src/librustc_mir/shim.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use rustc::hir;
  12 use rustc::hir::def_id::DefId;
  13 use rustc::infer;
  14 use rustc::mir::*;
  15 use rustc::ty::{self, Ty, TyCtxt, GenericParamDefKind};
  16 use rustc::ty::subst::{Subst, Substs};
  17 use rustc::ty::query::Providers;
  18
  19 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
  20
  21 use rustc_target::spec::abi::Abi;
  22 use syntax::ast;
  23 use syntax_pos::Span;
  24
  25 use std::fmt;
  26 use std::iter;
  27
  28 use transform::{add_moves_for_packed_drops, add_call_guards};
  29 use transform::{remove_noop_landing_pads, no_landing_pads, simplify};
  30 use util::elaborate_drops::{self, DropElaborator, DropStyle, DropFlagMode};
  31 use util::patch::MirPatch;
  32
  33 pub fn provide(providers: &mut Providers) {
  34     providers.mir_shims = make_shim;
  35 }
  36
  37 fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  38                        instance: ty::InstanceDef<'tcx>)
  39                        -> &'tcx Mir<'tcx>
  40 {
  41     debug!("make_shim({:?})", instance);
  42
  43     let mut result = match instance {
  44         ty::InstanceDef::Item(..) =>
  45             bug!("item {:?} passed to make_shim", instance),
  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     RefMut,
 132 }
 133
 134 #[derive(Copy, Clone, Debug, PartialEq)]
 135 enum CallKind {
 136     Indirect,
 137     Direct(DefId),
 138 }
 139
 140 fn temp_decl(mutability: Mutability, ty: Ty, span: Span) -> LocalDecl {
 141     let source_info = SourceInfo { scope: OUTERMOST_SOURCE_SCOPE, span };
 142     LocalDecl {
 143         mutability, ty, name: None,
 144         source_info,
 145         visibility_scope: source_info.scope,
 146         internal: false,
 147         is_user_variable: None,
 148     }
 149 }
 150
 151 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 152     -> IndexVec<Local, LocalDecl<'tcx>>
 153 {
 154     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 155         .chain(sig.inputs().iter().map(
 156             |ity| temp_decl(Mutability::Not, ity, span)))
 157         .collect()
 158 }
 159
 160 fn build_drop_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 161                              def_id: DefId,
 162                              ty: Option<Ty<'tcx>>)
 163                              -> Mir<'tcx>
 164 {
 165     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 166
 167     // Check if this is a generator, if so, return the drop glue for it
 168     if let Some(&ty::TyS { sty: ty::Generator(gen_def_id, substs, _), .. }) = ty {
 169         let mir = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 170         return mir.subst(tcx, substs.substs);
 171     }
 172
 173     let substs = if let Some(ty) = ty {
 174         tcx.intern_substs(&[ty.into()])
 175     } else {
 176         Substs::identity_for_item(tcx, def_id)
 177     };
 178     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 179     let sig = tcx.erase_late_bound_regions(&sig);
 180     let span = tcx.def_span(def_id);
 181
 182     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 183
 184     let return_block = BasicBlock::new(1);
 185     let mut blocks = IndexVec::new();
 186     let block = |blocks: &mut IndexVec<_, _>, kind| {
 187         blocks.push(BasicBlockData {
 188             statements: vec![],
 189             terminator: Some(Terminator { source_info, kind }),
 190             is_cleanup: false
 191         })
 192     };
 193     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 194     block(&mut blocks, TerminatorKind::Return);
 195
 196     let mut mir = Mir::new(
 197         blocks,
 198         IndexVec::from_elem_n(
 199             SourceScopeData { span: span, parent_scope: None }, 1
 200         ),
 201         ClearCrossCrate::Clear,
 202         IndexVec::new(),
 203         None,
 204         local_decls_for_sig(&sig, span),
 205         sig.inputs().len(),
 206         vec![],
 207         span
 208     );
 209
 210     if let Some(..) = ty {
 211         let patch = {
 212             let param_env = tcx.param_env(def_id).with_reveal_all();
 213             let mut elaborator = DropShimElaborator {
 214                 mir: &mir,
 215                 patch: MirPatch::new(&mir),
 216                 tcx,
 217                 param_env
 218             };
 219             let dropee = Place::Local(Local::new(1+0)).deref();
 220             let resume_block = elaborator.patch.resume_block();
 221             elaborate_drops::elaborate_drop(
 222                 &mut elaborator,
 223                 source_info,
 224                 &dropee,
 225                 (),
 226                 return_block,
 227                 elaborate_drops::Unwind::To(resume_block),
 228                 START_BLOCK
 229             );
 230             elaborator.patch
 231         };
 232         patch.apply(&mut mir);
 233     }
 234
 235     mir
 236 }
 237
 238 pub struct DropShimElaborator<'a, 'tcx: 'a> {
 239     pub mir: &'a Mir<'tcx>,
 240     pub patch: MirPatch<'tcx>,
