src/base.rs

   1 //! Codegen of a single function
   2
   3 use rustc_ast::InlineAsmOptions;
   4 use rustc_index::vec::IndexVec;
   5 use rustc_middle::ty::adjustment::PointerCast;
   6 use rustc_middle::ty::layout::FnAbiOf;
   7
   8 use indexmap::IndexSet;
   9
  10 use crate::constant::ConstantCx;
  11 use crate::prelude::*;
  12 use crate::pretty_clif::CommentWriter;
  13
  14 pub(crate) fn codegen_fn<'tcx>(
  15     cx: &mut crate::CodegenCx<'tcx>,
  16     module: &mut dyn Module,
  17     instance: Instance<'tcx>,
  18 ) {
  19     let tcx = cx.tcx;
  20
  21     let _inst_guard =
  22         crate::PrintOnPanic(|| format!("{:?} {}", instance, tcx.symbol_name(instance).name));
  23     debug_assert!(!instance.substs.needs_infer());
  24
  25     let mir = tcx.instance_mir(instance.def);
  26     let _mir_guard = crate::PrintOnPanic(|| {
  27         let mut buf = Vec::new();
  28         rustc_middle::mir::write_mir_pretty(tcx, Some(instance.def_id()), &mut buf).unwrap();
  29         String::from_utf8_lossy(&buf).into_owned()
  30     });
  31
  32     // Declare function
  33     let symbol_name = tcx.symbol_name(instance);
  34     let sig = get_function_sig(tcx, module.isa().triple(), instance);
  35     let func_id = module.declare_function(symbol_name.name, Linkage::Local, &sig).unwrap();
  36
  37     cx.cached_context.clear();
  38
  39     // Make the FunctionBuilder
  40     let mut func_ctx = FunctionBuilderContext::new();
  41     let mut func = std::mem::replace(&mut cx.cached_context.func, Function::new());
  42     func.name = ExternalName::user(0, func_id.as_u32());
  43     func.signature = sig;
  44     func.collect_debug_info();
  45
  46     let mut bcx = FunctionBuilder::new(&mut func, &mut func_ctx);
  47
  48     // Predefine blocks
  49     let start_block = bcx.create_block();
  50     let block_map: IndexVec<BasicBlock, Block> =
  51         (0..mir.basic_blocks().len()).map(|_| bcx.create_block()).collect();
  52
  53     // Make FunctionCx
  54     let target_config = module.target_config();
  55     let pointer_type = target_config.pointer_type();
  56     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  57
  58     let mut fx = FunctionCx {
  59         cx,
  60         module,
  61         tcx,
  62         target_config,
  63         pointer_type,
  64         constants_cx: ConstantCx::new(),
  65
  66         instance,
  67         symbol_name,
  68         mir,
  69         fn_abi: Some(RevealAllLayoutCx(tcx).fn_abi_of_instance(instance, ty::List::empty())),
  70
  71         bcx,
  72         block_map,
  73         local_map: IndexVec::with_capacity(mir.local_decls.len()),
  74         caller_location: None, // set by `codegen_fn_prelude`
  75
  76         clif_comments,
  77         source_info_set: indexmap::IndexSet::new(),
  78         next_ssa_var: 0,
  79     };
  80
  81     let arg_uninhabited = fx
  82         .mir
  83         .args_iter()
  84         .any(|arg| fx.layout_of(fx.monomorphize(fx.mir.local_decls[arg].ty)).abi.is_uninhabited());
  85
  86     if !crate::constant::check_constants(&mut fx) {
  87         fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
  88         fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
  89         crate::trap::trap_unreachable(&mut fx, "compilation should have been aborted");
  90     } else if arg_uninhabited {
  91         fx.bcx.append_block_params_for_function_params(fx.block_map[START_BLOCK]);
  92         fx.bcx.switch_to_block(fx.block_map[START_BLOCK]);
  93         crate::trap::trap_unreachable(&mut fx, "function has uninhabited argument");
  94     } else {
  95         tcx.sess.time("codegen clif ir", || {
  96             tcx.sess
  97                 .time("codegen prelude", || crate::abi::codegen_fn_prelude(&mut fx, start_block));
  98             codegen_fn_content(&mut fx);
  99         });
 100     }
 101
 102     // Recover all necessary data from fx, before accessing func will prevent future access to it.
