src/librustc_mir/transform/inline.rs

   1 //! Inlining pass for MIR functions
   2
   3 use rustc::hir::CodegenFnAttrFlags;
   4 use rustc::hir::def_id::DefId;
   5
   6 use rustc_data_structures::bit_set::BitSet;
   7 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
   8
   9 use rustc::mir::*;
  10 use rustc::mir::visit::*;
  11 use rustc::ty::{self, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
  12 use rustc::ty::subst::{Subst, SubstsRef};
  13
  14 use std::collections::VecDeque;
  15 use std::iter;
  16 use crate::transform::{MirPass, MirSource};
  17 use super::simplify::{remove_dead_blocks, CfgSimplifier};
  18
  19 use syntax::attr;
  20 use rustc_target::spec::abi::Abi;
  21
  22 const DEFAULT_THRESHOLD: usize = 50;
  23 const HINT_THRESHOLD: usize = 100;
  24
  25 const INSTR_COST: usize = 5;
  26 const CALL_PENALTY: usize = 25;
  27
  28 const UNKNOWN_SIZE_COST: usize = 10;
  29
  30 pub struct Inline;
  31
  32 #[derive(Copy, Clone, Debug)]
  33 struct CallSite<'tcx> {
  34     callee: DefId,
  35     substs: SubstsRef<'tcx>,
  36     bb: BasicBlock,
  37     location: SourceInfo,
  38 }
  39
  40 impl MirPass for Inline {
  41     fn run_pass<'tcx>(&self, tcx: TyCtxt<'tcx>, source: MirSource<'tcx>, body: &mut Body<'tcx>) {
  42         if tcx.sess.opts.debugging_opts.mir_opt_level >= 2 {
  43             Inliner { tcx, source }.run_pass(body);
  44         }
  45     }
  46 }
  47
  48 struct Inliner<'tcx> {
  49     tcx: TyCtxt<'tcx>,
  50     source: MirSource<'tcx>,
  51 }
  52
  53 impl Inliner<'tcx> {
  54     fn run_pass(&self, caller_body: &mut Body<'tcx>) {
  55         // Keep a queue of callsites to try inlining on. We take
  56         // advantage of the fact that queries detect cycles here to
  57         // allow us to try and fetch the fully optimized MIR of a
  58         // call; if it succeeds, we can inline it and we know that
  59         // they do not call us.  Otherwise, we just don't try to
  60         // inline.
  61         //
  62         // We use a queue so that we inline "broadly" before we inline
  63         // in depth. It is unclear if this is the best heuristic,
  64         // really, but that's true of all the heuristics in this
  65         // file. =)
  66
  67         let mut callsites = VecDeque::new();
  68
  69         let param_env = self.tcx.param_env(self.source.def_id());
  70
  71         // Only do inlining into fn bodies.
  72         let id = self.tcx.hir().as_local_hir_id(self.source.def_id()).unwrap();
  73         if self.tcx.hir().body_owner_kind(id).is_fn_or_closure()
  74             && self.source.promoted.is_none()
  75         {
  76             for (bb, bb_data) in caller_body.basic_blocks().iter_enumerated() {
  77                 if let Some(callsite) = self.get_valid_function_call(bb,
  78                                                                     bb_data,
  79                                                                     caller_body,
  80                                                                     param_env) {
  81                     callsites.push_back(callsite);
  82                 }
  83             }
  84         } else {
  85             return;
  86         }
  87
  88         let mut local_change;
  89         let mut changed = false;
  90
  91         loop {
  92             local_change = false;
  93             while let Some(callsite) = callsites.pop_front() {
  94                 debug!("checking whether to inline callsite {:?}", callsite);
  95                 if !self.tcx.is_mir_available(callsite.callee) {
  96                     debug!("checking whether to inline callsite {:?} - MIR unavailable", callsite);
  97                     continue;
  98                 }
  99
 100                 let self_node_id = self.tcx.hir().as_local_node_id(self.source.def_id()).unwrap();
 101                 let callee_node_id = self.tcx.hir().as_local_node_id(callsite.callee);
 102
 103                 let callee_body = if let Some(callee_node_id) = callee_node_id {
 104                     // Avoid a cycle here by only using `optimized_mir` only if we have
 105                     // a lower node id than the callee. This ensures that the callee will
 106                     // not inline us. This trick only works without incremental compilation.
