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         pointer_type,
  40
  41         instance,
  42         mir,
  43
  44         bcx,
  45         block_map,
  46         local_map: FxHashMap::with_capacity_and_hasher(mir.local_decls.len(), Default::default()),
  47         caller_location: None, // set by `codegen_fn_prelude`
  48         cold_blocks: EntitySet::new(),
  49
  50         clif_comments,
  51         constants_cx: &mut cx.constants_cx,
  52         vtables: &mut cx.vtables,
  53         source_info_set: indexmap::IndexSet::new(),
  54         next_ssa_var: 0,
  55     };
  56
  57     let arg_uninhabited = fx.mir.args_iter().any(|arg| fx.layout_of(fx.monomorphize(&fx.mir.local_decls[arg].ty)).abi.is_uninhabited());
  58
  59     if arg_uninhabited {
  60         fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
  61         fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
  62         crate::trap::trap_unreachable(&mut fx, "function has uninhabited argument");
  63     } else {
  64         tcx.sess.time("codegen clif ir", || {
  65             tcx.sess.time("codegen prelude", || crate::abi::codegen_fn_prelude(&mut fx, start_block));
  66             codegen_fn_content(&mut fx);
  67         });
  68     }
  69
  70     // Recover all necessary data from fx, before accessing func will prevent future access to it.
  71     let instance = fx.instance;
  72     let mut clif_comments = fx.clif_comments;
  73     let source_info_set = fx.source_info_set;
  74     let local_map = fx.local_map;
  75     let cold_blocks = fx.cold_blocks;
  76
  77     crate::pretty_clif::write_clif_file(
  78         cx.tcx,
  79         "unopt",
  80         None,
  81         instance,
  82         &context,
  83         &clif_comments,
  84     );
  85
  86     // Verify function
  87     verify_func(tcx, &clif_comments, &context.func);
  88
  89     // Perform rust specific optimizations
  90     tcx.sess.time("optimize clif ir", || {
  91         crate::optimize::optimize_function(tcx, instance, context, &cold_blocks, &mut clif_comments);
  92     });
  93
  94     // If the return block is not reachable, then the SSA builder may have inserted a `iconst.i128`
  95     // instruction, which doesn't have an encoding.
  96     context.compute_cfg();
  97     context.compute_domtree();
  98     context.eliminate_unreachable_code(cx.module.isa()).unwrap();
  99
 100     // Define function
 101     let module = &mut cx.module;
 102     tcx.sess.time(
 103         "define function",
 104         || module.define_function(
 105             func_id,
 106             context,
 107             &mut cranelift_codegen::binemit::NullTrapSink {},
 108         ).unwrap(),
 109     );
 110
 111     // Write optimized function to file for debugging
 112     crate::pretty_clif::write_clif_file(
 113         cx.tcx,
 114         "opt",
 115         Some(cx.module.isa()),
 116         instance,
 117         &context,
 118         &clif_comments,
 119     );
 120
 121     // Define debuginfo for function
 122     let isa = cx.module.isa();
 123     let debug_context = &mut cx.debug_context;
 124     let unwind_context = &mut cx.unwind_context;
 125     tcx.sess.time("generate debug info", || {
 126         if let Some(debug_context) = debug_context {
 127             debug_context.define_function(instance, func_id, &name, isa, context, &source_info_set, local_map);
 128         }
 129         unwind_context.add_function(func_id, &context, isa);
 130     });
 131
 132     // Clear context to make it usable for the next function
 133     context.clear();
 134 }
 135
 136 pub(crate) fn verify_func(tcx: TyCtxt<'_>, writer: &crate::pretty_clif::CommentWriter, func: &Function) {
 137     tcx.sess.time("verify clif ir", || {
 138         let flags = cranelift_codegen::settings::Flags::new(cranelift_codegen::settings::builder());
 139         match cranelift_codegen::verify_function(&func, &flags) {
 140             Ok(_) => {}
 141             Err(err) => {
 142                 tcx.sess.err(&format!("{:?}", err));
 143                 let pretty_error = cranelift_codegen::print_errors::pretty_verifier_error(
 144                     &func,
 145                     None,
 146                     Some(Box::new(writer)),
 147                     err,
 148                 );
 149                 tcx.sess
 150                     .fatal(&format!("cranelift verify error:\n{}", pretty_error));
 151             }
 152         }
 153     });
 154 }
 155
 156 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Backend>) {
 157     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 158         let block = fx.get_block(bb);
 159         fx.bcx.switch_to_block(block);
 160
 161         if bb_data.is_cleanup {
 162             // Unwinding after panicking is not supported
 163             continue;
 164
 165             // FIXME once unwinding is supported uncomment next lines
 166             // // Unwinding is unlikely to happen, so mark cleanup block's as cold.
