.collect_debug_info();
  25     let mut func_ctx = FunctionBuilderContext::new();
  26     let mut bcx = FunctionBuilder::new(&mut context.func, &mut func_ctx);
  27
  28     // Predefine blocks
  29     let start_block = bcx.create_block();
  30     let block_map: IndexVec<BasicBlock, Block> = (0..mir.basic_blocks().len()).map(|_| bcx.create_block()).collect();
  31
  32     // Make FunctionCx
  33     let pointer_type = cx.module.target_config().pointer_type();
  34     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  35
  36     let mut fx = FunctionCx {
  37         tcx,
  38         module: &mut cx.module,
  39         global_asm: &mut cx.global_asm,
  40         pointer_type,
  41
  42         instance,
  43         mir,
  44
  45         bcx,
  46         block_map,
  47         local_map: FxHashMap::with_capacity_and_hasher(mir.local_decls.len(), Default::default()),
  48         caller_location: None, // set by `codegen_fn_prelude`
  49         cold_blocks: EntitySet::new(),
  50
  51         clif_comments,
  52         constants_cx: &mut cx.constants_cx,
  53         vtables: &mut cx.vtables,
  54         source_info_set: indexmap::IndexSet::new(),
  55         next_ssa_var: 0,
  56
  57         inline_asm_index: 0,
  58     };
  59
  60     let arg_uninhabited = fx.mir.args_iter().any(|arg| fx.layout_of(fx.monomorphize(&fx.mir.local_decls[arg].ty)).abi.is_uninhabited());
  61
  62     if arg_uninhabited {
  63         fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
  64         fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
  65         crate::trap::trap_unreachable(&mut fx, "function has uninhabited argument");
  66     } else {
  67         tcx.sess.time("codegen clif ir", || {
  68             tcx.sess.time("codegen prelude", || crate::abi::codegen_fn_prelude(&mut fx, start_block));
  69             codegen_fn_content(&mut fx);
  70         });
  71     }
  72
  73     // Recover all necessary data from fx, before accessing func will prevent future access to it.
  74     let instance = fx.instance;
  75     let mut clif_comments = fx.clif_comments;
  76     let source_info_set = fx.source_info_set;
  77     let local_map = fx.local_map;
  78     let cold_blocks = fx.cold_blocks;
  79
  80     crate::pretty_clif::write_clif_file(
  81         cx.tcx,
  82         "unopt",
  83         None,
  84         instance,
  85         &context,
  86         &clif_comments,
  87     );
  88
  89     // Verify function
  90     verify_func(tcx, &clif_comments, &context.func);
  91
  92     // Perform rust specific optimizations
  93     tcx.sess.time("optimize clif ir", || {
  94         crate::optimize::optimize_function(tcx, instance, context, &cold_blocks, &mut clif_comments);
  95     });
  96
  97     // If the return block is not reachable, then the SSA builder may have inserted a `iconst.i128`
  98     // instruction, which doesn't have an encoding.
  99     context.compute_cfg();
 100     context.compute_domtree();
 101     context.eliminate_unreachable_code(cx.module.isa()).unwrap();
 102
 103     // Define function
 104     let module = &mut cx.module;
 105     tcx.sess.time(
 106         "define function",
 107         || module.define_function(
 108             func_id,
 109             context,
 110             &mut cranelift_codegen::binemit::NullTrapSink {},
 111         ).unwrap(),
 112     );
 113
 114     // Write optimized function to file for debugging
 115     crate::pretty_clif::write_clif_file(
 116         cx.tcx,
 117         "opt",
 118         Some(cx.module.isa()),
 119         instance,
 120         &context,
 121         &clif_comments,
 122     );
 123
 124     // Define debuginfo for function
 125     let isa = cx.module.isa();
 126     let debug_context = &mut cx.debug_context;
 127     let unwind_context = &mut cx.unwind_context;
 128     tcx.sess.time("generate debug info", || {
 129         if let Some(debug_context) = debug_context {
 130             debug_context.define_function(instance, func_id, &name, isa, context, &source_info_set, local_map);
 131         }
 132         unwind_context.add_function(func_id, &context, isa);
 133     });
 134
 135     // Clear context to make it usable for the next function
 136     context.clear();
 137 }
 138
 139 pub(crate) fn verify_func(tcx: TyCtxt<'_>, writer: &crate::pretty_clif::CommentWriter, func: &Function) {
 140     tcx.sess.time("verify clif ir", || {
 141         let flags = cranelift_codegen::settings::Flags::new(cranelift_codegen::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
 159 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Backend>) {
 160     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 161         let block = fx.get_block(bb);
 162         fx.bcx.switch_to_block(block);
 163
 164         if bb_data.is_cleanup {
 165             // Unwinding after panicking is not supported
 166             continue;
 167
 168             // FIXME once unwinding is supported uncomment next lines
 169             // // Unwinding is unlikely to happen, so mark cleanup block's as cold.
