compiler/rustc_codegen_cranelift/src/base.rs

   1 //! Codegen of a single function
   2
   3 use rustc_index::vec::IndexVec;
   4 use rustc_middle::ty::adjustment::PointerCast;
   5 use rustc_middle::ty::layout::FnAbiExt;
   6 use rustc_target::abi::call::FnAbi;
   7
   8 use crate::prelude::*;
   9
  10 pub(crate) fn codegen_fn<'tcx>(
  11     cx: &mut crate::CodegenCx<'tcx, impl Module>,
  12     instance: Instance<'tcx>,
  13     linkage: Linkage,
  14 ) {
  15     let tcx = cx.tcx;
  16
  17     let _inst_guard =
  18         crate::PrintOnPanic(|| format!("{:?} {}", instance, tcx.symbol_name(instance).name));
  19     debug_assert!(!instance.substs.needs_infer());
  20
  21     let mir = tcx.instance_mir(instance.def);
  22
  23     // Declare function
  24     let name = tcx.symbol_name(instance).name.to_string();
  25     let sig = get_function_sig(tcx, cx.module.isa().triple(), instance);
  26     let func_id = cx.module.declare_function(&name, linkage, &sig).unwrap();
  27
  28     cx.cached_context.clear();
  29
  30     // Make the FunctionBuilder
  31     let mut func_ctx = FunctionBuilderContext::new();
  32     let mut func = std::mem::replace(&mut cx.cached_context.func, Function::new());
  33     func.name = ExternalName::user(0, func_id.as_u32());
  34     func.signature = sig;
  35     func.collect_debug_info();
  36
  37     let mut bcx = FunctionBuilder::new(&mut func, &mut func_ctx);
  38
  39     // Predefine blocks
  40     let start_block = bcx.create_block();
  41     let block_map: IndexVec<BasicBlock, Block> = (0..mir.basic_blocks().len())
  42         .map(|_| bcx.create_block())
  43         .collect();
  44
  45     // Make FunctionCx
  46     let pointer_type = cx.module.target_config().pointer_type();
  47     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  48
  49     let mut fx = FunctionCx {
  50         cx,
  51         tcx,
  52         pointer_type,
  53
  54         instance,
  55         mir,
  56         fn_abi: Some(FnAbi::of_instance(&RevealAllLayoutCx(tcx), instance, &[])),
  57
  58         bcx,
  59         block_map,
  60         local_map: IndexVec::with_capacity(mir.local_decls.len()),
  61         caller_location: None, // set by `codegen_fn_prelude`
  62         cold_blocks: EntitySet::new(),
  63
  64         clif_comments,
  65         source_info_set: indexmap::IndexSet::new(),
  66         next_ssa_var: 0,
  67
  68         inline_asm_index: 0,
  69     };
  70
  71     let arg_uninhabited = fx.mir.args_iter().any(|arg| {
  72         fx.layout_of(fx.monomorphize(&fx.mir.local_decls[arg].ty))
  73             .abi
  74             .is_uninhabited()
  75     });
  76
  77     if arg_uninhabited {
  78         fx.bcx
  79             .append_block_params_for_function_params(fx.block_map[START_BLOCK]);
  80         fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
  81         crate::trap::trap_unreachable(&mut fx, "function has uninhabited argument");
  82     } else {
  83         tcx.sess.time("codegen clif ir", || {
  84             tcx.sess.time("codegen prelude", || {
  85                 crate::abi::codegen_fn_prelude(&mut fx, start_block)
  86             });
  87             codegen_fn_content(&mut fx);
  88         });
  89     }
  90
  91     // Recover all necessary data from fx, before accessing func will prevent future access to it.
  92     let instance = fx.instance;
  93     let mut clif_comments = fx.clif_comments;
  94     let source_info_set = fx.source_info_set;
  95     let local_map = fx.local_map;
  96     let cold_blocks = fx.cold_blocks;
  97
  98     // Store function in context
  99     let context = &mut cx.cached_context;
 100     context.func = func;
 101
 102     crate::pretty_clif::write_clif_file(tcx, "unopt", None, instance, &context, &clif_comments);
 103
 104     // Verify function
 105     verify_func(tcx, &clif_comments, &context.func);
 106
 107     // Perform rust specific optimizations
 108     tcx.sess.time("optimize clif ir", || {
 109         crate::optimize::optimize_function(
 110             tcx,
 111             instance,
 112             context,
 113             &cold_blocks,
 114             &mut clif_comments,
 115         );
 116     });
 117
 118     // If the return block is not reachable, then the SSA builder may have inserted an `iconst.i128`
 119     // instruction, which doesn't have an encoding.
 120     context.compute_cfg();
 121     context.compute_domtree();
 122     context.eliminate_unreachable_code(cx.module.isa()).unwrap();
 123     context.dce(cx.module.isa()).unwrap();
 124     // Some Cranelift optimizations expect the domtree to not yet be computed and as such don't
 125     // invalidate it when it would change.
