src/base.rs

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