src/librustc_mir/shim.rs

   1 use rustc::hir;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::*;
   4 use rustc::ty::{self, Ty, TyCtxt};
   5 use rustc::ty::layout::VariantIdx;
   6 use rustc::ty::subst::{Subst, InternalSubsts};
   7 use rustc::ty::query::Providers;
   8
   9 use rustc_index::vec::{IndexVec, Idx};
  10
  11 use rustc_target::spec::abi::Abi;
  12 use syntax_pos::{Span, sym};
  13
  14 use std::fmt;
  15 use std::iter;
  16
  17 use crate::transform::{
  18     add_moves_for_packed_drops, add_call_guards,
  19     remove_noop_landing_pads, no_landing_pads, simplify, run_passes
  20 };
  21 use crate::util::elaborate_drops::{self, DropElaborator, DropStyle, DropFlagMode};
  22 use crate::util::patch::MirPatch;
  23 use crate::util::expand_aggregate;
  24
  25 pub fn provide(providers: &mut Providers<'_>) {
  26     providers.mir_shims = make_shim;
  27 }
  28
  29 fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
  30     debug!("make_shim({:?})", instance);
  31
  32     let mut result = match instance {
  33         ty::InstanceDef::Item(..) =>
  34             bug!("item {:?} passed to make_shim", instance),
  35         ty::InstanceDef::VtableShim(def_id) => {
  36             build_call_shim(
  37                 tcx,
  38                 def_id,
  39                 Adjustment::DerefMove,
  40                 CallKind::Direct(def_id),
  41                 None,
  42             )
  43         }
  44         ty::InstanceDef::FnPtrShim(def_id, ty) => {
  45             let trait_ = tcx.trait_of_item(def_id).unwrap();
  46             let adjustment = match tcx.lang_items().fn_trait_kind(trait_) {
  47                 Some(ty::ClosureKind::FnOnce) => Adjustment::Identity,
  48                 Some(ty::ClosureKind::FnMut) |
  49                 Some(ty::ClosureKind::Fn) => Adjustment::Deref,
  50                 None => bug!("fn pointer {:?} is not an fn", ty)
  51             };
  52             // HACK: we need the "real" argument types for the MIR,
  53             // but because our substs are (Self, Args), where Args
  54             // is a tuple, we must include the *concrete* argument
  55             // types in the MIR. They will be substituted again with
  56             // the param-substs, but because they are concrete, this
  57             // will not do any harm.
  58             let sig = tcx.erase_late_bound_regions(&ty.fn_sig(tcx));
  59             let arg_tys = sig.inputs();
  60
  61             build_call_shim(
  62                 tcx,
  63                 def_id,
  64                 adjustment,
  65                 CallKind::Indirect,
  66                 Some(arg_tys)
  67             )
  68         }
  69         // We are generating a call back to our def-id, which the
  70         // codegen backend knows to turn to an actual virtual call.
  71         ty::InstanceDef::Virtual(def_id, _) |
  72         // ...or we are generating a direct call to a function for which indirect calls must be
  73         // codegen'd differently than direct ones (example: #[track_caller])
  74         ty::InstanceDef::ReifyShim(def_id) => {
  75             build_call_shim(
  76                 tcx,
  77                 def_id,
  78                 Adjustment::Identity,
  79                 CallKind::Direct(def_id),
  80                 None
  81             )
  82         }
  83         ty::InstanceDef::ClosureOnceShim { call_once } => {
  84             let fn_mut = tcx.lang_items().fn_mut_trait().unwrap();
  85             let call_mut = tcx
  86                 .associated_items(fn_mut)
  87                 .find(|it| it.kind == ty::AssocKind::Method)
  88                 .unwrap().def_id;
  89
  90             build_call_shim(
  91                 tcx,
  92                 call_once,
  93                 Adjustment::RefMut,
  94                 CallKind::Direct(call_mut),
  95                 None
  96             )
  97         }
  98         ty::InstanceDef::DropGlue(def_id, ty) => {
  99             build_drop_shim(tcx, def_id, ty)
 100         }
 101         ty::InstanceDef::CloneShim(def_id, ty) => {
 102             let name = tcx.item_name(def_id);