 126     context.domtree.clear();
 127
 128     context.want_disasm = crate::pretty_clif::should_write_ir(tcx);
 129
 130     // Define function
 131     let module = &mut cx.module;
 132     tcx.sess.time("define function", || {
 133         module
 134             .define_function(
 135                 func_id,
 136                 context,
 137                 &mut cranelift_codegen::binemit::NullTrapSink {},
 138             )
 139             .unwrap()
 140     });
 141
 142     // Write optimized function to file for debugging
 143     crate::pretty_clif::write_clif_file(
 144         tcx,
 145         "opt",
 146         Some(cx.module.isa()),
 147         instance,
 148         &context,
 149         &clif_comments,
 150     );
 151
 152     if let Some(mach_compile_result) = &context.mach_compile_result {
 153         if let Some(disasm) = &mach_compile_result.disasm {
 154             crate::pretty_clif::write_ir_file(
 155                 tcx,
 156                 &format!("{}.vcode", tcx.symbol_name(instance).name),
 157                 |file| file.write_all(disasm.as_bytes()),
 158             )
 159         }
 160     }
 161
 162     // Define debuginfo for function
 163     let isa = cx.module.isa();
 164     let debug_context = &mut cx.debug_context;
 165     let unwind_context = &mut cx.unwind_context;
 166     tcx.sess.time("generate debug info", || {
 167         if let Some(debug_context) = debug_context {
 168             debug_context.define_function(
 169                 instance,
 170                 func_id,
 171                 &name,
 172                 isa,
 173                 context,
 174                 &source_info_set,
 175                 local_map,
 176             );
 177         }
 178         unwind_context.add_function(func_id, &context, isa);
 179     });
 180
 181     // Clear context to make it usable for the next function
 182     context.clear();
 183 }
 184
 185 pub(crate) fn verify_func(
 186     tcx: TyCtxt<'_>,
 187     writer: &crate::pretty_clif::CommentWriter,
 188     func: &Function,
 189 ) {
 190     tcx.sess.time("verify clif ir", || {
 191         let flags = cranelift_codegen::settings::Flags::new(cranelift_codegen::settings::builder());
 192         match cranelift_codegen::verify_function(&func, &flags) {
 193             Ok(_) => {}
 194             Err(err) => {
 195                 tcx.sess.err(&format!("{:?}", err));
 196                 let pretty_error = cranelift_codegen::print_errors::pretty_verifier_error(
 197                     &func,
 198                     None,
 199                     Some(Box::new(writer)),
 200                     err,
 201                 );
 202                 tcx.sess
 203                     .fatal(&format!("cranelift verify error:\n{}", pretty_error));
 204             }
 205         }
 206     });
 207 }
 208
 209 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, impl Module>) {
 210     crate::constant::check_constants(fx);
 211
 212     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 213         let block = fx.get_block(bb);
 214         fx.bcx.switch_to_block(block);
 215
 216         if bb_data.is_cleanup {
 217             // Unwinding after panicking is not supported
 218             continue;
 219
 220             // FIXME once unwinding is supported uncomment next lines
 221             // // Unwinding is unlikely to happen, so mark cleanup block's as cold.
 222             // fx.cold_blocks.insert(block);
 223         }
 224
 225         fx.bcx.ins().nop();
 226         for stmt in &bb_data.statements {
 227             fx.set_debug_loc(stmt.source_info);
 228             codegen_stmt(fx, block, stmt);
 229         }
 230
 231         #[cfg(debug_assertions)]
 232         {
 233             let mut terminator_head = "\n".to_string();
 234             bb_data
 235                 .terminator()
 236                 .kind
 237                 .fmt_head(&mut terminator_head)
 238                 .unwrap();
 239             let inst = fx.bcx.func.layout.last_inst(block).unwrap();
 240             fx.add_comment(inst, terminator_head);
 241         }
 242
 243         fx.set_debug_loc(bb_data.terminator().source_info);
 244
 245         match &bb_data.terminator().kind {
 246             TerminatorKind::Goto { target } => {
 247                 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
 248                     let mut can_immediately_return = true;
 249                     for stmt in &fx.mir[*target].statements {
 250                         if let StatementKind::StorageDead(_) = stmt.kind {
 251                         } else {
 252                             // FIXME Can sometimes happen, see rust-lang/rust#70531
 253                             can_immediately_return = false;
 254                             break;
 255                         }
 256                     }
 257
 258                     if can_immediately_return {
 259                         crate::abi::codegen_return(fx);
 260                         continue;
 261                     }
 262                 }
 263
 264                 let block = fx.get_block(*target);
 265                 fx.bcx.ins().jump(block, &[]);
 266             }
 267             TerminatorKind::Return => {
 268                 crate::abi::codegen_return(fx);
 269             }
 270             TerminatorKind::Assert {
 271                 cond,
 272                 expected,
 273                 msg,
 274                 target,
 275                 cleanup: _,
 276             } => {
 277                 if !fx.tcx.sess.overflow_checks() {
 278                     if let mir::AssertKind::OverflowNeg(_) = *msg {
 279                         let target = fx.get_block(*target);
 280                         fx.bcx.ins().jump(target, &[]);
 281                         continue;
 282                     }
 283                 }
 284                 let cond = codegen_operand(fx, cond).load_scalar(fx);
 285
 286                 let target = fx.get_block(*target);
 287                 let failure = fx.bcx.create_block();
