compiler/rustc_mir/src/transform/inline.rs

   1 //! Inlining pass for MIR functions
   2
   3 use rustc_attr as attr;
   4 use rustc_hir as hir;
   5 use rustc_index::bit_set::BitSet;
   6 use rustc_index::vec::Idx;
   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;
  11 use rustc_middle::ty::{self, ConstKind, Instance, InstanceDef, ParamEnv, Ty, TyCtxt};
  12 use rustc_span::{hygiene::ExpnKind, ExpnData, Span};
  13 use rustc_target::spec::abi::Abi;
  14
  15 use super::simplify::{remove_dead_blocks, CfgSimplifier};
  16 use crate::transform::MirPass;
  17 use std::iter;
  18 use std::ops::{Range, RangeFrom};
  19
  20 const INSTR_COST: usize = 5;
  21 const CALL_PENALTY: usize = 25;
  22 const LANDINGPAD_PENALTY: usize = 50;
  23 const RESUME_PENALTY: usize = 45;
  24
  25 const UNKNOWN_SIZE_COST: usize = 10;
  26
  27 pub struct Inline;
  28
  29 #[derive(Copy, Clone, Debug)]
  30 struct CallSite<'tcx> {
  31     callee: Instance<'tcx>,
  32     fn_sig: ty::PolyFnSig<'tcx>,
  33     block: BasicBlock,
  34     target: Option<BasicBlock>,
  35     source_info: SourceInfo,
  36 }
  37
  38 impl<'tcx> MirPass<'tcx> for Inline {
  39     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
  40         if tcx.sess.opts.debugging_opts.mir_opt_level < 2 {
  41             return;
  42         }
  43
  44         if tcx.sess.opts.debugging_opts.instrument_coverage {
  45             // Since `Inline` happens after `InstrumentCoverage`, the function-specific coverage
  46             // counters can be invalidated, such as by merging coverage counter statements from
  47             // a pre-inlined function into a different function. This kind of change is invalid,
  48             // so inlining must be skipped. Note: This check is performed here so inlining can
  49             // be disabled without preventing other optimizations (regardless of `mir_opt_level`).
  50             return;
  51         }
  52
  53         if inline(tcx, body) {
  54             debug!("running simplify cfg on {:?}", body.source);
  55             CfgSimplifier::new(body).simplify();
  56             remove_dead_blocks(body);
  57         }
  58     }
  59 }
  60
  61 fn inline(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) -> bool {
  62     let def_id = body.source.def_id();
  63     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
  64
  65     // Only do inlining into fn bodies.
  66     if !tcx.hir().body_owner_kind(hir_id).is_fn_or_closure() {
  67         return false;
  68     }
  69     if body.source.promoted.is_some() {
  70         return false;
  71     }
  72
  73     let mut this = Inliner {
  74         tcx,
  75         param_env: tcx.param_env_reveal_all_normalized(body.source.def_id()),
  76         codegen_fn_attrs: tcx.codegen_fn_attrs(body.source.def_id()),
  77         hir_id,
  78         history: Vec::new(),
  79         changed: false,
  80     };
  81     let blocks = BasicBlock::new(0)..body.basic_blocks().next_index();
  82     this.process_blocks(body, blocks);
  83     this.changed
  84 }
  85
  86 struct Inliner<'tcx> {
  87     tcx: TyCtxt<'tcx>,
  88     param_env: ParamEnv<'tcx>,
  89     /// Caller codegen attributes.
  90     codegen_fn_attrs: &'tcx CodegenFnAttrs,
  91     /// Caller HirID.
  92     hir_id: hir::HirId,
  93     /// Stack of inlined instances.
  94     history: Vec<Instance<'tcx>>,
  95     /// Indicates that the caller body has been modified.
