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         local_decls_for_sig(&sig, span),
 202         sig.inputs().len(),
 203         span);
 204
 205     let mut body_cache = BodyCache::new(&mut body);
 206
 207     if let Some(..) = ty {
 208         // The first argument (index 0), but add 1 for the return value.
 209         let dropee_ptr = Place::from(Local::new(1+0));
 210         if tcx.sess.opts.debugging_opts.mir_emit_retag {
 211             // Function arguments should be retagged, and we make this one raw.
 212             body_cache.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
 213                 source_info,
 214                 kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
 215             });
 216         }
 217         let patch = {
 218             let param_env = tcx.param_env(def_id).with_reveal_all();
 219             let mut elaborator = DropShimElaborator {
 220                 body: body_cache.body(),
 221                 patch: MirPatch::new(body_cache.body()),
 222                 tcx,
 223                 param_env
 224             };
 225             let dropee = tcx.mk_place_deref(dropee_ptr);
 226             let resume_block = elaborator.patch.resume_block();
 227             elaborate_drops::elaborate_drop(
 228                 &mut elaborator,
 229                 source_info,
 230                 &dropee,
 231                 (),
 232                 return_block,
 233                 elaborate_drops::Unwind::To(resume_block),
 234                 START_BLOCK
 235             );
 236             elaborator.patch
 237         };
 238         patch.apply(&mut body_cache);
 239     }
 240
 241     // TODO(pfaia) return owning body cache...
 242     body
 243 }
 244
 245 fn new_body<'tcx>(
 246     basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 247     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 248     arg_count: usize,
 249     span: Span,
 250 ) -> Body<'tcx> {
 251     Body::new(
 252         basic_blocks,
 253         IndexVec::from_elem_n(
 254             SourceScopeData { span, parent_scope: None, local_data: ClearCrossCrate::Clear },
 255             1,
 256         ),
 257         local_decls,
 258         IndexVec::new(),
 259         arg_count,
 260         vec![],
 261         span,
 262         vec![],
 263         None,
 264     )
 265 }
 266
 267 pub struct DropShimElaborator<'a, 'tcx> {
 268     pub body: &'a Body<'tcx>,
 269     pub patch: MirPatch<'tcx>,
 270     pub tcx: TyCtxt<'tcx>,
 271     pub param_env: ty::ParamEnv<'tcx>,
 272 }
 273
 274 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 275     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
 276         Ok(())
 277     }
 278 }
 279
 280 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 281     type Path = ();
 282
 283     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 284     fn body(&self) -> &'a Body<'tcx> { self.body }
 285     fn tcx(&self) -> TyCtxt<'tcx> {
 286         self.tcx
 287         }
 288     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 289
 290     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 291         if let DropFlagMode::Shallow = mode {
 292             DropStyle::Static
 293         } else {
 294             DropStyle::Open
 295         }
 296     }
 297
 298     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 299         None
 300     }
 301
 302     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 303     }
 304
 305     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 306         None
 307     }
 308     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 309         None
 310     }
 311     fn downcast_subpath(&self, _path: Self::Path, _variant: VariantIdx) -> Option<Self::Path> {
 312         Some(())
 313     }
 314     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 315         None
 316     }
 317 }
 318
 319 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 320 fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
 321     debug!("build_clone_shim(def_id={:?})", def_id);
 322
 323     let param_env = tcx.param_env(def_id);
 324
 325     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 326     let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env, builder.span);
 327
 328     let dest = Place::return_place();
 329     let src = tcx.mk_place_deref(Place::from(Local::new(1+0)));
 330
 331     match self_ty.kind {
 332         _ if is_copy => builder.copy_shim(),
 333         ty::Array(ty, len) => {
 334             let len = len.eval_usize(tcx, param_env);
 335             builder.array_shim(dest, src, ty, len)
 336         }
 337         ty::Closure(def_id, substs) => {
 338             builder.tuple_like_shim(
 339                 dest, src,
 340                 substs.as_closure().upvar_tys(def_id, tcx)
 341             )
 342         }
 343         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
 344         _ => {
 345             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 346         }
 347     };
 348
 349     builder.into_mir()
 350 }
 351
 352 struct CloneShimBuilder<'tcx> {
 353     tcx: TyCtxt<'tcx>,
 354     def_id: DefId,
 355     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 356     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 357     span: Span,
 358     sig: ty::FnSig<'tcx>,
 359 }
 360
 361 impl CloneShimBuilder<'tcx> {
 362     fn new(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Self {
 363         // we must subst the self_ty because it's
 364         // otherwise going to be TySelf and we can't index
 365         // or access fields of a Place of type TySelf.
