src/librustc_mir/shim.rs

   1 use rustc::hir;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::infer;
   4 use rustc::mir::*;
   5 use rustc::ty::{self, Ty, TyCtxt};
   6 use rustc::ty::layout::VariantIdx;
   7 use rustc::ty::subst::{Subst, InternalSubsts};
   8 use rustc::ty::query::Providers;
   9
  10 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
  11
  12 use rustc_target::spec::abi::Abi;
  13 use syntax_pos::{Span, sym};
  14
  15 use std::fmt;
  16 use std::iter;
  17
  18 use crate::transform::{
  19     add_moves_for_packed_drops, add_call_guards,
  20     remove_noop_landing_pads, no_landing_pads, simplify, run_passes
  21 };
  22 use crate::util::elaborate_drops::{self, DropElaborator, DropStyle, DropFlagMode};
  23 use crate::util::patch::MirPatch;
  24
  25 pub fn provide(providers: &mut Providers<'_>) {
  26     providers.mir_shims = make_shim;
  27 }
  28
  29 fn make_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  30                        instance: ty::InstanceDef<'tcx>)
  31                        -> &'tcx Body<'tcx>
  32 {
  33     debug!("make_shim({:?})", instance);
  34
  35     let mut result = match instance {
  36         ty::InstanceDef::Item(..) =>
  37             bug!("item {:?} passed to make_shim", instance),
  38         ty::InstanceDef::VtableShim(def_id) => {
  39             build_call_shim(
  40                 tcx,
  41                 def_id,
  42                 Adjustment::DerefMove,
  43                 CallKind::Direct(def_id),
  44                 None,
  45             )
  46         }
  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 generating a call back to our def-id, which the
  74             // codegen backend 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::AssocKind::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 == sym::clone {
 104                 build_clone_shim(tcx, def_id, ty)
 105             } else if name == sym::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
 118     run_passes(tcx, &mut result, instance, MirPhase::Const, &[
 119         &add_moves_for_packed_drops::AddMovesForPackedDrops,
 120         &no_landing_pads::NoLandingPads,
 121         &remove_noop_landing_pads::RemoveNoopLandingPads,
 122         &simplify::SimplifyCfg::new("make_shim"),
 123         &add_call_guards::CriticalCallEdges,
 124     ]);
 125
 126     debug!("make_shim({:?}) = {:?}", instance, result);
 127
 128     tcx.arena.alloc(result)
 129 }
 130
 131 #[derive(Copy, Clone, Debug, PartialEq)]
 132 enum Adjustment {
 133     Identity,
 134     Deref,
 135     DerefMove,
 136     RefMut,
 137 }
 138
 139 #[derive(Copy, Clone, Debug, PartialEq)]
 140 enum CallKind {
 141     Indirect,
 142     Direct(DefId),
 143 }
 144
 145 fn temp_decl(mutability: Mutability, ty: Ty<'_>, span: Span) -> LocalDecl<'_> {
 146     let source_info = SourceInfo { scope: OUTERMOST_SOURCE_SCOPE, span };
 147     LocalDecl {
 148         mutability,
 149         ty,
 150         user_ty: UserTypeProjections::none(),
 151         name: None,
 152         source_info,
 153         visibility_scope: source_info.scope,
 154         internal: false,
 155         is_user_variable: None,
 156         is_block_tail: None,
 157     }
 158 }
 159
 160 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 161     -> IndexVec<Local, LocalDecl<'tcx>>
 162 {
 163     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 164         .chain(sig.inputs().iter().map(
 165             |ity| temp_decl(Mutability::Not, ity, span)))
 166         .collect()
 167 }
 168
 169 fn build_drop_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 170                              def_id: DefId,
 171                              ty: Option<Ty<'tcx>>)
 172                              -> Body<'tcx>
 173 {
 174     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 175
 176     // Check if this is a generator, if so, return the drop glue for it
 177     if let Some(&ty::TyS { sty: ty::Generator(gen_def_id, substs, _), .. }) = ty {
