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.moves_by_default(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: ty::Const::zero_sized(self.tcx, func_ty),
 463         });
 464
 465         let ref_loc = self.make_place(
 466             Mutability::Not,
 467             tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 468                 ty,
 469                 mutbl: hir::Mutability::MutImmutable,
 470             })
 471         );
 472
 473         // `let ref_loc: &ty = &src;`
 474         let statement = self.make_statement(
 475             StatementKind::Assign(
 476                 ref_loc.clone(),
 477                 box Rvalue::Ref(tcx.types.re_erased, BorrowKind::Shared, src)
 478             )
 479         );
 480
 481         // `let loc = Clone::clone(ref_loc);`
 482         self.block(vec![statement], TerminatorKind::Call {
 483             func,
 484             args: vec![Operand::Move(ref_loc)],
 485             destination: Some((dest, next)),
 486             cleanup: Some(cleanup),
 487             from_hir_call: true,
 488         }, false);
 489     }
 490
 491     fn loop_header(
 492         &mut self,
 493         beg: Place<'tcx>,
 494         end: Place<'tcx>,
 495         loop_body: BasicBlock,
 496         loop_end: BasicBlock,
 497         is_cleanup: bool
 498     ) {
 499         let tcx = self.tcx;
 500
 501         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 502         let compute_cond = self.make_statement(
 503             StatementKind::Assign(
 504                 cond.clone(),
 505                 box Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 506             )
 507         );
 508
 509         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 510         self.block(
 511             vec![compute_cond],
 512             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 513             is_cleanup
 514         );
 515     }
 516
 517     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 518         box Constant {
 519             span: self.span,
 520             ty: self.tcx.types.usize,
 521             user_ty: None,
 522             literal: ty::Const::from_usize(self.tcx, value),
 523         }
 524     }
 525
 526     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 527         let tcx = self.tcx;
 528         let span = self.span;
 529
 530         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 531         let end = self.make_place(Mutability::Not, tcx.types.usize);
 532
 533         // BB #0
 534         // `let mut beg = 0;`
 535         // `let end = len;`
 536         // `goto #1;`
 537         let inits = vec![
 538             self.make_statement(
 539                 StatementKind::Assign(
 540                     Place::Local(beg),
 541                     box Rvalue::Use(Operand::Constant(self.make_usize(0)))
 542                 )
 543             ),
 544             self.make_statement(
 545                 StatementKind::Assign(
 546                     end.clone(),
 547                     box Rvalue::Use(Operand::Constant(self.make_usize(len)))
 548                 )
 549             )
 550         ];
 551         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 552
 553         // BB #1: loop {
 554         //     BB #2;
 555         //     BB #3;
 556         // }
 557         // BB #4;
 558         self.loop_header(Place::Local(beg), end, BasicBlock::new(2), BasicBlock::new(4), false);
 559
 560         // BB #2
 561         // `dest[i] = Clone::clone(src[beg])`;
 562         // Goto #3 if ok, #5 if unwinding happens.
 563         let dest_field = dest.clone().index(beg);
 564         let src_field = src.index(beg);
 565         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 566                              BasicBlock::new(5));
 567
 568         // BB #3
 569         // `beg = beg + 1;`
 570         // `goto #1`;
 571         let statements = vec![
 572             self.make_statement(
 573                 StatementKind::Assign(
 574                     Place::Local(beg),
 575                     box Rvalue::BinaryOp(
 576                         BinOp::Add,
 577                         Operand::Copy(Place::Local(beg)),
 578                         Operand::Constant(self.make_usize(1))
 579                     )
 580                 )
 581             )
 582         ];
 583         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 584
 585         // BB #4
 586         // `return dest;`
 587         self.block(vec![], TerminatorKind::Return, false);
 588
 589         // BB #5 (cleanup)
 590         // `let end = beg;`
 591         // `let mut beg = 0;`
 592         // goto #6;
 593         let end = beg;
 594         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 595         let init = self.make_statement(
 596             StatementKind::Assign(
 597                 Place::Local(beg),
 598                 box Rvalue::Use(Operand::Constant(self.make_usize(0)))
 599             )
 600         );
 601         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 602
 603         // BB #6 (cleanup): loop {
 604         //     BB #7;
 605         //     BB #8;
 606         // }
 607         // BB #9;
 608         self.loop_header(Place::Local(beg), Place::Local(end),
 609                          BasicBlock::new(7), BasicBlock::new(9), true);
 610
 611         // BB #7 (cleanup)
 612         // `drop(dest[beg])`;
 613         self.block(vec![], TerminatorKind::Drop {
 614             location: dest.index(beg),
 615             target: BasicBlock::new(8),
 616             unwind: None,
 617         }, true);
 618
 619         // BB #8 (cleanup)
 620         // `beg = beg + 1;`
 621         // `goto #6;`
 622         let statement = self.make_statement(
 623             StatementKind::Assign(
 624                 Place::Local(beg),
 625                 box Rvalue::BinaryOp(
 626                     BinOp::Add,
 627                     Operand::Copy(Place::Local(beg)),
 628                     Operand::Constant(self.make_usize(1))
 629                 )
 630             )
 631         );
 632         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 633
 634         // BB #9 (resume)
 635         self.block(vec![], TerminatorKind::Resume, true);
 636     }
 637
 638     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 639                           src: Place<'tcx>, tys: I)
 640             where I: Iterator<Item = ty::Ty<'tcx>> {
 641         let mut previous_field = None;
 642         for (i, ity) in tys.enumerate() {
 643             let field = Field::new(i);
 644             let src_field = src.clone().field(field, ity);
 645
 646             let dest_field = dest.clone().field(field, ity);
 647
 648             // #(2i + 1) is the cleanup block for the previous clone operation
 649             let cleanup_block = self.block_index_offset(1);
 650             // #(2i + 2) is the next cloning block
 651             // (or the Return terminator if this is the last block)
 652             let next_block = self.block_index_offset(2);
 653
 654             // BB #(2i)
 655             // `dest.i = Clone::clone(&src.i);`
 656             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 657             self.make_clone_call(
 658                 dest_field.clone(),
 659                 src_field,
 660                 ity,
 661                 next_block,
 662                 cleanup_block,
 663             );
 664
 665             // BB #(2i + 1) (cleanup)
 666             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 667                 // Drop previous field and goto previous cleanup block.
