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::{Kind, Subst, Substs};
  17 use rustc::ty::maps::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 translating a call back to our def-id, which
  73             // trans::mir 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     LocalDecl {
 142         mutability, ty, name: None,
 143         source_info: SourceInfo { scope: ARGUMENT_VISIBILITY_SCOPE, span },
 144         syntactic_scope: ARGUMENT_VISIBILITY_SCOPE,
 145         internal: false,
 146         is_user_variable: false
 147     }
 148 }
 149
 150 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 151     -> IndexVec<Local, LocalDecl<'tcx>>
 152 {
 153     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 154         .chain(sig.inputs().iter().map(
 155             |ity| temp_decl(Mutability::Not, ity, span)))
 156         .collect()
 157 }
 158
 159 fn build_drop_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 160                              def_id: DefId,
 161                              ty: Option<Ty<'tcx>>)
 162                              -> Mir<'tcx>
 163 {
 164     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 165
 166     // Check if this is a generator, if so, return the drop glue for it
 167     if let Some(&ty::TyS { sty: ty::TyGenerator(gen_def_id, substs, _), .. }) = ty {
 168         let mir = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 169         return mir.subst(tcx, substs.substs);
 170     }
 171
 172     let substs = if let Some(ty) = ty {
 173         tcx.mk_substs(iter::once(Kind::from(ty)))
 174     } else {
 175         Substs::identity_for_item(tcx, def_id)
 176     };
 177     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 178     let sig = tcx.erase_late_bound_regions(&sig);
 179     let span = tcx.def_span(def_id);
 180
 181     let source_info = SourceInfo { span, scope: ARGUMENT_VISIBILITY_SCOPE };
 182
 183     let return_block = BasicBlock::new(1);
 184     let mut blocks = IndexVec::new();
 185     let block = |blocks: &mut IndexVec<_, _>, kind| {
 186         blocks.push(BasicBlockData {
 187             statements: vec![],
 188             terminator: Some(Terminator { source_info, kind }),
 189             is_cleanup: false
 190         })
 191     };
 192     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 193     block(&mut blocks, TerminatorKind::Return);
 194
 195     let mut mir = Mir::new(
 196         blocks,
 197         IndexVec::from_elem_n(
 198             VisibilityScopeData { span: span, parent_scope: None }, 1
 199         ),
 200         ClearCrossCrate::Clear,
 201         IndexVec::new(),
 202         None,
 203         local_decls_for_sig(&sig, span),
 204         sig.inputs().len(),
 205         vec![],
 206         span
 207     );
 208
 209     if let Some(..) = ty {
 210         let patch = {
 211             let param_env = tcx.param_env(def_id).with_reveal_all();
 212             let mut elaborator = DropShimElaborator {
 213                 mir: &mir,
 214                 patch: MirPatch::new(&mir),
 215                 tcx,
 216                 param_env
 217             };
 218             let dropee = Place::Local(Local::new(1+0)).deref();
 219             let resume_block = elaborator.patch.resume_block();
 220             elaborate_drops::elaborate_drop(
 221                 &mut elaborator,
 222                 source_info,
 223                 &dropee,
 224                 (),
 225                 return_block,
 226                 elaborate_drops::Unwind::To(resume_block),
 227                 START_BLOCK
 228             );
 229             elaborator.patch
 230         };
 231         patch.apply(&mut mir);
 232     }
 233
 234     mir
 235 }
 236
 237 pub struct DropShimElaborator<'a, 'tcx: 'a> {
 238     pub mir: &'a Mir<'tcx>,
 239     pub patch: MirPatch<'tcx>,
 240     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
 241     pub param_env: ty::ParamEnv<'tcx>,
 242 }
 243
 244 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 245     fn fmt(&self, _f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
 246         Ok(())
 247     }
 248 }
 249
 250 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 251     type Path = ();
 252
 253     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 254     fn mir(&self) -> &'a Mir<'tcx> { self.mir }
 255     fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx> { self.tcx }
 256     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 257