 103             if name == sym::clone {
 104                 build_clone_shim(tcx, def_id, ty)
 105             } else if name == sym::clone_from {
 106                 debug!("make_shim({:?}: using default trait implementation", instance);
 107                 return tcx.optimized_mir(def_id);
 108             } else {
 109                 bug!("builtin clone shim {:?} not supported", instance)
 110             }
 111         }
 112         ty::InstanceDef::Intrinsic(_) => {
 113             bug!("creating shims from intrinsics ({:?}) is unsupported", instance)
 114         }
 115     };
 116     debug!("make_shim({:?}) = untransformed {:?}", instance, result);
 117
 118     run_passes(tcx, &mut result, instance, None, MirPhase::Const, &[
 119         &add_moves_for_packed_drops::AddMovesForPackedDrops,
 120         &no_landing_pads::NoLandingPads::new(tcx),
 121         &remove_noop_landing_pads::RemoveNoopLandingPads,
 122         &simplify::SimplifyCfg::new("make_shim"),
 123         &add_call_guards::CriticalCallEdges,
 124     ]);
 125
 126     debug!("make_shim({:?}) = {:?}", instance, result);
 127
 128     tcx.arena.alloc(result)
 129 }
 130
 131 #[derive(Copy, Clone, Debug, PartialEq)]
 132 enum Adjustment {
 133     Identity,
 134     Deref,
 135     DerefMove,
 136     RefMut,
 137 }
 138
 139 #[derive(Copy, Clone, Debug, PartialEq)]
 140 enum CallKind {
 141     Indirect,
 142     Direct(DefId),
 143 }
 144
 145 fn temp_decl(mutability: Mutability, ty: Ty<'_>, span: Span) -> LocalDecl<'_> {
 146     let source_info = SourceInfo { scope: OUTERMOST_SOURCE_SCOPE, span };
 147     LocalDecl {
 148         mutability,
 149         ty,
 150         user_ty: UserTypeProjections::none(),
 151         source_info,
 152         internal: false,
 153         local_info: LocalInfo::Other,
 154         is_block_tail: None,
 155     }
 156 }
 157
 158 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 159     -> IndexVec<Local, LocalDecl<'tcx>>
 160 {
 161     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 162         .chain(sig.inputs().iter().map(
 163             |ity| temp_decl(Mutability::Not, ity, span)))
 164         .collect()
 165 }
 166
 167 fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>) -> Body<'tcx> {
 168     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 169
 170     // Check if this is a generator, if so, return the drop glue for it
 171     if let Some(&ty::TyS { kind: ty::Generator(gen_def_id, substs, _), .. }) = ty {
 172         let body = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 173         return body.subst(tcx, substs);
 174     }
 175
 176     let substs = if let Some(ty) = ty {
 177         tcx.intern_substs(&[ty.into()])
 178     } else {
 179         InternalSubsts::identity_for_item(tcx, def_id)
 180     };
 181     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 182     let sig = tcx.erase_late_bound_regions(&sig);
 183     let span = tcx.def_span(def_id);
 184
 185     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 186
 187     let return_block = BasicBlock::new(1);
 188     let mut blocks = IndexVec::with_capacity(2);
 189     let block = |blocks: &mut IndexVec<_, _>, kind| {
 190         blocks.push(BasicBlockData {
 191             statements: vec![],
 192             terminator: Some(Terminator { source_info, kind }),
 193             is_cleanup: false
 194         })
 195     };
 196     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 197     block(&mut blocks, TerminatorKind::Return);
 198
 199     let mut body = new_body(
 200         blocks,
 201         IndexVec::from_elem_n(
 202             SourceScopeData { span, parent_scope: None }, 1
 203         ),
 204         local_decls_for_sig(&sig, span),
 205         sig.inputs().len(),
 206         span);
 207
 208     if let Some(..) = ty {
 209         // The first argument (index 0), but add 1 for the return value.
 210         let dropee_ptr = Place::from(Local::new(1+0));
 211         if tcx.sess.opts.debugging_opts.mir_emit_retag {
 212             // Function arguments should be retagged, and we make this one raw.