 178         let mir = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 179         return mir.subst(tcx, substs.substs);
 180     }
 181
 182     let substs = if let Some(ty) = ty {
 183         tcx.intern_substs(&[ty.into()])
 184     } else {
 185         InternalSubsts::identity_for_item(tcx, def_id)
 186     };
 187     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 188     let sig = tcx.erase_late_bound_regions(&sig);
 189     let span = tcx.def_span(def_id);
 190
 191     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 192
 193     let return_block = BasicBlock::new(1);
 194     let mut blocks = IndexVec::with_capacity(2);
 195     let block = |blocks: &mut IndexVec<_, _>, kind| {
 196         blocks.push(BasicBlockData {
 197             statements: vec![],
 198             terminator: Some(Terminator { source_info, kind }),
 199             is_cleanup: false
 200         })
 201     };
 202     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 203     block(&mut blocks, TerminatorKind::Return);
 204
 205     let mut mir = Body::new(
 206         blocks,
 207         IndexVec::from_elem_n(
 208             SourceScopeData { span: span, parent_scope: None }, 1
 209         ),
 210         ClearCrossCrate::Clear,
 211         IndexVec::new(),
 212         None,
 213         local_decls_for_sig(&sig, span),
 214         IndexVec::new(),
 215         sig.inputs().len(),
 216         vec![],
 217         span,
 218         vec![],
 219     );
 220
 221     if let Some(..) = ty {
 222         // The first argument (index 0), but add 1 for the return value.
 223         let dropee_ptr = Place::Base(PlaceBase::Local(Local::new(1+0)));
 224         if tcx.sess.opts.debugging_opts.mir_emit_retag {
 225             // Function arguments should be retagged, and we make this one raw.
 226             mir.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
 227                 source_info,
 228                 kind: StatementKind::Retag(RetagKind::Raw, dropee_ptr.clone()),
 229             });
 230         }
 231         let patch = {
 232             let param_env = tcx.param_env(def_id).with_reveal_all();
 233             let mut elaborator = DropShimElaborator {
 234                 mir: &mir,
 235                 patch: MirPatch::new(&mir),
 236                 tcx,
 237                 param_env
 238             };
 239             let dropee = dropee_ptr.deref();
 240             let resume_block = elaborator.patch.resume_block();
 241             elaborate_drops::elaborate_drop(
 242                 &mut elaborator,
 243                 source_info,
 244                 &dropee,
 245                 (),
 246                 return_block,
 247                 elaborate_drops::Unwind::To(resume_block),
 248                 START_BLOCK
 249             );
 250             elaborator.patch
 251         };
 252         patch.apply(&mut mir);
 253     }
 254
 255     mir
 256 }
 257
 258 pub struct DropShimElaborator<'a, 'tcx: 'a> {
 259     pub mir: &'a Body<'tcx>,
 260     pub patch: MirPatch<'tcx>,
 261     pub tcx: TyCtxt<'a, 'tcx, 'tcx>,
 262     pub param_env: ty::ParamEnv<'tcx>,
 263 }
 264
 265 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 266     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
 267         Ok(())
 268     }
 269 }
 270
 271 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 272     type Path = ();
 273
 274     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 275     fn mir(&self) -> &'a Body<'tcx> { self.mir }
 276     fn tcx(&self) -> TyCtxt<'a, 'tcx, 'tcx> { self.tcx }
 277     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 278
 279     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 280         if let DropFlagMode::Shallow = mode {
 281             DropStyle::Static
 282         } else {
 283             DropStyle::Open
 284         }
 285     }
 286
 287     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 288         None
 289     }
 290
 291     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 292     }
 293
 294     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 295         None
