compiler/rustc_codegen_ssa/src/mir/block.rs

   1 use super::operand::OperandRef;
   2 use super::operand::OperandValue::{Immediate, Pair, Ref};
   3 use super::place::PlaceRef;
   4 use super::{CachedLlbb, FunctionCx, LocalRef};
   5
   6 use crate::base;
   7 use crate::common::{self, IntPredicate};
   8 use crate::meth;
   9 use crate::traits::*;
  10 use crate::MemFlags;
  11
  12 use rustc_ast as ast;
  13 use rustc_ast::{InlineAsmOptions, InlineAsmTemplatePiece};
  14 use rustc_hir::lang_items::LangItem;
  15 use rustc_index::vec::Idx;
  16 use rustc_middle::mir::{self, AssertKind, SwitchTargets};
  17 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf, ValidityRequirement};
  18 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
  19 use rustc_middle::ty::{self, Instance, Ty};
  20 use rustc_session::config::OptLevel;
  21 use rustc_span::source_map::Span;
  22 use rustc_span::{sym, Symbol};
  23 use rustc_symbol_mangling::typeid::typeid_for_fnabi;
  24 use rustc_target::abi::call::{ArgAbi, FnAbi, PassMode, Reg};
  25 use rustc_target::abi::{self, HasDataLayout, WrappingRange};
  26 use rustc_target::spec::abi::Abi;
  27
  28 // Indicates if we are in the middle of merging a BB's successor into it. This
  29 // can happen when BB jumps directly to its successor and the successor has no
  30 // other predecessors.
  31 #[derive(Debug, PartialEq)]
  32 enum MergingSucc {
  33     False,
  34     True,
  35 }
  36
  37 /// Used by `FunctionCx::codegen_terminator` for emitting common patterns
  38 /// e.g., creating a basic block, calling a function, etc.
  39 struct TerminatorCodegenHelper<'tcx> {
  40     bb: mir::BasicBlock,
  41     terminator: &'tcx mir::Terminator<'tcx>,
  42 }
  43
  44 impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
  45     /// Returns the appropriate `Funclet` for the current funclet, if on MSVC,
  46     /// either already previously cached, or newly created, by `landing_pad_for`.
  47     fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
  48         &self,
  49         fx: &'b mut FunctionCx<'a, 'tcx, Bx>,
  50     ) -> Option<&'b Bx::Funclet> {
  51         let cleanup_kinds = (&fx.cleanup_kinds).as_ref()?;
  52         let funclet_bb = cleanup_kinds[self.bb].funclet_bb(self.bb)?;
  53         // If `landing_pad_for` hasn't been called yet to create the `Funclet`,
  54         // it has to be now. This may not seem necessary, as RPO should lead
  55         // to all the unwind edges being visited (and so to `landing_pad_for`
  56         // getting called for them), before building any of the blocks inside
  57         // the funclet itself - however, if MIR contains edges that end up not
  58         // being needed in the LLVM IR after monomorphization, the funclet may
  59         // be unreachable, and we don't have yet a way to skip building it in
  60         // such an eventuality (which may be a better solution than this).
  61         if fx.funclets[funclet_bb].is_none() {
  62             fx.landing_pad_for(funclet_bb);
  63         }
  64         Some(
  65             fx.funclets[funclet_bb]
  66                 .as_ref()
  67                 .expect("landing_pad_for didn't also create funclets entry"),
  68         )
  69     }
  70
  71     /// Get a basic block (creating it if necessary), possibly with cleanup
  72     /// stuff in it or next to it.
  73     fn llbb_with_cleanup<Bx: BuilderMethods<'a, 'tcx>>(
  74         &self,
  75         fx: &mut FunctionCx<'a, 'tcx, Bx>,
  76         target: mir::BasicBlock,
  77     ) -> Bx::BasicBlock {
  78         let (needs_landing_pad, is_cleanupret) = self.llbb_characteristics(fx, target);
  79         let mut lltarget = fx.llbb(target);
  80         if needs_landing_pad {
  81             lltarget = fx.landing_pad_for(target);
  82         }
  83         if is_cleanupret {
  84             // MSVC cross-funclet jump - need a trampoline
  85             debug_assert!(base::wants_msvc_seh(fx.cx.tcx().sess));
  86             debug!("llbb_with_cleanup: creating cleanup trampoline for {:?}", target);
  87             let name = &format!("{:?}_cleanup_trampoline_{:?}", self.bb, target);
  88             let trampoline_llbb = Bx::append_block(fx.cx, fx.llfn, name);
  89             let mut trampoline_bx = Bx::build(fx.cx, trampoline_llbb);
  90             trampoline_bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
  91             trampoline_llbb
  92         } else {
  93             lltarget
  94         }
  95     }
  96
  97     fn llbb_characteristics<Bx: BuilderMethods<'a, 'tcx>>(
  98         &self,
  99         fx: &mut FunctionCx<'a, 'tcx, Bx>,
 100         target: mir::BasicBlock,
 101     ) -> (bool, bool) {
 102         if let Some(ref cleanup_kinds) = fx.cleanup_kinds {
 103             let funclet_bb = cleanup_kinds[self.bb].funclet_bb(self.bb);
 104             let target_funclet = cleanup_kinds[target].funclet_bb(target);
 105             let (needs_landing_pad, is_cleanupret) = match (funclet_bb, target_funclet) {
 106                 (None, None) => (false, false),
 107                 (None, Some(_)) => (true, false),
 108                 (Some(f), Some(t_f)) => (f != t_f, f != t_f),
 109                 (Some(_), None) => {
 110                     let span = self.terminator.source_info.span;
 111                     span_bug!(span, "{:?} - jump out of cleanup?", self.terminator);
 112                 }
 113             };
 114             (needs_landing_pad, is_cleanupret)
 115         } else {
 116             let needs_landing_pad = !fx.mir[self.bb].is_cleanup && fx.mir[target].is_cleanup;
 117             let is_cleanupret = false;
 118             (needs_landing_pad, is_cleanupret)
 119         }
 120     }
 121
 122     fn funclet_br<Bx: BuilderMethods<'a, 'tcx>>(
 123         &self,
 124         fx: &mut FunctionCx<'a, 'tcx, Bx>,
 125         bx: &mut Bx,
 126         target: mir::BasicBlock,
 127         mergeable_succ: bool,
 128     ) -> MergingSucc {
 129         let (needs_landing_pad, is_cleanupret) = self.llbb_characteristics(fx, target);
 130         if mergeable_succ && !needs_landing_pad && !is_cleanupret {
 131             // We can merge the successor into this bb, so no need for a `br`.
 132             MergingSucc::True
 133         } else {
 134             let mut lltarget = fx.llbb(target);
 135             if needs_landing_pad {
 136                 lltarget = fx.landing_pad_for(target);
 137             }
 138             if is_cleanupret {
 139                 // micro-optimization: generate a `ret` rather than a jump
 140                 // to a trampoline.
 141                 bx.cleanup_ret(self.funclet(fx).unwrap(), Some(lltarget));
 142             } else {
 143                 bx.br(lltarget);
 144             }
 145             MergingSucc::False
 146         }
 147     }
 148
 149     /// Call `fn_ptr` of `fn_abi` with the arguments `llargs`, the optional
 150     /// return destination `destination` and the unwind action `unwind`.
 151     fn do_call<Bx: BuilderMethods<'a, 'tcx>>(
 152         &self,
 153         fx: &mut FunctionCx<'a, 'tcx, Bx>,
 154         bx: &mut Bx,
 155         fn_abi: &'tcx FnAbi<'tcx, Ty<'tcx>>,
 156         fn_ptr: Bx::Value,
 157         llargs: &[Bx::Value],
 158         destination: Option<(ReturnDest<'tcx, Bx::Value>, mir::BasicBlock)>,
 159         mut unwind: mir::UnwindAction,
 160         copied_constant_arguments: &[PlaceRef<'tcx, <Bx as BackendTypes>::Value>],
 161         mergeable_succ: bool,
 162     ) -> MergingSucc {
 163         // If there is a cleanup block and the function we're calling can unwind, then
 164         // do an invoke, otherwise do a call.
 165         let fn_ty = bx.fn_decl_backend_type(&fn_abi);
 166
 167         if !fn_abi.can_unwind {
 168             unwind = mir::UnwindAction::Unreachable;
 169         }
 170
 171         let unwind_block = match unwind {
 172             mir::UnwindAction::Cleanup(cleanup) => Some(self.llbb_with_cleanup(fx, cleanup)),
 173             mir::UnwindAction::Continue => None,
 174             mir::UnwindAction::Unreachable => None,
 175             mir::UnwindAction::Terminate => {
 176                 if fx.mir[self.bb].is_cleanup && base::wants_msvc_seh(fx.cx.tcx().sess) {
 177                     // SEH will abort automatically if an exception tries to
 178                     // propagate out from cleanup.
