src/interpreter.rs

   1 use arena::TypedArena;
   2 use rustc::infer;
   3 use rustc::middle::const_eval;
   4 use rustc::middle::def_id::DefId;
   5 use rustc::mir::mir_map::MirMap;
   6 use rustc::mir::repr as mir;
   7 use rustc::traits::{self, ProjectionMode};
   8 use rustc::ty::fold::TypeFoldable;
   9 use rustc::ty::subst::{self, Subst, Substs};
  10 use rustc::ty::{self, TyCtxt};
  11 use rustc::util::nodemap::DefIdMap;
  12 use rustc_data_structures::fnv::FnvHashMap;
  13 use std::cell::RefCell;
  14 use std::iter;
  15 use std::ops::Deref;
  16 use std::rc::Rc;
  17 use syntax::ast;
  18 use syntax::attr;
  19 use syntax::codemap::DUMMY_SP;
  20
  21 use error::{EvalError, EvalResult};
  22 use memory::{self, FieldRepr, Memory, Pointer, Repr};
  23 use primval::{self, PrimVal};
  24
  25 const TRACE_EXECUTION: bool = false;
  26
  27 struct Interpreter<'a, 'tcx: 'a, 'arena> {
  28     /// The results of the type checker, from rustc.
  29     tcx: &'a TyCtxt<'tcx>,
  30
  31     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  32     mir_map: &'a MirMap<'tcx>,
  33
  34     /// A local cache from DefIds to Mir for non-crate-local items.
  35     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  36
  37     /// An arena allocator for type representations.
  38     repr_arena: &'arena TypedArena<Repr>,
  39
  40     /// A cache for in-memory representations of types.
  41     repr_cache: RefCell<FnvHashMap<ty::Ty<'tcx>, &'arena Repr>>,
  42
  43     /// The virtual memory system.
  44     memory: Memory,
  45
  46     /// The virtual call stack.
  47     stack: Vec<Frame<'a, 'tcx>>,
  48
  49     /// Another stack containing the type substitutions for the current function invocation. It
  50     /// exists separately from `stack` because it must contain the `Substs` for a function while
  51     /// *creating* the `Frame` for that same function.
  52     substs_stack: Vec<&'tcx Substs<'tcx>>,
  53 }
  54
  55 /// A stack frame.
  56 struct Frame<'a, 'tcx: 'a> {
  57     /// The MIR for the function called on this frame.
  58     mir: CachedMir<'a, 'tcx>,
  59
  60     /// The block this frame will execute when a function call returns back to this frame.
  61     next_block: mir::BasicBlock,
  62
  63     /// A pointer for writing the return value of the current call if it's not a diverging call.
  64     return_ptr: Option<Pointer>,
  65
  66     /// The list of locals for the current function, stored in order as
  67     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  68     /// and the temporaries at `self.temp_offset`.
  69     locals: Vec<Pointer>,
  70
  71     /// The offset of the first variable in `self.locals`.
  72     var_offset: usize,
  73
  74     /// The offset of the first temporary in `self.locals`.
  75     temp_offset: usize,
  76 }
  77
  78 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  79 struct Lvalue {
  80     ptr: Pointer,
  81     extra: LvalueExtra,
  82 }
  83
  84 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  85 enum LvalueExtra {
  86     None,
  87     Length(u64),
  88     // Vtable(memory::AllocId),
  89 }
  90
  91 #[derive(Clone)]
  92 enum CachedMir<'mir, 'tcx: 'mir> {
  93     Ref(&'mir mir::Mir<'tcx>),
  94     Owned(Rc<mir::Mir<'tcx>>)
  95 }
  96
  97 /// Represents the action to be taken in the main loop as a result of executing a terminator.
  98 enum TerminatorTarget {
  99     /// Make a local jump to the given block.
 100     Block(mir::BasicBlock),
 101
 102     /// Start executing from the new current frame. (For function calls.)
 103     Call,
 104
 105     /// Stop executing the current frame and resume the previous frame.
 106     Return,
 107 }
 108
 109 impl<'a, 'tcx: 'a, 'arena> Interpreter<'a, 'tcx, 'arena> {
 110     fn new(tcx: &'a TyCtxt<'tcx>, mir_map: &'a MirMap<'tcx>, repr_arena: &'arena TypedArena<Repr>)
 111         -> Self
 112     {
 113         Interpreter {
 114             tcx: tcx,
 115             mir_map: mir_map,
 116             mir_cache: RefCell::new(DefIdMap()),
 117             repr_arena: repr_arena,
 118             repr_cache: RefCell::new(FnvHashMap()),
 119             memory: Memory::new(),
 120             stack: Vec::new(),
 121             substs_stack: Vec::new(),
 122         }
 123     }
 124
 125     fn run(&mut self) -> EvalResult<()> {
 126         use std::fmt::Debug;
 127         fn print_trace<T: Debug>(t: &T, suffix: &'static str, indent: usize) {
 128             if !TRACE_EXECUTION { return; }
 129             for _ in 0..indent { print!("  "); }
 130             println!("{:?}{}", t, suffix);
 131         }
 132
 133         'outer: while !self.stack.is_empty() {
 134             let mut current_block = self.frame().next_block;
 135
 136             loop {
 137                 print_trace(&current_block, ":", self.stack.len());
 138                 let current_mir = self.mir().clone(); // Cloning a reference.
