src/interpreter/mod.rs

   1 use rustc::middle::const_val;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::mir_map::MirMap;
   4 use rustc::mir::repr as mir;
   5 use rustc::traits::{self, ProjectionMode};
   6 use rustc::ty::fold::TypeFoldable;
   7 use rustc::ty::layout::{self, Layout, Size};
   8 use rustc::ty::subst::{self, Subst, Substs};
   9 use rustc::ty::{self, Ty, TyCtxt};
  10 use rustc::util::nodemap::DefIdMap;
  11 use std::cell::RefCell;
  12 use std::ops::{Deref, DerefMut};
  13 use std::rc::Rc;
  14 use std::{iter, mem};
  15 use syntax::ast;
  16 use syntax::attr;
  17 use syntax::codemap::{self, DUMMY_SP};
  18
  19 use error::{EvalError, EvalResult};
  20 use memory::{Memory, Pointer};
  21 use primval::{self, PrimVal};
  22
  23 use std::collections::HashMap;
  24
  25 mod stepper;
  26
  27 struct GlobalEvalContext<'a, 'tcx: 'a> {
  28     /// The results of the type checker, from rustc.
  29     tcx: TyCtxt<'a, 'tcx, '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     /// The virtual memory system.
  38     memory: Memory,
  39
  40     /// Precomputed statics, constants and promoteds
  41     statics: HashMap<ConstantId<'tcx>, Pointer>,
  42 }
  43
  44 struct FnEvalContext<'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> {
  45     gecx: &'a mut GlobalEvalContext<'b, 'tcx>,
  46
  47     /// The virtual call stack.
  48     stack: Vec<Frame<'mir, 'tcx>>,
  49 }
  50
  51 impl<'a, 'b, 'mir, 'tcx> Deref for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  52     type Target = GlobalEvalContext<'b, 'tcx>;
  53     fn deref(&self) -> &Self::Target {
  54         self.gecx
  55     }
  56 }
  57
  58 impl<'a, 'b, 'mir, 'tcx> DerefMut for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  59     fn deref_mut(&mut self) -> &mut Self::Target {
  60         self.gecx
  61     }
  62 }
  63
  64 /// A stack frame.
  65 struct Frame<'a, 'tcx: 'a> {
  66     /// The def_id of the current function
  67     def_id: DefId,
  68
  69     /// The span of the call site
  70     span: codemap::Span,
  71
  72     /// type substitutions for the current function invocation
  73     substs: &'tcx Substs<'tcx>,
  74
  75     /// The MIR for the function called on this frame.
  76     mir: CachedMir<'a, 'tcx>,
  77
  78     /// The block that is currently executed (or will be executed after the above call stacks return)
  79     next_block: mir::BasicBlock,
  80
  81     /// A pointer for writing the return value of the current call if it's not a diverging call.
  82     return_ptr: Option<Pointer>,
  83
  84     /// The list of locals for the current function, stored in order as
  85     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  86     /// and the temporaries at `self.temp_offset`.
  87     locals: Vec<Pointer>,
  88
  89     /// The offset of the first variable in `self.locals`.
  90     var_offset: usize,
  91
  92     /// The offset of the first temporary in `self.locals`.
  93     temp_offset: usize,
  94
  95     /// The index of the currently evaluated statment
  96     stmt: usize,
  97 }
  98
  99 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 100 struct Lvalue {
 101     ptr: Pointer,
 102     extra: LvalueExtra,
 103 }
 104
 105 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 106 enum LvalueExtra {
 107     None,
 108     Length(u64),
 109     // TODO(solson): Vtable(memory::AllocId),
 110     DowncastVariant(usize),
 111 }
 112
 113 #[derive(Clone)]
 114 enum CachedMir<'mir, 'tcx: 'mir> {
 115     Ref(&'mir mir::Mir<'tcx>),
 116     Owned(Rc<mir::Mir<'tcx>>)
 117 }
 118
 119 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 120 enum TerminatorTarget {
 121     /// Make a local jump to the next block
 122     Block,
 123
 124     /// Start executing from the new current frame. (For function calls.)
 125     Call,
 126
 127     /// Stop executing the current frame and resume the previous frame.