 179                     None
 180                 } else {
 181                     Some(fx.terminate_block())
 182                 }
 183             }
 184         };
 185
 186         if let Some(unwind_block) = unwind_block {
 187             let ret_llbb = if let Some((_, target)) = destination {
 188                 fx.llbb(target)
 189             } else {
 190                 fx.unreachable_block()
 191             };
 192             let invokeret = bx.invoke(
 193                 fn_ty,
 194                 Some(&fn_abi),
 195                 fn_ptr,
 196                 &llargs,
 197                 ret_llbb,
 198                 unwind_block,
 199                 self.funclet(fx),
 200             );
 201             if fx.mir[self.bb].is_cleanup {
 202                 bx.do_not_inline(invokeret);
 203             }
 204
 205             if let Some((ret_dest, target)) = destination {
 206                 bx.switch_to_block(fx.llbb(target));
 207                 fx.set_debug_loc(bx, self.terminator.source_info);
 208                 for tmp in copied_constant_arguments {
 209                     bx.lifetime_end(tmp.llval, tmp.layout.size);
 210                 }
 211                 fx.store_return(bx, ret_dest, &fn_abi.ret, invokeret);
 212             }
 213             MergingSucc::False
 214         } else {
 215             let llret = bx.call(fn_ty, Some(&fn_abi), fn_ptr, &llargs, self.funclet(fx));
 216             if fx.mir[self.bb].is_cleanup {
 217                 // Cleanup is always the cold path. Don't inline
 218                 // drop glue. Also, when there is a deeply-nested
 219                 // struct, there are "symmetry" issues that cause
 220                 // exponential inlining - see issue #41696.
 221                 bx.do_not_inline(llret);
 222             }
 223
 224             if let Some((ret_dest, target)) = destination {
 225                 for tmp in copied_constant_arguments {
 226                     bx.lifetime_end(tmp.llval, tmp.layout.size);
 227                 }
 228                 fx.store_return(bx, ret_dest, &fn_abi.ret, llret);
 229                 self.funclet_br(fx, bx, target, mergeable_succ)
 230             } else {
 231                 bx.unreachable();
 232                 MergingSucc::False
 233             }
 234         }
 235     }
 236
 237     /// Generates inline assembly with optional `destination` and `unwind`.
 238     fn do_inlineasm<Bx: BuilderMethods<'a, 'tcx>>(
 239         &self,
 240         fx: &mut FunctionCx<'a, 'tcx, Bx>,
 241         bx: &mut Bx,
 242         template: &[InlineAsmTemplatePiece],
 243         operands: &[InlineAsmOperandRef<'tcx, Bx>],
 244         options: InlineAsmOptions,
 245         line_spans: &[Span],
 246         destination: Option<mir::BasicBlock>,
 247         unwind: mir::UnwindAction,
 248         instance: Instance<'_>,
 249         mergeable_succ: bool,
 250     ) -> MergingSucc {
 251         let unwind_target = match unwind {
 252             mir::UnwindAction::Cleanup(cleanup) => Some(self.llbb_with_cleanup(fx, cleanup)),
 253             mir::UnwindAction::Terminate => Some(fx.terminate_block()),
 254             mir::UnwindAction::Continue => None,
 255             mir::UnwindAction::Unreachable => None,
 256         };
 257
 258         if let Some(cleanup) = unwind_target {
 259             let ret_llbb = if let Some(target) = destination {
 260                 fx.llbb(target)
 261             } else {
 262                 fx.unreachable_block()
 263             };
 264
 265             bx.codegen_inline_asm(
 266                 template,
 267                 &operands,
 268                 options,
 269                 line_spans,
 270                 instance,
 271                 Some((ret_llbb, cleanup, self.funclet(fx))),
 272             );
 273             MergingSucc::False
 274         } else {
 275             bx.codegen_inline_asm(template, &operands, options, line_spans, instance, None);
 276
 277             if let Some(target) = destination {
 278                 self.funclet_br(fx, bx, target, mergeable_succ)
 279             } else {
 280                 bx.unreachable();
 281                 MergingSucc::False
 282             }
 283         }
 284     }
 285 }
 286
 287 /// Codegen implementations for some terminator variants.
 288 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 289     /// Generates code for a `Resume` terminator.
 290     fn codegen_resume_terminator(&mut self, helper: TerminatorCodegenHelper<'tcx>, bx: &mut Bx) {
 291         if let Some(funclet) = helper.funclet(self) {
 292             bx.cleanup_ret(funclet, None);
 293         } else {
 294             let slot = self.get_personality_slot(bx);
 295             let exn0 = slot.project_field(bx, 0);
 296             let exn0 = bx.load_operand(exn0).immediate();
 297             let exn1 = slot.project_field(bx, 1);
 298             let exn1 = bx.load_operand(exn1).immediate();
 299             slot.storage_dead(bx);
 300
 301             bx.resume(exn0, exn1);
 302         }
 303     }
 304
 305     fn codegen_switchint_terminator(
 306         &mut self,
 307         helper: TerminatorCodegenHelper<'tcx>,
 308         bx: &mut Bx,
 309         discr: &mir::Operand<'tcx>,
 310         targets: &SwitchTargets,
 311     ) {
 312         let discr = self.codegen_operand(bx, &discr);
 313         let switch_ty = discr.layout.ty;
 314         let mut target_iter = targets.iter();
 315         if target_iter.len() == 1 {
 316             // If there are two targets (one conditional, one fallback), emit `br` instead of
 317             // `switch`.
 318             let (test_value, target) = target_iter.next().unwrap();
 319             let lltrue = helper.llbb_with_cleanup(self, target);
 320             let llfalse = helper.llbb_with_cleanup(self, targets.otherwise());
 321             if switch_ty == bx.tcx().types.bool {
 322                 // Don't generate trivial icmps when switching on bool.
 323                 match test_value {
 324                     0 => bx.cond_br(discr.immediate(), llfalse, lltrue),
 325                     1 => bx.cond_br(discr.immediate(), lltrue, llfalse),
 326                     _ => bug!(),
 327                 }
 328             } else {
 329                 let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
 330                 let llval = bx.const_uint_big(switch_llty, test_value);
 331                 let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 332                 bx.cond_br(cmp, lltrue, llfalse);
 333             }
 334         } else if self.cx.sess().opts.optimize == OptLevel::No
 335             && target_iter.len() == 2
 336             && self.mir[targets.otherwise()].is_empty_unreachable()
 337         {
 338             // In unoptimized builds, if there are two normal targets and the `otherwise` target is
 339             // an unreachable BB, emit `br` instead of `switch`. This leaves behind the unreachable
 340             // BB, which will usually (but not always) be dead code.
 341             //
 342             // Why only in unoptimized builds?
 343             // - In unoptimized builds LLVM uses FastISel which does not support switches, so it
 344             //   must fall back to the to the slower SelectionDAG isel. Therefore, using `br` gives
 345             //   significant compile time speedups for unoptimized builds.
 346             // - In optimized builds the above doesn't hold, and using `br` sometimes results in
 347             //   worse generated code because LLVM can no longer tell that the value being switched
 348             //   on can only have two values, e.g. 0 and 1.
 349             //
 350             let (test_value1, target1) = target_iter.next().unwrap();
 351             let (_test_value2, target2) = target_iter.next().unwrap();
 352             let ll1 = helper.llbb_with_cleanup(self, target1);
 353             let ll2 = helper.llbb_with_cleanup(self, target2);
 354             let switch_llty = bx.immediate_backend_type(bx.layout_of(switch_ty));
 355             let llval = bx.const_uint_big(switch_llty, test_value1);
 356             let cmp = bx.icmp(IntPredicate::IntEQ, discr.immediate(), llval);
 357             bx.cond_br(cmp, ll1, ll2);
 358         } else {
 359             bx.switch(
 360                 discr.immediate(),
 361                 helper.llbb_with_cleanup(self, targets.otherwise()),
 362                 target_iter.map(|(value, target)| (value, helper.llbb_with_cleanup(self, target))),
 363             );
 364         }
 365     }
 366
 367     fn codegen_return_terminator(&mut self, bx: &mut Bx) {
 368         // Call `va_end` if this is the definition of a C-variadic function.
 369         if self.fn_abi.c_variadic {
 370             // The `VaList` "spoofed" argument is just after all the real arguments.
 371             let va_list_arg_idx = self.fn_abi.args.len();
 372             match self.locals[mir::Local::new(1 + va_list_arg_idx)] {
 373                 LocalRef::Place(va_list) => {
 374                     bx.va_end(va_list.llval);
 375                 }
 376                 _ => bug!("C-variadic function must have a `VaList` place"),
 377             }
 378         }
 379         if self.fn_abi.ret.layout.abi.is_uninhabited() {
 380             // Functions with uninhabited return values are marked `noreturn`,
 381             // so we should make sure that we never actually do.
 382             // We play it safe by using a well-defined `abort`, but we could go for immediate UB
 383             // if that turns out to be helpful.
 384             bx.abort();
 385             // `abort` does not terminate the block, so we still need to generate
 386             // an `unreachable` terminator after it.