 167             // fx.cold_blocks.insert(block);
 168         }
 169
 170         fx.bcx.ins().nop();
 171         for stmt in &bb_data.statements {
 172             fx.set_debug_loc(stmt.source_info);
 173             trans_stmt(fx, block, stmt);
 174         }
 175
 176         #[cfg(debug_assertions)]
 177         {
 178             let mut terminator_head = "\n".to_string();
 179             bb_data
 180                 .terminator()
 181                 .kind
 182                 .fmt_head(&mut terminator_head)
 183                 .unwrap();
 184             let inst = fx.bcx.func.layout.last_inst(block).unwrap();
 185             fx.add_comment(inst, terminator_head);
 186         }
 187
 188         fx.set_debug_loc(bb_data.terminator().source_info);
 189
 190         match &bb_data.terminator().kind {
 191             TerminatorKind::Goto { target } => {
 192                 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
 193                     let mut can_immediately_return = true;
 194                     for stmt in &fx.mir[*target].statements {
 195                         if let StatementKind::StorageDead(_) = stmt.kind {
 196                         } else {
 197                             // FIXME Can sometimes happen, see rust-lang/rust#70531
 198                             can_immediately_return = false;
 199                             break;
 200                         }
 201                     }
 202
 203                     if can_immediately_return {
 204                         crate::abi::codegen_return(fx);
 205                         continue;
 206                     }
 207                 }
 208
 209                 let block = fx.get_block(*target);
 210                 fx.bcx.ins().jump(block, &[]);
 211             }
 212             TerminatorKind::Return => {
 213                 crate::abi::codegen_return(fx);
 214             }
 215             TerminatorKind::Assert {
 216                 cond,
 217                 expected,
 218                 msg,
 219                 target,
 220                 cleanup: _,
 221             } => {
 222                 if !fx.tcx.sess.overflow_checks() {
 223                     if let mir::AssertKind::OverflowNeg(_) = *msg {
 224                         let target = fx.get_block(*target);
 225                         fx.bcx.ins().jump(target, &[]);
 226                         continue;
 227                     }
 228                 }
 229                 let cond = trans_operand(fx, cond).load_scalar(fx);
 230
 231                 let target = fx.get_block(*target);
 232                 let failure = fx.bcx.create_block();
 233                 fx.cold_blocks.insert(failure);
 234
 235                 if *expected {
 236                     fx.bcx.ins().brz(cond, failure, &[]);
 237                 } else {
 238                     fx.bcx.ins().brnz(cond, failure, &[]);
 239                 };
 240                 fx.bcx.ins().jump(target, &[]);
 241
 242                 fx.bcx.switch_to_block(failure);
 243
 244                 let location = fx.get_caller_location(bb_data.terminator().source_info.span).load_scalar(fx);
 245
 246                 let args;
 247                 let lang_item = match msg {
 248                     AssertKind::BoundsCheck { ref len, ref index } => {
 249                         let len = trans_operand(fx, len).load_scalar(fx);
 250                         let index = trans_operand(fx, index).load_scalar(fx);
 251                         args = [index, len, location];
 252                         rustc_hir::lang_items::PanicBoundsCheckFnLangItem
 253                     }
 254                     _ => {
 255                         let msg_str = msg.description();
 256                         let msg_ptr = fx.anonymous_str("assert", msg_str);
 257                         let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
 258                         args = [msg_ptr, msg_len, location];
 259                         rustc_hir::lang_items::PanicFnLangItem
 260                     }
 261                 };
 262
 263                 let def_id = fx.tcx.lang_items().require(lang_item).unwrap_or_else(|s| {
 264                     fx.tcx.sess.span_fatal(bb_data.terminator().source_info.span, &s)
 265                 });
 266
 267                 let instance = Instance::mono(fx.tcx, def_id);
 268                 let symbol_name = fx.tcx.symbol_name(instance).name.as_str();
 269
 270                 fx.lib_call(&*symbol_name, vec![fx.pointer_type, fx.pointer_type, fx.pointer_type], vec![], &args);
 271
 272                 crate::trap::trap_unreachable(fx, "panic lang item returned");
 273             }
 274
 275             TerminatorKind::SwitchInt {
 276                 discr,
 277                 switch_ty: _,
 278                 values,
 279                 targets,
 280             } => {
 281                 let discr = trans_operand(fx, discr).load_scalar(fx);
 282                 let mut switch = ::cranelift_frontend::Switch::new();
 283                 for (i, value) in values.iter().enumerate() {
 284                     let block = fx.get_block(targets[i]);
 285                     switch.set_entry(*value as u64, block);
 286                 }
 287                 let otherwise_block = fx.get_block(targets[targets.len() - 1]);
