src/interpreter.rs

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