src/interpreter.rs

   1 use arena::TypedArena;
   2 use rustc::infer;
   3 use rustc::middle::const_val;
   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::{self, DUMMY_SP};
  20
  21 use error::{EvalError, EvalResult};
  22 use memory::{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     // TODO(tsion): Merge with `substs_stack`. Also try restructuring `Frame` to accomodate.
  55     /// A stack of the things necessary to print good strack traces:
  56     ///   * Function DefIds and Substs to print proper substituted function names.
  57     ///   * Spans pointing to specific function calls in the source.
  58     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
  59 }
  60
  61 /// A stack frame.
  62 struct Frame<'a, 'tcx: 'a> {
  63     /// The MIR for the function called on this frame.
  64     mir: CachedMir<'a, 'tcx>,
  65
  66     /// The block this frame will execute when a function call returns back to this frame.
  67     next_block: mir::BasicBlock,
  68
  69     /// A pointer for writing the return value of the current call if it's not a diverging call.
  70     return_ptr: Option<Pointer>,
  71
  72     /// The list of locals for the current function, stored in order as
  73     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  74     /// and the temporaries at `self.temp_offset`.
  75     locals: Vec<Pointer>,
  76
  77     /// The offset of the first variable in `self.locals`.
  78     var_offset: usize,
  79
  80     /// The offset of the first temporary in `self.locals`.
  81     temp_offset: usize,
  82 }
  83
  84 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  85 struct Lvalue {
  86     ptr: Pointer,
  87     extra: LvalueExtra,
  88 }
  89
  90 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  91 enum LvalueExtra {
  92     None,
  93     Length(u64),
  94     // Vtable(memory::AllocId),
  95 }
  96
  97 #[derive(Clone)]
  98 enum CachedMir<'mir, 'tcx: 'mir> {
  99     Ref(&'mir mir::Mir<'tcx>),
 100     Owned(Rc<mir::Mir<'tcx>>)
 101 }
 102
 103 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 104 enum TerminatorTarget {
 105     /// Make a local jump to the given block.
 106     Block(mir::BasicBlock),
 107
 108     /// Start executing from the new current frame. (For function calls.)
 109     Call,
 110
 111     /// Stop executing the current frame and resume the previous frame.
 112     Return,
 113 }
 114
 115 impl<'a, 'tcx: 'a, 'arena> Interpreter<'a, 'tcx, 'arena> {
 116     fn new(tcx: &'a TyCtxt<'tcx>, mir_map: &'a MirMap<'tcx>, repr_arena: &'arena TypedArena<Repr>)
 117         -> Self
 118     {
 119         Interpreter {
 120             tcx: tcx,
 121             mir_map: mir_map,
 122             mir_cache: RefCell::new(DefIdMap()),
 123             repr_arena: repr_arena,
 124             repr_cache: RefCell::new(FnvHashMap()),
 125             memory: Memory::new(),
 126             stack: Vec::new(),
 127             substs_stack: Vec::new(),
 128             name_stack: Vec::new(),
 129         }
 130     }
 131
 132     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 133         if let Err(ref e) = r {
 134             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 135             for &(def_id, substs, span) in self.name_stack.iter().rev() {
 136                 // FIXME(tsion): Find a way to do this without this Display impl hack.
 137                 use rustc::util::ppaux;
 138                 use std::fmt;
 139                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 140                 impl<'tcx> fmt::Display for Instance<'tcx> {
 141                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 142                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 143                             |tcx| tcx.lookup_item_type(self.0).generics)
 144                     }
 145                 }
 146                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 147             }
 148             err.emit();
 149         }
 150         r
 151     }
 152
 153     fn log<F>(&self, extra_indent: usize, f: F) where F: FnOnce() {
 154         let indent = self.stack.len() - 1 + extra_indent;
 155         if !TRACE_EXECUTION { return; }
 156         for _ in 0..indent { print!("  "); }
 157         f();
 158         println!("");
 159     }
 160
 161     fn run(&mut self) -> EvalResult<()> {
 162         'outer: while !self.stack.is_empty() {
 163             let mut current_block = self.frame().next_block;
 164
 165             loop {
 166                 self.log(0, || print!("{:?}", current_block));
 167                 let current_mir = self.mir().clone(); // Cloning a reference.
 168                 let block_data = current_mir.basic_block_data(current_block);
 169
 170                 for stmt in &block_data.statements {
 171                     self.log(1, || print!("{:?}", stmt));
 172                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 173                     let result = self.eval_assignment(lvalue, rvalue);
 174                     try!(self.maybe_report(stmt.span, result));
 175                 }
 176
 177                 let terminator = block_data.terminator();
 178                 self.log(1, || print!("{:?}", terminator.kind));
 179
 180                 let result = self.eval_terminator(terminator);
 181                 match try!(self.maybe_report(terminator.span, result)) {
 182                     TerminatorTarget::Block(block) => current_block = block,
 183                     TerminatorTarget::Return => {
 184                         self.pop_stack_frame();
 185                         self.name_stack.pop();
 186                         continue 'outer;
 187                     }
 188                     TerminatorTarget::Call => continue 'outer,
 189                 }
 190             }
 191         }
 192
 193         Ok(())
 194     }
 195
 196     fn push_stack_frame(&mut self, mir: CachedMir<'a, 'tcx>, substs: &'tcx Substs<'tcx>,
 197         return_ptr: Option<Pointer>)
 198     {
 199         self.substs_stack.push(substs);
 200
 201         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 202         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 203         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 204
 205         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 206             let size = self.type_size(ty);
 207             self.memory.allocate(size)
 208         }).collect();
 209
 210         let num_args = mir.arg_decls.len();
 211         let num_vars = mir.var_decls.len();
 212
 213         self.stack.push(Frame {
 214             mir: mir.clone(),
 215             next_block: mir::START_BLOCK,
 216             return_ptr: return_ptr,
 217             locals: locals,
 218             var_offset: num_args,
 219             temp_offset: num_args + num_vars,
 220         });
 221     }
 222
 223     fn pop_stack_frame(&mut self) {
 224         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 225         // TODO(tsion): Deallocate local variables.