 288                 switch.emit(&mut fx.bcx, discr, otherwise_block);
 289             }
 290             TerminatorKind::Call {
 291                 func,
 292                 args,
 293                 destination,
 294                 fn_span,
 295                 cleanup: _,
 296                 from_hir_call: _,
 297             } => {
 298                 fx.tcx.sess.time("codegen call", || crate::abi::codegen_terminator_call(
 299                     fx,
 300                     *fn_span,
 301                     block,
 302                     func,
 303                     args,
 304                     *destination,
 305                 ));
 306             }
 307             TerminatorKind::InlineAsm {
 308                 template,
 309                 operands,
 310                 options: _,
 311                 destination,
 312                 line_spans: _,
 313             } => {
 314                 match template {
 315                     &[] => {
 316                         assert_eq!(operands, &[]);
 317                         match *destination {
 318                             Some(destination) => {
 319                                 let destination_block = fx.get_block(destination);
 320                                 fx.bcx.ins().jump(destination_block, &[]);
 321                             }
 322                             None => bug!(),
 323                         }
 324
 325                         // Black box
 326                     }
 327                     _ => fx.tcx.sess.span_fatal(bb_data.terminator().source_info.span, "Inline assembly is not supported"),
 328                 }
 329             }
 330             TerminatorKind::Resume | TerminatorKind::Abort => {
 331                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 332             }
 333             TerminatorKind::Unreachable => {
 334                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 335             }
 336             TerminatorKind::Yield { .. }
 337             | TerminatorKind::FalseEdge { .. }
 338             | TerminatorKind::FalseUnwind { .. }
 339             | TerminatorKind::DropAndReplace { .. }
 340             | TerminatorKind::GeneratorDrop => {
 341                 bug!("shouldn't exist at trans {:?}", bb_data.terminator());
 342             }
 343             TerminatorKind::Drop {
 344                 place,
 345                 target,
 346                 unwind: _,
 347             } => {
 348                 let drop_place = trans_place(fx, *place);
 349                 crate::abi::codegen_drop(fx, bb_data.terminator().source_info.span, drop_place);
 350
 351                 let target_block = fx.get_block(*target);
 352                 fx.bcx.ins().jump(target_block, &[]);
 353             }
 354         };
 355     }
 356
 357     fx.bcx.seal_all_blocks();
 358     fx.bcx.finalize();
 359 }
 360
 361 fn trans_stmt<'tcx>(
 362     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 363     #[allow(unused_variables)]
 364     cur_block: Block,
 365     stmt: &Statement<'tcx>,
 366 ) {
 367     let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
 368
 369     fx.set_debug_loc(stmt.source_info);
 370
 371     #[cfg(false_debug_assertions)]
 372     match &stmt.kind {
 373         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 374         _ => {
 375             let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
 376             fx.add_comment(inst, format!("{:?}", stmt));
 377         }
 378     }
 379
 380     match &stmt.kind {
 381         StatementKind::SetDiscriminant {
 382             place,
 383             variant_index,
 384         } => {
 385             let place = trans_place(fx, **place);
 386             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 387         }
 388         StatementKind::Assign(to_place_and_rval) => {
 389             let lval = trans_place(fx, to_place_and_rval.0);
 390             let dest_layout = lval.layout();
 391             match &to_place_and_rval.1 {
 392                 Rvalue::Use(operand) => {
 393                     let val = trans_operand(fx, operand);
 394                     lval.write_cvalue(fx, val);
 395                 }
 396                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
 397                     let place = trans_place(fx, *place);
 398                     place.write_place_ref(fx, lval);
 399                 }
 400                 Rvalue::ThreadLocalRef(def_id) => {
 401                     let val = crate::constant::codegen_tls_ref(fx, *def_id, lval.layout());
 402                     lval.write_cvalue(fx, val);
 403                 }
 404                 Rvalue::BinaryOp(bin_op, lhs, rhs) => {
 405                     let lhs = trans_operand(fx, lhs);
 406                     let rhs = trans_operand(fx, rhs);
 407
 408                     let res = crate::num::codegen_binop(fx, *bin_op, lhs, rhs);
 409                     lval.write_cvalue(fx, res);
 410                 }
 411                 Rvalue::CheckedBinaryOp(bin_op, lhs, rhs) => {
 412                     let lhs = trans_operand(fx, lhs);
 413                     let rhs = trans_operand(fx, rhs);
 414
 415                     let res = if !fx.tcx.sess.overflow_checks() {
 416                         let val =
