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::middle::const_val::ConstVal;
  15 use rustc::mir::*;
  16 use rustc::ty::{self, Ty, TyCtxt};
  17 use rustc::ty::subst::{Kind, Subst, Substs};
  18 use rustc::ty::maps::Providers;
  19 use rustc_const_math::{ConstInt, ConstUsize};
  20
  21 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
  22
  23 use syntax::abi::Abi;
  24 use syntax::ast;
  25 use syntax_pos::Span;
  26
  27 use std::fmt;
  28 use std::iter;
  29
  30 use transform::{add_call_guards, no_landing_pads, simplify};
  31 use util::elaborate_drops::{self, DropElaborator, DropStyle, DropFlagMode};
  32 use util::patch::MirPatch;
  33
  34 pub fn provide(providers: &mut Providers) {
  35     providers.mir_shims = make_shim;
  36 }
  37
  38 fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  39                        instance: ty::InstanceDef<'tcx>)
  40                        -> &'tcx Mir<'tcx>
  41 {
  42     debug!("make_shim({:?})", instance);
  43
  44     let mut result = match instance {
  45         ty::InstanceDef::Item(..) =>
  46             bug!("item {:?} passed to make_shim", instance),
  47         ty::InstanceDef::FnPtrShim(def_id, ty) => {
  48             let trait_ = tcx.trait_of_item(def_id).unwrap();
  49             let adjustment = match tcx.lang_items().fn_trait_kind(trait_) {
  50                 Some(ty::ClosureKind::FnOnce) => Adjustment::Identity,
  51                 Some(ty::ClosureKind::FnMut) |
  52                 Some(ty::ClosureKind::Fn) => Adjustment::Deref,
  53                 None => bug!("fn pointer {:?} is not an fn", ty)
  54             };
  55             // HACK: we need the "real" argument types for the MIR,
  56             // but because our substs are (Self, Args), where Args
  57             // is a tuple, we must include the *concrete* argument
  58             // types in the MIR. They will be substituted again with
  59             // the param-substs, but because they are concrete, this
  60             // will not do any harm.
  61             let sig = tcx.erase_late_bound_regions(&ty.fn_sig(tcx));
  62             let arg_tys = sig.inputs();
  63
  64             build_call_shim(
  65                 tcx,
  66                 def_id,
  67                 adjustment,
  68                 CallKind::Indirect,
  69                 Some(arg_tys)
  70             )
  71         }
  72         ty::InstanceDef::Virtual(def_id, _) => {
  73             // We are translating a call back to our def-id, which
  74             // trans::mir knows to turn to an actual virtual call.
  75             build_call_shim(
  76                 tcx,
  77                 def_id,
  78                 Adjustment::Identity,
  79                 CallKind::Direct(def_id),
  80                 None
  81             )
  82         }
  83         ty::InstanceDef::ClosureOnceShim { call_once } => {
  84             let fn_mut = tcx.lang_items().fn_mut_trait().unwrap();
  85             let call_mut = tcx.global_tcx()
  86                 .associated_items(fn_mut)
  87                 .find(|it| it.kind == ty::AssociatedKind::Method)
  88                 .unwrap().def_id;
  89
  90             build_call_shim(
  91                 tcx,
  92                 call_once,
  93                 Adjustment::RefMut,
  94                 CallKind::Direct(call_mut),
  95                 None
  96             )
  97         }
  98         ty::InstanceDef::DropGlue(def_id, ty) => {
  99             build_drop_shim(tcx, def_id, ty)
 100         }
 101         ty::InstanceDef::CloneShim(def_id, ty) => {
 102             let name = tcx.item_name(def_id);
 103             if name == "clone" {
 104                 build_clone_shim(tcx, def_id, ty)
 105             } else if name == "clone_from" {
 106                 debug!("make_shim({:?}: using default trait implementation", instance);
 107                 return tcx.optimized_mir(def_id);
 108             } else {
 109                 bug!("builtin clone shim {:?} not supported", instance)
 110             }
 111         }
 112         ty::InstanceDef::Intrinsic(_) => {
 113             bug!("creating shims from intrinsics ({:?}) is unsupported", instance)
 114         }
 115     };
 116     debug!("make_shim({:?}) = untransformed {:?}", instance, result);
 117     no_landing_pads::no_landing_pads(tcx, &mut result);
 118     simplify::simplify_cfg(&mut result);
 119     add_call_guards::CriticalCallEdges.add_call_guards(&mut result);
 120     debug!("make_shim({:?}) = {:?}", instance, result);
 121
 122     tcx.alloc_mir(result)
 123 }
 124
 125 #[derive(Copy, Clone, Debug, PartialEq)]
 126 enum Adjustment {
 127     Identity,
 128     Deref,