 226         self.substs_stack.pop();
 227     }
 228
 229     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 230             -> EvalResult<TerminatorTarget> {
 231         use rustc::mir::repr::TerminatorKind::*;
 232         let target = match terminator.kind {
 233             Return => TerminatorTarget::Return,
 234
 235             Goto { target } => TerminatorTarget::Block(target),
 236
 237             If { ref cond, targets: (then_target, else_target) } => {
 238                 let cond_ptr = try!(self.eval_operand(cond));
 239                 let cond_val = try!(self.memory.read_bool(cond_ptr));
 240                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 241             }
 242
 243             SwitchInt { ref discr, ref values, ref targets, .. } => {
 244                 let discr_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 245                 let discr_size = self.lvalue_repr(discr).size();
 246                 let discr_val = try!(self.memory.read_uint(discr_ptr, discr_size));
 247
 248                 // Branch to the `otherwise` case by default, if no match is found.
 249                 let mut target_block = targets[targets.len() - 1];
 250
 251                 for (index, val_const) in values.iter().enumerate() {
 252                     let ptr = try!(self.const_to_ptr(val_const));
 253                     let val = try!(self.memory.read_uint(ptr, discr_size));
 254                     if discr_val == val {
 255                         target_block = targets[index];
 256                         break;
 257                     }
 258                 }
 259
 260                 TerminatorTarget::Block(target_block)
 261             }
 262
 263             Switch { ref discr, ref targets, adt_def } => {
 264                 let adt_ptr = try!(self.eval_lvalue(discr)).to_ptr();
 265                 let adt_repr = self.lvalue_repr(discr);
 266                 let discr_size = match *adt_repr {
 267                     Repr::Aggregate { discr_size, .. } => discr_size,
 268                     _ => panic!("attmpted to switch on non-aggregate type"),
 269                 };
 270                 let discr_val = try!(self.memory.read_uint(adt_ptr, discr_size));
 271
 272                 let matching = adt_def.variants.iter()
 273                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 274
 275                 match matching {
 276                     Some(i) => TerminatorTarget::Block(targets[i]),
 277                     None => return Err(EvalError::InvalidDiscriminant),
 278                 }
 279             }
 280
 281             Call { ref func, ref args, ref destination, .. } => {
 282                 let mut return_ptr = None;
 283                 if let Some((ref lv, target)) = *destination {
 284                     self.frame_mut().next_block = target;
 285                     return_ptr = Some(try!(self.eval_lvalue(lv)).to_ptr());
 286                 }
 287
 288                 let func_ty = self.operand_ty(func);
 289                 match func_ty.sty {
 290                     ty::TyFnDef(def_id, substs, fn_ty) => {
 291                         use syntax::abi::Abi;
 292                         match fn_ty.abi {
 293                             Abi::RustIntrinsic => {
 294                                 let name = self.tcx.item_name(def_id).as_str();
 295                                 match fn_ty.sig.0.output {
 296                                     ty::FnConverging(ty) => {
 297                                         let size = self.type_size(ty);
 298                                         try!(self.call_intrinsic(&name, substs, args,
 299                                             return_ptr.unwrap(), size))
 300                                     }
 301                                     ty::FnDiverging => unimplemented!(),
 302                                 }
 303                             }
 304
 305                             Abi::C =>
 306                                 try!(self.call_c_abi(def_id, args, return_ptr.unwrap())),
 307
 308                             Abi::Rust | Abi::RustCall => {
 309                                 // TODO(tsion): Adjust the first argument when calling a Fn or
 310                                 // FnMut closure via FnOnce::call_once.
 311
 312                                 // Only trait methods can have a Self parameter.
 313                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 314                                     self.trait_method(def_id, substs)
 315                                 } else {
 316                                     (def_id, substs)
 317                                 };
 318
 319                                 let mut arg_srcs = Vec::new();
 320                                 for arg in args {
 321                                     let (src, repr) = try!(self.eval_operand_and_repr(arg));
 322                                     arg_srcs.push((src, repr.size()));
 323                                 }
 324
 325                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 326                                     arg_srcs.pop();
 327                                     let last_arg = args.last().unwrap();
 328                                     let (last_src, last_repr) =
 329                                         try!(self.eval_operand_and_repr(last_arg));
 330                                     match *last_repr {
 331                                         Repr::Aggregate { discr_size: 0, ref variants, .. } => {
 332                                             assert_eq!(variants.len(), 1);
 333                                             for field in &variants[0] {
 334                                                 let src = last_src.offset(field.offset as isize);
 335                                                 arg_srcs.push((src, field.size));
 336                                             }
 337                                         }
 338
 339                                         _ => panic!("expected tuple as last argument in function with 'rust-call' ABI"),
 340                                     }
 341                                 }
 342
 343                                 let mir = self.load_mir(resolved_def_id);
 344                                 self.name_stack.push((def_id, substs, terminator.span));
 345                                 self.push_stack_frame(mir, resolved_substs, return_ptr);
 346
 347                                 for (i, (src, size)) in arg_srcs.into_iter().enumerate() {
 348                                     let dest = self.frame().locals[i];
 349                                     try!(self.memory.copy(src, dest, size));
 350                                 }
 351
 352                                 TerminatorTarget::Call
 353                             }
 354
 355                             abi => panic!("can't handle function with {:?} ABI", abi),
 356                         }
 357                     }
 358
 359                     _ => panic!("can't handle callee of type {:?}", func_ty),
 360                 }
 361             }
 362
 363             Drop { target, .. } => {
 364                 // TODO: Handle destructors and dynamic drop.