 213             body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
 214                 source_info,
 215                 kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
 216             });
 217         }
 218         let patch = {
 219             let param_env = tcx.param_env(def_id).with_reveal_all();
 220             let mut elaborator = DropShimElaborator {
 221                 body: &body,
 222                 patch: MirPatch::new(&body),
 223                 tcx,
 224                 param_env
 225             };
 226             let dropee = tcx.mk_place_deref(dropee_ptr);
 227             let resume_block = elaborator.patch.resume_block();
 228             elaborate_drops::elaborate_drop(
 229                 &mut elaborator,
 230                 source_info,
 231                 &dropee,
 232                 (),
 233                 return_block,
 234                 elaborate_drops::Unwind::To(resume_block),
 235                 START_BLOCK
 236             );
 237             elaborator.patch
 238         };
 239         patch.apply(&mut body);
 240     }
 241
 242     body
 243 }
 244
 245 fn new_body<'tcx>(
 246     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 247     source_scopes: IndexVec<SourceScope, SourceScopeData>,
 248     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 249     arg_count: usize,
 250     span: Span,
 251 ) -> Body<'tcx> {
 252     Body::new(
 253         basic_blocks,
 254         source_scopes,
 255         ClearCrossCrate::Clear,
 256         local_decls,
 257         IndexVec::new(),
 258         arg_count,
 259         vec![],
 260         span,
 261         vec![],
 262         None,
 263     )
 264 }
 265
 266 pub struct DropShimElaborator<'a, 'tcx> {
 267     pub body: &'a Body<'tcx>,
 268     pub patch: MirPatch<'tcx>,
 269     pub tcx: TyCtxt<'tcx>,
 270     pub param_env: ty::ParamEnv<'tcx>,
 271 }
 272
 273 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 274     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
 275         Ok(())
 276     }
 277 }
 278
 279 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 280     type Path = ();
 281
 282     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 283     fn body(&self) -> &'a Body<'tcx> { self.body }
 284     fn tcx(&self) -> TyCtxt<'tcx> {
 285         self.tcx
 286         }
 287     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 288
 289     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 290         if let DropFlagMode::Shallow = mode {
 291             DropStyle::Static
 292         } else {
 293             DropStyle::Open
 294         }
 295     }
 296
 297     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 298         None
 299     }
 300
 301     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 302     }
 303
 304     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 305         None
 306     }
 307     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 308         None
 309     }
 310     fn downcast_subpath(&self, _path: Self::Path, _variant: VariantIdx) -> Option<Self::Path> {
 311         Some(())
 312     }
 313     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 314         None
 315     }
 316 }
 317
 318 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 319 fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
 320     debug!("build_clone_shim(def_id={:?})", def_id);
 321
 322     let param_env = tcx.param_env(def_id);
 323
 324     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 325     let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env, builder.span);
 326
 327     let dest = Place::return_place();
 328     let src = tcx.mk_place_deref(Place::from(Local::new(1+0)));
 329
 330     match self_ty.kind {
 331         _ if is_copy => builder.copy_shim(),
 332         ty::Array(ty, len) => {
 333             let len = len.eval_usize(tcx, param_env);
 334             builder.array_shim(dest, src, ty, len)
 335         }
 336         ty::Closure(def_id, substs) => {
 337             builder.tuple_like_shim(
 338                 dest, src,
 339                 substs.as_closure().upvar_tys(def_id, tcx)
 340             )
 341         }
 342         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
 343         _ => {
 344             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 345         }
 346     };
 347
 348     builder.into_mir()
 349 }
 350
 351 struct CloneShimBuilder<'tcx> {
 352     tcx: TyCtxt<'tcx>,
 353     def_id: DefId,
 354     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 355     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 356     span: Span,
 357     sig: ty::FnSig<'tcx>,
 358 }
 359
 360 impl CloneShimBuilder<'tcx> {
 361     fn new(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Self {
 362         // we must subst the self_ty because it's
 363         // otherwise going to be TySelf and we can't index
 364         // or access fields of a Place of type TySelf.
 365         let substs = tcx.mk_substs_trait(self_ty, &[]);
 366         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 367         let sig = tcx.erase_late_bound_regions(&sig);
 368         let span = tcx.def_span(def_id);
 369
 370         CloneShimBuilder {
 371             tcx,
 372             def_id,
 373             local_decls: local_decls_for_sig(&sig, span),
 374             blocks: IndexVec::new(),
 375             span,
 376             sig,
 377         }
 378     }
 379
 380     fn into_mir(self) -> Body<'tcx> {
 381         new_body(
 382             self.blocks,
 383             IndexVec::from_elem_n(
 384                 SourceScopeData { span: self.span, parent_scope: None }, 1
 385             ),
 386             self.local_decls,
 387             self.sig.inputs().len(),
 388             self.span,
 389         )
 390     }
 391
 392     fn source_info(&self) -> SourceInfo {
 393         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 394     }
 395
 396     fn block(
 397         &mut self,
 398         statements: Vec<Statement<'tcx>>,
 399         kind: TerminatorKind<'tcx>,
 400         is_cleanup: bool
 401     ) -> BasicBlock {
 402         let source_info = self.source_info();
 403         self.blocks.push(BasicBlockData {
 404             statements,
 405             terminator: Some(Terminator { source_info, kind }),
 406             is_cleanup,
 407         })
 408     }
 409
 410     /// Gives the index of an upcoming BasicBlock, with an offset.
