compiler/rustc_const_eval/src/interpret/terminator.rs

   1 use std::borrow::Cow;
   2
   3 use rustc_ast::ast::InlineAsmOptions;
   4 use rustc_middle::ty::layout::{FnAbiOf, LayoutOf};
   5 use rustc_middle::ty::Instance;
   6 use rustc_middle::{
   7     mir,
   8     ty::{self, Ty},
   9 };
  10 use rustc_target::abi;
  11 use rustc_target::abi::call::{ArgAbi, ArgAttribute, ArgAttributes, FnAbi, PassMode};
  12 use rustc_target::spec::abi::Abi;
  13
  14 use super::{
  15     FnVal, ImmTy, Immediate, InterpCx, InterpResult, MPlaceTy, Machine, MemoryKind, OpTy, Operand,
  16     PlaceTy, Scalar, StackPopCleanup, StackPopUnwind,
  17 };
  18
  19 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  20     pub(super) fn eval_terminator(
  21         &mut self,
  22         terminator: &mir::Terminator<'tcx>,
  23     ) -> InterpResult<'tcx> {
  24         use rustc_middle::mir::TerminatorKind::*;
  25         match terminator.kind {
  26             Return => {
  27                 self.pop_stack_frame(/* unwinding */ false)?
  28             }
  29
  30             Goto { target } => self.go_to_block(target),
  31
  32             SwitchInt { ref discr, ref targets, switch_ty } => {
  33                 let discr = self.read_immediate(&self.eval_operand(discr, None)?)?;
  34                 trace!("SwitchInt({:?})", *discr);
  35                 assert_eq!(discr.layout.ty, switch_ty);
  36
  37                 // Branch to the `otherwise` case by default, if no match is found.
  38                 assert!(!targets.iter().is_empty());
  39                 let mut target_block = targets.otherwise();
  40
  41                 for (const_int, target) in targets.iter() {
  42                     // Compare using MIR BinOp::Eq, to also support pointer values.
  43                     // (Avoiding `self.binary_op` as that does some redundant layout computation.)
  44                     let res = self
  45                         .overflowing_binary_op(
  46                             mir::BinOp::Eq,
  47                             &discr,
  48                             &ImmTy::from_uint(const_int, discr.layout),
  49                         )?
  50                         .0;
  51                     if res.to_bool()? {
  52                         target_block = target;
  53                         break;
  54                     }
  55                 }
  56
  57                 self.go_to_block(target_block);
  58             }
  59
  60             Call {
  61                 ref func,
  62                 ref args,
  63                 destination,
  64                 target,
  65                 ref cleanup,
  66                 from_hir_call: _,
  67                 fn_span: _,
  68             } => {
  69                 let old_stack = self.frame_idx();
  70                 let old_loc = self.frame().loc;
  71                 let func = self.eval_operand(func, None)?;
  72                 let args = self.eval_operands(args)?;
  73
  74                 let fn_sig_binder = func.layout.ty.fn_sig(*self.tcx);
  75                 let fn_sig =
  76                     self.tcx.normalize_erasing_late_bound_regions(self.param_env, fn_sig_binder);
  77                 let extra_args = &args[fn_sig.inputs().len()..];
  78                 let extra_args = self.tcx.mk_type_list(extra_args.iter().map(|arg| arg.layout.ty));
  79
  80                 let (fn_val, fn_abi, with_caller_location) = match *func.layout.ty.kind() {
  81                     ty::FnPtr(_sig) => {
  82                         let fn_ptr = self.read_pointer(&func)?;
  83                         let fn_val = self.get_ptr_fn(fn_ptr)?;
  84                         (fn_val, self.fn_abi_of_fn_ptr(fn_sig_binder, extra_args)?, false)
  85                     }
  86                     ty::FnDef(def_id, substs) => {
  87                         let instance =
  88                             self.resolve(ty::WithOptConstParam::unknown(def_id), substs)?;
  89                         (
  90                             FnVal::Instance(instance),
  91                             self.fn_abi_of_instance(instance, extra_args)?,
  92                             instance.def.requires_caller_location(*self.tcx),
  93                         )
  94                     }
  95                     _ => span_bug!(
  96                         terminator.source_info.span,
  97                         "invalid callee of type {:?}",
  98                         func.layout.ty
  99                     ),
 100                 };
 101
 102                 let destination = self.eval_place(destination)?;
 103                 self.eval_fn_call(
 104                     fn_val,
 105                     (fn_sig.abi, fn_abi),
 106                     &args,
 107                     with_caller_location,
 108                     &destination,
 109                     target,
 110                     match (cleanup, fn_abi.can_unwind) {
 111                         (Some(cleanup), true) => StackPopUnwind::Cleanup(*cleanup),
 112                         (None, true) => StackPopUnwind::Skip,
 113                         (_, false) => StackPopUnwind::NotAllowed,
 114                     },
 115                 )?;
 116                 // Sanity-check that `eval_fn_call` either pushed a new frame or
 117                 // did a jump to another block.
