src/base.rs

   1 //! Codegen of a single function
   2
   3 use cranelift_codegen::binemit::{NullStackMapSink, NullTrapSink};
   4 use rustc_index::vec::IndexVec;
   5 use rustc_middle::ty::adjustment::PointerCast;
   6 use rustc_middle::ty::layout::FnAbiExt;
   7 use rustc_target::abi::call::FnAbi;
   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_mir::util::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 pointer_type = module.target_config().pointer_type();
  53     let clif_comments = crate::pretty_clif::CommentWriter::new(tcx, instance);
  54
  55     let mut fx = FunctionCx {
  56         cx,
  57         module,
  58         tcx,
  59         pointer_type,
  60         constants_cx: ConstantCx::new(),
  61
  62         instance,
  63         symbol_name,
  64         mir,
  65         fn_abi: Some(FnAbi::of_instance(&RevealAllLayoutCx(tcx), instance, &[])),
  66
  67         bcx,
  68         block_map,
  69         local_map: IndexVec::with_capacity(mir.local_decls.len()),
  70         caller_location: None, // set by `codegen_fn_prelude`
  71
  72         clif_comments,
  73         source_info_set: indexmap::IndexSet::new(),
  74         next_ssa_var: 0,
  75
  76         inline_asm_index: 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                     None,
 208                     Some(Box::new(writer)),
 209                     err,
 210                 );
 211                 tcx.sess.fatal(&format!("cranelift verify error:\n{}", pretty_error));
 212             }
 213         }
 214     });
 215 }
 216
 217 fn codegen_fn_content(fx: &mut FunctionCx<'_, '_, '_>) {
 218     for (bb, bb_data) in fx.mir.basic_blocks().iter_enumerated() {
 219         let block = fx.get_block(bb);
 220         fx.bcx.switch_to_block(block);
 221
 222         if bb_data.is_cleanup {
 223             // Unwinding after panicking is not supported
 224             continue;
 225
 226             // FIXME Once unwinding is supported and Cranelift supports marking blocks as cold, do
 227             // so for cleanup blocks.
 228         }
 229
 230         fx.bcx.ins().nop();
 231         for stmt in &bb_data.statements {
 232             fx.set_debug_loc(stmt.source_info);
 233             codegen_stmt(fx, block, stmt);
 234         }
 235
 236         if fx.clif_comments.enabled() {
 237             let mut terminator_head = "\n".to_string();
 238             bb_data.terminator().kind.fmt_head(&mut terminator_head).unwrap();
 239             let inst = fx.bcx.func.layout.last_inst(block).unwrap();
 240             fx.add_comment(inst, terminator_head);
 241         }
 242
 243         fx.set_debug_loc(bb_data.terminator().source_info);
 244
 245         match &bb_data.terminator().kind {
 246             TerminatorKind::Goto { target } => {
 247                 if let TerminatorKind::Return = fx.mir[*target].terminator().kind {
 248                     let mut can_immediately_return = true;
 249                     for stmt in &fx.mir[*target].statements {
 250                         if let StatementKind::StorageDead(_) = stmt.kind {
 251                         } else {
 252                             // FIXME Can sometimes happen, see rust-lang/rust#70531
 253                             can_immediately_return = false;
 254                             break;
 255                         }
 256                     }
 257
 258                     if can_immediately_return {
 259                         crate::abi::codegen_return(fx);
 260                         continue;
 261                     }
 262                 }
 263
 264                 let block = fx.get_block(*target);
 265                 fx.bcx.ins().jump(block, &[]);
 266             }
 267             TerminatorKind::Return => {
 268                 crate::abi::codegen_return(fx);
 269             }
 270             TerminatorKind::Assert { 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
 299                             .get_caller_location(bb_data.terminator().source_info.span)
 300                             .load_scalar(fx);
 301
 302                         codegen_panic_inner(
 303                             fx,
 304                             rustc_hir::LangItem::PanicBoundsCheck,
 305                             &[index, len, location],
 306                             bb_data.terminator().source_info.span,
 307                         );
 308                     }
 309                     _ => {
 310                         let msg_str = msg.description();
 311                         codegen_panic(fx, msg_str, bb_data.terminator().source_info.span);
 312                     }
 313                 }
