src/librustc_mir/shim.rs

   1 use rustc::hir;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::*;
   4 use rustc::ty::{self, Ty, TyCtxt};
   5 use rustc::ty::layout::VariantIdx;
   6 use rustc::ty::subst::{Subst, InternalSubsts};
   7 use rustc::ty::query::Providers;
   8
   9 use rustc_index::vec::{IndexVec, Idx};
  10
  11 use rustc_target::spec::abi::Abi;
  12 use syntax_pos::{Span, sym};
  13
  14 use std::fmt;
  15 use std::iter;
  16
  17 use crate::transform::{
  18     add_moves_for_packed_drops, add_call_guards,
  19     remove_noop_landing_pads, no_landing_pads, simplify, run_passes
  20 };
  21 use crate::util::elaborate_drops::{self, DropElaborator, DropStyle, DropFlagMode};
  22 use crate::util::patch::MirPatch;
  23 use crate::util::expand_aggregate;
  24
  25 pub fn provide(providers: &mut Providers<'_>) {
  26     providers.mir_shims = make_shim;
  27 }
  28
  29 fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
  30     debug!("make_shim({:?})", instance);
  31
  32     let mut result = match instance {
  33         ty::InstanceDef::Item(..) =>
  34             bug!("item {:?} passed to make_shim", instance),
  35         ty::InstanceDef::VtableShim(def_id) => {
  36             build_call_shim(
  37                 tcx,
  38                 def_id,
  39                 Adjustment::DerefMove,
  40                 CallKind::Direct(def_id),
  41                 None,
  42             )
  43         }
  44         ty::InstanceDef::FnPtrShim(def_id, ty) => {
  45             let trait_ = tcx.trait_of_item(def_id).unwrap();
  46             let adjustment = match tcx.lang_items().fn_trait_kind(trait_) {
  47                 Some(ty::ClosureKind::FnOnce) => Adjustment::Identity,
  48                 Some(ty::ClosureKind::FnMut) |
  49                 Some(ty::ClosureKind::Fn) => Adjustment::Deref,
  50                 None => bug!("fn pointer {:?} is not an fn", ty)
  51             };
  52             // HACK: we need the "real" argument types for the MIR,
  53             // but because our substs are (Self, Args), where Args
  54             // is a tuple, we must include the *concrete* argument
  55             // types in the MIR. They will be substituted again with
  56             // the param-substs, but because they are concrete, this
  57             // will not do any harm.
  58             let sig = tcx.erase_late_bound_regions(&ty.fn_sig(tcx));
  59             let arg_tys = sig.inputs();
  60
  61             build_call_shim(
  62                 tcx,
  63                 def_id,
  64                 adjustment,
  65                 CallKind::Indirect,
  66                 Some(arg_tys)
  67             )
  68         }
  69         // We are generating a call back to our def-id, which the
  70         // codegen backend knows to turn to an actual virtual call.