 107                     // So don't do it if that is enabled.
 108                     if !self.tcx.dep_graph.is_fully_enabled()
 109                         && self_node_id.as_u32() < callee_node_id.as_u32() {
 110                         self.tcx.optimized_mir(callsite.callee)
 111                     } else {
 112                         continue;
 113                     }
 114                 } else {
 115                     // This cannot result in a cycle since the callee MIR is from another crate
 116                     // and is already optimized.
 117                     self.tcx.optimized_mir(callsite.callee)
 118                 };
 119
 120                 let callee_body = if self.consider_optimizing(callsite, callee_body) {
 121                     self.tcx.subst_and_normalize_erasing_regions(
 122                         &callsite.substs,
 123                         param_env,
 124                         callee_body,
 125                     )
 126                 } else {
 127                     continue;
 128                 };
 129
 130                 let start = caller_body.basic_blocks().len();
 131                 debug!("attempting to inline callsite {:?} - body={:?}", callsite, callee_body);
 132                 if !self.inline_call(callsite, caller_body, callee_body) {
 133                     debug!("attempting to inline callsite {:?} - failure", callsite);
 134                     continue;
 135                 }
 136                 debug!("attempting to inline callsite {:?} - success", callsite);
 137
 138                 // Add callsites from inlined function
 139                 for (bb, bb_data) in caller_body.basic_blocks().iter_enumerated().skip(start) {
 140                     if let Some(new_callsite) = self.get_valid_function_call(bb,
 141                                                                              bb_data,
 142                                                                              caller_body,
 143                                                                              param_env) {
 144                         // Don't inline the same function multiple times.
 145                         if callsite.callee != new_callsite.callee {
 146                             callsites.push_back(new_callsite);
 147                         }
 148                     }
 149                 }
 150
 151                 local_change = true;
 152                 changed = true;
 153             }
 154
 155             if !local_change {
 156                 break;
 157             }
 158         }
 159
 160         // Simplify if we inlined anything.
 161         if changed {
 162             debug!("running simplify cfg on {:?}", self.source);
 163             CfgSimplifier::new(caller_body).simplify();
 164             remove_dead_blocks(caller_body);
 165         }
 166     }
 167
 168     fn get_valid_function_call(&self,
 169                                bb: BasicBlock,
 170                                bb_data: &BasicBlockData<'tcx>,
 171                                caller_body: &Body<'tcx>,
 172                                param_env: ParamEnv<'tcx>,
 173     ) -> Option<CallSite<'tcx>> {
 174         // Don't inline calls that are in cleanup blocks.