 128     Return,
 129 }
 130
 131 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 132 struct ConstantId<'tcx> {
 133     def_id: DefId,
 134     substs: &'tcx Substs<'tcx>,
 135     kind: ConstantKind,
 136 }
 137
 138 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 139 enum ConstantKind {
 140     Promoted(usize),
 141     Static,
 142 }
 143
 144 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 145     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 146         GlobalEvalContext {
 147             tcx: tcx,
 148             mir_map: mir_map,
 149             mir_cache: RefCell::new(DefIdMap()),
 150             memory: Memory::new(tcx.sess
 151                                    .target
 152                                    .uint_type
 153                                    .bit_width()
 154                                    .expect("Session::target::uint_type was usize")/8),
 155             statics: HashMap::new(),
 156         }
 157     }
 158
 159     fn call(&mut self, mir: &mir::Mir<'tcx>, def_id: DefId) -> EvalResult<Option<Pointer>> {
 160         let substs = self.tcx.mk_substs(subst::Substs::empty());
 161         let return_ptr = self.alloc_ret_ptr(mir.return_ty, substs);
 162
 163         let mut nested_fecx = FnEvalContext::new(self);
 164
 165         nested_fecx.push_stack_frame(def_id, mir.span, CachedMir::Ref(mir), substs, None);
 166
 167         nested_fecx.frame_mut().return_ptr = return_ptr;
 168
 169         nested_fecx.run()?;
 170         Ok(return_ptr)
 171     }
 172
 173     fn alloc_ret_ptr(&mut self, output_ty: ty::FnOutput<'tcx>, substs: &'tcx Substs<'tcx>) -> Option<Pointer> {
 174         match output_ty {
 175             ty::FnConverging(ty) => {
 176                 let size = self.type_size(ty, substs);
 177                 Some(self.memory.allocate(size))
 178             }
 179             ty::FnDiverging => None,
 180         }
 181     }
 182
 183     // TODO(solson): Try making const_to_primval instead.
 184     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
 185         use rustc::middle::const_val::ConstVal::*;
 186         match *const_val {
 187             Float(_f) => unimplemented!(),
 188             Integral(int) => {
 189                 // TODO(solson): Check int constant type.
 190                 let ptr = self.memory.allocate(8);
 191                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
 192                 Ok(ptr)
 193             }
 194             Str(ref s) => {
 195                 let psize = self.memory.pointer_size;
 196                 let static_ptr = self.memory.allocate(s.len());
 197                 let ptr = self.memory.allocate(psize * 2);
 198                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
 199                 self.memory.write_ptr(ptr, static_ptr)?;
 200                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
 201                 Ok(ptr)
 202             }
 203             ByteStr(ref bs) => {
 204                 let psize = self.memory.pointer_size;
 205                 let static_ptr = self.memory.allocate(bs.len());
 206                 let ptr = self.memory.allocate(psize);
 207                 self.memory.write_bytes(static_ptr, bs)?;
 208                 self.memory.write_ptr(ptr, static_ptr)?;
 209                 Ok(ptr)
 210             }
 211             Bool(b) => {
 212                 let ptr = self.memory.allocate(1);
 213                 self.memory.write_bool(ptr, b)?;
 214                 Ok(ptr)
 215             }
 216             Char(_c)          => unimplemented!(),
 217             Struct(_node_id)  => unimplemented!(),
 218             Tuple(_node_id)   => unimplemented!(),
 219             Function(_def_id) => unimplemented!(),
 220             Array(_, _)       => unimplemented!(),
 221             Repeat(_, _)      => unimplemented!(),
 222             Dummy             => unimplemented!(),
 223         }
 224     }
 225
 226     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
 227         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
 228     }
 229
 230     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
 231         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
 232     }
 233
 234     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
 235         // Do the initial selection for the obligation. This yields the shallow result we are
 236         // looking for -- that is, what specific impl.
 237         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 238             let mut selcx = traits::SelectionContext::new(&infcx);
 239
 240             let obligation = traits::Obligation::new(
 241                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
 242                 trait_ref.to_poly_trait_predicate(),
 243             );
 244             let selection = selcx.select(&obligation).unwrap().unwrap();
 245
 246             // Currently, we use a fulfillment context to completely resolve all nested obligations.
 247             // This is because they can inform the inference of the impl's type parameters.
 248             let mut fulfill_cx = traits::FulfillmentContext::new();
 249             let vtable = selection.map(|predicate| {
 250                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
 251             });
 252             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
 253         })
 254     }
 255
 256     /// Trait method, which has to be resolved to an impl method.