  96     changed: bool,
  97 }
  98
  99 impl Inliner<'tcx> {
 100     fn process_blocks(&mut self, caller_body: &mut Body<'tcx>, blocks: Range<BasicBlock>) {
 101         for bb in blocks {
 102             let callsite = match self.get_valid_function_call(bb, &caller_body[bb], caller_body) {
 103                 None => continue,
 104                 Some(it) => it,
 105             };
 106
 107             if !self.is_mir_available(&callsite.callee, caller_body) {
 108                 debug!("MIR unavailable {}", callsite.callee);
 109                 continue;
 110             }
 111
 112             let callee_body = self.tcx.instance_mir(callsite.callee.def);
 113             if !self.should_inline(callsite, callee_body) {
 114                 continue;
 115             }
 116
 117             if !self.tcx.consider_optimizing(|| {
 118                 format!("Inline {:?} into {}", callee_body.span, callsite.callee)
 119             }) {
 120                 return;
 121             }
 122
 123             let callee_body = callsite.callee.subst_mir_and_normalize_erasing_regions(
 124                 self.tcx,
 125                 self.param_env,
 126                 callee_body.clone(),
 127             );
 128
 129             let old_blocks = caller_body.basic_blocks().next_index();
 130             self.inline_call(callsite, caller_body, callee_body);
 131             let new_blocks = old_blocks..caller_body.basic_blocks().next_index();
 132             self.changed = true;
 133
 134             self.history.push(callsite.callee);
 135             self.process_blocks(caller_body, new_blocks);
 136             self.history.pop();
 137         }
 138     }
 139
 140     fn is_mir_available(&self, callee: &Instance<'tcx>, caller_body: &Body<'tcx>) -> bool {
 141         if let InstanceDef::Item(_) = callee.def {
 142             if !self.tcx.is_mir_available(callee.def_id()) {
 143                 return false;
 144             }
 145         }
 146
 147         if let Some(callee_def_id) = callee.def_id().as_local() {
 148             let callee_hir_id = self.tcx.hir().local_def_id_to_hir_id(callee_def_id);
 149             // Avoid a cycle here by only using `instance_mir` only if we have
 150             // a lower `HirId` than the callee. This ensures that the callee will
 151             // not inline us. This trick only works without incremental compilation.
 152             // So don't do it if that is enabled. Also avoid inlining into generators,
 153             // since their `optimized_mir` is used for layout computation, which can
 154             // create a cycle, even when no attempt is made to inline the function
 155             // in the other direction.
 156             !self.tcx.dep_graph.is_fully_enabled()
 157                 && self.hir_id < callee_hir_id
 158                 && caller_body.generator_kind.is_none()
 159         } else {
 160             // This cannot result in a cycle since the callee MIR is from another crate
 161             // and is already optimized.
 162             true
 163         }
 164     }
 165
 166     fn get_valid_function_call(
 167         &self,
 168         bb: BasicBlock,
 169         bb_data: &BasicBlockData<'tcx>,
 170         caller_body: &Body<'tcx>,
 171     ) -> Option<CallSite<'tcx>> {
 172         // Don't inline calls that are in cleanup blocks.
 173         if bb_data.is_cleanup {
 174             return None;
 175         }
 176
 177         // Only consider direct calls to functions
 178         let terminator = bb_data.terminator();
 179         if let TerminatorKind::Call { ref func, ref destination, .. } = terminator.kind {
 180             let func_ty = func.ty(caller_body, self.tcx);
 181             if let ty::FnDef(def_id, substs) = *func_ty.kind() {
 182                 // To resolve an instance its substs have to be fully normalized.
 183                 let substs = self.tcx.normalize_erasing_regions(self.param_env, substs);
 184                 let callee =
 185                     Instance::resolve(self.tcx, self.param_env, def_id, substs).ok().flatten()?;
 186
 187                 if let InstanceDef::Virtual(..) | InstanceDef::Intrinsic(_) = callee.def {
 188                     return None;
 189                 }
 190
 191                 let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, substs);
 192
 193                 return Some(CallSite {
 194                     callee,
 195                     fn_sig,
 196                     block: bb,
 197                     target: destination.map(|(_, target)| target),
 198                     source_info: terminator.source_info,
 199                 });
 200             }
 201         }
 202
 203         None
 204     }
 205
 206     fn should_inline(&self, callsite: CallSite<'tcx>, callee_body: &Body<'tcx>) -> bool {
 207         debug!("should_inline({:?})", callsite);
 208         let tcx = self.tcx;
 209
 210         if callsite.fn_sig.c_variadic() {
 211             debug!("callee is variadic - not inlining");
 212             return false;
 213         }
 214
 215         let codegen_fn_attrs = tcx.codegen_fn_attrs(callsite.callee.def_id());
 216
 217         let self_features = &self.codegen_fn_attrs.target_features;
 218         let callee_features = &codegen_fn_attrs.target_features;
 219         if callee_features.iter().any(|feature| !self_features.contains(feature)) {
 220             debug!("`callee has extra target features - not inlining");
 221             return false;
 222         }
 223
 224         if self.codegen_fn_attrs.no_sanitize != codegen_fn_attrs.no_sanitize {
 225             debug!("`callee has incompatible no_sanitize attribute - not inlining");
 226             return false;
 227         }
 228
 229         let hinted = match codegen_fn_attrs.inline {
 230             // Just treat inline(always) as a hint for now,
 231             // there are cases that prevent inlining that we
 232             // need to check for first.