 139                 let block_data = current_mir.basic_block_data(current_block);
 140
 141                 for stmt in &block_data.statements {
 142                     print_trace(stmt, "", self.stack.len() + 1);
 143                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 144                     try!(self.eval_assignment(lvalue, rvalue));
 145                 }
 146
 147                 let terminator = block_data.terminator();
 148                 print_trace(terminator, "", self.stack.len() + 1);
 149
 150                 match try!(self.eval_terminator(terminator)) {
 151                     TerminatorTarget::Block(block) => current_block = block,
 152                     TerminatorTarget::Return => {
 153                         self.pop_stack_frame();
 154                         self.substs_stack.pop();
 155                         continue 'outer;
 156                     }
 157                     TerminatorTarget::Call => continue 'outer,
 158                 }
 159             }
 160         }
 161
 162         Ok(())
 163     }
 164
 165     fn push_stack_frame(&mut self, mir: CachedMir<'a, 'tcx>, return_ptr: Option<Pointer>)
 166         -> EvalResult<()>
 167     {
 168         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 169         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 170         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 171
 172         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 173             let size = self.ty_size(ty);
 174             self.memory.allocate(size)
 175         }).collect();
 176
 177         let num_args = mir.arg_decls.len();
 178         let num_vars = mir.var_decls.len();
 179
 180         self.stack.push(Frame {
 181             mir: mir.clone(),
 182             next_block: mir::START_BLOCK,
 183             return_ptr: return_ptr,
 184             locals: locals,
 185             var_offset: num_args,
 186             temp_offset: num_args + num_vars,
 187         });
 188
 189         Ok(())
 190     }
 191
 192     fn pop_stack_frame(&mut self) {
 193         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 194         // TODO(tsion): Deallocate local variables.
 195     }
 196
 197     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 198             -> EvalResult<TerminatorTarget> {
 199         use rustc::mir::repr::TerminatorKind::*;
 200         let target = match terminator.kind {
 201             Return => TerminatorTarget::Return,
 202
 203             Goto { target } => TerminatorTarget::Block(target),
 204
 205             If { ref cond, targets: (then_target, else_target) } => {
 206                 let cond_ptr = try!(self.eval_operand(cond));
 207                 let cond_val = try!(self.memory.read_bool(cond_ptr));
 208                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 209             }
 210
 211             SwitchInt { ref discr, ref values, ref targets, .. } => {
 212                 let discr_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 213                 let discr_size = self.lvalue_repr(discr).size();
 214                 let discr_val = try!(self.memory.read_uint(discr_ptr, discr_size));
 215
 216                 // Branch to the `otherwise` case by default, if no match is found.
 217                 let mut target_block = targets[targets.len() - 1];
 218
 219                 for (index, val_const) in values.iter().enumerate() {
 220                     let ptr = try!(self.const_to_ptr(val_const));
 221                     let val = try!(self.memory.read_uint(ptr, discr_size));
 222                     if discr_val == val {
 223                         target_block = targets[index];
 224                         break;
 225                     }
 226                 }
 227
 228                 TerminatorTarget::Block(target_block)
 229             }
 230
 231             Switch { ref discr, ref targets, .. } => {
 232                 let adt_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 233                 let adt_repr = self.lvalue_repr(discr);
 234                 let discr_size = match *adt_repr {
 235                     Repr::Aggregate { discr_size, .. } => discr_size,
 236                     _ => panic!("attmpted to switch on non-aggregate type"),
 237                 };
 238                 let discr_val = try!(self.memory.read_uint(adt_ptr, discr_size));
 239                 TerminatorTarget::Block(targets[discr_val as usize])
 240             }
 241
 242             Call { ref func, ref args, ref destination, .. } => {
 243                 let mut return_ptr = None;
 244                 if let Some((ref lv, target)) = *destination {
 245                     self.frame_mut().next_block = target;
 246                     return_ptr = Some(try!(self.eval_lvalue(lv)).to_ptr());
 247                 }
 248
 249                 let func_ty = self.operand_ty(func);
 250                 match func_ty.sty {
 251                     ty::TyFnDef(def_id, substs, fn_ty) => {
 252                         use syntax::abi::Abi;
 253                         match fn_ty.abi {
 254                             Abi::RustIntrinsic => {
 255                                 let name = self.tcx.item_name(def_id).as_str();
 256                                 match fn_ty.sig.0.output {
 257                                     ty::FnConverging(ty) => {
 258                                         let size = self.ty_size(ty);
 259                                         try!(self.call_intrinsic(&name, substs, args,
 260                                             return_ptr.unwrap(), size))
 261                                     }
 262                                     ty::FnDiverging => unimplemented!(),
 263                                 }
 264                             }
 265
 266                             Abi::C =>
 267                                 try!(self.call_c_abi(def_id, args, return_ptr.unwrap())),
 268
 269                             Abi::Rust | Abi::RustCall => {
 270                                 // TODO(tsion): Adjust the first argument when calling a Fn or
 271                                 // FnMut closure via FnOnce::call_once.
 272
 273                                 // Only trait methods can have a Self parameter.
 274                                 let (def_id, substs) = if substs.self_ty().is_some() {
 275                                     self.trait_method(def_id, substs)
 276                                 } else {
 277                                     (def_id, substs)
 278                                 };
 279
 280                                 let mut arg_srcs = Vec::new();
 281                                 for arg in args {
 282                                     let (src, repr) = try!(self.eval_operand_and_repr(arg));
 283                                     arg_srcs.push((src, repr.size()));
 284                                 }
 285
 286                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 287                                     arg_srcs.pop();
 288                                     let last_arg = args.last().unwrap();
 289                                     let (last_src, last_repr) =
 290                                         try!(self.eval_operand_and_repr(last_arg));
 291                                     match *last_repr {
 292                                         Repr::Aggregate { discr_size: 0, ref variants, .. } => {
 293                                             assert_eq!(variants.len(), 1);
 294                                             for field in &variants[0] {
 295                                                 let src = last_src.offset(field.offset as isize);
 296                                                 arg_srcs.push((src, field.size));
 297                                             }
 298                                         }
 299
 300                                         _ => panic!("expected tuple as last argument in function with 'rust-call' ABI"),
 301                                     }
 302                                 }
 303
 304                                 let mir = self.load_mir(def_id);
 305                                 self.substs_stack.push(substs);
 306                                 try!(self.push_stack_frame(mir, return_ptr));
 307
 308                                 for (i, (src, size)) in arg_srcs.into_iter().enumerate() {
 309                                     let dest = self.frame().locals[i];
 310                                     try!(self.memory.copy(src, dest, size));
 311                                 }
 312
 313                                 TerminatorTarget::Call
 314                             }
 315
 316                             abi => panic!("can't handle function with {:?} ABI", abi),
 317                         }
 318                     }
 319
 320                     _ => panic!("can't handle callee of type {:?}", func_ty),
 321                 }
 322             }
 323
 324             Drop { target, .. } => {
 325                 // TODO: Handle destructors and dynamic drop.