 257     pub fn trait_method(
 258         &self,
 259         def_id: DefId,
 260         substs: &'tcx Substs<'tcx>
 261     ) -> (DefId, &'tcx Substs<'tcx>) {
 262         let method_item = self.tcx.impl_or_trait_item(def_id);
 263         let trait_id = method_item.container().id();
 264         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
 265         match self.fulfill_obligation(trait_ref) {
 266             traits::VtableImpl(vtable_impl) => {
 267                 let impl_did = vtable_impl.impl_def_id;
 268                 let mname = self.tcx.item_name(def_id);
 269                 // Create a concatenated set of substitutions which includes those from the impl
 270                 // and those from the method:
 271                 let impl_substs = vtable_impl.substs.with_method_from(substs);
 272                 let substs = self.tcx.mk_substs(impl_substs);
 273                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
 274
 275                 (mth.method.def_id, mth.substs)
 276             }
 277
 278             traits::VtableClosure(vtable_closure) =>
 279                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
 280
 281             traits::VtableFnPointer(_fn_ty) => {
 282                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
 283                 unimplemented!()
 284                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
 285
 286                 // let method_ty = def_ty(tcx, def_id, substs);
 287                 // let fn_ptr_ty = match method_ty.sty {
 288                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
 289                 //     _ => unreachable!("expected fn item type, found {}",
 290                 //                       method_ty)
 291                 // };
 292                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
 293             }
 294
 295             traits::VtableObject(ref _data) => {
 296                 unimplemented!()
 297                 // Callee {
 298                 //     data: Virtual(traits::get_vtable_index_of_object_method(
 299                 //                   tcx, data, def_id)),
 300                 //                   ty: def_ty(tcx, def_id, substs)
 301                 // }
 302             }
 303             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
 304         }
 305     }
 306
 307     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
 308         match self.tcx.map.as_local_node_id(def_id) {
 309             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
 310             None => {
 311                 let mut mir_cache = self.mir_cache.borrow_mut();
 312                 if let Some(mir) = mir_cache.get(&def_id) {
 313                     return CachedMir::Owned(mir.clone());
 314                 }
 315
 316                 let cs = &self.tcx.sess.cstore;
 317                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
 318                     panic!("no mir for {:?}", def_id);
 319                 });
 320                 let cached = Rc::new(mir);
 321                 mir_cache.insert(def_id, cached.clone());
 322                 CachedMir::Owned(cached)
 323             }
 324         }
 325     }
 326
 327     fn monomorphize(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
 328         let substituted = ty.subst(self.tcx, substs);
 329         self.tcx.normalize_associated_type(&substituted)
 330     }
 331
 332     fn type_size(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> usize {
 333         self.type_layout(ty, substs).size(&self.tcx.data_layout).bytes() as usize
 334     }
 335
 336     fn type_layout(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> &'tcx Layout {
 337         // TODO(solson): Is this inefficient? Needs investigation.
 338         let ty = self.monomorphize(ty, substs);
 339
 340         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 341             // TODO(solson): Report this error properly.
 342             ty.layout(&infcx).unwrap()
 343         })
 344     }
 345 }
 346
 347 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 348     fn new(gecx: &'a mut GlobalEvalContext<'b, 'tcx>) -> Self {
 349         FnEvalContext {
 350             gecx: gecx,
 351             stack: Vec::new(),
 352         }
 353     }
 354
 355     #[inline(never)]
 356     #[cold]
 357     fn report(&self, e: &EvalError) {
 358         let stmt = self.frame().stmt;
 359         let block = self.basic_block();
 360         let span = if stmt < block.statements.len() {
 361             block.statements[stmt].span
 362         } else {
 363             block.terminator().span
 364         };
 365         let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 366         for &Frame{ def_id, substs, span, .. } in self.stack.iter().rev() {
 367             // FIXME(solson): Find a way to do this without this Display impl hack.
 368             use rustc::util::ppaux;
 369             use std::fmt;
 370             struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 371             impl<'tcx> fmt::Display for Instance<'tcx> {
 372                 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 373                     ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 374                         |tcx| tcx.lookup_item_type(self.0).generics)
 375                 }
 376             }
 377             err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 378         }
 379         err.emit();
 380     }
 381
 382     fn maybe_report<T>(&self, r: EvalResult<T>) -> EvalResult<T> {
 383         if let Err(ref e) = r {
 384             self.report(e);
 385         }
 386         r
 387     }
 388
 389     fn run(&mut self) -> EvalResult<()> {
 390         let mut stepper = stepper::Stepper::new(self);
 391         let mut done = false;
 392         while !done {
 393             use self::stepper::Event::*;
 394             stepper.step(|event| match event {
 395                 Block(b) => trace!("// {:?}", b),
 396                 Assignment(a) => trace!("{:?}", a),
 397                 Terminator(t) => trace!("{:?}", t.kind),
 398                 Done => done = true,
 399                 _ => {},
 400             })?;
 401         }
 402         Ok(())
 403     }
 404
 405     fn push_stack_frame(&mut self, def_id: DefId, span: codemap::Span, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
 406         return_ptr: Option<Pointer>)
 407     {
 408         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 409         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 410         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 411
 412         let num_args = mir.arg_decls.len();
 413         let num_vars = mir.var_decls.len();
 414
 415         ::log_settings::settings().indentation += 1;
 416
 417         self.stack.push(Frame {
 418             mir: mir.clone(),
 419             next_block: mir::START_BLOCK,
 420             return_ptr: return_ptr,
 421             locals: Vec::new(),
 422             var_offset: num_args,
 423             temp_offset: num_args + num_vars,
 424             span: span,
 425             def_id: def_id,
 426             substs: substs,
 427             stmt: 0,
 428         });
 429
 430         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 431             let size = self.type_size(ty);
 432             self.memory.allocate(size)
 433         }).collect();
 434
 435         self.frame_mut().locals = locals;
 436     }
 437
 438     fn pop_stack_frame(&mut self) {
 439         ::log_settings::settings().indentation -= 1;
 440         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 441         // TODO(solson): Deallocate local variables.