 233             attr::InlineAttr::Always => true,
 234             attr::InlineAttr::Never => {
 235                 debug!("`#[inline(never)]` present - not inlining");
 236                 return false;
 237             }
 238             attr::InlineAttr::Hint => true,
 239             attr::InlineAttr::None => false,
 240         };
 241
 242         // Only inline local functions if they would be eligible for cross-crate
 243         // inlining. This is to ensure that the final crate doesn't have MIR that
 244         // reference unexported symbols
 245         if callsite.callee.def_id().is_local() {
 246             if callsite.callee.substs.non_erasable_generics().count() == 0 && !hinted {
 247                 debug!("    callee is an exported function - not inlining");
 248                 return false;
 249             }
 250         }
 251
 252         let mut threshold = if hinted {
 253             self.tcx.sess.opts.debugging_opts.inline_mir_hint_threshold
 254         } else {
 255             self.tcx.sess.opts.debugging_opts.inline_mir_threshold
 256         };
 257
 258         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
 259             debug!("#[naked] present - not inlining");
 260             return false;
 261         }
 262
 263         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
 264             debug!("#[cold] present - not inlining");
 265             return false;
 266         }
 267
 268         // Give a bonus functions with a small number of blocks,
 269         // We normally have two or three blocks for even
 270         // very small functions.
 271         if callee_body.basic_blocks().len() <= 3 {
 272             threshold += threshold / 4;
 273         }
 274         debug!("    final inline threshold = {}", threshold);
 275
 276         // FIXME: Give a bonus to functions with only a single caller
 277         let mut first_block = true;
 278         let mut cost = 0;
 279
 280         // Traverse the MIR manually so we can account for the effects of
 281         // inlining on the CFG.
 282         let mut work_list = vec![START_BLOCK];
 283         let mut visited = BitSet::new_empty(callee_body.basic_blocks().len());
 284         while let Some(bb) = work_list.pop() {
 285             if !visited.insert(bb.index()) {
 286                 continue;
 287             }
 288             let blk = &callee_body.basic_blocks()[bb];
 289
 290             for stmt in &blk.statements {
 291                 // Don't count StorageLive/StorageDead in the inlining cost.
 292                 match stmt.kind {
 293                     StatementKind::StorageLive(_)
 294                     | StatementKind::StorageDead(_)
 295                     | StatementKind::Nop => {}
 296                     _ => cost += INSTR_COST,
 297                 }
 298             }
 299             let term = blk.terminator();
 300             let mut is_drop = false;
 301             match term.kind {
 302                 TerminatorKind::Drop { ref place, target, unwind }
 303                 | TerminatorKind::DropAndReplace { ref place, target, unwind, .. } => {
 304                     is_drop = true;
 305                     work_list.push(target);
 306                     // If the place doesn't actually need dropping, treat it like
 307                     // a regular goto.
 308                     let ty = callsite.callee.subst_mir(self.tcx, &place.ty(callee_body, tcx).ty);
 309                     if ty.needs_drop(tcx, self.param_env) {
 310                         cost += CALL_PENALTY;
 311                         if let Some(unwind) = unwind {
 312                             cost += LANDINGPAD_PENALTY;
 313                             work_list.push(unwind);
 314                         }
 315                     } else {
 316                         cost += INSTR_COST;
 317                     }
 318                 }
 319
 320                 TerminatorKind::Unreachable | TerminatorKind::Call { destination: None, .. }
 321                     if first_block =>
 322                 {
 323                     // If the function always diverges, don't inline
 324                     // unless the cost is zero
 325                     threshold = 0;
 326                 }
 327
 328                 TerminatorKind::Call { func: Operand::Constant(ref f), cleanup, .. } => {
 329                     if let ty::FnDef(def_id, substs) =
 330                         *callsite.callee.subst_mir(self.tcx, &f.literal.ty).kind()
 331                     {
 332                         let substs = self.tcx.normalize_erasing_regions(self.param_env, substs);
 333                         if let Ok(Some(instance)) =
 334                             Instance::resolve(self.tcx, self.param_env, def_id, substs)
 335                         {
 336                             if callsite.callee == instance || self.history.contains(&instance) {
 337                                 debug!("`callee is recursive - not inlining");
 338                                 return false;
 339                             }
 340                         }
 341                         // Don't give intrinsics the extra penalty for calls
 342                         let f = tcx.fn_sig(def_id);
 343                         if f.abi() == Abi::RustIntrinsic || f.abi() == Abi::PlatformIntrinsic {
 344                             cost += INSTR_COST;
 345                         } else {
 346                             cost += CALL_PENALTY;
 347                         }
 348                     } else {
 349                         cost += CALL_PENALTY;
 350                     }
 351                     if cleanup.is_some() {
 352                         cost += LANDINGPAD_PENALTY;
 353                     }
 354                 }
 355                 TerminatorKind::Assert { cleanup, .. } => {
 356                     cost += CALL_PENALTY;
 357
 358                     if cleanup.is_some() {
 359                         cost += LANDINGPAD_PENALTY;
 360                     }
 361                 }
 362                 TerminatorKind::Resume => cost += RESUME_PENALTY,
 363                 _ => cost += INSTR_COST,
 364             }
 365
 366             if !is_drop {
 367                 for &succ in term.successors() {
 368                     work_list.push(succ);
 369                 }
 370             }
 371
 372             first_block = false;
 373         }
 374
 375         // Count up the cost of local variables and temps, if we know the size
 376         // use that, otherwise we use a moderately-large dummy cost.