 288                 fx.cold_blocks.insert(failure);
 289
 290                 if *expected {
 291                     fx.bcx.ins().brz(cond, failure, &[]);
 292                 } else {
 293                     fx.bcx.ins().brnz(cond, failure, &[]);
 294                 };
 295                 fx.bcx.ins().jump(target, &[]);
 296
 297                 fx.bcx.switch_to_block(failure);
 298                 fx.bcx.ins().nop();
 299
 300                 match msg {
 301                     AssertKind::BoundsCheck { ref len, ref index } => {
 302                         let len = codegen_operand(fx, len).load_scalar(fx);
 303                         let index = codegen_operand(fx, index).load_scalar(fx);
 304                         let location = fx
 305                             .get_caller_location(bb_data.terminator().source_info.span)
 306                             .load_scalar(fx);
 307
 308                         codegen_panic_inner(
 309                             fx,
 310                             rustc_hir::LangItem::PanicBoundsCheck,
 311                             &[index, len, location],
 312                             bb_data.terminator().source_info.span,
 313                         );
 314                     }
 315                     _ => {
 316                         let msg_str = msg.description();
 317                         codegen_panic(fx, msg_str, bb_data.terminator().source_info.span);
 318                     }
 319                 }
 320             }
 321
 322             TerminatorKind::SwitchInt {
 323                 discr,
 324                 switch_ty,
 325                 targets,
 326             } => {
 327                 let discr = codegen_operand(fx, discr).load_scalar(fx);
 328
 329                 let use_bool_opt = switch_ty.kind() == fx.tcx.types.bool.kind()
 330                     || (targets.iter().count() == 1 && targets.iter().next().unwrap().0 == 0);
 331                 if use_bool_opt {
 332                     assert_eq!(targets.iter().count(), 1);
 333                     let (then_value, then_block) = targets.iter().next().unwrap();
 334                     let then_block = fx.get_block(then_block);
 335                     let else_block = fx.get_block(targets.otherwise());
 336                     let test_zero = match then_value {
 337                         0 => true,
 338                         1 => false,
 339                         _ => unreachable!("{:?}", targets),
 340                     };
 341
 342                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 343                     let (discr, is_inverted) =
 344                         crate::optimize::peephole::maybe_unwrap_bool_not(&mut fx.bcx, discr);
 345                     let test_zero = if is_inverted { !test_zero } else { test_zero };
 346                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 347                     let discr =
 348                         crate::optimize::peephole::make_branchable_value(&mut fx.bcx, discr);
 349                     if let Some(taken) = crate::optimize::peephole::maybe_known_branch_taken(
 350                         &fx.bcx, discr, test_zero,
 351                     ) {
 352                         if taken {
 353                             fx.bcx.ins().jump(then_block, &[]);
 354                         } else {
 355                             fx.bcx.ins().jump(else_block, &[]);
 356                         }
 357                     } else {
 358                         if test_zero {
 359                             fx.bcx.ins().brz(discr, then_block, &[]);
 360                             fx.bcx.ins().jump(else_block, &[]);
 361                         } else {
 362                             fx.bcx.ins().brnz(discr, then_block, &[]);
 363                             fx.bcx.ins().jump(else_block, &[]);
 364                         }
 365                     }
 366                 } else {
 367                     let mut switch = ::cranelift_frontend::Switch::new();
 368                     for (value, block) in targets.iter() {
 369                         let block = fx.get_block(block);
 370                         switch.set_entry(value, block);
 371                     }
 372                     let otherwise_block = fx.get_block(targets.otherwise());
 373                     switch.emit(&mut fx.bcx, discr, otherwise_block);
 374                 }
 375             }
 376             TerminatorKind::Call {
 377                 func,
 378                 args,
 379                 destination,
 380                 fn_span,
 381                 cleanup: _,
 382                 from_hir_call: _,
 383             } => {
 384                 fx.tcx.sess.time("codegen call", || {
 385                     crate::abi::codegen_terminator_call(
 386                         fx,
 387                         *fn_span,
 388                         block,
 389                         func,
 390                         args,
 391                         *destination,
 392                     )
 393                 });
 394             }
 395             TerminatorKind::InlineAsm {
 396                 template,
 397                 operands,
 398                 options,
 399                 destination,
 400                 line_spans: _,
 401             } => {
 402                 crate::inline_asm::codegen_inline_asm(
 403                     fx,
 404                     bb_data.terminator().source_info.span,
 405                     template,
 406                     operands,
 407                     *options,
 408                 );
 409
 410                 match *destination {
 411                     Some(destination) => {
 412                         let destination_block = fx.get_block(destination);
 413                         fx.bcx.ins().jump(destination_block, &[]);
 414                     }
 415                     None => {
 416                         crate::trap::trap_unreachable(
 417                             fx,
 418                             "[corruption] Returned from noreturn inline asm",