 129     RefMut,
 130 }
 131
 132 #[derive(Copy, Clone, Debug, PartialEq)]
 133 enum CallKind {
 134     Indirect,
 135     Direct(DefId),
 136 }
 137
 138 fn temp_decl(mutability: Mutability, ty: Ty, span: Span) -> LocalDecl {
 139     LocalDecl {
 140         mutability, ty, name: None,
 141         source_info: SourceInfo { scope: ARGUMENT_VISIBILITY_SCOPE, span },
 142         lexical_scope: ARGUMENT_VISIBILITY_SCOPE,
 143         internal: false,
 144         is_user_variable: false
 145     }
 146 }
 147
 148 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 149     -> IndexVec<Local, LocalDecl<'tcx>>
 150 {
 151     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 152         .chain(sig.inputs().iter().map(
 153             |ity| temp_decl(Mutability::Not, ity, span)))
 154         .collect()
 155 }
 156
 157 fn build_drop_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 158                              def_id: DefId,
 159                              ty: Option<Ty<'tcx>>)
 160                              -> Mir<'tcx>
 161 {
 162     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 163
 164     // Check if this is a generator, if so, return the drop glue for it
 165     if let Some(&ty::TyS { sty: ty::TyGenerator(gen_def_id, substs, _), .. }) = ty {
 166         let mir = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 167         return mir.subst(tcx, substs.substs);
 168     }
 169
 170     let substs = if let Some(ty) = ty {
 171         tcx.mk_substs(iter::once(Kind::from(ty)))
 172     } else {
 173         Substs::identity_for_item(tcx, def_id)
 174     };
 175     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 176     let sig = tcx.erase_late_bound_regions(&sig);
 177     let span = tcx.def_span(def_id);
 178
 179     let source_info = SourceInfo { span, scope: ARGUMENT_VISIBILITY_SCOPE };
 180
 181     let return_block = BasicBlock::new(1);
 182     let mut blocks = IndexVec::new();
 183     let block = |blocks: &mut IndexVec<_, _>, kind| {
 184         blocks.push(BasicBlockData {
 185             statements: vec![],
 186             terminator: Some(Terminator { source_info, kind }),
 187             is_cleanup: false
 188         })
 189     };
 190     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 191     block(&mut blocks, TerminatorKind::Return);
 192
 193     let mut mir = Mir::new(
 194         blocks,
 195         IndexVec::from_elem_n(
 196             VisibilityScopeData { span: span, parent_scope: None }, 1
 197         ),
 198         ClearOnDecode::Clear,
 199         IndexVec::new(),
 200         None,
 201         local_decls_for_sig(&sig, span),
 202         sig.inputs().len(),
 203         vec![],
 204         span
 205     );
 206
 207     if let Some(..) = ty {
 208         let patch = {
 209             let param_env = tcx.param_env(def_id);
 210             let mut elaborator = DropShimElaborator {
 211                 mir: &mir,
 212                 patch: MirPatch::new(&mir),
 213                 tcx,
 214                 param_env
 215             };
 216             let dropee = Lvalue::Local(Local::new(1+0)).deref();
 217             let resume_block = elaborator.patch.resume_block();
 218             elaborate_drops::elaborate_drop(
 219                 &mut elaborator,
 220                 source_info,
 221                 &dropee,
 222                 (),
 223                 return_block,
 224                 elaborate_drops::Unwind::To(resume_block),
 225                 START_BLOCK
 226             );
 227             elaborator.patch
 228         };
 229         patch.apply(&mut mir);
 230     }
 231
 232     mir
 233 }
 234
 235 pub struct DropShimElaborator<'a, 'tcx: 'a> {
 236     pub mir: &'a Mir<'tcx>,
 237     pub patch: MirPatch<'tcx>,
 238     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
 239     pub param_env: ty::ParamEnv<'tcx>,
 240 }
 241
 242 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 243     fn fmt(&self, _f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 244         Ok(())
 245     }
 246 }
 247
 248 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 249     type Path = ();
 250
 251     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 252     fn mir(&self) -> &'a Mir<'tcx> { self.mir }
 253     fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx> { self.tcx }
 254     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 255
 256     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 257         if let DropFlagMode::Shallow = mode {
 258             DropStyle::Static
 259         } else {
 260             DropStyle::Open
 261         }
 262     }
 263
 264     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 265         None