 118                 if self.frame_idx() == old_stack && self.frame().loc == old_loc {
 119                     span_bug!(terminator.source_info.span, "evaluating this call made no progress");
 120                 }
 121             }
 122
 123             Drop { place, target, unwind } => {
 124                 let place = self.eval_place(place)?;
 125                 let ty = place.layout.ty;
 126                 trace!("TerminatorKind::drop: {:?}, type {}", place, ty);
 127
 128                 let instance = Instance::resolve_drop_in_place(*self.tcx, ty);
 129                 self.drop_in_place(&place, instance, target, unwind)?;
 130             }
 131
 132             Assert { ref cond, expected, ref msg, target, cleanup } => {
 133                 let cond_val = self.read_scalar(&self.eval_operand(cond, None)?)?.to_bool()?;
 134                 if expected == cond_val {
 135                     self.go_to_block(target);
 136                 } else {
 137                     M::assert_panic(self, msg, cleanup)?;
 138                 }
 139             }
 140
 141             Abort => {
 142                 M::abort(self, "the program aborted execution".to_owned())?;
 143             }
 144
 145             // When we encounter Resume, we've finished unwinding
 146             // cleanup for the current stack frame. We pop it in order
 147             // to continue unwinding the next frame
 148             Resume => {
 149                 trace!("unwinding: resuming from cleanup");
 150                 // By definition, a Resume terminator means
 151                 // that we're unwinding
 152                 self.pop_stack_frame(/* unwinding */ true)?;
 153                 return Ok(());
 154             }
 155
 156             // It is UB to ever encounter this.
 157             Unreachable => throw_ub!(Unreachable),
 158
 159             // These should never occur for MIR we actually run.
 160             DropAndReplace { .. }
 161             | FalseEdge { .. }
 162             | FalseUnwind { .. }
 163             | Yield { .. }
 164             | GeneratorDrop => span_bug!(
 165                 terminator.source_info.span,
 166                 "{:#?} should have been eliminated by MIR pass",
 167                 terminator.kind
 168             ),
 169
 170             InlineAsm { template, ref operands, options, destination, .. } => {
 171                 M::eval_inline_asm(self, template, operands, options)?;
 172                 if options.contains(InlineAsmOptions::NORETURN) {
 173                     throw_ub_format!("returned from noreturn inline assembly");
 174                 }
 175                 self.go_to_block(
 176                     destination
 177                         .expect("InlineAsm terminators without noreturn must have a destination"),
 178                 )
 179             }
 180         }
 181
 182         Ok(())
 183     }
 184
 185     fn check_argument_compat(
 186         caller_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 187         callee_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 188     ) -> bool {
 189         // Heuristic for type comparison.
 190         let layout_compat = || {
 191             if caller_abi.layout.ty == callee_abi.layout.ty {
 192                 // No question
 193                 return true;
 194             }
 195             if caller_abi.layout.is_unsized() || callee_abi.layout.is_unsized() {
 196                 // No, no, no. We require the types to *exactly* match for unsized arguments. If
 197                 // these are somehow unsized "in a different way" (say, `dyn Trait` vs `[i32]`),
 198                 // then who knows what happens.
 199                 return false;
 200             }
 201             if caller_abi.layout.size != callee_abi.layout.size
 202                 || caller_abi.layout.align.abi != callee_abi.layout.align.abi
 203             {
 204                 // This cannot go well...
 205                 return false;
 206             }
 207             // The rest *should* be okay, but we are extra conservative.
 208             match (caller_abi.layout.abi, callee_abi.layout.abi) {
 209                 // Different valid ranges are okay (once we enforce validity,
 210                 // that will take care to make it UB to leave the range, just
 211                 // like for transmute).