 387             bx.unreachable();
 388             return;
 389         }
 390         let llval = match &self.fn_abi.ret.mode {
 391             PassMode::Ignore | PassMode::Indirect { .. } => {
 392                 bx.ret_void();
 393                 return;
 394             }
 395
 396             PassMode::Direct(_) | PassMode::Pair(..) => {
 397                 let op = self.codegen_consume(bx, mir::Place::return_place().as_ref());
 398                 if let Ref(llval, _, align) = op.val {
 399                     bx.load(bx.backend_type(op.layout), llval, align)
 400                 } else {
 401                     op.immediate_or_packed_pair(bx)
 402                 }
 403             }
 404
 405             PassMode::Cast(cast_ty, _) => {
 406                 let op = match self.locals[mir::RETURN_PLACE] {
 407                     LocalRef::Operand(op) => op,
 408                     LocalRef::PendingOperand => bug!("use of return before def"),
 409                     LocalRef::Place(cg_place) => OperandRef {
 410                         val: Ref(cg_place.llval, None, cg_place.align),
 411                         layout: cg_place.layout,
 412                     },
 413                     LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
 414                 };
 415                 let llslot = match op.val {
 416                     Immediate(_) | Pair(..) => {
 417                         let scratch = PlaceRef::alloca(bx, self.fn_abi.ret.layout);
 418                         op.val.store(bx, scratch);
 419                         scratch.llval
 420                     }
 421                     Ref(llval, _, align) => {
 422                         assert_eq!(align, op.layout.align.abi, "return place is unaligned!");
 423                         llval
 424                     }
 425                 };
 426                 let ty = bx.cast_backend_type(cast_ty);
 427                 let addr = bx.pointercast(llslot, bx.type_ptr_to(ty));
 428                 bx.load(ty, addr, self.fn_abi.ret.layout.align.abi)
 429             }
 430         };
 431         bx.ret(llval);
 432     }
 433
 434     #[tracing::instrument(level = "trace", skip(self, helper, bx))]
 435     fn codegen_drop_terminator(
 436         &mut self,
 437         helper: TerminatorCodegenHelper<'tcx>,
 438         bx: &mut Bx,
 439         location: mir::Place<'tcx>,
 440         target: mir::BasicBlock,
 441         unwind: mir::UnwindAction,
 442         mergeable_succ: bool,
 443     ) -> MergingSucc {
 444         let ty = location.ty(self.mir, bx.tcx()).ty;
 445         let ty = self.monomorphize(ty);
 446         let drop_fn = Instance::resolve_drop_in_place(bx.tcx(), ty);
 447
 448         if let ty::InstanceDef::DropGlue(_, None) = drop_fn.def {
 449             // we don't actually need to drop anything.
 450             return helper.funclet_br(self, bx, target, mergeable_succ);
 451         }
 452
 453         let place = self.codegen_place(bx, location.as_ref());
 454         let (args1, args2);
 455         let mut args = if let Some(llextra) = place.llextra {
 456             args2 = [place.llval, llextra];
 457             &args2[..]
 458         } else {
 459             args1 = [place.llval];
 460             &args1[..]
 461         };
 462         let (drop_fn, fn_abi) =
 463             match ty.kind() {
 464                 // FIXME(eddyb) perhaps move some of this logic into
 465                 // `Instance::resolve_drop_in_place`?
 466                 ty::Dynamic(_, _, ty::Dyn) => {
 467                     // IN THIS ARM, WE HAVE:
 468                     // ty = *mut (dyn Trait)
 469                     // which is: exists<T> ( *mut T,    Vtable<T: Trait> )
 470                     //                       args[0]    args[1]
 471                     //
 472                     // args = ( Data, Vtable )
 473                     //                  |
 474                     //                  v
 475                     //                /-------\
 476                     //                | ...   |
 477                     //                \-------/
 478                     //
 479                     let virtual_drop = Instance {
 480                         def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
 481                         substs: drop_fn.substs,
 482                     };
 483                     debug!("ty = {:?}", ty);
 484                     debug!("drop_fn = {:?}", drop_fn);
 485                     debug!("args = {:?}", args);
 486                     let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
 487                     let vtable = args[1];
 488                     // Truncate vtable off of args list
 489                     args = &args[..1];
 490                     (
 491                         meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
 492                             .get_fn(bx, vtable, ty, &fn_abi),
 493                         fn_abi,
 494                     )
 495                 }
 496                 ty::Dynamic(_, _, ty::DynStar) => {
 497                     // IN THIS ARM, WE HAVE:
 498                     // ty = *mut (dyn* Trait)
 499                     // which is: *mut exists<T: sizeof(T) == sizeof(usize)> (T, Vtable<T: Trait>)
 500                     //
 501                     // args = [ * ]
 502                     //          |
 503                     //          v
 504                     //      ( Data, Vtable )
 505                     //                |
 506                     //                v
 507                     //              /-------\
 508                     //              | ...   |
 509                     //              \-------/
 510                     //
 511                     //
 512                     // WE CAN CONVERT THIS INTO THE ABOVE LOGIC BY DOING
 513                     //
 514                     // data = &(*args[0]).0    // gives a pointer to Data above (really the same pointer)
 515                     // vtable = (*args[0]).1   // loads the vtable out
 516                     // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
 517                     //
 518                     // SO THEN WE CAN USE THE ABOVE CODE.
 519                     let virtual_drop = Instance {
 520                         def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
 521                         substs: drop_fn.substs,
 522                     };
 523                     debug!("ty = {:?}", ty);
 524                     debug!("drop_fn = {:?}", drop_fn);
 525                     debug!("args = {:?}", args);
 526                     let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
 527                     let meta_ptr = place.project_field(bx, 1);
 528                     let meta = bx.load_operand(meta_ptr);
 529                     // Truncate vtable off of args list
 530                     args = &args[..1];
 531                     debug!("args' = {:?}", args);
 532                     (
 533                         meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
 534                             .get_fn(bx, meta.immediate(), ty, &fn_abi),
 535                         fn_abi,
 536                     )
 537                 }
 538                 _ => (bx.get_fn_addr(drop_fn), bx.fn_abi_of_instance(drop_fn, ty::List::empty())),
 539             };
 540         helper.do_call(
 541             self,
 542             bx,
 543             fn_abi,
 544             drop_fn,
 545             args,
 546             Some((ReturnDest::Nothing, target)),
 547             unwind,
 548             &[],
 549             mergeable_succ,
 550         )
 551     }
 552
 553     fn codegen_assert_terminator(
 554         &mut self,
 555         helper: TerminatorCodegenHelper<'tcx>,
 556         bx: &mut Bx,
 557         terminator: &mir::Terminator<'tcx>,
 558         cond: &mir::Operand<'tcx>,
 559         expected: bool,
 560         msg: &mir::AssertMessage<'tcx>,
 561         target: mir::BasicBlock,
 562         unwind: mir::UnwindAction,
 563         mergeable_succ: bool,
 564     ) -> MergingSucc {
 565         let span = terminator.source_info.span;
 566         let cond = self.codegen_operand(bx, cond).immediate();
 567         let mut const_cond = bx.const_to_opt_u128(cond, false).map(|c| c == 1);
 568
 569         // This case can currently arise only from functions marked
 570         // with #[rustc_inherit_overflow_checks] and inlined from
 571         // another crate (mostly core::num generic/#[inline] fns),
 572         // while the current crate doesn't use overflow checks.
 573         if !bx.cx().check_overflow() && msg.is_optional_overflow_check() {
 574             const_cond = Some(expected);
 575         }
 576
 577         // Don't codegen the panic block if success if known.
 578         if const_cond == Some(expected) {
 579             return helper.funclet_br(self, bx, target, mergeable_succ);
 580         }
 581
 582         // Pass the condition through llvm.expect for branch hinting.
 583         let cond = bx.expect(cond, expected);
 584
 585         // Create the failure block and the conditional branch to it.
 586         let lltarget = helper.llbb_with_cleanup(self, target);
 587         let panic_block = bx.append_sibling_block("panic");
 588         if expected {
 589             bx.cond_br(cond, lltarget, panic_block);
 590         } else {
 591             bx.cond_br(cond, panic_block, lltarget);
 592         }
 593
 594         // After this point, bx is the block for the call to panic.
 595         bx.switch_to_block(panic_block);
 596         self.set_debug_loc(bx, terminator.source_info);
 597
 598         // Get the location information.
 599         let location = self.get_caller_location(bx, terminator.source_info).immediate();
 600
 601         // Put together the arguments to the panic entry point.
 602         let (lang_item, args) = match msg {
 603             AssertKind::BoundsCheck { ref len, ref index } => {
 604                 let len = self.codegen_operand(bx, len).immediate();
 605                 let index = self.codegen_operand(bx, index).immediate();
 606                 // It's `fn panic_bounds_check(index: usize, len: usize)`,
 607                 // and `#[track_caller]` adds an implicit third argument.
 608                 (LangItem::PanicBoundsCheck, vec![index, len, location])
 609             }
 610             AssertKind::MisalignedPointerDereference { ref required, ref found } => {
 611                 let required = self.codegen_operand(bx, required).immediate();
 612                 let found = self.codegen_operand(bx, found).immediate();
 613                 // It's `fn panic_bounds_check(index: usize, len: usize)`,
 614                 // and `#[track_caller]` adds an implicit third argument.
 615                 (LangItem::PanicMisalignedPointerDereference, vec![required, found, location])
 616             }
 617             _ => {
 618                 let msg = bx.const_str(msg.description());
 619                 // It's `pub fn panic(expr: &str)`, with the wide reference being passed
 620                 // as two arguments, and `#[track_caller]` adds an implicit third argument.
 621                 (LangItem::Panic, vec![msg.0, msg.1, location])
 622             }
 623         };
 624
 625         let (fn_abi, llfn) = common::build_langcall(bx, Some(span), lang_item);
 626
 627         // Codegen the actual panic invoke/call.