 103     let instance = fx.instance;
 104     let clif_comments = fx.clif_comments;
 105     let source_info_set = fx.source_info_set;
 106     let local_map = fx.local_map;
 107
 108     fx.constants_cx.finalize(fx.tcx, &mut *fx.module);
 109
 110     crate::pretty_clif::write_clif_file(
 111         tcx,
 112         "unopt",
 113         module.isa(),
 114         instance,
 115         &func,
 116         &clif_comments,
 117     );
 118
 119     // Verify function
 120     verify_func(tcx, &clif_comments, &func);
 121
 122     compile_fn(
 123         cx,
 124         module,
 125         instance,
 126         symbol_name.name,
 127         func_id,
 128         func,
 129         clif_comments,
 130         source_info_set,
 131         local_map,
 132     );
 133 }
 134
 135 fn compile_fn<'tcx>(
 136     cx: &mut crate::CodegenCx<'tcx>,
 137     module: &mut dyn Module,
 138     instance: Instance<'tcx>,
 139     symbol_name: &str,
 140     func_id: FuncId,
 141     func: Function,
 142     mut clif_comments: CommentWriter,
 143     source_info_set: IndexSet<SourceInfo>,
 144     local_map: IndexVec<mir::Local, CPlace<'tcx>>,
 145 ) {
 146     let tcx = cx.tcx;
 147
 148     // Store function in context
 149     let context = &mut cx.cached_context;
 150     context.clear();
 151     context.func = func;
 152
 153     // If the return block is not reachable, then the SSA builder may have inserted an `iconst.i128`
 154     // instruction, which doesn't have an encoding.
 155     context.compute_cfg();
 156     context.compute_domtree();
 157     context.eliminate_unreachable_code(module.isa()).unwrap();
 158     context.dce(module.isa()).unwrap();
 159     // Some Cranelift optimizations expect the domtree to not yet be computed and as such don't
 160     // invalidate it when it would change.
 161     context.domtree.clear();
 162
 163     // Perform rust specific optimizations
 164     tcx.sess.time("optimize clif ir", || {
 165         crate::optimize::optimize_function(
 166             tcx,
 167             module.isa(),
 168             instance,
 169             context,
 170             &mut clif_comments,
 171         );
 172     });
 173
 174     // Define function
 175     tcx.sess.time("define function", || {
 176         context.want_disasm = crate::pretty_clif::should_write_ir(tcx);
 177         module.define_function(func_id, context).unwrap()
 178     });
 179
 180     // Write optimized function to file for debugging
 181     crate::pretty_clif::write_clif_file(
 182         tcx,
 183         "opt",
 184         module.isa(),
 185         instance,
 186         &context.func,
 187         &clif_comments,
 188     );
 189
 190     if let Some(disasm) = &context.mach_compile_result.as_ref().unwrap().disasm {
 191         crate::pretty_clif::write_ir_file(
 192             tcx,
 193             || format!("{}.vcode", tcx.symbol_name(instance).name),
 194             |file| file.write_all(disasm.as_bytes()),
 195         )
 196     }
 197
 198     // Define debuginfo for function
 199     let isa = module.isa();
 200     let debug_context = &mut cx.debug_context;
 201     let unwind_context = &mut cx.unwind_context;
 202     tcx.sess.time("generate debug info", || {
 203         if let Some(debug_context) = debug_context {
 204             debug_context.define_function(
 205                 instance,
 206                 func_id,
 207                 symbol_name,
 208                 isa,
 209                 context,
 210                 &source_info_set,
 211                 local_map,
 212             );
 213         }
 214         unwind_context.add_function(func_id, &context, isa);
 215     });
 216 }
 217
 218 pub(crate) fn verify_func(
 219     tcx: TyCtxt<'_>,
 220     writer: &crate::pretty_clif::CommentWriter,
 221     func: &Function,
 222 ) {
 223     tcx.sess.time("verify clif ir", || {
 224         let flags = cranelift_codegen::settings::Flags::new(cranelift_codegen::settings::builder());
 225         match cranelift_codegen::verify_function(&func, &flags) {
 226             Ok(_) => {}
 227             Err(err) => {
 228                 tcx.sess.err(&format!("{:?}", err));
 229                 let pretty_error = cranelift_codegen::print_errors::pretty_verifier_error(
 230                     &func,
 231                     Some(Box::new(writer)),
 232                     err,
 233                 );
 234                 tcx.sess.fatal(&format!("cranelift verify error:\n{}", pretty_error));
 235             }
 236         }
 237     });
 238 }
 239
 240 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, '_>) {
 241     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 242         let block = fx.get_block(bb);
 243         fx.bcx.switch_to_block(block);
 244
 245         if bb_data.is_cleanup {
 246             // Unwinding after panicking is not supported
 247             continue;
 248
 249             // FIXME Once unwinding is supported and Cranelift supports marking blocks as cold, do
 250             // so for cleanup blocks.