 366         let substs = tcx.mk_substs_trait(self_ty, &[]);
 367         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 368         let sig = tcx.erase_late_bound_regions(&sig);
 369         let span = tcx.def_span(def_id);
 370
 371         CloneShimBuilder {
 372             tcx,
 373             def_id,
 374             local_decls: local_decls_for_sig(&sig, span),
 375             blocks: IndexVec::new(),
 376             span,
 377             sig,
 378         }
 379     }
 380
 381     fn into_mir(self) -> Body<'tcx> {
 382         new_body(
 383             self.blocks,
 384             self.local_decls,
 385             self.sig.inputs().len(),
 386             self.span,
 387         )
 388     }
 389
 390     fn source_info(&self) -> SourceInfo {
 391         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 392     }
 393
 394     fn block(
 395         &mut self,
 396         statements: Vec<Statement<'tcx>>,
 397         kind: TerminatorKind<'tcx>,
 398         is_cleanup: bool
 399     ) -> BasicBlock {
 400         let source_info = self.source_info();
 401         self.blocks.push(BasicBlockData {
 402             statements,
 403             terminator: Some(Terminator { source_info, kind }),
 404             is_cleanup,
 405         })
 406     }
 407
 408     /// Gives the index of an upcoming BasicBlock, with an offset.
 409     /// offset=0 will give you the index of the next BasicBlock,
 410     /// offset=1 will give the index of the next-to-next block,
 411     /// offset=-1 will give you the index of the last-created block
 412     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 413         BasicBlock::new(self.blocks.len() + offset)
 414     }
 415
 416     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 417         Statement {
 418             source_info: self.source_info(),
 419             kind,
 420         }
 421     }
 422
 423     fn copy_shim(&mut self) {
 424         let rcvr = self.tcx.mk_place_deref(Place::from(Local::new(1+0)));
 425         let ret_statement = self.make_statement(
 426             StatementKind::Assign(
 427                 box(
 428                     Place::return_place(),
 429                     Rvalue::Use(Operand::Copy(rcvr))
 430                 )
 431             )
 432         );
 433         self.block(vec![ret_statement], TerminatorKind::Return, false);
 434     }
 435
 436     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 437         let span = self.span;
 438         Place::from(self.local_decls.push(temp_decl(mutability, ty, span)))
 439     }
 440
 441     fn make_clone_call(
 442         &mut self,
 443         dest: Place<'tcx>,
 444         src: Place<'tcx>,
 445         ty: Ty<'tcx>,
 446         next: BasicBlock,
 447         cleanup: BasicBlock
 448     ) {
 449         let tcx = self.tcx;
 450
 451         let substs = tcx.mk_substs_trait(ty, &[]);
 452
 453         // `func == Clone::clone(&ty) -> ty`
 454         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 455         let func = Operand::Constant(box Constant {
 456             span: self.span,
 457             user_ty: None,
 458             literal: ty::Const::zero_sized(tcx, func_ty),
 459         });
 460
 461         let ref_loc = self.make_place(
 462             Mutability::Not,
 463             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 464                 ty,
 465                 mutbl: hir::Mutability::Immutable,
 466             })
 467         );
 468
 469         // `let ref_loc: &ty = &src;`
 470         let statement = self.make_statement(
 471             StatementKind::Assign(
 472                 box(
 473                     ref_loc.clone(),
 474                     Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
 475                 )
 476             )
 477         );
 478
 479         // `let loc = Clone::clone(ref_loc);`
 480         self.block(vec![statement], TerminatorKind::Call {
 481             func,
 482             args: vec![Operand::Move(ref_loc)],
 483             destination: Some((dest, next)),
 484             cleanup: Some(cleanup),
 485             from_hir_call: true,
 486         }, false);
 487     }
 488
 489     fn loop_header(
 490         &mut self,
 491         beg: Place<'tcx>,
 492         end: Place<'tcx>,
 493         loop_body: BasicBlock,
 494         loop_end: BasicBlock,
 495         is_cleanup: bool
 496     ) {
 497         let tcx = self.tcx;
 498
 499         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 500         let compute_cond = self.make_statement(
 501             StatementKind::Assign(
 502                 box(
 503                     cond.clone(),
 504                     Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 505                 )
 506             )
 507         );
 508
 509         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 510         self.block(
 511             vec![compute_cond],
 512             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 513             is_cleanup
 514         );
 515     }
 516
 517     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 518         box Constant {
 519             span: self.span,
 520             user_ty: None,
 521             literal: ty::Const::from_usize(self.tcx, value),
 522         }
 523     }
 524
 525     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 526         let tcx = self.tcx;
 527         let span = self.span;
 528
 529         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 530         let end = self.make_place(Mutability::Not, tcx.types.usize);
 531
 532         // BB #0