 411     /// offset=0 will give you the index of the next BasicBlock,
 412     /// offset=1 will give the index of the next-to-next block,
 413     /// offset=-1 will give you the index of the last-created block
 414     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 415         BasicBlock::new(self.blocks.len() + offset)
 416     }
 417
 418     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 419         Statement {
 420             source_info: self.source_info(),
 421             kind,
 422         }
 423     }
 424
 425     fn copy_shim(&mut self) {
 426         let rcvr = self.tcx.mk_place_deref(Place::from(Local::new(1+0)));
 427         let ret_statement = self.make_statement(
 428             StatementKind::Assign(
 429                 box(
 430                     Place::return_place(),
 431                     Rvalue::Use(Operand::Copy(rcvr))
 432                 )
 433             )
 434         );
 435         self.block(vec![ret_statement], TerminatorKind::Return, false);
 436     }
 437
 438     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 439         let span = self.span;
 440         Place::from(self.local_decls.push(temp_decl(mutability, ty, span)))
 441     }
 442
 443     fn make_clone_call(
 444         &mut self,
 445         dest: Place<'tcx>,
 446         src: Place<'tcx>,
 447         ty: Ty<'tcx>,
 448         next: BasicBlock,
 449         cleanup: BasicBlock
 450     ) {
 451         let tcx = self.tcx;
 452
 453         let substs = tcx.mk_substs_trait(ty, &[]);
 454
 455         // `func == Clone::clone(&ty) -> ty`
 456         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 457         let func = Operand::Constant(box Constant {
 458             span: self.span,
 459             user_ty: None,
 460             literal: ty::Const::zero_sized(tcx, func_ty),
 461         });
 462
 463         let ref_loc = self.make_place(
 464             Mutability::Not,
 465             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 466                 ty,
 467                 mutbl: hir::Mutability::Immutable,
 468             })
 469         );
 470
 471         // `let ref_loc: &ty = &src;`
 472         let statement = self.make_statement(
 473             StatementKind::Assign(
 474                 box(
 475                     ref_loc.clone(),
 476                     Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
 477                 )
 478             )
 479         );
 480
 481         // `let loc = Clone::clone(ref_loc);`
 482         self.block(vec![statement], TerminatorKind::Call {
 483             func,
 484             args: vec![Operand::Move(ref_loc)],
 485             destination: Some((dest, next)),
 486             cleanup: Some(cleanup),
 487             from_hir_call: true,
 488         }, false);
 489     }
 490
 491     fn loop_header(
 492         &mut self,
 493         beg: Place<'tcx>,
 494         end: Place<'tcx>,
 495         loop_body: BasicBlock,
 496         loop_end: BasicBlock,
 497         is_cleanup: bool
 498     ) {
 499         let tcx = self.tcx;
 500
 501         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 502         let compute_cond = self.make_statement(
 503             StatementKind::Assign(
 504                 box(
 505                     cond.clone(),
 506                     Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 507                 )
 508             )
 509         );
 510
 511         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 512         self.block(
 513             vec![compute_cond],
 514             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 515             is_cleanup
 516         );
 517     }
 518
 519     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 520         box Constant {
 521             span: self.span,
 522             user_ty: None,
 523             literal: ty::Const::from_usize(self.tcx, value),
 524         }
 525     }
 526
 527     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 528         let tcx = self.tcx;
 529         let span = self.span;
 530
 531         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 532         let end = self.make_place(Mutability::Not, tcx.types.usize);
 533
 534         // BB #0
 535         // `let mut beg = 0;`
 536         // `let end = len;`
 537         // `goto #1;`
 538         let inits = vec![
 539             self.make_statement(
 540                 StatementKind::Assign(
 541                     box(
 542                         Place::from(beg),
 543                         Rvalue::Use(Operand::Constant(self.make_usize(0)))
 544                     )
 545                 )
 546             ),
 547             self.make_statement(
 548                 StatementKind::Assign(
 549                     box(
 550                         end.clone(),
 551                         Rvalue::Use(Operand::Constant(self.make_usize(len)))
 552                     )
 553                 )
 554             )
 555         ];
 556         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 557
 558         // BB #1: loop {
 559         //     BB #2;
 560         //     BB #3;
 561         // }
 562         // BB #4;
 563         self.loop_header(Place::from(beg),
 564                          end,
 565                          BasicBlock::new(2),
 566                          BasicBlock::new(4),
 567                          false);
 568
 569         // BB #2
 570         // `dest[i] = Clone::clone(src[beg])`;
 571         // Goto #3 if ok, #5 if unwinding happens.