 419                         );
 420                     }
 421                 }
 422             }
 423             TerminatorKind::Resume | TerminatorKind::Abort => {
 424                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 425             }
 426             TerminatorKind::Unreachable => {
 427                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 428             }
 429             TerminatorKind::Yield { .. }
 430             | TerminatorKind::FalseEdge { .. }
 431             | TerminatorKind::FalseUnwind { .. }
 432             | TerminatorKind::DropAndReplace { .. }
 433             | TerminatorKind::GeneratorDrop => {
 434                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
 435             }
 436             TerminatorKind::Drop {
 437                 place,
 438                 target,
 439                 unwind: _,
 440             } => {
 441                 let drop_place = codegen_place(fx, *place);
 442                 crate::abi::codegen_drop(fx, bb_data.terminator().source_info.span, drop_place);
 443
 444                 let target_block = fx.get_block(*target);
 445                 fx.bcx.ins().jump(target_block, &[]);
 446             }
 447         };
 448     }
 449
 450     fx.bcx.seal_all_blocks();
 451     fx.bcx.finalize();
 452 }
 453
 454 fn codegen_stmt<'tcx>(
 455     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
 456     #[allow(unused_variables)] cur_block: Block,
 457     stmt: &Statement<'tcx>,
 458 ) {
 459     let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
 460
 461     fx.set_debug_loc(stmt.source_info);
 462
 463     #[cfg(false_debug_assertions)]
 464     match &stmt.kind {
 465         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 466         _ => {
 467             let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
 468             fx.add_comment(inst, format!("{:?}", stmt));
 469         }
 470     }
 471
 472     match &stmt.kind {
 473         StatementKind::SetDiscriminant {
 474             place,
 475             variant_index,
 476         } => {
 477             let place = codegen_place(fx, **place);
 478             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 479         }
 480         StatementKind::Assign(to_place_and_rval) => {
 481             let lval = codegen_place(fx, to_place_and_rval.0);
 482             let dest_layout = lval.layout();
 483             match to_place_and_rval.1 {
 484                 Rvalue::Use(ref operand) => {
 485                     let val = codegen_operand(fx, operand);
 486                     lval.write_cvalue(fx, val);
 487                 }
 488                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
 489                     let place = codegen_place(fx, place);
 490                     let ref_ = place.place_ref(fx, lval.layout());
 491                     lval.write_cvalue(fx, ref_);
 492                 }
 493                 Rvalue::ThreadLocalRef(def_id) => {
 494                     let val = crate::constant::codegen_tls_ref(fx, def_id, lval.layout());
 495                     lval.write_cvalue(fx, val);
 496                 }
 497                 Rvalue::BinaryOp(bin_op, box (ref lhs, ref rhs)) => {
 498                     let lhs = codegen_operand(fx, lhs);
 499                     let rhs = codegen_operand(fx, rhs);
 500
 501                     let res = crate::num::codegen_binop(fx, bin_op, lhs, rhs);
 502                     lval.write_cvalue(fx, res);
 503                 }
 504                 Rvalue::CheckedBinaryOp(bin_op, box (ref lhs, ref rhs)) => {
 505                     let lhs = codegen_operand(fx, lhs);
 506                     let rhs = codegen_operand(fx, rhs);
 507
 508                     let res = if !fx.tcx.sess.overflow_checks() {
 509                         let val =
 510                             crate::num::codegen_int_binop(fx, bin_op, lhs, rhs).load_scalar(fx);
 511                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 512                         CValue::by_val_pair(val, is_overflow, lval.layout())
 513                     } else {
 514                         crate::num::codegen_checked_int_binop(fx, bin_op, lhs, rhs)
 515                     };
 516
 517                     lval.write_cvalue(fx, res);
 518                 }
 519                 Rvalue::UnaryOp(un_op, ref operand) => {
 520                     let operand = codegen_operand(fx, operand);
 521                     let layout = operand.layout();
 522                     let val = operand.load_scalar(fx);
 523                     let res = match un_op {
 524                         UnOp::Not => match layout.ty.kind() {
 525                             ty::Bool => {
 526                                 let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 527                                 CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 528                             }
 529                             ty::Uint(_) | ty::Int(_) => {
 530                                 CValue::by_val(fx.bcx.ins().bnot(val), layout)
 531                             }
 532                             _ => unreachable!("un op Not for {:?}", layout.ty),
 533                         },
 534                         UnOp::Neg => match layout.ty.kind() {
 535                             ty::Int(IntTy::I128) => {
 536                                 // FIXME remove this case once ineg.i128 works
 537                                 let zero =
 538                                     CValue::const_val(fx, layout, ty::ScalarInt::null(layout.size));
 539                                 crate::num::codegen_int_binop(fx, BinOp::Sub, zero, operand)
 540                             }
 541                             ty::Int(_) => CValue::by_val(fx.bcx.ins().ineg(val), layout),
 542                             ty::Float(_) => CValue::by_val(fx.bcx.ins().fneg(val), layout),
 543                             _ => unreachable!("un op Neg for {:?}", layout.ty),
 544                         },
 545                     };