 417                             crate::num::trans_int_binop(fx, *bin_op, lhs, rhs).load_scalar(fx);
 418                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 419                         CValue::by_val_pair(val, is_overflow, lval.layout())
 420                     } else {
 421                         crate::num::trans_checked_int_binop(fx, *bin_op, lhs, rhs)
 422                     };
 423
 424                     lval.write_cvalue(fx, res);
 425                 }
 426                 Rvalue::UnaryOp(un_op, operand) => {
 427                     let operand = trans_operand(fx, operand);
 428                     let layout = operand.layout();
 429                     let val = operand.load_scalar(fx);
 430                     let res = match un_op {
 431                         UnOp::Not => {
 432                             match layout.ty.kind {
 433                                 ty::Bool => {
 434                                     let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 435                                     CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 436                                 }
 437                                 ty::Uint(_) | ty::Int(_) => {
 438                                     CValue::by_val(fx.bcx.ins().bnot(val), layout)
 439                                 }
 440                                 _ => unreachable!("un op Not for {:?}", layout.ty),
 441                             }
 442                         }
 443                         UnOp::Neg => match layout.ty.kind {
 444                             ty::Int(IntTy::I128) => {
 445                                 // FIXME remove this case once ineg.i128 works
 446                                 let zero = CValue::const_val(fx, layout, 0);
 447                                 crate::num::trans_int_binop(fx, BinOp::Sub, zero, operand)
 448                             }
 449                             ty::Int(_) => {
 450                                 CValue::by_val(fx.bcx.ins().ineg(val), layout)
 451                             }
 452                             ty::Float(_) => {
 453                                 CValue::by_val(fx.bcx.ins().fneg(val), layout)
 454                             }
 455                             _ => unreachable!("un op Neg for {:?}", layout.ty),
 456                         },
 457                     };
 458                     lval.write_cvalue(fx, res);
 459                 }
 460                 Rvalue::Cast(CastKind::Pointer(PointerCast::ReifyFnPointer), operand, to_ty) => {
 461                     let from_ty = fx.monomorphize(&operand.ty(&fx.mir.local_decls, fx.tcx));
 462                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 463                     match from_ty.kind {
 464                         ty::FnDef(def_id, substs) => {
 465                             let func_ref = fx.get_function_ref(
 466                                 Instance::resolve_for_fn_ptr(fx.tcx, ParamEnv::reveal_all(), def_id, substs)
 467                                     .unwrap(),
 468                             );
 469                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 470                             lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
 471                         }
 472                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
 473                     }
 474                 }
 475                 Rvalue::Cast(CastKind::Pointer(PointerCast::UnsafeFnPointer), operand, to_ty)
 476                 | Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer), operand, to_ty)
 477                 | Rvalue::Cast(CastKind::Pointer(PointerCast::ArrayToPointer), operand, to_ty) => {
 478                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 479                     let operand = trans_operand(fx, operand);
 480                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
 481                 }
 482                 Rvalue::Cast(CastKind::Misc, operand, to_ty) => {
 483                     let operand = trans_operand(fx, operand);
 484                     let from_ty = operand.layout().ty;
 485                     let to_ty = fx.monomorphize(to_ty);
 486
 487                     fn is_fat_ptr<'tcx>(
 488                         fx: &FunctionCx<'_, 'tcx, impl Backend>,
 489                         ty: Ty<'tcx>,
 490                     ) -> bool {
 491                         ty.builtin_deref(true)
 492                             .map(
 493                                 |ty::TypeAndMut {
 494                                      ty: pointee_ty,
 495                                      mutbl: _,
 496                                  }| has_ptr_meta(fx.tcx, pointee_ty),
 497                             )
 498                             .unwrap_or(false)
 499                     }
 500
 501                     if is_fat_ptr(fx, from_ty) {
 502                         if is_fat_ptr(fx, to_ty) {
 503                             // fat-ptr -> fat-ptr
 504                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
 505                         } else {
 506                             // fat-ptr -> thin-ptr
 507                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 508                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 509                         }