 212                 (abi::Abi::Scalar(caller), abi::Abi::Scalar(callee)) => {
 213                     caller.primitive() == callee.primitive()
 214                 }
 215                 (
 216                     abi::Abi::ScalarPair(caller1, caller2),
 217                     abi::Abi::ScalarPair(callee1, callee2),
 218                 ) => {
 219                     caller1.primitive() == callee1.primitive()
 220                         && caller2.primitive() == callee2.primitive()
 221                 }
 222                 // Be conservative
 223                 _ => false,
 224             }
 225         };
 226         // When comparing the PassMode, we have to be smart about comparing the attributes.
 227         let arg_attr_compat = |a1: &ArgAttributes, a2: &ArgAttributes| {
 228             // There's only one regular attribute that matters for the call ABI: InReg.
 229             // Everything else is things like noalias, dereferenceable, nonnull, ...
 230             // (This also applies to pointee_size, pointee_align.)
 231             if a1.regular.contains(ArgAttribute::InReg) != a2.regular.contains(ArgAttribute::InReg)
 232             {
 233                 return false;
 234             }
 235             // We also compare the sign extension mode -- this could let the callee make assumptions
 236             // about bits that conceptually were not even passed.
 237             if a1.arg_ext != a2.arg_ext {
 238                 return false;
 239             }
 240             return true;
 241         };
 242         let mode_compat = || match (&caller_abi.mode, &callee_abi.mode) {
 243             (PassMode::Ignore, PassMode::Ignore) => true,
 244             (PassMode::Direct(a1), PassMode::Direct(a2)) => arg_attr_compat(a1, a2),
 245             (PassMode::Pair(a1, b1), PassMode::Pair(a2, b2)) => {
 246                 arg_attr_compat(a1, a2) && arg_attr_compat(b1, b2)
 247             }
 248             (PassMode::Cast(c1, pad1), PassMode::Cast(c2, pad2)) => c1 == c2 && pad1 == pad2,
 249             (
 250                 PassMode::Indirect { attrs: a1, extra_attrs: None, on_stack: s1 },
 251                 PassMode::Indirect { attrs: a2, extra_attrs: None, on_stack: s2 },
 252             ) => arg_attr_compat(a1, a2) && s1 == s2,
 253             (
 254                 PassMode::Indirect { attrs: a1, extra_attrs: Some(e1), on_stack: s1 },
 255                 PassMode::Indirect { attrs: a2, extra_attrs: Some(e2), on_stack: s2 },
 256             ) => arg_attr_compat(a1, a2) && arg_attr_compat(e1, e2) && s1 == s2,
 257             _ => false,
 258         };
 259
 260         if layout_compat() && mode_compat() {
 261             return true;
 262         }
 263         trace!(
 264             "check_argument_compat: incompatible ABIs:\ncaller: {:?}\ncallee: {:?}",
 265             caller_abi,
 266             callee_abi
 267         );
 268         return false;
 269     }
 270
 271     /// Initialize a single callee argument, checking the types for compatibility.
 272     fn pass_argument<'x, 'y>(
 273         &mut self,
 274         caller_args: &mut impl Iterator<
 275             Item = (&'x OpTy<'tcx, M::Provenance>, &'y ArgAbi<'tcx, Ty<'tcx>>),
 276         >,
 277         callee_abi: &ArgAbi<'tcx, Ty<'tcx>>,
 278         callee_arg: &PlaceTy<'tcx, M::Provenance>,
 279     ) -> InterpResult<'tcx>
 280     where
 281         'tcx: 'x,
 282         'tcx: 'y,
 283     {
 284         if matches!(callee_abi.mode, PassMode::Ignore) {
 285             // This one is skipped.
 286             return Ok(());
 287         }
 288         // Find next caller arg.
 289         let (caller_arg, caller_abi) = caller_args.next().ok_or_else(|| {
 290             err_ub_format!("calling a function with fewer arguments than it requires")
 291         })?;
 292         // Now, check
 293         if !Self::check_argument_compat(caller_abi, callee_abi) {
 294             throw_ub_format!(
 295                 "calling a function with argument of type {:?} passing data of type {:?}",
 296                 callee_arg.layout.ty,
 297                 caller_arg.layout.ty
 298             )
 299         }
 300         // Special handling for unsized parameters.