 377
 378         let ptr_size = tcx.data_layout.pointer_size.bytes();
 379
 380         for v in callee_body.vars_and_temps_iter() {
 381             let ty = callsite.callee.subst_mir(self.tcx, &callee_body.local_decls[v].ty);
 382             // Cost of the var is the size in machine-words, if we know
 383             // it.
 384             if let Some(size) = type_size_of(tcx, self.param_env, ty) {
 385                 cost += (size / ptr_size) as usize;
 386             } else {
 387                 cost += UNKNOWN_SIZE_COST;
 388             }
 389         }
 390
 391         if let attr::InlineAttr::Always = codegen_fn_attrs.inline {
 392             debug!("INLINING {:?} because inline(always) [cost={}]", callsite, cost);
 393             true
 394         } else {
 395             if cost <= threshold {
 396                 debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
 397                 true
 398             } else {
 399                 debug!("NOT inlining {:?} [cost={} > threshold={}]", callsite, cost, threshold);
 400                 false
 401             }
 402         }
 403     }
 404
 405     fn inline_call(
 406         &self,
 407         callsite: CallSite<'tcx>,
 408         caller_body: &mut Body<'tcx>,
 409         mut callee_body: Body<'tcx>,
 410     ) {
 411         let terminator = caller_body[callsite.block].terminator.take().unwrap();
 412         match terminator.kind {
 413             TerminatorKind::Call { args, destination, cleanup, .. } => {
 414                 // If the call is something like `a[*i] = f(i)`, where
 415                 // `i : &mut usize`, then just duplicating the `a[*i]`
 416                 // Place could result in two different locations if `f`
 417                 // writes to `i`. To prevent this we need to create a temporary
 418                 // borrow of the place and pass the destination as `*temp` instead.
 419                 fn dest_needs_borrow(place: Place<'_>) -> bool {
 420                     for elem in place.projection.iter() {
 421                         match elem {
 422                             ProjectionElem::Deref | ProjectionElem::Index(_) => return true,
 423                             _ => {}
 424                         }
 425                     }
 426
 427                     false
 428                 }
 429
 430                 let dest = if let Some((destination_place, _)) = destination {
 431                     if dest_needs_borrow(destination_place) {
 432                         trace!("creating temp for return destination");
 433                         let dest = Rvalue::Ref(
 434                             self.tcx.lifetimes.re_erased,
 435                             BorrowKind::Mut { allow_two_phase_borrow: false },
 436                             destination_place,
 437                         );
 438                         let dest_ty = dest.ty(caller_body, self.tcx);
 439                         let temp = Place::from(self.new_call_temp(caller_body, &callsite, dest_ty));
 440                         caller_body[callsite.block].statements.push(Statement {
 441                             source_info: callsite.source_info,
 442                             kind: StatementKind::Assign(box (temp, dest)),
 443                         });
 444                         self.tcx.mk_place_deref(temp)
 445                     } else {
 446                         destination_place
 447                     }
 448                 } else {
 449                     trace!("creating temp for return place");
 450                     Place::from(self.new_call_temp(caller_body, &callsite, callee_body.return_ty()))
 451                 };
 452
 453                 // Copy the arguments if needed.
 454                 let args: Vec<_> = self.make_call_args(args, &callsite, caller_body, &callee_body);
 455
 456                 let mut integrator = Integrator {
 457                     args: &args,
 458                     new_locals: Local::new(caller_body.local_decls.len())..,
 459                     new_scopes: SourceScope::new(caller_body.source_scopes.len())..,
 460                     new_blocks: BasicBlock::new(caller_body.basic_blocks().len())..,
 461                     destination: dest,
 462                     return_block: callsite.target,
 463                     cleanup_block: cleanup,
 464                     in_cleanup_block: false,
 465                     tcx: self.tcx,
 466                     callsite_span: callsite.source_info.span,
 467                     body_span: callee_body.span,
 468                     always_live_locals: BitSet::new_filled(callee_body.local_decls.len()),
 469                 };
 470
 471                 // Map all `Local`s, `SourceScope`s and `BasicBlock`s to new ones
 472                 // (or existing ones, in a few special cases) in the caller.