 572         let dest_field = self.tcx.mk_place_index(dest.clone(), beg);
 573         let src_field = self.tcx.mk_place_index(src, beg);
 574         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 575                              BasicBlock::new(5));
 576
 577         // BB #3
 578         // `beg = beg + 1;`
 579         // `goto #1`;
 580         let statements = vec![
 581             self.make_statement(
 582                 StatementKind::Assign(
 583                     box(
 584                         Place::from(beg),
 585                         Rvalue::BinaryOp(
 586                             BinOp::Add,
 587                             Operand::Copy(Place::from(beg)),
 588                             Operand::Constant(self.make_usize(1))
 589                         )
 590                     )
 591                 )
 592             )
 593         ];
 594         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 595
 596         // BB #4
 597         // `return dest;`
 598         self.block(vec![], TerminatorKind::Return, false);
 599
 600         // BB #5 (cleanup)
 601         // `let end = beg;`
 602         // `let mut beg = 0;`
 603         // goto #6;
 604         let end = beg;
 605         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 606         let init = self.make_statement(
 607             StatementKind::Assign(
 608                 box(
 609                     Place::from(beg),
 610                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 611                 )
 612             )
 613         );
 614         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 615
 616         // BB #6 (cleanup): loop {
 617         //     BB #7;
 618         //     BB #8;
 619         // }
 620         // BB #9;
 621         self.loop_header(Place::from(beg), Place::from(end),
 622                          BasicBlock::new(7), BasicBlock::new(9), true);
 623
 624         // BB #7 (cleanup)
 625         // `drop(dest[beg])`;
 626         self.block(vec![], TerminatorKind::Drop {
 627             location: self.tcx.mk_place_index(dest, beg),
 628             target: BasicBlock::new(8),
 629             unwind: None,
 630         }, true);
 631
 632         // BB #8 (cleanup)
 633         // `beg = beg + 1;`
 634         // `goto #6;`
 635         let statement = self.make_statement(
 636             StatementKind::Assign(
 637                 box(
 638                     Place::from(beg),
 639                     Rvalue::BinaryOp(
 640                         BinOp::Add,
 641                         Operand::Copy(Place::from(beg)),
 642                         Operand::Constant(self.make_usize(1))
 643                     )
 644                 )
 645             )
 646         );
 647         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 648
 649         // BB #9 (resume)
 650         self.block(vec![], TerminatorKind::Resume, true);
 651     }
 652
 653     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 654                           src: Place<'tcx>, tys: I)
 655             where I: Iterator<Item = Ty<'tcx>> {
 656         let mut previous_field = None;
 657         for (i, ity) in tys.enumerate() {
 658             let field = Field::new(i);
 659             let src_field = self.tcx.mk_place_field(src.clone(), field, ity);
 660
 661             let dest_field = self.tcx.mk_place_field(dest.clone(), field, ity);
 662
 663             // #(2i + 1) is the cleanup block for the previous clone operation
 664             let cleanup_block = self.block_index_offset(1);
 665             // #(2i + 2) is the next cloning block
 666             // (or the Return terminator if this is the last block)
 667             let next_block = self.block_index_offset(2);
 668
 669             // BB #(2i)
 670             // `dest.i = Clone::clone(&src.i);`
 671             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 672             self.make_clone_call(
 673                 dest_field.clone(),
 674                 src_field,
 675                 ity,
 676                 next_block,
 677                 cleanup_block,
 678             );
 679
 680             // BB #(2i + 1) (cleanup)
 681             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 682                 // Drop previous field and goto previous cleanup block.