  71         ty::InstanceDef::Virtual(def_id, _) |
  72         // ...or we are generating a direct call to a function for which indirect calls must be
  73         // codegen'd differently than direct ones (example: #[track_caller])
  74         ty::InstanceDef::ReifyShim(def_id) => {
  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
  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, None, MirPhase::Const, &[
 119         &add_moves_for_packed_drops::AddMovesForPackedDrops,
 120         &no_landing_pads::NoLandingPads::new(tcx),
 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         source_info,
 152         internal: false,
 153         local_info: LocalInfo::Other,
 154         is_block_tail: None,
 155     }
 156 }
 157
 158 fn local_decls_for_sig<'tcx>(sig: &ty::FnSig<'tcx>, span: Span)
 159     -> IndexVec<Local, LocalDecl<'tcx>>
 160 {
 161     iter::once(temp_decl(Mutability::Mut, sig.output(), span))
 162         .chain(sig.inputs().iter().map(
 163             |ity| temp_decl(Mutability::Not, ity, span)))
 164         .collect()
 165 }
 166
 167 fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>) -> Body<'tcx> {
 168     debug!("build_drop_shim(def_id={:?}, ty={:?})", def_id, ty);
 169
 170     // Check if this is a generator, if so, return the drop glue for it
 171     if let Some(&ty::TyS { kind: ty::Generator(gen_def_id, substs, _), .. }) = ty {
 172         let body = &**tcx.optimized_mir(gen_def_id).generator_drop.as_ref().unwrap();
 173         return body.subst(tcx, substs);
 174     }
 175
 176     let substs = if let Some(ty) = ty {
 177         tcx.intern_substs(&[ty.into()])
 178     } else {
 179         InternalSubsts::identity_for_item(tcx, def_id)
 180     };
 181     let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 182     let sig = tcx.erase_late_bound_regions(&sig);
 183     let span = tcx.def_span(def_id);
 184
 185     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 186
 187     let return_block = BasicBlock::new(1);
 188     let mut blocks = IndexVec::with_capacity(2);
 189     let block = |blocks: &mut IndexVec<_, _>, kind| {
 190         blocks.push(BasicBlockData {
 191             statements: vec![],
 192             terminator: Some(Terminator { source_info, kind }),
 193             is_cleanup: false
 194         })
 195     };
 196     block(&mut blocks, TerminatorKind::Goto { target: return_block });
 197     block(&mut blocks, TerminatorKind::Return);
 198
 199     let mut body = Body::new(
 200         blocks,
 201         IndexVec::from_elem_n(
 202             SourceScopeData { span: span, parent_scope: None }, 1
 203         ),
 204         ClearCrossCrate::Clear,
 205         local_decls_for_sig(&sig, span),
 206         IndexVec::new(),
 207         sig.inputs().len(),
 208         vec![],
 209         span,
 210         vec![],
 211         None,
 212     );
 213
 214     if let Some(..) = ty {
 215         // The first argument (index 0), but add 1 for the return value.
 216         let dropee_ptr = Place::from(Local::new(1+0));
 217         if tcx.sess.opts.debugging_opts.mir_emit_retag {
 218             // Function arguments should be retagged, and we make this one raw.
 219             body.basic_blocks_mut()[START_BLOCK].statements.insert(0, Statement {
 220                 source_info,
 221                 kind: StatementKind::Retag(RetagKind::Raw, box(dropee_ptr.clone())),
 222             });
 223         }
 224         let patch = {
 225             let param_env = tcx.param_env(def_id).with_reveal_all();
 226             let mut elaborator = DropShimElaborator {
 227                 body: &body,
 228                 patch: MirPatch::new(&body),
 229                 tcx,
 230                 param_env
 231             };
 232             let dropee = tcx.mk_place_deref(dropee_ptr);
 233             let resume_block = elaborator.patch.resume_block();
 234             elaborate_drops::elaborate_drop(
 235                 &mut elaborator,
 236                 source_info,
 237                 &dropee,
 238                 (),
 239                 return_block,
 240                 elaborate_drops::Unwind::To(resume_block),
 241                 START_BLOCK
 242             );
 243             elaborator.patch
 244         };
 245         patch.apply(&mut body);
 246     }
 247
 248     body
 249 }
 250
 251 pub struct DropShimElaborator<'a, 'tcx> {
 252     pub body: &'a Body<'tcx>,
 253     pub patch: MirPatch<'tcx>,
 254     pub tcx: TyCtxt<'tcx>,
 255     pub param_env: ty::ParamEnv<'tcx>,
 256 }
 257
 258 impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
 259     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
 260         Ok(())
 261     }
 262 }
 263
 264 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