 241     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
 242     pub param_env: ty::ParamEnv<'tcx>,
 243 }
 244
 245 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 246     fn fmt(&self, _f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 247         Ok(())
 248     }
 249 }
 250
 251 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 252     type Path = ();
 253
 254     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 255     fn mir(&self) -> &'a Mir<'tcx> { self.mir }
 256     fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx> { self.tcx }
 257     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 258
 259     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 260         if let DropFlagMode::Shallow = mode {
 261             DropStyle::Static
 262         } else {
 263             DropStyle::Open
 264         }
 265     }
 266
 267     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 268         None
 269     }
 270
 271     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 272     }
 273
 274     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 275         None
 276     }
 277     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 278         None
 279     }
 280     fn downcast_subpath(&self, _path: Self::Path, _variant: usize) -> Option<Self::Path> {
 281         Some(())
 282     }
 283     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 284         None
 285     }
 286 }
 287
 288 /// Build a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 289 fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 290                               def_id: DefId,
 291                               self_ty: Ty<'tcx>)
 292                               -> Mir<'tcx>
 293 {
 294     debug!("build_clone_shim(def_id={:?})", def_id);
 295
 296     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 297     let is_copy = !self_ty.moves_by_default(tcx, tcx.param_env(def_id), builder.span);
 298
 299     let dest = Place::Local(RETURN_PLACE);
 300     let src = Place::Local(Local::new(1+0)).deref();
 301
 302     match self_ty.sty {
 303         _ if is_copy => builder.copy_shim(),
 304         ty::Array(ty, len) => {
 305             let len = len.unwrap_usize(tcx);
 306             builder.array_shim(dest, src, ty, len)
 307         }
 308         ty::Closure(def_id, substs) => {
 309             builder.tuple_like_shim(
 310                 dest, src,
 311                 substs.upvar_tys(def_id, tcx)
 312             )
 313         }
 314         ty::Tuple(tys) => builder.tuple_like_shim(dest, src, tys.iter().cloned()),
 315         _ => {
 316             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 317         }
 318     };
 319
 320     builder.into_mir()
 321 }
 322
 323 struct CloneShimBuilder<'a, 'tcx: 'a> {
 324     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 325     def_id: DefId,
 326     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 327     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 328     span: Span,
 329     sig: ty::FnSig<'tcx>,
 330 }
 331
 332 impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
 333     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 334            def_id: DefId,
 335            self_ty: Ty<'tcx>) -> Self {
 336         // we must subst the self_ty because it's
 337         // otherwise going to be TySelf and we can't index
 338         // or access fields of a Place of type TySelf.
 339         let substs = tcx.mk_substs_trait(self_ty, &[]);
 340         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 341         let sig = tcx.erase_late_bound_regions(&sig);
 342         let span = tcx.def_span(def_id);
 343
 344         CloneShimBuilder {
 345             tcx,
 346             def_id,
 347             local_decls: local_decls_for_sig(&sig, span),
 348             blocks: IndexVec::new(),
 349             span,
 350             sig,
 351         }
 352     }
 353
 354     fn into_mir(self) -> Mir<'tcx> {
 355         Mir::new(
 356             self.blocks,
 357             IndexVec::from_elem_n(
 358                 SourceScopeData { span: self.span, parent_scope: None }, 1
 359             ),
 360             ClearCrossCrate::Clear,
 361             IndexVec::new(),
 362             None,
 363             self.local_decls,
 364             self.sig.inputs().len(),
 365             vec![],
 366             self.span
 367         )
 368     }
 369
 370     fn source_info(&self) -> SourceInfo {
 371         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 372     }
 373
 374     fn block(
 375         &mut self,
 376         statements: Vec<Statement<'tcx>>,
 377         kind: TerminatorKind<'tcx>,
 378         is_cleanup: bool
 379     ) -> BasicBlock {
 380         let source_info = self.source_info();
 381         self.blocks.push(BasicBlockData {
 382             statements,
 383             terminator: Some(Terminator { source_info, kind }),
 384             is_cleanup,
 385         })
 386     }
 387
 388     /// Gives the index of an upcoming BasicBlock, with an offset.