 533         // `let mut beg = 0;`
 534         // `let end = len;`
 535         // `goto #1;`
 536         let inits = vec![
 537             self.make_statement(
 538                 StatementKind::Assign(
 539                     box(
 540                         Place::from(beg),
 541                         Rvalue::Use(Operand::Constant(self.make_usize(0)))
 542                     )
 543                 )
 544             ),
 545             self.make_statement(
 546                 StatementKind::Assign(
 547                     box(
 548                         end.clone(),
 549                         Rvalue::Use(Operand::Constant(self.make_usize(len)))
 550                     )
 551                 )
 552             )
 553         ];
 554         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 555
 556         // BB #1: loop {
 557         //     BB #2;
 558         //     BB #3;
 559         // }
 560         // BB #4;
 561         self.loop_header(Place::from(beg),
 562                          end,
 563                          BasicBlock::new(2),
 564                          BasicBlock::new(4),
 565                          false);
 566
 567         // BB #2
 568         // `dest[i] = Clone::clone(src[beg])`;
 569         // Goto #3 if ok, #5 if unwinding happens.
 570         let dest_field = self.tcx.mk_place_index(dest.clone(), beg);
 571         let src_field = self.tcx.mk_place_index(src, beg);
 572         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 573                              BasicBlock::new(5));
 574
 575         // BB #3
 576         // `beg = beg + 1;`
 577         // `goto #1`;
 578         let statements = vec![
 579             self.make_statement(
 580                 StatementKind::Assign(
 581                     box(
 582                         Place::from(beg),
 583                         Rvalue::BinaryOp(
 584                             BinOp::Add,
 585                             Operand::Copy(Place::from(beg)),
 586                             Operand::Constant(self.make_usize(1))
 587                         )
 588                     )
 589                 )
 590             )
 591         ];
 592         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 593
 594         // BB #4
 595         // `return dest;`
 596         self.block(vec![], TerminatorKind::Return, false);
 597
 598         // BB #5 (cleanup)
 599         // `let end = beg;`
 600         // `let mut beg = 0;`
 601         // goto #6;
 602         let end = beg;
 603         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 604         let init = self.make_statement(
 605             StatementKind::Assign(
 606                 box(
 607                     Place::from(beg),
 608                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 609                 )
 610             )
 611         );
 612         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 613
 614         // BB #6 (cleanup): loop {
 615         //     BB #7;
 616         //     BB #8;
 617         // }
 618         // BB #9;
 619         self.loop_header(Place::from(beg), Place::from(end),
 620                          BasicBlock::new(7), BasicBlock::new(9), true);
 621
 622         // BB #7 (cleanup)
 623         // `drop(dest[beg])`;
 624         self.block(vec![], TerminatorKind::Drop {
 625             location: self.tcx.mk_place_index(dest, beg),
 626             target: BasicBlock::new(8),
 627             unwind: None,
 628         }, true);
 629
 630         // BB #8 (cleanup)
 631         // `beg = beg + 1;`
 632         // `goto #6;`
 633         let statement = self.make_statement(
 634             StatementKind::Assign(
 635                 box(
 636                     Place::from(beg),
 637                     Rvalue::BinaryOp(
 638                         BinOp::Add,
 639                         Operand::Copy(Place::from(beg)),
 640                         Operand::Constant(self.make_usize(1))
 641                     )
 642                 )
 643             )
 644         );
 645         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 646
 647         // BB #9 (resume)
 648         self.block(vec![], TerminatorKind::Resume, true);
 649     }
 650
 651     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 652                           src: Place<'tcx>, tys: I)
 653             where I: Iterator<Item = Ty<'tcx>> {
 654         let mut previous_field = None;
 655         for (i, ity) in tys.enumerate() {
 656             let field = Field::new(i);
 657             let src_field = self.tcx.mk_place_field(src.clone(), field, ity);
 658
 659             let dest_field = self.tcx.mk_place_field(dest.clone(), field, ity);
 660
 661             // #(2i + 1) is the cleanup block for the previous clone operation
 662             let cleanup_block = self.block_index_offset(1);
 663             // #(2i + 2) is the next cloning block
 664             // (or the Return terminator if this is the last block)
 665             let next_block = self.block_index_offset(2);
 666
 667             // BB #(2i)
 668             // `dest.i = Clone::clone(&src.i);`
 669             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 670             self.make_clone_call(
 671                 dest_field.clone(),
 672                 src_field,
 673                 ity,
 674                 next_block,
 675                 cleanup_block,
 676             );
 677
 678             // BB #(2i + 1) (cleanup)
 679             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 680                 // Drop previous field and goto previous cleanup block.