 510                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind {
 511                         // enum -> discriminant value
 512                         assert!(adt_def.is_enum());
 513                         match to_ty.kind {
 514                             ty::Uint(_) | ty::Int(_) => {}
 515                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 516                         }
 517
 518                         use rustc_target::abi::{TagEncoding, Int, Variants};
 519
 520                         match &operand.layout().variants {
 521                             Variants::Single { index } => {
 522                                 let discr = operand.layout().ty.discriminant_for_variant(fx.tcx, *index).unwrap();
 523                                 let discr = if discr.ty.is_signed() {
 524                                     rustc_middle::mir::interpret::sign_extend(discr.val, fx.layout_of(discr.ty).size)
 525                                 } else {
 526                                     discr.val
 527                                 };
 528
 529                                 let discr = CValue::const_val(fx, fx.layout_of(to_ty), discr);
 530                                 lval.write_cvalue(fx, discr);
 531                             }
 532                             Variants::Multiple {
 533                                 tag,
 534                                 tag_field,
 535                                 tag_encoding: TagEncoding::Direct,
 536                                 variants: _,
 537                             } => {
 538                                 let cast_to = fx.clif_type(dest_layout.ty).unwrap();
 539
 540                                 // Read the tag/niche-encoded discriminant from memory.
 541                                 let encoded_discr = operand.value_field(fx, mir::Field::new(*tag_field));
 542                                 let encoded_discr = encoded_discr.load_scalar(fx);
 543
 544                                 // Decode the discriminant (specifically if it's niche-encoded).
 545                                 let signed = match tag.value {
 546                                     Int(_, signed) => signed,
 547                                     _ => false,
 548                                 };
 549                                 let val = clif_intcast(fx, encoded_discr, cast_to, signed);
 550                                 let val = CValue::by_val(val, dest_layout);
 551                                 lval.write_cvalue(fx, val);
 552                             }
 553                             Variants::Multiple { ..} => unreachable!(),
 554                         }
 555                     } else {
 556                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 557                         let from = operand.load_scalar(fx);
 558
 559                         let res = clif_int_or_float_cast(
 560                             fx,
 561                             from,
 562                             type_sign(from_ty),
 563                             to_clif_ty,
 564                             type_sign(to_ty),
 565                         );
 566                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 567                     }
 568                 }
 569                 Rvalue::Cast(CastKind::Pointer(PointerCast::ClosureFnPointer(_)), operand, _to_ty) => {
 570                     let operand = trans_operand(fx, operand);
 571                     match operand.layout().ty.kind {
 572                         ty::Closure(def_id, substs) => {
 573                             let instance = Instance::resolve_closure(
 574                                 fx.tcx,
 575                                 def_id,
 576                                 substs,
 577                                 ty::ClosureKind::FnOnce,
 578                             );
 579                             let func_ref = fx.get_function_ref(instance);
 580                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 581                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 582                         }
 583                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 584                     }
 585                 }
 586                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), operand, _to_ty) => {
 587                     let operand = trans_operand(fx, operand);
 588                     operand.unsize_value(fx, lval);
 589                 }
 590                 Rvalue::Discriminant(place) => {
 591                     let place = trans_place(fx, *place);
 592                     let value = place.to_cvalue(fx);
 593                     let discr =
 594                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 595                     lval.write_cvalue(fx, discr);
 596                 }
 597                 Rvalue::Repeat(operand, times) => {
 598                     let operand = trans_operand(fx, operand);
 599                     let times = fx
 600                         .monomorphize(times)
 601                         .eval(fx.tcx, ParamEnv::reveal_all())
 602                         .val