 628         let merging_succ = helper.do_call(self, bx, fn_abi, llfn, &args, None, unwind, &[], false);
 629         assert_eq!(merging_succ, MergingSucc::False);
 630         MergingSucc::False
 631     }
 632
 633     fn codegen_terminate_terminator(
 634         &mut self,
 635         helper: TerminatorCodegenHelper<'tcx>,
 636         bx: &mut Bx,
 637         terminator: &mir::Terminator<'tcx>,
 638     ) {
 639         let span = terminator.source_info.span;
 640         self.set_debug_loc(bx, terminator.source_info);
 641
 642         // Obtain the panic entry point.
 643         let (fn_abi, llfn) = common::build_langcall(bx, Some(span), LangItem::PanicCannotUnwind);
 644
 645         // Codegen the actual panic invoke/call.
 646         let merging_succ = helper.do_call(
 647             self,
 648             bx,
 649             fn_abi,
 650             llfn,
 651             &[],
 652             None,
 653             mir::UnwindAction::Unreachable,
 654             &[],
 655             false,
 656         );
 657         assert_eq!(merging_succ, MergingSucc::False);
 658     }
 659
 660     /// Returns `Some` if this is indeed a panic intrinsic and codegen is done.
 661     fn codegen_panic_intrinsic(
 662         &mut self,
 663         helper: &TerminatorCodegenHelper<'tcx>,
 664         bx: &mut Bx,
 665         intrinsic: Option<Symbol>,
 666         instance: Option<Instance<'tcx>>,
 667         source_info: mir::SourceInfo,
 668         target: Option<mir::BasicBlock>,
 669         unwind: mir::UnwindAction,
 670         mergeable_succ: bool,
 671     ) -> Option<MergingSucc> {
 672         // Emit a panic or a no-op for `assert_*` intrinsics.
 673         // These are intrinsics that compile to panics so that we can get a message
 674         // which mentions the offending type, even from a const context.
 675         let panic_intrinsic = intrinsic.and_then(|s| ValidityRequirement::from_intrinsic(s));
 676         if let Some(requirement) = panic_intrinsic {
 677             let ty = instance.unwrap().substs.type_at(0);
 678
 679             let do_panic = !bx
 680                 .tcx()
 681                 .check_validity_requirement((requirement, bx.param_env().and(ty)))
 682                 .expect("expect to have layout during codegen");
 683
 684             let layout = bx.layout_of(ty);
 685
 686             Some(if do_panic {
 687                 let msg_str = with_no_visible_paths!({
 688                     with_no_trimmed_paths!({
 689                         if layout.abi.is_uninhabited() {
 690                             // Use this error even for the other intrinsics as it is more precise.
 691                             format!("attempted to instantiate uninhabited type `{}`", ty)
 692                         } else if requirement == ValidityRequirement::Zero {
 693                             format!("attempted to zero-initialize type `{}`, which is invalid", ty)
 694                         } else {
 695                             format!(
 696                                 "attempted to leave type `{}` uninitialized, which is invalid",
 697                                 ty
 698                             )
 699                         }
 700                     })
 701                 });
 702                 let msg = bx.const_str(&msg_str);
 703
 704                 // Obtain the panic entry point.
 705                 let (fn_abi, llfn) =
 706                     common::build_langcall(bx, Some(source_info.span), LangItem::PanicNounwind);
 707
 708                 // Codegen the actual panic invoke/call.
 709                 helper.do_call(
 710                     self,
 711                     bx,
 712                     fn_abi,
 713                     llfn,
 714                     &[msg.0, msg.1],
 715                     target.as_ref().map(|bb| (ReturnDest::Nothing, *bb)),
 716                     unwind,
 717                     &[],
 718                     mergeable_succ,
 719                 )
 720             } else {
 721                 // a NOP
 722                 let target = target.unwrap();
 723                 helper.funclet_br(self, bx, target, mergeable_succ)
 724             })
 725         } else {
 726             None
 727         }
 728     }
 729
 730     fn codegen_call_terminator(
 731         &mut self,
 732         helper: TerminatorCodegenHelper<'tcx>,
 733         bx: &mut Bx,
 734         terminator: &mir::Terminator<'tcx>,
 735         func: &mir::Operand<'tcx>,
 736         args: &[mir::Operand<'tcx>],
 737         destination: mir::Place<'tcx>,
 738         target: Option<mir::BasicBlock>,
 739         unwind: mir::UnwindAction,
 740         fn_span: Span,
 741         mergeable_succ: bool,
 742     ) -> MergingSucc {
 743         let source_info = terminator.source_info;
 744         let span = source_info.span;
 745
 746         // Create the callee. This is a fn ptr or zero-sized and hence a kind of scalar.
 747         let callee = self.codegen_operand(bx, func);
 748
 749         let (instance, mut llfn) = match *callee.layout.ty.kind() {
 750             ty::FnDef(def_id, substs) => (
 751                 Some(
 752                     ty::Instance::expect_resolve(
 753                         bx.tcx(),
 754                         ty::ParamEnv::reveal_all(),
 755                         def_id,
 756                         substs,
 757                     )
 758                     .polymorphize(bx.tcx()),
 759                 ),
 760                 None,
 761             ),
 762             ty::FnPtr(_) => (None, Some(callee.immediate())),
 763             _ => bug!("{} is not callable", callee.layout.ty),
 764         };
 765         let def = instance.map(|i| i.def);
 766
 767         if let Some(ty::InstanceDef::DropGlue(_, None)) = def {
 768             // Empty drop glue; a no-op.
 769             let target = target.unwrap();
 770             return helper.funclet_br(self, bx, target, mergeable_succ);
 771         }
 772
 773         // FIXME(eddyb) avoid computing this if possible, when `instance` is
 774         // available - right now `sig` is only needed for getting the `abi`
 775         // and figuring out how many extra args were passed to a C-variadic `fn`.
 776         let sig = callee.layout.ty.fn_sig(bx.tcx());
 777         let abi = sig.abi();
 778
 779         // Handle intrinsics old codegen wants Expr's for, ourselves.
 780         let intrinsic = match def {
 781             Some(ty::InstanceDef::Intrinsic(def_id)) => Some(bx.tcx().item_name(def_id)),
 782             _ => None,
 783         };
 784
 785         let extra_args = &args[sig.inputs().skip_binder().len()..];
 786         let extra_args = bx.tcx().mk_type_list_from_iter(extra_args.iter().map(|op_arg| {
 787             let op_ty = op_arg.ty(self.mir, bx.tcx());
 788             self.monomorphize(op_ty)
 789         }));
 790
 791         let fn_abi = match instance {
 792             Some(instance) => bx.fn_abi_of_instance(instance, extra_args),
 793             None => bx.fn_abi_of_fn_ptr(sig, extra_args),
 794         };
 795
 796         if let Some(merging_succ) = self.codegen_panic_intrinsic(
 797             &helper,
 798             bx,
 799             intrinsic,
 800             instance,
 801             source_info,
 802             target,
 803             unwind,
 804             mergeable_succ,
 805         ) {
 806             return merging_succ;
 807         }
 808
 809         // The arguments we'll be passing. Plus one to account for outptr, if used.
 810         let arg_count = fn_abi.args.len() + fn_abi.ret.is_indirect() as usize;
 811         let mut llargs = Vec::with_capacity(arg_count);
 812
 813         // Prepare the return value destination
 814         let ret_dest = if target.is_some() {
 815             let is_intrinsic = intrinsic.is_some();
 816             self.make_return_dest(bx, destination, &fn_abi.ret, &mut llargs, is_intrinsic)
 817         } else {
 818             ReturnDest::Nothing
 819         };
 820
 821         if intrinsic == Some(sym::caller_location) {
 822             return if let Some(target) = target {
 823                 let location =
 824                     self.get_caller_location(bx, mir::SourceInfo { span: fn_span, ..source_info });
 825
 826                 if let ReturnDest::IndirectOperand(tmp, _) = ret_dest {
 827                     location.val.store(bx, tmp);
 828                 }
 829                 self.store_return(bx, ret_dest, &fn_abi.ret, location.immediate());
 830                 helper.funclet_br(self, bx, target, mergeable_succ)
 831             } else {
 832                 MergingSucc::False
 833             };
 834         }
 835
 836         match intrinsic {
 837             None | Some(sym::drop_in_place) => {}
 838             Some(intrinsic) => {
 839                 let dest = match ret_dest {
 840                     _ if fn_abi.ret.is_indirect() => llargs[0],
 841                     ReturnDest::Nothing => {
 842                         bx.const_undef(bx.type_ptr_to(bx.arg_memory_ty(&fn_abi.ret)))
 843                     }
 844                     ReturnDest::IndirectOperand(dst, _) | ReturnDest::Store(dst) => dst.llval,
 845                     ReturnDest::DirectOperand(_) => {
 846                         bug!("Cannot use direct operand with an intrinsic call")
 847                     }
 848                 };
 849
 850                 let args: Vec<_> = args
 851                     .iter()
 852                     .enumerate()
 853                     .map(|(i, arg)| {
 854                         // The indices passed to simd_shuffle* in the
 855                         // third argument must be constant. This is
 856                         // checked by const-qualification, which also
 857                         // promotes any complex rvalues to constants.