 389     /// offset=0 will give you the index of the next BasicBlock,
 390     /// offset=1 will give the index of the next-to-next block,
 391     /// offset=-1 will give you the index of the last-created block
 392     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 393         BasicBlock::new(self.blocks.len() + offset)
 394     }
 395
 396     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 397         Statement {
 398             source_info: self.source_info(),
 399             kind,
 400         }
 401     }
 402
 403     fn copy_shim(&mut self) {
 404         let rcvr = Place::Local(Local::new(1+0)).deref();
 405         let ret_statement = self.make_statement(
 406             StatementKind::Assign(
 407                 Place::Local(RETURN_PLACE),
 408                 Rvalue::Use(Operand::Copy(rcvr))
 409             )
 410         );
 411         self.block(vec![ret_statement], TerminatorKind::Return, false);
 412     }
 413
 414     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 415         let span = self.span;
 416         Place::Local(
 417             self.local_decls.push(temp_decl(mutability, ty, span))
 418         )
 419     }
 420
 421     fn make_clone_call(
 422         &mut self,
 423         dest: Place<'tcx>,
 424         src: Place<'tcx>,
 425         ty: Ty<'tcx>,
 426         next: BasicBlock,
 427         cleanup: BasicBlock
 428     ) {
 429         let tcx = self.tcx;
 430
 431         let substs = Substs::for_item(tcx, self.def_id, |param, _| {
 432             match param.kind {
 433                 GenericParamDefKind::Lifetime => tcx.types.re_erased.into(),
 434                 GenericParamDefKind::Type {..} => ty.into(),
 435             }
 436         });
 437
 438         // `func == Clone::clone(&ty) -> ty`
 439         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 440         let func = Operand::Constant(box Constant {
 441             span: self.span,
 442             ty: func_ty,
 443             literal: ty::Const::zero_sized(self.tcx, func_ty),
 444         });
 445
 446         let ref_loc = self.make_place(
 447             Mutability::Not,
 448             tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 449                 ty,
 450                 mutbl: hir::Mutability::MutImmutable,
 451             })
 452         );
 453
 454         // `let ref_loc: &ty = &src;`
 455         let statement = self.make_statement(
 456             StatementKind::Assign(
 457                 ref_loc.clone(),
 458                 Rvalue::Ref(tcx.types.re_erased, BorrowKind::Shared, src)
 459             )
 460         );
 461
 462         // `let loc = Clone::clone(ref_loc);`
 463         self.block(vec![statement], TerminatorKind::Call {
 464             func,
 465             args: vec![Operand::Move(ref_loc)],
 466             destination: Some((dest, next)),
 467             cleanup: Some(cleanup),
 468         }, false);
 469     }
 470
 471     fn loop_header(
 472         &mut self,
 473         beg: Place<'tcx>,
 474         end: Place<'tcx>,
 475         loop_body: BasicBlock,
 476         loop_end: BasicBlock,
 477         is_cleanup: bool
 478     ) {
 479         let tcx = self.tcx;
 480
 481         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 482         let compute_cond = self.make_statement(
 483             StatementKind::Assign(
 484                 cond.clone(),
 485                 Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 486             )
 487         );
 488
 489         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 490         self.block(
 491             vec![compute_cond],
 492             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 493             is_cleanup
 494         );
 495     }
 496
 497     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 498         box Constant {
 499             span: self.span,
 500             ty: self.tcx.types.usize,
 501             literal: ty::Const::from_usize(self.tcx, value),
 502         }
 503     }
 504
 505     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 506         let tcx = self.tcx;
 507         let span = self.span;
 508
 509         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 510         let end = self.make_place(Mutability::Not, tcx.types.usize);
 511
 512         // BB #0
 513         // `let mut beg = 0;`
 514         // `let end = len;`
 515         // `goto #1;`
 516         let inits = vec![
 517             self.make_statement(
 518                 StatementKind::Assign(
 519                     Place::Local(beg),
 520                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 521                 )
 522             ),
 523             self.make_statement(
 524                 StatementKind::Assign(
 525                     end.clone(),
 526                     Rvalue::Use(Operand::Constant(self.make_usize(len)))
 527                 )
 528             )
 529         ];
 530         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 531
 532         // BB #1: loop {
 533         //     BB #2;
 534         //     BB #3;
 535         // }
 536         // BB #4;
 537         self.loop_header(Place::Local(beg), end, BasicBlock::new(2), BasicBlock::new(4), false);
 538
 539         // BB #2
 540         // `dest[i] = Clone::clone(src[beg])`;
 541         // Goto #3 if ok, #5 if unwinding happens.
