src/librustc_mir/transform/inline.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Inlining pass for MIR functions
  12
  13 use rustc::hir::def_id::DefId;
  14
  15 use rustc_data_structures::bitvec::BitVector;
  16 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
  17 use rustc_data_structures::graph;
  18
  19 use rustc::dep_graph::DepNode;
  20 use rustc::mir::*;
  21 use rustc::mir::transform::{MirCtxt, MirSource, Pass, PassId};
  22 use rustc::mir::visit::*;
  23 use rustc::traits;
  24 use rustc::ty::{self, Ty, TyCtxt};
  25 use rustc::ty::maps::Multi;
  26 use rustc::ty::steal::Steal;
  27 use rustc::ty::subst::{Subst,Substs};
  28 use rustc::util::nodemap::{DefIdSet};
  29
  30 use super::simplify::{remove_dead_blocks, CfgSimplifier};
  31
  32 use syntax::{attr};
  33 use syntax::abi::Abi;
  34
  35 use callgraph;
  36 use transform::interprocedural::InterproceduralCx;
  37
  38 const DEFAULT_THRESHOLD: usize = 50;
  39 const HINT_THRESHOLD: usize = 100;
  40
  41 const INSTR_COST: usize = 5;
  42 const CALL_PENALTY: usize = 25;
  43
  44 const UNKNOWN_SIZE_COST: usize = 10;
  45
  46 pub struct Inline;
  47
  48 impl Pass for Inline {
  49     fn run_pass<'a, 'tcx: 'a>(&self, mir_cx: &MirCtxt<'a, 'tcx>)
  50                               -> Multi<PassId, &'tcx Steal<Mir<'tcx>>> {
  51         let tcx = mir_cx.tcx();
  52         if tcx.sess.opts.debugging_opts.mir_opt_level < 2 {
  53             return Multi::from(tcx.alloc_steal_mir(mir_cx.steal_previous_mir()));
  54         }
  55
  56         let mut cx = InterproceduralCx::new(mir_cx);
  57
  58         let callgraph = callgraph::CallGraph::build(&mut cx);
  59
  60         let mut inliner = Inliner { tcx };
  61
  62         for scc in callgraph.scc_iter() {
  63             inliner.inline_scc(&mut cx, &callgraph, &scc);
  64         }
  65
  66         Multi::from(cx.into_local_mirs())
  67     }
  68 }
  69
  70 struct Inliner<'mir, 'tcx: 'mir> {
  71     tcx: TyCtxt<'mir, 'tcx, 'tcx>,
  72 }
  73
  74 #[derive(Copy, Clone)]
  75 struct CallSite<'tcx> {
  76     caller: DefId,
  77     callee: DefId,
  78     substs: &'tcx Substs<'tcx>,
  79     bb: BasicBlock,
  80     location: SourceInfo,
  81 }
  82
  83 impl<'mir, 'tcx> Inliner<'mir, 'tcx> {
  84     fn inline_scc<'a>(&mut self,
  85                       cx: &mut InterproceduralCx<'a, 'mir, 'tcx>,
  86                       callgraph: &callgraph::CallGraph,
  87                       scc: &[graph::NodeIndex]) -> bool {
  88         let tcx = self.tcx;
  89         let mut callsites = Vec::new();
  90         let mut in_scc = DefIdSet();
  91
  92         let mut inlined_into = DefIdSet();
  93
  94         for &node in scc {
  95             let def_id = callgraph.def_id(node);
  96
  97             // Don't inspect functions from other crates
  98             let id = if let Some(id) = tcx.hir.as_local_node_id(def_id) {
  99                 id
 100             } else {
 101                 continue;
 102             };
 103             let src = MirSource::from_node(tcx, id);
 104             if let MirSource::Fn(_) = src {
 105                 if let Some(mir) = cx.ensure_mir_and_read(def_id) {
 106                     for (bb, bb_data) in mir.basic_blocks().iter_enumerated() {
 107                         // Don't inline calls that are in cleanup blocks.