 365                 TerminatorTarget::Block(target)
 366             }
 367
 368             Resume => unimplemented!(),
 369         };
 370
 371         Ok(target)
 372     }
 373
 374     fn call_intrinsic(&mut self, name: &str, substs: &'tcx Substs<'tcx>,
 375         args: &[mir::Operand<'tcx>], dest: Pointer, dest_size: usize)
 376         -> EvalResult<TerminatorTarget>
 377     {
 378         match name {
 379             "assume" => {}
 380
 381             "copy_nonoverlapping" => {
 382                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 383                 let elem_size = self.type_size(elem_ty);
 384
 385                 let src_arg   = try!(self.eval_operand(&args[0]));
 386                 let dest_arg  = try!(self.eval_operand(&args[1]));
 387                 let count_arg = try!(self.eval_operand(&args[2]));
 388
 389                 let src   = try!(self.memory.read_ptr(src_arg));
 390                 let dest  = try!(self.memory.read_ptr(dest_arg));
 391                 let count = try!(self.memory.read_isize(count_arg));
 392
 393                 try!(self.memory.copy(src, dest, count as usize * elem_size));
 394             }
 395
 396             // TODO(tsion): Mark as dropped?
 397             "forget" => {}
 398
 399             "min_align_of" => {
 400                 try!(self.memory.write_int(dest, 1, dest_size));
 401             }
 402
 403             "move_val_init" => {
 404                 let ty = *substs.types.get(subst::FnSpace, 0);
 405                 let size = self.type_size(ty);
 406
 407                 let ptr_arg = try!(self.eval_operand(&args[0]));
 408                 let ptr = try!(self.memory.read_ptr(ptr_arg));
 409
 410                 let val = try!(self.eval_operand(&args[1]));
 411                 try!(self.memory.copy(val, ptr, size));
 412             }
 413
 414             // FIXME(tsion): Handle different integer types correctly.
 415             "add_with_overflow" => {
 416                 let ty = *substs.types.get(subst::FnSpace, 0);
 417                 let size = self.type_size(ty);
 418
 419                 let left_arg  = try!(self.eval_operand(&args[0]));
 420                 let right_arg = try!(self.eval_operand(&args[1]));
 421
 422                 let left = try!(self.memory.read_int(left_arg, size));
 423                 let right = try!(self.memory.read_int(right_arg, size));
 424
 425                 let (n, overflowed) = unsafe {
 426                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 427                 };
 428
 429                 try!(self.memory.write_int(dest, n, size));
 430                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 431             }
 432
 433             // FIXME(tsion): Handle different integer types correctly.
 434             "mul_with_overflow" => {
 435                 let ty = *substs.types.get(subst::FnSpace, 0);
 436                 let size = self.type_size(ty);
 437
 438                 let left_arg  = try!(self.eval_operand(&args[0]));
 439                 let right_arg = try!(self.eval_operand(&args[1]));
 440
 441                 let left = try!(self.memory.read_int(left_arg, size));
 442                 let right = try!(self.memory.read_int(right_arg, size));
 443
 444                 let (n, overflowed) = unsafe {
 445                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 446                 };
 447
 448                 try!(self.memory.write_int(dest, n, size));
 449                 try!(self.memory.write_bool(dest.offset(size as isize), overflowed));
 450             }
 451
 452             "offset" => {
 453                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 454                 let pointee_size = self.type_size(pointee_ty) as isize;
 455
 456                 let ptr_arg    = try!(self.eval_operand(&args[0]));
 457                 let offset_arg = try!(self.eval_operand(&args[1]));
 458
 459                 let offset = try!(self.memory.read_isize(offset_arg));
 460
 461                 match self.memory.read_ptr(ptr_arg) {
 462                     Ok(ptr) => {
 463                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 464                         try!(self.memory.write_ptr(dest, result_ptr));
 465                     }
 466                     Err(EvalError::ReadBytesAsPointer) => {
 467                         let addr = try!(self.memory.read_isize(ptr_arg));
 468                         let result_addr = addr + offset * pointee_size as i64;
 469                         try!(self.memory.write_isize(dest, result_addr));
 470                     }
 471                     Err(e) => return Err(e),
 472                 }
 473             }
 474
 475             // FIXME(tsion): Handle different integer types correctly. Use primvals?
 476             "overflowing_sub" => {
 477                 let ty = *substs.types.get(subst::FnSpace, 0);
 478                 let size = self.type_size(ty);
 479
 480                 let left_arg  = try!(self.eval_operand(&args[0]));
 481                 let right_arg = try!(self.eval_operand(&args[1]));
 482
 483                 let left = try!(self.memory.read_int(left_arg, size));
 484                 let right = try!(self.memory.read_int(right_arg, size));
 485
 486                 let n = left.wrapping_sub(right);
 487                 try!(self.memory.write_int(dest, n, size));
 488             }
 489
 490             "size_of" => {
 491                 let ty = *substs.types.get(subst::FnSpace, 0);
 492                 let size = self.type_size(ty) as u64;
 493                 try!(self.memory.write_uint(dest, size, dest_size));
 494             }
 495
 496             "transmute" => {
 497                 let src = try!(self.eval_operand(&args[0]));
 498                 try!(self.memory.copy(src, dest, dest_size));
 499             }
 500
 501             "uninit" => {
 502                 try!(self.memory.mark_definedness(dest, dest_size, false));
 503             }
 504
 505             name => panic!("can't handle intrinsic: {}", name),
 506         }
 507
 508         // Since we pushed no stack frame, the main loop will act
 509         // as if the call just completed and it's returning to the
 510         // current frame.
