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 = Body::new(
 200         blocks,
 201         IndexVec::from_elem_n(
 202             SourceScopeData { span: span, parent_scope: None }, 1
 203         ),
 204         ClearCrossCrate::Clear,
 205         local_decls_for_sig(&sig, span),
 206         IndexVec::new(),
 207         sig.inputs().len(),
 208         vec![],
 209         span,
 210         vec![],
 211     );
 212
 213     if let Some(..) = ty {
 214         // The first argument (index 0), but add 1 for the return value.
 215         let dropee_ptr = Place::from(Local::new(1+0));
 216         if tcx.sess.opts.debugging_opts.mir_emit_retag {
 217             // Function arguments should be retagged, and we make this one raw.
 218             body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
 219                 source_info,
 220                 kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
 221             });
 222         }
 223         let patch = {
 224             let param_env = tcx.param_env(def_id).with_reveal_all();
 225             let mut elaborator = DropShimElaborator {
 226                 body: &body,
 227                 patch: MirPatch::new(&body),
 228                 tcx,
 229                 param_env
 230             };
 231             let dropee = tcx.mk_place_deref(dropee_ptr);
 232             let resume_block = elaborator.patch.resume_block();
 233             elaborate_drops::elaborate_drop(
 234                 &mut elaborator,
 235                 source_info,
 236                 &dropee,
 237                 (),
 238                 return_block,
 239                 elaborate_drops::Unwind::To(resume_block),
 240                 START_BLOCK
 241             );
 242             elaborator.patch
 243         };
 244         patch.apply(&mut body);
 245     }
 246
 247     body
 248 }
 249
 250 pub struct DropShimElaborator<'a, 'tcx> {
 251     pub body: &'a Body<'tcx>,
 252     pub patch: MirPatch<'tcx>,
 253     pub tcx: TyCtxt<'tcx>,
 254     pub param_env: ty::ParamEnv<'tcx>,
 255 }
 256
 257 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 258     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
 259         Ok(())
 260     }
 261 }
 262
 263 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 264     type Path = ();
 265
 266     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 267     fn body(&self) -> &'a Body<'tcx> { self.body }
 268     fn tcx(&self) -> TyCtxt<'tcx> {
 269         self.tcx
 270         }
 271     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 272
 273     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 274         if let DropFlagMode::Shallow = mode {
 275             DropStyle::Static
 276         } else {
 277             DropStyle::Open
 278         }
 279     }
 280
 281     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 282         None
 283     }
 284
 285     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 286     }
 287
 288     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 289         None
 290     }
 291     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 292         None
 293     }
 294     fn downcast_subpath(&self, _path: Self::Path, _variant: VariantIdx) -> Option<Self::Path> {
 295         Some(())
 296     }
 297     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 298         None
 299     }
 300 }
 301
 302 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 303 fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
 304     debug!("build_clone_shim(def_id={:?})", def_id);
 305
 306     let param_env = tcx.param_env(def_id);
 307
 308     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 309     let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env, builder.span);
 310
 311     let dest = Place::return_place();
 312     let src = tcx.mk_place_deref(Place::from(Local::new(1+0)));
 313
 314     match self_ty.kind {
 315         _ if is_copy => builder.copy_shim(),
 316         ty::Array(ty, len) => {
 317             let len = len.eval_usize(tcx, param_env);
 318             builder.array_shim(dest, src, ty, len)
 319         }
 320         ty::Closure(def_id, substs) => {
 321             builder.tuple_like_shim(
 322                 dest, src,
 323                 substs.as_closure().upvar_tys(def_id, tcx)
 324             )
 325         }
 326         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
 327         _ => {
 328             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 329         }
 330     };
 331
 332     builder.into_mir()
 333 }
 334
 335 struct CloneShimBuilder<'tcx> {
 336     tcx: TyCtxt<'tcx>,
 337     def_id: DefId,
 338     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 339     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 340     span: Span,
 341     sig: ty::FnSig<'tcx>,
 342 }
 343
 344 impl CloneShimBuilder<'tcx> {
 345     fn new(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Self {
 346         // we must subst the self_ty because it's
 347         // otherwise going to be TySelf and we can't index
 348         // or access fields of a Place of type TySelf.
