src/librustc_mir/shim.rs

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