 511         Ok(TerminatorTarget::Call)
 512     }
 513
 514     fn call_c_abi(&mut self, def_id: DefId, args: &[mir::Operand<'tcx>], dest: Pointer)
 515         -> EvalResult<TerminatorTarget>
 516     {
 517         let name = self.tcx.item_name(def_id);
 518         let attrs = self.tcx.get_attrs(def_id);
 519         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 520             Some(ln) => ln.clone(),
 521             None => name.as_str(),
 522         };
 523
 524         match &link_name[..] {
 525             "__rust_allocate" => {
 526                 let size_arg  = try!(self.eval_operand(&args[0]));
 527                 let _align_arg = try!(self.eval_operand(&args[1]));
 528                 let size = try!(self.memory.read_usize(size_arg));
 529                 let ptr = self.memory.allocate(size as usize);
 530                 try!(self.memory.write_ptr(dest, ptr));
 531             }
 532
 533             "__rust_reallocate" => {
 534                 let ptr_arg = try!(self.eval_operand(&args[0]));
 535                 let _old_size_arg = try!(self.eval_operand(&args[1]));
 536                 let size_arg = try!(self.eval_operand(&args[2]));
 537                 let _align_arg = try!(self.eval_operand(&args[3]));
 538                 let ptr = try!(self.memory.read_ptr(ptr_arg));
 539                 let size = try!(self.memory.read_usize(size_arg));
 540                 try!(self.memory.reallocate(ptr, size as usize));
 541                 try!(self.memory.write_ptr(dest, ptr));
 542             }
 543
 544             _ => panic!("can't call C ABI function: {}", link_name),
 545         }
 546
 547         // Since we pushed no stack frame, the main loop will act
 548         // as if the call just completed and it's returning to the
 549         // current frame.
 550         Ok(TerminatorTarget::Call)
 551     }
 552
 553     fn assign_to_aggregate(
 554         &mut self,
 555         dest: Pointer,
 556         dest_repr: &Repr,
 557         variant: usize,
 558         discr: Option<u64>,
 559         operands: &[mir::Operand<'tcx>],
 560     ) -> EvalResult<()> {
 561         match *dest_repr {
 562             Repr::Aggregate { discr_size, ref variants, .. } => {
 563                 if discr_size > 0 {
 564                     try!(self.memory.write_uint(dest, discr.unwrap(), discr_size));
 565                 }
 566                 let after_discr = dest.offset(discr_size as isize);
 567                 for (field, operand) in variants[variant].iter().zip(operands) {
 568                     let src = try!(self.eval_operand(operand));
 569                     let field_dest = after_discr.offset(field.offset as isize);
 570                     try!(self.memory.copy(src, field_dest, field.size));
 571                 }
 572             }
 573             _ => panic!("expected Repr::Aggregate target"),
 574         }
 575         Ok(())
 576     }
 577
 578     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 579         -> EvalResult<()>
 580     {
 581         let dest = try!(self.eval_lvalue(lvalue)).to_ptr();
 582         let dest_repr = self.lvalue_repr(lvalue);
 583
 584         use rustc::mir::repr::Rvalue::*;
 585         match *rvalue {
 586             Use(ref operand) => {
 587                 let src = try!(self.eval_operand(operand));
 588                 try!(self.memory.copy(src, dest, dest_repr.size()));
 589             }
 590
 591             BinaryOp(bin_op, ref left, ref right) => {
 592                 let left_ptr = try!(self.eval_operand(left));
 593                 let left_ty = self.operand_ty(left);
 594                 let left_val = try!(self.read_primval(left_ptr, left_ty));
 595
 596                 let right_ptr = try!(self.eval_operand(right));
 597                 let right_ty = self.operand_ty(right);
 598                 let right_val = try!(self.read_primval(right_ptr, right_ty));
 599
 600                 let val = try!(primval::binary_op(bin_op, left_val, right_val));
 601                 try!(self.memory.write_primval(dest, val));
 602             }
 603
 604             UnaryOp(un_op, ref operand) => {
 605                 let ptr = try!(self.eval_operand(operand));
 606                 let ty = self.operand_ty(operand);
 607                 let val = try!(self.read_primval(ptr, ty));
 608                 try!(self.memory.write_primval(dest, primval::unary_op(un_op, val)));
 609             }
 610
 611             Aggregate(ref kind, ref operands) => {
 612                 use rustc::mir::repr::AggregateKind::*;
 613                 match *kind {
 614                     Tuple | Closure(..) =>
 615                         try!(self.assign_to_aggregate(dest, &dest_repr, 0, None, operands)),
 616
 617                     Adt(adt_def, variant, _) => {
 618                         let discr = Some(adt_def.variants[variant].disr_val.to_u64_unchecked());
 619                         try!(self.assign_to_aggregate(dest, &dest_repr, variant, discr, operands));
 620                     }
 621
 622                     Vec => if let Repr::Array { elem_size, length } = *dest_repr {
 623                         assert_eq!(length, operands.len());
 624                         for (i, operand) in operands.iter().enumerate() {
 625                             let src = try!(self.eval_operand(operand));
 626                             let elem_dest = dest.offset((i * elem_size) as isize);
 627                             try!(self.memory.copy(src, elem_dest, elem_size));
 628                         }
 629                     } else {
 630                         panic!("expected Repr::Array target");
 631                     },
 632                 }
 633             }
 634
 635             Repeat(ref operand, _) => {
 636                 if let Repr::Array { elem_size, length } = *dest_repr {
 637                     let src = try!(self.eval_operand(operand));
 638                     for i in 0..length {
 639                         let elem_dest = dest.offset((i * elem_size) as isize);
 640                         try!(self.memory.copy(src, elem_dest, elem_size));
 641                     }
 642                 } else {
 643                     panic!("expected Repr::Array target");
 644                 }
 645             }
 646
 647             Len(ref lvalue) => {
 648                 let src = try!(self.eval_lvalue(lvalue));
 649                 let ty = self.lvalue_ty(lvalue);
 650                 let len = match ty.sty {
 651                     ty::TyArray(_, n) => n as u64,
 652                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 653                         n
 654                     } else {
 655                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 656                     },
 657                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 658                 };
 659                 try!(self.memory.write_usize(dest, len));
 660             }
 661
 662             Ref(_, _, ref lvalue) => {
 663                 let lv = try!(self.eval_lvalue(lvalue));
 664                 try!(self.memory.write_ptr(dest, lv.ptr));
 665                 match lv.extra {