 546                     lval.write_cvalue(fx, res);
 547                 }
 548                 Rvalue::Cast(
 549                     CastKind::Pointer(PointerCast::ReifyFnPointer),
 550                     ref operand,
 551                     to_ty,
 552                 ) => {
 553                     let from_ty = fx.monomorphize(operand.ty(&fx.mir.local_decls, fx.tcx));
 554                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 555                     match *from_ty.kind() {
 556                         ty::FnDef(def_id, substs) => {
 557                             let func_ref = fx.get_function_ref(
 558                                 Instance::resolve_for_fn_ptr(
 559                                     fx.tcx,
 560                                     ParamEnv::reveal_all(),
 561                                     def_id,
 562                                     substs,
 563                                 )
 564                                 .unwrap()
 565                                 .polymorphize(fx.tcx),
 566                             );
 567                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 568                             lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
 569                         }
 570                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
 571                     }
 572                 }
 573                 Rvalue::Cast(
 574                     CastKind::Pointer(PointerCast::UnsafeFnPointer),
 575                     ref operand,
 576                     to_ty,
 577                 )
 578                 | Rvalue::Cast(
 579                     CastKind::Pointer(PointerCast::MutToConstPointer),
 580                     ref operand,
 581                     to_ty,
 582                 )
 583                 | Rvalue::Cast(
 584                     CastKind::Pointer(PointerCast::ArrayToPointer),
 585                     ref operand,
 586                     to_ty,
 587                 ) => {
 588                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 589                     let operand = codegen_operand(fx, operand);
 590                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
 591                 }
 592                 Rvalue::Cast(CastKind::Misc, ref operand, to_ty) => {
 593                     let operand = codegen_operand(fx, operand);
 594                     let from_ty = operand.layout().ty;
 595                     let to_ty = fx.monomorphize(to_ty);
 596
 597                     fn is_fat_ptr<'tcx>(
 598                         fx: &FunctionCx<'_, 'tcx, impl Module>,
 599                         ty: Ty<'tcx>,
 600                     ) -> bool {
 601                         ty.builtin_deref(true)
 602                             .map(
 603                                 |ty::TypeAndMut {
 604                                      ty: pointee_ty,
 605                                      mutbl: _,
 606                                  }| {
 607                                     has_ptr_meta(fx.tcx, pointee_ty)
 608                                 },
 609                             )
 610                             .unwrap_or(false)
 611                     }
 612
 613                     if is_fat_ptr(fx, from_ty) {
 614                         if is_fat_ptr(fx, to_ty) {
 615                             // fat-ptr -> fat-ptr
 616                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
 617                         } else {
 618                             // fat-ptr -> thin-ptr
 619                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 620                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 621                         }
 622                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind() {
 623                         // enum -> discriminant value
 624                         assert!(adt_def.is_enum());
 625                         match to_ty.kind() {
 626                             ty::Uint(_) | ty::Int(_) => {}
 627                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 628                         }
 629
 630                         use rustc_target::abi::{Int, TagEncoding, Variants};
 631
 632                         match operand.layout().variants {
 633                             Variants::Single { index } => {
 634                                 let discr = operand
 635                                     .layout()
 636                                     .ty
 637                                     .discriminant_for_variant(fx.tcx, index)
 638                                     .unwrap();
 639                                 let discr = if discr.ty.is_signed() {
 640                                     fx.layout_of(discr.ty).size.sign_extend(discr.val)
 641                                 } else {
 642                                     discr.val
 643                                 };
 644                                 let discr = discr.into();
 645
 646                                 let discr = CValue::const_val(fx, fx.layout_of(to_ty), discr);
 647                                 lval.write_cvalue(fx, discr);
 648                             }
 649                             Variants::Multiple {
 650                                 ref tag,
 651                                 tag_field,
 652                                 tag_encoding: TagEncoding::Direct,
 653                                 variants: _,
 654                             } => {
 655                                 let cast_to = fx.clif_type(dest_layout.ty).unwrap();
 656
 657                                 // Read the tag/niche-encoded discriminant from memory.
 658                                 let encoded_discr =
 659                                     operand.value_field(fx, mir::Field::new(tag_field));
 660                                 let encoded_discr = encoded_discr.load_scalar(fx);
 661
 662                                 // Decode the discriminant (specifically if it's niche-encoded).