 175         if bb_data.is_cleanup { return None; }
 176
 177         // Only consider direct calls to functions
 178         let terminator = bb_data.terminator();
 179         if let TerminatorKind::Call { func: ref op, .. } = terminator.kind {
 180             if let ty::FnDef(callee_def_id, substs) = op.ty(caller_body, self.tcx).sty {
 181                 let instance = Instance::resolve(self.tcx,
 182                                                  param_env,
 183                                                  callee_def_id,
 184                                                  substs)?;
 185
 186                 if let InstanceDef::Virtual(..) = instance.def {
 187                     return None;
 188                 }
 189
 190                 return Some(CallSite {
 191                     callee: instance.def_id(),
 192                     substs: instance.substs,
 193                     bb,
 194                     location: terminator.source_info
 195                 });
 196             }
 197         }
 198
 199         None
 200     }
 201
 202     fn consider_optimizing(&self,
 203                            callsite: CallSite<'tcx>,
 204                            callee_body: &Body<'tcx>)
 205                            -> bool
 206     {
 207         debug!("consider_optimizing({:?})", callsite);
 208         self.should_inline(callsite, callee_body)
 209             && self.tcx.consider_optimizing(|| format!("Inline {:?} into {:?}",
 210                                                        callee_body.span,
 211                                                        callsite))
 212     }
 213
 214     fn should_inline(&self,
 215                      callsite: CallSite<'tcx>,
 216                      callee_body: &Body<'tcx>)
 217                      -> bool
 218     {
 219         debug!("should_inline({:?})", callsite);
 220         let tcx = self.tcx;
 221
 222         // Don't inline closures that have capture debuginfo
 223         // FIXME: Handle closures better
 224         if callee_body.__upvar_debuginfo_codegen_only_do_not_use.len() > 0 {
 225             debug!("    upvar debuginfo present - not inlining");
 226             return false;
 227         }
 228
 229         // Cannot inline generators which haven't been transformed yet
 230         if callee_body.yield_ty.is_some() {
 231             debug!("    yield ty present - not inlining");
 232             return false;
 233         }
 234
 235         // Do not inline {u,i}128 lang items, codegen const eval depends
 236         // on detecting calls to these lang items and intercepting them
 237         if tcx.is_binop_lang_item(callsite.callee).is_some() {
 238             debug!("    not inlining 128bit integer lang item");
 239             return false;
 240         }
 241
 242         let codegen_fn_attrs = tcx.codegen_fn_attrs(callsite.callee);
 243
 244         let hinted = match codegen_fn_attrs.inline {
 245             // Just treat inline(always) as a hint for now,
 246             // there are cases that prevent inlining that we
 247             // need to check for first.
 248             attr::InlineAttr::Always => true,
 249             attr::InlineAttr::Never => {
 250                 debug!("`#[inline(never)]` present - not inlining");
 251                 return false
 252             }
 253             attr::InlineAttr::Hint => true,
 254             attr::InlineAttr::None => false,
 255         };
 256
 257         // Only inline local functions if they would be eligible for cross-crate
 258         // inlining. This is to ensure that the final crate doesn't have MIR that
 259         // reference unexported symbols
 260         if callsite.callee.is_local() {
 261             if callsite.substs.non_erasable_generics().count() == 0 && !hinted {
 262                 debug!("    callee is an exported function - not inlining");
 263                 return false;
 264             }
 265         }
 266
 267         let mut threshold = if hinted {
 268             HINT_THRESHOLD
 269         } else {
 270             DEFAULT_THRESHOLD
 271         };
 272
 273         // Significantly lower the threshold for inlining cold functions
 274         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
 275             threshold /= 5;
 276         }
 277
 278         // Give a bonus functions with a small number of blocks,
 279         // We normally have two or three blocks for even
 280         // very small functions.
 281         if callee_body.basic_blocks().len() <= 3 {
 282             threshold += threshold / 4;
 283         }
 284         debug!("    final inline threshold = {}", threshold);
 285
 286         // FIXME: Give a bonus to functions with only a single caller
 287
 288         let param_env = tcx.param_env(self.source.def_id());
 289
 290         let mut first_block = true;
 291         let mut cost = 0;
 292
 293         // Traverse the MIR manually so we can account for the effects of
 294         // inlining on the CFG.
 295         let mut work_list = vec![START_BLOCK];
 296         let mut visited = BitSet::new_empty(callee_body.basic_blocks().len());
 297         while let Some(bb) = work_list.pop() {
 298             if !visited.insert(bb.index()) { continue; }
 299             let blk = &callee_body.basic_blocks()[bb];
 300
 301             for stmt in &blk.statements {
 302                 // Don't count StorageLive/StorageDead in the inlining cost.