 170             // fx.cold_blocks.insert(block);
 171         }
 172
 173         fx.bcx.ins().nop();
 174         for stmt in &bb_data.statements {
 175             fx.set_debug_loc(stmt.source_info);
 176             trans_stmt(fx, block, stmt);
 177         }
 178
 179         #[cfg(debug_assertions)]
 180         {
 181             let mut terminator_head = "\n".to_string();
 182             bb_data
 183                 .terminator()
 184                 .kind
 185                 .fmt_head(&mut terminator_head)
 186                 .unwrap();
 187             let inst = fx.bcx.func.layout.last_inst(block).unwrap();
 188             fx.add_comment(inst, terminator_head);
 189         }
 190
 191         fx.set_debug_loc(bb_data.terminator().source_info);
 192
 193         match &bb_data.terminator().kind {
 194             TerminatorKind::Goto { target } => {
 195                 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
 196                     let mut can_immediately_return = true;
 197                     for stmt in &fx.mir[*target].statements {
 198                         if let StatementKind::StorageDead(_) = stmt.kind {
 199                         } else {
 200                             // FIXME Can sometimes happen, see rust-lang/rust#70531
 201                             can_immediately_return = false;
 202                             break;
 203                         }
 204                     }
 205
 206                     if can_immediately_return {
 207                         crate::abi::codegen_return(fx);
 208                         continue;
 209                     }
 210                 }
 211
 212                 let block = fx.get_block(*target);
 213                 fx.bcx.ins().jump(block, &[]);
 214             }
 215             TerminatorKind::Return => {
 216                 crate::abi::codegen_return(fx);
 217             }
 218             TerminatorKind::Assert {
 219                 cond,
 220                 expected,
 221                 msg,
 222                 target,
 223                 cleanup: _,
 224             } => {
 225                 if !fx.tcx.sess.overflow_checks() {
 226                     if let mir::AssertKind::OverflowNeg(_) = *msg {
 227                         let target = fx.get_block(*target);
 228                         fx.bcx.ins().jump(target, &[]);
 229                         continue;
 230                     }
 231                 }
 232                 let cond = trans_operand(fx, cond).load_scalar(fx);
 233
 234                 let target = fx.get_block(*target);
 235                 let failure = fx.bcx.create_block();
 236                 fx.cold_blocks.insert(failure);
 237
 238                 if *expected {
 239                     fx.bcx.ins().brz(cond, failure, &[]);
 240                 } else {
 241                     fx.bcx.ins().brnz(cond, failure, &[]);
 242                 };
 243                 fx.bcx.ins().jump(target, &[]);
 244
 245                 fx.bcx.switch_to_block(failure);
 246
 247                 let location = fx.get_caller_location(bb_data.terminator().source_info.span).load_scalar(fx);
 248
 249                 let args;
 250                 let lang_item = match msg {
 251                     AssertKind::BoundsCheck { ref len, ref index } => {
 252                         let len = trans_operand(fx, len).load_scalar(fx);
 253                         let index = trans_operand(fx, index).load_scalar(fx);
 254                         args = [index, len, location];
 255                         rustc_hir::lang_items::PanicBoundsCheckFnLangItem
 256                     }
 257                     _ => {
 258                         let msg_str = msg.description();
 259                         let msg_ptr = fx.anonymous_str("assert", msg_str);
 260                         let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
 261                         args = [msg_ptr, msg_len, location];
 262                         rustc_hir::lang_items::PanicFnLangItem
 263                     }
 264                 };
 265
 266                 let def_id = fx.tcx.lang_items().require(lang_item).unwrap_or_else(|s| {
 267                     fx.tcx.sess.span_fatal(bb_data.terminator().source_info.span, &s)
 268                 });
 269
 270                 let instance = Instance::mono(fx.tcx, def_id);
 271                 let symbol_name = fx.tcx.symbol_name(instance).name;
 272
 273                 fx.lib_call(&*symbol_name, vec![fx.pointer_type, fx.pointer_type, fx.pointer_type], vec![], &args);
 274
 275                 crate::trap::trap_unreachable(fx, "panic lang item returned");
 276             }
 277
 278             TerminatorKind::SwitchInt {
 279                 discr,
 280                 switch_ty: _,
 281                 values,
 282                 targets,
 283             } => {
 284                 let discr = trans_operand(fx, discr).load_scalar(fx);
 285                 let mut switch = ::cranelift_frontend::Switch::new();
 286                 for (i, value) in values.iter().enumerate() {
 287                     let block = fx.get_block(targets[i]);
 288                     switch.set_entry(*value, block);
 289                 }
 290                 let otherwise_block = fx.get_block(targets[targets.len() - 1]);