 542         let dest_field = dest.clone().index(beg);
 543         let src_field = src.clone().index(beg);
 544         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 545                              BasicBlock::new(5));
 546
 547         // BB #3
 548         // `beg = beg + 1;`
 549         // `goto #1`;
 550         let statements = vec![
 551             self.make_statement(
 552                 StatementKind::Assign(
 553                     Place::Local(beg),
 554                     Rvalue::BinaryOp(
 555                         BinOp::Add,
 556                         Operand::Copy(Place::Local(beg)),
 557                         Operand::Constant(self.make_usize(1))
 558                     )
 559                 )
 560             )
 561         ];
 562         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 563
 564         // BB #4
 565         // `return dest;`
 566         self.block(vec![], TerminatorKind::Return, false);
 567
 568         // BB #5 (cleanup)
 569         // `let end = beg;`
 570         // `let mut beg = 0;`
 571         // goto #6;
 572         let end = beg;
 573         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 574         let init = self.make_statement(
 575             StatementKind::Assign(
 576                 Place::Local(beg),
 577                 Rvalue::Use(Operand::Constant(self.make_usize(0)))
 578             )
 579         );
 580         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 581
 582         // BB #6 (cleanup): loop {
 583         //     BB #7;
 584         //     BB #8;
 585         // }
 586         // BB #9;
 587         self.loop_header(Place::Local(beg), Place::Local(end),
 588                          BasicBlock::new(7), BasicBlock::new(9), true);
 589
 590         // BB #7 (cleanup)
 591         // `drop(dest[beg])`;
 592         self.block(vec![], TerminatorKind::Drop {
 593             location: dest.index(beg),
 594             target: BasicBlock::new(8),
 595             unwind: None,
 596         }, true);
 597
 598         // BB #8 (cleanup)
 599         // `beg = beg + 1;`
 600         // `goto #6;`
 601         let statement = self.make_statement(
 602             StatementKind::Assign(
 603                 Place::Local(beg),
 604                 Rvalue::BinaryOp(
 605                     BinOp::Add,
 606                     Operand::Copy(Place::Local(beg)),
 607                     Operand::Constant(self.make_usize(1))
 608                 )
 609             )
 610         );
 611         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 612
 613         // BB #9 (resume)
 614         self.block(vec![], TerminatorKind::Resume, true);
 615     }
 616
 617     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 618                           src: Place<'tcx>, tys: I)
 619             where I: Iterator<Item = ty::Ty<'tcx>> {
 620         let mut previous_field = None;
 621         for (i, ity) in tys.enumerate() {
 622             let field = Field::new(i);
 623             let src_field = src.clone().field(field, ity);
 624
 625             let dest_field = dest.clone().field(field, ity);
 626
 627             // #(2i + 1) is the cleanup block for the previous clone operation
 628             let cleanup_block = self.block_index_offset(1);
 629             // #(2i + 2) is the next cloning block
 630             // (or the Return terminator if this is the last block)
 631             let next_block = self.block_index_offset(2);
 632
 633             // BB #(2i)
 634             // `dest.i = Clone::clone(&src.i);`
 635             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 636             self.make_clone_call(
 637                 dest_field.clone(),
 638                 src_field,
 639                 ity,
 640                 next_block,
 641                 cleanup_block,
 642             );
 643
 644             // BB #(2i + 1) (cleanup)
 645             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 646                 // Drop previous field and goto previous cleanup block.