 303                 match stmt.kind {
 304                     StatementKind::StorageLive(_) |
 305                     StatementKind::StorageDead(_) |
 306                     StatementKind::Nop => {}
 307                     _ => cost += INSTR_COST
 308                 }
 309             }
 310             let term = blk.terminator();
 311             let mut is_drop = false;
 312             match term.kind {
 313                 TerminatorKind::Drop { ref location, target, unwind } |
 314                 TerminatorKind::DropAndReplace { ref location, target, unwind, .. } => {
 315                     is_drop = true;
 316                     work_list.push(target);
 317                     // If the location doesn't actually need dropping, treat it like
 318                     // a regular goto.
 319                     let ty = location.ty(callee_body, tcx).subst(tcx, callsite.substs).ty;
 320                     if ty.needs_drop(tcx, param_env) {
 321                         cost += CALL_PENALTY;
 322                         if let Some(unwind) = unwind {
 323                             work_list.push(unwind);
 324                         }
 325                     } else {
 326                         cost += INSTR_COST;
 327                     }
 328                 }
 329
 330                 TerminatorKind::Unreachable |
 331                 TerminatorKind::Call { destination: None, .. } if first_block => {
 332                     // If the function always diverges, don't inline
 333                     // unless the cost is zero
 334                     threshold = 0;
 335                 }
 336
 337                 TerminatorKind::Call {func: Operand::Constant(ref f), .. } => {
 338                     if let ty::FnDef(def_id, _) = f.ty.sty {
 339                         // Don't give intrinsics the extra penalty for calls
 340                         let f = tcx.fn_sig(def_id);
 341                         if f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic {
 342                             cost += INSTR_COST;
 343                         } else {
 344                             cost += CALL_PENALTY;
 345                         }
 346                     }
 347                 }
 348                 TerminatorKind::Assert { .. } => cost += CALL_PENALTY,
 349                 _ => cost += INSTR_COST
 350             }
 351
 352             if !is_drop {
 353                 for &succ in term.successors() {
 354                     work_list.push(succ);
 355                 }
 356             }
 357
 358             first_block = false;
 359         }
 360
 361         // Count up the cost of local variables and temps, if we know the size
 362         // use that, otherwise we use a moderately-large dummy cost.
 363
 364         let ptr_size = tcx.data_layout.pointer_size.bytes();
 365
 366         for v in callee_body.vars_and_temps_iter() {
 367             let v = &callee_body.local_decls[v];
 368             let ty = v.ty.subst(tcx, callsite.substs);
 369             // Cost of the var is the size in machine-words, if we know
 370             // it.
 371             if let Some(size) = type_size_of(tcx, param_env.clone(), ty) {
 372                 cost += (size / ptr_size) as usize;
 373             } else {
 374                 cost += UNKNOWN_SIZE_COST;
 375             }
 376         }
 377
 378         if let attr::InlineAttr::Always = codegen_fn_attrs.inline {
 379             debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
 380             true
 381         } else {
 382             if cost <= threshold {
 383                 debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
 384                 true
 385             } else {
 386                 debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
 387                 false
 388             }
 389         }
 390     }
 391
 392     fn inline_call(&self,
 393                    callsite: CallSite<'tcx>,
 394                    caller_body: &mut Body<'tcx>,
 395                    mut callee_body: Body<'tcx>) -> bool {
 396         let terminator = caller_body[callsite.bb].terminator.take().unwrap();
 397         match terminator.kind {
 398             // FIXME: Handle inlining of diverging calls
 399             TerminatorKind::Call { args, destination: Some(destination), cleanup, .. } => {
 400                 debug!("inlined {:?} into {:?}", callsite.callee, self.source);
 401
 402                 let mut local_map = IndexVec::with_capacity(callee_body.local_decls.len());
 403                 let mut scope_map = IndexVec::with_capacity(callee_body.source_scopes.len());
 404                 let mut promoted_map = IndexVec::with_capacity(callee_body.promoted.len());
 405
 406                 for mut scope in callee_body.source_scopes.iter().cloned() {
 407                     if scope.parent_scope.is_none() {
 408                         scope.parent_scope = Some(callsite.location.scope);
 409                         scope.span = callee_body.span;
 410                     }
 411
 412                     scope.span = callsite.location.span;
 413
 414                     let idx = caller_body.source_scopes.push(scope);
 415                     scope_map.push(idx);
