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