 326                 TerminatorTarget::Block(target)
 327             }
 328
 329             Resume => unimplemented!(),
 330         };
 331
 332         Ok(target)
 333     }
 334
 335     fn call_intrinsic(&mut self, name: &str, substs: &'tcx Substs<'tcx>,
 336         args: &[mir::Operand<'tcx>], dest: Pointer, dest_size: usize)
 337         -> EvalResult<TerminatorTarget>
 338     {
 339         match name {
 340             "assume" => {}
 341
 342             "copy_nonoverlapping" => {
 343                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 344                 let elem_size = self.ty_size(elem_ty);
 345
 346                 let src_arg   = try!(self.eval_operand(&args[0]));
 347                 let dest_arg  = try!(self.eval_operand(&args[1]));
 348                 let count_arg = try!(self.eval_operand(&args[2]));
 349
 350                 let src   = try!(self.memory.read_ptr(src_arg));
 351                 let dest  = try!(self.memory.read_ptr(dest_arg));
 352                 let count = try!(self.memory.read_isize(count_arg));
 353
 354                 try!(self.memory.copy(src, dest, count as usize * elem_size));
 355             }
 356
 357             // TODO(tsion): Mark as dropped?
 358             "forget" => {}
 359
 360             "min_align_of" => {
 361                 try!(self.memory.write_int(dest, 1, dest_size));
 362             }
 363
 364             "move_val_init" => {
 365                 let ty = *substs.types.get(subst::FnSpace, 0);
 366                 let size = self.ty_size(ty);
 367
 368                 let ptr_arg = try!(self.eval_operand(&args[0]));
 369                 let ptr = try!(self.memory.read_ptr(ptr_arg));
 370
 371                 let val = try!(self.eval_operand(&args[1]));
 372                 try!(self.memory.copy(val, ptr, size));
 373             }
 374
 375             // FIXME(tsion): Handle different integer types correctly.
 376             "mul_with_overflow" => {
 377                 let ty = *substs.types.get(subst::FnSpace, 0);
 378                 let size = self.ty_size(ty);
 379
 380                 let left_arg  = try!(self.eval_operand(&args[0]));
 381                 let right_arg = try!(self.eval_operand(&args[1]));
 382
 383                 let left = try!(self.memory.read_int(left_arg, size));
 384                 let right = try!(self.memory.read_int(right_arg, size));
 385
 386                 let (n, overflowed) = unsafe {
 387                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 388                 };
 389
 390                 try!(self.memory.write_int(dest, n, size));
 391                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 392             }
 393
 394             "offset" => {
 395                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 396                 let pointee_size = self.ty_size(pointee_ty) as isize;
 397
 398                 let ptr_arg    = try!(self.eval_operand(&args[0]));
 399                 let offset_arg = try!(self.eval_operand(&args[1]));
 400
 401                 let offset = try!(self.memory.read_isize(offset_arg));
 402
 403                 match self.memory.read_ptr(ptr_arg) {
 404                     Ok(ptr) => {
 405                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 406                         try!(self.memory.write_ptr(dest, result_ptr));
 407                     }
 408                     Err(EvalError::ReadBytesAsPointer) => {
 409                         let addr = try!(self.memory.read_isize(ptr_arg));
 410                         let result_addr = addr + offset * pointee_size as i64;
 411                         try!(self.memory.write_isize(dest, result_addr));
 412                     }
 413                     Err(e) => return Err(e),
 414                 }
 415             }
 416
 417             // FIXME(tsion): Handle different integer types correctly. Use primvals?
 418             "overflowing_sub" => {
 419                 let ty = *substs.types.get(subst::FnSpace, 0);
 420                 let size = self.ty_size(ty);
 421
 422                 let left_arg  = try!(self.eval_operand(&args[0]));
 423                 let right_arg = try!(self.eval_operand(&args[1]));
 424
 425                 let left = try!(self.memory.read_int(left_arg, size));
 426                 let right = try!(self.memory.read_int(right_arg, size));
 427
 428                 let n = left.wrapping_sub(right);
 429                 try!(self.memory.write_int(dest, n, size));
 430             }
 431
 432             "size_of" => {
 433                 let ty = *substs.types.get(subst::FnSpace, 0);
 434                 let size = self.ty_size(ty) as u64;
 435                 try!(self.memory.write_uint(dest, size, dest_size));
 436             }
 437
 438             "transmute" => {
 439                 let src = try!(self.eval_operand(&args[0]));
 440                 try!(self.memory.copy(src, dest, dest_size));
 441             }
 442
 443             "uninit" => {
 444                 try!(self.memory.mark_definedness(dest, dest_size, false));
 445             }
 446
 447             name => panic!("can't handle intrinsic: {}", name),
 448         }
 449
 450         // Since we pushed no stack frame, the main loop will act
 451         // as if the call just completed and it's returning to the
 452         // current frame.