 668                 self.block(vec![], TerminatorKind::Drop {
 669                     location: previous_field,
 670                     target: previous_cleanup,
 671                     unwind: None,
 672                 }, true);
 673             } else {
 674                 // Nothing to drop, just resume.
 675                 self.block(vec![], TerminatorKind::Resume, true);
 676             }
 677
 678             previous_field = Some((dest_field, cleanup_block));
 679         }
 680
 681         self.block(vec![], TerminatorKind::Return, false);
 682     }
 683 }
 684
 685 /// Build a "call" shim for `def_id`. The shim calls the
 686 /// function specified by `call_kind`, first adjusting its first
 687 /// argument according to `rcvr_adjustment`.
 688 ///
 689 /// If `untuple_args` is a vec of types, the second argument of the
 690 /// function will be untupled as these types.
 691 fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 692                              def_id: DefId,
 693                              rcvr_adjustment: Adjustment,
 694                              call_kind: CallKind,
 695                              untuple_args: Option<&[Ty<'tcx>]>)
 696                              -> Mir<'tcx>
 697 {
 698     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 699             call_kind={:?}, untuple_args={:?})",
 700            def_id, rcvr_adjustment, call_kind, untuple_args);
 701
 702     let sig = tcx.fn_sig(def_id);
 703     let sig = tcx.erase_late_bound_regions(&sig);
 704     let span = tcx.def_span(def_id);
 705
 706     debug!("build_call_shim: sig={:?}", sig);
 707
 708     let mut local_decls = local_decls_for_sig(&sig, span);
 709     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 710
 711     let rcvr_arg = Local::new(1+0);
 712     let rcvr_l = Place::Local(rcvr_arg);
 713     let mut statements = vec![];
 714
 715     let rcvr = match rcvr_adjustment {
 716         Adjustment::Identity => Operand::Move(rcvr_l),
 717         Adjustment::Deref => Operand::Copy(rcvr_l.deref()),
 718         Adjustment::DerefMove => {
 719             // fn(Self, ...) -> fn(*mut Self, ...)
 720             let arg_ty = local_decls[rcvr_arg].ty;
 721             assert!(arg_ty.is_self());
 722             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 723
 724             Operand::Move(rcvr_l.deref())
 725         }
 726         Adjustment::RefMut => {
 727             // let rcvr = &mut rcvr;
 728             let ref_rcvr = local_decls.push(temp_decl(
 729                 Mutability::Not,
 730                 tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 731                     ty: sig.inputs()[0],
 732                     mutbl: hir::Mutability::MutMutable
 733                 }),
 734                 span
 735             ));
 736             let borrow_kind = BorrowKind::Mut {
 737                 allow_two_phase_borrow: false,
 738             };
 739             statements.push(Statement {
 740                 source_info,
 741                 kind: StatementKind::Assign(
 742                     Place::Local(ref_rcvr),
 743                     box Rvalue::Ref(tcx.types.re_erased, borrow_kind, rcvr_l)
 744                 )
 745             });
 746             Operand::Move(Place::Local(ref_rcvr))
 747         }
 748     };
 749
 750     let (callee, mut args) = match call_kind {
 751         CallKind::Indirect => (rcvr, vec![]),
 752         CallKind::Direct(def_id) => {
 753             let ty = tcx.type_of(def_id);
 754             (Operand::Constant(box Constant {
 755                 span,
 756                 ty,
 757                 user_ty: None,
 758                 literal: ty::Const::zero_sized(tcx, ty),
 759              }),
 760              vec![rcvr])
 761         }
 762     };
 763
 764     if let Some(untuple_args) = untuple_args {
 765         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 766             let arg_place = Place::Local(Local::new(1+1));
 767             Operand::Move(arg_place.field(Field::new(i), *ity))
 768         }));
 769     } else {
 770         args.extend((1..sig.inputs().len()).map(|i| {
 771             Operand::Move(Place::Local(Local::new(1+i)))
 772         }));
 773     }
 774
 775     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 776     let mut blocks = IndexVec::with_capacity(n_blocks);
 777     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 778         blocks.push(BasicBlockData {
 779             statements,
 780             terminator: Some(Terminator { source_info, kind }),