 858                         if i == 2 && intrinsic.as_str().starts_with("simd_shuffle") {
 859                             if let mir::Operand::Constant(constant) = arg {
 860                                 let c = self.eval_mir_constant(constant);
 861                                 let (llval, ty) = self.simd_shuffle_indices(
 862                                     &bx,
 863                                     constant.span,
 864                                     self.monomorphize(constant.ty()),
 865                                     c,
 866                                 );
 867                                 return OperandRef {
 868                                     val: Immediate(llval),
 869                                     layout: bx.layout_of(ty),
 870                                 };
 871                             } else {
 872                                 span_bug!(span, "shuffle indices must be constant");
 873                             }
 874                         }
 875
 876                         self.codegen_operand(bx, arg)
 877                     })
 878                     .collect();
 879
 880                 Self::codegen_intrinsic_call(
 881                     bx,
 882                     *instance.as_ref().unwrap(),
 883                     &fn_abi,
 884                     &args,
 885                     dest,
 886                     span,
 887                 );
 888
 889                 if let ReturnDest::IndirectOperand(dst, _) = ret_dest {
 890                     self.store_return(bx, ret_dest, &fn_abi.ret, dst.llval);
 891                 }
 892
 893                 return if let Some(target) = target {
 894                     helper.funclet_br(self, bx, target, mergeable_succ)
 895                 } else {
 896                     bx.unreachable();
 897                     MergingSucc::False
 898                 };
 899             }
 900         }
 901
 902         // Split the rust-call tupled arguments off.
 903         let (first_args, untuple) = if abi == Abi::RustCall && !args.is_empty() {
 904             let (tup, args) = args.split_last().unwrap();
 905             (args, Some(tup))
 906         } else {
 907             (args, None)
 908         };
 909
 910         let mut copied_constant_arguments = vec![];
 911         'make_args: for (i, arg) in first_args.iter().enumerate() {
 912             let mut op = self.codegen_operand(bx, arg);
 913
 914             if let (0, Some(ty::InstanceDef::Virtual(_, idx))) = (i, def) {
 915                 match op.val {
 916                     Pair(data_ptr, meta) => {
 917                         // In the case of Rc<Self>, we need to explicitly pass a
 918                         // *mut RcBox<Self> with a Scalar (not ScalarPair) ABI. This is a hack
 919                         // that is understood elsewhere in the compiler as a method on
 920                         // `dyn Trait`.
 921                         // To get a `*mut RcBox<Self>`, we just keep unwrapping newtypes until
 922                         // we get a value of a built-in pointer type.
 923                         //
 924                         // This is also relevant for `Pin<&mut Self>`, where we need to peel the `Pin`.
 925                         'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 926                             && !op.layout.ty.is_ref()
 927                         {
 928                             for i in 0..op.layout.fields.count() {
 929                                 let field = op.extract_field(bx, i);
 930                                 if !field.layout.is_zst() {
 931                                     // we found the one non-zero-sized field that is allowed
 932                                     // now find *its* non-zero-sized field, or stop if it's a
 933                                     // pointer
 934                                     op = field;
 935                                     continue 'descend_newtypes;
 936                                 }
 937                             }
 938
 939                             span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 940                         }
 941
 942                         // now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
 943                         // data pointer and vtable. Look up the method in the vtable, and pass
 944                         // the data pointer as the first argument
 945                         llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
 946                             bx,
 947                             meta,
 948                             op.layout.ty,
 949                             &fn_abi,
 950                         ));
 951                         llargs.push(data_ptr);
 952                         continue 'make_args;
 953                     }
 954                     Ref(data_ptr, Some(meta), _) => {
 955                         // by-value dynamic dispatch
 956                         llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
 957                             bx,
 958                             meta,
 959                             op.layout.ty,
 960                             &fn_abi,
 961                         ));
 962                         llargs.push(data_ptr);
 963                         continue;
 964                     }
 965                     Immediate(_) => {
 966                         // See comment above explaining why we peel these newtypes
 967                         'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
 968                             && !op.layout.ty.is_ref()
 969                         {
 970                             for i in 0..op.layout.fields.count() {
 971                                 let field = op.extract_field(bx, i);
 972                                 if !field.layout.is_zst() {
 973                                     // we found the one non-zero-sized field that is allowed
 974                                     // now find *its* non-zero-sized field, or stop if it's a
 975                                     // pointer
 976                                     op = field;
 977                                     continue 'descend_newtypes;
 978                                 }
 979                             }
 980
 981                             span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
 982                         }
 983
 984                         // Make sure that we've actually unwrapped the rcvr down
 985                         // to a pointer or ref to `dyn* Trait`.
 986                         if !op.layout.ty.builtin_deref(true).unwrap().ty.is_dyn_star() {
 987                             span_bug!(span, "can't codegen a virtual call on {:#?}", op);
 988                         }
 989                         let place = op.deref(bx.cx());
 990                         let data_ptr = place.project_field(bx, 0);
 991                         let meta_ptr = place.project_field(bx, 1);
 992                         let meta = bx.load_operand(meta_ptr);
 993                         llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
 994                             bx,
 995                             meta.immediate(),
 996                             op.layout.ty,
 997                             &fn_abi,
 998                         ));
 999                         llargs.push(data_ptr.llval);
1000                         continue;
1001                     }
1002                     _ => {
1003                         span_bug!(span, "can't codegen a virtual call on {:#?}", op);
1004                     }
1005                 }
1006             }
1007
1008             // The callee needs to own the argument memory if we pass it
1009             // by-ref, so make a local copy of non-immediate constants.
1010             match (arg, op.val) {
1011                 (&mir::Operand::Copy(_), Ref(_, None, _))
1012                 | (&mir::Operand::Constant(_), Ref(_, None, _)) => {
1013                     let tmp = PlaceRef::alloca(bx, op.layout);
1014                     bx.lifetime_start(tmp.llval, tmp.layout.size);
1015                     op.val.store(bx, tmp);
1016                     op.val = Ref(tmp.llval, None, tmp.align);
1017                     copied_constant_arguments.push(tmp);
1018                 }
1019                 _ => {}
1020             }
1021
1022             self.codegen_argument(bx, op, &mut llargs, &fn_abi.args[i]);
1023         }
1024         let num_untupled = untuple.map(|tup| {
1025             self.codegen_arguments_untupled(bx, tup, &mut llargs, &fn_abi.args[first_args.len()..])
1026         });
1027
1028         let needs_location =
1029             instance.map_or(false, |i| i.def.requires_caller_location(self.cx.tcx()));
1030         if needs_location {
1031             let mir_args = if let Some(num_untupled) = num_untupled {
1032                 first_args.len() + num_untupled
1033             } else {
1034                 args.len()
1035             };
1036             assert_eq!(
1037                 fn_abi.args.len(),
1038                 mir_args + 1,
1039                 "#[track_caller] fn's must have 1 more argument in their ABI than in their MIR: {:?} {:?} {:?}",
1040                 instance,
1041                 fn_span,
1042                 fn_abi,
1043             );
1044             let location =
1045                 self.get_caller_location(bx, mir::SourceInfo { span: fn_span, ..source_info });
1046             debug!(
1047                 "codegen_call_terminator({:?}): location={:?} (fn_span {:?})",
1048                 terminator, location, fn_span
1049             );
1050
1051             let last_arg = fn_abi.args.last().unwrap();
1052             self.codegen_argument(bx, location, &mut llargs, last_arg);
1053         }
1054
1055         let (is_indirect_call, fn_ptr) = match (llfn, instance) {
1056             (Some(llfn), _) => (true, llfn),
1057             (None, Some(instance)) => (false, bx.get_fn_addr(instance)),
1058             _ => span_bug!(span, "no llfn for call"),
1059         };
1060
1061         // For backends that support CFI using type membership (i.e., testing whether a given
1062         // pointer is associated with a type identifier).
1063         if bx.tcx().sess.is_sanitizer_cfi_enabled() && is_indirect_call {
1064             // Emit type metadata and checks.
1065             // FIXME(rcvalle): Add support for generalized identifiers.
1066             // FIXME(rcvalle): Create distinct unnamed MDNodes for internal identifiers.
1067             let typeid = typeid_for_fnabi(bx.tcx(), fn_abi);
1068             let typeid_metadata = self.cx.typeid_metadata(typeid);
1069
1070             // Test whether the function pointer is associated with the type identifier.