 266     }
 267
 268     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 269     }
 270
 271     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 272         None
 273     }
 274     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 275         None
 276     }
 277     fn downcast_subpath(&self, _path: Self::Path, _variant: usize) -> Option<Self::Path> {
 278         Some(())
 279     }
 280 }
 281
 282 /// Build a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 283 fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 284                               def_id: DefId,
 285                               self_ty: Ty<'tcx>)
 286                               -> Mir<'tcx>
 287 {
 288     debug!("build_clone_shim(def_id={:?})", def_id);
 289
 290     let mut builder = CloneShimBuilder::new(tcx, def_id);
 291     let is_copy = !self_ty.moves_by_default(tcx, tcx.param_env(def_id), builder.span);
 292
 293     match self_ty.sty {
 294         _ if is_copy => builder.copy_shim(),
 295         ty::TyArray(ty, len) => {
 296             let len = len.val.to_const_int().unwrap().to_u64().unwrap();
 297             builder.array_shim(ty, len)
 298         }
 299         ty::TyClosure(def_id, substs) => {
 300             builder.tuple_like_shim(
 301                 &substs.upvar_tys(def_id, tcx).collect::<Vec<_>>(),
 302                 AggregateKind::Closure(def_id, substs)
 303             )
 304         }
 305         ty::TyTuple(tys, _) => builder.tuple_like_shim(&**tys, AggregateKind::Tuple),
 306         _ => {
 307             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 308         }
 309     };
 310
 311     builder.into_mir()
 312 }
 313
 314 struct CloneShimBuilder<'a, 'tcx: 'a> {
 315     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 316     def_id: DefId,
 317     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 318     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 319     span: Span,
 320     sig: ty::FnSig<'tcx>,
 321 }
 322
 323 impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
 324     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Self {
 325         let sig = tcx.fn_sig(def_id);
 326         let sig = tcx.erase_late_bound_regions(&sig);
 327         let span = tcx.def_span(def_id);
 328
 329         CloneShimBuilder {
 330             tcx,
 331             def_id,
 332             local_decls: local_decls_for_sig(&sig, span),
 333             blocks: IndexVec::new(),
 334             span,
 335             sig,
 336         }
 337     }
 338
 339     fn into_mir(self) -> Mir<'tcx> {
 340         Mir::new(
 341             self.blocks,
 342             IndexVec::from_elem_n(
 343                 VisibilityScopeData { span: self.span, parent_scope: None }, 1
 344             ),
 345             ClearOnDecode::Clear,
 346             IndexVec::new(),
 347             None,
 348             self.local_decls,
 349             self.sig.inputs().len(),
 350             vec![],
 351             self.span
 352         )
 353     }
 354
 355     fn source_info(&self) -> SourceInfo {
 356         SourceInfo { span: self.span, scope: ARGUMENT_VISIBILITY_SCOPE }
 357     }
 358
 359     fn block(
 360         &mut self,
 361         statements: Vec<Statement<'tcx>>,
 362         kind: TerminatorKind<'tcx>,
 363         is_cleanup: bool
 364     ) -> BasicBlock {
 365         let source_info = self.source_info();
 366         self.blocks.push(BasicBlockData {
 367             statements,
 368             terminator: Some(Terminator { source_info, kind }),
 369             is_cleanup,
 370         })
 371     }
 372
 373     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 374         Statement {
 375             source_info: self.source_info(),
 376             kind,
 377         }
 378     }
 379
 380     fn copy_shim(&mut self) {
 381         let rcvr = Lvalue::Local(Local::new(1+0)).deref();
 382         let ret_statement = self.make_statement(
 383             StatementKind::Assign(
 384                 Lvalue::Local(RETURN_POINTER),
 385                 Rvalue::Use(Operand::Consume(rcvr))
 386             )
 387         );
 388         self.block(vec![ret_statement], TerminatorKind::Return, false);
 389     }
 390
 391     fn make_lvalue(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Lvalue<'tcx> {
 392         let span = self.span;
 393         Lvalue::Local(
 394             self.local_decls.push(temp_decl(mutability, ty, span))
 395         )
 396     }
 397
 398     fn make_clone_call(
 399         &mut self,
 400         ty: Ty<'tcx>,
 401         rcvr_field: Lvalue<'tcx>,
 402         next: BasicBlock,
 403         cleanup: BasicBlock