 314             }
 315
 316             TerminatorKind::SwitchInt { discr, switch_ty, targets } => {
 317                 let discr = codegen_operand(fx, discr).load_scalar(fx);
 318
 319                 let use_bool_opt = switch_ty.kind() == fx.tcx.types.bool.kind()
 320                     || (targets.iter().count() == 1 && targets.iter().next().unwrap().0 == 0);
 321                 if use_bool_opt {
 322                     assert_eq!(targets.iter().count(), 1);
 323                     let (then_value, then_block) = targets.iter().next().unwrap();
 324                     let then_block = fx.get_block(then_block);
 325                     let else_block = fx.get_block(targets.otherwise());
 326                     let test_zero = match then_value {
 327                         0 => true,
 328                         1 => false,
 329                         _ => unreachable!("{:?}", targets),
 330                     };
 331
 332                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 333                     let (discr, is_inverted) =
 334                         crate::optimize::peephole::maybe_unwrap_bool_not(&mut fx.bcx, discr);
 335                     let test_zero = if is_inverted { !test_zero } else { test_zero };
 336                     let discr = crate::optimize::peephole::maybe_unwrap_bint(&mut fx.bcx, discr);
 337                     if let Some(taken) = crate::optimize::peephole::maybe_known_branch_taken(
 338                         &fx.bcx, discr, test_zero,
 339                     ) {
 340                         if taken {
 341                             fx.bcx.ins().jump(then_block, &[]);
 342                         } else {
 343                             fx.bcx.ins().jump(else_block, &[]);
 344                         }
 345                     } else {
 346                         if test_zero {
 347                             fx.bcx.ins().brz(discr, then_block, &[]);
 348                             fx.bcx.ins().jump(else_block, &[]);
 349                         } else {
 350                             fx.bcx.ins().brnz(discr, then_block, &[]);
 351                             fx.bcx.ins().jump(else_block, &[]);
 352                         }
 353                     }
 354                 } else {
 355                     let mut switch = ::cranelift_frontend::Switch::new();
 356                     for (value, block) in targets.iter() {
 357                         let block = fx.get_block(block);
 358                         switch.set_entry(value, block);
 359                     }
 360                     let otherwise_block = fx.get_block(targets.otherwise());
 361                     switch.emit(&mut fx.bcx, discr, otherwise_block);
 362                 }
 363             }
 364             TerminatorKind::Call {
 365                 func,
 366                 args,
 367                 destination,
 368                 fn_span,
 369                 cleanup: _,
 370                 from_hir_call: _,
 371             } => {
 372                 fx.tcx.sess.time("codegen call", || {
 373                     crate::abi::codegen_terminator_call(fx, *fn_span, func, args, *destination)
 374                 });
 375             }
 376             TerminatorKind::InlineAsm {
 377                 template,
 378                 operands,
 379                 options,
 380                 destination,
 381                 line_spans: _,
 382             } => {
 383                 crate::inline_asm::codegen_inline_asm(
 384                     fx,
 385                     bb_data.terminator().source_info.span,
 386                     template,
 387                     operands,
 388                     *options,
 389                 );
 390
 391                 match *destination {
 392                     Some(destination) => {
 393                         let destination_block = fx.get_block(destination);
 394                         fx.bcx.ins().jump(destination_block, &[]);
 395                     }
 396                     None => {
 397                         crate::trap::trap_unreachable(
 398                             fx,
 399                             "[corruption] Returned from noreturn inline asm",
 400                         );
 401                     }
 402                 }
 403             }
 404             TerminatorKind::Resume | TerminatorKind::Abort => {
 405                 trap_unreachable(fx, "[corruption] Unwinding bb reached.");
 406             }
 407             TerminatorKind::Unreachable => {
 408                 trap_unreachable(fx, "[corruption] Hit unreachable code.");
 409             }