 291                 switch.emit(&mut fx.bcx, discr, otherwise_block);
 292             }
 293             TerminatorKind::Call {
 294                 func,
 295                 args,
 296                 destination,
 297                 fn_span,
 298                 cleanup: _,
 299                 from_hir_call: _,
 300             } => {
 301                 fx.tcx.sess.time("codegen call", || crate::abi::codegen_terminator_call(
 302                     fx,
 303                     *fn_span,
 304                     block,
 305                     func,
 306                     args,
 307                     *destination,
 308                 ));
 309             }
 310             TerminatorKind::InlineAsm {
 311                 template,
 312                 operands,
 313                 options,
 314                 destination,
 315                 line_spans: _,
 316             } => {
 317                 crate::inline_asm::codegen_inline_asm(
 318                     fx,
 319                     bb_data.terminator().source_info.span,
 320                     template,
 321                     operands,
 322                     *options,
 323                 );
 324
 325                 match *destination {
 326                     Some(destination) => {
 327                         let destination_block = fx.get_block(destination);
 328                         fx.bcx.ins().jump(destination_block, &[]);
 329                     }
 330                     None => {
 331                         crate::trap::trap_unreachable(fx, "[corruption] Returned from noreturn inline asm");
 332                     }
 333                 }
 334             }
 335             TerminatorKind::Resume | TerminatorKind::Abort => {
 336                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 337             }
 338             TerminatorKind::Unreachable => {
 339                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 340             }
 341             TerminatorKind::Yield { .. }
 342             | TerminatorKind::FalseEdge { .. }
 343             | TerminatorKind::FalseUnwind { .. }
 344             | TerminatorKind::DropAndReplace { .. }
 345             | TerminatorKind::GeneratorDrop => {
 346                 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
 347             }
 348             TerminatorKind::Drop {
 349                 place,
 350                 target,
 351                 unwind: _,
 352             } => {
 353                 let drop_place = trans_place(fx, *place);
 354                 crate::abi::codegen_drop(fx, bb_data.terminator().source_info.span, drop_place);
 355
 356                 let target_block = fx.get_block(*target);
 357                 fx.bcx.ins().jump(target_block, &[]);
 358             }
 359         };
 360     }
 361
 362     fx.bcx.seal_all_blocks();
 363     fx.bcx.finalize();
 364 }
 365
 366 fn trans_stmt<'tcx>(
 367     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 368     #[allow(unused_variables)]
 369     cur_block: Block,
 370     stmt: &Statement<'tcx>,
 371 ) {
 372     let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
 373
 374     fx.set_debug_loc(stmt.source_info);
 375
 376     #[cfg(false_debug_assertions)]
 377     match &stmt.kind {
 378         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 379         _ => {
 380             let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
 381             fx.add_comment(inst, format!("{:?}", stmt));
 382         }
 383     }
 384
 385     match &stmt.kind {
 386         StatementKind::SetDiscriminant {
 387             place,
 388             variant_index,
 389         } => {
 390             let place = trans_place(fx, **place);
 391             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 392         }
 393         StatementKind::Assign(to_place_and_rval) => {
 394             let lval = trans_place(fx, to_place_and_rval.0);
 395             let dest_layout = lval.layout();
 396             match &to_place_and_rval.1 {
 397                 Rvalue::Use(operand) => {
 398                     let val = trans_operand(fx, operand);
 399                     lval.write_cvalue(fx, val);
 400                 }
 401                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
 402                     let place = trans_place(fx, *place);
 403                     place.write_place_ref(fx, lval);
 404                 }
 405                 Rvalue::ThreadLocalRef(def_id) => {
 406                     let val = crate::constant::codegen_tls_ref(fx, *def_id, lval.layout());
 407                     lval.write_cvalue(fx, val);
 408                 }
 409                 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
 410                     let lhs = trans_operand(fx, lhs);
 411                     let rhs = trans_operand(fx, rhs);
 412
 413                     let res = crate::num::codegen_binop(fx, *bin_op, lhs, rhs);
 414                     lval.write_cvalue(fx, res);
 415                 }
 416                 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
 417                     let lhs = trans_operand(fx, lhs);
 418                     let rhs = trans_operand(fx, rhs);
 419
 420                     let res = if !fx.tcx.sess.overflow_checks() {
 421                         let val =