 404     ) -> Lvalue<'tcx> {
 405         let tcx = self.tcx;
 406
 407         let substs = Substs::for_item(
 408             tcx,
 409             self.def_id,
 410             |_, _| tcx.types.re_erased,
 411             |_, _| ty
 412         );
 413
 414         // `func == Clone::clone(&ty) -> ty`
 415         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 416         let func = Operand::Constant(box Constant {
 417             span: self.span,
 418             ty: func_ty,
 419             literal: Literal::Value {
 420                 value: tcx.mk_const(ty::Const {
 421                     val: ConstVal::Function(self.def_id, substs),
 422                     ty: func_ty
 423                 }),
 424             },
 425         });
 426
 427         let ref_loc = self.make_lvalue(
 428             Mutability::Not,
 429             tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 430                 ty,
 431                 mutbl: hir::Mutability::MutImmutable,
 432             })
 433         );
 434
 435         let loc = self.make_lvalue(Mutability::Not, ty);
 436
 437         // `let ref_loc: &ty = &rcvr_field;`
 438         let statement = self.make_statement(
 439             StatementKind::Assign(
 440                 ref_loc.clone(),
 441                 Rvalue::Ref(tcx.types.re_erased, BorrowKind::Shared, rcvr_field)
 442             )
 443         );
 444
 445         // `let loc = Clone::clone(ref_loc);`
 446         self.block(vec![statement], TerminatorKind::Call {
 447             func,
 448             args: vec![Operand::Consume(ref_loc)],
 449             destination: Some((loc.clone(), next)),
 450             cleanup: Some(cleanup),
 451         }, false);
 452
 453         loc
 454     }
 455
 456     fn loop_header(
 457         &mut self,
 458         beg: Lvalue<'tcx>,
 459         end: Lvalue<'tcx>,
 460         loop_body: BasicBlock,
 461         loop_end: BasicBlock,
 462         is_cleanup: bool
 463     ) {
 464         let tcx = self.tcx;
 465
 466         let cond = self.make_lvalue(Mutability::Mut, tcx.types.bool);
 467         let compute_cond = self.make_statement(
 468             StatementKind::Assign(
 469                 cond.clone(),
 470                 Rvalue::BinaryOp(BinOp::Ne, Operand::Consume(end), Operand::Consume(beg))
 471             )
 472         );
 473
 474         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 475         self.block(
 476             vec![compute_cond],
 477             TerminatorKind::if_(tcx, Operand::Consume(cond), loop_body, loop_end),
 478             is_cleanup
 479         );
 480     }
 481
 482     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 483         let value = ConstUsize::new(value, self.tcx.sess.target.usize_ty).unwrap();
 484         box Constant {
 485             span: self.span,
 486             ty: self.tcx.types.usize,
 487             literal: Literal::Value {
 488                 value: self.tcx.mk_const(ty::Const {
 489                     val: ConstVal::Integral(ConstInt::Usize(value)),
 490                     ty: self.tcx.types.usize,
 491                 })
 492             }
 493         }
 494     }
 495
 496     fn array_shim(&mut self, ty: Ty<'tcx>, len: u64) {
 497         let tcx = self.tcx;
 498         let span = self.span;
 499         let rcvr = Lvalue::Local(Local::new(1+0)).deref();
 500
 501         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 502         let end = self.make_lvalue(Mutability::Not, tcx.types.usize);
 503         let ret = self.make_lvalue(Mutability::Mut, tcx.mk_array(ty, len));
 504
 505         // BB #0
 506         // `let mut beg = 0;`
 507         // `let end = len;`
 508         // `goto #1;`
 509         let inits = vec![
 510             self.make_statement(
 511                 StatementKind::Assign(
 512                     Lvalue::Local(beg),
 513                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 514                 )
 515             ),
 516             self.make_statement(
 517                 StatementKind::Assign(
 518                     end.clone(),
 519                     Rvalue::Use(Operand::Constant(self.make_usize(len)))
 520                 )
 521             )
 522         ];
 523         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 524
 525         // BB #1: loop {
 526         //     BB #2;
 527         //     BB #3;
 528         // }
 529         // BB #4;
 530         self.loop_header(Lvalue::Local(beg), end, BasicBlock::new(2), BasicBlock::new(4), false);
 531
 532         // BB #2
 533         // `let cloned = Clone::clone(rcvr[beg])`;
 534         // Goto #3 if ok, #5 if unwinding happens.