 258     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 259         if let DropFlagMode::Shallow = mode {
 260             DropStyle::Static
 261         } else {
 262             DropStyle::Open
 263         }
 264     }
 265
 266     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 267         None
 268     }
 269
 270     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 271     }
 272
 273     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 274         None
 275     }
 276     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 277         None
 278     }
 279     fn downcast_subpath(&self, _path: Self::Path, _variant: usize) -> Option<Self::Path> {
 280         Some(())
 281     }
 282     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 283         None
 284     }
 285 }
 286
 287 /// Build a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 288 fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 289                               def_id: DefId,
 290                               self_ty: Ty<'tcx>)
 291                               -> Mir<'tcx>
 292 {
 293     debug!("build_clone_shim(def_id={:?})", def_id);
 294
 295     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 296     let is_copy = !self_ty.moves_by_default(tcx, tcx.param_env(def_id), builder.span);
 297
 298     let dest = Place::Local(RETURN_PLACE);
 299     let src = Place::Local(Local::new(1+0)).deref();
 300
 301     match self_ty.sty {
 302         _ if is_copy => builder.copy_shim(),
 303         ty::TyArray(ty, len) => {
 304             let len = len.unwrap_usize(tcx);
 305             builder.array_shim(dest, src, ty, len)
 306         }
 307         ty::TyClosure(def_id, substs) => {
 308             builder.tuple_like_shim(
 309                 dest, src,
 310                 substs.upvar_tys(def_id, tcx)
 311             )
 312         }
 313         ty::TyTuple(tys) => builder.tuple_like_shim(dest, src, tys.iter().cloned()),
 314         _ => {
 315             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 316         }
 317     };
 318
 319     builder.into_mir()
 320 }
 321
 322 struct CloneShimBuilder<'a, 'tcx: 'a> {
 323     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 324     def_id: DefId,
 325     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 326     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 327     span: Span,
 328     sig: ty::FnSig<'tcx>,
 329 }
 330
 331 impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
 332     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 333            def_id: DefId,
 334            self_ty: Ty<'tcx>) -> Self {
 335         // we must subst the self_ty because it's
 336         // otherwise going to be TySelf and we can't index
 337         // or access fields of a Place of type TySelf.
 338         let substs = tcx.mk_substs_trait(self_ty, &[]);
 339         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 340         let sig = tcx.erase_late_bound_regions(&sig);
 341         let span = tcx.def_span(def_id);
 342
 343         CloneShimBuilder {
 344             tcx,
 345             def_id,
 346             local_decls: local_decls_for_sig(&sig, span),
 347             blocks: IndexVec::new(),
 348             span,
 349             sig,
 350         }
 351     }
 352
 353     fn into_mir(self) -> Mir<'tcx> {
 354         Mir::new(
 355             self.blocks,
 356             IndexVec::from_elem_n(
 357                 VisibilityScopeData { span: self.span, parent_scope: None }, 1
 358             ),
 359             ClearCrossCrate::Clear,
 360             IndexVec::new(),
 361             None,
 362             self.local_decls,
 363             self.sig.inputs().len(),
 364             vec![],
 365             self.span
 366         )
 367     }
 368
 369     fn source_info(&self) -> SourceInfo {
 370         SourceInfo { span: self.span, scope: ARGUMENT_VISIBILITY_SCOPE }
 371     }
 372
 373     fn block(
 374         &mut self,
 375         statements: Vec<Statement<'tcx>>,
 376         kind: TerminatorKind<'tcx>,
 377         is_cleanup: bool
 378     ) -> BasicBlock {
 379         let source_info = self.source_info();
 380         self.blocks.push(BasicBlockData {
 381             statements,
 382             terminator: Some(Terminator { source_info, kind }),
 383             is_cleanup,
 384         })
 385     }
 386
 387     /// Gives the index of an upcoming BasicBlock, with an offset.