 666                     LvalueExtra::None => {},
 667                     LvalueExtra::Length(len) => {
 668                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 669                         try!(self.memory.write_usize(len_ptr, len));
 670                     }
 671                 }
 672             }
 673
 674             Box(ty) => {
 675                 let size = self.type_size(ty);
 676                 let ptr = self.memory.allocate(size);
 677                 try!(self.memory.write_ptr(dest, ptr));
 678             }
 679
 680             Cast(kind, ref operand, dest_ty) => {
 681                 let src = try!(self.eval_operand(operand));
 682                 let src_ty = self.operand_ty(operand);
 683
 684                 use rustc::mir::repr::CastKind::*;
 685                 match kind {
 686                     Unsize => {
 687                         try!(self.memory.copy(src, dest, 8));
 688                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 689                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 690
 691                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 692                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 693                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 694                                 try!(self.memory.write_usize(len_ptr, length as u64));
 695                             }
 696
 697                             _ => panic!("can't handle cast: {:?}", rvalue),
 698                         }
 699                     }
 700
 701                     Misc => {
 702                         // FIXME(tsion): Wrong for almost everything.
 703                         let size = dest_repr.size();
 704                         try!(self.memory.copy(src, dest, size));
 705                     }
 706
 707                     _ => panic!("can't handle cast: {:?}", rvalue),
 708                 }
 709             }
 710
 711             Slice { .. } => unimplemented!(),
 712             InlineAsm { .. } => unimplemented!(),
 713         }
 714
 715         Ok(())
 716     }
 717
 718     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 719         self.eval_operand_and_repr(op).map(|(p, _)| p)
 720     }
 721
 722     fn eval_operand_and_repr(&mut self, op: &mir::Operand<'tcx>)
 723         -> EvalResult<(Pointer, &'arena Repr)>
 724     {
 725         use rustc::mir::repr::Operand::*;
 726         match *op {
 727             Consume(ref lvalue) =>
 728                 Ok((try!(self.eval_lvalue(lvalue)).to_ptr(), self.lvalue_repr(lvalue))),
 729             Constant(mir::Constant { ref literal, ty, .. }) => {
 730                 use rustc::mir::repr::Literal::*;
 731                 match *literal {
 732                     Value { ref value } => Ok((
 733                         try!(self.const_to_ptr(value)),
 734                         self.type_repr(ty),
 735                     )),
 736                     Item { .. } => unimplemented!(),
 737                 }
 738             }
 739         }
 740     }
 741
 742     // TODO(tsion): Replace this inefficient hack with a wrapper like LvalueTy (e.g. LvalueRepr).
 743     fn lvalue_repr(&self, lvalue: &mir::Lvalue<'tcx>) -> &'arena Repr {
 744         use rustc::mir::tcx::LvalueTy;
 745         match self.mir().lvalue_ty(self.tcx, lvalue) {
 746             LvalueTy::Ty { ty } => self.type_repr(ty),
 747             LvalueTy::Downcast { adt_def, substs, variant_index } => {
 748                 let field_tys = adt_def.variants[variant_index].fields.iter()
 749                     .map(|f| f.ty(self.tcx, substs));
 750                 self.repr_arena.alloc(self.make_aggregate_repr(iter::once(field_tys)))
 751             }
 752         }
 753     }
 754
 755     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
 756         use rustc::mir::repr::Lvalue::*;
 757         let ptr = match *lvalue {
 758             ReturnPointer => self.frame().return_ptr
 759                 .expect("ReturnPointer used in a function with no return value"),
 760             Arg(i) => self.frame().locals[i as usize],
 761             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
 762             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
 763
 764             Static(_def_id) => unimplemented!(),
 765
 766             Projection(ref proj) => {
 767                 let base_ptr = try!(self.eval_lvalue(&proj.base)).to_ptr();
 768                 let base_repr = self.lvalue_repr(&proj.base);
 769                 let base_ty = self.lvalue_ty(&proj.base);
 770                 use rustc::mir::repr::ProjectionElem::*;
 771                 match proj.elem {
 772                     Field(field, _) => match *base_repr {
 773                         Repr::Aggregate { discr_size: 0, ref variants, .. } => {
 774                             let fields = &variants[0];
 775                             base_ptr.offset(fields[field.index()].offset as isize)
 776                         }
 777                         _ => panic!("field access on non-product type: {:?}", base_repr),
 778                     },
 779
 780                     Downcast(..) => match *base_repr {
 781                         Repr::Aggregate { discr_size, .. } => base_ptr.offset(discr_size as isize),
 782                         _ => panic!("variant downcast on non-aggregate type: {:?}", base_repr),
 783                     },
 784
 785                     Deref => {
 786                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
 787                         let ptr = try!(self.memory.read_ptr(base_ptr));
 788                         let extra = match pointee_ty.sty {
 789                             ty::TySlice(_) | ty::TyStr => {
 790                                 let len_ptr = base_ptr.offset(self.memory.pointer_size as isize);
 791                                 let len = try!(self.memory.read_usize(len_ptr));
 792                                 LvalueExtra::Length(len)
 793                             }
 794                             ty::TyTrait(_) => unimplemented!(),
 795                             _ => LvalueExtra::None,
 796                         };
 797                         return Ok(Lvalue { ptr: ptr, extra: extra });
 798                     }
 799
 800                     Index(ref operand) => {
 801                         let elem_size = match base_ty.sty {
 802                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty),
 803                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
 804                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
 805                         };
 806                         let n_ptr = try!(self.eval_operand(operand));
 807                         let n = try!(self.memory.read_usize(n_ptr));
 808                         base_ptr.offset(n as isize * elem_size as isize)
 809                     }
 810
 811                     ConstantIndex { .. } => unimplemented!(),
 812                 }
 813             }
 814         };
 815
 816         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
 817     }
 818
 819     // TODO(tsion): Try making const_to_primval instead.