 265     type Path = ();
 266
 267     fn patch(&mut self) -> &mut MirPatch<'tcx> { &mut self.patch }
 268     fn body(&self) -> &'a Body<'tcx> { self.body }
 269     fn tcx(&self) -> TyCtxt<'tcx> {
 270         self.tcx
 271         }
 272     fn param_env(&self) -> ty::ParamEnv<'tcx> { self.param_env }
 273
 274     fn drop_style(&self, _path: Self::Path, mode: DropFlagMode) -> DropStyle {
 275         if let DropFlagMode::Shallow = mode {
 276             DropStyle::Static
 277         } else {
 278             DropStyle::Open
 279         }
 280     }
 281
 282     fn get_drop_flag(&mut self, _path: Self::Path) -> Option<Operand<'tcx>> {
 283         None
 284     }
 285
 286     fn clear_drop_flag(&mut self, _location: Location, _path: Self::Path, _mode: DropFlagMode) {
 287     }
 288
 289     fn field_subpath(&self, _path: Self::Path, _field: Field) -> Option<Self::Path> {
 290         None
 291     }
 292     fn deref_subpath(&self, _path: Self::Path) -> Option<Self::Path> {
 293         None
 294     }
 295     fn downcast_subpath(&self, _path: Self::Path, _variant: VariantIdx) -> Option<Self::Path> {
 296         Some(())
 297     }
 298     fn array_subpath(&self, _path: Self::Path, _index: u32, _size: u32) -> Option<Self::Path> {
 299         None
 300     }
 301 }
 302
 303 /// Builds a `Clone::clone` shim for `self_ty`. Here, `def_id` is `Clone::clone`.
 304 fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
 305     debug!("build_clone_shim(def_id={:?})", def_id);
 306
 307     let param_env = tcx.param_env(def_id);
 308
 309     let mut builder = CloneShimBuilder::new(tcx, def_id, self_ty);
 310     let is_copy = self_ty.is_copy_modulo_regions(tcx, param_env, builder.span);
 311
 312     let dest = Place::return_place();
 313     let src = tcx.mk_place_deref(Place::from(Local::new(1+0)));
 314
 315     match self_ty.kind {
 316         _ if is_copy => builder.copy_shim(),
 317         ty::Array(ty, len) => {
 318             let len = len.eval_usize(tcx, param_env);
 319             builder.array_shim(dest, src, ty, len)
 320         }
 321         ty::Closure(def_id, substs) => {
 322             builder.tuple_like_shim(
 323                 dest, src,
 324                 substs.as_closure().upvar_tys(def_id, tcx)
 325             )
 326         }
 327         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
 328         _ => {
 329             bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty)
 330         }
 331     };
 332
 333     builder.into_mir()
 334 }
 335
 336 struct CloneShimBuilder<'tcx> {
 337     tcx: TyCtxt<'tcx>,
 338     def_id: DefId,
 339     local_decls: IndexVec<Local, LocalDecl<'tcx>>,
 340     blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>,
 341     span: Span,
 342     sig: ty::FnSig<'tcx>,
 343 }
 344
 345 impl CloneShimBuilder<'tcx> {
 346     fn new(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Self {
 347         // we must subst the self_ty because it's
 348         // otherwise going to be TySelf and we can't index
 349         // or access fields of a Place of type TySelf.
 350         let substs = tcx.mk_substs_trait(self_ty, &[]);
 351         let sig = tcx.fn_sig(def_id).subst(tcx, substs);
 352         let sig = tcx.erase_late_bound_regions(&sig);
 353         let span = tcx.def_span(def_id);
 354
 355         CloneShimBuilder {
 356             tcx,
 357             def_id,
 358             local_decls: local_decls_for_sig(&sig, span),
 359             blocks: IndexVec::new(),
 360             span,
 361             sig,
 362         }
 363     }
 364
 365     fn into_mir(self) -> Body<'tcx> {
 366         Body::new(
 367             self.blocks,
 368             IndexVec::from_elem_n(
 369                 SourceScopeData { span: self.span, parent_scope: None }, 1
 370             ),
 371             ClearCrossCrate::Clear,
 372             self.local_decls,
 373             IndexVec::new(),
 374             self.sig.inputs().len(),
 375             vec![],
 376             self.span,
 377             vec![],
 378             None,
 379         )
 380     }
 381
 382     fn source_info(&self) -> SourceInfo {
 383         SourceInfo { span: self.span, scope: OUTERMOST_SOURCE_SCOPE }
 384     }
 385
 386     fn block(
 387         &mut self,
 388         statements: Vec<Statement<'tcx>>,
 389         kind: TerminatorKind<'tcx>,
 390         is_cleanup: bool
 391     ) -> BasicBlock {
 392         let source_info = self.source_info();
 393         self.blocks.push(BasicBlockData {
 394             statements,
 395             terminator: Some(Terminator { source_info, kind }),
 396             is_cleanup,
 397         })
 398     }
 399
 400     /// Gives the index of an upcoming BasicBlock, with an offset.