 108                         if bb_data.is_cleanup { continue; }
 109
 110                         // Only consider direct calls to functions
 111                         let terminator = bb_data.terminator();
 112                         if let TerminatorKind::Call {
 113                             func: Operand::Constant(ref f), .. } = terminator.kind {
 114                             if let ty::TyFnDef(callee_def_id, substs, _) = f.ty.sty {
 115                                 callsites.push(CallSite {
 116                                     caller: def_id,
 117                                     callee: callee_def_id,
 118                                     substs: substs,
 119                                     bb: bb,
 120                                     location: terminator.source_info
 121                                 });
 122                             }
 123                         }
 124                     }
 125
 126                     in_scc.insert(def_id);
 127                 }
 128             }
 129         }
 130
 131         // Move callsites that are in the the SCC to the end so
 132         // they're inlined after calls to outside the SCC
 133         let mut first_call_in_scc = callsites.len();
 134
 135         let mut i = 0;
 136         while i < first_call_in_scc {
 137             let f = callsites[i].caller;
 138             if in_scc.contains(&f) {
 139                 first_call_in_scc -= 1;
 140                 callsites.swap(i, first_call_in_scc);
 141             } else {
 142                 i += 1;
 143             }
 144         }
 145
 146         let mut local_change;
 147         let mut changed = false;
 148
 149         loop {
 150             local_change = false;
 151             let mut csi = 0;
 152             while csi < callsites.len() {
 153                 let callsite = callsites[csi];
 154                 csi += 1;
 155
 156                 let _task = tcx.dep_graph.in_task(DepNode::Mir(callsite.caller));
 157                 tcx.dep_graph.write(DepNode::Mir(callsite.caller));
 158
 159                 let callee_mir = {
 160                     if let Some(callee_mir) = cx.ensure_mir_and_read(callsite.callee) {
 161                         if !self.should_inline(callsite, &callee_mir) {
 162                             continue;
 163                         }
 164
 165                         callee_mir.subst(tcx, callsite.substs)
 166                     } else {
 167                         continue;
 168                     }
 169
 170                 };
 171
 172                 let caller_mir = cx.mir_mut(callsite.caller);
 173
 174                 let start = caller_mir.basic_blocks().len();
 175
 176                 if !self.inline_call(callsite, caller_mir, callee_mir) {
 177                     continue;
 178                 }
 179
 180                 inlined_into.insert(callsite.caller);
 181
 182                 // Add callsites from inlined function
 183                 for (bb, bb_data) in caller_mir.basic_blocks().iter_enumerated().skip(start) {
 184                     // Only consider direct calls to functions
 185                     let terminator = bb_data.terminator();
 186                     if let TerminatorKind::Call {
 187                         func: Operand::Constant(ref f), .. } = terminator.kind {
 188                         if let ty::TyFnDef(callee_def_id, substs, _) = f.ty.sty {
 189                             // Don't inline the same function multiple times.
 190                             if callsite.callee != callee_def_id {
 191                                 callsites.push(CallSite {
 192                                     caller: callsite.caller,
 193                                     callee: callee_def_id,
 194                                     substs: substs,
 195                                     bb: bb,
 196                                     location: terminator.source_info
 197                                 });
 198                             }
 199                         }
 200                     }
 201                 }
 202
 203                 csi -= 1;
 204                 if scc.len() == 1 {
 205                     callsites.swap_remove(csi);
 206                 } else {
 207                     callsites.remove(csi);
 208                 }
 209
 210                 local_change = true;
 211                 changed = true;
 212             }
 213
 214             if !local_change {
 215                 break;
 216             }
 217         }
 218
 219         // Simplify functions we inlined into.
 220         for def_id in inlined_into {
 221             let _task = tcx.dep_graph.in_task(DepNode::Mir(def_id));
 222             tcx.dep_graph.write(DepNode::Mir(def_id));
 223
 224             let caller_mir = cx.mir_mut(def_id);
 225
 226             debug!("Running simplify cfg on {:?}", def_id);
 227             CfgSimplifier::new(caller_mir).simplify();
 228             remove_dead_blocks(caller_mir);
 229         }
 230         changed
 231     }
 232
 233     fn should_inline(&self,
 234                      callsite: CallSite<'tcx>,
 235                      callee_mir: &Mir<'tcx>)
 236                      -> bool
 237     {
 238         let tcx = self.tcx;
 239
 240         // Don't inline closures that have captures
 241         // FIXME: Handle closures better
 242         if callee_mir.upvar_decls.len() > 0 {
 243             return false;
 244         }
 245
 246
 247         let attrs = tcx.get_attrs(callsite.callee);
 248         let hint = attr::find_inline_attr(None, &attrs[..]);
 249
 250         let hinted = match hint {
 251             // Just treat inline(always) as a hint for now,
 252             // there are cases that prevent inlining that we
 253             // need to check for first.
