compiler/rustc_mir/src/transform/inline.rs

   1 //! Inlining pass for MIR functions
   2
   3 use rustc_attr as attr;
   4 use rustc_hir::def_id::DefId;
   5 use rustc_index::bit_set::BitSet;
   6 use rustc_index::vec::{Idx, IndexVec};
   7 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
   8 use rustc_middle::mir::visit::*;
   9 use rustc_middle::mir::*;
  10 use rustc_middle::ty::subst::{Subst, SubstsRef};
  11 use rustc_middle::ty::{self, ConstKind, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
  12 use rustc_target::spec::abi::Abi;
  13
  14 use super::simplify::{remove_dead_blocks, CfgSimplifier};
  15 use crate::transform::{MirPass, MirSource};
  16 use std::collections::VecDeque;
  17 use std::iter;
  18
  19 const DEFAULT_THRESHOLD: usize = 50;
  20 const HINT_THRESHOLD: usize = 100;
  21
  22 const INSTR_COST: usize = 5;
  23 const CALL_PENALTY: usize = 25;
  24 const LANDINGPAD_PENALTY: usize = 50;
  25 const RESUME_PENALTY: usize = 45;
  26
  27 const UNKNOWN_SIZE_COST: usize = 10;
  28
  29 pub struct Inline;
  30
  31 #[derive(Copy, Clone, Debug)]
  32 struct CallSite<'tcx> {
  33     callee: DefId,
  34     substs: SubstsRef<'tcx>,
  35     bb: BasicBlock,
  36     location: SourceInfo,
  37 }
  38
  39 impl<'tcx> MirPass<'tcx> for Inline {
  40     fn run_pass(&self, tcx: TyCtxt<'tcx>, source: MirSource<'tcx>, body: &mut Body<'tcx>) {
  41         if tcx.sess.opts.debugging_opts.mir_opt_level >= 2 {
  42             if tcx.sess.opts.debugging_opts.instrument_coverage {
  43                 // The current implementation of source code coverage injects code region counters
  44                 // into the MIR, and assumes a 1-to-1 correspondence between MIR and source-code-
  45                 // based function.
  46                 debug!("function inlining is disabled when compiling with `instrument_coverage`");
  47             } else {
  48                 Inliner { tcx, source, codegen_fn_attrs: tcx.codegen_fn_attrs(source.def_id()) }
  49                     .run_pass(body);
  50             }
  51         }
  52     }
  53 }
  54
  55 struct Inliner<'tcx> {
  56     tcx: TyCtxt<'tcx>,
  57     source: MirSource<'tcx>,
  58     codegen_fn_attrs: &'tcx CodegenFnAttrs,
  59 }
  60
  61 impl Inliner<'tcx> {
  62     fn run_pass(&self, caller_body: &mut Body<'tcx>) {
  63         // Keep a queue of callsites to try inlining on. We take
  64         // advantage of the fact that queries detect cycles here to
  65         // allow us to try and fetch the fully optimized MIR of a
  66         // call; if it succeeds, we can inline it and we know that
  67         // they do not call us.  Otherwise, we just don't try to
  68         // inline.
  69         //
  70         // We use a queue so that we inline "broadly" before we inline
  71         // in depth. It is unclear if this is the best heuristic,
  72         // really, but that's true of all the heuristics in this
  73         // file. =)
  74
  75         let mut callsites = VecDeque::new();
  76
  77         let param_env = self.tcx.param_env_reveal_all_normalized(self.source.def_id());
  78
  79         // Only do inlining into fn bodies.