 401     /// offset=0 will give you the index of the next BasicBlock,
 402     /// offset=1 will give the index of the next-to-next block,
 403     /// offset=-1 will give you the index of the last-created block
 404     fn block_index_offset(&mut self, offset: usize) -> BasicBlock {
 405         BasicBlock::new(self.blocks.len() + offset)
 406     }
 407
 408     fn make_statement(&self, kind: StatementKind<'tcx>) -> Statement<'tcx> {
 409         Statement {
 410             source_info: self.source_info(),
 411             kind,
 412         }
 413     }
 414
 415     fn copy_shim(&mut self) {
 416         let rcvr = self.tcx.mk_place_deref(Place::from(Local::new(1+0)));
 417         let ret_statement = self.make_statement(
 418             StatementKind::Assign(
 419                 box(
 420                     Place::return_place(),
 421                     Rvalue::Use(Operand::Copy(rcvr))
 422                 )
 423             )
 424         );
 425         self.block(vec![ret_statement], TerminatorKind::Return, false);
 426     }
 427
 428     fn make_place(&mut self, mutability: Mutability, ty: Ty<'tcx>) -> Place<'tcx> {
 429         let span = self.span;
 430         Place::from(self.local_decls.push(temp_decl(mutability, ty, span)))
 431     }
 432
 433     fn make_clone_call(
 434         &mut self,
 435         dest: Place<'tcx>,
 436         src: Place<'tcx>,
 437         ty: Ty<'tcx>,
 438         next: BasicBlock,
 439         cleanup: BasicBlock
 440     ) {
 441         let tcx = self.tcx;
 442
 443         let substs = tcx.mk_substs_trait(ty, &[]);
 444
 445         // `func == Clone::clone(&ty) -> ty`
 446         let func_ty = tcx.mk_fn_def(self.def_id, substs);
 447         let func = Operand::Constant(box Constant {
 448             span: self.span,
 449             user_ty: None,
 450             literal: ty::Const::zero_sized(tcx, func_ty),
 451         });
 452
 453         let ref_loc = self.make_place(
 454             Mutability::Not,
 455             tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 456                 ty,
 457                 mutbl: hir::Mutability::Immutable,
 458             })
 459         );
 460
 461         // `let ref_loc: &ty = &src;`
 462         let statement = self.make_statement(
 463             StatementKind::Assign(
 464                 box(
 465                     ref_loc.clone(),
 466                     Rvalue::Ref(tcx.lifetimes.re_erased, BorrowKind::Shared, src)
 467                 )
 468             )
 469         );
 470
 471         // `let loc = Clone::clone(ref_loc);`
 472         self.block(vec![statement], TerminatorKind::Call {
 473             func,
 474             args: vec![Operand::Move(ref_loc)],
 475             destination: Some((dest, next)),
 476             cleanup: Some(cleanup),
 477             from_hir_call: true,
 478         }, false);
 479     }
 480
 481     fn loop_header(
 482         &mut self,
 483         beg: Place<'tcx>,
 484         end: Place<'tcx>,
 485         loop_body: BasicBlock,
 486         loop_end: BasicBlock,
 487         is_cleanup: bool
 488     ) {
 489         let tcx = self.tcx;
 490
 491         let cond = self.make_place(Mutability::Mut, tcx.types.bool);
 492         let compute_cond = self.make_statement(
 493             StatementKind::Assign(
 494                 box(
 495                     cond.clone(),
 496                     Rvalue::BinaryOp(BinOp::Ne, Operand::Copy(end), Operand::Copy(beg))
 497                 )
 498             )
 499         );
 500
 501         // `if end != beg { goto loop_body; } else { goto loop_end; }`
 502         self.block(
 503             vec![compute_cond],
 504             TerminatorKind::if_(tcx, Operand::Move(cond), loop_body, loop_end),
 505             is_cleanup
 506         );
 507     }
 508
 509     fn make_usize(&self, value: u64) -> Box<Constant<'tcx>> {