 410             TerminatorKind::Yield { .. }
 411             | TerminatorKind::FalseEdge { .. }
 412             | TerminatorKind::FalseUnwind { .. }
 413             | TerminatorKind::DropAndReplace { .. }
 414             | TerminatorKind::GeneratorDrop => {
 415                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
 416             }
 417             TerminatorKind::Drop { place, target, unwind: _ } => {
 418                 let drop_place = codegen_place(fx, *place);
 419                 crate::abi::codegen_drop(fx, bb_data.terminator().source_info.span, drop_place);
 420
 421                 let target_block = fx.get_block(*target);
 422                 fx.bcx.ins().jump(target_block, &[]);
 423             }
 424         };
 425     }
 426
 427     fx.bcx.seal_all_blocks();
 428     fx.bcx.finalize();
 429 }
 430
 431 fn codegen_stmt<'tcx>(
 432     fx: &mut FunctionCx<'_, '_, 'tcx>,
 433     #[allow(unused_variables)] cur_block: Block,
 434     stmt: &Statement<'tcx>,
 435 ) {
 436     let _print_guard = crate::PrintOnPanic(|| format!("stmt {:?}", stmt));
 437
 438     fx.set_debug_loc(stmt.source_info);
 439
 440     #[cfg(disabled)]
 441     match &stmt.kind {
 442         StatementKind::StorageLive(..) | StatementKind::StorageDead(..) => {} // Those are not very useful
 443         _ => {
 444             if fx.clif_comments.enabled() {
 445                 let inst = fx.bcx.func.layout.last_inst(cur_block).unwrap();
 446                 fx.add_comment(inst, format!("{:?}", stmt));
 447             }
 448         }
 449     }
 450
 451     match &stmt.kind {
 452         StatementKind::SetDiscriminant { place, variant_index } => {
 453             let place = codegen_place(fx, **place);
 454             crate::discriminant::codegen_set_discriminant(fx, place, *variant_index);
 455         }
 456         StatementKind::Assign(to_place_and_rval) => {
 457             let lval = codegen_place(fx, to_place_and_rval.0);
 458             let dest_layout = lval.layout();
 459             match to_place_and_rval.1 {
 460                 Rvalue::Use(ref operand) => {
 461                     let val = codegen_operand(fx, operand);
 462                     lval.write_cvalue(fx, val);
 463                 }
 464                 Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
 465                     let place = codegen_place(fx, place);
 466                     let ref_ = place.place_ref(fx, lval.layout());
 467                     lval.write_cvalue(fx, ref_);
 468                 }
 469                 Rvalue::ThreadLocalRef(def_id) => {
 470                     let val = crate::constant::codegen_tls_ref(fx, def_id, lval.layout());
 471                     lval.write_cvalue(fx, val);
 472                 }
 473                 Rvalue::BinaryOp(bin_op, ref lhs_rhs) => {
 474                     let lhs = codegen_operand(fx, &lhs_rhs.0);
 475                     let rhs = codegen_operand(fx, &lhs_rhs.1);
 476
 477                     let res = crate::num::codegen_binop(fx, bin_op, lhs, rhs);
 478                     lval.write_cvalue(fx, res);
 479                 }
 480                 Rvalue::CheckedBinaryOp(bin_op, ref lhs_rhs) => {
 481                     let lhs = codegen_operand(fx, &lhs_rhs.0);
 482                     let rhs = codegen_operand(fx, &lhs_rhs.1);
 483
 484                     let res = if !fx.tcx.sess.overflow_checks() {
 485                         let val =
 486                             crate::num::codegen_int_binop(fx, bin_op, lhs, rhs).load_scalar(fx);
 487                         let is_overflow = fx.bcx.ins().iconst(types::I8, 0);
 488                         CValue::by_val_pair(val, is_overflow, lval.layout())
 489                     } else {
 490                         crate::num::codegen_checked_int_binop(fx, bin_op, lhs, rhs)
 491                     };
 492
 493                     lval.write_cvalue(fx, res);
 494                 }
 495                 Rvalue::UnaryOp(un_op, ref operand) => {
 496                     let operand = codegen_operand(fx, operand);
 497                     let layout = operand.layout();
 498                     let val = operand.load_scalar(fx);
 499                     let res = match un_op {
 500                         UnOp::Not => match layout.ty.kind() {
 501                             ty::Bool => {
 502                                 let res = fx.bcx.ins().icmp_imm(IntCC::Equal, val, 0);
 503                                 CValue::by_val(fx.bcx.ins().bint(types::I8, res), layout)
 504                             }
 505                             ty::Uint(_) | ty::Int(_) => {