  80         let id = self.tcx.hir().local_def_id_to_hir_id(self.source.def_id().expect_local());
  81         if self.tcx.hir().body_owner_kind(id).is_fn_or_closure() && self.source.promoted.is_none() {
  82             for (bb, bb_data) in caller_body.basic_blocks().iter_enumerated() {
  83                 if let Some(callsite) =
  84                     self.get_valid_function_call(bb, bb_data, caller_body, param_env)
  85                 {
  86                     callsites.push_back(callsite);
  87                 }
  88             }
  89         } else {
  90             return;
  91         }
  92
  93         let mut local_change;
  94         let mut changed = false;
  95
  96         loop {
  97             local_change = false;
  98             while let Some(callsite) = callsites.pop_front() {
  99                 debug!("checking whether to inline callsite {:?}", callsite);
 100                 if !self.tcx.is_mir_available(callsite.callee) {
 101                     debug!("checking whether to inline callsite {:?} - MIR unavailable", callsite);
 102                     continue;
 103                 }
 104
 105                 let callee_body = if let Some(callee_def_id) = callsite.callee.as_local() {
 106                     let callee_hir_id = self.tcx.hir().local_def_id_to_hir_id(callee_def_id);
 107                     let self_hir_id =
 108                         self.tcx.hir().local_def_id_to_hir_id(self.source.def_id().expect_local());
 109                     // Avoid a cycle here by only using `optimized_mir` only if we have
 110                     // a lower `HirId` than the callee. This ensures that the callee will
 111                     // not inline us. This trick only works without incremental compilation.
 112                     // So don't do it if that is enabled. Also avoid inlining into generators,
 113                     // since their `optimized_mir` is used for layout computation, which can
 114                     // create a cycle, even when no attempt is made to inline the function
 115                     // in the other direction.
 116                     if !self.tcx.dep_graph.is_fully_enabled()
 117                         && self_hir_id < callee_hir_id
 118                         && caller_body.generator_kind.is_none()
 119                     {
 120                         self.tcx.optimized_mir(callsite.callee)
 121                     } else {
 122                         continue;
 123                     }
 124                 } else {
 125                     // This cannot result in a cycle since the callee MIR is from another crate
 126                     // and is already optimized.
 127                     self.tcx.optimized_mir(callsite.callee)
 128                 };
 129
 130                 let callee_body = if self.consider_optimizing(callsite, callee_body) {
 131                     self.tcx.subst_and_normalize_erasing_regions(
 132                         &callsite.substs,
 133                         param_env,
 134                         callee_body,
 135                     )
 136                 } else {
 137                     continue;
 138                 };
 139
 140                 // Copy only unevaluated constants from the callee_body into the caller_body.
 141                 // Although we are only pushing `ConstKind::Unevaluated` consts to
 142                 // `required_consts`, here we may not only have `ConstKind::Unevaluated`
 143                 // because we are calling `subst_and_normalize_erasing_regions`.
 144                 caller_body.required_consts.extend(
 145                     callee_body.required_consts.iter().copied().filter(|&constant| {
 146                         matches!(constant.literal.val, ConstKind::Unevaluated(_, _, _))
 147                     }),
 148                 );
 149
 150                 let start = caller_body.basic_blocks().len();
 151                 debug!("attempting to inline callsite {:?} - body={:?}", callsite, callee_body);
 152                 if !self.inline_call(callsite, caller_body, callee_body) {
 153                     debug!("attempting to inline callsite {:?} - failure", callsite);
 154                     continue;
 155                 }
 156                 debug!("attempting to inline callsite {:?} - success", callsite);
 157
 158                 // Add callsites from inlined function
 159                 for (bb, bb_data) in caller_body.basic_blocks().iter_enumerated().skip(start) {
 160                     if let Some(new_callsite) =
 161                         self.get_valid_function_call(bb, bb_data, caller_body, param_env)
 162                     {
 163                         // Don't inline the same function multiple times.
 164                         if callsite.callee != new_callsite.callee {
 165                             callsites.push_back(new_callsite);
 166                         }
 167                     }
 168                 }
 169
 170                 local_change = true;
 171                 changed = true;
 172             }
 173
 174             if !local_change {
 175                 break;
 176             }
 177         }
 178
 179         // Simplify if we inlined anything.
 180         if changed {
 181             debug!("running simplify cfg on {:?}", self.source);
 182             CfgSimplifier::new(caller_body).simplify();
 183             remove_dead_blocks(caller_body);
 184         }
 185     }
 186
 187     fn get_valid_function_call(
 188         &self,
 189         bb: BasicBlock,
 190         bb_data: &BasicBlockData<'tcx>,
 191         caller_body: &Body<'tcx>,
 192         param_env: ParamEnv<'tcx>,
 193     ) -> Option<CallSite<'tcx>> {
 194         // Don't inline calls that are in cleanup blocks.