 251         }
 252
 253         fx.bcx.ins().nop();
 254         for stmt in &bb_data.statements {
 255             fx.set_debug_loc(stmt.source_info);
 256             codegen_stmt(fx, block, stmt);
 257         }
 258
 259         if fx.clif_comments.enabled() {
 260             let mut terminator_head = "\n".to_string();
 261             bb_data.terminator().kind.fmt_head(&mut terminator_head).unwrap();
 262             let inst = fx.bcx.func.layout.last_inst(block).unwrap();
 263             fx.add_comment(inst, terminator_head);
 264         }
 265
 266         let source_info = bb_data.terminator().source_info;
 267         fx.set_debug_loc(source_info);
 268
 269         match &bb_data.terminator().kind {
 270             TerminatorKind::Goto { target } => {
 271                 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
 272                     let mut can_immediately_return = true;
 273                     for stmt in &fx.mir[*target].statements {
 274                         if let StatementKind::StorageDead(_) = stmt.kind {
 275                         } else {
 276                             // FIXME Can sometimes happen, see rust-lang/rust#70531
 277                             can_immediately_return = false;
 278                             break;
 279                         }
 280                     }
 281
 282                     if can_immediately_return {
 283                         crate::abi::codegen_return(fx);
 284                         continue;
 285                     }
 286                 }
 287
 288                 let block = fx.get_block(*target);
 289                 fx.bcx.ins().jump(block, &[]);
 290             }
 291             TerminatorKind::Return => {
 292                 crate::abi::codegen_return(fx);
 293             }
 294             TerminatorKind::Assert { cond, expected, msg, target, cleanup: _ } => {
 295                 if !fx.tcx.sess.overflow_checks() {
 296                     if let mir::AssertKind::OverflowNeg(_) = *msg {
 297                         let target = fx.get_block(*target);
 298                         fx.bcx.ins().jump(target, &[]);
 299                         continue;
 300                     }
 301                 }
 302                 let cond = codegen_operand(fx, cond).load_scalar(fx);
 303
 304                 let target = fx.get_block(*target);
 305                 let failure = fx.bcx.create_block();
 306                 // FIXME Mark failure block as cold once Cranelift supports it
 307
 308                 if *expected {
 309                     fx.bcx.ins().brz(cond, failure, &[]);
 310                 } else {
 311                     fx.bcx.ins().brnz(cond, failure, &[]);
 312                 };
 313                 fx.bcx.ins().jump(target, &[]);
 314
 315                 fx.bcx.switch_to_block(failure);
 316                 fx.bcx.ins().nop();
 317
 318                 match msg {
 319                     AssertKind::BoundsCheck { ref len, ref index } => {
 320                         let len = codegen_operand(fx, len).load_scalar(fx);
 321                         let index = codegen_operand(fx, index).load_scalar(fx);
 322                         let location = fx.get_caller_location(source_info.span).load_scalar(fx);
 323
 324                         codegen_panic_inner(
 325                             fx,
 326                             rustc_hir::LangItem::PanicBoundsCheck,
 327                             &[index, len, location],
 328                             source_info.span,
 329                         );
 330                     }
 331                     _ => {
 332                         let msg_str = msg.description();
 333                         codegen_panic(fx, msg_str, source_info.span);
 334                     }
 335                 }
 336             }
 337
 338             TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
 339                 let discr = codegen_operand(fx, discr).load_scalar(fx);
 340
 341                 let use_bool_opt = switch_ty.kind() == fx.tcx.types.bool.kind()
 342                     || (targets.iter().count() == 1 && targets.iter().next().unwrap().0 == 0);
 343                 if use_bool_opt {
 344                     assert_eq!(targets.iter().count(), 1);
 345                     let (then_value, then_block) = targets.iter().next().unwrap();
 346                     let then_block = fx.get_block(then_block);
 347                     let else_block = fx.get_block(targets.otherwise());
 348                     let test_zero = match then_value {
 349                         0 => true,
 350                         1 => false,
 351                         _ => unreachable!("{:?}", targets),
 352                     };
 353
 354                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 355                     let (discr, is_inverted) =
 356                         crate::optimize::peephole::maybe_unwrap_bool_not(&mut fx.bcx, discr);
 357                     let test_zero = if is_inverted { !test_zero } else { test_zero };
 358                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 359                     if let Some(taken) = crate::optimize::peephole::maybe_known_branch_taken(
 360                         &fx.bcx, discr, test_zero,
 361                     ) {
 362                         if taken {
 363                             fx.bcx.ins().jump(then_block, &[]);
 364                         } else {
 365                             fx.bcx.ins().jump(else_block, &[]);
 366                         }
 367                     } else {
 368                         if test_zero {
 369                             fx.bcx.ins().brz(discr, then_block, &[]);
 370                             fx.bcx.ins().jump(else_block, &[]);
 371                         } else {