 254             attr::InlineAttr::Always => true,
 255             attr::InlineAttr::Never => return false,
 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.types().count() == 0 && !hinted {
 265                 return false;
 266             }
 267         }
 268
 269         let mut threshold = if hinted {
 270             HINT_THRESHOLD
 271         } else {
 272             DEFAULT_THRESHOLD
 273         };
 274
 275         // Significantly lower the threshold for inlining cold functions
 276         if attr::contains_name(&attrs[..], "cold") {
 277             threshold /= 5;
 278         }
 279
 280         // Give a bonus functions with a small number of blocks,
 281         // We normally have two or three blocks for even
 282         // very small functions.
 283         if callee_mir.basic_blocks().len() <= 3 {
 284             threshold += threshold / 4;
 285         }
 286
 287         // FIXME: Give a bonus to functions with only a single caller
 288
 289         let id = tcx.hir.as_local_node_id(callsite.caller).expect("Caller not local");
 290         let param_env = ty::ParameterEnvironment::for_item(tcx, id);
 291
 292         let mut first_block = true;
 293         let mut cost = 0;
 294
 295         // Traverse the MIR manually so we can account for the effects of
 296         // inlining on the CFG.
 297         let mut work_list = vec![START_BLOCK];
 298         let mut visited = BitVector::new(callee_mir.basic_blocks().len());
 299         while let Some(bb) = work_list.pop() {
 300             if !visited.insert(bb.index()) { continue; }
 301             let blk = &callee_mir.basic_blocks()[bb];
 302
 303             for stmt in &blk.statements {
 304                 // Don't count StorageLive/StorageDead in the inlining cost.
 305                 match stmt.kind {
 306                     StatementKind::StorageLive(_) |
 307                     StatementKind::StorageDead(_) |
 308                     StatementKind::Nop => {}
 309                     _ => cost += INSTR_COST
 310                 }
 311             }
 312             let term = blk.terminator();
 313             let mut is_drop = false;
 314             match term.kind {
 315                 TerminatorKind::Drop { ref location, target, unwind } |
 316                 TerminatorKind::DropAndReplace { ref location, target, unwind, .. } => {
 317                     is_drop = true;
 318                     work_list.push(target);
 319                     // If the location doesn't actually need dropping, treat it like
 320                     // a regular goto.
 321                     let ty = location.ty(&callee_mir, tcx).subst(tcx, callsite.substs);
 322                     let ty = ty.to_ty(tcx);
 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::TyFnDef(.., f) = f.ty.sty {
 342                         // Don't give intrinsics the extra penalty for calls
 343                         if f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic {
 344                             cost += INSTR_COST;
 345                         } else {
 346                             cost += CALL_PENALTY;
 347                         }
 348                     }
 349                 }
 350                 TerminatorKind::Assert { .. } => cost += CALL_PENALTY,
 351                 _ => cost += INSTR_COST
 352             }
 353
 354             if !is_drop {
 355                 for &succ in &term.successors()[..] {
 356                     work_list.push(succ);
 357                 }
 358             }
 359
 360             first_block = false;
 361         }
 362
 363         // Count up the cost of local variables and temps, if we know the size
 364         // use that, otherwise we use a moderately-large dummy cost.
 365
 366         let ptr_size = tcx.data_layout.pointer_size.bytes();
 367
 368         for v in callee_mir.vars_and_temps_iter() {
 369             let v = &callee_mir.local_decls[v];
 370             let ty = v.ty.subst(tcx, callsite.substs);
 371             // Cost of the var is the size in machine-words, if we know
 372             // it.