 510         box Constant {
 511             span: self.span,
 512             user_ty: None,
 513             literal: ty::Const::from_usize(self.tcx, value),
 514         }
 515     }
 516
 517     fn array_shim(&mut self, dest: Place<'tcx>, src: Place<'tcx>, ty: Ty<'tcx>, len: u64) {
 518         let tcx = self.tcx;
 519         let span = self.span;
 520
 521         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 522         let end = self.make_place(Mutability::Not, tcx.types.usize);
 523
 524         // BB #0
 525         // `let mut beg = 0;`
 526         // `let end = len;`
 527         // `goto #1;`
 528         let inits = vec![
 529             self.make_statement(
 530                 StatementKind::Assign(
 531                     box(
 532                         Place::from(beg),
 533                         Rvalue::Use(Operand::Constant(self.make_usize(0)))
 534                     )
 535                 )
 536             ),
 537             self.make_statement(
 538                 StatementKind::Assign(
 539                     box(
 540                         end.clone(),
 541                         Rvalue::Use(Operand::Constant(self.make_usize(len)))
 542                     )
 543                 )
 544             )
 545         ];
 546         self.block(inits, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 547
 548         // BB #1: loop {
 549         //     BB #2;
 550         //     BB #3;
 551         // }
 552         // BB #4;
 553         self.loop_header(Place::from(beg),
 554                          end,
 555                          BasicBlock::new(2),
 556                          BasicBlock::new(4),
 557                          false);
 558
 559         // BB #2
 560         // `dest[i] = Clone::clone(src[beg])`;
 561         // Goto #3 if ok, #5 if unwinding happens.
 562         let dest_field = self.tcx.mk_place_index(dest.clone(), beg);
 563         let src_field = self.tcx.mk_place_index(src, beg);
 564         self.make_clone_call(dest_field, src_field, ty, BasicBlock::new(3),
 565                              BasicBlock::new(5));
 566
 567         // BB #3
 568         // `beg = beg + 1;`
 569         // `goto #1`;
 570         let statements = vec![
 571             self.make_statement(
 572                 StatementKind::Assign(
 573                     box(
 574                         Place::from(beg),
 575                         Rvalue::BinaryOp(
 576                             BinOp::Add,
 577                             Operand::Copy(Place::from(beg)),
 578                             Operand::Constant(self.make_usize(1))
 579                         )
 580                     )
 581                 )
 582             )
 583         ];
 584         self.block(statements, TerminatorKind::Goto { target: BasicBlock::new(1) }, false);
 585
 586         // BB #4
 587         // `return dest;`
 588         self.block(vec![], TerminatorKind::Return, false);
 589
 590         // BB #5 (cleanup)
 591         // `let end = beg;`
 592         // `let mut beg = 0;`
 593         // goto #6;
 594         let end = beg;
 595         let beg = self.local_decls.push(temp_decl(Mutability::Mut, tcx.types.usize, span));
 596         let init = self.make_statement(
 597             StatementKind::Assign(
 598                 box(
 599                     Place::from(beg),
 600                     Rvalue::Use(Operand::Constant(self.make_usize(0)))
 601                 )
 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::from(beg), Place::from(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: self.tcx.mk_place_index(dest, 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                 box(
 628                     Place::from(beg),
 629                     Rvalue::BinaryOp(
 630                         BinOp::Add,
 631                         Operand::Copy(Place::from(beg)),