 388     /// offset=0 will give you the index of the next BasicBlock,
 389     /// offset=1 will give the index of the next-to-next block,
 390     /// offset=-1 will give you the index of the last-created block
 391     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 392         BasicBlock::new(self.blocks.len() + offset)
 393     }
 394
 395     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 396         Statement {
 397             source_info: self.source_info(),
 398             kind,
 399         }
 400     }
 401
 402     fn copy_shim(&mut self) {
 403         let rcvr = Place::Local(Local::new(1+0)).deref();
 404         let ret_statement = self.make_statement(
 405             StatementKind::Assign(
 406                 Place::Local(RETURN_PLACE),
 407                 Rvalue::Use(Operand::Copy(rcvr))
 408             )
 409         );
 410         self.block(vec![ret_statement], TerminatorKind::Return, false);
 411     }
 412
 413     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 414         let span = self.span;
 415         Place::Local(
 416             self.local_decls.push(temp_decl(mutability, ty, span))
 417         )
 418     }
 419
 420     fn make_clone_call(
 421         &mut self,
 422         dest: Place<'tcx>,
 423         src: Place<'tcx>,
 424         ty: Ty<'tcx>,
 425         next: BasicBlock,
 426         cleanup: BasicBlock
 427     ) {
 428         let tcx = self.tcx;
 429
 430         let substs = Substs::for_item(tcx, self.def_id, |param, _| {
 431             match param.kind {
 432                 GenericParamDefKind::Lifetime => tcx.types.re_erased.into(),
 433                 GenericParamDefKind::Type(_) => ty.into(),
 434             }
 435         });
 436
 437         // `func == Clone::clone(&ty) -> ty`
 438         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 439         let func = Operand::Constant(box Constant {
 440             span: self.span,
 441             ty: func_ty,
 442             literal: Literal::Value {
 443                 value: ty::Const::zero_sized(self.tcx, func_ty)
 444             },
 445         });
 446
 447         let ref_loc = self.make_place(
 448             Mutability::Not,
 449             tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 450                 ty,
 451                 mutbl: hir::Mutability::MutImmutable,
 452             })
 453         );
 454
 455         // `let ref_loc: &ty = &src;`
 456         let statement = self.make_statement(
 457             StatementKind::Assign(
 458                 ref_loc.clone(),
 459                 Rvalue::Ref(tcx.types.re_erased, BorrowKind::Shared, src)
 460             )
 461         );
 462
 463         // `let loc = Clone::clone(ref_loc);`
 464         self.block(vec![statement], TerminatorKind::Call {
 465             func,
 466             args: vec![Operand::Move(ref_loc)],
 467             destination: Some((dest, next)),
 468             cleanup: Some(cleanup),
 469         }, false);
 470     }
 471
 472     fn loop_header(
 473         &mut self,
 474         beg: Place<'tcx>,
 475         end: Place<'tcx>,
 476         loop_body: BasicBlock,
 477         loop_end: BasicBlock,
 478         is_cleanup: bool
 479     ) {
 480         let tcx = self.tcx;
 481
 482         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 483         let compute_cond = self.make_statement(
 484             StatementKind::Assign(
 485                 cond.clone(),
 486                 Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 487             )
 488         );
 489
 490         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 491         self.block(
 492             vec![compute_cond],
 493             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 494             is_cleanup
 495         );
 496     }
 497
 498     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 499         box Constant {
 500             span: self.span,
 501             ty: self.tcx.types.usize,
 502             literal: Literal::Value {
 503                 value: ty::Const::from_usize(self.tcx, value),
 504             }
 505         }
 506     }
 507
 508     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 509         let tcx = self.tcx;
 510         let span = self.span;
 511
 512         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 513         let end = self.make_place(Mutability::Not, tcx.types.usize);
 514
 515         // BB #0
 516         // `let mut beg = 0;`
 517         // `let end = len;`
 518         // `goto #1;`
 519         let inits = vec![
 520             self.make_statement(
 521                 StatementKind::Assign(
 522                     Place::Local(beg),
 523                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 524                 )
 525             ),
 526             self.make_statement(
 527                 StatementKind::Assign(
 528                     end.clone(),
 529                     Rvalue::Use(Operand::Constant(self.make_usize(len)))
 530                 )
 531             )
 532         ];
 533         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 534
 535         // BB #1: loop {
 536         //     BB #2;
 537         //     BB #3;
 538         // }
 539         // BB #4;
 540         self.loop_header(Place::Local(beg), end, BasicBlock::new(2), BasicBlock::new(4), false);
 541
 542         // BB #2
 543         // `dest[i] = Clone::clone(src[beg])`;
 544         // Goto #3 if ok, #5 if unwinding happens.