 296     }
 297     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 298         None
 299     }
 300     fn downcast_subpath(&self, _path: Self::Path, _variant: VariantIdx) -> Option<Self::Path> {
 301         Some(())
 302     }
 303     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 304         None
 305     }
 306 }
 307
 308 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 309 fn build_clone_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 310                               def_id: DefId,
 311                               self_ty: Ty<'tcx>)
 312                               -> Body<'tcx>
 313 {
 314     debug!("build_clone_shim(def_id={:?})", def_id);
 315
 316     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 317     let is_copy = self_ty.is_copy_modulo_regions(tcx, tcx.param_env(def_id), builder.span);
 318
 319     let dest = Place::RETURN_PLACE;
 320     let src = Place::Base(PlaceBase::Local(Local::new(1+0))).deref();
 321
 322     match self_ty.sty {
 323         _ if is_copy => builder.copy_shim(),
 324         ty::Array(ty, len) => {
 325             let len = len.unwrap_usize(tcx);
 326             builder.array_shim(dest, src, ty, len)
 327         }
 328         ty::Closure(def_id, substs) => {
 329             builder.tuple_like_shim(
 330                 dest, src,
 331                 substs.upvar_tys(def_id, tcx)
 332             )
 333         }
 334         ty::Tuple(tys) => builder.tuple_like_shim(dest, src, tys.iter().map(|k| k.expect_ty())),
 335         _ => {
 336             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 337         }
 338     };
 339
 340     builder.into_mir()
 341 }
 342
 343 struct CloneShimBuilder<'a, 'tcx: 'a> {
 344     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 345     def_id: DefId,
 346     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 347     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 348     span: Span,
 349     sig: ty::FnSig<'tcx>,
 350 }
 351
 352 impl<'a, 'tcx> CloneShimBuilder<'a, 'tcx> {
 353     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 354            def_id: DefId,
 355            self_ty: Ty<'tcx>) -> Self {
 356         // we must subst the self_ty because it's
 357         // otherwise going to be TySelf and we can't index
 358         // or access fields of a Place of type TySelf.
 359         let substs = tcx.mk_substs_trait(self_ty, &[]);
 360         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 361         let sig = tcx.erase_late_bound_regions(&sig);
 362         let span = tcx.def_span(def_id);
 363
 364         CloneShimBuilder {
 365             tcx,
 366             def_id,
 367             local_decls: local_decls_for_sig(&sig, span),
 368             blocks: IndexVec::new(),
 369             span,
 370             sig,
 371         }
 372     }
 373
 374     fn into_mir(self) -> Body<'tcx> {
 375         Body::new(
 376             self.blocks,
 377             IndexVec::from_elem_n(
 378                 SourceScopeData { span: self.span, parent_scope: None }, 1
 379             ),
 380             ClearCrossCrate::Clear,
 381             IndexVec::new(),
 382             None,
 383             self.local_decls,
 384             IndexVec::new(),
 385             self.sig.inputs().len(),
 386             vec![],
 387             self.span,
 388             vec![],
 389         )
 390     }
 391
 392     fn source_info(&self) -> SourceInfo {
 393         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 394     }
 395
 396     fn block(
 397         &mut self,
 398         statements: Vec<Statement<'tcx>>,
 399         kind: TerminatorKind<'tcx>,
 400         is_cleanup: bool
 401     ) -> BasicBlock {
 402         let source_info = self.source_info();
 403         self.blocks.push(BasicBlockData {
 404             statements,
 405             terminator: Some(Terminator { source_info, kind }),
 406             is_cleanup,
 407         })
 408     }
 409
 410     /// Gives the index of an upcoming BasicBlock, with an offset.