 473                 integrator.visit_body(&mut callee_body);
 474
 475                 for scope in &mut callee_body.source_scopes {
 476                     // FIXME(eddyb) move this into a `fn visit_scope_data` in `Integrator`.
 477                     if scope.parent_scope.is_none() {
 478                         let callsite_scope = &caller_body.source_scopes[callsite.source_info.scope];
 479
 480                         // Attach the outermost callee scope as a child of the callsite
 481                         // scope, via the `parent_scope` and `inlined_parent_scope` chains.
 482                         scope.parent_scope = Some(callsite.source_info.scope);
 483                         assert_eq!(scope.inlined_parent_scope, None);
 484                         scope.inlined_parent_scope = if callsite_scope.inlined.is_some() {
 485                             Some(callsite.source_info.scope)
 486                         } else {
 487                             callsite_scope.inlined_parent_scope
 488                         };
 489
 490                         // Mark the outermost callee scope as an inlined one.
 491                         assert_eq!(scope.inlined, None);
 492                         scope.inlined = Some((callsite.callee, callsite.source_info.span));
 493                     } else if scope.inlined_parent_scope.is_none() {
 494                         // Make it easy to find the scope with `inlined` set above.
 495                         scope.inlined_parent_scope =
 496                             Some(integrator.map_scope(OUTERMOST_SOURCE_SCOPE));
 497                     }
 498                 }
 499
 500                 // If there are any locals without storage markers, give them storage only for the
 501                 // duration of the call.
 502                 for local in callee_body.vars_and_temps_iter() {
 503                     if integrator.always_live_locals.contains(local) {
 504                         let new_local = integrator.map_local(local);
 505                         caller_body[callsite.block].statements.push(Statement {
 506                             source_info: callsite.source_info,
 507                             kind: StatementKind::StorageLive(new_local),
 508                         });
 509                     }
 510                 }
 511                 if let Some(block) = callsite.target {
 512                     // To avoid repeated O(n) insert, push any new statements to the end and rotate
 513                     // the slice once.
 514                     let mut n = 0;
 515                     for local in callee_body.vars_and_temps_iter().rev() {
 516                         if integrator.always_live_locals.contains(local) {
 517                             let new_local = integrator.map_local(local);
 518                             caller_body[block].statements.push(Statement {
 519                                 source_info: callsite.source_info,
 520                                 kind: StatementKind::StorageDead(new_local),
 521                             });
 522                             n += 1;
 523                         }
 524                     }
 525                     caller_body[block].statements.rotate_right(n);
 526                 }
 527
 528                 // Insert all of the (mapped) parts of the callee body into the caller.
 529                 caller_body.local_decls.extend(
 530                     // FIXME(eddyb) make `Range<Local>` iterable so that we can use
 531                     // `callee_body.local_decls.drain(callee_body.vars_and_temps())`
 532                     callee_body
 533                         .vars_and_temps_iter()
 534                         .map(|local| callee_body.local_decls[local].clone()),
 535                 );
 536                 caller_body.source_scopes.extend(callee_body.source_scopes.drain(..));
 537                 caller_body.var_debug_info.extend(callee_body.var_debug_info.drain(..));
 538                 caller_body.basic_blocks_mut().extend(callee_body.basic_blocks_mut().drain(..));
 539
 540                 caller_body[callsite.block].terminator = Some(Terminator {
 541                     source_info: callsite.source_info,
 542                     kind: TerminatorKind::Goto { target: integrator.map_block(START_BLOCK) },
 543                 });
 544
 545                 // Copy only unevaluated constants from the callee_body into the caller_body.
 546                 // Although we are only pushing `ConstKind::Unevaluated` consts to
 547                 // `required_consts`, here we may not only have `ConstKind::Unevaluated`
 548                 // because we are calling `subst_and_normalize_erasing_regions`.
 549                 caller_body.required_consts.extend(
 550                     callee_body.required_consts.iter().copied().filter(|&constant| {
 551                         matches!(constant.literal.val, ConstKind::Unevaluated(_, _, _))
 552                     }),
 553                 );
 554             }
 555             kind => bug!("unexpected terminator kind {:?}", kind),
 556         }
 557     }
 558
 559     fn make_call_args(
 560         &self,
 561         args: Vec<Operand<'tcx>>,
 562         callsite: &CallSite<'tcx>,
 563         caller_body: &mut Body<'tcx>,
 564         callee_body: &Body<'tcx>,
 565     ) -> Vec<Local> {
 566         let tcx = self.tcx;
 567
 568         // There is a bit of a mismatch between the *caller* of a closure and the *callee*.