1071             let cond = bx.type_test(fn_ptr, typeid_metadata);
1072             let bb_pass = bx.append_sibling_block("type_test.pass");
1073             let bb_fail = bx.append_sibling_block("type_test.fail");
1074             bx.cond_br(cond, bb_pass, bb_fail);
1075
1076             bx.switch_to_block(bb_pass);
1077             let merging_succ = helper.do_call(
1078                 self,
1079                 bx,
1080                 fn_abi,
1081                 fn_ptr,
1082                 &llargs,
1083                 target.as_ref().map(|&target| (ret_dest, target)),
1084                 unwind,
1085                 &copied_constant_arguments,
1086                 false,
1087             );
1088             assert_eq!(merging_succ, MergingSucc::False);
1089
1090             bx.switch_to_block(bb_fail);
1091             bx.abort();
1092             bx.unreachable();
1093
1094             return MergingSucc::False;
1095         }
1096
1097         helper.do_call(
1098             self,
1099             bx,
1100             fn_abi,
1101             fn_ptr,
1102             &llargs,
1103             target.as_ref().map(|&target| (ret_dest, target)),
1104             unwind,
1105             &copied_constant_arguments,
1106             mergeable_succ,
1107         )
1108     }
1109
1110     fn codegen_asm_terminator(
1111         &mut self,
1112         helper: TerminatorCodegenHelper<'tcx>,
1113         bx: &mut Bx,
1114         terminator: &mir::Terminator<'tcx>,
1115         template: &[ast::InlineAsmTemplatePiece],
1116         operands: &[mir::InlineAsmOperand<'tcx>],
1117         options: ast::InlineAsmOptions,
1118         line_spans: &[Span],
1119         destination: Option<mir::BasicBlock>,
1120         unwind: mir::UnwindAction,
1121         instance: Instance<'_>,
1122         mergeable_succ: bool,
1123     ) -> MergingSucc {
1124         let span = terminator.source_info.span;
1125
1126         let operands: Vec<_> = operands
1127             .iter()
1128             .map(|op| match *op {
1129                 mir::InlineAsmOperand::In { reg, ref value } => {
1130                     let value = self.codegen_operand(bx, value);
1131                     InlineAsmOperandRef::In { reg, value }
1132                 }
1133                 mir::InlineAsmOperand::Out { reg, late, ref place } => {
1134                     let place = place.map(|place| self.codegen_place(bx, place.as_ref()));
1135                     InlineAsmOperandRef::Out { reg, late, place }
1136                 }
1137                 mir::InlineAsmOperand::InOut { reg, late, ref in_value, ref out_place } => {
1138                     let in_value = self.codegen_operand(bx, in_value);
1139                     let out_place =
1140                         out_place.map(|out_place| self.codegen_place(bx, out_place.as_ref()));
1141                     InlineAsmOperandRef::InOut { reg, late, in_value, out_place }
1142                 }
1143                 mir::InlineAsmOperand::Const { ref value } => {
1144                     let const_value = self
1145                         .eval_mir_constant(value)
1146                         .unwrap_or_else(|_| span_bug!(span, "asm const cannot be resolved"));
1147                     let string = common::asm_const_to_str(
1148                         bx.tcx(),
1149                         span,
1150                         const_value,
1151                         bx.layout_of(value.ty()),
1152                     );
1153                     InlineAsmOperandRef::Const { string }
1154                 }
1155                 mir::InlineAsmOperand::SymFn { ref value } => {
1156                     let literal = self.monomorphize(value.literal);
1157                     if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
1158                         let instance = ty::Instance::resolve_for_fn_ptr(
1159                             bx.tcx(),
1160                             ty::ParamEnv::reveal_all(),
1161                             def_id,
1162                             substs,
1163                         )
1164                         .unwrap();
1165                         InlineAsmOperandRef::SymFn { instance }
1166                     } else {
1167                         span_bug!(span, "invalid type for asm sym (fn)");
1168                     }
1169                 }
1170                 mir::InlineAsmOperand::SymStatic { def_id } => {
1171                     InlineAsmOperandRef::SymStatic { def_id }
1172                 }
1173             })
1174             .collect();
1175
1176         helper.do_inlineasm(
1177             self,
1178             bx,
1179             template,
1180             &operands,
1181             options,
1182             line_spans,
1183             destination,
1184             unwind,
1185             instance,
1186             mergeable_succ,
1187         )
1188     }
1189 }
1190
1191 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
1192     pub fn codegen_block(&mut self, mut bb: mir::BasicBlock) {
1193         let llbb = match self.try_llbb(bb) {
1194             Some(llbb) => llbb,
1195             None => return,
1196         };
1197         let bx = &mut Bx::build(self.cx, llbb);
1198         let mir = self.mir;
1199
1200         // MIR basic blocks stop at any function call. This may not be the case
1201         // for the backend's basic blocks, in which case we might be able to
1202         // combine multiple MIR basic blocks into a single backend basic block.
1203         loop {
1204             let data = &mir[bb];
1205
1206             debug!("codegen_block({:?}={:?})", bb, data);
1207
1208             for statement in &data.statements {
1209                 self.codegen_statement(bx, statement);
1210             }
1211
1212             let merging_succ = self.codegen_terminator(bx, bb, data.terminator());
1213             if let MergingSucc::False = merging_succ {
1214                 break;
1215             }
1216
1217             // We are merging the successor into the produced backend basic
1218             // block. Record that the successor should be skipped when it is
1219             // reached.
1220             //
1221             // Note: we must not have already generated code for the successor.
1222             // This is implicitly ensured by the reverse postorder traversal,
1223             // and the assertion explicitly guarantees that.
1224             let mut successors = data.terminator().successors();
1225             let succ = successors.next().unwrap();
1226             assert!(matches!(self.cached_llbbs[succ], CachedLlbb::None));
1227             self.cached_llbbs[succ] = CachedLlbb::Skip;
1228             bb = succ;
1229         }
1230     }
1231
1232     fn codegen_terminator(
1233         &mut self,
1234         bx: &mut Bx,
1235         bb: mir::BasicBlock,
1236         terminator: &'tcx mir::Terminator<'tcx>,
1237     ) -> MergingSucc {
1238         debug!("codegen_terminator: {:?}", terminator);
1239
1240         let helper = TerminatorCodegenHelper { bb, terminator };
1241
1242         let mergeable_succ = || {
1243             // Note: any call to `switch_to_block` will invalidate a `true` value
1244             // of `mergeable_succ`.
1245             let mut successors = terminator.successors();
1246             if let Some(succ) = successors.next()
1247                 && successors.next().is_none()
1248                 && let &[succ_pred] = self.mir.basic_blocks.predecessors()[succ].as_slice()
1249             {
1250                 // bb has a single successor, and bb is its only predecessor. This
1251                 // makes it a candidate for merging.
1252                 assert_eq!(succ_pred, bb);
1253                 true
1254             } else {
1255                 false
1256             }
1257         };
1258
1259         self.set_debug_loc(bx, terminator.source_info);
1260         match terminator.kind {
1261             mir::TerminatorKind::Resume => {
1262                 self.codegen_resume_terminator(helper, bx);
1263                 MergingSucc::False
1264             }
1265
1266             mir::TerminatorKind::Terminate => {
1267                 self.codegen_terminate_terminator(helper, bx, terminator);
1268                 MergingSucc::False
1269             }
1270
1271             mir::TerminatorKind::Goto { target } => {
1272                 helper.funclet_br(self, bx, target, mergeable_succ())
1273             }
1274
1275             mir::TerminatorKind::SwitchInt { ref discr, ref targets } => {
1276                 self.codegen_switchint_terminator(helper, bx, discr, targets);
1277                 MergingSucc::False
1278             }
1279
1280             mir::TerminatorKind::Return => {
1281                 self.codegen_return_terminator(bx);
1282                 MergingSucc::False
1283             }
1284
1285             mir::TerminatorKind::Unreachable => {
1286                 bx.unreachable();
1287                 MergingSucc::False
1288             }
1289
1290             mir::TerminatorKind::Drop { place, target, unwind } => {
1291                 self.codegen_drop_terminator(helper, bx, place, target, unwind, mergeable_succ())
1292             }
1293
1294             mir::TerminatorKind::Assert { ref cond, expected, ref msg, target, unwind } => self
1295                 .codegen_assert_terminator(
1296                     helper,
1297                     bx,
1298                     terminator,
1299                     cond,
1300                     expected,
1301                     msg,
1302                     target,
1303                     unwind,
1304                     mergeable_succ(),
1305                 ),
1306
1307             mir::TerminatorKind::Call {
1308                 ref func,
1309                 ref args,
1310                 destination,
1311                 target,
1312                 unwind,
1313                 from_hir_call: _,
1314                 fn_span,
1315             } => self.codegen_call_terminator(
1316                 helper,
1317                 bx,
1318                 terminator,
1319                 func,
1320                 args,
1321                 destination,
1322                 target,
1323                 unwind,
1324                 fn_span,
1325                 mergeable_succ(),
1326             ),
1327             mir::TerminatorKind::GeneratorDrop | mir::TerminatorKind::Yield { .. } => {
1328                 bug!("generator ops in codegen")
1329             }
1330             mir::TerminatorKind::FalseEdge { .. } | mir::TerminatorKind::FalseUnwind { .. } => {
1331                 bug!("borrowck false edges in codegen")
1332             }
1333
1334             mir::TerminatorKind::InlineAsm {
1335                 template,
1336                 ref operands,
1337                 options,
1338                 line_spans,
1339                 destination,
1340                 unwind,
1341             } => self.codegen_asm_terminator(
1342                 helper,
1343                 bx,
1344                 terminator,
1345                 template,
1346                 operands,
1347                 options,
1348                 line_spans,
1349                 destination,
1350                 unwind,
1351                 self.instance,
1352                 mergeable_succ(),
1353             ),
1354         }
1355     }
1356
1357     fn codegen_argument(
1358         &mut self,
1359         bx: &mut Bx,
1360         op: OperandRef<'tcx, Bx::Value>,
1361         llargs: &mut Vec<Bx::Value>,
1362         arg: &ArgAbi<'tcx, Ty<'tcx>>,
1363     ) {
1364         match arg.mode {
1365             PassMode::Ignore => return,
1366             PassMode::Cast(_, true) => {
1367                 // Fill padding with undef value, where applicable.