 372                             fx.bcx.ins().brnz(discr, then_block, &[]);
 373                             fx.bcx.ins().jump(else_block, &[]);
 374                         }
 375                     }
 376                 } else {
 377                     let mut switch = ::cranelift_frontend::Switch::new();
 378                     for (value, block) in targets.iter() {
 379                         let block = fx.get_block(block);
 380                         switch.set_entry(value, block);
 381                     }
 382                     let otherwise_block = fx.get_block(targets.otherwise());
 383                     switch.emit(&mut fx.bcx, discr, otherwise_block);
 384                 }
 385             }
 386             TerminatorKind::Call {
 387                 func,
 388                 args,
 389                 destination,
 390                 fn_span,
 391                 cleanup: _,
 392                 from_hir_call: _,
 393             } => {
 394                 fx.tcx.sess.time("codegen call", || {
 395                     crate::abi::codegen_terminator_call(fx, *fn_span, func, args, *destination)
 396                 });
 397             }
 398             TerminatorKind::InlineAsm {
 399                 template,
 400                 operands,
 401                 options,
 402                 destination,
 403                 line_spans: _,
 404                 cleanup: _,
 405             } => {
 406                 if options.contains(InlineAsmOptions::MAY_UNWIND) {
 407                     fx.tcx.sess.span_fatal(
 408                         source_info.span,
 409                         "cranelift doesn't support unwinding from inline assembly.",
 410                     );
 411                 }
 412
 413                 crate::inline_asm::codegen_inline_asm(
 414                     fx,
 415                     source_info.span,
 416                     template,
 417                     operands,
 418                     *options,
 419                 );
 420
 421                 match *destination {
 422                     Some(destination) => {
 423                         let destination_block = fx.get_block(destination);
 424                         fx.bcx.ins().jump(destination_block, &[]);
 425                     }
 426                     None => {
 427                         crate::trap::trap_unreachable(
 428                             fx,
 429                             "[corruption] Returned from noreturn inline asm",
 430                         );
 431                     }
 432                 }
 433             }
 434             TerminatorKind::Resume | TerminatorKind::Abort => {
 435                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 436             }
 437             TerminatorKind::Unreachable => {
 438                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 439             }
 440             TerminatorKind::Yield { .. }
 441             | TerminatorKind::FalseEdge { .. }
 442             | TerminatorKind::FalseUnwind { .. }
 443             | TerminatorKind::DropAndReplace { .. }
 444             | TerminatorKind::GeneratorDrop => {
 445                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
 446             }
 447             TerminatorKind::Drop { place, target, unwind: _ } => {
 448                 let drop_place = codegen_place(fx, *place);
 449                 crate::abi::codegen_drop(fx, source_info.span, drop_place);
 450
 451                 let target_block = fx.get_block(*target);
 452                 fx.bcx.ins().jump(target_block, &[]);
 453             }
 454         };
 455     }
 456
 457     fx.bcx.seal_all_blocks();
 458     fx.bcx.finalize();
 459 }
 460
 461 fn codegen_stmt<'tcx>(
 462     fx: &mut FunctionCx<'_, '_, 'tcx>,
 463     #[allow(unused_variables)] cur_block: Block,
 464     stmt: &Statement<'tcx>,
 465 ) {
 466     let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
 467
 468     fx.set_debug_loc(stmt.source_info);
 469
 470     #[cfg(disabled)]
 471     match &stmt.kind {
 472         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 473         _ => {
 474             if fx.clif_comments.enabled() {
 475                 let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
 476                 fx.add_comment(inst, format!("{:?}", stmt));
 477             }
 478         }
 479     }
 480
 481     match &stmt.kind {
 482         StatementKind::SetDiscriminant { place, variant_index } => {
 483             let place = codegen_place(fx, **place);
 484             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 485         }
 486         StatementKind::Assign(to_place_and_rval) => {
 487             let lval = codegen_place(fx, to_place_and_rval.0);
 488             let dest_layout = lval.layout();
 489             match to_place_and_rval.1 {
 490                 Rvalue::Use(ref operand) => {
 491                     let val = codegen_operand(fx, operand);
 492                     lval.write_cvalue(fx, val);
 493                 }
 494                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
 495                     let place = codegen_place(fx, place);
 496                     let ref_ = place.place_ref(fx, lval.layout());
 497                     lval.write_cvalue(fx, ref_);
 498                 }
 499                 Rvalue::ThreadLocalRef(def_id) => {
 500                     let val = crate::constant::codegen_tls_ref(fx, def_id, lval.layout());
 501                     lval.write_cvalue(fx, val);
 502                 }
 503                 Rvalue::BinaryOp(bin_op, ref lhs_rhs) => {
 504                     let lhs = codegen_operand(fx, &lhs_rhs.0);
 505                     let rhs = codegen_operand(fx, &lhs_rhs.1);
 506