 422                             crate::num::trans_int_binop(fx, *bin_op, lhs, rhs).load_scalar(fx);
 423                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 424                         CValue::by_val_pair(val, is_overflow, lval.layout())
 425                     } else {
 426                         crate::num::trans_checked_int_binop(fx, *bin_op, lhs, rhs)
 427                     };
 428
 429                     lval.write_cvalue(fx, res);
 430                 }
 431                 Rvalue::UnaryOp(un_op, operand) => {
 432                     let operand = trans_operand(fx, operand);
 433                     let layout = operand.layout();
 434                     let val = operand.load_scalar(fx);
 435                     let res = match un_op {
 436                         UnOp::Not => {
 437                             match layout.ty.kind {
 438                                 ty::Bool => {
 439                                     let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 440                                     CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 441                                 }
 442                                 ty::Uint(_) | ty::Int(_) => {
 443                                     CValue::by_val(fx.bcx.ins().bnot(val), layout)
 444                                 }
 445                                 _ => unreachable!("un op Not for {:?}", layout.ty),
 446                             }
 447                         }
 448                         UnOp::Neg => match layout.ty.kind {
 449                             ty::Int(IntTy::I128) => {
 450                                 // FIXME remove this case once ineg.i128 works
 451                                 let zero = CValue::const_val(fx, layout, 0);
 452                                 crate::num::trans_int_binop(fx, BinOp::Sub, zero, operand)
 453                             }
 454                             ty::Int(_) => {
 455                                 CValue::by_val(fx.bcx.ins().ineg(val), layout)
 456                             }
 457                             ty::Float(_) => {
 458                                 CValue::by_val(fx.bcx.ins().fneg(val), layout)
 459                             }
 460                             _ => unreachable!("un op Neg for {:?}", layout.ty),
 461                         },
 462                     };
 463                     lval.write_cvalue(fx, res);
 464                 }
 465                 Rvalue::Cast(CastKind::Pointer(PointerCast::ReifyFnPointer), operand, to_ty) => {
 466                     let from_ty = fx.monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx));
 467                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 468                     match from_ty.kind {
 469                         ty::FnDef(def_id, substs) => {
 470                             let func_ref = fx.get_function_ref(
 471                                 Instance::resolve_for_fn_ptr(fx.tcx, ParamEnv::reveal_all(), def_id, substs)
 472                                     .unwrap(),
 473                             );
 474                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 475                             lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
 476                         }
 477                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
 478                     }
 479                 }
 480                 Rvalue::Cast(CastKind::Pointer(PointerCast::UnsafeFnPointer), operand, to_ty)
 481                 | Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer), operand, to_ty)
 482                 | Rvalue::Cast(CastKind::Pointer(PointerCast::ArrayToPointer), operand, to_ty) => {
 483                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 484                     let operand = trans_operand(fx, operand);
 485                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
 486                 }
 487                 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
 488                     let operand = trans_operand(fx, operand);
 489                     let from_ty = operand.layout().ty;
 490                     let to_ty = fx.monomorphize(to_ty);
 491
 492                     fn is_fat_ptr<'tcx>(
 493                         fx: &FunctionCx<'_, 'tcx, impl Backend>,
 494                         ty: Ty<'tcx>,
 495                     ) -> bool {
 496                         ty.builtin_deref(true)
 497                             .map(
 498                                 |ty::TypeAndMut {
 499                                      ty: pointee_ty,
 500                                      mutbl: _,
 501                                  }| has_ptr_meta(fx.tcx, pointee_ty),
 502                             )
 503                             .unwrap_or(false)
 504                     }
 505
 506                     if is_fat_ptr(fx, from_ty) {
 507                         if is_fat_ptr(fx, to_ty) {
 508                             // fat-ptr -> fat-ptr
 509                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
 510                         } else {
 511                             // fat-ptr -> thin-ptr
 512                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 513                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 514                         }