 453         Ok(TerminatorTarget::Call)
 454     }
 455
 456     fn call_c_abi(&mut self, def_id: DefId, args: &[mir::Operand<'tcx>], dest: Pointer)
 457         -> EvalResult<TerminatorTarget>
 458     {
 459         let name = self.tcx.item_name(def_id);
 460         let attrs = self.tcx.get_attrs(def_id);
 461         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 462             Some(ln) => ln.clone(),
 463             None => name.as_str(),
 464         };
 465
 466         match &link_name[..] {
 467             "__rust_allocate" => {
 468                 let size_arg  = try!(self.eval_operand(&args[0]));
 469                 let _align_arg = try!(self.eval_operand(&args[1]));
 470                 let size = try!(self.memory.read_usize(size_arg));
 471                 let ptr = self.memory.allocate(size as usize);
 472                 try!(self.memory.write_ptr(dest, ptr));
 473             }
 474
 475             _ => panic!("can't call C ABI function: {}", link_name),
 476         }
 477
 478         // Since we pushed no stack frame, the main loop will act
 479         // as if the call just completed and it's returning to the
 480         // current frame.
 481         Ok(TerminatorTarget::Call)
 482     }
 483
 484     fn assign_to_aggregate(&mut self, dest: Pointer, dest_repr: &Repr, variant: usize,
 485                          operands: &[mir::Operand<'tcx>]) -> EvalResult<()> {
 486         match *dest_repr {
 487             Repr::Aggregate { discr_size, ref variants, .. } => {
 488                 if discr_size > 0 {
 489                     let discr = variant as u64;
 490                     try!(self.memory.write_uint(dest, discr, discr_size));
 491                 }
 492                 let after_discr = dest.offset(discr_size as isize);
 493                 for (field, operand) in variants[variant].iter().zip(operands) {
 494                     let src = try!(self.eval_operand(operand));
 495                     let field_dest = after_discr.offset(field.offset as isize);
 496                     try!(self.memory.copy(src, field_dest, field.size));
 497                 }
 498             }
 499             _ => panic!("expected Repr::Aggregate target"),
 500         }
 501         Ok(())
 502     }
 503
 504     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 505         -> EvalResult<()>
 506     {
 507         let dest = try!(self.eval_lvalue(lvalue)).to_ptr();
 508         let dest_repr = self.lvalue_repr(lvalue);
 509
 510         use rustc::mir::repr::Rvalue::*;
 511         match *rvalue {
 512             Use(ref operand) => {
 513                 let src = try!(self.eval_operand(operand));
 514                 try!(self.memory.copy(src, dest, dest_repr.size()));
 515             }
 516
 517             BinaryOp(bin_op, ref left, ref right) => {
 518                 let left_ptr = try!(self.eval_operand(left));
 519                 let left_ty = self.operand_ty(left);
 520                 let left_val = try!(self.read_primval(left_ptr, left_ty));
 521
 522                 let right_ptr = try!(self.eval_operand(right));
 523                 let right_ty = self.operand_ty(right);
 524                 let right_val = try!(self.read_primval(right_ptr, right_ty));
 525
 526                 let val = try!(primval::binary_op(bin_op, left_val, right_val));
 527                 try!(self.memory.write_primval(dest, val));
 528             }
 529
 530             UnaryOp(un_op, ref operand) => {
 531                 let ptr = try!(self.eval_operand(operand));
 532                 let ty = self.operand_ty(operand);
 533                 let val = try!(self.read_primval(ptr, ty));
 534                 try!(self.memory.write_primval(dest, primval::unary_op(un_op, val)));
 535             }
 536
 537             Aggregate(ref kind, ref operands) => {
 538                 use rustc::mir::repr::AggregateKind::*;
 539                 match *kind {
 540                     Tuple | Closure(..) =>
 541                         try!(self.assign_to_aggregate(dest, &dest_repr, 0, operands)),
 542
 543                     Adt(_, variant_idx, _) =>
 544                         try!(self.assign_to_aggregate(dest, &dest_repr, variant_idx, operands)),
 545
 546                     Vec => if let Repr::Array { elem_size, length } = *dest_repr {
 547                         assert_eq!(length, operands.len());
 548                         for (i, operand) in operands.iter().enumerate() {
 549                             let src = try!(self.eval_operand(operand));
 550                             let elem_dest = dest.offset((i * elem_size) as isize);
 551                             try!(self.memory.copy(src, elem_dest, elem_size));
 552                         }
 553                     } else {
 554                         panic!("expected Repr::Array target");
 555                     },
 556                 }
 557             }
 558
 559             Repeat(ref operand, _) => {
 560                 if let Repr::Array { elem_size, length } = *dest_repr {
 561                     let src = try!(self.eval_operand(operand));
 562                     for i in 0..length {
 563                         let elem_dest = dest.offset((i * elem_size) as isize);
 564                         try!(self.memory.copy(src, elem_dest, elem_size));
 565                     }
 566                 } else {
 567                     panic!("expected Repr::Array target");
 568                 }
 569             }
 570
 571             Len(ref lvalue) => {
 572                 let src = try!(self.eval_lvalue(lvalue));
 573                 let ty = self.lvalue_ty(lvalue);
 574                 let len = match ty.sty {
 575                     ty::TyArray(_, n) => n as u64,
 576                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 577                         n
 578                     } else {
 579                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 580                     },
 581                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 582                 };
 583                 try!(self.memory.write_usize(dest, len));
 584             }
 585
 586             Ref(_, _, ref lvalue) => {
 587                 let lv = try!(self.eval_lvalue(lvalue));
 588                 try!(self.memory.write_ptr(dest, lv.ptr));
 589                 match lv.extra {
 590                     LvalueExtra::None => {},
 591                     LvalueExtra::Length(len) => {
 592                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 593                         try!(self.memory.write_usize(len_ptr, len));
 594                     }
 595                 }
 596             }
 597
 598             Box(ty) => {
 599                 let size = self.ty_size(ty);
 600                 let ptr = self.memory.allocate(size);
 601                 try!(self.memory.write_ptr(dest, ptr));
 602             }
 603
 604             Cast(kind, ref operand, dest_ty) => {
 605                 let src = try!(self.eval_operand(operand));
 606                 let src_ty = self.operand_ty(operand);
 607
 608                 use rustc::mir::repr::CastKind::*;
 609                 match kind {
 610                     Unsize => {
 611                         try!(self.memory.copy(src, dest, 8));
 612                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 613                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 614
 615                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 616                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 617                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 618                                 try!(self.memory.write_usize(len_ptr, length as u64));
 619                             }
 620
 621                             _ => panic!("can't handle cast: {:?}", rvalue),
 622                         }
 623                     }
 624
 625                     Misc => {
 626                         // FIXME(tsion): Wrong for almost everything.