 507                     let res = crate::num::codegen_binop(fx, bin_op, lhs, rhs);
 508                     lval.write_cvalue(fx, res);
 509                 }
 510                 Rvalue::CheckedBinaryOp(bin_op, ref lhs_rhs) => {
 511                     let lhs = codegen_operand(fx, &lhs_rhs.0);
 512                     let rhs = codegen_operand(fx, &lhs_rhs.1);
 513
 514                     let res = if !fx.tcx.sess.overflow_checks() {
 515                         let val =
 516                             crate::num::codegen_int_binop(fx, bin_op, lhs, rhs).load_scalar(fx);
 517                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 518                         CValue::by_val_pair(val, is_overflow, lval.layout())
 519                     } else {
 520                         crate::num::codegen_checked_int_binop(fx, bin_op, lhs, rhs)
 521                     };
 522
 523                     lval.write_cvalue(fx, res);
 524                 }
 525                 Rvalue::UnaryOp(un_op, ref operand) => {
 526                     let operand = codegen_operand(fx, operand);
 527                     let layout = operand.layout();
 528                     let val = operand.load_scalar(fx);
 529                     let res = match un_op {
 530                         UnOp::Not => match layout.ty.kind() {
 531                             ty::Bool => {
 532                                 let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 533                                 CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 534                             }
 535                             ty::Uint(_) | ty::Int(_) => {
 536                                 CValue::by_val(fx.bcx.ins().bnot(val), layout)
 537                             }
 538                             _ => unreachable!("un op Not for {:?}", layout.ty),
 539                         },
 540                         UnOp::Neg => match layout.ty.kind() {
 541                             ty::Int(IntTy::I128) => {
 542                                 // FIXME remove this case once ineg.i128 works
 543                                 let zero =
 544                                     CValue::const_val(fx, layout, ty::ScalarInt::null(layout.size));
 545                                 crate::num::codegen_int_binop(fx, BinOp::Sub, zero, operand)
 546                             }
 547                             ty::Int(_) => CValue::by_val(fx.bcx.ins().ineg(val), layout),
 548                             ty::Float(_) => CValue::by_val(fx.bcx.ins().fneg(val), layout),
 549                             _ => unreachable!("un op Neg for {:?}", layout.ty),
 550                         },
 551                     };
 552                     lval.write_cvalue(fx, res);
 553                 }
 554                 Rvalue::Cast(
 555                     CastKind::Pointer(PointerCast::ReifyFnPointer),
 556                     ref operand,
 557                     to_ty,
 558                 ) => {
 559                     let from_ty = fx.monomorphize(operand.ty(&fx.mir.local_decls, fx.tcx));
 560                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 561                     match *from_ty.kind() {
 562                         ty::FnDef(def_id, substs) => {
 563                             let func_ref = fx.get_function_ref(
 564                                 Instance::resolve_for_fn_ptr(
 565                                     fx.tcx,
 566                                     ParamEnv::reveal_all(),
 567                                     def_id,
 568                                     substs,
 569                                 )
 570                                 .unwrap()
 571                                 .polymorphize(fx.tcx),
 572                             );
 573                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 574                             lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
 575                         }
 576                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
 577                     }
 578                 }
 579                 Rvalue::Cast(
 580                     CastKind::Pointer(PointerCast::UnsafeFnPointer),
 581                     ref operand,
 582                     to_ty,
 583                 )
 584                 | Rvalue::Cast(
 585                     CastKind::Pointer(PointerCast::MutToConstPointer),
 586                     ref operand,
 587                     to_ty,
 588                 )
 589                 | Rvalue::Cast(
 590                     CastKind::Pointer(PointerCast::ArrayToPointer),
 591                     ref operand,
 592                     to_ty,
 593                 ) => {
 594                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 595                     let operand = codegen_operand(fx, operand);
 596                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
 597                 }
 598                 Rvalue::Cast(CastKind::Misc, ref operand, to_ty) => {
 599                     let operand = codegen_operand(fx, operand);
 600                     let from_ty = operand.layout().ty;
 601                     let to_ty = fx.monomorphize(to_ty);
 602
 603                     fn is_fat_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
 604                         ty.builtin_deref(true)
 605                             .map(|ty::TypeAndMut { ty: pointee_ty, mutbl: _ }| {
 606                                 has_ptr_meta(fx.tcx, pointee_ty)
 607                             })
 608                             .unwrap_or(false)
 609                     }
 610
 611                     if is_fat_ptr(fx, from_ty) {
 612                         if is_fat_ptr(fx, to_ty) {
 613                             // fat-ptr -> fat-ptr