 373             if let Some(size) = type_size_of(tcx, param_env.clone(), ty) {
 374                 cost += (size / ptr_size) as usize;
 375             } else {
 376                 cost += UNKNOWN_SIZE_COST;
 377             }
 378         }
 379
 380         debug!("Inline cost for {:?} is {}", callsite.callee, cost);
 381
 382         if let attr::InlineAttr::Always = hint {
 383             true
 384         } else {
 385             cost <= threshold
 386         }
 387     }
 388
 389     fn inline_call(&self,
 390                    callsite: CallSite<'tcx>,
 391                    caller_mir: &mut Mir<'tcx>,
 392                    mut callee_mir: Mir<'tcx>) -> bool {
 393         // Don't inline a function into itself
 394         if callsite.caller == callsite.callee { return false; }
 395
 396         let _task = self.tcx.dep_graph.in_task(DepNode::Mir(callsite.caller));
 397
 398
 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
 404                 debug!("Inlined {:?} into {:?}", callsite.callee, callsite.caller);
 405
 406                 let is_box_free = Some(callsite.callee) == self.tcx.lang_items.box_free_fn();
 407
 408                 let mut local_map = IndexVec::with_capacity(callee_mir.local_decls.len());
 409                 let mut scope_map = IndexVec::with_capacity(callee_mir.visibility_scopes.len());
 410                 let mut promoted_map = IndexVec::with_capacity(callee_mir.promoted.len());
 411
 412                 for mut scope in callee_mir.visibility_scopes.iter().cloned() {
 413                     if scope.parent_scope.is_none() {
 414                         scope.parent_scope = Some(callsite.location.scope);
 415                         scope.span = callee_mir.span;
 416                     }
 417
 418                     scope.span = callsite.location.span;
 419
 420                     let idx = caller_mir.visibility_scopes.push(scope);
 421                     scope_map.push(idx);
 422                 }
 423
 424                 for loc in callee_mir.vars_and_temps_iter() {
 425                     let mut local = callee_mir.local_decls[loc].clone();
 426
 427                     local.source_info.scope = scope_map[local.source_info.scope];
 428                     local.source_info.span = callsite.location.span;
 429
 430                     let idx = caller_mir.local_decls.push(local);
 431                     local_map.push(idx);
 432                 }
 433
 434                 for p in callee_mir.promoted.iter().cloned() {
 435                     let idx = caller_mir.promoted.push(p);
 436                     promoted_map.push(idx);
 437                 }
 438
 439                 // If the call is something like `a[*i] = f(i)`, where
 440                 // `i : &mut usize`, then just duplicating the `a[*i]`
 441                 // Lvalue could result in two different locations if `f`
 442                 // writes to `i`. To prevent this we need to create a temporary
 443                 // borrow of the lvalue and pass the destination as `*temp` instead.
 444                 fn dest_needs_borrow(lval: &Lvalue) -> bool {
 445                     match *lval {
 446                         Lvalue::Projection(ref p) => {
 447                             match p.elem {
 448                                 ProjectionElem::Deref |
 449                                 ProjectionElem::Index(_) => true,
 450                                 _ => dest_needs_borrow(&p.base)
 451                             }
 452                         }
 453                         // Static variables need a borrow because the callee
 454                         // might modify the same static.
 455                         Lvalue::Static(_) => true,
 456                         _ => false
 457                     }
 458                 }
 459
 460                 let dest = if dest_needs_borrow(&destination.0) {
 461                     debug!("Creating temp for return destination");
 462                     let dest = Rvalue::Ref(
 463                         self.tcx.types.re_erased,
 464                         BorrowKind::Mut,
 465                         destination.0);
 466
 467                     let ty = dest.ty(caller_mir, self.tcx);
 468
 469                     let temp = LocalDecl::new_temp(ty, callsite.location.span);
 470
 471                     let tmp = caller_mir.local_decls.push(temp);
 472                     let tmp = Lvalue::Local(tmp);
 473
 474                     let stmt = Statement {
 475                         source_info: callsite.location,
 476                         kind: StatementKind::Assign(tmp.clone(), dest)
 477                     };
 478                     caller_mir[callsite.bb]
 479                         .statements.push(stmt);
 480                     tmp.deref()
 481                 } else {
 482                     destination.0
 483                 };
 484
 485                 let return_block = destination.1;
 486
 487                 let args : Vec<_> = if is_box_free {
 488                     assert!(args.len() == 1);
 489                     // box_free takes a Box, but is defined with a *mut T, inlining
 490                     // needs to generate the cast.