 195         if bb_data.is_cleanup {
 196             return None;
 197         }
 198
 199         // Only consider direct calls to functions
 200         let terminator = bb_data.terminator();
 201         if let TerminatorKind::Call { func: ref op, .. } = terminator.kind {
 202             if let ty::FnDef(callee_def_id, substs) = *op.ty(caller_body, self.tcx).kind() {
 203                 let instance =
 204                     Instance::resolve(self.tcx, param_env, callee_def_id, substs).ok().flatten()?;
 205
 206                 if let InstanceDef::Virtual(..) = instance.def {
 207                     return None;
 208                 }
 209
 210                 return Some(CallSite {
 211                     callee: instance.def_id(),
 212                     substs: instance.substs,
 213                     bb,
 214                     location: terminator.source_info,
 215                 });
 216             }
 217         }
 218
 219         None
 220     }
 221
 222     fn consider_optimizing(&self, callsite: CallSite<'tcx>, callee_body: &Body<'tcx>) -> bool {
 223         debug!("consider_optimizing({:?})", callsite);
 224         self.should_inline(callsite, callee_body)
 225             && self.tcx.consider_optimizing(|| {
 226                 format!("Inline {:?} into {:?}", callee_body.span, callsite)
 227             })
 228     }
 229
 230     fn should_inline(&self, callsite: CallSite<'tcx>, callee_body: &Body<'tcx>) -> bool {
 231         debug!("should_inline({:?})", callsite);
 232         let tcx = self.tcx;
 233
 234         // Cannot inline generators which haven't been transformed yet
 235         if callee_body.yield_ty.is_some() {
 236             debug!("    yield ty present - not inlining");
 237             return false;
 238         }
 239
 240         let codegen_fn_attrs = tcx.codegen_fn_attrs(callsite.callee);
 241
 242         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::TRACK_CALLER) {
 243             debug!("`#[track_caller]` present - not inlining");
 244             return false;
 245         }
 246
 247         let self_features = &self.codegen_fn_attrs.target_features;
 248         let callee_features = &codegen_fn_attrs.target_features;
 249         if callee_features.iter().any(|feature| !self_features.contains(feature)) {
 250             debug!("`callee has extra target features - not inlining");
 251             return false;
 252         }
 253
 254         let self_no_sanitize =
 255             self.codegen_fn_attrs.no_sanitize & self.tcx.sess.opts.debugging_opts.sanitizer;
 256         let callee_no_sanitize =
 257             codegen_fn_attrs.no_sanitize & self.tcx.sess.opts.debugging_opts.sanitizer;
 258         if self_no_sanitize != callee_no_sanitize {
 259             debug!("`callee has incompatible no_sanitize attribute - not inlining");
 260             return false;
 261         }
 262
 263         let hinted = match codegen_fn_attrs.inline {
 264             // Just treat inline(always) as a hint for now,
 265             // there are cases that prevent inlining that we
 266             // need to check for first.
 267             attr::InlineAttr::Always => true,
 268             attr::InlineAttr::Never => {
 269                 debug!("`#[inline(never)]` present - not inlining");
 270                 return false;
 271             }
 272             attr::InlineAttr::Hint => true,
 273             attr::InlineAttr::None => false,
 274         };
 275
 276         // Only inline local functions if they would be eligible for cross-crate
 277         // inlining. This is to ensure that the final crate doesn't have MIR that
 278         // reference unexported symbols
 279         if callsite.callee.is_local() {
 280             if callsite.substs.non_erasable_generics().count() == 0 && !hinted {
 281                 debug!("    callee is an exported function - not inlining");
 282                 return false;
 283             }
 284         }
 285
 286         let mut threshold = if hinted { HINT_THRESHOLD } else { DEFAULT_THRESHOLD };
 287
 288         // Significantly lower the threshold for inlining cold functions
 289         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
 290             threshold /= 5;
 291         }
 292
 293         // Give a bonus functions with a small number of blocks,
 294         // We normally have two or three blocks for even
 295         // very small functions.
 296         if callee_body.basic_blocks().len() <= 3 {
 297             threshold += threshold / 4;
 298         }
 299         debug!("    final inline threshold = {}", threshold);
 300
 301         // FIXME: Give a bonus to functions with only a single caller
 302
 303         let param_env = tcx.param_env(self.source.def_id());
 304
 305         let mut first_block = true;
 306         let mut cost = 0;
 307
 308         // Traverse the MIR manually so we can account for the effects of
 309         // inlining on the CFG.