 614                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
 615                         } else {
 616                             // fat-ptr -> thin-ptr
 617                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 618                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 619                         }
 620                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind() {
 621                         // enum -> discriminant value
 622                         assert!(adt_def.is_enum());
 623                         match to_ty.kind() {
 624                             ty::Uint(_) | ty::Int(_) => {}
 625                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 626                         }
 627                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 628
 629                         let discriminant = crate::discriminant::codegen_get_discriminant(
 630                             fx,
 631                             operand,
 632                             fx.layout_of(operand.layout().ty.discriminant_ty(fx.tcx)),
 633                         )
 634                         .load_scalar(fx);
 635
 636                         let res = crate::cast::clif_intcast(
 637                             fx,
 638                             discriminant,
 639                             to_clif_ty,
 640                             to_ty.is_signed(),
 641                         );
 642                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 643                     } else {
 644                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 645                         let from = operand.load_scalar(fx);
 646
 647                         let res = clif_int_or_float_cast(
 648                             fx,
 649                             from,
 650                             type_sign(from_ty),
 651                             to_clif_ty,
 652                             type_sign(to_ty),
 653                         );
 654                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 655                     }
 656                 }
 657                 Rvalue::Cast(
 658                     CastKind::Pointer(PointerCast::ClosureFnPointer(_)),
 659                     ref operand,
 660                     _to_ty,
 661                 ) => {
 662                     let operand = codegen_operand(fx, operand);
 663                     match *operand.layout().ty.kind() {
 664                         ty::Closure(def_id, substs) => {
 665                             let instance = Instance::resolve_closure(
 666                                 fx.tcx,
 667                                 def_id,
 668                                 substs,
 669                                 ty::ClosureKind::FnOnce,
 670                             )
 671                             .polymorphize(fx.tcx);
 672                             let func_ref = fx.get_function_ref(instance);
 673                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 674                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 675                         }
 676                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 677                     }
 678                 }
 679                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), ref operand, _to_ty) => {
 680                     let operand = codegen_operand(fx, operand);
 681                     operand.unsize_value(fx, lval);
 682                 }
 683                 Rvalue::Discriminant(place) => {
 684                     let place = codegen_place(fx, place);
 685                     let value = place.to_cvalue(fx);
 686                     let discr =
 687                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 688                     lval.write_cvalue(fx, discr);
 689                 }
 690                 Rvalue::Repeat(ref operand, times) => {
 691                     let operand = codegen_operand(fx, operand);
 692                     let times = fx
 693                         .monomorphize(times)
 694                         .eval(fx.tcx, ParamEnv::reveal_all())
 695                         .val()
 696                         .try_to_bits(fx.tcx.data_layout.pointer_size)
 697                         .unwrap();
 698                     if operand.layout().size.bytes() == 0 {
 699                         // Do nothing for ZST's
 700                     } else if fx.clif_type(operand.layout().ty) == Some(types::I8) {
 701                         let times = fx.bcx.ins().iconst(fx.pointer_type, times as i64);
 702                         // FIXME use emit_small_memset where possible
 703                         let addr = lval.to_ptr().get_addr(fx);
 704                         let val = operand.load_scalar(fx);
 705                         fx.bcx.call_memset(fx.target_config, addr, val, times);
 706                     } else {
 707                         let loop_block = fx.bcx.create_block();
 708                         let loop_block2 = fx.bcx.create_block();
 709                         let done_block = fx.bcx.create_block();
 710                         let index = fx.bcx.append_block_param(loop_block, fx.pointer_type);
 711                         let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
 712                         fx.bcx.ins().jump(loop_block, &[zero]);
 713
 714                         fx.bcx.switch_to_block(loop_block);
 715                         let done = fx.bcx.ins().icmp_imm(IntCC::Equal, index, times as i64);
 716                         fx.bcx.ins().brnz(done, done_block, &[]);
 717                         fx.bcx.ins().jump(loop_block2, &[]);
 718
 719                         fx.bcx.switch_to_block(loop_block2);
 720                         let to = lval.place_index(fx, index);