 491                     // FIXME: we should probably just generate correct MIR in the first place...
 492
 493                     let arg = if let Operand::Consume(ref lval) = args[0] {
 494                         lval.clone()
 495                     } else {
 496                         bug!("Constant arg to \"box_free\"");
 497                     };
 498
 499                     let ptr_ty = args[0].ty(caller_mir, self.tcx);
 500                     vec![self.cast_box_free_arg(arg, ptr_ty, &callsite, caller_mir)]
 501                 } else {
 502                     // Copy the arguments if needed.
 503                     self.make_call_args(args, &callsite, caller_mir)
 504                 };
 505
 506                 let bb_len = caller_mir.basic_blocks().len();
 507                 let mut integrator = Integrator {
 508                     block_idx: bb_len,
 509                     args: &args,
 510                     local_map: local_map,
 511                     scope_map: scope_map,
 512                     promoted_map: promoted_map,
 513                     _callsite: callsite,
 514                     destination: dest,
 515                     return_block: return_block,
 516                     cleanup_block: cleanup,
 517                     in_cleanup_block: false
 518                 };
 519
 520
 521                 for (bb, mut block) in callee_mir.basic_blocks_mut().drain_enumerated(..) {
 522                     integrator.visit_basic_block_data(bb, &mut block);
 523                     caller_mir.basic_blocks_mut().push(block);
 524                 }
 525
 526                 let terminator = Terminator {
 527                     source_info: callsite.location,
 528                     kind: TerminatorKind::Goto { target: BasicBlock::new(bb_len) }
 529                 };
 530
 531                 caller_mir[callsite.bb].terminator = Some(terminator);
 532
 533                 true
 534             }
 535             kind => {
 536                 caller_mir[callsite.bb].terminator = Some(Terminator {
 537                     source_info: terminator.source_info,
 538                     kind: kind
 539                 });
 540                 false
 541             }
 542         }
 543     }
 544
 545     fn cast_box_free_arg(&self, arg: Lvalue<'tcx>, ptr_ty: Ty<'tcx>,
 546                          callsite: &CallSite<'tcx>, caller_mir: &mut Mir<'tcx>) -> Operand<'tcx> {
 547         let arg = Rvalue::Ref(
 548             self.tcx.types.re_erased,
 549             BorrowKind::Mut,
 550             arg.deref());
 551
 552         let ty = arg.ty(caller_mir, self.tcx);
 553         let ref_tmp = LocalDecl::new_temp(ty, callsite.location.span);
 554         let ref_tmp = caller_mir.local_decls.push(ref_tmp);
 555         let ref_tmp = Lvalue::Local(ref_tmp);
 556
 557         let ref_stmt = Statement {
 558             source_info: callsite.location,
 559             kind: StatementKind::Assign(ref_tmp.clone(), arg)
 560         };
 561
 562         caller_mir[callsite.bb]
 563             .statements.push(ref_stmt);
 564
 565         let pointee_ty = match ptr_ty.sty {
 566             ty::TyRawPtr(tm) | ty::TyRef(_, tm) => tm.ty,
 567             _ if ptr_ty.is_box() => ptr_ty.boxed_ty(),
 568             _ => bug!("Invalid type `{:?}` for call to box_free", ptr_ty)
 569         };
 570         let ptr_ty = self.tcx.mk_mut_ptr(pointee_ty);
 571
 572         let raw_ptr = Rvalue::Cast(CastKind::Misc, Operand::Consume(ref_tmp), ptr_ty);
 573
 574         let cast_tmp = LocalDecl::new_temp(ptr_ty, callsite.location.span);
 575         let cast_tmp = caller_mir.local_decls.push(cast_tmp);
 576         let cast_tmp = Lvalue::Local(cast_tmp);
 577
 578         let cast_stmt = Statement {
 579             source_info: callsite.location,
 580             kind: StatementKind::Assign(cast_tmp.clone(), raw_ptr)
 581         };
 582
 583         caller_mir[callsite.bb]
 584             .statements.push(cast_stmt);
 585
 586         Operand::Consume(cast_tmp)
 587     }
 588
 589     fn make_call_args(&self, args: Vec<Operand<'tcx>>,
 590                       callsite: &CallSite<'tcx>, caller_mir: &mut Mir<'tcx>) -> Vec<Operand<'tcx>> {
 591         let tcx = self.tcx;
 592         // FIXME: Analysis of the usage of the arguments to avoid
 593         // unnecessary temporaries.