 349         let substs = tcx.mk_substs_trait(self_ty, &[]);
 350         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 351         let sig = tcx.erase_late_bound_regions(&sig);
 352         let span = tcx.def_span(def_id);
 353
 354         CloneShimBuilder {
 355             tcx,
 356             def_id,
 357             local_decls: local_decls_for_sig(&sig, span),
 358             blocks: IndexVec::new(),
 359             span,
 360             sig,
 361         }
 362     }
 363
 364     fn into_mir(self) -> Body<'tcx> {
 365         Body::new(
 366             self.blocks,
 367             IndexVec::from_elem_n(
 368                 SourceScopeData { span: self.span, parent_scope: None }, 1
 369             ),
 370             ClearCrossCrate::Clear,
 371             self.local_decls,
 372             IndexVec::new(),
 373             self.sig.inputs().len(),
 374             vec![],
 375             self.span,
 376             vec![],
 377         )
 378     }
 379
 380     fn source_info(&self) -> SourceInfo {
 381         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 382     }
 383
 384     fn block(
 385         &mut self,
 386         statements: Vec<Statement<'tcx>>,
 387         kind: TerminatorKind<'tcx>,
 388         is_cleanup: bool
 389     ) -> BasicBlock {
 390         let source_info = self.source_info();
 391         self.blocks.push(BasicBlockData {
 392             statements,
 393             terminator: Some(Terminator { source_info, kind }),
 394             is_cleanup,
 395         })
 396     }
 397
 398     /// Gives the index of an upcoming BasicBlock, with an offset.
 399     /// offset=0 will give you the index of the next BasicBlock,
 400     /// offset=1 will give the index of the next-to-next block,
 401     /// offset=-1 will give you the index of the last-created block
 402     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 403         BasicBlock::new(self.blocks.len() + offset)
 404     }
 405
 406     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 407         Statement {
 408             source_info: self.source_info(),
 409             kind,
 410         }
 411     }
 412
 413     fn copy_shim(&mut self) {
 414         let rcvr = self.tcx.mk_place_deref(Place::from(Local::new(1+0)));
 415         let ret_statement = self.make_statement(
 416             StatementKind::Assign(
 417                 box(
 418                     Place::return_place(),
 419                     Rvalue::Use(Operand::Copy(rcvr))
 420                 )
 421             )
 422         );
 423         self.block(vec![ret_statement], TerminatorKind::Return, false);
 424     }
 425
 426     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 427         let span = self.span;
 428         Place::from(self.local_decls.push(temp_decl(mutability, ty, span)))
 429     }
 430
 431     fn make_clone_call(
 432         &mut self,
 433         dest: Place<'tcx>,
 434         src: Place<'tcx>,
 435         ty: Ty<'tcx>,
 436         next: BasicBlock,
 437         cleanup: BasicBlock
 438     ) {
 439         let tcx = self.tcx;
 440
 441         let substs = tcx.mk_substs_trait(ty, &[]);
 442
 443         // `func == Clone::clone(&ty) -> ty`
 444         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 445         let func = Operand::Constant(box Constant {
 446             span: self.span,
 447             user_ty: None,
 448             literal: ty::Const::zero_sized(tcx, func_ty),
 449         });
 450
 451         let ref_loc = self.make_place(
 452             Mutability::Not,
 453             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 454                 ty,
 455                 mutbl: hir::Mutability::Immutable,
 456             })
 457         );
 458
 459         // `let ref_loc: &ty = &src;`
 460         let statement = self.make_statement(
 461             StatementKind::Assign(
 462                 box(
 463                     ref_loc.clone(),
 464                     Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
 465                 )
 466             )
 467         );
 468
 469         // `let loc = Clone::clone(ref_loc);`
 470         self.block(vec![statement], TerminatorKind::Call {
 471             func,
 472             args: vec![Operand::Move(ref_loc)],
 473             destination: Some((dest, next)),
 474             cleanup: Some(cleanup),
 475             from_hir_call: true,
 476         }, false);
 477     }
 478
 479     fn loop_header(
 480         &mut self,
 481         beg: Place<'tcx>,
 482         end: Place<'tcx>,
 483         loop_body: BasicBlock,
 484         loop_end: BasicBlock,
 485         is_cleanup: bool
 486     ) {
 487         let tcx = self.tcx;
 488
 489         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 490         let compute_cond = self.make_statement(
 491             StatementKind::Assign(
 492                 box(
 493                     cond.clone(),
 494                     Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 495                 )
 496             )
 497         );
 498
 499         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 500         self.block(
 501             vec![compute_cond],
 502             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 503             is_cleanup
 504         );
 505     }
 506
 507     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 508         box Constant {
 509             span: self.span,
 510             user_ty: None,
 511             literal: ty::Const::from_usize(self.tcx, value),
 512         }
 513     }
 514
 515     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 516         let tcx = self.tcx;
 517         let span = self.span;
 518
 519         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 520         let end = self.make_place(Mutability::Not, tcx.types.usize);
 521
 522         // BB #0
 523         // `let mut beg = 0;`
 524         // `let end = len;`
 525         // `goto #1;`
 526         let inits = vec![
 527             self.make_statement(
 528                 StatementKind::Assign(
 529                     box(
 530                         Place::from(beg),
 531                         Rvalue::Use(Operand::Constant(self.make_usize(0)))
 532                     )
 533                 )
 534             ),
 535             self.make_statement(
 536                 StatementKind::Assign(
 537                     box(
 538                         end.clone(),
 539                         Rvalue::Use(Operand::Constant(self.make_usize(len)))
 540                     )
 541                 )
 542             )
 543         ];
 544         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 545
 546         // BB #1: loop {
 547         //     BB #2;
 548         //     BB #3;
 549         // }
 550         // BB #4;
 551         self.loop_header(Place::from(beg),
 552                          end,
 553                          BasicBlock::new(2),
 554                          BasicBlock::new(4),
 555                          false);
 556
 557         // BB #2
 558         // `dest[i] = Clone::clone(src[beg])`;
 559         // Goto #3 if ok, #5 if unwinding happens.