 681                 self.block(vec![], TerminatorKind::Drop {
 682                     location: previous_field,
 683                     target: previous_cleanup,
 684                     unwind: None,
 685                 }, true);
 686             } else {
 687                 // Nothing to drop, just resume.
 688                 self.block(vec![], TerminatorKind::Resume, true);
 689             }
 690
 691             previous_field = Some((dest_field, cleanup_block));
 692         }
 693
 694         self.block(vec![], TerminatorKind::Return, false);
 695     }
 696 }
 697
 698 /// Builds a "call" shim for `def_id`. The shim calls the
 699 /// function specified by `call_kind`, first adjusting its first
 700 /// argument according to `rcvr_adjustment`.
 701 ///
 702 /// If `untuple_args` is a vec of types, the second argument of the
 703 /// function will be untupled as these types.
 704 fn build_call_shim<'tcx>(
 705     tcx: TyCtxt<'tcx>,
 706     def_id: DefId,
 707     rcvr_adjustment: Adjustment,
 708     call_kind: CallKind,
 709     untuple_args: Option<&[Ty<'tcx>]>,
 710 ) -> Body<'tcx> {
 711     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 712             call_kind={:?}, untuple_args={:?})",
 713            def_id, rcvr_adjustment, call_kind, untuple_args);
 714
 715     let sig = tcx.fn_sig(def_id);
 716     let sig = tcx.erase_late_bound_regions(&sig);
 717     let span = tcx.def_span(def_id);
 718
 719     debug!("build_call_shim: sig={:?}", sig);
 720
 721     let mut local_decls = local_decls_for_sig(&sig, span);
 722     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 723
 724     let rcvr_arg = Local::new(1+0);
 725     let rcvr_l = Place::from(rcvr_arg);
 726     let mut statements = vec![];
 727
 728     let rcvr = match rcvr_adjustment {
 729         Adjustment::Identity => Operand::Move(rcvr_l),
 730         Adjustment::Deref => Operand::Copy(tcx.mk_place_deref(rcvr_l)),
 731         Adjustment::DerefMove => {
 732             // fn(Self, ...) -> fn(*mut Self, ...)
 733             let arg_ty = local_decls[rcvr_arg].ty;
 734             debug_assert!(tcx.generics_of(def_id).has_self && arg_ty == tcx.types.self_param);
 735             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 736
 737             Operand::Move(tcx.mk_place_deref(rcvr_l))
 738         }
 739         Adjustment::RefMut => {
 740             // let rcvr = &mut rcvr;
 741             let ref_rcvr = local_decls.push(temp_decl(
 742                 Mutability::Not,
 743                 tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 744                     ty: sig.inputs()[0],
 745                     mutbl: hir::Mutability::Mutable
 746                 }),
 747                 span
 748             ));
 749             let borrow_kind = BorrowKind::Mut {
 750                 allow_two_phase_borrow: false,
 751             };
 752             statements.push(Statement {
 753                 source_info,
 754                 kind: StatementKind::Assign(
 755                     box(
 756                         Place::from(ref_rcvr),
 757                         Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
 758                     )
 759                 )
 760             });
 761             Operand::Move(Place::from(ref_rcvr))
 762         }
 763     };
 764
 765     let (callee, mut args) = match call_kind {
 766         CallKind::Indirect => (rcvr, vec![]),
 767         CallKind::Direct(def_id) => {
 768             let ty = tcx.type_of(def_id);
 769             (Operand::Constant(box Constant {
 770                 span,
 771                 user_ty: None,
 772                 literal: ty::Const::zero_sized(tcx, ty),
 773              }),
 774              vec![rcvr])
 775         }
 776     };
 777
 778     if let Some(untuple_args) = untuple_args {
 779         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 780             let arg_place = Place::from(Local::new(1+1));
 781             Operand::Move(tcx.mk_place_field(arg_place, Field::new(i), *ity))
 782         }));
 783     } else {
 784         args.extend((1..sig.inputs().len()).map(|i| {
 785             Operand::Move(Place::from(Local::new(1+i)))
 786         }));
 787     }
 788
 789     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 790     let mut blocks = IndexVec::with_capacity(n_blocks);
 791     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 792         blocks.push(BasicBlockData {