 301         if caller_arg.layout.is_unsized() {
 302             // `check_argument_compat` ensures that both have the same type, so we know they will use the metadata the same way.
 303             assert_eq!(caller_arg.layout.ty, callee_arg.layout.ty);
 304             // We have to properly pre-allocate the memory for the callee.
 305             // So let's tear down some wrappers.
 306             // This all has to be in memory, there are no immediate unsized values.
 307             let src = caller_arg.assert_mem_place();
 308             // The destination cannot be one of these "spread args".
 309             let (dest_frame, dest_local) = callee_arg.assert_local();
 310             // We are just initializing things, so there can't be anything here yet.
 311             assert!(matches!(
 312                 *self.local_to_op(&self.stack()[dest_frame], dest_local, None)?,
 313                 Operand::Immediate(Immediate::Uninit)
 314             ));
 315             // Allocate enough memory to hold `src`.
 316             let Some((size, align)) = self.size_and_align_of_mplace(&src)? else {
 317                 span_bug!(self.cur_span(), "unsized fn arg with `extern` type tail should not be allowed")
 318             };
 319             let ptr = self.allocate_ptr(size, align, MemoryKind::Stack)?;
 320             let dest_place =
 321                 MPlaceTy::from_aligned_ptr_with_meta(ptr.into(), callee_arg.layout, src.meta);
 322             // Update the local to be that new place.
 323             *M::access_local_mut(self, dest_frame, dest_local)? = Operand::Indirect(*dest_place);
 324         }
 325         // We allow some transmutes here.
 326         // FIXME: Depending on the PassMode, this should reset some padding to uninitialized. (This
 327         // is true for all `copy_op`, but there are a lot of special cases for argument passing
 328         // specifically.)
 329         self.copy_op(&caller_arg, callee_arg, /*allow_transmute*/ true)
 330     }
 331
 332     /// Call this function -- pushing the stack frame and initializing the arguments.
 333     ///
 334     /// `caller_fn_abi` is used to determine if all the arguments are passed the proper way.
 335     /// However, we also need `caller_abi` to determine if we need to do untupling of arguments.
 336     ///
 337     /// `with_caller_location` indicates whether the caller passed a caller location. Miri
 338     /// implements caller locations without argument passing, but to match `FnAbi` we need to know
 339     /// when those arguments are present.
 340     pub(crate) fn eval_fn_call(
 341         &mut self,
 342         fn_val: FnVal<'tcx, M::ExtraFnVal>,
 343         (caller_abi, caller_fn_abi): (Abi, &FnAbi<'tcx, Ty<'tcx>>),
 344         args: &[OpTy<'tcx, M::Provenance>],
 345         with_caller_location: bool,
 346         destination: &PlaceTy<'tcx, M::Provenance>,
 347         target: Option<mir::BasicBlock>,
 348         mut unwind: StackPopUnwind,
 349     ) -> InterpResult<'tcx> {
 350         trace!("eval_fn_call: {:#?}", fn_val);
 351
 352         let instance = match fn_val {
 353             FnVal::Instance(instance) => instance,
 354             FnVal::Other(extra) => {
 355                 return M::call_extra_fn(
 356                     self,
 357                     extra,
 358                     caller_abi,
 359                     args,
 360                     destination,
 361                     target,
 362                     unwind,
 363                 );
 364             }
 365         };
 366
 367         match instance.def {
 368             ty::InstanceDef::Intrinsic(def_id) => {
 369                 assert!(self.tcx.is_intrinsic(def_id));
 370                 // caller_fn_abi is not relevant here, we interpret the arguments directly for each intrinsic.
 371                 M::call_intrinsic(self, instance, args, destination, target, unwind)
 372             }
 373             ty::InstanceDef::VTableShim(..)
 374             | ty::InstanceDef::ReifyShim(..)
 375             | ty::InstanceDef::ClosureOnceShim { .. }
 376             | ty::InstanceDef::FnPtrShim(..)
 377             | ty::InstanceDef::DropGlue(..)
 378             | ty::InstanceDef::CloneShim(..)
 379             | ty::InstanceDef::Item(_) => {
 380                 // We need MIR for this fn
 381                 let Some((body, instance)) =
 382                     M::find_mir_or_eval_fn(self, instance, caller_abi, args, destination, target, unwind)? else {
 383                         return Ok(());
 384                     };
 385
 386                 // Compute callee information using the `instance` returned by
 387                 // `find_mir_or_eval_fn`.