 663                                 let signed = match tag.value {
 664                                     Int(_, signed) => signed,
 665                                     _ => false,
 666                                 };
 667                                 let val = clif_intcast(fx, encoded_discr, cast_to, signed);
 668                                 let val = CValue::by_val(val, dest_layout);
 669                                 lval.write_cvalue(fx, val);
 670                             }
 671                             Variants::Multiple { .. } => unreachable!(),
 672                         }
 673                     } else {
 674                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 675                         let from = operand.load_scalar(fx);
 676
 677                         let res = clif_int_or_float_cast(
 678                             fx,
 679                             from,
 680                             type_sign(from_ty),
 681                             to_clif_ty,
 682                             type_sign(to_ty),
 683                         );
 684                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 685                     }
 686                 }
 687                 Rvalue::Cast(
 688                     CastKind::Pointer(PointerCast::ClosureFnPointer(_)),
 689                     ref operand,
 690                     _to_ty,
 691                 ) => {
 692                     let operand = codegen_operand(fx, operand);
 693                     match *operand.layout().ty.kind() {
 694                         ty::Closure(def_id, substs) => {
 695                             let instance = Instance::resolve_closure(
 696                                 fx.tcx,
 697                                 def_id,
 698                                 substs,
 699                                 ty::ClosureKind::FnOnce,
 700                             )
 701                             .polymorphize(fx.tcx);
 702                             let func_ref = fx.get_function_ref(instance);
 703                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 704                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 705                         }
 706                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 707                     }
 708                 }
 709                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), ref operand, _to_ty) => {
 710                     let operand = codegen_operand(fx, operand);
 711                     operand.unsize_value(fx, lval);
 712                 }
 713                 Rvalue::Discriminant(place) => {
 714                     let place = codegen_place(fx, place);
 715                     let value = place.to_cvalue(fx);
 716                     let discr =
 717                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 718                     lval.write_cvalue(fx, discr);
 719                 }
 720                 Rvalue::Repeat(ref operand, times) => {
 721                     let operand = codegen_operand(fx, operand);
 722                     let times = fx
 723                         .monomorphize(times)
 724                         .eval(fx.tcx, ParamEnv::reveal_all())
 725                         .val
 726                         .try_to_bits(fx.tcx.data_layout.pointer_size)
 727                         .unwrap();
 728                     if fx.clif_type(operand.layout().ty) == Some(types::I8) {
 729                         let times = fx.bcx.ins().iconst(fx.pointer_type, times as i64);
 730                         // FIXME use emit_small_memset where possible
 731                         let addr = lval.to_ptr().get_addr(fx);
 732                         let val = operand.load_scalar(fx);
 733                         fx.bcx
 734                             .call_memset(fx.cx.module.target_config(), addr, val, times);
 735                     } else {
 736                         let loop_block = fx.bcx.create_block();
 737                         let loop_block2 = fx.bcx.create_block();
 738                         let done_block = fx.bcx.create_block();
 739                         let index = fx.bcx.append_block_param(loop_block, fx.pointer_type);
 740                         let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
 741                         fx.bcx.ins().jump(loop_block, &[zero]);
 742
 743                         fx.bcx.switch_to_block(loop_block);
 744                         let done = fx.bcx.ins().icmp_imm(IntCC::Equal, index, times as i64);
 745                         fx.bcx.ins().brnz(done, done_block, &[]);
 746                         fx.bcx.ins().jump(loop_block2, &[]);
 747
 748                         fx.bcx.switch_to_block(loop_block2);
 749                         let to = lval.place_index(fx, index);
 750                         to.write_cvalue(fx, operand);
 751                         let index = fx.bcx.ins().iadd_imm(index, 1);
 752                         fx.bcx.ins().jump(loop_block, &[index]);
 753
 754                         fx.bcx.switch_to_block(done_block);
 755                         fx.bcx.ins().nop();
 756                     }
 757                 }
 758                 Rvalue::Len(place) => {
 759                     let place = codegen_place(fx, place);
 760                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 761                     let len = codegen_array_len(fx, place);
 762                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 763                 }
 764                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 765                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 766                     let content_ty = fx.monomorphize(content_ty);
 767                     let layout = fx.layout_of(content_ty);
 768                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 769                     let llalign = fx
 770                         .bcx
 771                         .ins()
 772                         .iconst(usize_type, layout.align.abi.bytes() as i64);
 773                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 774
 775                     // Allocate space:
 776                     let def_id = match fx
 777                         .tcx
 778                         .lang_items()
 779                         .require(rustc_hir::LangItem::ExchangeMalloc)
 780                     {
 781                         Ok(id) => id,
 782                         Err(s) => {
 783                             fx.tcx
 784                                 .sess
 785                                 .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 786                         }
 787                     };
 788                     let instance = ty::Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
 789                     let func_ref = fx.get_function_ref(instance);
 790                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 791                     let ptr = fx.bcx.inst_results(call)[0];
 792                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 793                 }
 794                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 795                     assert!(lval
 796                         .layout()
 797                         .ty
 798                         .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all()));
 799                     let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
 800                     let val =
 801                         CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
 802                     lval.write_cvalue(fx, val);
 803                 }
 804                 Rvalue::Aggregate(ref kind, ref operands) => match kind.as_ref() {
 805                     AggregateKind::Array(_ty) => {
 806                         for (i, operand) in operands.iter().enumerate() {
 807                             let operand = codegen_operand(fx, operand);
 808                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 809                             let to = lval.place_index(fx, index);
 810                             to.write_cvalue(fx, operand);
 811                         }
 812                     }
 813                     _ => unreachable!("shouldn't exist at codegen {:?}", to_place_and_rval.1),
 814                 },
 815             }
 816         }
 817         StatementKind::StorageLive(_)
 818         | StatementKind::StorageDead(_)
 819         | StatementKind::Nop
 820         | StatementKind::FakeRead(..)