 683                 self.block(vec![], TerminatorKind::Drop {
 684                     location: previous_field,
 685                     target: previous_cleanup,
 686                     unwind: None,
 687                 }, true);
 688             } else {
 689                 // Nothing to drop, just resume.
 690                 self.block(vec![], TerminatorKind::Resume, true);
 691             }
 692
 693             previous_field = Some((dest_field, cleanup_block));
 694         }
 695
 696         self.block(vec![], TerminatorKind::Return, false);
 697     }
 698 }
 699
 700 /// Builds a "call" shim for `def_id`. The shim calls the
 701 /// function specified by `call_kind`, first adjusting its first
 702 /// argument according to `rcvr_adjustment`.
 703 ///
 704 /// If `untuple_args` is a vec of types, the second argument of the
 705 /// function will be untupled as these types.
 706 fn build_call_shim<'tcx>(
 707     tcx: TyCtxt<'tcx>,
 708     def_id: DefId,
 709     rcvr_adjustment: Adjustment,
 710     call_kind: CallKind,
 711     untuple_args: Option<&[Ty<'tcx>]>,
 712 ) -> Body<'tcx> {
 713     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 714             call_kind={:?}, untuple_args={:?})",
 715            def_id, rcvr_adjustment, call_kind, untuple_args);
 716
 717     let sig = tcx.fn_sig(def_id);
 718     let sig = tcx.erase_late_bound_regions(&sig);
 719     let span = tcx.def_span(def_id);
 720
 721     debug!("build_call_shim: sig={:?}", sig);
 722
 723     let mut local_decls = local_decls_for_sig(&sig, span);
 724     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 725
 726     let rcvr_arg = Local::new(1+0);
 727     let rcvr_l = Place::from(rcvr_arg);
 728     let mut statements = vec![];
 729
 730     let rcvr = match rcvr_adjustment {
 731         Adjustment::Identity => Operand::Move(rcvr_l),
 732         Adjustment::Deref => Operand::Copy(tcx.mk_place_deref(rcvr_l)),
 733         Adjustment::DerefMove => {
 734             // fn(Self, ...) -> fn(*mut Self, ...)
 735             let arg_ty = local_decls[rcvr_arg].ty;
 736             debug_assert!(tcx.generics_of(def_id).has_self && arg_ty == tcx.types.self_param);
 737             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 738
 739             Operand::Move(tcx.mk_place_deref(rcvr_l))
 740         }
 741         Adjustment::RefMut => {
 742             // let rcvr = &mut rcvr;
 743             let ref_rcvr = local_decls.push(temp_decl(
 744                 Mutability::Not,
 745                 tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 746                     ty: sig.inputs()[0],
 747                     mutbl: hir::Mutability::Mutable
 748                 }),
 749                 span
 750             ));
 751             let borrow_kind = BorrowKind::Mut {
 752                 allow_two_phase_borrow: false,
 753             };
 754             statements.push(Statement {
 755                 source_info,
 756                 kind: StatementKind::Assign(
 757                     box(
 758                         Place::from(ref_rcvr),
 759                         Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
 760                     )
 761                 )
 762             });
 763             Operand::Move(Place::from(ref_rcvr))
 764         }
 765     };
 766
 767     let (callee, mut args) = match call_kind {
 768         CallKind::Indirect => (rcvr, vec![]),
 769         CallKind::Direct(def_id) => {
 770             let ty = tcx.type_of(def_id);
 771             (Operand::Constant(box Constant {
 772                 span,
 773                 user_ty: None,
 774                 literal: ty::Const::zero_sized(tcx, ty),
 775              }),
 776              vec![rcvr])
 777         }
 778     };
 779
 780     if let Some(untuple_args) = untuple_args {
 781         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 782             let arg_place = Place::from(Local::new(1+1));
 783             Operand::Move(tcx.mk_place_field(arg_place, Field::new(i), *ity))
 784         }));
 785     } else {
 786         args.extend((1..sig.inputs().len()).map(|i| {
 787             Operand::Move(Place::from(Local::new(1+i)))
 788         }));
 789     }
 790
 791     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 792     let mut blocks = IndexVec::with_capacity(n_blocks);
 793     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 794         blocks.push(BasicBlockData {
 795             statements,
 796             terminator: Some(Terminator { source_info, kind }),