 416                 }
 417
 418                 for loc in callee_body.vars_and_temps_iter() {
 419                     let mut local = callee_body.local_decls[loc].clone();
 420
 421                     local.source_info.scope =
 422                         scope_map[local.source_info.scope];
 423                     local.source_info.span = callsite.location.span;
 424                     local.visibility_scope = scope_map[local.visibility_scope];
 425
 426                     let idx = caller_body.local_decls.push(local);
 427                     local_map.push(idx);
 428                 }
 429
 430                 promoted_map.extend(
 431                     callee_body.promoted.iter().cloned().map(|p| caller_body.promoted.push(p))
 432                 );
 433
 434                 // If the call is something like `a[*i] = f(i)`, where
 435                 // `i : &mut usize`, then just duplicating the `a[*i]`
 436                 // Place could result in two different locations if `f`
 437                 // writes to `i`. To prevent this we need to create a temporary
 438                 // borrow of the place and pass the destination as `*temp` instead.
 439                 fn dest_needs_borrow(place: &Place<'_>) -> bool {
 440                     place.iterate(|place_base, place_projection| {
 441                         for proj in place_projection {
 442                             match proj.elem {
 443                                 ProjectionElem::Deref |
 444                                 ProjectionElem::Index(_) => return true,
 445                                 _ => {}
 446                             }
 447                         }
 448
 449                         match place_base {
 450                             // Static variables need a borrow because the callee
 451                             // might modify the same static.
 452                             PlaceBase::Static(_) => true,
 453                             _ => false
 454                         }
 455                     })
 456                 }
 457
 458                 let dest = if dest_needs_borrow(&destination.0) {
 459                     debug!("creating temp for return destination");
 460                     let dest = Rvalue::Ref(
 461                         self.tcx.lifetimes.re_erased,
 462                         BorrowKind::Mut { allow_two_phase_borrow: false },
 463                         destination.0);
 464
 465                     let ty = dest.ty(caller_body, self.tcx);
 466
 467                     let temp = LocalDecl::new_temp(ty, callsite.location.span);
 468
 469                     let tmp = caller_body.local_decls.push(temp);
 470                     let tmp = Place::from(tmp);
 471
 472                     let stmt = Statement {
 473                         source_info: callsite.location,
 474                         kind: StatementKind::Assign(tmp.clone(), box dest)
 475                     };
 476                     caller_body[callsite.bb]
 477                         .statements.push(stmt);
 478                     tmp.deref()
 479                 } else {
 480                     destination.0
 481                 };
 482
 483                 let return_block = destination.1;
 484
 485                 // Copy the arguments if needed.
 486                 let args: Vec<_> = self.make_call_args(args, &callsite, caller_body);
 487
 488                 let bb_len = caller_body.basic_blocks().len();
 489                 let mut integrator = Integrator {
 490                     block_idx: bb_len,
 491                     args: &args,
 492                     local_map,
 493                     scope_map,
 494                     promoted_map,
 495                     _callsite: callsite,
 496                     destination: dest,
 497                     return_block,
 498                     cleanup_block: cleanup,
 499                     in_cleanup_block: false
 500                 };
 501
 502
 503                 for (bb, mut block) in callee_body.basic_blocks_mut().drain_enumerated(..) {
 504                     integrator.visit_basic_block_data(bb, &mut block);
 505                     caller_body.basic_blocks_mut().push(block);
 506                 }
 507
 508                 let terminator = Terminator {
 509                     source_info: callsite.location,
 510                     kind: TerminatorKind::Goto { target: BasicBlock::new(bb_len) }
 511                 };
 512
 513                 caller_body[callsite.bb].terminator = Some(terminator);
 514
 515                 true
 516             }
 517             kind => {
 518                 caller_body[callsite.bb].terminator = Some(Terminator {
 519                     source_info: terminator.source_info,
 520                     kind,
 521                 });
 522                 false
 523             }
 524         }
 525     }
 526
 527     fn make_call_args(
 528         &self,
 529         args: Vec<Operand<'tcx>>,
 530         callsite: &CallSite<'tcx>,
 531         caller_body: &mut Body<'tcx>,
 532     ) -> Vec<Local> {
 533         let tcx = self.tcx;
 534
 535         // There is a bit of a mismatch between the *caller* of a closure and the *callee*.