 506                                 CValue::by_val(fx.bcx.ins().bnot(val), layout)
 507                             }
 508                             _ => unreachable!("un op Not for {:?}", layout.ty),
 509                         },
 510                         UnOp::Neg => match layout.ty.kind() {
 511                             ty::Int(IntTy::I128) => {
 512                                 // FIXME remove this case once ineg.i128 works
 513                                 let zero =
 514                                     CValue::const_val(fx, layout, ty::ScalarInt::null(layout.size));
 515                                 crate::num::codegen_int_binop(fx, BinOp::Sub, zero, operand)
 516                             }
 517                             ty::Int(_) => CValue::by_val(fx.bcx.ins().ineg(val), layout),
 518                             ty::Float(_) => CValue::by_val(fx.bcx.ins().fneg(val), layout),
 519                             _ => unreachable!("un op Neg for {:?}", layout.ty),
 520                         },
 521                     };
 522                     lval.write_cvalue(fx, res);
 523                 }
 524                 Rvalue::Cast(
 525                     CastKind::Pointer(PointerCast::ReifyFnPointer),
 526                     ref operand,
 527                     to_ty,
 528                 ) => {
 529                     let from_ty = fx.monomorphize(operand.ty(&fx.mir.local_decls, fx.tcx));
 530                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 531                     match *from_ty.kind() {
 532                         ty::FnDef(def_id, substs) => {
 533                             let func_ref = fx.get_function_ref(
 534                                 Instance::resolve_for_fn_ptr(
 535                                     fx.tcx,
 536                                     ParamEnv::reveal_all(),
 537                                     def_id,
 538                                     substs,
 539                                 )
 540                                 .unwrap()
 541                                 .polymorphize(fx.tcx),
 542                             );
 543                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 544                             lval.write_cvalue(fx, CValue::by_val(func_addr, to_layout));
 545                         }
 546                         _ => bug!("Trying to ReifyFnPointer on non FnDef {:?}", from_ty),
 547                     }
 548                 }
 549                 Rvalue::Cast(
 550                     CastKind::Pointer(PointerCast::UnsafeFnPointer),
 551                     ref operand,
 552                     to_ty,
 553                 )
 554                 | Rvalue::Cast(
 555                     CastKind::Pointer(PointerCast::MutToConstPointer),
 556                     ref operand,
 557                     to_ty,
 558                 )
 559                 | Rvalue::Cast(
 560                     CastKind::Pointer(PointerCast::ArrayToPointer),
 561                     ref operand,
 562                     to_ty,
 563                 ) => {
 564                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
 565                     let operand = codegen_operand(fx, operand);
 566                     lval.write_cvalue(fx, operand.cast_pointer_to(to_layout));
 567                 }
 568                 Rvalue::Cast(CastKind::Misc, ref operand, to_ty) => {
 569                     let operand = codegen_operand(fx, operand);
 570                     let from_ty = operand.layout().ty;
 571                     let to_ty = fx.monomorphize(to_ty);
 572
 573                     fn is_fat_ptr<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> bool {
 574                         ty.builtin_deref(true)
 575                             .map(|ty::TypeAndMut { ty: pointee_ty, mutbl: _ }| {
 576                                 has_ptr_meta(fx.tcx, pointee_ty)
 577                             })
 578                             .unwrap_or(false)
 579                     }
 580
 581                     if is_fat_ptr(fx, from_ty) {
 582                         if is_fat_ptr(fx, to_ty) {
 583                             // fat-ptr -> fat-ptr
 584                             lval.write_cvalue(fx, operand.cast_pointer_to(dest_layout));
 585                         } else {
 586                             // fat-ptr -> thin-ptr
 587                             let (ptr, _extra) = operand.load_scalar_pair(fx);
 588                             lval.write_cvalue(fx, CValue::by_val(ptr, dest_layout))
 589                         }
 590                     } else if let ty::Adt(adt_def, _substs) = from_ty.kind() {