 442     }
 443
 444     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 445             -> EvalResult<TerminatorTarget> {
 446         use rustc::mir::repr::TerminatorKind::*;
 447         let target = match terminator.kind {
 448             Return => TerminatorTarget::Return,
 449
 450             Goto { target } => {
 451                 self.frame_mut().next_block = target;
 452                 TerminatorTarget::Block
 453             },
 454
 455             If { ref cond, targets: (then_target, else_target) } => {
 456                 let cond_ptr = self.eval_operand(cond)?;
 457                 let cond_val = self.memory.read_bool(cond_ptr)?;
 458                 self.frame_mut().next_block = if cond_val { then_target } else { else_target };
 459                 TerminatorTarget::Block
 460             }
 461
 462             SwitchInt { ref discr, ref values, ref targets, .. } => {
 463                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 464                 let discr_size = self
 465                     .type_layout(self.lvalue_ty(discr))
 466                     .size(&self.tcx.data_layout)
 467                     .bytes() as usize;
 468                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 469
 470                 // Branch to the `otherwise` case by default, if no match is found.
 471                 let mut target_block = targets[targets.len() - 1];
 472
 473                 for (index, val_const) in values.iter().enumerate() {
 474                     let ptr = self.const_to_ptr(val_const)?;
 475                     let val = self.memory.read_uint(ptr, discr_size)?;
 476                     if discr_val == val {
 477                         target_block = targets[index];
 478                         break;
 479                     }
 480                 }
 481
 482                 self.frame_mut().next_block = target_block;
 483                 TerminatorTarget::Block
 484             }
 485
 486             Switch { ref discr, ref targets, adt_def } => {
 487                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 488                 let adt_ty = self.lvalue_ty(discr);
 489                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 490                 let matching = adt_def.variants.iter()
 491                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 492
 493                 match matching {
 494                     Some(i) => {
 495                         self.frame_mut().next_block = targets[i];
 496                         TerminatorTarget::Block
 497                     },
 498                     None => return Err(EvalError::InvalidDiscriminant),
 499                 }
 500             }
 501
 502             Call { ref func, ref args, ref destination, .. } => {
 503                 let mut return_ptr = None;
 504                 if let Some((ref lv, target)) = *destination {
 505                     self.frame_mut().next_block = target;
 506                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 507                 }
 508
 509                 let func_ty = self.operand_ty(func);
 510                 match func_ty.sty {
 511                     ty::TyFnDef(def_id, substs, fn_ty) => {
 512                         use syntax::abi::Abi;
 513                         match fn_ty.abi {
 514                             Abi::RustIntrinsic => {
 515                                 let name = self.tcx.item_name(def_id).as_str();
 516                                 match fn_ty.sig.0.output {
 517                                     ty::FnConverging(ty) => {
 518                                         let size = self.type_size(ty);
 519                                         let ret = return_ptr.unwrap();
 520                                         self.call_intrinsic(&name, substs, args, ret, size)?
 521                                     }
 522                                     ty::FnDiverging => unimplemented!(),
 523                                 }
 524                             }
 525
 526                             Abi::C => {
 527                                 match fn_ty.sig.0.output {
 528                                     ty::FnConverging(ty) => {
 529                                         let size = self.type_size(ty);
 530                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 531                                     }
 532                                     ty::FnDiverging => unimplemented!(),
 533                                 }
 534                             }
 535
 536                             Abi::Rust | Abi::RustCall => {
 537                                 // TODO(solson): Adjust the first argument when calling a Fn or
 538                                 // FnMut closure via FnOnce::call_once.
 539
 540                                 // Only trait methods can have a Self parameter.