 411     /// offset=0 will give you the index of the next BasicBlock,
 412     /// offset=1 will give the index of the next-to-next block,
 413     /// offset=-1 will give you the index of the last-created block
 414     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 415         BasicBlock::new(self.blocks.len() + offset)
 416     }
 417
 418     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 419         Statement {
 420             source_info: self.source_info(),
 421             kind,
 422         }
 423     }
 424
 425     fn copy_shim(&mut self) {
 426         let rcvr = Place::Base(PlaceBase::Local(Local::new(1+0))).deref();
 427         let ret_statement = self.make_statement(
 428             StatementKind::Assign(
 429                 Place::RETURN_PLACE,
 430                 box Rvalue::Use(Operand::Copy(rcvr))
 431             )
 432         );
 433         self.block(vec![ret_statement], TerminatorKind::Return, false);
 434     }
 435
 436     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 437         let span = self.span;
 438         Place::Base(PlaceBase::Local(
 439             self.local_decls.push(temp_decl(mutability, ty, span))
 440         ))
 441     }
 442
 443     fn make_clone_call(
 444         &mut self,
 445         dest: Place<'tcx>,
 446         src: Place<'tcx>,
 447         ty: Ty<'tcx>,
 448         next: BasicBlock,
 449         cleanup: BasicBlock
 450     ) {
 451         let tcx = self.tcx;
 452
 453         let substs = tcx.mk_substs_trait(ty, &[]);
 454
 455         // `func == Clone::clone(&ty) -> ty`
 456         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 457         let func = Operand::Constant(box Constant {
 458             span: self.span,
 459             ty: func_ty,
 460             user_ty: None,
 461             literal: ty::Const::zero_sized(tcx, func_ty),
 462         });
 463
 464         let ref_loc = self.make_place(
 465             Mutability::Not,
 466             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 467                 ty,
 468                 mutbl: hir::Mutability::MutImmutable,
 469             })
 470         );
 471
 472         // `let ref_loc: &ty = &src;`
 473         let statement = self.make_statement(
 474             StatementKind::Assign(
 475                 ref_loc.clone(),
 476                 box Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
 477             )
 478         );
 479
 480         // `let loc = Clone::clone(ref_loc);`
 481         self.block(vec![statement], TerminatorKind::Call {
 482             func,
 483             args: vec![Operand::Move(ref_loc)],
 484             destination: Some((dest, next)),
 485             cleanup: Some(cleanup),
 486             from_hir_call: true,
 487         }, false);
 488     }
 489
 490     fn loop_header(
 491         &mut self,
 492         beg: Place<'tcx>,
 493         end: Place<'tcx>,
 494         loop_body: BasicBlock,
 495         loop_end: BasicBlock,
 496         is_cleanup: bool
 497     ) {
 498         let tcx = self.tcx;
 499
 500         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 501         let compute_cond = self.make_statement(
 502             StatementKind::Assign(
 503                 cond.clone(),
 504                 box Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 505             )
 506         );
 507
 508         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 509         self.block(
 510             vec![compute_cond],
 511             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 512             is_cleanup
 513         );
 514     }
 515
 516     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 517         box Constant {
 518             span: self.span,
 519             ty: self.tcx.types.usize,
 520             user_ty: None,
 521             literal: ty::Const::from_usize(self.tcx, value),
 522         }
 523     }
 524
 525     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 526         let tcx = self.tcx;
 527         let span = self.span;
 528
 529         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 530         let end = self.make_place(Mutability::Not, tcx.types.usize);
 531
 532         // BB #0
 533         // `let mut beg = 0;`
 534         // `let end = len;`
 535         // `goto #1;`
 536         let inits = vec![
 537             self.make_statement(
 538                 StatementKind::Assign(
 539                     Place::Base(PlaceBase::Local(beg)),
 540                     box Rvalue::Use(Operand::Constant(self.make_usize(0)))
 541                 )
 542             ),
 543             self.make_statement(
 544                 StatementKind::Assign(
 545                     end.clone(),
 546                     box Rvalue::Use(Operand::Constant(self.make_usize(len)))
 547                 )
 548             )
 549         ];
 550         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 551
 552         // BB #1: loop {
 553         //     BB #2;
 554         //     BB #3;
 555         // }
 556         // BB #4;
 557         self.loop_header(Place::Base(PlaceBase::Local(beg)),
 558                          end,
 559                          BasicBlock::new(2),
 560                          BasicBlock::new(4),
 561                          false);
 562
 563         // BB #2
 564         // `dest[i] = Clone::clone(src[beg])`;
 565         // Goto #3 if ok, #5 if unwinding happens.