 821         | StatementKind::Retag { .. }
 822         | StatementKind::AscribeUserType(..) => {}
 823
 824         StatementKind::LlvmInlineAsm(asm) => {
 825             use rustc_span::symbol::Symbol;
 826             let LlvmInlineAsm {
 827                 asm,
 828                 outputs,
 829                 inputs,
 830             } = &**asm;
 831             let rustc_hir::LlvmInlineAsmInner {
 832                 asm: asm_code,         // Name
 833                 outputs: output_names, // Vec<LlvmInlineAsmOutput>
 834                 inputs: input_names,   // Vec<Name>
 835                 clobbers,              // Vec<Name>
 836                 volatile,              // bool
 837                 alignstack,            // bool
 838                 dialect: _,
 839                 asm_str_style: _,
 840             } = asm;
 841             match asm_code.as_str().trim() {
 842                 "" => {
 843                     // Black box
 844                 }
 845                 "mov %rbx, %rsi\n                  cpuid\n                  xchg %rbx, %rsi" => {
 846                     assert_eq!(
 847                         input_names,
 848                         &[Symbol::intern("{eax}"), Symbol::intern("{ecx}")]
 849                     );
 850                     assert_eq!(output_names.len(), 4);
 851                     for (i, c) in (&["={eax}", "={esi}", "={ecx}", "={edx}"])
 852                         .iter()
 853                         .enumerate()
 854                     {
 855                         assert_eq!(&output_names[i].constraint.as_str(), c);
 856                         assert!(!output_names[i].is_rw);
 857                         assert!(!output_names[i].is_indirect);
 858                     }
 859
 860                     assert_eq!(clobbers, &[]);
 861
 862                     assert!(!volatile);
 863                     assert!(!alignstack);
 864
 865                     assert_eq!(inputs.len(), 2);
 866                     let leaf = codegen_operand(fx, &inputs[0].1).load_scalar(fx); // %eax
 867                     let subleaf = codegen_operand(fx, &inputs[1].1).load_scalar(fx); // %ecx
 868
 869                     let (eax, ebx, ecx, edx) =
 870                         crate::intrinsics::codegen_cpuid_call(fx, leaf, subleaf);
 871
 872                     assert_eq!(outputs.len(), 4);
 873                     codegen_place(fx, outputs[0])
 874                         .write_cvalue(fx, CValue::by_val(eax, fx.layout_of(fx.tcx.types.u32)));
 875                     codegen_place(fx, outputs[1])
 876                         .write_cvalue(fx, CValue::by_val(ebx, fx.layout_of(fx.tcx.types.u32)));
 877                     codegen_place(fx, outputs[2])
 878                         .write_cvalue(fx, CValue::by_val(ecx, fx.layout_of(fx.tcx.types.u32)));
 879                     codegen_place(fx, outputs[3])
 880                         .write_cvalue(fx, CValue::by_val(edx, fx.layout_of(fx.tcx.types.u32)));
 881                 }
 882                 "xgetbv" => {
 883                     assert_eq!(input_names, &[Symbol::intern("{ecx}")]);
 884
 885                     assert_eq!(output_names.len(), 2);
 886                     for (i, c) in (&["={eax}", "={edx}"]).iter().enumerate() {
 887                         assert_eq!(&output_names[i].constraint.as_str(), c);
 888                         assert!(!output_names[i].is_rw);
 889                         assert!(!output_names[i].is_indirect);
 890                     }
 891
 892                     assert_eq!(clobbers, &[]);
 893
 894                     assert!(!volatile);
 895                     assert!(!alignstack);
 896
 897                     crate::trap::trap_unimplemented(fx, "_xgetbv arch intrinsic is not supported");
 898                 }
 899                 // ___chkstk, ___chkstk_ms and __alloca are only used on Windows
 900                 _ if fx
 901                     .tcx
 902                     .symbol_name(fx.instance)
 903                     .name
 904                     .starts_with("___chkstk") =>
 905                 {
 906                     crate::trap::trap_unimplemented(fx, "Stack probes are not supported");
 907                 }
 908                 _ if fx.tcx.symbol_name(fx.instance).name == "__alloca" => {
 909                     crate::trap::trap_unimplemented(fx, "Alloca is not supported");
 910                 }
 911                 // Used in sys::windows::abort_internal
 912                 "int $$0x29" => {
 913                     crate::trap::trap_unimplemented(fx, "Windows abort");
 914                 }
 915                 _ => fx
 916                     .tcx
 917                     .sess
 918                     .span_fatal(stmt.source_info.span, "Inline assembly is not supported"),
 919             }
 920         }
 921         StatementKind::Coverage { .. } => fx.tcx.sess.fatal("-Zcoverage is unimplemented"),
 922     }
 923 }
 924
 925 fn codegen_array_len<'tcx>(
 926     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
 927     place: CPlace<'tcx>,
 928 ) -> Value {
 929     match *place.layout().ty.kind() {
 930         ty::Array(_elem_ty, len) => {
 931             let len = fx
 932                 .monomorphize(len)
 933                 .eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 934             fx.bcx.ins().iconst(fx.pointer_type, len)