 541                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 542                                     self.trait_method(def_id, substs)
 543                                 } else {
 544                                     (def_id, substs)
 545                                 };
 546
 547                                 let mut arg_srcs = Vec::new();
 548                                 for arg in args {
 549                                     let src = self.eval_operand(arg)?;
 550                                     let src_ty = self.operand_ty(arg);
 551                                     arg_srcs.push((src, src_ty));
 552                                 }
 553
 554                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 555                                     arg_srcs.pop();
 556                                     let last_arg = args.last().unwrap();
 557                                     let last = self.eval_operand(last_arg)?;
 558                                     let last_ty = self.operand_ty(last_arg);
 559                                     let last_layout = self.type_layout(last_ty);
 560                                     match (&last_ty.sty, last_layout) {
 561                                         (&ty::TyTuple(fields),
 562                                          &Layout::Univariant { ref variant, .. }) => {
 563                                             let offsets = iter::once(0)
 564                                                 .chain(variant.offset_after_field.iter()
 565                                                     .map(|s| s.bytes()));
 566                                             for (offset, ty) in offsets.zip(fields) {
 567                                                 let src = last.offset(offset as isize);
 568                                                 arg_srcs.push((src, ty));
 569                                             }
 570                                         }
 571                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 572                                     }
 573                                 }
 574
 575                                 let mir = self.load_mir(resolved_def_id);
 576                                 self.push_stack_frame(def_id, terminator.span, mir, resolved_substs, return_ptr);
 577
 578                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 579                                     let dest = self.frame().locals[i];
 580                                     self.move_(src, dest, src_ty)?;
 581                                 }
 582
 583                                 TerminatorTarget::Call
 584                             }
 585
 586                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 587                         }
 588                     }
 589
 590                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 591                 }
 592             }
 593
 594             Drop { ref value, target, .. } => {
 595                 let ptr = self.eval_lvalue(value)?.to_ptr();
 596                 let ty = self.lvalue_ty(value);
 597                 self.drop(ptr, ty)?;
 598                 self.frame_mut().next_block = target;
 599                 TerminatorTarget::Block
 600             }
 601
 602             Resume => unimplemented!(),
 603         };
 604
 605         Ok(target)
 606     }
 607
 608     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 609         if !self.type_needs_drop(ty) {
 610             debug!("no need to drop {:?}", ty);
 611             return Ok(());
 612         }
 613         trace!("-need to drop {:?}", ty);
 614
 615         // TODO(solson): Call user-defined Drop::drop impls.
 616
 617         match ty.sty {
 618             ty::TyBox(contents_ty) => {
 619                 match self.memory.read_ptr(ptr) {
 620                     Ok(contents_ptr) => {
 621                         self.drop(contents_ptr, contents_ty)?;
 622                         trace!("-deallocating box");
 623                         self.memory.deallocate(contents_ptr)?;
 624                     }
 625                     Err(EvalError::ReadBytesAsPointer) => {
 626                         let size = self.memory.pointer_size;
 627                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 628                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 629                             return Ok(());
 630                         } else {
 631                             return Err(EvalError::ReadBytesAsPointer);
 632                         }
 633                     }
 634                     Err(e) => return Err(e),
 635                 }
 636             }
 637
 638             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 639             _ => {}
 640         }
 641
 642         // Filling drop.
 643         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 644         let size = self.type_size(ty);
 645         self.memory.drop_fill(ptr, size)?;
 646
 647         Ok(())
 648     }
 649
 650     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 651         use rustc::ty::layout::Layout::*;
 652         let adt_layout = self.type_layout(adt_ty);
 653
 654         let discr_val = match *adt_layout {
 655             General { discr, .. } | CEnum { discr, .. } => {
 656                 let discr_size = discr.size().bytes();
 657                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 658             }
 659
 660             RawNullablePointer { nndiscr, .. } => {
 661                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 662             }
 663
 664             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 665                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 666                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 667                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 668             }
 669
 670             // The discriminant_value intrinsic returns 0 for non-sum types.
 671             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 672             Vector { .. } => 0,
 673         };
 674
 675         Ok(discr_val)
 676     }
 677
 678     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 679         let not_null = match self.memory.read_usize(ptr) {
 680             Ok(0) => false,
 681             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 682             Err(e) => return Err(e),
 683         };
 684         assert!(nndiscr == 0 || nndiscr == 1);
 685         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 686     }
 687
 688     fn call_intrinsic(
 689         &mut self,
 690         name: &str,
 691         substs: &'tcx Substs<'tcx>,
 692         args: &[mir::Operand<'tcx>],
 693         dest: Pointer,
 694         dest_size: usize
 695     ) -> EvalResult<TerminatorTarget> {
 696         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 697             .map(|arg| self.eval_operand(arg))
 698             .collect();
 699         let args = args_res?;
 700
 701         match name {
 702             // FIXME(solson): Handle different integer types correctly.