 545         let dest_field = dest.clone().index(beg);
 546         let src_field = src.clone().index(beg);
 547         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 548                              BasicBlock::new(5));
 549
 550         // BB #3
 551         // `beg = beg + 1;`
 552         // `goto #1`;
 553         let statements = vec![
 554             self.make_statement(
 555                 StatementKind::Assign(
 556                     Place::Local(beg),
 557                     Rvalue::BinaryOp(
 558                         BinOp::Add,
 559                         Operand::Copy(Place::Local(beg)),
 560                         Operand::Constant(self.make_usize(1))
 561                     )
 562                 )
 563             )
 564         ];
 565         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 566
 567         // BB #4
 568         // `return dest;`
 569         self.block(vec![], TerminatorKind::Return, false);
 570
 571         // BB #5 (cleanup)
 572         // `let end = beg;`
 573         // `let mut beg = 0;`
 574         // goto #6;
 575         let end = beg;
 576         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 577         let init = self.make_statement(
 578             StatementKind::Assign(
 579                 Place::Local(beg),
 580                 Rvalue::Use(Operand::Constant(self.make_usize(0)))
 581             )
 582         );
 583         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 584
 585         // BB #6 (cleanup): loop {
 586         //     BB #7;
 587         //     BB #8;
 588         // }
 589         // BB #9;
 590         self.loop_header(Place::Local(beg), Place::Local(end),
 591                          BasicBlock::new(7), BasicBlock::new(9), true);
 592
 593         // BB #7 (cleanup)
 594         // `drop(dest[beg])`;
 595         self.block(vec![], TerminatorKind::Drop {
 596             location: dest.index(beg),
 597             target: BasicBlock::new(8),
 598             unwind: None,
 599         }, true);
 600
 601         // BB #8 (cleanup)
 602         // `beg = beg + 1;`
 603         // `goto #6;`
 604         let statement = self.make_statement(
 605             StatementKind::Assign(
 606                 Place::Local(beg),
 607                 Rvalue::BinaryOp(
 608                     BinOp::Add,
 609                     Operand::Copy(Place::Local(beg)),
 610                     Operand::Constant(self.make_usize(1))
 611                 )
 612             )
 613         );
 614         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 615
 616         // BB #9 (resume)
 617         self.block(vec![], TerminatorKind::Resume, true);
 618     }
 619
 620     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 621                           src: Place<'tcx>, tys: I)
 622             where I: Iterator<Item = ty::Ty<'tcx>> {
 623         let mut previous_field = None;
 624         for (i, ity) in tys.enumerate() {
 625             let field = Field::new(i);
 626             let src_field = src.clone().field(field, ity);
 627
 628             let dest_field = dest.clone().field(field, ity);
 629
 630             // #(2i + 1) is the cleanup block for the previous clone operation
 631             let cleanup_block = self.block_index_offset(1);
 632             // #(2i + 2) is the next cloning block
 633             // (or the Return terminator if this is the last block)
 634             let next_block = self.block_index_offset(2);
 635
 636             // BB #(2i)
 637             // `dest.i = Clone::clone(&src.i);`
 638             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 639             self.make_clone_call(
 640                 dest_field.clone(),
 641                 src_field,
 642                 ity,
 643                 next_block,
 644                 cleanup_block,
 645             );
 646
 647             // BB #(2i + 1) (cleanup)
 648             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 649                 // Drop previous field and goto previous cleanup block.
 650                 self.block(vec![], TerminatorKind::Drop {
 651                     location: previous_field,
 652                     target: previous_cleanup,
 653                     unwind: None,
 654                 }, true);
 655             } else {
 656                 // Nothing to drop, just resume.