 388                 // FIXME: for variadic support, do we have to somehow determine callee's extra_args?
 389                 let callee_fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
 390
 391                 if callee_fn_abi.c_variadic || caller_fn_abi.c_variadic {
 392                     throw_unsup_format!("calling a c-variadic function is not supported");
 393                 }
 394
 395                 if M::enforce_abi(self) {
 396                     if caller_fn_abi.conv != callee_fn_abi.conv {
 397                         throw_ub_format!(
 398                             "calling a function with calling convention {:?} using calling convention {:?}",
 399                             callee_fn_abi.conv,
 400                             caller_fn_abi.conv
 401                         )
 402                     }
 403                 }
 404
 405                 if !matches!(unwind, StackPopUnwind::NotAllowed) && !callee_fn_abi.can_unwind {
 406                     // The callee cannot unwind.
 407                     unwind = StackPopUnwind::NotAllowed;
 408                 }
 409
 410                 self.push_stack_frame(
 411                     instance,
 412                     body,
 413                     destination,
 414                     StackPopCleanup::Goto { ret: target, unwind },
 415                 )?;
 416
 417                 // If an error is raised here, pop the frame again to get an accurate backtrace.
 418                 // To this end, we wrap it all in a `try` block.
 419                 let res: InterpResult<'tcx> = try {
 420                     trace!(
 421                         "caller ABI: {:?}, args: {:#?}",
 422                         caller_abi,
 423                         args.iter()
 424                             .map(|arg| (arg.layout.ty, format!("{:?}", **arg)))
 425                             .collect::<Vec<_>>()
 426                     );
 427                     trace!(
 428                         "spread_arg: {:?}, locals: {:#?}",
 429                         body.spread_arg,
 430                         body.args_iter()
 431                             .map(|local| (
 432                                 local,
 433                                 self.layout_of_local(self.frame(), local, None).unwrap().ty
 434                             ))
 435                             .collect::<Vec<_>>()
 436                     );
 437
 438                     // In principle, we have two iterators: Where the arguments come from, and where
 439                     // they go to.
 440
 441                     // For where they come from: If the ABI is RustCall, we untuple the
 442                     // last incoming argument.  These two iterators do not have the same type,
 443                     // so to keep the code paths uniform we accept an allocation
 444                     // (for RustCall ABI only).
 445                     let caller_args: Cow<'_, [OpTy<'tcx, M::Provenance>]> =
 446                         if caller_abi == Abi::RustCall && !args.is_empty() {
 447                             // Untuple
 448                             let (untuple_arg, args) = args.split_last().unwrap();
 449                             trace!("eval_fn_call: Will pass last argument by untupling");
 450                             Cow::from(
 451                                 args.iter()
 452                                     .map(|a| Ok(a.clone()))
 453                                     .chain(
 454                                         (0..untuple_arg.layout.fields.count())
 455                                             .map(|i| self.operand_field(untuple_arg, i)),
 456                                     )
 457                                     .collect::<InterpResult<'_, Vec<OpTy<'tcx, M::Provenance>>>>(
 458                                     )?,
 459                             )
 460                         } else {
 461                             // Plain arg passing
 462                             Cow::from(args)
 463                         };
 464                     // If `with_caller_location` is set we pretend there is an extra argument (that
 465                     // we will not pass).
 466                     assert_eq!(
 467                         caller_args.len() + if with_caller_location { 1 } else { 0 },
 468                         caller_fn_abi.args.len(),
 469                         "mismatch between caller ABI and caller arguments",
 470                     );
 471                     let mut caller_args = caller_args
 472                         .iter()
 473                         .zip(caller_fn_abi.args.iter())
 474                         .filter(|arg_and_abi| !matches!(arg_and_abi.1.mode, PassMode::Ignore));
 475
 476                     // Now we have to spread them out across the callee's locals,
 477                     // taking into account the `spread_arg`.  If we could write
 478                     // this is a single iterator (that handles `spread_arg`), then
 479                     // `pass_argument` would be the loop body. It takes care to
 480                     // not advance `caller_iter` for ZSTs.