 721                         to.write_cvalue(fx, operand);
 722                         let index = fx.bcx.ins().iadd_imm(index, 1);
 723                         fx.bcx.ins().jump(loop_block, &[index]);
 724
 725                         fx.bcx.switch_to_block(done_block);
 726                         fx.bcx.ins().nop();
 727                     }
 728                 }
 729                 Rvalue::Len(place) => {
 730                     let place = codegen_place(fx, place);
 731                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 732                     let len = codegen_array_len(fx, place);
 733                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 734                 }
 735                 Rvalue::ShallowInitBox(ref operand, content_ty) => {
 736                     let content_ty = fx.monomorphize(content_ty);
 737                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 738                     let operand = codegen_operand(fx, operand);
 739                     let operand = operand.load_scalar(fx);
 740                     lval.write_cvalue(fx, CValue::by_val(operand, box_layout));
 741                 }
 742                 Rvalue::NullaryOp(null_op, ty) => {
 743                     assert!(
 744                         lval.layout()
 745                             .ty
 746                             .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all())
 747                     );
 748                     let layout = fx.layout_of(fx.monomorphize(ty));
 749                     let val = match null_op {
 750                         NullOp::SizeOf => layout.size.bytes(),
 751                         NullOp::AlignOf => layout.align.abi.bytes(),
 752                     };
 753                     let val = CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), val.into());
 754                     lval.write_cvalue(fx, val);
 755                 }
 756                 Rvalue::Aggregate(ref kind, ref operands) => match kind.as_ref() {
 757                     AggregateKind::Array(_ty) => {
 758                         for (i, operand) in operands.iter().enumerate() {
 759                             let operand = codegen_operand(fx, operand);
 760                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 761                             let to = lval.place_index(fx, index);
 762                             to.write_cvalue(fx, operand);
 763                         }
 764                     }
 765                     _ => unreachable!("shouldn't exist at codegen {:?}", to_place_and_rval.1),
 766                 },
 767             }
 768         }
 769         StatementKind::StorageLive(_)
 770         | StatementKind::StorageDead(_)
 771         | StatementKind::Nop
 772         | StatementKind::FakeRead(..)
 773         | StatementKind::Retag { .. }
 774         | StatementKind::AscribeUserType(..) => {}
 775
 776         StatementKind::Coverage { .. } => fx.tcx.sess.fatal("-Zcoverage is unimplemented"),
 777         StatementKind::CopyNonOverlapping(inner) => {
 778             let dst = codegen_operand(fx, &inner.dst);
 779             let pointee = dst
 780                 .layout()
 781                 .pointee_info_at(fx, rustc_target::abi::Size::ZERO)
 782                 .expect("Expected pointer");
 783             let dst = dst.load_scalar(fx);
 784             let src = codegen_operand(fx, &inner.src).load_scalar(fx);
 785             let count = codegen_operand(fx, &inner.count).load_scalar(fx);
 786             let elem_size: u64 = pointee.size.bytes();
 787             let bytes =
 788                 if elem_size != 1 { fx.bcx.ins().imul_imm(count, elem_size as i64) } else { count };
 789             fx.bcx.call_memcpy(fx.target_config, dst, src, bytes);
 790         }
 791     }
 792 }
 793
 794 fn codegen_array_len<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, place: CPlace<'tcx>) -> Value {
 795     match *place.layout().ty.kind() {
 796         ty::Array(_elem_ty, len) => {
 797             let len = fx.monomorphize(len).eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 798             fx.bcx.ins().iconst(fx.pointer_type, len)
 799         }
 800         ty::Slice(_elem_ty) => {
 801             place.to_ptr_maybe_unsized().1.expect("Length metadata for slice place")
 802         }
 803         _ => bug!("Rvalue::Len({:?})", place),
 804     }
 805 }
 806
 807 pub(crate) fn codegen_place<'tcx>(
 808     fx: &mut FunctionCx<'_, '_, 'tcx>,
 809     place: Place<'tcx>,
 810 ) -> CPlace<'tcx> {
 811     let mut cplace = fx.get_local_place(place.local);
 812
 813     for elem in place.projection {
 814         match elem {
 815             PlaceElem::Deref => {
 816                 cplace = cplace.place_deref(fx);
 817             }
 818             PlaceElem::Field(field, _ty) => {
 819                 cplace = cplace.place_field(fx, field);
 820             }
 821             PlaceElem::Index(local) => {
 822                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 823                 cplace = cplace.place_index(fx, index);
 824             }
 825             PlaceElem::ConstantIndex { offset, min_length: _, from_end } => {
 826                 let offset: u64 = offset;
 827                 let index = if !from_end {
 828                     fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 829                 } else {
 830                     let len = codegen_array_len(fx, cplace);
 831                     fx.bcx.ins().iadd_imm(len, -(offset as i64))
 832                 };
 833                 cplace = cplace.place_index(fx, index);
 834             }
 835             PlaceElem::Subslice { from, to, from_end } => {
 836                 // These indices are generated by slice patterns.