 647                 self.block(vec![], TerminatorKind::Drop {
 648                     location: previous_field,
 649                     target: previous_cleanup,
 650                     unwind: None,
 651                 }, true);
 652             } else {
 653                 // Nothing to drop, just resume.
 654                 self.block(vec![], TerminatorKind::Resume, true);
 655             }
 656
 657             previous_field = Some((dest_field, cleanup_block));
 658         }
 659
 660         self.block(vec![], TerminatorKind::Return, false);
 661     }
 662 }
 663
 664 /// Build a "call" shim for `def_id`. The shim calls the
 665 /// function specified by `call_kind`, first adjusting its first
 666 /// argument according to `rcvr_adjustment`.
 667 ///
 668 /// If `untuple_args` is a vec of types, the second argument of the
 669 /// function will be untupled as these types.
 670 fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 671                              def_id: DefId,
 672                              rcvr_adjustment: Adjustment,
 673                              call_kind: CallKind,
 674                              untuple_args: Option<&[Ty<'tcx>]>)
 675                              -> Mir<'tcx>
 676 {
 677     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 678             call_kind={:?}, untuple_args={:?})",
 679            def_id, rcvr_adjustment, call_kind, untuple_args);
 680
 681     let sig = tcx.fn_sig(def_id);
 682     let sig = tcx.erase_late_bound_regions(&sig);
 683     let span = tcx.def_span(def_id);
 684
 685     debug!("build_call_shim: sig={:?}", sig);
 686
 687     let mut local_decls = local_decls_for_sig(&sig, span);
 688     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 689
 690     let rcvr_arg = Local::new(1+0);
 691     let rcvr_l = Place::Local(rcvr_arg);
 692     let mut statements = vec![];
 693
 694     let rcvr = match rcvr_adjustment {
 695         Adjustment::Identity => Operand::Move(rcvr_l),
 696         Adjustment::Deref => Operand::Copy(rcvr_l.deref()),
 697         Adjustment::RefMut => {
 698             // let rcvr = &mut rcvr;
 699             let ref_rcvr = local_decls.push(temp_decl(
 700                 Mutability::Not,
 701                 tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 702                     ty: sig.inputs()[0],
 703                     mutbl: hir::Mutability::MutMutable
 704                 }),
 705                 span
 706             ));
 707             let borrow_kind = BorrowKind::Mut {
 708                 allow_two_phase_borrow: false,
 709             };
 710             statements.push(Statement {
 711                 source_info,
 712                 kind: StatementKind::Assign(
 713                     Place::Local(ref_rcvr),
 714                     Rvalue::Ref(tcx.types.re_erased, borrow_kind, rcvr_l)
 715                 )
 716             });
 717             Operand::Move(Place::Local(ref_rcvr))
 718         }
 719     };
 720
 721     let (callee, mut args) = match call_kind {
 722         CallKind::Indirect => (rcvr, vec![]),
 723         CallKind::Direct(def_id) => {
 724             let ty = tcx.type_of(def_id);
 725             (Operand::Constant(box Constant {
 726                 span,
 727                 ty,
 728                 literal: ty::Const::zero_sized(tcx, ty),
 729              }),
 730              vec![rcvr])
 731         }
 732     };
 733
 734     if let Some(untuple_args) = untuple_args {
 735         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 736             let arg_place = Place::Local(Local::new(1+1));
 737             Operand::Move(arg_place.field(Field::new(i), *ity))
 738         }));
 739     } else {
 740         args.extend((1..sig.inputs().len()).map(|i| {
 741             Operand::Move(Place::Local(Local::new(1+i)))
 742         }));
 743     }
 744
 745     let mut blocks = IndexVec::new();
 746     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 747         blocks.push(BasicBlockData {
 748             statements,
 749             terminator: Some(Terminator { source_info, kind }),
 750             is_cleanup
 751         })
 752     };
 753
 754     // BB #0
 755     block(&mut blocks, statements, TerminatorKind::Call {