 657                 self.block(vec![], TerminatorKind::Resume, true);
 658             }
 659
 660             previous_field = Some((dest_field, cleanup_block));
 661         }
 662
 663         self.block(vec![], TerminatorKind::Return, false);
 664     }
 665 }
 666
 667 /// Build a "call" shim for `def_id`. The shim calls the
 668 /// function specified by `call_kind`, first adjusting its first
 669 /// argument according to `rcvr_adjustment`.
 670 ///
 671 /// If `untuple_args` is a vec of types, the second argument of the
 672 /// function will be untupled as these types.
 673 fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 674                              def_id: DefId,
 675                              rcvr_adjustment: Adjustment,
 676                              call_kind: CallKind,
 677                              untuple_args: Option<&[Ty<'tcx>]>)
 678                              -> Mir<'tcx>
 679 {
 680     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 681             call_kind={:?}, untuple_args={:?})",
 682            def_id, rcvr_adjustment, call_kind, untuple_args);
 683
 684     let sig = tcx.fn_sig(def_id);
 685     let sig = tcx.erase_late_bound_regions(&sig);
 686     let span = tcx.def_span(def_id);
 687
 688     debug!("build_call_shim: sig={:?}", sig);
 689
 690     let mut local_decls = local_decls_for_sig(&sig, span);
 691     let source_info = SourceInfo { span, scope: ARGUMENT_VISIBILITY_SCOPE };
 692
 693     let rcvr_arg = Local::new(1+0);
 694     let rcvr_l = Place::Local(rcvr_arg);
 695     let mut statements = vec![];
 696
 697     let rcvr = match rcvr_adjustment {
 698         Adjustment::Identity => Operand::Move(rcvr_l),
 699         Adjustment::Deref => Operand::Copy(rcvr_l.deref()),
 700         Adjustment::RefMut => {
 701             // let rcvr = &mut rcvr;
 702             let ref_rcvr = local_decls.push(temp_decl(
 703                 Mutability::Not,
 704                 tcx.mk_ref(tcx.types.re_erased, ty::TypeAndMut {
 705                     ty: sig.inputs()[0],
 706                     mutbl: hir::Mutability::MutMutable
 707                 }),
 708                 span
 709             ));
 710             let borrow_kind = BorrowKind::Mut {
 711                 allow_two_phase_borrow: false,
 712             };
 713             statements.push(Statement {
 714                 source_info,
 715                 kind: StatementKind::Assign(
 716                     Place::Local(ref_rcvr),
 717                     Rvalue::Ref(tcx.types.re_erased, borrow_kind, rcvr_l)
 718                 )
 719             });
 720             Operand::Move(Place::Local(ref_rcvr))
 721         }
 722     };
 723
 724     let (callee, mut args) = match call_kind {
 725         CallKind::Indirect => (rcvr, vec![]),
 726         CallKind::Direct(def_id) => {
 727             let ty = tcx.type_of(def_id);
 728             (Operand::Constant(box Constant {
 729                 span,
 730                 ty,
 731                 literal: Literal::Value {
 732                     value: ty::Const::zero_sized(tcx, ty)
 733                 },
 734              }),
 735              vec![rcvr])
 736         }
 737     };
 738
 739     if let Some(untuple_args) = untuple_args {
 740         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 741             let arg_place = Place::Local(Local::new(1+1));
 742             Operand::Move(arg_place.field(Field::new(i), *ity))
 743         }));
 744     } else {
 745         args.extend((1..sig.inputs().len()).map(|i| {
 746             Operand::Move(Place::Local(Local::new(1+i)))
 747         }));
 748     }
 749
 750     let mut blocks = IndexVec::new();
 751     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 752         blocks.push(BasicBlockData {
 753             statements,
 754             terminator: Some(Terminator { source_info, kind }),
 755             is_cleanup
 756         })
 757     };
 758
 759     // BB #0
 760     block(&mut blocks, statements, TerminatorKind::Call {
 761         func: callee,
 762         args,
 763         destination: Some((Place::Local(RETURN_PLACE),