 627                         let size = dest_repr.size();
 628                         try!(self.memory.copy(src, dest, size));
 629                     }
 630
 631                     _ => panic!("can't handle cast: {:?}", rvalue),
 632                 }
 633             }
 634
 635             Slice { .. } => unimplemented!(),
 636             InlineAsm { .. } => unimplemented!(),
 637         }
 638
 639         Ok(())
 640     }
 641
 642     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 643         self.eval_operand_and_repr(op).map(|(p, _)| p)
 644     }
 645
 646     fn eval_operand_and_repr(&mut self, op: &mir::Operand<'tcx>)
 647         -> EvalResult<(Pointer, &'arena Repr)>
 648     {
 649         use rustc::mir::repr::Operand::*;
 650         match *op {
 651             Consume(ref lvalue) =>
 652                 Ok((try!(self.eval_lvalue(lvalue)).to_ptr(), self.lvalue_repr(lvalue))),
 653             Constant(mir::Constant { ref literal, ty, .. }) => {
 654                 use rustc::mir::repr::Literal::*;
 655                 match *literal {
 656                     Value { ref value } => Ok((
 657                         try!(self.const_to_ptr(value)),
 658                         self.ty_to_repr(ty),
 659                     )),
 660                     Item { .. } => unimplemented!(),
 661                 }
 662             }
 663         }
 664     }
 665
 666     // TODO(tsion): Replace this inefficient hack with a wrapper like LvalueTy (e.g. LvalueRepr).
 667     fn lvalue_repr(&self, lvalue: &mir::Lvalue<'tcx>) -> &'arena Repr {
 668         use rustc::mir::tcx::LvalueTy;
 669         match self.mir().lvalue_ty(self.tcx, lvalue) {
 670             LvalueTy::Ty { ty } => self.ty_to_repr(ty),
 671             LvalueTy::Downcast { ref adt_def, substs, variant_index } => {
 672                 let field_tys = adt_def.variants[variant_index].fields.iter()
 673                     .map(|f| f.ty(self.tcx, substs));
 674                 self.repr_arena.alloc(self.make_aggregate_repr(iter::once(field_tys)))
 675             }
 676         }
 677     }
 678
 679     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
 680         use rustc::mir::repr::Lvalue::*;
 681         let ptr = match *lvalue {
 682             ReturnPointer => self.frame().return_ptr
 683                 .expect("ReturnPointer used in a function with no return value"),
 684             Arg(i) => self.frame().locals[i as usize],
 685             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
 686             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
 687
 688             Static(_def_id) => unimplemented!(),
 689
 690             Projection(ref proj) => {
 691                 let base_ptr = try!(self.eval_lvalue(&proj.base)).to_ptr();
 692                 let base_repr = self.lvalue_repr(&proj.base);
 693                 let base_ty = self.lvalue_ty(&proj.base);
 694                 use rustc::mir::repr::ProjectionElem::*;
 695                 match proj.elem {
 696                     Field(field, _) => match *base_repr {
 697                         Repr::Aggregate { discr_size: 0, ref variants, .. } => {
 698                             let fields = &variants[0];
 699                             base_ptr.offset(fields[field.index()].offset as isize)
 700                         }
 701                         _ => panic!("field access on non-product type: {:?}", base_repr),
 702                     },
 703
 704                     Downcast(..) => match *base_repr {
 705                         Repr::Aggregate { discr_size, .. } => base_ptr.offset(discr_size as isize),
 706                         _ => panic!("variant downcast on non-aggregate type: {:?}", base_repr),
 707                     },
 708
 709                     Deref => {
 710                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
 711                         let ptr = try!(self.memory.read_ptr(base_ptr));
 712                         let extra = match pointee_ty.sty {
 713                             ty::TySlice(_) | ty::TyStr => {
 714                                 let len_ptr = base_ptr.offset(self.memory.pointer_size as isize);
 715                                 let len = try!(self.memory.read_usize(len_ptr));
 716                                 LvalueExtra::Length(len)
 717                             }
 718                             ty::TyTrait(_) => unimplemented!(),
 719                             _ => LvalueExtra::None,
 720                         };
 721                         return Ok(Lvalue { ptr: ptr, extra: extra });
 722                     }
 723
 724                     Index(ref operand) => {
 725                         let elem_size = match base_ty.sty {
 726                             ty::TyArray(elem_ty, _) => self.ty_size(elem_ty),
 727                             ty::TySlice(elem_ty) => self.ty_size(elem_ty),
 728                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
 729                         };
 730                         let n_ptr = try!(self.eval_operand(operand));
 731                         let n = try!(self.memory.read_usize(n_ptr));
 732                         base_ptr.offset(n as isize * elem_size as isize)
 733                     }
 734
 735                     ConstantIndex { .. } => unimplemented!(),
 736                 }
 737             }
 738         };
 739
 740         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
 741     }
 742
 743     // TODO(tsion): Try making const_to_primval instead.