 632                         Operand::Constant(self.make_usize(1))
 633                     )
 634                 )
 635             )
 636         );
 637         self.block(vec![statement], TerminatorKind::Goto { target: BasicBlock::new(6) }, true);
 638
 639         // BB #9 (resume)
 640         self.block(vec![], TerminatorKind::Resume, true);
 641     }
 642
 643     fn tuple_like_shim<I>(&mut self, dest: Place<'tcx>,
 644                           src: Place<'tcx>, tys: I)
 645             where I: Iterator<Item = Ty<'tcx>> {
 646         let mut previous_field = None;
 647         for (i, ity) in tys.enumerate() {
 648             let field = Field::new(i);
 649             let src_field = self.tcx.mk_place_field(src.clone(), field, ity);
 650
 651             let dest_field = self.tcx.mk_place_field(dest.clone(), field, ity);
 652
 653             // #(2i + 1) is the cleanup block for the previous clone operation
 654             let cleanup_block = self.block_index_offset(1);
 655             // #(2i + 2) is the next cloning block
 656             // (or the Return terminator if this is the last block)
 657             let next_block = self.block_index_offset(2);
 658
 659             // BB #(2i)
 660             // `dest.i = Clone::clone(&src.i);`
 661             // Goto #(2i + 2) if ok, #(2i + 1) if unwinding happens.
 662             self.make_clone_call(
 663                 dest_field.clone(),
 664                 src_field,
 665                 ity,
 666                 next_block,
 667                 cleanup_block,
 668             );
 669
 670             // BB #(2i + 1) (cleanup)
 671             if let Some((previous_field, previous_cleanup)) = previous_field.take() {
 672                 // Drop previous field and goto previous cleanup block.
 673                 self.block(vec![], TerminatorKind::Drop {
 674                     location: previous_field,
 675                     target: previous_cleanup,
 676                     unwind: None,
 677                 }, true);
 678             } else {
 679                 // Nothing to drop, just resume.
 680                 self.block(vec![], TerminatorKind::Resume, true);
 681             }
 682
 683             previous_field = Some((dest_field, cleanup_block));
 684         }
 685
 686         self.block(vec![], TerminatorKind::Return, false);
 687     }
 688 }
 689
 690 /// Builds a "call" shim for `def_id`. The shim calls the
 691 /// function specified by `call_kind`, first adjusting its first
 692 /// argument according to `rcvr_adjustment`.
 693 ///
 694 /// If `untuple_args` is a vec of types, the second argument of the
 695 /// function will be untupled as these types.
 696 fn build_call_shim<'tcx>(
 697     tcx: TyCtxt<'tcx>,
 698     def_id: DefId,
 699     rcvr_adjustment: Adjustment,
 700     call_kind: CallKind,
 701     untuple_args: Option<&[Ty<'tcx>]>,
 702 ) -> Body<'tcx> {
 703     debug!("build_call_shim(def_id={:?}, rcvr_adjustment={:?}, \
 704             call_kind={:?}, untuple_args={:?})",
 705            def_id, rcvr_adjustment, call_kind, untuple_args);
 706
 707     let sig = tcx.fn_sig(def_id);
 708     let sig = tcx.erase_late_bound_regions(&sig);
 709     let span = tcx.def_span(def_id);
 710
 711     debug!("build_call_shim: sig={:?}", sig);
 712
 713     let mut local_decls = local_decls_for_sig(&sig, span);
 714     let source_info = SourceInfo { span, scope: OUTERMOST_SOURCE_SCOPE };
 715
 716     let rcvr_arg = Local::new(1+0);
 717     let rcvr_l = Place::from(rcvr_arg);
 718     let mut statements = vec![];
 719
 720     let rcvr = match rcvr_adjustment {
 721         Adjustment::Identity => Operand::Move(rcvr_l),
 722         Adjustment::Deref => Operand::Copy(tcx.mk_place_deref(rcvr_l)),
 723         Adjustment::DerefMove => {
 724             // fn(Self, ...) -> fn(*mut Self, ...)