 603                         .try_to_bits(fx.tcx.data_layout.pointer_size)
 604                         .unwrap();
 605                     for i in 0..times {
 606                         let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 607                         let to = lval.place_index(fx, index);
 608                         to.write_cvalue(fx, operand);
 609                     }
 610                 }
 611                 Rvalue::Len(place) => {
 612                     let place = trans_place(fx, *place);
 613                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 614                     let len = codegen_array_len(fx, place);
 615                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 616                 }
 617                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 618                     use rustc_hir::lang_items::ExchangeMallocFnLangItem;
 619
 620                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 621                     let content_ty = fx.monomorphize(content_ty);
 622                     let layout = fx.layout_of(content_ty);
 623                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 624                     let llalign = fx
 625                         .bcx
 626                         .ins()
 627                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 628                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 629
 630                     // Allocate space:
 631                     let def_id = match fx.tcx.lang_items().require(ExchangeMallocFnLangItem) {
 632                         Ok(id) => id,
 633                         Err(s) => {
 634                             fx.tcx
 635                                 .sess
 636                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 637                         }
 638                     };
 639                     let instance = ty::Instance::mono(fx.tcx, def_id);
 640                     let func_ref = fx.get_function_ref(instance);
 641                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 642                     let ptr = fx.bcx.inst_results(call)[0];
 643                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 644                 }
 645                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 646                     assert!(lval
 647                         .layout()
 648                         .ty
 649                         .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all()));
 650                     let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
 651                     let val = CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
 652                     lval.write_cvalue(fx, val);
 653                 }
 654                 Rvalue::Aggregate(kind, operands) => match **kind {
 655                     AggregateKind::Array(_ty) => {
 656                         for (i, operand) in operands.into_iter().enumerate() {
 657                             let operand = trans_operand(fx, operand);
 658                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 659                             let to = lval.place_index(fx, index);
 660                             to.write_cvalue(fx, operand);
 661                         }
 662                     }
 663                     _ => unreachable!("shouldn't exist at trans {:?}", to_place_and_rval.1),
 664                 },
 665             }
 666         }
 667         StatementKind::StorageLive(_)
 668         | StatementKind::StorageDead(_)
 669         | StatementKind::Nop
 670         | StatementKind::FakeRead(..)
 671         | StatementKind::Retag { .. }
 672         | StatementKind::AscribeUserType(..) => {}
 673
 674         StatementKind::LlvmInlineAsm(asm) => {
 675             use rustc_span::symbol::Symbol;
 676             let LlvmInlineAsm {
 677                 asm,
 678                 outputs: _,
 679                 inputs: _,
 680             } = &**asm;
 681             let rustc_hir::LlvmInlineAsmInner {
 682                 asm: asm_code, // Name
 683                 outputs,       // Vec<Name>
 684                 inputs,        // Vec<Name>
 685                 clobbers,      // Vec<Name>
 686                 volatile,      // bool
 687                 alignstack,    // bool
 688                 dialect: _,    // rustc_ast::ast::AsmDialect
 689                 asm_str_style: _,
 690             } = asm;
 691             match &*asm_code.as_str() {
 692                 cpuid if cpuid.contains("cpuid") => {
 693                     crate::trap::trap_unimplemented(
 694                         fx,
 695                         "__cpuid_count arch intrinsic is not supported",
 696                     );
 697                 }
 698                 "xgetbv" => {
 699                     assert_eq!(inputs, &[Symbol::intern("{ecx}")]);
 700
 701                     assert_eq!(outputs.len(), 2);
 702                     for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
 703                         assert_eq!(&outputs[i].constraint.as_str(), c);
 704                         assert!(!outputs[i].is_rw);
 705                         assert!(!outputs[i].is_indirect);
 706                     }
 707
 708                     assert_eq!(clobbers, &[]);
 709