 535         let rcvr_field = rcvr.clone().index(beg);
 536         let cloned = self.make_clone_call(ty, rcvr_field, BasicBlock::new(3), BasicBlock::new(5));
 537
 538         // BB #3
 539         // `ret[beg] = cloned;`
 540         // `beg = beg + 1;`
 541         // `goto #1`;
 542         let ret_field = ret.clone().index(beg);
 543         let statements = vec![
 544             self.make_statement(
 545                 StatementKind::Assign(
 546                     ret_field,
 547                     Rvalue::Use(Operand::Consume(cloned))
 548                 )
 549             ),
 550             self.make_statement(
 551                 StatementKind::Assign(
 552                     Lvalue::Local(beg),
 553                     Rvalue::BinaryOp(
 554                         BinOp::Add,
 555                         Operand::Consume(Lvalue::Local(beg)),
 556                         Operand::Constant(self.make_usize(1))
 557                     )
 558                 )
 559             )
 560         ];
 561         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 562
 563         // BB #4
 564         // `return ret;`
 565         let ret_statement = self.make_statement(
 566             StatementKind::Assign(
 567                 Lvalue::Local(RETURN_POINTER),
 568                 Rvalue::Use(Operand::Consume(ret.clone())),
 569             )
 570         );
 571         self.block(vec![ret_statement], TerminatorKind::Return, false);
 572
 573         // BB #5 (cleanup)
 574         // `let end = beg;`
 575         // `let mut beg = 0;`
 576         // goto #6;
 577         let end = beg;
 578         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 579         let init = self.make_statement(
 580             StatementKind::Assign(
 581                 Lvalue::Local(beg),
 582                 Rvalue::Use(Operand::Constant(self.make_usize(0)))
 583             )
 584         );
 585         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 586
 587         // BB #6 (cleanup): loop {
 588         //     BB #7;
 589         //     BB #8;
 590         // }
 591         // BB #9;
 592         self.loop_header(Lvalue::Local(beg), Lvalue::Local(end),
 593                          BasicBlock::new(7), BasicBlock::new(9), true);
 594
 595         // BB #7 (cleanup)
 596         // `drop(ret[beg])`;
 597         self.block(vec![], TerminatorKind::Drop {
 598             location: ret.index(beg),
 599             target: BasicBlock::new(8),
 600             unwind: None,
 601         }, true);
 602
 603         // BB #8 (cleanup)
 604         // `beg = beg + 1;`
 605         // `goto #6;`
 606         let statement = self.make_statement(
 607             StatementKind::Assign(
 608                 Lvalue::Local(beg),
 609                 Rvalue::BinaryOp(
 610                     BinOp::Add,
 611                     Operand::Consume(Lvalue::Local(beg)),
 612                     Operand::Constant(self.make_usize(1))
 613                 )
 614             )
 615         );
 616         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 617
 618         // BB #9 (resume)
 619         self.block(vec![], TerminatorKind::Resume, true);
 620     }
 621
 622     fn tuple_like_shim(&mut self, tys: &[ty::Ty<'tcx>], kind: AggregateKind<'tcx>) {
 623         match kind {
 624             AggregateKind::Tuple | AggregateKind::Closure(..) => (),
 625             _ => bug!("only tuples and closures are accepted"),
 626         };
 627
 628         let rcvr = Lvalue::Local(Local::new(1+0)).deref();
 629
 630         let mut returns = Vec::new();
 631         for (i, ity) in tys.iter().enumerate() {
 632             let rcvr_field = rcvr.clone().field(Field::new(i), *ity);
 633
 634             // BB #(2i)
 635             // `returns[i] = Clone::clone(&rcvr.i);`
 636             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 637             returns.push(
 638                 self.make_clone_call(
 639                     *ity,
 640                     rcvr_field,
 641                     BasicBlock::new(2 * i + 2),
 642                     BasicBlock::new(2 * i + 1),
 643                 )
 644             );
 645
 646             // BB #(2i + 1) (cleanup)
 647             if i == 0 {
 648                 // Nothing to drop, just resume.
 649                 self.block(vec![], TerminatorKind::Resume, true);
 650             } else {
 651                 // Drop previous field and goto previous cleanup block.