 591                         // enum -> discriminant value
 592                         assert!(adt_def.is_enum());
 593                         match to_ty.kind() {
 594                             ty::Uint(_) | ty::Int(_) => {}
 595                             _ => unreachable!("cast adt {} -> {}", from_ty, to_ty),
 596                         }
 597                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 598
 599                         let discriminant = crate::discriminant::codegen_get_discriminant(
 600                             fx,
 601                             operand,
 602                             fx.layout_of(operand.layout().ty.discriminant_ty(fx.tcx)),
 603                         )
 604                         .load_scalar(fx);
 605
 606                         let res = crate::cast::clif_intcast(
 607                             fx,
 608                             discriminant,
 609                             to_clif_ty,
 610                             to_ty.is_signed(),
 611                         );
 612                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 613                     } else {
 614                         let to_clif_ty = fx.clif_type(to_ty).unwrap();
 615                         let from = operand.load_scalar(fx);
 616
 617                         let res = clif_int_or_float_cast(
 618                             fx,
 619                             from,
 620                             type_sign(from_ty),
 621                             to_clif_ty,
 622                             type_sign(to_ty),
 623                         );
 624                         lval.write_cvalue(fx, CValue::by_val(res, dest_layout));
 625                     }
 626                 }
 627                 Rvalue::Cast(
 628                     CastKind::Pointer(PointerCast::ClosureFnPointer(_)),
 629                     ref operand,
 630                     _to_ty,
 631                 ) => {
 632                     let operand = codegen_operand(fx, operand);
 633                     match *operand.layout().ty.kind() {
 634                         ty::Closure(def_id, substs) => {
 635                             let instance = Instance::resolve_closure(
 636                                 fx.tcx,
 637                                 def_id,
 638                                 substs,
 639                                 ty::ClosureKind::FnOnce,
 640                             )
 641                             .polymorphize(fx.tcx);
 642                             let func_ref = fx.get_function_ref(instance);
 643                             let func_addr = fx.bcx.ins().func_addr(fx.pointer_type, func_ref);
 644                             lval.write_cvalue(fx, CValue::by_val(func_addr, lval.layout()));
 645                         }
 646                         _ => bug!("{} cannot be cast to a fn ptr", operand.layout().ty),
 647                     }
 648                 }
 649                 Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), ref operand, _to_ty) => {
 650                     let operand = codegen_operand(fx, operand);
 651                     operand.unsize_value(fx, lval);
 652                 }
 653                 Rvalue::Discriminant(place) => {
 654                     let place = codegen_place(fx, place);
 655                     let value = place.to_cvalue(fx);
 656                     let discr =
 657                         crate::discriminant::codegen_get_discriminant(fx, value, dest_layout);
 658                     lval.write_cvalue(fx, discr);
 659                 }
 660                 Rvalue::Repeat(ref operand, times) => {
 661                     let operand = codegen_operand(fx, operand);
 662                     let times = fx
 663                         .monomorphize(times)
 664                         .eval(fx.tcx, ParamEnv::reveal_all())
 665                         .val
 666                         .try_to_bits(fx.tcx.data_layout.pointer_size)
 667                         .unwrap();
 668                     if operand.layout().size.bytes() == 0 {
 669                         // Do nothing for ZST's
 670                     } else if fx.clif_type(operand.layout().ty) == Some(types::I8) {
 671                         let times = fx.bcx.ins().iconst(fx.pointer_type, times as i64);
 672                         // FIXME use emit_small_memset where possible
 673                         let addr = lval.to_ptr().get_addr(fx);
 674                         let val = operand.load_scalar(fx);
 675                         fx.bcx.call_memset(fx.module.target_config(), addr, val, times);
 676                     } else {