 710                     assert!(!volatile);
 711                     assert!(!alignstack);
 712
 713                     crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
 714                 }
 715                 // ___chkstk, ___chkstk_ms and __alloca are only used on Windows
 716                 _ if fx.tcx.symbol_name(fx.instance).name.as_str().starts_with("___chkstk") => {
 717                     crate::trap::trap_unimplemented(fx, "Stack probes are not supported");
 718                 }
 719                 _ if fx.tcx.symbol_name(fx.instance).name.as_str() == "__alloca" => {
 720                     crate::trap::trap_unimplemented(fx, "Alloca is not supported");
 721                 }
 722                 // Used in sys::windows::abort_internal
 723                 "int $$0x29" => {
 724                     crate::trap::trap_unimplemented(fx, "Windows abort");
 725                 }
 726                 _ => fx.tcx.sess.span_fatal(stmt.source_info.span, "Inline assembly is not supported"),
 727             }
 728         }
 729     }
 730 }
 731
 732 fn codegen_array_len<'tcx>(
 733     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 734     place: CPlace<'tcx>,
 735 ) -> Value {
 736     match place.layout().ty.kind {
 737         ty::Array(_elem_ty, len) => {
 738             let len = fx.monomorphize(&len)
 739                 .eval(fx.tcx, ParamEnv::reveal_all())
 740                 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 741             fx.bcx.ins().iconst(fx.pointer_type, len)
 742         }
 743         ty::Slice(_elem_ty) => place
 744             .to_ptr_maybe_unsized()
 745             .1
 746             .expect("Length metadata for slice place"),
 747         _ => bug!("Rvalue::Len({:?})", place),
 748     }
 749 }
 750
 751 pub(crate) fn trans_place<'tcx>(
 752     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 753     place: Place<'tcx>,
 754 ) -> CPlace<'tcx> {
 755     let mut cplace = fx.get_local_place(place.local);
 756
 757     for elem in place.projection {
 758         match elem {
 759             PlaceElem::Deref => {
 760                 cplace = cplace.place_deref(fx);
 761             }
 762             PlaceElem::Field(field, _ty) => {
 763                 cplace = cplace.place_field(fx, field);
 764             }
 765             PlaceElem::Index(local) => {
 766                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 767                 cplace = cplace.place_index(fx, index);
 768             }
 769             PlaceElem::ConstantIndex {
 770                 offset,
 771                 min_length: _,
 772                 from_end,
 773             } => {
 774                 let index = if !from_end {
 775                     fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 776                 } else {
 777                     let len = codegen_array_len(fx, cplace);
 778                     fx.bcx.ins().iadd_imm(len, -(offset as i64))
 779                 };
 780                 cplace = cplace.place_index(fx, index);
 781             }
 782             PlaceElem::Subslice { from, to, from_end } => {
 783                 // These indices are generated by slice patterns.
 784                 // slice[from:-to] in Python terms.
 785
 786                 match cplace.layout().ty.kind {
 787                     ty::Array(elem_ty, _len) => {
 788                         assert!(!from_end, "array subslices are never `from_end`");
 789                         let elem_layout = fx.layout_of(elem_ty);
 790                         let ptr = cplace.to_ptr();
 791                         cplace = CPlace::for_ptr(
 792                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * from as i64),
 793                             fx.layout_of(fx.tcx.mk_array(elem_ty, to as u64 - from as u64)),
 794                         );
 795                     }
 796                     ty::Slice(elem_ty) => {
 797                         assert!(from_end, "slice subslices should be `from_end`");
 798                         let elem_layout = fx.layout_of(elem_ty);
 799                         let (ptr, len) = cplace.to_ptr_maybe_unsized();
 800                         let len = len.unwrap();
 801                         cplace = CPlace::for_ptr_with_extra(
 802                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * from as i64),
 803                             fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
 804                             cplace.layout(),
 805                         );
 806                     }
 807                     _ => unreachable!(),
 808                 }
 809             }
 810             PlaceElem::Downcast(_adt_def, variant) => {
 811                 cplace = cplace.downcast_variant(fx, variant);
 812             }
 813         }
 814     }
 815
 816     cplace
 817 }
 818
 819 pub(crate) fn trans_operand<'tcx>(
 820     fx: &mut FunctionCx<'_, 'tcx, impl Backend>,
 821     operand: &Operand<'tcx>,
 822 ) -> CValue<'tcx> {
 823     match operand {
 824         Operand::Move(place) | Operand::Copy(place) => {
 825             let cplace = trans_place(fx, *place);
 826             cplace.to_cvalue(fx)
 827         }
 828         Operand::Constant(const_) => crate::constant::trans_constant(fx, const_),
 829     }
 830 }