1368                 llargs.push(bx.const_undef(bx.reg_backend_type(&Reg::i32())));
1369             }
1370             PassMode::Pair(..) => match op.val {
1371                 Pair(a, b) => {
1372                     llargs.push(a);
1373                     llargs.push(b);
1374                     return;
1375                 }
1376                 _ => bug!("codegen_argument: {:?} invalid for pair argument", op),
1377             },
1378             PassMode::Indirect { attrs: _, extra_attrs: Some(_), on_stack: _ } => match op.val {
1379                 Ref(a, Some(b), _) => {
1380                     llargs.push(a);
1381                     llargs.push(b);
1382                     return;
1383                 }
1384                 _ => bug!("codegen_argument: {:?} invalid for unsized indirect argument", op),
1385             },
1386             _ => {}
1387         }
1388
1389         // Force by-ref if we have to load through a cast pointer.
1390         let (mut llval, align, by_ref) = match op.val {
1391             Immediate(_) | Pair(..) => match arg.mode {
1392                 PassMode::Indirect { .. } | PassMode::Cast(..) => {
1393                     let scratch = PlaceRef::alloca(bx, arg.layout);
1394                     op.val.store(bx, scratch);
1395                     (scratch.llval, scratch.align, true)
1396                 }
1397                 _ => (op.immediate_or_packed_pair(bx), arg.layout.align.abi, false),
1398             },
1399             Ref(llval, _, align) => {
1400                 if arg.is_indirect() && align < arg.layout.align.abi {
1401                     // `foo(packed.large_field)`. We can't pass the (unaligned) field directly. I
1402                     // think that ATM (Rust 1.16) we only pass temporaries, but we shouldn't
1403                     // have scary latent bugs around.
1404
1405                     let scratch = PlaceRef::alloca(bx, arg.layout);
1406                     base::memcpy_ty(
1407                         bx,
1408                         scratch.llval,
1409                         scratch.align,
1410                         llval,
1411                         align,
1412                         op.layout,
1413                         MemFlags::empty(),
1414                     );
1415                     (scratch.llval, scratch.align, true)
1416                 } else {
1417                     (llval, align, true)
1418                 }
1419             }
1420         };
1421
1422         if by_ref && !arg.is_indirect() {
1423             // Have to load the argument, maybe while casting it.
1424             if let PassMode::Cast(ty, _) = &arg.mode {
1425                 let llty = bx.cast_backend_type(ty);
1426                 let addr = bx.pointercast(llval, bx.type_ptr_to(llty));
1427                 llval = bx.load(llty, addr, align.min(arg.layout.align.abi));
1428             } else {
1429                 // We can't use `PlaceRef::load` here because the argument
1430                 // may have a type we don't treat as immediate, but the ABI
1431                 // used for this call is passing it by-value. In that case,
1432                 // the load would just produce `OperandValue::Ref` instead
1433                 // of the `OperandValue::Immediate` we need for the call.
1434                 llval = bx.load(bx.backend_type(arg.layout), llval, align);
1435                 if let abi::Abi::Scalar(scalar) = arg.layout.abi {
1436                     if scalar.is_bool() {
1437                         bx.range_metadata(llval, WrappingRange { start: 0, end: 1 });
1438                     }
1439                 }
1440                 // We store bools as `i8` so we need to truncate to `i1`.
1441                 llval = bx.to_immediate(llval, arg.layout);
1442             }
1443         }
1444
1445         llargs.push(llval);
1446     }
1447
1448     fn codegen_arguments_untupled(
1449         &mut self,
1450         bx: &mut Bx,
1451         operand: &mir::Operand<'tcx>,
1452         llargs: &mut Vec<Bx::Value>,
1453         args: &[ArgAbi<'tcx, Ty<'tcx>>],
1454     ) -> usize {
1455         let tuple = self.codegen_operand(bx, operand);
1456
1457         // Handle both by-ref and immediate tuples.
1458         if let Ref(llval, None, align) = tuple.val {
1459             let tuple_ptr = PlaceRef::new_sized_aligned(llval, tuple.layout, align);
1460             for i in 0..tuple.layout.fields.count() {
1461                 let field_ptr = tuple_ptr.project_field(bx, i);
1462                 let field = bx.load_operand(field_ptr);
1463                 self.codegen_argument(bx, field, llargs, &args[i]);
1464             }
1465         } else if let Ref(_, Some(_), _) = tuple.val {
1466             bug!("closure arguments must be sized")
1467         } else {
1468             // If the tuple is immediate, the elements are as well.
1469             for i in 0..tuple.layout.fields.count() {
1470                 let op = tuple.extract_field(bx, i);
1471                 self.codegen_argument(bx, op, llargs, &args[i]);
1472             }
1473         }
1474         tuple.layout.fields.count()
1475     }
1476
1477     fn get_caller_location(
1478         &mut self,
1479         bx: &mut Bx,
1480         mut source_info: mir::SourceInfo,
1481     ) -> OperandRef<'tcx, Bx::Value> {
1482         let tcx = bx.tcx();
1483
1484         let mut span_to_caller_location = |mut span: Span| {
1485             // Remove `Inlined` marks as they pollute `expansion_cause`.
1486             while span.is_inlined() {
1487                 span.remove_mark();
1488             }
1489             let topmost = span.ctxt().outer_expn().expansion_cause().unwrap_or(span);
1490             let caller = tcx.sess.source_map().lookup_char_pos(topmost.lo());
1491             let const_loc = tcx.const_caller_location((
1492                 Symbol::intern(&caller.file.name.prefer_remapped().to_string_lossy()),
1493                 caller.line as u32,
1494                 caller.col_display as u32 + 1,
1495             ));
1496             OperandRef::from_const(bx, const_loc, bx.tcx().caller_location_ty())
1497         };
1498
1499         // Walk up the `SourceScope`s, in case some of them are from MIR inlining.
1500         // If so, the starting `source_info.span` is in the innermost inlined
1501         // function, and will be replaced with outer callsite spans as long
1502         // as the inlined functions were `#[track_caller]`.
1503         loop {
1504             let scope_data = &self.mir.source_scopes[source_info.scope];
1505
1506             if let Some((callee, callsite_span)) = scope_data.inlined {
1507                 // Stop inside the most nested non-`#[track_caller]` function,
1508                 // before ever reaching its caller (which is irrelevant).
1509                 if !callee.def.requires_caller_location(tcx) {
1510                     return span_to_caller_location(source_info.span);
1511                 }
1512                 source_info.span = callsite_span;
1513             }
1514
1515             // Skip past all of the parents with `inlined: None`.
1516             match scope_data.inlined_parent_scope {
1517                 Some(parent) => source_info.scope = parent,
1518                 None => break,
1519             }
1520         }
1521
1522         // No inlined `SourceScope`s, or all of them were `#[track_caller]`.
1523         self.caller_location.unwrap_or_else(|| span_to_caller_location(source_info.span))
1524     }
1525
1526     fn get_personality_slot(&mut self, bx: &mut Bx) -> PlaceRef<'tcx, Bx::Value> {
1527         let cx = bx.cx();
1528         if let Some(slot) = self.personality_slot {
1529             slot
1530         } else {
1531             let layout = cx.layout_of(
1532                 cx.tcx().mk_tup(&[cx.tcx().mk_mut_ptr(cx.tcx().types.u8), cx.tcx().types.i32]),
1533             );
1534             let slot = PlaceRef::alloca(bx, layout);
1535             self.personality_slot = Some(slot);
1536             slot
1537         }
1538     }
1539
1540     /// Returns the landing/cleanup pad wrapper around the given basic block.
1541     // FIXME(eddyb) rename this to `eh_pad_for`.
1542     fn landing_pad_for(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1543         if let Some(landing_pad) = self.landing_pads[bb] {
1544             return landing_pad;
1545         }
1546
1547         let landing_pad = self.landing_pad_for_uncached(bb);
1548         self.landing_pads[bb] = Some(landing_pad);
1549         landing_pad
1550     }
1551
1552     // FIXME(eddyb) rename this to `eh_pad_for_uncached`.
1553     fn landing_pad_for_uncached(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1554         let llbb = self.llbb(bb);
1555         if base::wants_msvc_seh(self.cx.sess()) {
1556             let cleanup_bb = Bx::append_block(self.cx, self.llfn, &format!("funclet_{:?}", bb));
1557             let mut cleanup_bx = Bx::build(self.cx, cleanup_bb);
1558             let funclet = cleanup_bx.cleanup_pad(None, &[]);
1559             cleanup_bx.br(llbb);
1560             self.funclets[bb] = Some(funclet);
1561             cleanup_bb
1562         } else {
1563             let cleanup_llbb = Bx::append_block(self.cx, self.llfn, "cleanup");
1564             let mut cleanup_bx = Bx::build(self.cx, cleanup_llbb);
1565
1566             let llpersonality = self.cx.eh_personality();
1567             let (exn0, exn1) = cleanup_bx.cleanup_landing_pad(llpersonality);
1568
1569             let slot = self.get_personality_slot(&mut cleanup_bx);
1570             slot.storage_live(&mut cleanup_bx);
1571             Pair(exn0, exn1).store(&mut cleanup_bx, slot);
1572
1573             cleanup_bx.br(llbb);
1574             cleanup_llbb
1575         }
1576     }
1577
1578     fn unreachable_block(&mut self) -> Bx::BasicBlock {
1579         self.unreachable_block.unwrap_or_else(|| {
1580             let llbb = Bx::append_block(self.cx, self.llfn, "unreachable");
1581             let mut bx = Bx::build(self.cx, llbb);
1582             bx.unreachable();
1583             self.unreachable_block = Some(llbb);
1584             llbb
1585         })
1586     }
1587
1588     fn terminate_block(&mut self) -> Bx::BasicBlock {
1589         self.terminate_block.unwrap_or_else(|| {
1590             let funclet;
1591             let llbb;
1592             let mut bx;
1593             if base::wants_msvc_seh(self.cx.sess()) {
1594                 // This is a basic block that we're aborting the program for,
1595                 // notably in an `extern` function. These basic blocks are inserted
1596                 // so that we assert that `extern` functions do indeed not panic,
1597                 // and if they do we abort the process.