 677                         let loop_block = fx.bcx.create_block();
 678                         let loop_block2 = fx.bcx.create_block();
 679                         let done_block = fx.bcx.create_block();
 680                         let index = fx.bcx.append_block_param(loop_block, fx.pointer_type);
 681                         let zero = fx.bcx.ins().iconst(fx.pointer_type, 0);
 682                         fx.bcx.ins().jump(loop_block, &[zero]);
 683
 684                         fx.bcx.switch_to_block(loop_block);
 685                         let done = fx.bcx.ins().icmp_imm(IntCC::Equal, index, times as i64);
 686                         fx.bcx.ins().brnz(done, done_block, &[]);
 687                         fx.bcx.ins().jump(loop_block2, &[]);
 688
 689                         fx.bcx.switch_to_block(loop_block2);
 690                         let to = lval.place_index(fx, index);
 691                         to.write_cvalue(fx, operand);
 692                         let index = fx.bcx.ins().iadd_imm(index, 1);
 693                         fx.bcx.ins().jump(loop_block, &[index]);
 694
 695                         fx.bcx.switch_to_block(done_block);
 696                         fx.bcx.ins().nop();
 697                     }
 698                 }
 699                 Rvalue::Len(place) => {
 700                     let place = codegen_place(fx, place);
 701                     let usize_layout = fx.layout_of(fx.tcx.types.usize);
 702                     let len = codegen_array_len(fx, place);
 703                     lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
 704                 }
 705                 Rvalue::NullaryOp(NullOp::Box, content_ty) => {
 706                     let usize_type = fx.clif_type(fx.tcx.types.usize).unwrap();
 707                     let content_ty = fx.monomorphize(content_ty);
 708                     let layout = fx.layout_of(content_ty);
 709                     let llsize = fx.bcx.ins().iconst(usize_type, layout.size.bytes() as i64);
 710                     let llalign = fx.bcx.ins().iconst(usize_type, layout.align.abi.bytes() as i64);
 711                     let box_layout = fx.layout_of(fx.tcx.mk_box(content_ty));
 712
 713                     // Allocate space:
 714                     let def_id =
 715                         match fx.tcx.lang_items().require(rustc_hir::LangItem::ExchangeMalloc) {
 716                             Ok(id) => id,
 717                             Err(s) => {
 718                                 fx.tcx
 719                                     .sess
 720                                     .fatal(&format!("allocation of `{}` {}", box_layout.ty, s));
 721                             }
 722                         };
 723                     let instance = ty::Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
 724                     let func_ref = fx.get_function_ref(instance);
 725                     let call = fx.bcx.ins().call(func_ref, &[llsize, llalign]);
 726                     let ptr = fx.bcx.inst_results(call)[0];
 727                     lval.write_cvalue(fx, CValue::by_val(ptr, box_layout));
 728                 }
 729                 Rvalue::NullaryOp(NullOp::SizeOf, ty) => {
 730                     assert!(
 731                         lval.layout()
 732                             .ty
 733                             .is_sized(fx.tcx.at(stmt.source_info.span), ParamEnv::reveal_all())
 734                     );
 735                     let ty_size = fx.layout_of(fx.monomorphize(ty)).size.bytes();
 736                     let val =
 737                         CValue::const_val(fx, fx.layout_of(fx.tcx.types.usize), ty_size.into());
 738                     lval.write_cvalue(fx, val);
 739                 }
 740                 Rvalue::Aggregate(ref kind, ref operands) => match kind.as_ref() {
 741                     AggregateKind::Array(_ty) => {
 742                         for (i, operand) in operands.iter().enumerate() {
 743                             let operand = codegen_operand(fx, operand);
 744                             let index = fx.bcx.ins().iconst(fx.pointer_type, i as i64);
 745                             let to = lval.place_index(fx, index);
 746                             to.write_cvalue(fx, operand);
 747                         }
 748                     }
 749                     _ => unreachable!("shouldn't exist at codegen {:?}", to_place_and_rval.1),
 750                 },
 751             }
 752         }
 753         StatementKind::StorageLive(_)
 754         | StatementKind::StorageDead(_)
 755         | StatementKind::Nop
 756         | StatementKind::FakeRead(..)