 703             "add_with_overflow" => {
 704                 let ty = *substs.types.get(subst::FnSpace, 0);
 705                 let size = self.type_size(ty);
 706                 let left = self.memory.read_int(args[0], size)?;
 707                 let right = self.memory.read_int(args[1], size)?;
 708                 let (n, overflowed) = unsafe {
 709                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 710                 };
 711                 self.memory.write_int(dest, n, size)?;
 712                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 713             }
 714
 715             "assume" => {}
 716
 717             "copy_nonoverlapping" => {
 718                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 719                 let elem_size = self.type_size(elem_ty);
 720                 let src = self.memory.read_ptr(args[0])?;
 721                 let dest = self.memory.read_ptr(args[1])?;
 722                 let count = self.memory.read_isize(args[2])?;
 723                 self.memory.copy(src, dest, count as usize * elem_size)?;
 724             }
 725
 726             "discriminant_value" => {
 727                 let ty = *substs.types.get(subst::FnSpace, 0);
 728                 let adt_ptr = self.memory.read_ptr(args[0])?;
 729                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 730                 self.memory.write_uint(dest, discr_val, dest_size)?;
 731             }
 732
 733             "forget" => {
 734                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 735                 let arg_size = self.type_size(arg_ty);
 736                 self.memory.drop_fill(args[0], arg_size)?;
 737             }
 738
 739             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 740
 741             "min_align_of" => {
 742                 self.memory.write_int(dest, 1, dest_size)?;
 743             }
 744
 745             "move_val_init" => {
 746                 let ty = *substs.types.get(subst::FnSpace, 0);
 747                 let ptr = self.memory.read_ptr(args[0])?;
 748                 self.move_(args[1], ptr, ty)?;
 749             }
 750
 751             // FIXME(solson): Handle different integer types correctly.
 752             "mul_with_overflow" => {
 753                 let ty = *substs.types.get(subst::FnSpace, 0);
 754                 let size = self.type_size(ty);
 755                 let left = self.memory.read_int(args[0], size)?;
 756                 let right = self.memory.read_int(args[1], size)?;
 757                 let (n, overflowed) = unsafe {
 758                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 759                 };
 760                 self.memory.write_int(dest, n, size)?;
 761                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 762             }
 763
 764             "offset" => {
 765                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 766                 let pointee_size = self.type_size(pointee_ty) as isize;
 767                 let ptr_arg = args[0];
 768                 let offset = self.memory.read_isize(args[1])?;
 769
 770                 match self.memory.read_ptr(ptr_arg) {
 771                     Ok(ptr) => {
 772                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 773                         self.memory.write_ptr(dest, result_ptr)?;
 774                     }
 775                     Err(EvalError::ReadBytesAsPointer) => {
 776                         let addr = self.memory.read_isize(ptr_arg)?;
 777                         let result_addr = addr + offset * pointee_size as i64;
 778                         self.memory.write_isize(dest, result_addr)?;
 779                     }
 780                     Err(e) => return Err(e),
 781                 }
 782             }
 783
 784             // FIXME(solson): Handle different integer types correctly. Use primvals?
 785             "overflowing_sub" => {
 786                 let ty = *substs.types.get(subst::FnSpace, 0);
 787                 let size = self.type_size(ty);
 788                 let left = self.memory.read_int(args[0], size)?;
 789                 let right = self.memory.read_int(args[1], size)?;
 790                 let n = left.wrapping_sub(right);
 791                 self.memory.write_int(dest, n, size)?;
 792             }
 793
 794             "size_of" => {
 795                 let ty = *substs.types.get(subst::FnSpace, 0);
 796                 let size = self.type_size(ty) as u64;
 797                 self.memory.write_uint(dest, size, dest_size)?;
 798             }
 799
 800             "size_of_val" => {
 801                 let ty = *substs.types.get(subst::FnSpace, 0);
 802                 if self.type_is_sized(ty) {
 803                     let size = self.type_size(ty) as u64;
 804                     self.memory.write_uint(dest, size, dest_size)?;
 805                 } else {
 806                     match ty.sty {
 807                         ty::TySlice(_) | ty::TyStr => {
 808                             let elem_ty = ty.sequence_element_type(self.tcx);
 809                             let elem_size = self.type_size(elem_ty) as u64;
 810                             let ptr_size = self.memory.pointer_size as isize;
 811                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 812                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 813                         }
 814
 815                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 816                     }
 817                 }
 818             }
 819
 820             "transmute" => {
 821                 let ty = *substs.types.get(subst::FnSpace, 0);
 822                 self.move_(args[0], dest, ty)?;
 823             }
 824             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 825
 826             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 827         }
 828
 829         // Since we pushed no stack frame, the main loop will act
 830         // as if the call just completed and it's returning to the
 831         // current frame.