 837                 // slice[from:-to] in Python terms.
 838
 839                 let from: u64 = from;
 840                 let to: u64 = to;
 841
 842                 match cplace.layout().ty.kind() {
 843                     ty::Array(elem_ty, _len) => {
 844                         assert!(!from_end, "array subslices are never `from_end`");
 845                         let elem_layout = fx.layout_of(*elem_ty);
 846                         let ptr = cplace.to_ptr();
 847                         cplace = CPlace::for_ptr(
 848                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
 849                             fx.layout_of(fx.tcx.mk_array(*elem_ty, to - from)),
 850                         );
 851                     }
 852                     ty::Slice(elem_ty) => {
 853                         assert!(from_end, "slice subslices should be `from_end`");
 854                         let elem_layout = fx.layout_of(*elem_ty);
 855                         let (ptr, len) = cplace.to_ptr_maybe_unsized();
 856                         let len = len.unwrap();
 857                         cplace = CPlace::for_ptr_with_extra(
 858                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
 859                             fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
 860                             cplace.layout(),
 861                         );
 862                     }
 863                     _ => unreachable!(),
 864                 }
 865             }
 866             PlaceElem::Downcast(_adt_def, variant) => {
 867                 cplace = cplace.downcast_variant(fx, variant);
 868             }
 869         }
 870     }
 871
 872     cplace
 873 }
 874
 875 pub(crate) fn codegen_operand<'tcx>(
 876     fx: &mut FunctionCx<'_, '_, 'tcx>,
 877     operand: &Operand<'tcx>,
 878 ) -> CValue<'tcx> {
 879     match operand {
 880         Operand::Move(place) | Operand::Copy(place) => {
 881             let cplace = codegen_place(fx, *place);
 882             cplace.to_cvalue(fx)
 883         }
 884         Operand::Constant(const_) => crate::constant::codegen_constant(fx, const_),
 885     }
 886 }
 887
 888 pub(crate) fn codegen_panic<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, msg_str: &str, span: Span) {
 889     let location = fx.get_caller_location(span).load_scalar(fx);
 890
 891     let msg_ptr = fx.anonymous_str(msg_str);
 892     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
 893     let args = [msg_ptr, msg_len, location];
 894
 895     codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, span);
 896 }
 897
 898 pub(crate) fn codegen_panic_inner<'tcx>(
 899     fx: &mut FunctionCx<'_, '_, 'tcx>,
 900     lang_item: rustc_hir::LangItem,
 901     args: &[Value],
 902     span: Span,
 903 ) {
 904     let def_id =
 905         fx.tcx.lang_items().require(lang_item).unwrap_or_else(|s| fx.tcx.sess.span_fatal(span, &s));
 906
 907     let instance = Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
 908     let symbol_name = fx.tcx.symbol_name(instance).name;
 909
 910     fx.lib_call(
 911         &*symbol_name,
 912         vec![
 913             AbiParam::new(fx.pointer_type),
 914             AbiParam::new(fx.pointer_type),
 915             AbiParam::new(fx.pointer_type),
 916         ],
 917         vec![],
 918         args,
 919     );
 920
 921     crate::trap::trap_unreachable(fx, "panic lang item returned");
 922 }