 481                     let mut callee_args_abis = callee_fn_abi.args.iter();
 482                     for local in body.args_iter() {
 483                         let dest = self.eval_place(mir::Place::from(local))?;
 484                         if Some(local) == body.spread_arg {
 485                             // Must be a tuple
 486                             for i in 0..dest.layout.fields.count() {
 487                                 let dest = self.place_field(&dest, i)?;
 488                                 let callee_abi = callee_args_abis.next().unwrap();
 489                                 self.pass_argument(&mut caller_args, callee_abi, &dest)?;
 490                             }
 491                         } else {
 492                             // Normal argument
 493                             let callee_abi = callee_args_abis.next().unwrap();
 494                             self.pass_argument(&mut caller_args, callee_abi, &dest)?;
 495                         }
 496                     }
 497                     // If the callee needs a caller location, pretend we consume one more argument from the ABI.
 498                     if instance.def.requires_caller_location(*self.tcx) {
 499                         callee_args_abis.next().unwrap();
 500                     }
 501                     // Now we should have no more caller args or callee arg ABIs
 502                     assert!(
 503                         callee_args_abis.next().is_none(),
 504                         "mismatch between callee ABI and callee body arguments"
 505                     );
 506                     if caller_args.next().is_some() {
 507                         throw_ub_format!("calling a function with more arguments than it expected")
 508                     }
 509                     // Don't forget to check the return type!
 510                     if !Self::check_argument_compat(&caller_fn_abi.ret, &callee_fn_abi.ret) {
 511                         throw_ub_format!(
 512                             "calling a function with return type {:?} passing \
 513                                     return place of type {:?}",
 514                             callee_fn_abi.ret.layout.ty,
 515                             caller_fn_abi.ret.layout.ty,
 516                         )
 517                     }
 518                 };
 519                 match res {
 520                     Err(err) => {
 521                         self.stack_mut().pop();
 522                         Err(err)
 523                     }
 524                     Ok(()) => Ok(()),
 525                 }
 526             }
 527             // cannot use the shim here, because that will only result in infinite recursion
 528             ty::InstanceDef::Virtual(def_id, idx) => {
 529                 let mut args = args.to_vec();
 530                 // We have to implement all "object safe receivers". So we have to go search for a
 531                 // pointer or `dyn Trait` type, but it could be wrapped in newtypes. So recursively
 532                 // unwrap those newtypes until we are there.
 533                 let mut receiver = args[0].clone();
 534                 let receiver_place = loop {
 535                     match receiver.layout.ty.kind() {
 536                         ty::Ref(..) | ty::RawPtr(..) => break self.deref_operand(&receiver)?,
 537                         ty::Dynamic(..) => break receiver.assert_mem_place(), // no immediate unsized values
 538                         _ => {
 539                             // Not there yet, search for the only non-ZST field.
 540                             let mut non_zst_field = None;
 541                             for i in 0..receiver.layout.fields.count() {
 542                                 let field = self.operand_field(&receiver, i)?;
 543                                 let zst =
 544                                     field.layout.is_zst() && field.layout.align.abi.bytes() == 1;
 545                                 if !zst {
 546                                     assert!(
 547                                         non_zst_field.is_none(),
 548                                         "multiple non-ZST fields in dyn receiver type {}",
 549                                         receiver.layout.ty
 550                                     );
 551                                     non_zst_field = Some(field);
 552                                 }
 553                             }
 554                             receiver = non_zst_field.unwrap_or_else(|| {
 555                                 panic!(
 556                                     "no non-ZST fields in dyn receiver type {}",
 557                                     receiver.layout.ty
 558                                 )
 559                             });
 560                         }
 561                     }
 562                 };
 563                 // Obtain the underlying trait we are working on.
 564                 let receiver_tail = self
 565                     .tcx
 566                     .struct_tail_erasing_lifetimes(receiver_place.layout.ty, self.param_env);
 567                 let ty::Dynamic(data, ..) = receiver_tail.kind() else {
 568                     span_bug!(self.cur_span(), "dynamic call on non-`dyn` type {}", receiver_tail)
 569                 };
 570
 571                 // Get the required information from the vtable.