 594         args.into_iter().map(|a| {
 595             if let Operand::Consume(Lvalue::Local(local)) = a {
 596                 if caller_mir.local_kind(local) == LocalKind::Temp {
 597                     // Reuse the operand if it's a temporary already
 598                     return a;
 599                 }
 600             }
 601
 602             debug!("Creating temp for argument");
 603             // Otherwise, create a temporary for the arg
 604             let arg = Rvalue::Use(a);
 605
 606             let ty = arg.ty(caller_mir, tcx);
 607
 608             let arg_tmp = LocalDecl::new_temp(ty, callsite.location.span);
 609             let arg_tmp = caller_mir.local_decls.push(arg_tmp);
 610             let arg_tmp = Lvalue::Local(arg_tmp);
 611
 612             let stmt = Statement {
 613                 source_info: callsite.location,
 614                 kind: StatementKind::Assign(arg_tmp.clone(), arg)
 615             };
 616             caller_mir[callsite.bb].statements.push(stmt);
 617             Operand::Consume(arg_tmp)
 618         }).collect()
 619     }
 620 }
 621
 622 fn type_size_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, param_env: ty::ParameterEnvironment<'tcx>,
 623                           ty: Ty<'tcx>) -> Option<u64> {
 624     tcx.infer_ctxt(param_env, traits::Reveal::All).enter(|infcx| {
 625         ty.layout(&infcx).ok().map(|layout| {
 626             layout.size(&tcx.data_layout).bytes()
 627         })
 628     })
 629 }
 630
 631 /**
 632  * Integrator.
 633  *
 634  * Integrates blocks from the callee function into the calling function.
 635  * Updates block indices, references to locals and other control flow
 636  * stuff.
 637  */
 638 struct Integrator<'a, 'tcx: 'a> {
 639     block_idx: usize,
 640     args: &'a [Operand<'tcx>],
 641     local_map: IndexVec<Local, Local>,
 642     scope_map: IndexVec<VisibilityScope, VisibilityScope>,
 643     promoted_map: IndexVec<Promoted, Promoted>,
 644     _callsite: CallSite<'tcx>,
 645     destination: Lvalue<'tcx>,
 646     return_block: BasicBlock,
 647     cleanup_block: Option<BasicBlock>,
 648     in_cleanup_block: bool,
 649 }
 650
 651 impl<'a, 'tcx> Integrator<'a, 'tcx> {
 652     fn update_target(&self, tgt: BasicBlock) -> BasicBlock {
 653         let new = BasicBlock::new(tgt.index() + self.block_idx);
 654         debug!("Updating target `{:?}`, new: `{:?}`", tgt, new);
 655         new
 656     }
 657
 658     fn update_local(&self, local: Local) -> Option<Local> {
 659         let idx = local.index();
 660         if idx < (self.args.len() + 1) {
 661             return None;
 662         }
 663         let idx = idx - (self.args.len() + 1);
 664         let local = Local::new(idx);
 665         self.local_map.get(local).cloned()
 666     }
 667
 668     fn arg_index(&self, arg: Local) -> Option<usize> {
 669         let idx = arg.index();
 670         if idx > 0 && idx <= self.args.len() {
 671             Some(idx - 1)
 672         } else {
 673             None
 674         }
 675     }
 676 }
 677
 678 impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
 679     fn visit_lvalue(&mut self,
 680                     lvalue: &mut Lvalue<'tcx>,
 681                     _ctxt: LvalueContext<'tcx>,
 682                     _location: Location) {
 683         if let Lvalue::Local(ref mut local) = *lvalue {
 684             if let Some(l) = self.update_local(*local) {
 685                 // Temp or Var; update the local reference
 686                 *local = l;
 687                 return;
 688             }
 689         }
 690         if let Lvalue::Local(local) = *lvalue {
 691             if local == RETURN_POINTER {
 692                 // Return pointer; update the lvalue itself
 693                 *lvalue = self.destination.clone();
 694             } else if local.index() < (self.args.len() + 1) {
 695                 // Argument, once again update the the lvalue itself
 696                 let idx = local.index() - 1;
 697                 if let Operand::Consume(ref lval) = self.args[idx] {
 698                     *lvalue = lval.clone();
 699                 } else {
 700                     bug!("Arg operand `{:?}` is not an Lvalue use.", idx)