 832         Ok(TerminatorTarget::Call)
 833     }
 834
 835     fn call_c_abi(
 836         &mut self,
 837         def_id: DefId,
 838         args: &[mir::Operand<'tcx>],
 839         dest: Pointer,
 840         dest_size: usize,
 841     ) -> EvalResult<TerminatorTarget> {
 842         let name = self.tcx.item_name(def_id);
 843         let attrs = self.tcx.get_attrs(def_id);
 844         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 845             Some(ln) => ln.clone(),
 846             None => name.as_str(),
 847         };
 848
 849         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 850             .map(|arg| self.eval_operand(arg))
 851             .collect();
 852         let args = args_res?;
 853
 854         match &link_name[..] {
 855             "__rust_allocate" => {
 856                 let size = self.memory.read_usize(args[0])?;
 857                 let ptr = self.memory.allocate(size as usize);
 858                 self.memory.write_ptr(dest, ptr)?;
 859             }
 860
 861             "__rust_reallocate" => {
 862                 let ptr = self.memory.read_ptr(args[0])?;
 863                 let size = self.memory.read_usize(args[2])?;
 864                 self.memory.reallocate(ptr, size as usize)?;
 865                 self.memory.write_ptr(dest, ptr)?;
 866             }
 867
 868             "memcmp" => {
 869                 let left = self.memory.read_ptr(args[0])?;
 870                 let right = self.memory.read_ptr(args[1])?;
 871                 let n = self.memory.read_usize(args[2])? as usize;
 872
 873                 let result = {
 874                     let left_bytes = self.memory.read_bytes(left, n)?;
 875                     let right_bytes = self.memory.read_bytes(right, n)?;
 876
 877                     use std::cmp::Ordering::*;
 878                     match left_bytes.cmp(right_bytes) {
 879                         Less => -1,
 880                         Equal => 0,
 881                         Greater => 1,
 882                     }
 883                 };
 884
 885                 self.memory.write_int(dest, result, dest_size)?;
 886             }
 887
 888             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 889         }
 890
 891         // Since we pushed no stack frame, the main loop will act
 892         // as if the call just completed and it's returning to the
 893         // current frame.
 894         Ok(TerminatorTarget::Call)
 895     }
 896
 897     fn assign_fields<I: IntoIterator<Item = u64>>(
 898         &mut self,
 899         dest: Pointer,
 900         offsets: I,
 901         operands: &[mir::Operand<'tcx>],
 902     ) -> EvalResult<()> {
 903         for (offset, operand) in offsets.into_iter().zip(operands) {
 904             let src = self.eval_operand(operand)?;
 905             let src_ty = self.operand_ty(operand);
 906             let field_dest = dest.offset(offset as isize);
 907             self.move_(src, field_dest, src_ty)?;
 908         }
 909         Ok(())
 910     }
 911
 912     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 913         -> EvalResult<()>
 914     {
 915         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 916         let dest_ty = self.lvalue_ty(lvalue);
 917         let dest_layout = self.type_layout(dest_ty);
 918
 919         use rustc::mir::repr::Rvalue::*;
 920         match *rvalue {
 921             Use(ref operand) => {
 922                 let src = self.eval_operand(operand)?;
 923                 self.move_(src, dest, dest_ty)?;
 924             }
 925
 926             BinaryOp(bin_op, ref left, ref right) => {
 927                 let left_ptr = self.eval_operand(left)?;
 928                 let left_ty = self.operand_ty(left);
 929                 let left_val = self.read_primval(left_ptr, left_ty)?;
 930
 931                 let right_ptr = self.eval_operand(right)?;
 932                 let right_ty = self.operand_ty(right);
 933                 let right_val = self.read_primval(right_ptr, right_ty)?;
 934
 935                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 936                 self.memory.write_primval(dest, val)?;
 937             }
 938
 939             UnaryOp(un_op, ref operand) => {
 940                 let ptr = self.eval_operand(operand)?;
 941                 let ty = self.operand_ty(operand);
 942                 let val = self.read_primval(ptr, ty)?;
 943                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 944             }
 945
 946             Aggregate(ref kind, ref operands) => {
 947                 use rustc::ty::layout::Layout::*;
 948                 match *dest_layout {
 949                     Univariant { ref variant, .. } => {
 950                         let offsets = iter::once(0)
 951                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 952                         self.assign_fields(dest, offsets, operands)?;
 953                     }
 954
 955                     Array { .. } => {
 956                         let elem_size = match dest_ty.sty {
 957                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 958                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 959                                         kind, dest_ty),
 960                         };
 961                         let offsets = (0..).map(|i| i * elem_size);
 962                         self.assign_fields(dest, offsets, operands)?;
 963                     }
 964
 965                     General { discr, ref variants, .. } => {
 966                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 967                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 968                             let discr_size = discr.size().bytes() as usize;
 969                             self.memory.write_uint(dest, discr_val, discr_size)?;
 970
 971                             let offsets = variants[variant].offset_after_field.iter()
 972                                 .map(|s| s.bytes());
 973                             self.assign_fields(dest, offsets, operands)?;
 974                         } else {
 975                             panic!("tried to assign {:?} to Layout::General", kind);
 976                         }
 977                     }
 978
 979                     RawNullablePointer { nndiscr, .. } => {
 980                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 981                             if nndiscr == variant as u64 {
 982                                 assert_eq!(operands.len(), 1);
 983                                 let operand = &operands[0];
 984                                 let src = self.eval_operand(operand)?;
 985                                 let src_ty = self.operand_ty(operand);