 569         // The caller provides the arguments wrapped up in a tuple:
 570         //
 571         //     tuple_tmp = (a, b, c)
 572         //     Fn::call(closure_ref, tuple_tmp)
 573         //
 574         // meanwhile the closure body expects the arguments (here, `a`, `b`, and `c`)
 575         // as distinct arguments. (This is the "rust-call" ABI hack.) Normally, codegen has
 576         // the job of unpacking this tuple. But here, we are codegen. =) So we want to create
 577         // a vector like
 578         //
 579         //     [closure_ref, tuple_tmp.0, tuple_tmp.1, tuple_tmp.2]
 580         //
 581         // Except for one tiny wrinkle: we don't actually want `tuple_tmp.0`. It's more convenient
 582         // if we "spill" that into *another* temporary, so that we can map the argument
 583         // variable in the callee MIR directly to an argument variable on our side.
 584         // So we introduce temporaries like:
 585         //
 586         //     tmp0 = tuple_tmp.0
 587         //     tmp1 = tuple_tmp.1
 588         //     tmp2 = tuple_tmp.2
 589         //
 590         // and the vector is `[closure_ref, tmp0, tmp1, tmp2]`.
 591         if callsite.fn_sig.abi() == Abi::RustCall && callee_body.spread_arg.is_none() {
 592             let mut args = args.into_iter();
 593             let self_ = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
 594             let tuple = self.create_temp_if_necessary(args.next().unwrap(), callsite, caller_body);
 595             assert!(args.next().is_none());
 596
 597             let tuple = Place::from(tuple);
 598             let tuple_tys = if let ty::Tuple(s) = tuple.ty(caller_body, tcx).ty.kind() {
 599                 s
 600             } else {
 601                 bug!("Closure arguments are not passed as a tuple");
 602             };
 603
 604             // The `closure_ref` in our example above.
 605             let closure_ref_arg = iter::once(self_);
 606
 607             // The `tmp0`, `tmp1`, and `tmp2` in our example abonve.
 608             let tuple_tmp_args = tuple_tys.iter().enumerate().map(|(i, ty)| {
 609                 // This is e.g., `tuple_tmp.0` in our example above.
 610                 let tuple_field =
 611                     Operand::Move(tcx.mk_place_field(tuple, Field::new(i), ty.expect_ty()));
 612
 613                 // Spill to a local to make e.g., `tmp0`.
 614                 self.create_temp_if_necessary(tuple_field, callsite, caller_body)
 615             });
 616
 617             closure_ref_arg.chain(tuple_tmp_args).collect()
 618         } else {
 619             args.into_iter()
 620                 .map(|a| self.create_temp_if_necessary(a, callsite, caller_body))
 621                 .collect()
 622         }
 623     }
 624
 625     /// If `arg` is already a temporary, returns it. Otherwise, introduces a fresh
 626     /// temporary `T` and an instruction `T = arg`, and returns `T`.
 627     fn create_temp_if_necessary(
 628         &self,
 629         arg: Operand<'tcx>,
 630         callsite: &CallSite<'tcx>,
 631         caller_body: &mut Body<'tcx>,
 632     ) -> Local {
 633         // Reuse the operand if it is a moved temporary.
 634         if let Operand::Move(place) = &arg {
 635             if let Some(local) = place.as_local() {
 636                 if caller_body.local_kind(local) == LocalKind::Temp {
 637                     return local;
 638                 }
 639             }
 640         }
 641
 642         // Otherwise, create a temporary for the argument.
 643         trace!("creating temp for argument {:?}", arg);
 644         let arg_ty = arg.ty(caller_body, self.tcx);
 645         let local = self.new_call_temp(caller_body, callsite, arg_ty);
 646         caller_body[callsite.block].statements.push(Statement {
 647             source_info: callsite.source_info,
 648             kind: StatementKind::Assign(box (Place::from(local), Rvalue::Use(arg))),
 649         });
 650         local
 651     }
 652
 653     /// Introduces a new temporary into the caller body that is live for the duration of the call.