 701                 }
 702             }
 703         } else {
 704             self.super_lvalue(lvalue, _ctxt, _location)
 705         }
 706     }
 707
 708     fn visit_operand(&mut self, operand: &mut Operand<'tcx>, location: Location) {
 709         if let Operand::Consume(Lvalue::Local(arg)) = *operand {
 710             if let Some(idx) = self.arg_index(arg) {
 711                 let new_arg = self.args[idx].clone();
 712                 *operand = new_arg;
 713                 return;
 714             }
 715         }
 716         self.super_operand(operand, location);
 717     }
 718
 719     fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
 720         self.in_cleanup_block = data.is_cleanup;
 721         self.super_basic_block_data(block, data);
 722         self.in_cleanup_block = false;
 723     }
 724
 725     fn visit_terminator_kind(&mut self, block: BasicBlock,
 726                              kind: &mut TerminatorKind<'tcx>, loc: Location) {
 727         self.super_terminator_kind(block, kind, loc);
 728
 729         match *kind {
 730             TerminatorKind::Goto { ref mut target} => {
 731                 *target = self.update_target(*target);
 732             }
 733             TerminatorKind::SwitchInt { ref mut targets, .. } => {
 734                 for tgt in targets {
 735                     *tgt = self.update_target(*tgt);
 736                 }
 737             }
 738             TerminatorKind::Drop { ref mut target, ref mut unwind, .. } |
 739             TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
 740                 *target = self.update_target(*target);
 741                 if let Some(tgt) = *unwind {
 742                     *unwind = Some(self.update_target(tgt));
 743                 } else if !self.in_cleanup_block {
 744                     // Unless this drop is in a cleanup block, add an unwind edge to
 745                     // the orignal call's cleanup block
 746                     *unwind = self.cleanup_block;
 747                 }
 748             }
 749             TerminatorKind::Call { ref mut destination, ref mut cleanup, .. } => {
 750                 if let Some((_, ref mut tgt)) = *destination {
 751                     *tgt = self.update_target(*tgt);
 752                 }
 753                 if let Some(tgt) = *cleanup {
 754                     *cleanup = Some(self.update_target(tgt));
 755                 } else if !self.in_cleanup_block {
 756                     // Unless this call is in a cleanup block, add an unwind edge to
 757                     // the orignal call's cleanup block
 758                     *cleanup = self.cleanup_block;
 759                 }
 760             }
 761             TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
 762                 *target = self.update_target(*target);
 763                 if let Some(tgt) = *cleanup {
 764                     *cleanup = Some(self.update_target(tgt));
 765                 } else if !self.in_cleanup_block {
 766                     // Unless this assert is in a cleanup block, add an unwind edge to
 767                     // the orignal call's cleanup block
 768                     *cleanup = self.cleanup_block;
 769                 }
 770             }
 771             TerminatorKind::Return => {
 772                 *kind = TerminatorKind::Goto { target: self.return_block };
 773             }
 774             TerminatorKind::Resume => {
 775                 if let Some(tgt) = self.cleanup_block {
 776                     *kind = TerminatorKind::Goto { target: tgt }
 777                 }
 778             }
 779             TerminatorKind::Unreachable => { }
 780         }
 781     }
 782
 783     fn visit_visibility_scope(&mut self, scope: &mut VisibilityScope) {
 784         *scope = self.scope_map[*scope];
 785     }
 786
 787     fn visit_literal(&mut self, literal: &mut Literal<'tcx>, loc: Location) {
 788         if let Literal::Promoted { ref mut index } = *literal {
 789             if let Some(p) = self.promoted_map.get(*index).cloned() {
 790                 *index = p;
 791             }
 792         } else {
 793             self.super_literal(literal, loc);
 794         }
 795     }
 796 }