 310         let mut work_list = vec![START_BLOCK];
 311         let mut visited = BitSet::new_empty(callee_body.basic_blocks().len());
 312         while let Some(bb) = work_list.pop() {
 313             if !visited.insert(bb.index()) {
 314                 continue;
 315             }
 316             let blk = &callee_body.basic_blocks()[bb];
 317
 318             for stmt in &blk.statements {
 319                 // Don't count StorageLive/StorageDead in the inlining cost.
 320                 match stmt.kind {
 321                     StatementKind::StorageLive(_)
 322                     | StatementKind::StorageDead(_)
 323                     | StatementKind::Nop => {}
 324                     _ => cost += INSTR_COST,
 325                 }
 326             }
 327             let term = blk.terminator();
 328             let mut is_drop = false;
 329             match term.kind {
 330                 TerminatorKind::Drop { ref place, target, unwind }
 331                 | TerminatorKind::DropAndReplace { ref place, target, unwind, .. } => {
 332                     is_drop = true;
 333                     work_list.push(target);
 334                     // If the place doesn't actually need dropping, treat it like
 335                     // a regular goto.
 336                     let ty = place.ty(callee_body, tcx).subst(tcx, callsite.substs).ty;
 337                     if ty.needs_drop(tcx, param_env) {
 338                         cost += CALL_PENALTY;
 339                         if let Some(unwind) = unwind {
 340                             cost += LANDINGPAD_PENALTY;
 341                             work_list.push(unwind);
 342                         }
 343                     } else {
 344                         cost += INSTR_COST;
 345                     }
 346                 }
 347
 348                 TerminatorKind::Unreachable | TerminatorKind::Call { destination: None, .. }
 349                     if first_block =>
 350                 {
 351                     // If the function always diverges, don't inline
 352                     // unless the cost is zero
 353                     threshold = 0;
 354                 }
 355
 356                 TerminatorKind::Call { func: Operand::Constant(ref f), cleanup, .. } => {
 357                     if let ty::FnDef(def_id, _) = *f.literal.ty.kind() {
 358                         // Don't give intrinsics the extra penalty for calls
 359                         let f = tcx.fn_sig(def_id);
 360                         if f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic {
 361                             cost += INSTR_COST;
 362                         } else {
 363                             cost += CALL_PENALTY;
 364                         }
 365                     } else {
 366                         cost += CALL_PENALTY;
 367                     }
 368                     if cleanup.is_some() {
 369                         cost += LANDINGPAD_PENALTY;
 370                     }
 371                 }
 372                 TerminatorKind::Assert { cleanup, .. } => {
 373                     cost += CALL_PENALTY;
 374
 375                     if cleanup.is_some() {
 376                         cost += LANDINGPAD_PENALTY;
 377                     }
 378                 }
 379                 TerminatorKind::Resume => cost += RESUME_PENALTY,
 380                 _ => cost += INSTR_COST,
 381             }
 382
 383             if !is_drop {
 384                 for &succ in term.successors() {
 385                     work_list.push(succ);
 386                 }
 387             }
 388
 389             first_block = false;
 390         }
 391
 392         // Count up the cost of local variables and temps, if we know the size
 393         // use that, otherwise we use a moderately-large dummy cost.
 394
 395         let ptr_size = tcx.data_layout.pointer_size.bytes();
 396
 397         for v in callee_body.vars_and_temps_iter() {
 398             let v = &callee_body.local_decls[v];
 399             let ty = v.ty.subst(tcx, callsite.substs);
 400             // Cost of the var is the size in machine-words, if we know
 401             // it.