 757         | StatementKind::Retag { .. }
 758         | StatementKind::AscribeUserType(..) => {}
 759
 760         StatementKind::LlvmInlineAsm(asm) => {
 761             match asm.asm.asm.as_str().trim() {
 762                 "" => {
 763                     // Black box
 764                 }
 765                 _ => fx.tcx.sess.span_fatal(
 766                     stmt.source_info.span,
 767                     "Legacy `llvm_asm!` inline assembly is not supported. \
 768                     Try using the new `asm!` instead.",
 769                 ),
 770             }
 771         }
 772         StatementKind::Coverage { .. } => fx.tcx.sess.fatal("-Zcoverage is unimplemented"),
 773         StatementKind::CopyNonOverlapping(inner) => {
 774             let dst = codegen_operand(fx, &inner.dst);
 775             let pointee = dst
 776                 .layout()
 777                 .pointee_info_at(fx, rustc_target::abi::Size::ZERO)
 778                 .expect("Expected pointer");
 779             let dst = dst.load_scalar(fx);
 780             let src = codegen_operand(fx, &inner.src).load_scalar(fx);
 781             let count = codegen_operand(fx, &inner.count).load_scalar(fx);
 782             let elem_size: u64 = pointee.size.bytes();
 783             let bytes =
 784                 if elem_size != 1 { fx.bcx.ins().imul_imm(count, elem_size as i64) } else { count };
 785             fx.bcx.call_memcpy(fx.module.target_config(), dst, src, bytes);
 786         }
 787     }
 788 }
 789
 790 fn codegen_array_len<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, place: CPlace<'tcx>) -> Value {
 791     match *place.layout().ty.kind() {
 792         ty::Array(_elem_ty, len) => {
 793             let len = fx.monomorphize(len).eval_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
 794             fx.bcx.ins().iconst(fx.pointer_type, len)
 795         }
 796         ty::Slice(_elem_ty) => {
 797             place.to_ptr_maybe_unsized().1.expect("Length metadata for slice place")
 798         }
 799         _ => bug!("Rvalue::Len({:?})", place),
 800     }
 801 }
 802
 803 pub(crate) fn codegen_place<'tcx>(
 804     fx: &mut FunctionCx<'_, '_, 'tcx>,
 805     place: Place<'tcx>,
 806 ) -> CPlace<'tcx> {
 807     let mut cplace = fx.get_local_place(place.local);
 808
 809     for elem in place.projection {
 810         match elem {
 811             PlaceElem::Deref => {
 812                 cplace = cplace.place_deref(fx);
 813             }
 814             PlaceElem::Field(field, _ty) => {
 815                 cplace = cplace.place_field(fx, field);
 816             }
 817             PlaceElem::Index(local) => {
 818                 let index = fx.get_local_place(local).to_cvalue(fx).load_scalar(fx);
 819                 cplace = cplace.place_index(fx, index);
 820             }
 821             PlaceElem::ConstantIndex { offset, min_length: _, from_end } => {
 822                 let offset: u64 = offset;
 823                 let index = if !from_end {
 824                     fx.bcx.ins().iconst(fx.pointer_type, offset as i64)
 825                 } else {
 826                     let len = codegen_array_len(fx, cplace);
 827                     fx.bcx.ins().iadd_imm(len, -(offset as i64))
 828                 };
 829                 cplace = cplace.place_index(fx, index);
 830             }
 831             PlaceElem::Subslice { from, to, from_end } => {
 832                 // These indices are generated by slice patterns.