 797             is_cleanup
 798         })
 799     };
 800
 801     // BB #0
 802     block(&mut blocks, statements, TerminatorKind::Call {
 803         func: callee,
 804         args,
 805         destination: Some((Place::return_place(),
 806                            BasicBlock::new(1))),
 807         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 808             Some(BasicBlock::new(3))
 809         } else {
 810             None
 811         },
 812         from_hir_call: true,
 813     }, false);
 814
 815     if let Adjustment::RefMut = rcvr_adjustment {
 816         // BB #1 - drop for Self
 817         block(&mut blocks, vec![], TerminatorKind::Drop {
 818             location: Place::from(rcvr_arg),
 819             target: BasicBlock::new(2),
 820             unwind: None
 821         }, false);
 822     }
 823     // BB #1/#2 - return
 824     block(&mut blocks, vec![], TerminatorKind::Return, false);
 825     if let Adjustment::RefMut = rcvr_adjustment {
 826         // BB #3 - drop if closure panics
 827         block(&mut blocks, vec![], TerminatorKind::Drop {
 828             location: Place::from(rcvr_arg),
 829             target: BasicBlock::new(4),
 830             unwind: None
 831         }, true);
 832
 833         // BB #4 - resume
 834         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 835     }
 836
 837     let mut body = new_body(
 838         blocks,
 839         IndexVec::from_elem_n(
 840             SourceScopeData { span, parent_scope: None }, 1
 841         ),
 842         local_decls,
 843         sig.inputs().len(),
 844         span,
 845     );
 846
 847     if let Abi::RustCall = sig.abi {
 848         body.spread_arg = Some(Local::new(sig.inputs().len()));
 849     }
 850     body
 851 }
 852
 853 pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> &Body<'_> {
 854     debug_assert!(tcx.is_constructor(ctor_id));
 855
 856     let span = tcx.hir().span_if_local(ctor_id)
 857         .unwrap_or_else(|| bug!("no span for ctor {:?}", ctor_id));
 858
 859     let param_env = tcx.param_env(ctor_id);
 860
 861     // Normalize the sig.
 862     let sig = tcx.fn_sig(ctor_id)
 863         .no_bound_vars()
 864         .expect("LBR in ADT constructor signature");
 865     let sig = tcx.normalize_erasing_regions(param_env, sig);
 866
 867     let (adt_def, substs) = match sig.output().kind {
 868         ty::Adt(adt_def, substs) => (adt_def, substs),
 869         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 870     };
 871
 872     debug!("build_ctor: ctor_id={:?} sig={:?}", ctor_id, sig);
 873
 874     let local_decls = local_decls_for_sig(&sig, span);
 875
 876     let source_info = SourceInfo {
 877         span,
 878         scope: OUTERMOST_SOURCE_SCOPE
 879     };
 880
 881     let variant_index = if adt_def.is_enum() {
 882         adt_def.variant_index_with_ctor_id(ctor_id)
 883     } else {
 884         VariantIdx::new(0)
 885     };
 886
 887     // Generate the following MIR:
 888     //
 889     // (return as Variant).field0 = arg0;
 890     // (return as Variant).field1 = arg1;
 891     //
 892     // return;
 893     debug!("build_ctor: variant_index={:?}", variant_index);
 894
 895     let statements = expand_aggregate(
 896         Place::return_place(),
 897         adt_def
 898             .variants[variant_index]
 899             .fields
 900             .iter()
 901             .enumerate()
 902             .map(|(idx, field_def)| (
 903                 Operand::Move(Place::from(Local::new(idx + 1))),
 904                 field_def.ty(tcx, substs),
 905             )),
 906         AggregateKind::Adt(adt_def, variant_index, substs, None, None),
 907         source_info,
 908         tcx,
 909     ).collect();
 910
 911     let start_block = BasicBlockData {
 912         statements,
 913         terminator: Some(Terminator {
 914             source_info,
 915             kind: TerminatorKind::Return,
 916         }),
 917         is_cleanup: false
 918     };
 919
 920     let body = new_body(
 921         IndexVec::from_elem_n(start_block, 1),
 922         IndexVec::from_elem_n(
 923             SourceScopeData { span, parent_scope: None }, 1
 924         ),
 925         local_decls,
 926         sig.inputs().len(),
 927         span,
 928     );
 929
 930     crate::util::dump_mir(
 931         tcx,
 932         None,
 933         "mir_map",
 934         &0,
 935         crate::transform::MirSource::item(ctor_id),
 936         &body,
 937         |_, _| Ok(()),
 938     );
 939
 940     tcx.arena.alloc(body)
 941 }