 560         let dest_field = self.tcx.mk_place_index(dest.clone(), beg);
 561         let src_field = self.tcx.mk_place_index(src, beg);
 562         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 563                              BasicBlock::new(5));
 564
 565         // BB #3
 566         // `beg = beg + 1;`
 567         // `goto #1`;
 568         let statements = vec![
 569             self.make_statement(
 570                 StatementKind::Assign(
 571                     box(
 572                         Place::from(beg),
 573                         Rvalue::BinaryOp(
 574                             BinOp::Add,
 575                             Operand::Copy(Place::from(beg)),
 576                             Operand::Constant(self.make_usize(1))
 577                         )
 578                     )
 579                 )
 580             )
 581         ];
 582         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 583
 584         // BB #4
 585         // `return dest;`
 586         self.block(vec![], TerminatorKind::Return, false);
 587
 588         // BB #5 (cleanup)
 589         // `let end = beg;`
 590         // `let mut beg = 0;`
 591         // goto #6;
 592         let end = beg;
 593         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 594         let init = self.make_statement(
 595             StatementKind::Assign(
 596                 box(
 597                     Place::from(beg),
 598                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 599                 )
 600             )
 601         );
 602         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 603
 604         // BB #6 (cleanup): loop {
 605         //     BB #7;
 606         //     BB #8;
 607         // }
 608         // BB #9;
 609         self.loop_header(Place::from(beg), Place::from(end),
 610                          BasicBlock::new(7), BasicBlock::new(9), true);
 611
 612         // BB #7 (cleanup)
 613         // `drop(dest[beg])`;
 614         self.block(vec![], TerminatorKind::Drop {
 615             location: self.tcx.mk_place_index(dest, beg),
 616             target: BasicBlock::new(8),
 617             unwind: None,
 618         }, true);
 619
 620         // BB #8 (cleanup)
 621         // `beg = beg + 1;`
 622         // `goto #6;`
 623         let statement = self.make_statement(
 624             StatementKind::Assign(
 625                 box(
 626                     Place::from(beg),
 627                     Rvalue::BinaryOp(
 628                         BinOp::Add,
 629                         Operand::Copy(Place::from(beg)),
 630                         Operand::Constant(self.make_usize(1))
 631                     )
 632                 )
 633             )
 634         );
 635         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 636
 637         // BB #9 (resume)
 638         self.block(vec![], TerminatorKind::Resume, true);
 639     }
 640
 641     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 642                           src: Place<'tcx>, tys: I)
 643             where I: Iterator<Item = Ty<'tcx>> {
 644         let mut previous_field = None;
 645         for (i, ity) in tys.enumerate() {
 646             let field = Field::new(i);
 647             let src_field = self.tcx.mk_place_field(src.clone(), field, ity);
 648
 649             let dest_field = self.tcx.mk_place_field(dest.clone(), field, ity);
 650
 651             // #(2i + 1) is the cleanup block for the previous clone operation
 652             let cleanup_block = self.block_index_offset(1);
 653             // #(2i + 2) is the next cloning block
 654             // (or the Return terminator if this is the last block)
 655             let next_block = self.block_index_offset(2);
 656
 657             // BB #(2i)
 658             // `dest.i = Clone::clone(&src.i);`
 659             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 660             self.make_clone_call(
 661                 dest_field.clone(),
 662                 src_field,
 663                 ity,
 664                 next_block,
 665                 cleanup_block,
 666             );
 667
 668             // BB #(2i + 1) (cleanup)
 669             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 670                 // Drop previous field and goto previous cleanup block.