 402             if let Some(size) = type_size_of(tcx, param_env, ty) {
 403                 cost += (size / ptr_size) as usize;
 404             } else {
 405                 cost += UNKNOWN_SIZE_COST;
 406             }
 407         }
 408
 409         if let attr::InlineAttr::Always = codegen_fn_attrs.inline {
 410             debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
 411             true
 412         } else {
 413             if cost <= threshold {
 414                 debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
 415                 true
 416             } else {
 417                 debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
 418                 false
 419             }
 420         }
 421     }
 422
 423     fn inline_call(
 424         &self,
 425         callsite: CallSite<'tcx>,
 426         caller_body: &mut Body<'tcx>,
 427         mut callee_body: Body<'tcx>,
 428     ) -> bool {
 429         let terminator = caller_body[callsite.bb].terminator.take().unwrap();
 430         match terminator.kind {
 431             // FIXME: Handle inlining of diverging calls
 432             TerminatorKind::Call { args, destination: Some(destination), cleanup, .. } => {
 433                 debug!("inlined {:?} into {:?}", callsite.callee, self.source);
 434
 435                 let mut local_map = IndexVec::with_capacity(callee_body.local_decls.len());
 436                 let mut scope_map = IndexVec::with_capacity(callee_body.source_scopes.len());
 437
 438                 for mut scope in callee_body.source_scopes.iter().cloned() {
 439                     if scope.parent_scope.is_none() {
 440                         scope.parent_scope = Some(callsite.location.scope);
 441                         // FIXME(eddyb) is this really needed?
 442                         // (also note that it's always overwritten below)
 443                         scope.span = callee_body.span;
 444                     }
 445
 446                     // FIXME(eddyb) this doesn't seem right at all.
 447                     // The inlined source scopes should probably be annotated as
 448                     // such, but also contain all of the original information.
 449                     scope.span = callsite.location.span;
 450
 451                     let idx = caller_body.source_scopes.push(scope);
 452                     scope_map.push(idx);
 453                 }
 454
 455                 for loc in callee_body.vars_and_temps_iter() {
 456                     let mut local = callee_body.local_decls[loc].clone();
 457
 458                     local.source_info.scope = scope_map[local.source_info.scope];
 459                     local.source_info.span = callsite.location.span;
 460
 461                     let idx = caller_body.local_decls.push(local);
 462                     local_map.push(idx);
 463                 }
 464
 465                 // If the call is something like `a[*i] = f(i)`, where
 466                 // `i : &mut usize`, then just duplicating the `a[*i]`
 467                 // Place could result in two different locations if `f`
 468                 // writes to `i`. To prevent this we need to create a temporary
 469                 // borrow of the place and pass the destination as `*temp` instead.
 470                 fn dest_needs_borrow(place: Place<'_>) -> bool {
 471                     for elem in place.projection.iter() {
 472                         match elem {
 473                             ProjectionElem::Deref | ProjectionElem::Index(_) => return true,
 474                             _ => {}
 475                         }
 476                     }
 477
 478                     false
 479                 }
 480
 481                 let dest = if dest_needs_borrow(destination.0) {
 482                     debug!("creating temp for return destination");
 483                     let dest = Rvalue::Ref(
 484                         self.tcx.lifetimes.re_erased,
 485                         BorrowKind::Mut { allow_two_phase_borrow: false },
 486                         destination.0,
 487                     );
 488
 489                     let ty = dest.ty(caller_body, self.tcx);
 490
 491                     let temp = LocalDecl::new(ty, callsite.location.span);
 492
 493                     let tmp = caller_body.local_decls.push(temp);
 494                     let tmp = Place::from(tmp);
 495
 496                     let stmt = Statement {
 497                         source_info: callsite.location,
 498                         kind: StatementKind::Assign(box (tmp, dest)),
 499                     };
 500                     caller_body[callsite.bb].statements.push(stmt);
 501                     self.tcx.mk_place_deref(tmp)
 502                 } else {
 503                     destination.0
 504                 };
 505
 506                 let return_block = destination.1;
 507
 508                 // Copy the arguments if needed.