 652                 self.block(vec![], TerminatorKind::Drop {
 653                     location: returns[i - 1].clone(),
 654                     target: BasicBlock::new(2 * i - 1),
 655                     unwind: None,
 656                 }, true);
 657             }
 658         }
 659
 660         // `return kind(returns[0], returns[1], ..., returns[tys.len() - 1]);`
 661         let ret_statement = self.make_statement(
 662             StatementKind::Assign(
 663                 Lvalue::Local(RETURN_POINTER),
 664                 Rvalue::Aggregate(
 665                     box kind,
 666                     returns.into_iter().map(Operand::Consume).collect()
 667                 )
 668             )
 669         );
 670         self.block(vec![ret_statement], TerminatorKind::Return, false);
 671     }
 672 }
 673
 674 /// Build a "call" shim for `def_id`. The shim calls the
 675 /// function specified by `call_kind`, first adjusting its first
 676 /// argument according to `rcvr_adjustment`.
 677 ///
 678 /// If `untuple_args` is a vec of types, the second argument of the
 679 /// function will be untupled as these types.
 680 fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 681                              def_id: DefId,
 682                              rcvr_adjustment: Adjustment,
 683                              call_kind: CallKind,
 684                              untuple_args: Option<&[Ty<'tcx>]>)
 685                              -> Mir<'tcx>
 686 {
 687     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 688             call_kind={:?}, untuple_args={:?})",
 689            def_id, rcvr_adjustment, call_kind, untuple_args);
 690
 691     let sig = tcx.fn_sig(def_id);
 692     let sig = tcx.erase_late_bound_regions(&sig);
 693     let span = tcx.def_span(def_id);
 694
 695     debug!("build_call_shim: sig={:?}", sig);
 696
 697     let mut local_decls = local_decls_for_sig(&sig, span);
 698     let source_info = SourceInfo { span, scope: ARGUMENT_VISIBILITY_SCOPE };
 699
 700     let rcvr_arg = Local::new(1+0);
 701     let rcvr_l = Lvalue::Local(rcvr_arg);
 702     let mut statements = vec![];
 703
 704     let rcvr = match rcvr_adjustment {
 705         Adjustment::Identity => Operand::Consume(rcvr_l),
 706         Adjustment::Deref => Operand::Consume(rcvr_l.deref()),
 707         Adjustment::RefMut => {
 708             // let rcvr = &mut rcvr;
 709             let ref_rcvr = local_decls.push(temp_decl(
 710                 Mutability::Not,
 711                 tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 712                     ty: sig.inputs()[0],
 713                     mutbl: hir::Mutability::MutMutable
 714                 }),
 715                 span
 716             ));
 717             statements.push(Statement {
 718                 source_info,
 719                 kind: StatementKind::Assign(
 720                     Lvalue::Local(ref_rcvr),
 721                     Rvalue::Ref(tcx.types.re_erased, BorrowKind::Mut, rcvr_l)
 722                 )
 723             });
 724             Operand::Consume(Lvalue::Local(ref_rcvr))
 725         }
 726     };
 727
 728     let (callee, mut args) = match call_kind {
 729         CallKind::Indirect => (rcvr, vec![]),
 730         CallKind::Direct(def_id) => {
 731             let ty = tcx.type_of(def_id);
 732             (Operand::Constant(box Constant {
 733                 span,
 734                 ty,
 735                 literal: Literal::Value {
 736                     value: tcx.mk_const(ty::Const {
 737                         val: ConstVal::Function(def_id,
 738                             Substs::identity_for_item(tcx, def_id)),
 739                         ty
 740                     }),
 741                 },
 742              }),
 743              vec![rcvr])
 744         }
 745     };
 746
 747     if let Some(untuple_args) = untuple_args {
 748         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 749             let arg_lv = Lvalue::Local(Local::new(1+1));
 750             Operand::Consume(arg_lv.field(Field::new(i), *ity))
 751         }));
 752     } else {
 753         args.extend((1..sig.inputs().len()).map(|i| {
 754             Operand::Consume(Lvalue::Local(Local::new(1+i)))
 755         }));
 756     }
 757
 758     let mut blocks = IndexVec::new();
 759     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 760         blocks.push(BasicBlockData {
 761             statements,
 762             terminator: Some(Terminator { source_info, kind }),