 744     fn const_to_ptr(&mut self, const_val: &const_eval::ConstVal) -> EvalResult<Pointer> {
 745         use rustc::middle::const_eval::ConstVal::*;
 746         match *const_val {
 747             Float(_f) => unimplemented!(),
 748             Integral(int) => {
 749                 // TODO(tsion): Check int constant type.
 750                 let ptr = self.memory.allocate(8);
 751                 try!(self.memory.write_uint(ptr, int.to_u64_unchecked(), 8));
 752                 Ok(ptr)
 753             }
 754             Str(ref s) => {
 755                 let psize = self.memory.pointer_size;
 756                 let static_ptr = self.memory.allocate(s.len());
 757                 let ptr = self.memory.allocate(psize * 2);
 758                 try!(self.memory.write_bytes(static_ptr, s.as_bytes()));
 759                 try!(self.memory.write_ptr(ptr, static_ptr));
 760                 try!(self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64));
 761                 Ok(ptr)
 762             }
 763             ByteStr(ref bs) => {
 764                 let psize = self.memory.pointer_size;
 765                 let static_ptr = self.memory.allocate(bs.len());
 766                 let ptr = self.memory.allocate(psize);
 767                 try!(self.memory.write_bytes(static_ptr, bs));
 768                 try!(self.memory.write_ptr(ptr, static_ptr));
 769                 Ok(ptr)
 770             }
 771             Bool(b) => {
 772                 let ptr = self.memory.allocate(1);
 773                 try!(self.memory.write_bool(ptr, b));
 774                 Ok(ptr)
 775             }
 776             Char(_c)          => unimplemented!(),
 777             Struct(_node_id)  => unimplemented!(),
 778             Tuple(_node_id)   => unimplemented!(),
 779             Function(_def_id) => unimplemented!(),
 780             Array(_, _)       => unimplemented!(),
 781             Repeat(_, _)      => unimplemented!(),
 782             Dummy             => unimplemented!(),
 783         }
 784     }
 785
 786     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> ty::Ty<'tcx> {
 787         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
 788     }
 789
 790     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> ty::Ty<'tcx> {
 791         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
 792     }
 793
 794     fn monomorphize(&self, ty: ty::Ty<'tcx>) -> ty::Ty<'tcx> {
 795         let substituted = ty.subst(self.tcx, self.substs());
 796         infer::normalize_associated_type(self.tcx, &substituted)
 797     }
 798
 799     fn type_is_sized(&self, ty: ty::Ty<'tcx>) -> bool {
 800         ty.is_sized(&self.tcx.empty_parameter_environment(), DUMMY_SP)
 801     }
 802
 803     fn ty_size(&self, ty: ty::Ty<'tcx>) -> usize {
 804         self.ty_to_repr(ty).size()
 805     }
 806
 807     fn ty_to_repr(&self, ty: ty::Ty<'tcx>) -> &'arena Repr {
 808         let ty = self.monomorphize(ty);
 809
 810         if let Some(repr) = self.repr_cache.borrow().get(ty) {
 811             return repr;
 812         }
 813
 814         use syntax::ast::{IntTy, UintTy};
 815         let repr = match ty.sty {
 816             ty::TyBool => Repr::Primitive { size: 1 },
 817
 818             ty::TyInt(IntTy::I8)  | ty::TyUint(UintTy::U8)  => Repr::Primitive { size: 1 },
 819             ty::TyInt(IntTy::I16) | ty::TyUint(UintTy::U16) => Repr::Primitive { size: 2 },
 820             ty::TyInt(IntTy::I32) | ty::TyUint(UintTy::U32) => Repr::Primitive { size: 4 },
 821             ty::TyInt(IntTy::I64) | ty::TyUint(UintTy::U64) => Repr::Primitive { size: 8 },
 822
 823             ty::TyInt(IntTy::Is) | ty::TyUint(UintTy::Us) =>
 824                 Repr::Primitive { size: self.memory.pointer_size },
 825
 826             ty::TyTuple(ref fields) =>
 827                 self.make_aggregate_repr(iter::once(fields.iter().cloned())),
 828
 829             ty::TyEnum(adt_def, substs) | ty::TyStruct(adt_def, substs) => {
 830                 let variants = adt_def.variants.iter().map(|v| {
 831                     v.fields.iter().map(|f| f.ty(self.tcx, substs))
 832                 });
 833                 self.make_aggregate_repr(variants)
 834             }
 835
 836             ty::TyArray(elem_ty, length) => Repr::Array {
 837                 elem_size: self.ty_size(elem_ty),
 838                 length: length,
 839             },
 840
 841             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 842             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 843             ty::TyBox(ty) => {
 844                 if self.type_is_sized(ty) {
 845                     Repr::Primitive { size: self.memory.pointer_size }
 846                 } else {
 847                     Repr::Primitive { size: self.memory.pointer_size * 2 }
 848                 }
 849             }
 850
 851             ty::TyFnPtr(..) => Repr::Primitive { size: self.memory.pointer_size },
 852
 853             ty::TyClosure(_, ref closure_substs) =>
 854                 self.make_aggregate_repr(iter::once(closure_substs.upvar_tys.iter().cloned())),
 855
 856             ref t => panic!("can't convert type to repr: {:?}", t),
 857         };
 858
 859         let repr_ref = self.repr_arena.alloc(repr);
 860         self.repr_cache.borrow_mut().insert(ty, repr_ref);
 861         repr_ref
 862     }
 863
 864     fn make_aggregate_repr<V>(&self, variant_fields: V) -> Repr
 865         where V: IntoIterator, V::Item: IntoIterator<Item = ty::Ty<'tcx>>
 866     {
 867         let mut variants = Vec::new();