 509                 let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, return_block);
 510
 511                 let bb_len = caller_body.basic_blocks().len();
 512                 let mut integrator = Integrator {
 513                     block_idx: bb_len,
 514                     args: &args,
 515                     local_map,
 516                     scope_map,
 517                     destination: dest,
 518                     return_block,
 519                     cleanup_block: cleanup,
 520                     in_cleanup_block: false,
 521                     tcx: self.tcx,
 522                 };
 523
 524                 for mut var_debug_info in callee_body.var_debug_info.drain(..) {
 525                     integrator.visit_var_debug_info(&mut var_debug_info);
 526                     caller_body.var_debug_info.push(var_debug_info);
 527                 }
 528
 529                 for (bb, mut block) in callee_body.basic_blocks_mut().drain_enumerated(..) {
 530                     integrator.visit_basic_block_data(bb, &mut block);
 531                     caller_body.basic_blocks_mut().push(block);
 532                 }
 533
 534                 let terminator = Terminator {
 535                     source_info: callsite.location,
 536                     kind: TerminatorKind::Goto { target: BasicBlock::new(bb_len) },
 537                 };
 538
 539                 caller_body[callsite.bb].terminator = Some(terminator);
 540
 541                 true
 542             }
 543             kind => {
 544                 caller_body[callsite.bb].terminator =
 545                     Some(Terminator { source_info: terminator.source_info, kind });
 546                 false
 547             }
 548         }
 549     }
 550
 551     fn make_call_args(
 552         &self,
 553         args: Vec<Operand<'tcx>>,
 554         callsite: &CallSite<'tcx>,
 555         caller_body: &mut Body<'tcx>,
 556         return_block: BasicBlock,
 557     ) -> Vec<Local> {
 558         let tcx = self.tcx;
 559
 560         // There is a bit of a mismatch between the *caller* of a closure and the *callee*.
 561         // The caller provides the arguments wrapped up in a tuple:
 562         //
 563         //     tuple_tmp = (a, b, c)
 564         //     Fn::call(closure_ref, tuple_tmp)
 565         //
 566         // meanwhile the closure body expects the arguments (here, `a`, `b`, and `c`)
 567         // as distinct arguments. (This is the "rust-call" ABI hack.) Normally, codegen has
 568         // the job of unpacking this tuple. But here, we are codegen. =) So we want to create
 569         // a vector like
 570         //
 571         //     [closure_ref, tuple_tmp.0, tuple_tmp.1, tuple_tmp.2]
 572         //
 573         // Except for one tiny wrinkle: we don't actually want `tuple_tmp.0`. It's more convenient
 574         // if we "spill" that into *another* temporary, so that we can map the argument
 575         // variable in the callee MIR directly to an argument variable on our side.
 576         // So we introduce temporaries like:
 577         //
 578         //     tmp0 = tuple_tmp.0
 579         //     tmp1 = tuple_tmp.1
 580         //     tmp2 = tuple_tmp.2
 581         //
 582         // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
 583         if tcx.is_closure(callsite.callee) {
 584             let mut args = args.into_iter();
 585             let self_ = self.create_temp_if_necessary(
 586                 args.next().unwrap(),
 587                 callsite,
 588                 caller_body,
 589                 return_block,
 590             );
 591             let tuple = self.create_temp_if_necessary(
 592                 args.next().unwrap(),
 593                 callsite,
 594                 caller_body,
 595                 return_block,
 596             );
 597             assert!(args.next().is_none());
 598
 599             let tuple = Place::from(tuple);
 600             let tuple_tys = if let ty::Tuple(s) = tuple.ty(caller_body, tcx).ty.kind() {
 601                 s
 602             } else {
 603                 bug!("Closure arguments are not passed as a tuple");
 604             };
 605
 606             // The `closure_ref` in our example above.
 607             let closure_ref_arg = iter::once(self_);
 608
 609             // The `tmp0`, `tmp1`, and `tmp2` in our example abonve.
 610             let tuple_tmp_args = tuple_tys.iter().enumerate().map(|(i, ty)| {
 611                 // This is e.g., `tuple_tmp.0` in our example above.
 612                 let tuple_field =
 613                     Operand::Move(tcx.mk_place_field(tuple, Field::new(i), ty.expect_ty()));
 614
 615                 // Spill to a local to make e.g., `tmp0`.
 616                 self.create_temp_if_necessary(tuple_field, callsite, caller_body, return_block)
 617             });
 618
 619             closure_ref_arg.chain(tuple_tmp_args).collect()
 620         } else {
 621             args.into_iter()
 622                 .map(|a| self.create_temp_if_necessary(a, callsite, caller_body, return_block))
 623                 .collect()
 624         }
 625     }
 626
 627     /// If `arg` is already a temporary, returns it. Otherwise, introduces a fresh
 628     /// temporary `T` and an instruction `T = arg`, and returns `T`.