 763             is_cleanup
 764         })
 765     };
 766
 767     // BB #0
 768     block(&mut blocks, statements, TerminatorKind::Call {
 769         func: callee,
 770         args,
 771         destination: Some((Lvalue::Local(RETURN_POINTER),
 772                            BasicBlock::new(1))),
 773         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 774             Some(BasicBlock::new(3))
 775         } else {
 776             None
 777         }
 778     }, false);
 779
 780     if let Adjustment::RefMut = rcvr_adjustment {
 781         // BB #1 - drop for Self
 782         block(&mut blocks, vec![], TerminatorKind::Drop {
 783             location: Lvalue::Local(rcvr_arg),
 784             target: BasicBlock::new(2),
 785             unwind: None
 786         }, false);
 787     }
 788     // BB #1/#2 - return
 789     block(&mut blocks, vec![], TerminatorKind::Return, false);
 790     if let Adjustment::RefMut = rcvr_adjustment {
 791         // BB #3 - drop if closure panics
 792         block(&mut blocks, vec![], TerminatorKind::Drop {
 793             location: Lvalue::Local(rcvr_arg),
 794             target: BasicBlock::new(4),
 795             unwind: None
 796         }, true);
 797
 798         // BB #4 - resume
 799         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 800     }
 801
 802     let mut mir = Mir::new(
 803         blocks,
 804         IndexVec::from_elem_n(
 805             VisibilityScopeData { span: span, parent_scope: None }, 1
 806         ),
 807         ClearOnDecode::Clear,
 808         IndexVec::new(),
 809         None,
 810         local_decls,
 811         sig.inputs().len(),
 812         vec![],
 813         span
 814     );
 815     if let Abi::RustCall = sig.abi {
 816         mir.spread_arg = Some(Local::new(sig.inputs().len()));
 817     }
 818     mir
 819 }
 820
 821 pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
 822                                       ctor_id: ast::NodeId,
 823                                       fields: &[hir::StructField],
 824                                       span: Span)
 825                                       -> Mir<'tcx>
 826 {
 827     let tcx = infcx.tcx;
 828     let gcx = tcx.global_tcx();
 829     let def_id = tcx.hir.local_def_id(ctor_id);
 830     let sig = gcx.no_late_bound_regions(&gcx.fn_sig(def_id))
 831         .expect("LBR in ADT constructor signature");
 832     let sig = gcx.erase_regions(&sig);
 833     let param_env = gcx.param_env(def_id);
 834
 835     // Normalize the sig now that we have liberated the late-bound
 836     // regions.
 837     let sig = gcx.normalize_associated_type_in_env(&sig, param_env);
 838
 839     let (adt_def, substs) = match sig.output().sty {
 840         ty::TyAdt(adt_def, substs) => (adt_def, substs),
 841         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 842     };
 843
 844     debug!("build_ctor: def_id={:?} sig={:?} fields={:?}", def_id, sig, fields);
 845
 846     let local_decls = local_decls_for_sig(&sig, span);
 847
 848     let source_info = SourceInfo {
 849         span,
 850         scope: ARGUMENT_VISIBILITY_SCOPE
 851     };
 852
 853     let variant_no = if adt_def.is_enum() {
 854         adt_def.variant_index_with_id(def_id)
 855     } else {
 856         0
 857     };
 858
 859     // return = ADT(arg0, arg1, ...); return
 860     let start_block = BasicBlockData {
 861         statements: vec![Statement {
 862             source_info,
 863             kind: StatementKind::Assign(
 864                 Lvalue::Local(RETURN_POINTER),
 865                 Rvalue::Aggregate(
 866                     box AggregateKind::Adt(adt_def, variant_no, substs, None),
 867                     (1..sig.inputs().len()+1).map(|i| {
 868                         Operand::Consume(Lvalue::Local(Local::new(i)))
 869                     }).collect()
 870                 )
 871             )
 872         }],
 873         terminator: Some(Terminator {
 874             source_info,
 875             kind: TerminatorKind::Return,
 876         }),
 877         is_cleanup: false
 878     };
 879
 880     Mir::new(
 881         IndexVec::from_elem_n(start_block, 1),
 882         IndexVec::from_elem_n(
 883             VisibilityScopeData { span: span, parent_scope: None }, 1
 884         ),
 885         ClearOnDecode::Clear,
 886         IndexVec::new(),
 887         None,
 888         local_decls,
 889         sig.inputs().len(),
 890         vec![],
 891         span
 892     )
 893 }