 515                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind {
 516                         // enum -> discriminant value
 517                         assert!(adt_def.is_enum());
 518                         match to_ty.kind {
 519                             ty::Uint(_) | ty::Int(_) => {}
 520                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 521                         }
 522
 523                         use rustc_target::abi::{TagEncoding, Int, Variants};
 524
 525                         match &operand.layout().variants {
 526                             Variants::Single { index } => {
 527                                 let discr = operand.layout().ty.discriminant_for_variant(fx.tcx, *index).unwrap();
 528                                 let discr = if discr.ty.is_signed() {
 529                                     rustc_middle::mir::interpret::sign_extend(discr.val, fx.layout_of(discr.ty).size)
 530                                 } else {
 531                                     discr.val
 532                                 };
 533
 534                                 let discr = CValue::const_val(fx, fx.layout_of(to_ty), discr);
 535                                 lval.write_cvalue(fx, discr);
 536                             }
 537                             Variants::Multiple {
 538                                 tag,
 539                                 tag_field,
 540                                 tag_encoding: TagEncoding::Direct,
 541                                 variants: _,
 542                             } => {
 543                                 let cast_to = fx.clif_type(dest_layout.ty).unwrap();
 544
 545                                 // Read the tag/niche-encoded discriminant from memory.
 546                                 let encoded_discr = operand.value_field(fx, mir::Field::new(*tag_field));
 547                                 let encoded_discr = encoded_discr.load_scalar(fx);
 548
 549                                 // Decode the discriminant (specifically if it's niche-encoded).
 550                                 let signed = match tag.value {
 551                                     Int(_, signed) => signed,
 552                                     _ => false,
 553                                 };
 554                                 let val = clif_intcast(fx, encoded_discr, cast_to, signed);
 555                                 let val = CValue::by_val(val, dest_layout);
 556                                 lval.write_cvalue(fx, val);
 557                             }
 558                             Variants::Multiple { ..} => unreachable!(),
 559                         }
 560                     } else {
 561                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 562                         let from = operand.load_scalar(fx);
 563
 564                         let res = clif_int_or_float_cast(
 565                             fx,
 566                             from,
 567                             type_sign(from_ty),
 568                             to_clif_ty,
 569                             type_sign(to_ty),
 570                         );
 571                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 572                     }
 573                 }
 574                 Rvalue::Cast(CastKind::Pointer(PointerCast::ClosureFnPointer(_)), operand, _to_ty) => {
 575                     let operand = trans_operand(fx, operand);
 576                     match operand.layout().ty.kind {
 577                         ty::Closure(def_id, substs) => {
 578                             let instance = Instance::resolve_closure(
 579                                 fx.tcx,
 580                                 def_id,
 581                                 substs,
 582                                 ty::ClosureKind::FnOnce,
 583                             );
 584                             let func_ref = fx.get_function_ref(instance);
 585                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 586                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 587                         }
 588                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 589                     }
 590                 }
 591                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), operand, _to_ty) => {
 592                     let operand = trans_operand(fx, operand);
 593                     operand.unsize_value(fx, lval);
 594                 }
 595                 Rvalue::Discriminant(place) => {
 596                     let place = trans_place(fx, *place);
 597                     let value = place.to_cvalue(fx);
 598                     let discr =
 599                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 600                     lval.write_cvalue(fx, discr);
 601                 }
 602                 Rvalue::Repeat(operand, times) => {
 603                     let operand = trans_operand(fx, operand);
 604                     let times = fx
 605                         .monomorphize(times)
 606                         .eval(fx.tcx, ParamEnv::reveal_all())
 607                         .val
 608                         .try_to_bits(fx.tcx.data_layout.pointer_size)