 629     fn create_temp_if_necessary(
 630         &self,
 631         arg: Operand<'tcx>,
 632         callsite: &CallSite<'tcx>,
 633         caller_body: &mut Body<'tcx>,
 634         return_block: BasicBlock,
 635     ) -> Local {
 636         // FIXME: Analysis of the usage of the arguments to avoid
 637         // unnecessary temporaries.
 638
 639         if let Operand::Move(place) = &arg {
 640             if let Some(local) = place.as_local() {
 641                 if caller_body.local_kind(local) == LocalKind::Temp {
 642                     // Reuse the operand if it's a temporary already
 643                     return local;
 644                 }
 645             }
 646         }
 647
 648         debug!("creating temp for argument {:?}", arg);
 649         // Otherwise, create a temporary for the arg
 650         let arg = Rvalue::Use(arg);
 651
 652         let ty = arg.ty(caller_body, self.tcx);
 653
 654         let arg_tmp = LocalDecl::new(ty, callsite.location.span);
 655         let arg_tmp = caller_body.local_decls.push(arg_tmp);
 656
 657         caller_body[callsite.bb].statements.push(Statement {
 658             source_info: callsite.location,
 659             kind: StatementKind::StorageLive(arg_tmp),
 660         });
 661         caller_body[callsite.bb].statements.push(Statement {
 662             source_info: callsite.location,
 663             kind: StatementKind::Assign(box (Place::from(arg_tmp), arg)),
 664         });
 665         caller_body[return_block].statements.insert(
 666             0,
 667             Statement { source_info: callsite.location, kind: StatementKind::StorageDead(arg_tmp) },
 668         );
 669
 670         arg_tmp
 671     }
 672 }
 673
 674 fn type_size_of<'tcx>(
 675     tcx: TyCtxt<'tcx>,
 676     param_env: ty::ParamEnv<'tcx>,
 677     ty: Ty<'tcx>,
 678 ) -> Option<u64> {
 679     tcx.layout_of(param_env.and(ty)).ok().map(|layout| layout.size.bytes())
 680 }
 681
 682 /**
 683  * Integrator.
 684  *
 685  * Integrates blocks from the callee function into the calling function.
 686  * Updates block indices, references to locals and other control flow
 687  * stuff.
 688 */
 689 struct Integrator<'a, 'tcx> {
 690     block_idx: usize,
 691     args: &'a [Local],
 692     local_map: IndexVec<Local, Local>,
 693     scope_map: IndexVec<SourceScope, SourceScope>,
 694     destination: Place<'tcx>,
 695     return_block: BasicBlock,
 696     cleanup_block: Option<BasicBlock>,
 697     in_cleanup_block: bool,
 698     tcx: TyCtxt<'tcx>,
 699 }
 700
 701 impl<'a, 'tcx> Integrator<'a, 'tcx> {
 702     fn update_target(&self, tgt: BasicBlock) -> BasicBlock {
 703         let new = BasicBlock::new(tgt.index() + self.block_idx);
 704         debug!("updating target `{:?}`, new: `{:?}`", tgt, new);
 705         new
 706     }
 707
 708     fn make_integrate_local(&self, local: Local) -> Local {
 709         if local == RETURN_PLACE {
 710             return self.destination.local;
 711         }
 712
 713         let idx = local.index() - 1;
 714         if idx < self.args.len() {
 715             return self.args[idx];
 716         }
 717
 718         self.local_map[Local::new(idx - self.args.len())]
 719     }
 720 }
 721
 722 impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
 723     fn tcx(&self) -> TyCtxt<'tcx> {
 724         self.tcx
 725     }
 726
 727     fn visit_local(&mut self, local: &mut Local, _ctxt: PlaceContext, _location: Location) {
 728         *local = self.make_integrate_local(*local);
 729     }
 730
 731     fn visit_place(&mut self, place: &mut Place<'tcx>, context: PlaceContext, location: Location) {
 732         // If this is the `RETURN_PLACE`, we need to rebase any projections onto it.