 566         let dest_field = dest.clone().index(beg);
 567         let src_field = src.index(beg);
 568         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 569                              BasicBlock::new(5));
 570
 571         // BB #3
 572         // `beg = beg + 1;`
 573         // `goto #1`;
 574         let statements = vec![
 575             self.make_statement(
 576                 StatementKind::Assign(
 577                     Place::Base(PlaceBase::Local(beg)),
 578                     box Rvalue::BinaryOp(
 579                         BinOp::Add,
 580                         Operand::Copy(Place::Base(PlaceBase::Local(beg))),
 581                         Operand::Constant(self.make_usize(1))
 582                     )
 583                 )
 584             )
 585         ];
 586         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 587
 588         // BB #4
 589         // `return dest;`
 590         self.block(vec![], TerminatorKind::Return, false);
 591
 592         // BB #5 (cleanup)
 593         // `let end = beg;`
 594         // `let mut beg = 0;`
 595         // goto #6;
 596         let end = beg;
 597         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 598         let init = self.make_statement(
 599             StatementKind::Assign(
 600                 Place::Base(PlaceBase::Local(beg)),
 601                 box Rvalue::Use(Operand::Constant(self.make_usize(0)))
 602             )
 603         );
 604         self.block(vec![init], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 605
 606         // BB #6 (cleanup): loop {
 607         //     BB #7;
 608         //     BB #8;
 609         // }
 610         // BB #9;
 611         self.loop_header(Place::Base(PlaceBase::Local(beg)), Place::Base(PlaceBase::Local(end)),
 612                          BasicBlock::new(7), BasicBlock::new(9), true);
 613
 614         // BB #7 (cleanup)
 615         // `drop(dest[beg])`;
 616         self.block(vec![], TerminatorKind::Drop {
 617             location: dest.index(beg),
 618             target: BasicBlock::new(8),
 619             unwind: None,
 620         }, true);
 621
 622         // BB #8 (cleanup)
 623         // `beg = beg + 1;`
 624         // `goto #6;`
 625         let statement = self.make_statement(
 626             StatementKind::Assign(
 627                 Place::Base(PlaceBase::Local(beg)),
 628                 box Rvalue::BinaryOp(
 629                     BinOp::Add,
 630                     Operand::Copy(Place::Base(PlaceBase::Local(beg))),
 631                     Operand::Constant(self.make_usize(1))
 632                 )
 633             )
 634         );
 635         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 636
 637         // BB #9 (resume)
 638         self.block(vec![], TerminatorKind::Resume, true);
 639     }
 640
 641     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 642                           src: Place<'tcx>, tys: I)
 643             where I: Iterator<Item = Ty<'tcx>> {
 644         let mut previous_field = None;
 645         for (i, ity) in tys.enumerate() {
 646             let field = Field::new(i);
 647             let src_field = src.clone().field(field, ity);
 648
 649             let dest_field = dest.clone().field(field, ity);
 650
 651             // #(2i + 1) is the cleanup block for the previous clone operation
 652             let cleanup_block = self.block_index_offset(1);
 653             // #(2i + 2) is the next cloning block
 654             // (or the Return terminator if this is the last block)
 655             let next_block = self.block_index_offset(2);
 656
 657             // BB #(2i)
 658             // `dest.i = Clone::clone(&src.i);`
 659             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 660             self.make_clone_call(
 661                 dest_field.clone(),
 662                 src_field,
 663                 ity,
 664                 next_block,
 665                 cleanup_block,
 666             );
 667
 668             // BB #(2i + 1) (cleanup)
 669             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 670                 // Drop previous field and goto previous cleanup block.
 671                 self.block(vec![], TerminatorKind::Drop {
 672                     location: previous_field,
 673                     target: previous_cleanup,
 674                     unwind: None,
 675                 }, true);
 676             } else {
 677                 // Nothing to drop, just resume.
 678                 self.block(vec![], TerminatorKind::Resume, true);
 679             }
 680
 681             previous_field = Some((dest_field, cleanup_block));
 682         }
 683
 684         self.block(vec![], TerminatorKind::Return, false);
 685     }
 686 }
 687
 688 /// Builds a "call" shim for `def_id`. The shim calls the
 689 /// function specified by `call_kind`, first adjusting its first
 690 /// argument according to `rcvr_adjustment`.