 820     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
 821         use rustc::middle::const_val::ConstVal::*;
 822         match *const_val {
 823             Float(_f) => unimplemented!(),
 824             Integral(int) => {
 825                 // TODO(tsion): Check int constant type.
 826                 let ptr = self.memory.allocate(8);
 827                 try!(self.memory.write_uint(ptr, int.to_u64_unchecked(), 8));
 828                 Ok(ptr)
 829             }
 830             Str(ref s) => {
 831                 let psize = self.memory.pointer_size;
 832                 let static_ptr = self.memory.allocate(s.len());
 833                 let ptr = self.memory.allocate(psize * 2);
 834                 try!(self.memory.write_bytes(static_ptr, s.as_bytes()));
 835                 try!(self.memory.write_ptr(ptr, static_ptr));
 836                 try!(self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64));
 837                 Ok(ptr)
 838             }
 839             ByteStr(ref bs) => {
 840                 let psize = self.memory.pointer_size;
 841                 let static_ptr = self.memory.allocate(bs.len());
 842                 let ptr = self.memory.allocate(psize);
 843                 try!(self.memory.write_bytes(static_ptr, bs));
 844                 try!(self.memory.write_ptr(ptr, static_ptr));
 845                 Ok(ptr)
 846             }
 847             Bool(b) => {
 848                 let ptr = self.memory.allocate(1);
 849                 try!(self.memory.write_bool(ptr, b));
 850                 Ok(ptr)
 851             }
 852             Char(_c)          => unimplemented!(),
 853             Struct(_node_id)  => unimplemented!(),
 854             Tuple(_node_id)   => unimplemented!(),
 855             Function(_def_id) => unimplemented!(),
 856             Array(_, _)       => unimplemented!(),
 857             Repeat(_, _)      => unimplemented!(),
 858             Dummy             => unimplemented!(),
 859         }
 860     }
 861
 862     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> ty::Ty<'tcx> {
 863         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
 864     }
 865
 866     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> ty::Ty<'tcx> {
 867         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
 868     }
 869
 870     fn monomorphize(&self, ty: ty::Ty<'tcx>) -> ty::Ty<'tcx> {
 871         let substituted = ty.subst(self.tcx, self.substs());
 872         infer::normalize_associated_type(self.tcx, &substituted)
 873     }
 874
 875     fn type_is_sized(&self, ty: ty::Ty<'tcx>) -> bool {
 876         ty.is_sized(&self.tcx.empty_parameter_environment(), DUMMY_SP)
 877     }
 878
 879     fn type_size(&self, ty: ty::Ty<'tcx>) -> usize {
 880         self.type_repr(ty).size()
 881     }
 882
 883     fn type_repr(&self, ty: ty::Ty<'tcx>) -> &'arena Repr {
 884         let ty = self.monomorphize(ty);
 885
 886         if let Some(repr) = self.repr_cache.borrow().get(ty) {
 887             return repr;
 888         }
 889
 890         use syntax::ast::{IntTy, UintTy};
 891         let repr = match ty.sty {
 892             ty::TyBool => Repr::Primitive { size: 1 },
 893
 894             ty::TyInt(IntTy::I8)  | ty::TyUint(UintTy::U8)  => Repr::Primitive { size: 1 },
 895             ty::TyInt(IntTy::I16) | ty::TyUint(UintTy::U16) => Repr::Primitive { size: 2 },
 896             ty::TyInt(IntTy::I32) | ty::TyUint(UintTy::U32) => Repr::Primitive { size: 4 },
 897             ty::TyInt(IntTy::I64) | ty::TyUint(UintTy::U64) => Repr::Primitive { size: 8 },
 898
 899             ty::TyInt(IntTy::Is) | ty::TyUint(UintTy::Us) =>
 900                 Repr::Primitive { size: self.memory.pointer_size },
 901
 902             ty::TyTuple(ref fields) =>
 903                 self.make_aggregate_repr(iter::once(fields.iter().cloned())),
 904
 905             ty::TyEnum(adt_def, substs) | ty::TyStruct(adt_def, substs) => {
 906                 let variants = adt_def.variants.iter().map(|v| {
 907                     v.fields.iter().map(|f| f.ty(self.tcx, substs))
 908                 });
 909                 self.make_aggregate_repr(variants)
 910             }
 911
 912             ty::TyArray(elem_ty, length) => Repr::Array {
 913                 elem_size: self.type_size(elem_ty),
 914                 length: length,
 915             },
 916
 917             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 918             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 919             ty::TyBox(ty) => {
 920                 if self.type_is_sized(ty) {
 921                     Repr::Primitive { size: self.memory.pointer_size }
 922                 } else {
 923                     Repr::Primitive { size: self.memory.pointer_size * 2 }
 924                 }
 925             }
 926
 927             ty::TyFnPtr(..) => Repr::Primitive { size: self.memory.pointer_size },
 928
 929             ty::TyClosure(_, ref closure_substs) =>
 930                 self.make_aggregate_repr(iter::once(closure_substs.upvar_tys.iter().cloned())),
 931
 932             ref t => panic!("can't convert type to repr: {:?}", t),
 933         };
 934
 935         let repr_ref = self.repr_arena.alloc(repr);
 936         self.repr_cache.borrow_mut().insert(ty, repr_ref);
 937         repr_ref
 938     }
 939
 940     fn make_aggregate_repr<V>(&self, variant_fields: V) -> Repr
 941         where V: IntoIterator, V::Item: IntoIterator<Item = ty::Ty<'tcx>>
 942     {
 943         let mut variants = Vec::new();