 935         }
 936         ty::Slice(_elem_ty) => place
 937             .to_ptr_maybe_unsized()
 938             .1
 939             .expect("Length metadata for slice place"),
 940         _ => bug!("Rvalue::Len({:?})", place),
 941     }
 942 }
 943
 944 pub(crate) fn codegen_place<'tcx>(
 945     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
 946     place: Place<'tcx>,
 947 ) -> CPlace<'tcx> {
 948     let mut cplace = fx.get_local_place(place.local);
 949
 950     for elem in place.projection {
 951         match elem {
 952             PlaceElem::Deref => {
 953                 cplace = cplace.place_deref(fx);
 954             }
 955             PlaceElem::Field(field, _ty) => {
 956                 cplace = cplace.place_field(fx, field);
 957             }
 958             PlaceElem::Index(local) => {
 959                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 960                 cplace = cplace.place_index(fx, index);
 961             }
 962             PlaceElem::ConstantIndex {
 963                 offset,
 964                 min_length: _,
 965                 from_end,
 966             } => {
 967                 let offset: u64 = offset;
 968                 let index = if !from_end {
 969                     fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 970                 } else {
 971                     let len = codegen_array_len(fx, cplace);
 972                     fx.bcx.ins().iadd_imm(len, -(offset as i64))
 973                 };
 974                 cplace = cplace.place_index(fx, index);
 975             }
 976             PlaceElem::Subslice { from, to, from_end } => {
 977                 // These indices are generated by slice patterns.
 978                 // slice[from:-to] in Python terms.
 979
 980                 let from: u64 = from;
 981                 let to: u64 = to;
 982
 983                 match cplace.layout().ty.kind() {
 984                     ty::Array(elem_ty, _len) => {
 985                         assert!(!from_end, "array subslices are never `from_end`");
 986                         let elem_layout = fx.layout_of(elem_ty);
 987                         let ptr = cplace.to_ptr();
 988                         cplace = CPlace::for_ptr(
 989                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
 990                             fx.layout_of(fx.tcx.mk_array(elem_ty, to - from)),
 991                         );
 992                     }
 993                     ty::Slice(elem_ty) => {
 994                         assert!(from_end, "slice subslices should be `from_end`");
 995                         let elem_layout = fx.layout_of(elem_ty);
 996                         let (ptr, len) = cplace.to_ptr_maybe_unsized();
 997                         let len = len.unwrap();
 998                         cplace = CPlace::for_ptr_with_extra(
 999                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
1000                             fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
1001                             cplace.layout(),
1002                         );
1003                     }
1004                     _ => unreachable!(),
1005                 }
1006             }
1007             PlaceElem::Downcast(_adt_def, variant) => {
1008                 cplace = cplace.downcast_variant(fx, variant);
1009             }
1010         }
1011     }
1012
1013     cplace
1014 }
1015
1016 pub(crate) fn codegen_operand<'tcx>(
1017     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
1018     operand: &Operand<'tcx>,
1019 ) -> CValue<'tcx> {
1020     match operand {
1021         Operand::Move(place) | Operand::Copy(place) => {
1022             let cplace = codegen_place(fx, *place);
1023             cplace.to_cvalue(fx)
1024         }
1025         Operand::Constant(const_) => crate::constant::codegen_constant(fx, const_),
1026     }
1027 }
1028
1029 pub(crate) fn codegen_panic<'tcx>(
1030     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
1031     msg_str: &str,
1032     span: Span,
1033 ) {
1034     let location = fx.get_caller_location(span).load_scalar(fx);
1035
1036     let msg_ptr = fx.anonymous_str("assert", msg_str);
1037     let msg_len = fx
1038         .bcx
1039         .ins()
1040         .iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
1041     let args = [msg_ptr, msg_len, location];
1042
1043     codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, span);
1044 }
1045
1046 pub(crate) fn codegen_panic_inner<'tcx>(
1047     fx: &mut FunctionCx<'_, 'tcx, impl Module>,
1048     lang_item: rustc_hir::LangItem,
1049     args: &[Value],
1050     span: Span,
1051 ) {
1052     let def_id = fx
1053         .tcx
1054         .lang_items()
1055         .require(lang_item)
1056         .unwrap_or_else(|s| fx.tcx.sess.span_fatal(span, &s));
1057
1058     let instance = Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
1059     let symbol_name = fx.tcx.symbol_name(instance).name;
1060
1061     fx.lib_call(
1062         &*symbol_name,
1063         vec![
1064             AbiParam::new(fx.pointer_type),
1065             AbiParam::new(fx.pointer_type),
1066             AbiParam::new(fx.pointer_type),
1067         ],
1068         vec![],
1069         args,
1070     );
1071
1072     crate::trap::trap_unreachable(fx, "panic lang item returned");
1073 }