 868         let mut max_variant_size = 0;
 869
 870         for field_tys in variant_fields {
 871             let mut fields = Vec::new();
 872             let mut size = 0;
 873
 874             for ty in field_tys {
 875                 let field_size = self.ty_size(ty);
 876                 let offest = size;
 877                 size += field_size;
 878                 fields.push(FieldRepr { offset: offest, size: field_size });
 879             }
 880
 881             if size > max_variant_size { max_variant_size = size; }
 882             variants.push(fields);
 883         }
 884
 885         let discr_size = match variants.len() {
 886             n if n <= 1       => 0,
 887             n if n <= 1 << 8  => 1,
 888             n if n <= 1 << 16 => 2,
 889             n if n <= 1 << 32 => 4,
 890             _                 => 8,
 891         };
 892         Repr::Aggregate {
 893             discr_size: discr_size,
 894             size: max_variant_size + discr_size,
 895             variants: variants,
 896         }
 897     }
 898
 899     pub fn read_primval(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<PrimVal> {
 900         use syntax::ast::{IntTy, UintTy};
 901         let val = match ty.sty {
 902             ty::TyBool              => PrimVal::Bool(try!(self.memory.read_bool(ptr))),
 903             ty::TyInt(IntTy::I8)    => PrimVal::I8(try!(self.memory.read_int(ptr, 1)) as i8),
 904             ty::TyInt(IntTy::I16)   => PrimVal::I16(try!(self.memory.read_int(ptr, 2)) as i16),
 905             ty::TyInt(IntTy::I32)   => PrimVal::I32(try!(self.memory.read_int(ptr, 4)) as i32),
 906             ty::TyInt(IntTy::I64)   => PrimVal::I64(try!(self.memory.read_int(ptr, 8)) as i64),
 907             ty::TyUint(UintTy::U8)  => PrimVal::U8(try!(self.memory.read_uint(ptr, 1)) as u8),
 908             ty::TyUint(UintTy::U16) => PrimVal::U16(try!(self.memory.read_uint(ptr, 2)) as u16),
 909             ty::TyUint(UintTy::U32) => PrimVal::U32(try!(self.memory.read_uint(ptr, 4)) as u32),
 910             ty::TyUint(UintTy::U64) => PrimVal::U64(try!(self.memory.read_uint(ptr, 8)) as u64),
 911
 912             // TODO(tsion): Pick the PrimVal dynamically.
 913             ty::TyInt(IntTy::Is)   => PrimVal::I64(try!(self.memory.read_isize(ptr))),
 914             ty::TyUint(UintTy::Us) => PrimVal::U64(try!(self.memory.read_usize(ptr))),
 915
 916             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 917             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
 918                 if self.type_is_sized(ty) {
 919                     match self.memory.read_ptr(ptr) {
 920                         Ok(p) => PrimVal::AbstractPtr(p),
 921                         Err(EvalError::ReadBytesAsPointer) => {
 922                             let n = try!(self.memory.read_usize(ptr));
 923                             PrimVal::IntegerPtr(n)
 924                         }
 925                         Err(e) => return Err(e),
 926                     }
 927                 } else {
 928                     panic!("unimplemented: primitive read of fat pointer type: {:?}", ty);
 929                 }
 930             }
 931
 932             _ => panic!("primitive read of non-primitive type: {:?}", ty),
 933         };
 934         Ok(val)
 935     }
 936
 937     fn frame(&self) -> &Frame<'a, 'tcx> {
 938         self.stack.last().expect("no call frames exist")
 939     }
 940
 941     fn frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
 942         self.stack.last_mut().expect("no call frames exist")
 943     }
 944
 945     fn mir(&self) -> &mir::Mir<'tcx> {
 946         &self.frame().mir
 947     }
 948
 949     fn substs(&self) -> &'tcx Substs<'tcx> {
 950         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
 951     }
 952
 953     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
 954         match self.tcx.map.as_local_node_id(def_id) {
 955             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
 956             None => {
 957                 let mut mir_cache = self.mir_cache.borrow_mut();
 958                 if let Some(mir) = mir_cache.get(&def_id) {
 959                     return CachedMir::Owned(mir.clone());
 960                 }
 961
 962                 use rustc::middle::cstore::CrateStore;
 963                 let cs = &self.tcx.sess.cstore;
 964                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
 965                     panic!("no mir for {:?}", def_id);
 966                 });
 967                 let cached = Rc::new(mir);
 968                 mir_cache.insert(def_id, cached.clone());
 969                 CachedMir::Owned(cached)
 970             }
 971         }
 972     }
 973
 974     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
 975         // Do the initial selection for the obligation. This yields the shallow result we are
 976         // looking for -- that is, what specific impl.
 977         let infcx = infer::normalizing_infer_ctxt(self.tcx, &self.tcx.tables, ProjectionMode::Any);
 978         let mut selcx = traits::SelectionContext::new(&infcx);
 979
 980         let obligation = traits::Obligation::new(
 981             traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
 982             trait_ref.to_poly_trait_predicate(),
 983         );
 984         let selection = selcx.select(&obligation).unwrap().unwrap();
 985
 986         // Currently, we use a fulfillment context to completely resolve all nested obligations.
 987         // This is because they can inform the inference of the impl's type parameters.
