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