 833                 // slice[from:-to] in Python terms.
 834
 835                 let from: u64 = from;
 836                 let to: u64 = to;
 837
 838                 match cplace.layout().ty.kind() {
 839                     ty::Array(elem_ty, _len) => {
 840                         assert!(!from_end, "array subslices are never `from_end`");
 841                         let elem_layout = fx.layout_of(elem_ty);
 842                         let ptr = cplace.to_ptr();
 843                         cplace = CPlace::for_ptr(
 844                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
 845                             fx.layout_of(fx.tcx.mk_array(elem_ty, to - from)),
 846                         );
 847                     }
 848                     ty::Slice(elem_ty) => {
 849                         assert!(from_end, "slice subslices should be `from_end`");
 850                         let elem_layout = fx.layout_of(elem_ty);
 851                         let (ptr, len) = cplace.to_ptr_maybe_unsized();
 852                         let len = len.unwrap();
 853                         cplace = CPlace::for_ptr_with_extra(
 854                             ptr.offset_i64(fx, elem_layout.size.bytes() as i64 * (from as i64)),
 855                             fx.bcx.ins().iadd_imm(len, -(from as i64 + to as i64)),
 856                             cplace.layout(),
 857                         );
 858                     }
 859                     _ => unreachable!(),
 860                 }
 861             }
 862             PlaceElem::Downcast(_adt_def, variant) => {
 863                 cplace = cplace.downcast_variant(fx, variant);
 864             }
 865         }
 866     }
 867
 868     cplace
 869 }
 870
 871 pub(crate) fn codegen_operand<'tcx>(
 872     fx: &mut FunctionCx<'_, '_, 'tcx>,
 873     operand: &Operand<'tcx>,
 874 ) -> CValue<'tcx> {
 875     match operand {
 876         Operand::Move(place) | Operand::Copy(place) => {
 877             let cplace = codegen_place(fx, *place);
 878             cplace.to_cvalue(fx)
 879         }
 880         Operand::Constant(const_) => crate::constant::codegen_constant(fx, const_),
 881     }
 882 }
 883
 884 pub(crate) fn codegen_panic<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, msg_str: &str, span: Span) {
 885     let location = fx.get_caller_location(span).load_scalar(fx);
 886
 887     let msg_ptr = fx.anonymous_str(msg_str);
 888     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
 889     let args = [msg_ptr, msg_len, location];
 890
 891     codegen_panic_inner(fx, rustc_hir::LangItem::Panic, &args, span);
 892 }
 893
 894 pub(crate) fn codegen_panic_inner<'tcx>(
 895     fx: &mut FunctionCx<'_, '_, 'tcx>,
 896     lang_item: rustc_hir::LangItem,
 897     args: &[Value],
 898     span: Span,
 899 ) {
 900     let def_id =
 901         fx.tcx.lang_items().require(lang_item).unwrap_or_else(|s| fx.tcx.sess.span_fatal(span, &s));
 902
 903     let instance = Instance::mono(fx.tcx, def_id).polymorphize(fx.tcx);
 904     let symbol_name = fx.tcx.symbol_name(instance).name;
 905
 906     fx.lib_call(
 907         &*symbol_name,
 908         vec![
 909             AbiParam::new(fx.pointer_type),
 910             AbiParam::new(fx.pointer_type),
 911             AbiParam::new(fx.pointer_type),
 912         ],
 913         vec![],
 914         args,
 915     );
 916
 917     crate::trap::trap_unreachable(fx, "panic lang item returned");
 918 }