 691 ///
 692 /// If `untuple_args` is a vec of types, the second argument of the
 693 /// function will be untupled as these types.
 694 fn build_call_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 695                              def_id: DefId,
 696                              rcvr_adjustment: Adjustment,
 697                              call_kind: CallKind,
 698                              untuple_args: Option<&[Ty<'tcx>]>)
 699                              -> Body<'tcx>
 700 {
 701     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 702             call_kind={:?}, untuple_args={:?})",
 703            def_id, rcvr_adjustment, call_kind, untuple_args);
 704
 705     let sig = tcx.fn_sig(def_id);
 706     let sig = tcx.erase_late_bound_regions(&sig);
 707     let span = tcx.def_span(def_id);
 708
 709     debug!("build_call_shim: sig={:?}", sig);
 710
 711     let mut local_decls = local_decls_for_sig(&sig, span);
 712     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 713
 714     let rcvr_arg = Local::new(1+0);
 715     let rcvr_l = Place::Base(PlaceBase::Local(rcvr_arg));
 716     let mut statements = vec![];
 717
 718     let rcvr = match rcvr_adjustment {
 719         Adjustment::Identity => Operand::Move(rcvr_l),
 720         Adjustment::Deref => Operand::Copy(rcvr_l.deref()),
 721         Adjustment::DerefMove => {
 722             // fn(Self, ...) -> fn(*mut Self, ...)
 723             let arg_ty = local_decls[rcvr_arg].ty;
 724             assert!(arg_ty.is_self());
 725             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 726
 727             Operand::Move(rcvr_l.deref())
 728         }
 729         Adjustment::RefMut => {
 730             // let rcvr = &mut rcvr;
 731             let ref_rcvr = local_decls.push(temp_decl(
 732                 Mutability::Not,
 733                 tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 734                     ty: sig.inputs()[0],
 735                     mutbl: hir::Mutability::MutMutable
 736                 }),
 737                 span
 738             ));
 739             let borrow_kind = BorrowKind::Mut {
 740                 allow_two_phase_borrow: false,
 741             };
 742             statements.push(Statement {
 743                 source_info,
 744                 kind: StatementKind::Assign(
 745                     Place::Base(PlaceBase::Local(ref_rcvr)),
 746                     box Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
 747                 )
 748             });
 749             Operand::Move(Place::Base(PlaceBase::Local(ref_rcvr)))
 750         }
 751     };
 752
 753     let (callee, mut args) = match call_kind {
 754         CallKind::Indirect => (rcvr, vec![]),
 755         CallKind::Direct(def_id) => {
 756             let ty = tcx.type_of(def_id);
 757             (Operand::Constant(box Constant {
 758                 span,
 759                 ty,
 760                 user_ty: None,
 761                 literal: ty::Const::zero_sized(tcx, ty),
 762              }),
 763              vec![rcvr])
 764         }
 765     };
 766
 767     if let Some(untuple_args) = untuple_args {
 768         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 769             let arg_place = Place::Base(PlaceBase::Local(Local::new(1+1)));
 770             Operand::Move(arg_place.field(Field::new(i), *ity))
 771         }));
 772     } else {
 773         args.extend((1..sig.inputs().len()).map(|i| {
 774             Operand::Move(Place::Base(PlaceBase::Local(Local::new(1+i))))
 775         }));
 776     }
 777
 778     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 779     let mut blocks = IndexVec::with_capacity(n_blocks);
 780     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 781         blocks.push(BasicBlockData {
 782             statements,
 783             terminator: Some(Terminator { source_info, kind }),
 784             is_cleanup
 785         })
 786     };
 787
 788     // BB #0
 789     block(&mut blocks, statements, TerminatorKind::Call {
 790         func: callee,
 791         args,
 792         destination: Some((Place::RETURN_PLACE,
 793                            BasicBlock::new(1))),
 794         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 795             Some(BasicBlock::new(3))