 536         // The caller provides the arguments wrapped up in a tuple:
 537         //
 538         //     tuple_tmp = (a, b, c)
 539         //     Fn::call(closure_ref, tuple_tmp)
 540         //
 541         // meanwhile the closure body expects the arguments (here, `a`, `b`, and `c`)
 542         // as distinct arguments. (This is the "rust-call" ABI hack.) Normally, codegen has
 543         // the job of unpacking this tuple. But here, we are codegen. =) So we want to create
 544         // a vector like
 545         //
 546         //     [closure_ref, tuple_tmp.0, tuple_tmp.1, tuple_tmp.2]
 547         //
 548         // Except for one tiny wrinkle: we don't actually want `tuple_tmp.0`. It's more convenient
 549         // if we "spill" that into *another* temporary, so that we can map the argument
 550         // variable in the callee MIR directly to an argument variable on our side.
 551         // So we introduce temporaries like:
 552         //
 553         //     tmp0 = tuple_tmp.0
 554         //     tmp1 = tuple_tmp.1
 555         //     tmp2 = tuple_tmp.2
 556         //
 557         // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
 558         if tcx.is_closure(callsite.callee) {
 559             let mut args = args.into_iter();
 560             let self_ = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
 561             let tuple = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
 562             assert!(args.next().is_none());
 563
 564             let tuple = Place::from(tuple);
 565             let tuple_tys = if let ty::Tuple(s) = tuple.ty(caller_body, tcx).ty.sty {
 566                 s
 567             } else {
 568                 bug!("Closure arguments are not passed as a tuple");
 569             };
 570
 571             // The `closure_ref` in our example above.
 572             let closure_ref_arg = iter::once(self_);
 573
 574             // The `tmp0`, `tmp1`, and `tmp2` in our example abonve.
 575             let tuple_tmp_args =
 576                 tuple_tys.iter().enumerate().map(|(i, ty)| {
 577                     // This is e.g., `tuple_tmp.0` in our example above.
 578                     let tuple_field = Operand::Move(tuple.clone().field(
 579                         Field::new(i),
 580                         ty.expect_ty(),
 581                     ));
 582
 583                     // Spill to a local to make e.g., `tmp0`.
 584                     self.create_temp_if_necessary(tuple_field, callsite, caller_body)
 585                 });
 586
 587             closure_ref_arg.chain(tuple_tmp_args).collect()
 588         } else {
 589             args.into_iter()
 590                 .map(|a| self.create_temp_if_necessary(a, callsite, caller_body))
 591                 .collect()
 592         }
 593     }
 594
 595     /// If `arg` is already a temporary, returns it. Otherwise, introduces a fresh
 596     /// temporary `T` and an instruction `T = arg`, and returns `T`.
 597     fn create_temp_if_necessary(
 598         &self,
 599         arg: Operand<'tcx>,
 600         callsite: &CallSite<'tcx>,
 601         caller_body: &mut Body<'tcx>,
 602     ) -> Local {
 603         // FIXME: Analysis of the usage of the arguments to avoid
 604         // unnecessary temporaries.