 793             statements,
 794             terminator: Some(Terminator { source_info, kind }),
 795             is_cleanup
 796         })
 797     };
 798
 799     // BB #0
 800     block(&mut blocks, statements, TerminatorKind::Call {
 801         func: callee,
 802         args,
 803         destination: Some((Place::return_place(),
 804                            BasicBlock::new(1))),
 805         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 806             Some(BasicBlock::new(3))
 807         } else {
 808             None
 809         },
 810         from_hir_call: true,
 811     }, false);
 812
 813     if let Adjustment::RefMut = rcvr_adjustment {
 814         // BB #1 - drop for Self
 815         block(&mut blocks, vec![], TerminatorKind::Drop {
 816             location: Place::from(rcvr_arg),
 817             target: BasicBlock::new(2),
 818             unwind: None
 819         }, false);
 820     }
 821     // BB #1/#2 - return
 822     block(&mut blocks, vec![], TerminatorKind::Return, false);
 823     if let Adjustment::RefMut = rcvr_adjustment {
 824         // BB #3 - drop if closure panics
 825         block(&mut blocks, vec![], TerminatorKind::Drop {
 826             location: Place::from(rcvr_arg),
 827             target: BasicBlock::new(4),
 828             unwind: None
 829         }, true);
 830
 831         // BB #4 - resume
 832         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 833     }
 834
 835     let mut body = new_body(
 836         blocks,
 837         local_decls,
 838         sig.inputs().len(),
 839         span,
 840     );
 841
 842     if let Abi::RustCall = sig.abi {
 843         body.spread_arg = Some(Local::new(sig.inputs().len()));
 844     }
 845     body
 846 }
 847
 848 pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> &Body<'_> {
 849     debug_assert!(tcx.is_constructor(ctor_id));
 850
 851     let span = tcx.hir().span_if_local(ctor_id)
 852         .unwrap_or_else(|| bug!("no span for ctor {:?}", ctor_id));
 853
 854     let param_env = tcx.param_env(ctor_id);
 855
 856     // Normalize the sig.
 857     let sig = tcx.fn_sig(ctor_id)
 858         .no_bound_vars()
 859         .expect("LBR in ADT constructor signature");
 860     let sig = tcx.normalize_erasing_regions(param_env, sig);
 861
 862     let (adt_def, substs) = match sig.output().kind {
 863         ty::Adt(adt_def, substs) => (adt_def, substs),
 864         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 865     };
 866
 867     debug!("build_ctor: ctor_id={:?} sig={:?}", ctor_id, sig);
 868
 869     let local_decls = local_decls_for_sig(&sig, span);
 870
 871     let source_info = SourceInfo {
 872         span,
 873         scope: OUTERMOST_SOURCE_SCOPE
 874     };
 875
 876     let variant_index = if adt_def.is_enum() {
 877         adt_def.variant_index_with_ctor_id(ctor_id)
 878     } else {
 879         VariantIdx::new(0)
 880     };
 881
 882     // Generate the following MIR:
 883     //
 884     // (return as Variant).field0 = arg0;
 885     // (return as Variant).field1 = arg1;
 886     //
 887     // return;
 888     debug!("build_ctor: variant_index={:?}", variant_index);
 889
 890     let statements = expand_aggregate(
 891         Place::return_place(),
 892         adt_def
 893             .variants[variant_index]
 894             .fields
 895             .iter()
 896             .enumerate()
 897             .map(|(idx, field_def)| (
 898                 Operand::Move(Place::from(Local::new(idx + 1))),
 899                 field_def.ty(tcx, substs),
 900             )),
 901         AggregateKind::Adt(adt_def, variant_index, substs, None, None),
 902         source_info,
 903         tcx,
 904     ).collect();
 905
 906     let start_block = BasicBlockData {
 907         statements,
 908         terminator: Some(Terminator {
 909             source_info,
 910             kind: TerminatorKind::Return,
 911         }),
 912         is_cleanup: false
 913     };
 914
 915     let mut body = new_body(
 916         IndexVec::from_elem_n(start_block, 1),
 917         local_decls,
 918         sig.inputs().len(),
 919         span,
 920     );
 921
 922     crate::util::dump_mir(
 923         tcx,
 924         None,
 925         "mir_map",
 926         &0,
 927         crate::transform::MirSource::item(ctor_id),
 928         &body,
 929         |_, _| Ok(()),
 930     );
 931
 932     tcx.arena.alloc(body)
 933 }