 725             let arg_ty = local_decls[rcvr_arg].ty;
 726             debug_assert!(tcx.generics_of(def_id).has_self && arg_ty == tcx.types.self_param);
 727             local_decls[rcvr_arg].ty = tcx.mk_mut_ptr(arg_ty);
 728
 729             Operand::Move(tcx.mk_place_deref(rcvr_l))
 730         }
 731         Adjustment::RefMut => {
 732             // let rcvr = &mut rcvr;
 733             let ref_rcvr = local_decls.push(temp_decl(
 734                 Mutability::Not,
 735                 tcx.mk_ref(tcx.lifetimes.re_erased, ty::TypeAndMut {
 736                     ty: sig.inputs()[0],
 737                     mutbl: hir::Mutability::Mutable
 738                 }),
 739                 span
 740             ));
 741             let borrow_kind = BorrowKind::Mut {
 742                 allow_two_phase_borrow: false,
 743             };
 744             statements.push(Statement {
 745                 source_info,
 746                 kind: StatementKind::Assign(
 747                     box(
 748                         Place::from(ref_rcvr),
 749                         Rvalue::Ref(tcx.lifetimes.re_erased, borrow_kind, rcvr_l)
 750                     )
 751                 )
 752             });
 753             Operand::Move(Place::from(ref_rcvr))
 754         }
 755     };
 756
 757     let (callee, mut args) = match call_kind {
 758         CallKind::Indirect => (rcvr, vec![]),
 759         CallKind::Direct(def_id) => {
 760             let ty = tcx.type_of(def_id);
 761             (Operand::Constant(box Constant {
 762                 span,
 763                 user_ty: None,
 764                 literal: ty::Const::zero_sized(tcx, ty),
 765              }),
 766              vec![rcvr])
 767         }
 768     };
 769
 770     if let Some(untuple_args) = untuple_args {
 771         args.extend(untuple_args.iter().enumerate().map(|(i, ity)| {
 772             let arg_place = Place::from(Local::new(1+1));
 773             Operand::Move(tcx.mk_place_field(arg_place, Field::new(i), *ity))
 774         }));
 775     } else {
 776         args.extend((1..sig.inputs().len()).map(|i| {
 777             Operand::Move(Place::from(Local::new(1+i)))
 778         }));
 779     }
 780
 781     let n_blocks = if let Adjustment::RefMut = rcvr_adjustment { 5 } else { 2 };
 782     let mut blocks = IndexVec::with_capacity(n_blocks);
 783     let block = |blocks: &mut IndexVec<_, _>, statements, kind, is_cleanup| {
 784         blocks.push(BasicBlockData {
 785             statements,
 786             terminator: Some(Terminator { source_info, kind }),
 787             is_cleanup
 788         })
 789     };
 790
 791     // BB #0
 792     block(&mut blocks, statements, TerminatorKind::Call {
 793         func: callee,
 794         args,
 795         destination: Some((Place::return_place(),
 796                            BasicBlock::new(1))),
 797         cleanup: if let Adjustment::RefMut = rcvr_adjustment {
 798             Some(BasicBlock::new(3))
 799         } else {
 800             None
 801         },
 802         from_hir_call: true,
 803     }, false);
 804
 805     if let Adjustment::RefMut = rcvr_adjustment {
 806         // BB #1 - drop for Self
 807         block(&mut blocks, vec![], TerminatorKind::Drop {
 808             location: Place::from(rcvr_arg),
 809             target: BasicBlock::new(2),
 810             unwind: None
 811         }, false);
 812     }
 813     // BB #1/#2 - return
 814     block(&mut blocks, vec![], TerminatorKind::Return, false);
 815     if let Adjustment::RefMut = rcvr_adjustment {
 816         // BB #3 - drop if closure panics
 817         block(&mut blocks, vec![], TerminatorKind::Drop {
 818             location: Place::from(rcvr_arg),