 654     fn new_call_temp(
 655         &self,
 656         caller_body: &mut Body<'tcx>,
 657         callsite: &CallSite<'tcx>,
 658         ty: Ty<'tcx>,
 659     ) -> Local {
 660         let local = caller_body.local_decls.push(LocalDecl::new(ty, callsite.source_info.span));
 661
 662         caller_body[callsite.block].statements.push(Statement {
 663             source_info: callsite.source_info,
 664             kind: StatementKind::StorageLive(local),
 665         });
 666
 667         if let Some(block) = callsite.target {
 668             caller_body[block].statements.insert(
 669                 0,
 670                 Statement {
 671                     source_info: callsite.source_info,
 672                     kind: StatementKind::StorageDead(local),
 673                 },
 674             );
 675         }
 676
 677         local
 678     }
 679 }
 680
 681 fn type_size_of<'tcx>(
 682     tcx: TyCtxt<'tcx>,
 683     param_env: ty::ParamEnv<'tcx>,
 684     ty: Ty<'tcx>,
 685 ) -> Option<u64> {
 686     tcx.layout_of(param_env.and(ty)).ok().map(|layout| layout.size.bytes())
 687 }
 688
 689 /**
 690  * Integrator.
 691  *
 692  * Integrates blocks from the callee function into the calling function.
 693  * Updates block indices, references to locals and other control flow
 694  * stuff.
 695 */
 696 struct Integrator<'a, 'tcx> {
 697     args: &'a [Local],
 698     new_locals: RangeFrom<Local>,
 699     new_scopes: RangeFrom<SourceScope>,
 700     new_blocks: RangeFrom<BasicBlock>,
 701     destination: Place<'tcx>,
 702     return_block: Option<BasicBlock>,
 703     cleanup_block: Option<BasicBlock>,
 704     in_cleanup_block: bool,
 705     tcx: TyCtxt<'tcx>,
 706     callsite_span: Span,
 707     body_span: Span,
 708     always_live_locals: BitSet<Local>,
 709 }
 710
 711 impl<'a, 'tcx> Integrator<'a, 'tcx> {
 712     fn map_local(&self, local: Local) -> Local {
 713         let new = if local == RETURN_PLACE {
 714             self.destination.local
 715         } else {
 716             let idx = local.index() - 1;
 717             if idx < self.args.len() {
 718                 self.args[idx]
 719             } else {
 720                 Local::new(self.new_locals.start.index() + (idx - self.args.len()))
 721             }
 722         };
 723         trace!("mapping local `{:?}` to `{:?}`", local, new);
 724         new
 725     }
 726
 727     fn map_scope(&self, scope: SourceScope) -> SourceScope {
 728         let new = SourceScope::new(self.new_scopes.start.index() + scope.index());
 729         trace!("mapping scope `{:?}` to `{:?}`", scope, new);
 730         new
 731     }
 732
 733     fn map_block(&self, block: BasicBlock) -> BasicBlock {
 734         let new = BasicBlock::new(self.new_blocks.start.index() + block.index());
 735         trace!("mapping block `{:?}` to `{:?}`", block, new);
 736         new
 737     }
 738 }
 739
 740 impl<'a, 'tcx> MutVisitor<'tcx> for Integrator<'a, 'tcx> {
 741     fn tcx(&self) -> TyCtxt<'tcx> {
 742         self.tcx
 743     }
 744
 745     fn visit_local(&mut self, local: &mut Local, _ctxt: PlaceContext, _location: Location) {
 746         *local = self.map_local(*local);
 747     }
 748
 749     fn visit_source_scope(&mut self, scope: &mut SourceScope) {
 750         *scope = self.map_scope(*scope);
 751     }
 752
 753     fn visit_span(&mut self, span: &mut Span) {
 754         let mut expn_data =
 755             ExpnData::default(ExpnKind::Inlined, *span, self.tcx.sess.edition(), None);
 756         expn_data.def_site = self.body_span;
 757         // Make sure that all spans track the fact that they were inlined.
 758         *span = self.callsite_span.fresh_expansion(expn_data);
 759     }
 760
 761     fn visit_place(&mut self, place: &mut Place<'tcx>, context: PlaceContext, location: Location) {
 762         for elem in place.projection {
 763             // FIXME: Make sure that return place is not used in an indexing projection, since it
 764             // won't be rebased as it is supposed to be.
 765             assert_ne!(ProjectionElem::Index(RETURN_PLACE), elem);
 766         }
 767
 768         // If this is the `RETURN_PLACE`, we need to rebase any projections onto it.