 609                         .unwrap();
 610                     for i in 0..times {
 611                         let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 612                         let to = lval.place_index(fx, index);
 613                         to.write_cvalue(fx, operand);
 614                     }
 615                 }
 616                 Rvalue::Len(place) => {
 617                     let place = trans_place(fx, *place);
 618                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 619                     let len = codegen_array_len(fx, place);
 620                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 621                 }
 622                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 623                     use rustc_hir::lang_items::ExchangeMallocFnLangItem;
 624
 625                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 626                     let content_ty = fx.monomorphize(content_ty);
 627                     let layout = fx.layout_of(content_ty);
 628                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 629                     let llalign = fx
 630                         .bcx
 631                         .ins()
 632                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 633                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 634
 635                     // Allocate space:
 636                     let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
 637                         Ok(id) => id,
 638                         Err(s) => {
 639                             fx.tcx
 640                                 .sess
 641                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 642                         }
 643                     };
 644                     let instance = ty::Instance::mono(fx.tcx, def_id);
 645                     let func_ref = fx.get_function_ref(instance);
 646                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 647                     let ptr = fx.bcx.inst_results(call)[0];
 648                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 649                 }
 650                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 651                     assert!(lval
 652                         .layout()
 653                         .ty
 654                         .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all()));
 655                     let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
 656                     let val = CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
 657                     lval.write_cvalue(fx, val);
 658                 }
 659                 Rvalue::Aggregate(kind, operands) => match **kind {
 660                     AggregateKind::Array(_ty) => {
 661                         for (i, operand) in operands.into_iter().enumerate() {
 662                             let operand = trans_operand(fx, operand);
 663                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 664                             let to = lval.place_index(fx, index);
 665                             to.write_cvalue(fx, operand);
 666                         }
 667                     }
 668                     _ => unreachable!("shouldn't exist at trans {:?}", to_place_and_rval.1),
 669                 },
 670             }
 671         }
 672         StatementKind::StorageLive(_)
 673         | StatementKind::StorageDead(_)
 674         | StatementKind::Nop
 675         | StatementKind::FakeRead(..)
 676         | StatementKind::Retag { .. }
 677         | StatementKind::AscribeUserType(..) => {}
 678
 679         StatementKind::LlvmInlineAsm(asm) => {
 680             use rustc_span::symbol::Symbol;
 681             let LlvmInlineAsm {
 682                 asm,
 683                 outputs: _,
 684                 inputs: _,
 685             } = &**asm;
 686             let rustc_hir::LlvmInlineAsmInner {
 687                 asm: asm_code, // Name
 688                 outputs,       // Vec<Name>
 689                 inputs,        // Vec<Name>
 690                 clobbers,      // Vec<Name>
 691                 volatile,      // bool
 692                 alignstack,    // bool
 693                 dialect: _,    // rustc_ast::ast::AsmDialect
 694                 asm_str_style: _,
 695             } = asm;
 696             match &*asm_code.as_str() {
 697                 "" => {
 698                     // Black box
 699                 }
 700                 cpuid if cpuid.contains("cpuid") => {
 701                     crate::trap::trap_unimplemented(
 702                         fx,
 703                         "__cpuid_count arch intrinsic is not supported",
 704                     );
 705                 }
 706                 "xgetbv" => {
 707                     assert_eq!(inputs, &[Symbol::intern("{ecx}")]);
 708
 709                     assert_eq!(outputs.len(), 2);
 710                     for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
 711                         assert_eq!(&outputs[i].constraint.as_str(), c);
 712                         assert!(!outputs[i].is_rw);
 713                         assert!(!outputs[i].is_indirect);
 714                     }
 715
 716                     assert_eq!(clobbers, &[]);