 733         let dest_proj_len = self.destination.projection.len();
 734         if place.local == RETURN_PLACE && dest_proj_len > 0 {
 735             let mut projs = Vec::with_capacity(dest_proj_len + place.projection.len());
 736             projs.extend(self.destination.projection);
 737             projs.extend(place.projection);
 738
 739             place.projection = self.tcx.intern_place_elems(&*projs);
 740         }
 741         // Handles integrating any locals that occur in the base
 742         // or projections
 743         self.super_place(place, context, location)
 744     }
 745
 746     fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
 747         self.in_cleanup_block = data.is_cleanup;
 748         self.super_basic_block_data(block, data);
 749         self.in_cleanup_block = false;
 750     }
 751
 752     fn visit_retag(&mut self, kind: &mut RetagKind, place: &mut Place<'tcx>, loc: Location) {
 753         self.super_retag(kind, place, loc);
 754
 755         // We have to patch all inlined retags to be aware that they are no longer
 756         // happening on function entry.
 757         if *kind == RetagKind::FnEntry {
 758             *kind = RetagKind::Default;
 759         }
 760     }
 761
 762     fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, loc: Location) {
 763         // Don't try to modify the implicit `_0` access on return (`return` terminators are
 764         // replaced down below anyways).
 765         if !matches!(terminator.kind, TerminatorKind::Return) {
 766             self.super_terminator(terminator, loc);
 767         }
 768
 769         match terminator.kind {
 770             TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => bug!(),
 771             TerminatorKind::Goto { ref mut target } => {
 772                 *target = self.update_target(*target);
 773             }
 774             TerminatorKind::SwitchInt { ref mut targets, .. } => {
 775                 for tgt in targets {
 776                     *tgt = self.update_target(*tgt);
 777                 }
 778             }
 779             TerminatorKind::Drop { ref mut target, ref mut unwind, .. }
 780             | TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
 781                 *target = self.update_target(*target);
 782                 if let Some(tgt) = *unwind {
 783                     *unwind = Some(self.update_target(tgt));
 784                 } else if !self.in_cleanup_block {
 785                     // Unless this drop is in a cleanup block, add an unwind edge to
 786                     // the original call's cleanup block
 787                     *unwind = self.cleanup_block;
 788                 }
 789             }
 790             TerminatorKind::Call { ref mut destination, ref mut cleanup, .. } => {
 791                 if let Some((_, ref mut tgt)) = *destination {
 792                     *tgt = self.update_target(*tgt);
 793                 }
 794                 if let Some(tgt) = *cleanup {
 795                     *cleanup = Some(self.update_target(tgt));
 796                 } else if !self.in_cleanup_block {
 797                     // Unless this call is in a cleanup block, add an unwind edge to
 798                     // the original call's cleanup block
 799                     *cleanup = self.cleanup_block;
 800                 }
 801             }
 802             TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
 803                 *target = self.update_target(*target);
 804                 if let Some(tgt) = *cleanup {
 805                     *cleanup = Some(self.update_target(tgt));
 806                 } else if !self.in_cleanup_block {
 807                     // Unless this assert is in a cleanup block, add an unwind edge to
 808                     // the original call's cleanup block
 809                     *cleanup = self.cleanup_block;
 810                 }
 811             }
 812             TerminatorKind::Return => {
 813                 terminator.kind = TerminatorKind::Goto { target: self.return_block };
 814             }
 815             TerminatorKind::Resume => {
 816                 if let Some(tgt) = self.cleanup_block {
 817                     terminator.kind = TerminatorKind::Goto { target: tgt }
 818                 }
 819             }
 820             TerminatorKind::Abort => {}
 821             TerminatorKind::Unreachable => {}
 822             TerminatorKind::FalseEdge { ref mut real_target, ref mut imaginary_target } => {
 823                 *real_target = self.update_target(*real_target);
 824                 *imaginary_target = self.update_target(*imaginary_target);
 825             }
 826             TerminatorKind::FalseUnwind { real_target: _, unwind: _ } =>
 827             // see the ordering of passes in the optimized_mir query.
 828             {
 829                 bug!("False unwinds should have been removed before inlining")
 830             }
 831             TerminatorKind::InlineAsm { ref mut destination, .. } => {
 832                 if let Some(ref mut tgt) = *destination {
 833                     *tgt = self.update_target(*tgt);
 834                 }
 835             }
 836         }
 837     }
 838
 839     fn visit_source_scope(&mut self, scope: &mut SourceScope) {
 840         *scope = self.scope_map[*scope];
 841     }
 842 }