 769         let dest_proj_len = self.destination.projection.len();
 770         if place.local == RETURN_PLACE && dest_proj_len > 0 {
 771             let mut projs = Vec::with_capacity(dest_proj_len + place.projection.len());
 772             projs.extend(self.destination.projection);
 773             projs.extend(place.projection);
 774
 775             place.projection = self.tcx.intern_place_elems(&*projs);
 776         }
 777         // Handles integrating any locals that occur in the base
 778         // or projections
 779         self.super_place(place, context, location)
 780     }
 781
 782     fn visit_basic_block_data(&mut self, block: BasicBlock, data: &mut BasicBlockData<'tcx>) {
 783         self.in_cleanup_block = data.is_cleanup;
 784         self.super_basic_block_data(block, data);
 785         self.in_cleanup_block = false;
 786     }
 787
 788     fn visit_retag(&mut self, kind: &mut RetagKind, place: &mut Place<'tcx>, loc: Location) {
 789         self.super_retag(kind, place, loc);
 790
 791         // We have to patch all inlined retags to be aware that they are no longer
 792         // happening on function entry.
 793         if *kind == RetagKind::FnEntry {
 794             *kind = RetagKind::Default;
 795         }
 796     }
 797
 798     fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
 799         if let StatementKind::StorageLive(local) | StatementKind::StorageDead(local) =
 800             statement.kind
 801         {
 802             self.always_live_locals.remove(local);
 803         }
 804         self.super_statement(statement, location);
 805     }
 806
 807     fn visit_terminator(&mut self, terminator: &mut Terminator<'tcx>, loc: Location) {
 808         // Don't try to modify the implicit `_0` access on return (`return` terminators are
 809         // replaced down below anyways).
 810         if !matches!(terminator.kind, TerminatorKind::Return) {
 811             self.super_terminator(terminator, loc);
 812         }
 813
 814         match terminator.kind {
 815             TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => bug!(),
 816             TerminatorKind::Goto { ref mut target } => {
 817                 *target = self.map_block(*target);
 818             }
 819             TerminatorKind::SwitchInt { ref mut targets, .. } => {
 820                 for tgt in targets.all_targets_mut() {
 821                     *tgt = self.map_block(*tgt);
 822                 }
 823             }
 824             TerminatorKind::Drop { ref mut target, ref mut unwind, .. }
 825             | TerminatorKind::DropAndReplace { ref mut target, ref mut unwind, .. } => {
 826                 *target = self.map_block(*target);
 827                 if let Some(tgt) = *unwind {
 828                     *unwind = Some(self.map_block(tgt));
 829                 } else if !self.in_cleanup_block {
 830                     // Unless this drop is in a cleanup block, add an unwind edge to
 831                     // the original call's cleanup block
 832                     *unwind = self.cleanup_block;
 833                 }
 834             }
 835             TerminatorKind::Call { ref mut destination, ref mut cleanup, .. } => {
 836                 if let Some((_, ref mut tgt)) = *destination {
 837                     *tgt = self.map_block(*tgt);
 838                 }
 839                 if let Some(tgt) = *cleanup {
 840                     *cleanup = Some(self.map_block(tgt));
 841                 } else if !self.in_cleanup_block {
 842                     // Unless this call is in a cleanup block, add an unwind edge to
 843                     // the original call's cleanup block
 844                     *cleanup = self.cleanup_block;
 845                 }
 846             }
 847             TerminatorKind::Assert { ref mut target, ref mut cleanup, .. } => {
 848                 *target = self.map_block(*target);
 849                 if let Some(tgt) = *cleanup {
 850                     *cleanup = Some(self.map_block(tgt));
 851                 } else if !self.in_cleanup_block {
 852                     // Unless this assert is in a cleanup block, add an unwind edge to
 853                     // the original call's cleanup block
 854                     *cleanup = self.cleanup_block;
 855                 }
 856             }
 857             TerminatorKind::Return => {
 858                 terminator.kind = if let Some(tgt) = self.return_block {
 859                     TerminatorKind::Goto { target: tgt }
 860                 } else {
 861                     TerminatorKind::Unreachable
 862                 }
 863             }
 864             TerminatorKind::Resume => {
 865                 if let Some(tgt) = self.cleanup_block {
 866                     terminator.kind = TerminatorKind::Goto { target: tgt }
 867                 }
 868             }
 869             TerminatorKind::Abort => {}
 870             TerminatorKind::Unreachable => {}
 871             TerminatorKind::FalseEdge { ref mut real_target, ref mut imaginary_target } => {
 872                 *real_target = self.map_block(*real_target);
 873                 *imaginary_target = self.map_block(*imaginary_target);
 874             }
 875             TerminatorKind::FalseUnwind { real_target: _, unwind: _ } =>
 876             // see the ordering of passes in the optimized_mir query.
 877             {
 878                 bug!("False unwinds should have been removed before inlining")
 879             }
 880             TerminatorKind::InlineAsm { ref mut destination, .. } => {
 881                 if let Some(ref mut tgt) = *destination {
 882                     *tgt = self.map_block(*tgt);
 883                 }
 884             }
 885         }
 886     }
 887 }