 756         func: callee,
 757         args,
 758         destination: Some((Place::Local(RETURN_PLACE),
 759                            BasicBlock::new(1))),
 760         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 761             Some(BasicBlock::new(3))
 762         } else {
 763             None
 764         }
 765     }, false);
 766
 767     if let Adjustment::RefMut = rcvr_adjustment {
 768         // BB #1 - drop for Self
 769         block(&mut blocks, vec![], TerminatorKind::Drop {
 770             location: Place::Local(rcvr_arg),
 771             target: BasicBlock::new(2),
 772             unwind: None
 773         }, false);
 774     }
 775     // BB #1/#2 - return
 776     block(&mut blocks, vec![], TerminatorKind::Return, false);
 777     if let Adjustment::RefMut = rcvr_adjustment {
 778         // BB #3 - drop if closure panics
 779         block(&mut blocks, vec![], TerminatorKind::Drop {
 780             location: Place::Local(rcvr_arg),
 781             target: BasicBlock::new(4),
 782             unwind: None
 783         }, true);
 784
 785         // BB #4 - resume
 786         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 787     }
 788
 789     let mut mir = Mir::new(
 790         blocks,
 791         IndexVec::from_elem_n(
 792             SourceScopeData { span: span, parent_scope: None }, 1
 793         ),
 794         ClearCrossCrate::Clear,
 795         IndexVec::new(),
 796         None,
 797         local_decls,
 798         sig.inputs().len(),
 799         vec![],
 800         span
 801     );
 802     if let Abi::RustCall = sig.abi {
 803         mir.spread_arg = Some(Local::new(sig.inputs().len()));
 804     }
 805     mir
 806 }
 807
 808 pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
 809                                       ctor_id: ast::NodeId,
 810                                       fields: &[hir::StructField],
 811                                       span: Span)
 812                                       -> Mir<'tcx>
 813 {
 814     let tcx = infcx.tcx;
 815     let gcx = tcx.global_tcx();
 816     let def_id = tcx.hir.local_def_id(ctor_id);
 817     let param_env = gcx.param_env(def_id);
 818
 819     // Normalize the sig.
 820     let sig = gcx.fn_sig(def_id).no_late_bound_regions().expect("LBR in ADT constructor signature");
 821     let sig = gcx.normalize_erasing_regions(param_env, sig);
 822
 823     let (adt_def, substs) = match sig.output().sty {
 824         ty::Adt(adt_def, substs) => (adt_def, substs),
 825         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 826     };
 827
 828     debug!("build_ctor: def_id={:?} sig={:?} fields={:?}", def_id, sig, fields);
 829
 830     let local_decls = local_decls_for_sig(&sig, span);
 831
 832     let source_info = SourceInfo {
 833         span,
 834         scope: OUTERMOST_SOURCE_SCOPE
 835     };
 836
 837     let variant_no = if adt_def.is_enum() {
 838         adt_def.variant_index_with_id(def_id)
 839     } else {
 840         0
 841     };
 842
 843     // return = ADT(arg0, arg1, ...); return
 844     let start_block = BasicBlockData {
 845         statements: vec![Statement {
 846             source_info,
 847             kind: StatementKind::Assign(
 848                 Place::Local(RETURN_PLACE),
 849                 Rvalue::Aggregate(
 850                     box AggregateKind::Adt(adt_def, variant_no, substs, None),
 851                     (1..sig.inputs().len()+1).map(|i| {
 852                         Operand::Move(Place::Local(Local::new(i)))
 853                     }).collect()
 854                 )
 855             )
 856         }],
 857         terminator: Some(Terminator {
 858             source_info,
 859             kind: TerminatorKind::Return,
 860         }),
 861         is_cleanup: false
 862     };
 863
 864     Mir::new(
 865         IndexVec::from_elem_n(start_block, 1),
 866         IndexVec::from_elem_n(
 867             SourceScopeData { span: span, parent_scope: None }, 1
 868         ),
 869         ClearCrossCrate::Clear,
 870         IndexVec::new(),
 871         None,
 872         local_decls,
 873         sig.inputs().len(),
 874         vec![],
 875         span
 876     )
 877 }