 781             is_cleanup
 782         })
 783     };
 784
 785     // BB #0
 786     block(&mut blocks, statements, TerminatorKind::Call {
 787         func: callee,
 788         args,
 789         destination: Some((Place::Local(RETURN_PLACE),
 790                            BasicBlock::new(1))),
 791         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 792             Some(BasicBlock::new(3))
 793         } else {
 794             None
 795         },
 796         from_hir_call: true,
 797     }, false);
 798
 799     if let Adjustment::RefMut = rcvr_adjustment {
 800         // BB #1 - drop for Self
 801         block(&mut blocks, vec![], TerminatorKind::Drop {
 802             location: Place::Local(rcvr_arg),
 803             target: BasicBlock::new(2),
 804             unwind: None
 805         }, false);
 806     }
 807     // BB #1/#2 - return
 808     block(&mut blocks, vec![], TerminatorKind::Return, false);
 809     if let Adjustment::RefMut = rcvr_adjustment {
 810         // BB #3 - drop if closure panics
 811         block(&mut blocks, vec![], TerminatorKind::Drop {
 812             location: Place::Local(rcvr_arg),
 813             target: BasicBlock::new(4),
 814             unwind: None
 815         }, true);
 816
 817         // BB #4 - resume
 818         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 819     }
 820
 821     let mut mir = Mir::new(
 822         blocks,
 823         IndexVec::from_elem_n(
 824             SourceScopeData { span: span, parent_scope: None }, 1
 825         ),
 826         ClearCrossCrate::Clear,
 827         IndexVec::new(),
 828         None,
 829         local_decls,
 830         IndexVec::new(),
 831         sig.inputs().len(),
 832         vec![],
 833         span,
 834         vec![],
 835     );
 836     if let Abi::RustCall = sig.abi {
 837         mir.spread_arg = Some(Local::new(sig.inputs().len()));
 838     }
 839     mir
 840 }
 841
 842 pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
 843                                       ctor_id: ast::NodeId,
 844                                       fields: &[hir::StructField],
 845                                       span: Span)
 846                                       -> Mir<'tcx>
 847 {
 848     let tcx = infcx.tcx;
 849     let gcx = tcx.global_tcx();
 850     let def_id = tcx.hir().local_def_id(ctor_id);
 851     let param_env = gcx.param_env(def_id);
 852
 853     // Normalize the sig.
 854     let sig = gcx.fn_sig(def_id)
 855         .no_bound_vars()
 856         .expect("LBR in ADT constructor signature");
 857     let sig = gcx.normalize_erasing_regions(param_env, sig);
 858
 859     let (adt_def, substs) = match sig.output().sty {
 860         ty::Adt(adt_def, substs) => (adt_def, substs),
 861         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 862     };
 863
 864     debug!("build_ctor: def_id={:?} sig={:?} fields={:?}", def_id, sig, fields);
 865
 866     let local_decls = local_decls_for_sig(&sig, span);
 867
 868     let source_info = SourceInfo {
 869         span,
 870         scope: OUTERMOST_SOURCE_SCOPE
 871     };
 872
 873     let variant_no = if adt_def.is_enum() {
 874         adt_def.variant_index_with_id(def_id)
 875     } else {
 876         VariantIdx::new(0)
 877     };
 878
 879     // return = ADT(arg0, arg1, ...); return
 880     let start_block = BasicBlockData {
 881         statements: vec![Statement {
 882             source_info,
 883             kind: StatementKind::Assign(
 884                 Place::Local(RETURN_PLACE),
 885                 box Rvalue::Aggregate(
 886                     box AggregateKind::Adt(adt_def, variant_no, substs, None, None),
 887                     (1..sig.inputs().len()+1).map(|i| {
 888                         Operand::Move(Place::Local(Local::new(i)))
 889                     }).collect()
 890                 )
 891             )
 892         }],
 893         terminator: Some(Terminator {
 894             source_info,
 895             kind: TerminatorKind::Return,
 896         }),
 897         is_cleanup: false
 898     };
 899
 900     Mir::new(
 901         IndexVec::from_elem_n(start_block, 1),
 902         IndexVec::from_elem_n(
 903             SourceScopeData { span: span, parent_scope: None }, 1
 904         ),
 905         ClearCrossCrate::Clear,
 906         IndexVec::new(),
 907         None,
 908         local_decls,
 909         IndexVec::new(),
 910         sig.inputs().len(),
 911         vec![],
 912         span,
 913         vec![],
 914     )
 915 }