1598                 //
1599                 // On MSVC these are tricky though (where we're doing funclets). If
1600                 // we were to do a cleanuppad (like below) the normal functions like
1601                 // `longjmp` would trigger the abort logic, terminating the
1602                 // program. Instead we insert the equivalent of `catch(...)` for C++
1603                 // which magically doesn't trigger when `longjmp` files over this
1604                 // frame.
1605                 //
1606                 // Lots more discussion can be found on #48251 but this codegen is
1607                 // modeled after clang's for:
1608                 //
1609                 //      try {
1610                 //          foo();
1611                 //      } catch (...) {
1612                 //          bar();
1613                 //      }
1614                 llbb = Bx::append_block(self.cx, self.llfn, "cs_terminate");
1615                 let cp_llbb = Bx::append_block(self.cx, self.llfn, "cp_terminate");
1616
1617                 let mut cs_bx = Bx::build(self.cx, llbb);
1618                 let cs = cs_bx.catch_switch(None, None, &[cp_llbb]);
1619
1620                 // The "null" here is actually a RTTI type descriptor for the
1621                 // C++ personality function, but `catch (...)` has no type so
1622                 // it's null. The 64 here is actually a bitfield which
1623                 // represents that this is a catch-all block.
1624                 bx = Bx::build(self.cx, cp_llbb);
1625                 let null =
1626                     bx.const_null(bx.type_i8p_ext(bx.cx().data_layout().instruction_address_space));
1627                 let sixty_four = bx.const_i32(64);
1628                 funclet = Some(bx.catch_pad(cs, &[null, sixty_four, null]));
1629             } else {
1630                 llbb = Bx::append_block(self.cx, self.llfn, "terminate");
1631                 bx = Bx::build(self.cx, llbb);
1632
1633                 let llpersonality = self.cx.eh_personality();
1634                 bx.cleanup_landing_pad(llpersonality);
1635
1636                 funclet = None;
1637             }
1638
1639             self.set_debug_loc(&mut bx, mir::SourceInfo::outermost(self.mir.span));
1640
1641             let (fn_abi, fn_ptr) = common::build_langcall(&bx, None, LangItem::PanicCannotUnwind);
1642             let fn_ty = bx.fn_decl_backend_type(&fn_abi);
1643
1644             let llret = bx.call(fn_ty, Some(&fn_abi), fn_ptr, &[], funclet.as_ref());
1645             bx.do_not_inline(llret);
1646
1647             bx.unreachable();
1648
1649             self.terminate_block = Some(llbb);
1650             llbb
1651         })
1652     }
1653
1654     /// Get the backend `BasicBlock` for a MIR `BasicBlock`, either already
1655     /// cached in `self.cached_llbbs`, or created on demand (and cached).
1656     // FIXME(eddyb) rename `llbb` and other `ll`-prefixed things to use a
1657     // more backend-agnostic prefix such as `cg` (i.e. this would be `cgbb`).
1658     pub fn llbb(&mut self, bb: mir::BasicBlock) -> Bx::BasicBlock {
1659         self.try_llbb(bb).unwrap()
1660     }
1661
1662     /// Like `llbb`, but may fail if the basic block should be skipped.
1663     pub fn try_llbb(&mut self, bb: mir::BasicBlock) -> Option<Bx::BasicBlock> {
1664         match self.cached_llbbs[bb] {
1665             CachedLlbb::None => {
1666                 // FIXME(eddyb) only name the block if `fewer_names` is `false`.
1667                 let llbb = Bx::append_block(self.cx, self.llfn, &format!("{:?}", bb));
1668                 self.cached_llbbs[bb] = CachedLlbb::Some(llbb);
1669                 Some(llbb)
1670             }
1671             CachedLlbb::Some(llbb) => Some(llbb),
1672             CachedLlbb::Skip => None,
1673         }
1674     }
1675
1676     fn make_return_dest(
1677         &mut self,
1678         bx: &mut Bx,
1679         dest: mir::Place<'tcx>,
1680         fn_ret: &ArgAbi<'tcx, Ty<'tcx>>,
1681         llargs: &mut Vec<Bx::Value>,
1682         is_intrinsic: bool,
1683     ) -> ReturnDest<'tcx, Bx::Value> {
1684         // If the return is ignored, we can just return a do-nothing `ReturnDest`.
1685         if fn_ret.is_ignore() {
1686             return ReturnDest::Nothing;
1687         }
1688         let dest = if let Some(index) = dest.as_local() {
1689             match self.locals[index] {
1690                 LocalRef::Place(dest) => dest,
1691                 LocalRef::UnsizedPlace(_) => bug!("return type must be sized"),
1692                 LocalRef::PendingOperand => {
1693                     // Handle temporary places, specifically `Operand` ones, as
1694                     // they don't have `alloca`s.
1695                     return if fn_ret.is_indirect() {
1696                         // Odd, but possible, case, we have an operand temporary,
1697                         // but the calling convention has an indirect return.
1698                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1699                         tmp.storage_live(bx);
1700                         llargs.push(tmp.llval);
1701                         ReturnDest::IndirectOperand(tmp, index)
1702                     } else if is_intrinsic {
1703                         // Currently, intrinsics always need a location to store
1704                         // the result, so we create a temporary `alloca` for the
1705                         // result.
1706                         let tmp = PlaceRef::alloca(bx, fn_ret.layout);
1707                         tmp.storage_live(bx);
1708                         ReturnDest::IndirectOperand(tmp, index)
1709                     } else {
1710                         ReturnDest::DirectOperand(index)
1711                     };
1712                 }
1713                 LocalRef::Operand(_) => {
1714                     bug!("place local already assigned to");
1715                 }
1716             }
1717         } else {
1718             self.codegen_place(
1719                 bx,
1720                 mir::PlaceRef { local: dest.local, projection: &dest.projection },
1721             )
1722         };
1723         if fn_ret.is_indirect() {
1724             if dest.align < dest.layout.align.abi {
1725                 // Currently, MIR code generation does not create calls
1726                 // that store directly to fields of packed structs (in
1727                 // fact, the calls it creates write only to temps).
1728                 //
1729                 // If someone changes that, please update this code path
1730                 // to create a temporary.
1731                 span_bug!(self.mir.span, "can't directly store to unaligned value");
1732             }
1733             llargs.push(dest.llval);
1734             ReturnDest::Nothing
1735         } else {
1736             ReturnDest::Store(dest)
1737         }
1738     }
1739
1740     // Stores the return value of a function call into it's final location.
1741     fn store_return(
1742         &mut self,
1743         bx: &mut Bx,
1744         dest: ReturnDest<'tcx, Bx::Value>,
1745         ret_abi: &ArgAbi<'tcx, Ty<'tcx>>,
1746         llval: Bx::Value,
1747     ) {
1748         use self::ReturnDest::*;
1749
1750         match dest {
1751             Nothing => (),
1752             Store(dst) => bx.store_arg(&ret_abi, llval, dst),
1753             IndirectOperand(tmp, index) => {
1754                 let op = bx.load_operand(tmp);
1755                 tmp.storage_dead(bx);
1756                 self.locals[index] = LocalRef::Operand(op);
1757                 self.debug_introduce_local(bx, index);
1758             }
1759             DirectOperand(index) => {
1760                 // If there is a cast, we have to store and reload.
1761                 let op = if let PassMode::Cast(..) = ret_abi.mode {
1762                     let tmp = PlaceRef::alloca(bx, ret_abi.layout);
1763                     tmp.storage_live(bx);
1764                     bx.store_arg(&ret_abi, llval, tmp);
1765                     let op = bx.load_operand(tmp);
1766                     tmp.storage_dead(bx);
1767                     op
1768                 } else {
1769                     OperandRef::from_immediate_or_packed_pair(bx, llval, ret_abi.layout)
1770                 };
1771                 self.locals[index] = LocalRef::Operand(op);
1772                 self.debug_introduce_local(bx, index);
1773             }
1774         }
1775     }
1776 }
1777
1778 enum ReturnDest<'tcx, V> {
1779     // Do nothing; the return value is indirect or ignored.
1780     Nothing,
1781     // Store the return value to the pointer.
1782     Store(PlaceRef<'tcx, V>),
1783     // Store an indirect return value to an operand local place.
1784     IndirectOperand(PlaceRef<'tcx, V>, mir::Local),
1785     // Store a direct return value to an operand local place.
1786     DirectOperand(mir::Local),
1787 }