 944         let mut max_variant_size = 0;
 945
 946         for field_tys in variant_fields {
 947             let mut fields = Vec::new();
 948             let mut size = 0;
 949
 950             for ty in field_tys {
 951                 let field_size = self.type_size(ty);
 952                 let offest = size;
 953                 size += field_size;
 954                 fields.push(FieldRepr { offset: offest, size: field_size });
 955             }
 956
 957             if size > max_variant_size { max_variant_size = size; }
 958             variants.push(fields);
 959         }
 960
 961         let discr_size = match variants.len() {
 962             n if n <= 1       => 0,
 963             n if n <= 1 << 8  => 1,
 964             n if n <= 1 << 16 => 2,
 965             n if n <= 1 << 32 => 4,
 966             _                 => 8,
 967         };
 968         Repr::Aggregate {
 969             discr_size: discr_size,
 970             size: max_variant_size + discr_size,
 971             variants: variants,
 972         }
 973     }
 974
 975     pub fn read_primval(&mut self, ptr: Pointer, ty: ty::Ty<'tcx>) -> EvalResult<PrimVal> {
 976         use syntax::ast::{IntTy, UintTy};
 977         let val = match ty.sty {
 978             ty::TyBool              => PrimVal::Bool(try!(self.memory.read_bool(ptr))),
 979             ty::TyInt(IntTy::I8)    => PrimVal::I8(try!(self.memory.read_int(ptr, 1)) as i8),
 980             ty::TyInt(IntTy::I16)   => PrimVal::I16(try!(self.memory.read_int(ptr, 2)) as i16),
 981             ty::TyInt(IntTy::I32)   => PrimVal::I32(try!(self.memory.read_int(ptr, 4)) as i32),
 982             ty::TyInt(IntTy::I64)   => PrimVal::I64(try!(self.memory.read_int(ptr, 8)) as i64),
 983             ty::TyUint(UintTy::U8)  => PrimVal::U8(try!(self.memory.read_uint(ptr, 1)) as u8),
 984             ty::TyUint(UintTy::U16) => PrimVal::U16(try!(self.memory.read_uint(ptr, 2)) as u16),
 985             ty::TyUint(UintTy::U32) => PrimVal::U32(try!(self.memory.read_uint(ptr, 4)) as u32),
 986             ty::TyUint(UintTy::U64) => PrimVal::U64(try!(self.memory.read_uint(ptr, 8)) as u64),
 987
 988             // TODO(tsion): Pick the PrimVal dynamically.
 989             ty::TyInt(IntTy::Is)   => PrimVal::I64(try!(self.memory.read_isize(ptr))),
 990             ty::TyUint(UintTy::Us) => PrimVal::U64(try!(self.memory.read_usize(ptr))),
 991
 992             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 993             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
 994                 if self.type_is_sized(ty) {
 995                     match self.memory.read_ptr(ptr) {
 996                         Ok(p) => PrimVal::AbstractPtr(p),
 997                         Err(EvalError::ReadBytesAsPointer) => {
 998                             let n = try!(self.memory.read_usize(ptr));
 999                             PrimVal::IntegerPtr(n)
1000                         }
1001                         Err(e) => return Err(e),
1002                     }
1003                 } else {
1004                     panic!("unimplemented: primitive read of fat pointer type: {:?}", ty);
1005                 }
1006             }
1007
1008             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1009         };
1010         Ok(val)
1011     }
1012
1013     fn frame(&self) -> &Frame<'a, 'tcx> {
1014         self.stack.last().expect("no call frames exist")
1015     }
1016
1017     fn frame_mut(&mut self) -> &mut Frame<'a, 'tcx> {
1018         self.stack.last_mut().expect("no call frames exist")
1019     }
1020
1021     fn mir(&self) -> &mir::Mir<'tcx> {
1022         &self.frame().mir
1023     }
1024
1025     fn substs(&self) -> &'tcx Substs<'tcx> {
1026         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
1027     }
1028
1029     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
1030         match self.tcx.map.as_local_node_id(def_id) {
1031             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
1032             None => {
1033                 let mut mir_cache = self.mir_cache.borrow_mut();
1034                 if let Some(mir) = mir_cache.get(&def_id) {
1035                     return CachedMir::Owned(mir.clone());
1036                 }
1037
1038                 use rustc::middle::cstore::CrateStore;
1039                 let cs = &self.tcx.sess.cstore;
1040                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1041                     panic!("no mir for {:?}", def_id);
1042                 });
1043                 let cached = Rc::new(mir);
1044                 mir_cache.insert(def_id, cached.clone());
1045                 CachedMir::Owned(cached)
1046             }
1047         }
1048     }
1049
1050     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1051         // Do the initial selection for the obligation. This yields the shallow result we are
1052         // looking for -- that is, what specific impl.
1053         let infcx = infer::normalizing_infer_ctxt(self.tcx, &self.tcx.tables, ProjectionMode::Any);
1054         let mut selcx = traits::SelectionContext::new(&infcx);
1055
1056         let obligation = traits::Obligation::new(
1057             traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1058             trait_ref.to_poly_trait_predicate(),
1059         );
1060         let selection = selcx.select(&obligation).unwrap().unwrap();
1061
1062         // Currently, we use a fulfillment context to completely resolve all nested obligations.