 605
 606         if let Operand::Move(Place {
 607             base: PlaceBase::Local(local),
 608             projection: None,
 609         }) = arg {
 610             if caller_body.local_kind(local) == LocalKind::Temp {
 611                 // Reuse the operand if it's a temporary already
 612                 return local;
 613             }
 614         }
 615
 616         debug!("creating temp for argument {:?}", arg);
 617         // Otherwise, create a temporary for the arg
 618         let arg = Rvalue::Use(arg);
 619
 620         let ty = arg.ty(caller_body, self.tcx);
 621
 622         let arg_tmp = LocalDecl::new_temp(ty, callsite.location.span);
 623         let arg_tmp = caller_body.local_decls.push(arg_tmp);
 624
 625         let stmt = Statement {
 626             source_info: callsite.location,
 627             kind: StatementKind::Assign(Place::from(arg_tmp), box arg),
 628         };
 629         caller_body[callsite.bb].statements.push(stmt);
 630         arg_tmp
 631     }
 632 }
 633
 634 fn type_size_of<'tcx>(
 635     tcx: TyCtxt<'tcx>,
 636     param_env: ty::ParamEnv<'tcx>,
 637     ty: Ty<'tcx>,
 638 ) -> Option<u64> {
 639     tcx.layout_of(param_env.and(ty)).ok().map(|layout| layout.size.bytes())
 640 }
 641
 642 /**
 643  * Integrator.
 644  *
 645  * Integrates blocks from the callee function into the calling function.
 646  * Updates block indices, references to locals and other control flow
 647  * stuff.
 648 */
 649 struct Integrator<'a, 'tcx> {
 650     block_idx: usize,
 651     args: &'a [Local],
 652     local_map: IndexVec<Local, Local>,
 653     scope_map: IndexVec<SourceScope, SourceScope>,
 654     promoted_map: IndexVec<Promoted, Promoted>,
 655     _callsite: CallSite<'tcx>,
 656     destination: Place<'tcx>,
 657     return_block: BasicBlock,
 658     cleanup_block: Option<BasicBlock>,
 659     in_cleanup_block: bool,
 660 }
 661
 662 impl<'a, 'tcx> Integrator<'a, 'tcx> {
 663     fn update_target(&self, tgt: BasicBlock) -> BasicBlock {
 664         let new = BasicBlock::new(tgt.index() + self.block_idx);
 665         debug!("updating target `{:?}`, new: `{:?}`", tgt, new);
 666         new
 667     }
 668 }
 669
 670 impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
 671     fn visit_local(&mut self,
 672                    local: &mut Local,
 673                    _ctxt: PlaceContext,
 674                    _location: Location) {
 675         if *local == RETURN_PLACE {
 676             match self.destination {
 677                 Place {
 678                     base: PlaceBase::Local(l),
 679                     projection: None,
 680                 } => {
 681                     *local = l;
 682                     return;
 683                 },
 684                 ref place => bug!("Return place is {:?}, not local", place)
 685             }
 686         }
 687         let idx = local.index() - 1;
 688         if idx < self.args.len() {
 689             *local = self.args[idx];
 690             return;
 691         }
 692         *local = self.local_map[Local::new(idx - self.args.len())];
 693     }
 694
 695     fn visit_place(&mut self,
 696                     place: &mut Place<'tcx>,
 697                     _ctxt: PlaceContext,
 698                     _location: Location) {
 699
 700         match place {
 701             Place {
 702                 base: PlaceBase::Local(RETURN_PLACE),
 703                 projection: None,
 704             } => {
 705                 // Return pointer; update the place itself
 706                 *place = self.destination.clone();
 707             },
 708             Place {
 709                 base: PlaceBase::Static(box Static {
 710                     kind: StaticKind::Promoted(promoted),
 711                     ..
