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