 764                            BasicBlock::new(1))),
 765         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 766             Some(BasicBlock::new(3))
 767         } else {
 768             None
 769         }
 770     }, false);
 771
 772     if let Adjustment::RefMut = rcvr_adjustment {
 773         // BB #1 - drop for Self
 774         block(&mut blocks, vec![], TerminatorKind::Drop {
 775             location: Place::Local(rcvr_arg),
 776             target: BasicBlock::new(2),
 777             unwind: None
 778         }, false);
 779     }
 780     // BB #1/#2 - return
 781     block(&mut blocks, vec![], TerminatorKind::Return, false);
 782     if let Adjustment::RefMut = rcvr_adjustment {
 783         // BB #3 - drop if closure panics
 784         block(&mut blocks, vec![], TerminatorKind::Drop {
 785             location: Place::Local(rcvr_arg),
 786             target: BasicBlock::new(4),
 787             unwind: None
 788         }, true);
 789
 790         // BB #4 - resume
 791         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 792     }
 793
 794     let mut mir = Mir::new(
 795         blocks,
 796         IndexVec::from_elem_n(
 797             VisibilityScopeData { span: span, parent_scope: None }, 1
 798         ),
 799         ClearCrossCrate::Clear,
 800         IndexVec::new(),
 801         None,
 802         local_decls,
 803         sig.inputs().len(),
 804         vec![],
 805         span
 806     );
 807     if let Abi::RustCall = sig.abi {
 808         mir.spread_arg = Some(Local::new(sig.inputs().len()));
 809     }
 810     mir
 811 }
 812
 813 pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
 814                                       ctor_id: ast::NodeId,
 815                                       fields: &[hir::StructField],
 816                                       span: Span)
 817                                       -> Mir<'tcx>
 818 {
 819     let tcx = infcx.tcx;
 820     let gcx = tcx.global_tcx();
 821     let def_id = tcx.hir.local_def_id(ctor_id);
 822     let param_env = gcx.param_env(def_id);
 823
 824     // Normalize the sig.
 825     let sig = gcx.fn_sig(def_id).no_late_bound_regions().expect("LBR in ADT constructor signature");
 826     let sig = gcx.normalize_erasing_regions(param_env, sig);
 827
 828     let (adt_def, substs) = match sig.output().sty {
 829         ty::TyAdt(adt_def, substs) => (adt_def, substs),
 830         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 831     };
 832
 833     debug!("build_ctor: def_id={:?} sig={:?} fields={:?}", def_id, sig, fields);
 834
 835     let local_decls = local_decls_for_sig(&sig, span);
 836
 837     let source_info = SourceInfo {
 838         span,
 839         scope: ARGUMENT_VISIBILITY_SCOPE
 840     };
 841
 842     let variant_no = if adt_def.is_enum() {
 843         adt_def.variant_index_with_id(def_id)
 844     } else {
 845         0
 846     };
 847
 848     // return = ADT(arg0, arg1, ...); return
 849     let start_block = BasicBlockData {
 850         statements: vec![Statement {
 851             source_info,
 852             kind: StatementKind::Assign(
 853                 Place::Local(RETURN_PLACE),
 854                 Rvalue::Aggregate(
 855                     box AggregateKind::Adt(adt_def, variant_no, substs, None),
 856                     (1..sig.inputs().len()+1).map(|i| {
 857                         Operand::Move(Place::Local(Local::new(i)))
 858                     }).collect()
 859                 )
 860             )
 861         }],
 862         terminator: Some(Terminator {
 863             source_info,
 864             kind: TerminatorKind::Return,
 865         }),
 866         is_cleanup: false
 867     };
 868
 869     Mir::new(
 870         IndexVec::from_elem_n(start_block, 1),
 871         IndexVec::from_elem_n(
 872             VisibilityScopeData { span: span, parent_scope: None }, 1
 873         ),
 874         ClearCrossCrate::Clear,
 875         IndexVec::new(),
 876         None,
 877         local_decls,
 878         sig.inputs().len(),
 879         vec![],
 880         span
 881     )
 882 }