 671                 self.block(vec![], TerminatorKind::Drop {
 672                     location: previous_field,
 673                     target: previous_cleanup,
 674                     unwind: None,
 675                 }, true);
 676             } else {
 677                 // Nothing to drop, just resume.
 678                 self.block(vec![], TerminatorKind::Resume, true);
 679             }
 680
 681             previous_field = Some((dest_field, cleanup_block));
 682         }
 683
 684         self.block(vec![], TerminatorKind::Return, false);
 685     }
 686 }
 687
 688 /// Builds a "call" shim for `def_id`. The shim calls the
 689 /// function specified by `call_kind`, first adjusting its first
 690 /// argument according to `rcvr_adjustment`.
 691 ///
 692 /// If `untuple_args` is a vec of types, the second argument of the
 693 /// function will be untupled as these types.
 694 fn build_call_shim<'tcx>(
 695     tcx: TyCtxt<'tcx>,
 696     def_id: DefId,
 697     rcvr_adjustment: Adjustment,
 698     call_kind: CallKind,
 699     untuple_args: Option<&[Ty<'tcx>]>,
 700 ) -> Body<'tcx> {
 701     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 702             call_kind={:?}, untuple_args={:?})",
 703            def_id, rcvr_adjustment, call_kind, untuple_args);
 704
 705     let sig = tcx.fn_sig(def_id);
 706     let sig = tcx.erase_late_bound_regions(&sig);
 707     let span = tcx.def_span(def_id);
 708
 709     debug!("build_call_shim: sig={:?}", sig);
 710
 711     let mut local_decls = local_decls_for_sig(&sig, span);
 712     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 713
 714     let rcvr_arg = Local::new(1+0);
 715     let rcvr_l = Place::from(rcvr_arg);
 716     let mut statements = vec![];
 717
 718     let rcvr = match rcvr_adjustment {
 719         Adjustment::Identity => Operand::Move(rcvr_l),
 720         Adjustment::Deref => Operand::Copy(tcx.mk_place_deref(rcvr_l)),
 721         Adjustment::DerefMove => {
 722             // fn(Self, ...) -> fn(*mut Self, ...)
 723             let arg_ty = local_decls[rcvr_arg].ty;
 724             debug_assert!(tcx.generics_of(def_id).has_self && arg_ty == tcx.types.self_param);
 725             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 726
 727             Operand::Move(tcx.mk_place_deref(rcvr_l))
 728         }
 729         Adjustment::RefMut => {
 730             // let rcvr = &mut rcvr;
 731             let ref_rcvr = local_decls.push(temp_decl(
 732                 Mutability::Not,
 733                 tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 734                     ty: sig.inputs()[0],
 735                     mutbl: hir::Mutability::Mutable
 736                 }),
 737                 span
 738             ));
 739             let borrow_kind = BorrowKind::Mut {
 740                 allow_two_phase_borrow: false,
 741             };
 742             statements.push(Statement {
 743                 source_info,
 744                 kind: StatementKind::Assign(
 745                     box(
 746                         Place::from(ref_rcvr),
 747                         Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
 748                     )
 749                 )
 750             });
 751             Operand::Move(Place::from(ref_rcvr))
 752         }
 753     };
 754
 755     let (callee, mut args) = match call_kind {
 756         CallKind::Indirect => (rcvr, vec![]),
 757         CallKind::Direct(def_id) => {
 758             let ty = tcx.type_of(def_id);
 759             (Operand::Constant(box Constant {
 760                 span,
 761                 user_ty: None,
 762                 literal: ty::Const::zero_sized(tcx, ty),
 763              }),
 764              vec![rcvr])
 765         }
 766     };
 767
 768     if let Some(untuple_args) = untuple_args {
 769         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 770             let arg_place = Place::from(Local::new(1+1));
 771             Operand::Move(tcx.mk_place_field(arg_place, Field::new(i), *ity))
 772         }));
 773     } else {
 774         args.extend((1..sig.inputs().len()).map(|i| {
 775             Operand::Move(Place::from(Local::new(1+i)))
 776         }));
 777     }
 778
 779     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 780     let mut blocks = IndexVec::with_capacity(n_blocks);
 781     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 782         blocks.push(BasicBlockData {
 783             statements,
 784             terminator: Some(Terminator { source_info, kind }),
 785             is_cleanup
 786         })
 787     };
 788
 789     // BB #0
 790     block(&mut blocks, statements, TerminatorKind::Call {