1063         // This is because they can inform the inference of the impl's type parameters.
1064         let mut fulfill_cx = traits::FulfillmentContext::new();
1065         let vtable = selection.map(|predicate| {
1066             fulfill_cx.register_predicate_obligation(&infcx, predicate);
1067         });
1068         let vtable = infer::drain_fulfillment_cx_or_panic(
1069             DUMMY_SP, &infcx, &mut fulfill_cx, &vtable
1070         );
1071
1072         vtable
1073     }
1074
1075     /// Trait method, which has to be resolved to an impl method.
1076     pub fn trait_method(&self, def_id: DefId, substs: &'tcx Substs<'tcx>)
1077         -> (DefId, &'tcx Substs<'tcx>)
1078     {
1079         let method_item = self.tcx.impl_or_trait_item(def_id);
1080         let trait_id = method_item.container().id();
1081         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1082         match self.fulfill_obligation(trait_ref) {
1083             traits::VtableImpl(vtable_impl) => {
1084                 let impl_did = vtable_impl.impl_def_id;
1085                 let mname = self.tcx.item_name(def_id);
1086                 // Create a concatenated set of substitutions which includes those from the impl
1087                 // and those from the method:
1088                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1089                 let substs = self.tcx.mk_substs(impl_substs);
1090                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1091
1092                 (mth.method.def_id, mth.substs)
1093             }
1094
1095             traits::VtableClosure(vtable_closure) =>
1096                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1097
1098             traits::VtableFnPointer(_fn_ty) => {
1099                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1100                 unimplemented!()
1101                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1102
1103                 // let method_ty = def_ty(tcx, def_id, substs);
1104                 // let fn_ptr_ty = match method_ty.sty {
1105                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1106                 //     _ => unreachable!("expected fn item type, found {}",
1107                 //                       method_ty)
1108                 // };
1109                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1110             }
1111
1112             traits::VtableObject(ref _data) => {
1113                 unimplemented!()
1114                 // Callee {
1115                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1116                 //                   tcx, data, def_id)),
1117                 //                   ty: def_ty(tcx, def_id, substs)
1118                 // }
1119             }
1120             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1121         }
1122     }
1123 }
1124
1125 fn pointee_type<'tcx>(ptr_ty: ty::Ty<'tcx>) -> Option<ty::Ty<'tcx>> {
1126     match ptr_ty.sty {
1127         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1128         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1129         ty::TyBox(ty) => {
1130             Some(ty)
1131         }
1132         _ => None,
1133     }
1134 }
1135
1136 impl Lvalue {
1137     fn to_ptr(self) -> Pointer {
1138         assert_eq!(self.extra, LvalueExtra::None);
1139         self.ptr
1140     }
1141 }
1142
1143 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1144     type Target = mir::Mir<'tcx>;
1145     fn deref(&self) -> &mir::Mir<'tcx> {
1146         match *self {
1147             CachedMir::Ref(r) => r,
1148             CachedMir::Owned(ref rc) => &rc,
1149         }
1150     }
1151 }
1152
1153 #[derive(Debug)]
1154 pub struct ImplMethod<'tcx> {
1155     pub method: Rc<ty::Method<'tcx>>,
1156     pub substs: &'tcx Substs<'tcx>,
1157     pub is_provided: bool,
1158 }
1159
1160 /// Locates the applicable definition of a method, given its name.
1161 pub fn get_impl_method<'tcx>(
1162     tcx: &TyCtxt<'tcx>,
1163     impl_def_id: DefId,
1164     substs: &'tcx Substs<'tcx>,
1165     name: ast::Name,
1166 ) -> ImplMethod<'tcx> {
1167     assert!(!substs.types.needs_infer());
1168
1169     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1170     let trait_def = tcx.lookup_trait_def(trait_def_id);
1171     let infcx = infer::normalizing_infer_ctxt(tcx, &tcx.tables, ProjectionMode::Any);
1172
1173     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1174         Some(node_item) => {
1175             ImplMethod {
1176                 method: node_item.item,
1177                 substs: traits::translate_substs(&infcx, impl_def_id, substs, node_item.node),
1178                 is_provided: node_item.node.is_from_trait(),
1179             }
1180         }
1181         None => {
1182             bug!("method {:?} not found in {:?}", name, impl_def_id);
1183         }
1184     }
1185 }
1186
1187 pub fn interpret_start_points<'tcx>(tcx: &TyCtxt<'tcx>, mir_map: &MirMap<'tcx>) {
1188     for (&id, mir) in &mir_map.map {
1189         for attr in tcx.map.attrs(id) {
1190             use syntax::attr::AttrMetaMethods;
1191             if attr.check_name("miri_run") {
1192                 let item = tcx.map.expect_item(id);
1193
1194                 println!("Interpreting: {}", item.name);
1195
1196                 let repr_arena = TypedArena::new();
1197                 let mut miri = Interpreter::new(tcx, mir_map, &repr_arena);
1198                 let return_ptr = match mir.return_ty {
1199                     ty::FnConverging(ty) => {
1200                         let size = miri.type_size(ty);
1201                         Some(miri.memory.allocate(size))
1202                     }
1203                     ty::FnDiverging => None,
1204                 };
1205                 let substs = miri.tcx.mk_substs(Substs::empty());
1206                 miri.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
1207                 if let Err(_e) = miri.run() {
1208                     // TODO(tsion): Detect whether the error was already reported or not.
1209                     // tcx.sess.err(&e.to_string());
1210                 } else if let Some(ret) = return_ptr {
1211                     miri.memory.dump(ret.alloc_id);
1212                 }
1213                 println!("");
1214             }
1215         }
1216     }
1217 }