 712                 }),
 713                 projection: None,
 714             } => {
 715                 if let Some(p) = self.promoted_map.get(*promoted).cloned() {
 716                     *promoted = p;
 717                 }
 718             },
 719             _ => self.super_place(place, _ctxt, _location)
 720         }
 721     }
 722
 723     fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
 724         self.in_cleanup_block = data.is_cleanup;
 725         self.super_basic_block_data(block, data);
 726         self.in_cleanup_block = false;
 727     }
 728
 729     fn visit_retag(
 730         &mut self,
 731         kind: &mut RetagKind,
 732         place: &mut Place<'tcx>,
 733         loc: Location,
 734     ) {
 735         self.super_retag(kind, place, loc);
 736
 737         // We have to patch all inlined retags to be aware that they are no longer
 738         // happening on function entry.
 739         if *kind == RetagKind::FnEntry {
 740             *kind = RetagKind::Default;
 741         }
 742     }
 743
 744     fn visit_terminator_kind(&mut self,
 745                              kind: &mut TerminatorKind<'tcx>, loc: Location) {
 746         self.super_terminator_kind(kind, loc);
 747
 748         match *kind {
 749             TerminatorKind::GeneratorDrop |
 750             TerminatorKind::Yield { .. } => bug!(),
 751             TerminatorKind::Goto { ref mut target} => {
 752                 *target = self.update_target(*target);
 753             }
 754             TerminatorKind::SwitchInt { ref mut targets, .. } => {
 755                 for tgt in targets {
 756                     *tgt = self.update_target(*tgt);
 757                 }
 758             }
 759             TerminatorKind::Drop { ref mut target, ref mut unwind, .. } |
 760             TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
 761                 *target = self.update_target(*target);
 762                 if let Some(tgt) = *unwind {
 763                     *unwind = Some(self.update_target(tgt));
 764                 } else if !self.in_cleanup_block {
 765                     // Unless this drop is in a cleanup block, add an unwind edge to
 766                     // the original call's cleanup block
 767                     *unwind = self.cleanup_block;
 768                 }
 769             }
 770             TerminatorKind::Call { ref mut destination, ref mut cleanup, .. } => {
 771                 if let Some((_, ref mut tgt)) = *destination {
 772                     *tgt = self.update_target(*tgt);
 773                 }
 774                 if let Some(tgt) = *cleanup {
 775                     *cleanup = Some(self.update_target(tgt));
 776                 } else if !self.in_cleanup_block {
 777                     // Unless this call is in a cleanup block, add an unwind edge to
 778                     // the original call's cleanup block
 779                     *cleanup = self.cleanup_block;
 780                 }
 781             }
 782             TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
 783                 *target = self.update_target(*target);
 784                 if let Some(tgt) = *cleanup {
 785                     *cleanup = Some(self.update_target(tgt));
 786                 } else if !self.in_cleanup_block {
 787                     // Unless this assert is in a cleanup block, add an unwind edge to
 788                     // the original call's cleanup block
 789                     *cleanup = self.cleanup_block;
 790                 }
 791             }
 792             TerminatorKind::Return => {
 793                 *kind = TerminatorKind::Goto { target: self.return_block };
 794             }
 795             TerminatorKind::Resume => {
 796                 if let Some(tgt) = self.cleanup_block {
 797                     *kind = TerminatorKind::Goto { target: tgt }
 798                 }
 799             }
 800             TerminatorKind::Abort => { }
 801             TerminatorKind::Unreachable => { }
 802             TerminatorKind::FalseEdges { ref mut real_target, ref mut imaginary_target } => {
 803                 *real_target = self.update_target(*real_target);
 804                 *imaginary_target = self.update_target(*imaginary_target);
 805             }
 806             TerminatorKind::FalseUnwind { real_target: _ , unwind: _ } =>
 807                 // see the ordering of passes in the optimized_mir query.
 808                 bug!("False unwinds should have been removed before inlining")
 809         }
 810     }
 811
 812     fn visit_source_scope(&mut self, scope: &mut SourceScope) {
 813         *scope = self.scope_map[*scope];
 814     }
 815 }