 819             target: BasicBlock::new(4),
 820             unwind: None
 821         }, true);
 822
 823         // BB #4 - resume
 824         block(&mut blocks, vec![], TerminatorKind::Resume, true);
 825     }
 826
 827     let mut body = Body::new(
 828         blocks,
 829         IndexVec::from_elem_n(
 830             SourceScopeData { span: span, parent_scope: None }, 1
 831         ),
 832         ClearCrossCrate::Clear,
 833         local_decls,
 834         IndexVec::new(),
 835         sig.inputs().len(),
 836         vec![],
 837         span,
 838         vec![],
 839         None,
 840     );
 841     if let Abi::RustCall = sig.abi {
 842         body.spread_arg = Some(Local::new(sig.inputs().len()));
 843     }
 844     body
 845 }
 846
 847 pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> &Body<'_> {
 848     debug_assert!(tcx.is_constructor(ctor_id));
 849
 850     let span = tcx.hir().span_if_local(ctor_id)
 851         .unwrap_or_else(|| bug!("no span for ctor {:?}", ctor_id));
 852
 853     let param_env = tcx.param_env(ctor_id);
 854
 855     // Normalize the sig.
 856     let sig = tcx.fn_sig(ctor_id)
 857         .no_bound_vars()
 858         .expect("LBR in ADT constructor signature");
 859     let sig = tcx.normalize_erasing_regions(param_env, sig);
 860
 861     let (adt_def, substs) = match sig.output().kind {
 862         ty::Adt(adt_def, substs) => (adt_def, substs),
 863         _ => bug!("unexpected type for ADT ctor {:?}", sig.output())
 864     };
 865
 866     debug!("build_ctor: ctor_id={:?} sig={:?}", ctor_id, sig);
 867
 868     let local_decls = local_decls_for_sig(&sig, span);
 869
 870     let source_info = SourceInfo {
 871         span,
 872         scope: OUTERMOST_SOURCE_SCOPE
 873     };
 874
 875     let variant_index = if adt_def.is_enum() {
 876         adt_def.variant_index_with_ctor_id(ctor_id)
 877     } else {
 878         VariantIdx::new(0)
 879     };
 880
 881     // Generate the following MIR:
 882     //
 883     // (return as Variant).field0 = arg0;
 884     // (return as Variant).field1 = arg1;
 885     //
 886     // return;
 887     debug!("build_ctor: variant_index={:?}", variant_index);
 888
 889     let statements = expand_aggregate(
 890         Place::return_place(),
 891         adt_def
 892             .variants[variant_index]
 893             .fields
 894             .iter()
 895             .enumerate()
 896             .map(|(idx, field_def)| (
 897                 Operand::Move(Place::from(Local::new(idx + 1))),
 898                 field_def.ty(tcx, substs),
 899             )),
 900         AggregateKind::Adt(adt_def, variant_index, substs, None, None),
 901         source_info,
 902         tcx,
 903     ).collect();
 904
 905     let start_block = BasicBlockData {
 906         statements,
 907         terminator: Some(Terminator {
 908             source_info,
 909             kind: TerminatorKind::Return,
 910         }),
 911         is_cleanup: false
 912     };
 913
 914     let body = Body::new(
 915         IndexVec::from_elem_n(start_block, 1),
 916         IndexVec::from_elem_n(
 917             SourceScopeData { span: span, parent_scope: None }, 1
 918         ),
 919         ClearCrossCrate::Clear,
 920         local_decls,
 921         IndexVec::new(),
 922         sig.inputs().len(),
 923         vec![],
 924         span,
 925         vec![],
 926         None,
 927     );
 928
 929     crate::util::dump_mir(
 930         tcx,
 931         None,
 932         "mir_map",
 933         &0,
 934         crate::transform::MirSource::item(ctor_id),
 935         &body,
 936         |_, _| Ok(()),
 937     );
 938
 939     tcx.arena.alloc(body)
 940 }