 791         func: callee,
 792         args,
 793         destination: Some((Place::return_place(),
 794                            BasicBlock::new(1))),
 795         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 796             Some(BasicBlock::new(3))
 797         } else {
 798             None
 799         },
 800         from_hir_call: true,
 801     }, false);
 802
 803     if let Adjustment::RefMut = rcvr_adjustment {
 804         // BB #1 - drop for Self
 805         block(&mut blocks, vec![], TerminatorKind::Drop {
 806             location: Place::from(rcvr_arg),
 807             target: BasicBlock::new(2),
 808             unwind: None
 809         }, false);
 810     }
 811     // BB #1/#2 - return
 812     block(&mut blocks, vec![], TerminatorKind::Return, false);
 813     if let Adjustment::RefMut = rcvr_adjustment {
 814         // BB #3 - drop if closure panics
 815         block(&mut blocks, vec![], TerminatorKind::Drop {
 816             location: Place::from(rcvr_arg),
 817             target: BasicBlock::new(4),
 818             unwind: None
 819         }, true);
 820
 821         // BB #4 - resume
 822         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 823     }
 824
 825     let mut body = Body::new(
 826         blocks,
 827         IndexVec::from_elem_n(
 828             SourceScopeData { span: span, parent_scope: None }, 1
 829         ),
 830         ClearCrossCrate::Clear,
 831         local_decls,
 832         IndexVec::new(),
 833         sig.inputs().len(),
 834         vec![],
 835         span,
 836         vec![],
 837     );
 838     if let Abi::RustCall = sig.abi {
 839         body.spread_arg = Some(Local::new(sig.inputs().len()));
 840     }
 841     body
 842 }
 843
 844 pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> &Body<'_> {
 845     debug_assert!(tcx.is_constructor(ctor_id));
 846
 847     let span = tcx.hir().span_if_local(ctor_id)
 848         .unwrap_or_else(|| bug!("no span for ctor {:?}", ctor_id));
 849
 850     let param_env = tcx.param_env(ctor_id);
 851
 852     // Normalize the sig.
 853     let sig = tcx.fn_sig(ctor_id)
 854         .no_bound_vars()
 855         .expect("LBR in ADT constructor signature");
 856     let sig = tcx.normalize_erasing_regions(param_env, sig);
 857
 858     let (adt_def, substs) = match sig.output().kind {
 859         ty::Adt(adt_def, substs) => (adt_def, substs),
 860         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 861     };
 862
 863     debug!("build_ctor: ctor_id={:?} sig={:?}", ctor_id, sig);
 864
 865     let local_decls = local_decls_for_sig(&sig, span);
 866
 867     let source_info = SourceInfo {
 868         span,
 869         scope: OUTERMOST_SOURCE_SCOPE
 870     };
 871
 872     let variant_index = if adt_def.is_enum() {
 873         adt_def.variant_index_with_ctor_id(ctor_id)
 874     } else {
 875         VariantIdx::new(0)
 876     };
 877
 878     // Generate the following MIR:
 879     //
 880     // (return as Variant).field0 = arg0;
 881     // (return as Variant).field1 = arg1;
 882     //
 883     // return;
 884     debug!("build_ctor: variant_index={:?}", variant_index);
 885
 886     let statements = expand_aggregate(
 887         Place::return_place(),
 888         adt_def
 889             .variants[variant_index]
 890             .fields
 891             .iter()
 892             .enumerate()
 893             .map(|(idx, field_def)| (
 894                 Operand::Move(Place::from(Local::new(idx + 1))),
 895                 field_def.ty(tcx, substs),
 896             )),
 897         AggregateKind::Adt(adt_def, variant_index, substs, None, None),
 898         source_info,
 899         tcx,
 900     ).collect();
 901
 902     let start_block = BasicBlockData {
 903         statements,
 904         terminator: Some(Terminator {
 905             source_info,
 906             kind: TerminatorKind::Return,
 907         }),
 908         is_cleanup: false
 909     };
 910
 911     let body = Body::new(
 912         IndexVec::from_elem_n(start_block, 1),
 913         IndexVec::from_elem_n(
 914             SourceScopeData { span: span, parent_scope: None }, 1
 915         ),
 916         ClearCrossCrate::Clear,
 917         local_decls,
 918         IndexVec::new(),
 919         sig.inputs().len(),
 920         vec![],
 921         span,
 922         vec![],
 923     );
 924
 925     crate::util::dump_mir(
 926         tcx,
 927         None,
 928         "mir_map",
 929         &0,
 930         crate::transform::MirSource::item(ctor_id),
 931         &body,
 932         |_, _| Ok(()),
 933     );
 934
 935     tcx.arena.alloc(body)
 936 }