 572                 let vptr = receiver_place.meta.unwrap_meta().to_pointer(self)?;
 573                 let (dyn_ty, dyn_trait) = self.get_ptr_vtable(vptr)?;
 574                 if dyn_trait != data.principal() {
 575                     throw_ub_format!(
 576                         "`dyn` call on a pointer whose vtable does not match its type"
 577                     );
 578                 }
 579
 580                 // Now determine the actual method to call. We can do that in two different ways and
 581                 // compare them to ensure everything fits.
 582                 let Some(ty::VtblEntry::Method(fn_inst)) = self.get_vtable_entries(vptr)?.get(idx).copied() else {
 583                     throw_ub_format!("`dyn` call trying to call something that is not a method")
 584                 };
 585                 if cfg!(debug_assertions) {
 586                     let tcx = *self.tcx;
 587
 588                     let trait_def_id = tcx.trait_of_item(def_id).unwrap();
 589                     let virtual_trait_ref =
 590                         ty::TraitRef::from_method(tcx, trait_def_id, instance.substs);
 591                     assert_eq!(
 592                         receiver_tail,
 593                         virtual_trait_ref.self_ty(),
 594                         "mismatch in underlying dyn trait computation within Miri and MIR building",
 595                     );
 596                     let existential_trait_ref =
 597                         ty::ExistentialTraitRef::erase_self_ty(tcx, virtual_trait_ref);
 598                     let concrete_trait_ref = existential_trait_ref.with_self_ty(tcx, dyn_ty);
 599
 600                     let concrete_method = Instance::resolve_for_vtable(
 601                         tcx,
 602                         self.param_env,
 603                         def_id,
 604                         instance.substs.rebase_onto(tcx, trait_def_id, concrete_trait_ref.substs),
 605                     )
 606                     .unwrap();
 607                     assert_eq!(fn_inst, concrete_method);
 608                 }
 609
 610                 // `*mut receiver_place.layout.ty` is almost the layout that we
 611                 // want for args[0]: We have to project to field 0 because we want
 612                 // a thin pointer.
 613                 assert!(receiver_place.layout.is_unsized());
 614                 let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
 615                 let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0);
 616                 // Adjust receiver argument.
 617                 args[0] = OpTy::from(ImmTy::from_immediate(
 618                     Scalar::from_maybe_pointer(receiver_place.ptr, self).into(),
 619                     this_receiver_ptr,
 620                 ));
 621                 trace!("Patched receiver operand to {:#?}", args[0]);
 622                 // recurse with concrete function
 623                 self.eval_fn_call(
 624                     FnVal::Instance(fn_inst),
 625                     (caller_abi, caller_fn_abi),
 626                     &args,
 627                     with_caller_location,
 628                     destination,
 629                     target,
 630                     unwind,
 631                 )
 632             }
 633         }
 634     }
 635
 636     fn drop_in_place(
 637         &mut self,
 638         place: &PlaceTy<'tcx, M::Provenance>,
 639         instance: ty::Instance<'tcx>,
 640         target: mir::BasicBlock,
 641         unwind: Option<mir::BasicBlock>,
 642     ) -> InterpResult<'tcx> {
 643         trace!("drop_in_place: {:?},\n  {:?}, {:?}", *place, place.layout.ty, instance);
 644         // We take the address of the object.  This may well be unaligned, which is fine
 645         // for us here.  However, unaligned accesses will probably make the actual drop
 646         // implementation fail -- a problem shared by rustc.
 647         let place = self.force_allocation(place)?;
 648
 649         let (instance, place) = match place.layout.ty.kind() {
 650             ty::Dynamic(..) => {
 651                 // Dropping a trait object. Need to find actual drop fn.
 652                 let place = self.unpack_dyn_trait(&place)?;
 653                 let instance = ty::Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
 654                 (instance, place)
 655             }
 656             _ => (instance, place),
 657         };
 658         let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
 659
 660         let arg = ImmTy::from_immediate(
 661             place.to_ref(self),
 662             self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
 663         );
 664         let ret = MPlaceTy::fake_alloc_zst(self.layout_of(self.tcx.types.unit)?);
 665
 666         self.eval_fn_call(
 667             FnVal::Instance(instance),
 668             (Abi::Rust, fn_abi),
 669             &[arg.into()],
 670             false,
 671             &ret.into(),
 672             Some(target),
 673             match unwind {
 674                 Some(cleanup) => StackPopUnwind::Cleanup(cleanup),
 675                 None => StackPopUnwind::Skip,
 676             },
 677         )
 678     }
 679 }