 988         let mut fulfill_cx = traits::FulfillmentContext::new();
 989         let vtable = selection.map(|predicate| {
 990             fulfill_cx.register_predicate_obligation(&infcx, predicate);
 991         });
 992         let vtable = infer::drain_fulfillment_cx_or_panic(
 993             DUMMY_SP, &infcx, &mut fulfill_cx, &vtable
 994         );
 995
 996         vtable
 997     }
 998
 999     /// Trait method, which has to be resolved to an impl method.
1000     pub fn trait_method(&self, def_id: DefId, substs: &'tcx Substs<'tcx>)
1001         -> (DefId, &'tcx Substs<'tcx>)
1002     {
1003         let method_item = self.tcx.impl_or_trait_item(def_id);
1004         let trait_id = method_item.container().id();
1005         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1006         match self.fulfill_obligation(trait_ref) {
1007             traits::VtableImpl(vtable_impl) => {
1008                 let impl_did = vtable_impl.impl_def_id;
1009                 let mname = self.tcx.item_name(def_id);
1010                 // Create a concatenated set of substitutions which includes those from the impl
1011                 // and those from the method:
1012                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1013                 let substs = self.tcx.mk_substs(impl_substs);
1014                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1015
1016                 (mth.method.def_id, mth.substs)
1017             }
1018
1019             traits::VtableClosure(vtable_closure) =>
1020                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1021
1022             traits::VtableFnPointer(_fn_ty) => {
1023                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1024                 unimplemented!()
1025                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1026
1027                 // let method_ty = def_ty(tcx, def_id, substs);
1028                 // let fn_ptr_ty = match method_ty.sty {
1029                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1030                 //     _ => unreachable!("expected fn item type, found {}",
1031                 //                       method_ty)
1032                 // };
1033                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1034             }
1035
1036             traits::VtableObject(ref _data) => {
1037                 unimplemented!()
1038                 // Callee {
1039                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1040                 //                   tcx, data, def_id)),
1041                 //                   ty: def_ty(tcx, def_id, substs)
1042                 // }
1043             }
1044             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1045         }
1046     }
1047 }
1048
1049 fn pointee_type<'tcx>(ptr_ty: ty::Ty<'tcx>) -> Option<ty::Ty<'tcx>> {
1050     match ptr_ty.sty {
1051         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1052         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1053         ty::TyBox(ty) => {
1054             Some(ty)
1055         }
1056         _ => None,
1057     }
1058 }
1059
1060 impl Lvalue {
1061     fn to_ptr(self) -> Pointer {
1062         assert_eq!(self.extra, LvalueExtra::None);
1063         self.ptr
1064     }
1065 }
1066
1067 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1068     type Target = mir::Mir<'tcx>;
1069     fn deref(&self) -> &mir::Mir<'tcx> {
1070         match *self {
1071             CachedMir::Ref(r) => r,
1072             CachedMir::Owned(ref rc) => &rc,
1073         }
1074     }
1075 }
1076
1077 #[derive(Debug)]
1078 pub struct ImplMethod<'tcx> {
1079     pub method: Rc<ty::Method<'tcx>>,
1080     pub substs: &'tcx Substs<'tcx>,
1081     pub is_provided: bool,
1082 }
1083
1084 /// Locates the applicable definition of a method, given its name.
1085 pub fn get_impl_method<'tcx>(
1086     tcx: &TyCtxt<'tcx>,
1087     impl_def_id: DefId,
1088     substs: &'tcx Substs<'tcx>,
1089     name: ast::Name,
1090 ) -> ImplMethod<'tcx> {
1091     assert!(!substs.types.needs_infer());
1092
1093     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1094     let trait_def = tcx.lookup_trait_def(trait_def_id);
1095     let infcx = infer::normalizing_infer_ctxt(tcx, &tcx.tables, ProjectionMode::Any);
1096
1097     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1098         Some(node_item) => {
1099             ImplMethod {
1100                 method: node_item.item,
1101                 substs: traits::translate_substs(&infcx, impl_def_id, substs, node_item.node),
1102                 is_provided: node_item.node.is_from_trait(),
1103             }
1104         }
1105         None => {
1106             tcx.sess.bug(&format!("method {:?} not found in {:?}", name, impl_def_id))
1107         }
1108     }
1109 }
1110
1111 pub fn interpret_start_points<'tcx>(tcx: &TyCtxt<'tcx>, mir_map: &MirMap<'tcx>) {
1112     /// Print the given allocation and all allocations it depends on.
1113     fn print_allocation_tree(memory: &Memory, alloc_id: memory::AllocId) {
1114         let alloc = memory.get(alloc_id).unwrap();
1115         println!("  {:?}: {:?}", alloc_id, alloc);
1116         for &target_alloc in alloc.relocations.values() {
1117             print_allocation_tree(memory, target_alloc);
1118         }
1119     }
1120
1121     for (&id, mir) in &mir_map.map {
1122         for attr in tcx.map.attrs(id) {
1123             use syntax::attr::AttrMetaMethods;
1124             if attr.check_name("miri_run") {
1125                 let item = tcx.map.expect_item(id);
1126
1127                 println!("Interpreting: {}", item.name);
1128
1129                 let repr_arena = TypedArena::new();
1130                 let mut miri = Interpreter::new(tcx, mir_map, &repr_arena);
1131                 let return_ptr = match mir.return_ty {
1132                     ty::FnConverging(ty) => {
1133                         let size = miri.ty_size(ty);
1134                         Some(miri.memory.allocate(size))
1135                     }
1136                     ty::FnDiverging => None,
1137                 };
1138                 miri.push_stack_frame(CachedMir::Ref(mir), return_ptr).unwrap();
1139                 miri.run().unwrap();
1140
1141                 if let Some(ret) = return_ptr {
1142                     println!("Result:");
1143                     print_allocation_tree(&miri.memory, ret.alloc_id);
1144                     println!("");
1145                 }
1146             }
1147         }
1148     }
1149 }