src/base.rs

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