 717
 718                     assert!(!volatile);
 719                     assert!(!alignstack);
 720
 721                     crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
 722                 }
 723                 // ___chkstk, ___chkstk_ms and __alloca are only used on Windows
 724                 _ if fx.tcx.symbol_name(fx.instance).name.starts_with("___chkstk") => {
 725                     crate::trap::trap_unimplemented(fx, "Stack probes are not supported");
 726                 }
 727                 _ if fx.tcx.symbol_name(fx.instance).name == "__alloca" => {
 728                     crate::trap::trap_unimplemented(fx, "Alloca is not supported");
 729                 }
 730                 // Used in sys::windows::abort_internal
 731                 "int $$0x29" => {
 732                     crate::trap::trap_unimplemented(fx, "Windows abort");
 733                 }
 734                 _ => fx.tcx.sess.span_fatal(stmt.source_info.span, "Inline assembly is not supported"),
 735             }
 736         }
 737     }
 738 }
 739
 740 fn codegen_array_len<'tcx>(
 741     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 742     place: CPlace<'tcx>,
 743 ) -> Value {
 744     match place.layout().ty.kind {
 745         ty::Array(_elem_ty, len) => {
 746             let len = fx.monomorphize(&len)
 747                 .eval(fx.tcx, ParamEnv::reveal_all())
 748                 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 749             fx.bcx.ins().iconst(fx.pointer_type, len)
 750         }
 751         ty::Slice(_elem_ty) => place
 752             .to_ptr_maybe_unsized()
 753             .1
 754             .expect("Length metadata for slice place"),
 755         _ => bug!("Rvalue::Len({:?})", place),
 756     }
 757 }
 758
 759 pub(crate) fn trans_place<'tcx>(
 760     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 761     place: Place<'tcx>,
 762 ) -> CPlace<'tcx> {
 763     let mut cplace = fx.get_local_place(place.local);
 764
 765     for elem in place.projection {
 766         match elem {
 767             PlaceElem::Deref => {
 768                 cplace = cplace.place_deref(fx);
 769             }
 770             PlaceElem::Field(field, _ty) => {
 771                 cplace = cplace.place_field(fx, field);
 772             }
 773             PlaceElem::Index(local) => {
 774                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 775                 cplace = cplace.place_index(fx, index);
 776             }
 777             PlaceElem::ConstantIndex {
 778                 offset,
 779                 min_length: _,
 780                 from_end,
 781             } => {
 782                 let index = if !from_end {
 783                     fx.bcx.ins().iconst(fx.pointer_type, i64::from(offset))
 784                 } else {
 785                     let len = codegen_array_len(fx, cplace);
 786                     fx.bcx.ins().iadd_imm(len, -i64::from(offset))
 787                 };
 788                 cplace = cplace.place_index(fx, index);
 789             }
 790             PlaceElem::Subslice { from, to, from_end } => {
 791                 // These indices are generated by slice patterns.
 792                 // slice[from:-to] in Python terms.
 793
 794                 match cplace.layout().ty.kind {
 795                     ty::Array(elem_ty, _len) => {
 796                         assert!(!from_end, "array subslices are never `from_end`");
 797                         let elem_layout = fx.layout_of(elem_ty);
 798                         let ptr = cplace.to_ptr();
 799                         cplace = CPlace::for_ptr(
 800                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * i64::from(from)),
 801                             fx.layout_of(fx.tcx.mk_array(elem_ty, u64::from(to) - u64::from(from))),
 802                         );
 803                     }
 804                     ty::Slice(elem_ty) => {
 805                         assert!(from_end, "slice subslices should be `from_end`");
 806                         let elem_layout = fx.layout_of(elem_ty);
 807                         let (ptr, len) = cplace.to_ptr_maybe_unsized();
 808                         let len = len.unwrap();
 809                         cplace = CPlace::for_ptr_with_extra(
 810                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * i64::from(from)),
 811                             fx.bcx.ins().iadd_imm(len, -(i64::from(from) + i64::from(to))),
 812                             cplace.layout(),
 813                         );
 814                     }
 815                     _ => unreachable!(),
 816                 }
 817             }
 818             PlaceElem::Downcast(_adt_def, variant) => {
 819                 cplace = cplace.downcast_variant(fx, variant);
 820             }
 821         }
 822     }
 823
 824     cplace
 825 }
 826
 827 pub(crate) fn trans_operand<'tcx>(
 828     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 829     operand: &Operand<'tcx>,
 830 ) -> CValue<'tcx> {
 831     match operand {
 832         Operand::Move(place) | Operand::Copy(place) => {
 833             let cplace = trans_place(fx, *place);
 834             cplace.to_cvalue(fx)
 835         }
 836         Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),
 837     }
 838 }