 796         } else {
 797             None
 798         },
 799         from_hir_call: true,
 800     }, false);
 801
 802     if let Adjustment::RefMut = rcvr_adjustment {
 803         // BB #1 - drop for Self
 804         block(&mut blocks, vec![], TerminatorKind::Drop {
 805             location: Place::Base(PlaceBase::Local(rcvr_arg)),
 806             target: BasicBlock::new(2),
 807             unwind: None
 808         }, false);
 809     }
 810     // BB #1/#2 - return
 811     block(&mut blocks, vec![], TerminatorKind::Return, false);
 812     if let Adjustment::RefMut = rcvr_adjustment {
 813         // BB #3 - drop if closure panics
 814         block(&mut blocks, vec![], TerminatorKind::Drop {
 815             location: Place::Base(PlaceBase::Local(rcvr_arg)),
 816             target: BasicBlock::new(4),
 817             unwind: None
 818         }, true);
 819
 820         // BB #4 - resume
 821         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 822     }
 823
 824     let mut mir = Body::new(
 825         blocks,
 826         IndexVec::from_elem_n(
 827             SourceScopeData { span: span, parent_scope: None }, 1
 828         ),
 829         ClearCrossCrate::Clear,
 830         IndexVec::new(),
 831         None,
 832         local_decls,
 833         IndexVec::new(),
 834         sig.inputs().len(),
 835         vec![],
 836         span,
 837         vec![],
 838     );
 839     if let Abi::RustCall = sig.abi {
 840         mir.spread_arg = Some(Local::new(sig.inputs().len()));
 841     }
 842     mir
 843 }
 844
 845 pub fn build_adt_ctor<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
 846                                       ctor_id: hir::HirId,
 847                                       fields: &[hir::StructField],
 848                                       span: Span)
 849                                       -> Body<'tcx>
 850 {
 851     let tcx = infcx.tcx;
 852     let gcx = tcx.global_tcx();
 853     let def_id = tcx.hir().local_def_id_from_hir_id(ctor_id);
 854     let param_env = gcx.param_env(def_id);
 855
 856     // Normalize the sig.
 857     let sig = gcx.fn_sig(def_id)
 858         .no_bound_vars()
 859         .expect("LBR in ADT constructor signature");
 860     let sig = gcx.normalize_erasing_regions(param_env, sig);
 861
 862     let (adt_def, substs) = match sig.output().sty {
 863         ty::Adt(adt_def, substs) => (adt_def, substs),
 864         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 865     };
 866
 867     debug!("build_ctor: def_id={:?} sig={:?} fields={:?}", def_id, sig, fields);
 868
 869     let local_decls = local_decls_for_sig(&sig, span);
 870
 871     let source_info = SourceInfo {
 872         span,
 873         scope: OUTERMOST_SOURCE_SCOPE
 874     };
 875
 876     let variant_no = if adt_def.is_enum() {
 877         adt_def.variant_index_with_ctor_id(def_id)
 878     } else {
 879         VariantIdx::new(0)
 880     };
 881
 882     // return = ADT(arg0, arg1, ...); return
 883     let start_block = BasicBlockData {
 884         statements: vec![Statement {
 885             source_info,
 886             kind: StatementKind::Assign(
 887                 Place::RETURN_PLACE,
 888                 box Rvalue::Aggregate(
 889                     box AggregateKind::Adt(adt_def, variant_no, substs, None, None),
 890                     (1..sig.inputs().len()+1).map(|i| {
 891                         Operand::Move(Place::Base(PlaceBase::Local(Local::new(i))))
 892                     }).collect()
 893                 )
 894             )
 895         }],
 896         terminator: Some(Terminator {
 897             source_info,
 898             kind: TerminatorKind::Return,
 899         }),
 900         is_cleanup: false
 901     };
 902
 903     Body::new(
 904         IndexVec::from_elem_n(start_block, 1),
 905         IndexVec::from_elem_n(
 906             SourceScopeData { span: span, parent_scope: None }, 1
 907         ),
 908         ClearCrossCrate::Clear,
 909         IndexVec::new(),
 910         None,
 911         local_decls,
 912         IndexVec::new(),
 913         sig.inputs().len(),
 914         vec![],
 915         span,
 916         vec![],
 917     )
 918 }