 986                                 self.move_(src, dest, src_ty)?;
 987                             } else {
 988                                 assert_eq!(operands.len(), 0);
 989                                 self.memory.write_isize(dest, 0)?;
 990                             }
 991                         } else {
 992                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 993                         }
 994                     }
 995
 996                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
 997                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 998                             if nndiscr == variant as u64 {
 999                                 let offsets = iter::once(0)
1000                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
1001                                 try!(self.assign_fields(dest, offsets, operands));
1002                             } else {
1003                                 assert_eq!(operands.len(), 0);
1004                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
1005                                 let dest = dest.offset(offset.bytes() as isize);
1006                                 try!(self.memory.write_isize(dest, 0));
1007                             }
1008                         } else {
1009                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
1010                         }
1011                     }
1012
1013                     CEnum { discr, signed, .. } => {
1014                         assert_eq!(operands.len(), 0);
1015                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
1016                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
1017                             let size = discr.size().bytes() as usize;
1018
1019                             if signed {
1020                                 self.memory.write_int(dest, val as i64, size)?;
1021                             } else {
1022                                 self.memory.write_uint(dest, val, size)?;
1023                             }
1024                         } else {
1025                             panic!("tried to assign {:?} to Layout::CEnum", kind);
1026                         }
1027                     }
1028
1029                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
1030                 }
1031             }
1032
1033             Repeat(ref operand, _) => {
1034                 let (elem_size, length) = match dest_ty.sty {
1035                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
1036                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
1037                 };
1038
1039                 let src = self.eval_operand(operand)?;
1040                 for i in 0..length {
1041                     let elem_dest = dest.offset((i * elem_size) as isize);
1042                     self.memory.copy(src, elem_dest, elem_size)?;
1043                 }
1044             }
1045
1046             Len(ref lvalue) => {
1047                 let src = self.eval_lvalue(lvalue)?;
1048                 let ty = self.lvalue_ty(lvalue);
1049                 let len = match ty.sty {
1050                     ty::TyArray(_, n) => n as u64,
1051                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
1052                         n
1053                     } else {
1054                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
1055                     },
1056                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
1057                 };
1058                 self.memory.write_usize(dest, len)?;
1059             }
1060
1061             Ref(_, _, ref lvalue) => {
1062                 let lv = self.eval_lvalue(lvalue)?;
1063                 self.memory.write_ptr(dest, lv.ptr)?;
1064                 match lv.extra {
1065                     LvalueExtra::None => {},
1066                     LvalueExtra::Length(len) => {
1067                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
1068                         self.memory.write_usize(len_ptr, len)?;
1069                     }
1070                     LvalueExtra::DowncastVariant(..) =>
1071                         panic!("attempted to take a reference to an enum downcast lvalue"),
1072                 }
1073             }
1074
1075             Box(ty) => {
1076                 let size = self.type_size(ty);
1077                 let ptr = self.memory.allocate(size);
1078                 self.memory.write_ptr(dest, ptr)?;
1079             }
1080
1081             Cast(kind, ref operand, dest_ty) => {
1082                 let src = self.eval_operand(operand)?;
1083                 let src_ty = self.operand_ty(operand);
1084
1085                 use rustc::mir::repr::CastKind::*;
1086                 match kind {
1087                     Unsize => {
1088                         self.move_(src, dest, src_ty)?;
1089                         let src_pointee_ty = pointee_type(src_ty).unwrap();
1090                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
1091
1092                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
1093                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
1094                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
1095                                 self.memory.write_usize(len_ptr, length as u64)?;
1096                             }
1097
1098                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1099                         }
1100                     }
1101
1102                     Misc => {
1103                         // FIXME(solson): Wrong for almost everything.
1104                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
1105                         self.memory.copy(src, dest, size)?;
1106                     }
1107
1108                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1109                 }
1110             }
1111
1112             Slice { .. } => unimplemented!(),
1113             InlineAsm { .. } => unimplemented!(),
1114         }
1115
1116         Ok(())
1117     }
1118
1119     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
1120         // Skip the constant 0 at the start meant for LLVM GEP.
1121         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
1122
1123         // Handle the field index for the outer non-null variant.
1124         let inner_ty = match ty.sty {
1125             ty::TyEnum(adt_def, substs) => {
1126                 let variant = &adt_def.variants[nndiscr as usize];
1127                 let index = path.next().unwrap();
1128                 let field = &variant.fields[index];
1129                 field.ty(self.tcx, substs)
1130             }
1131             _ => panic!(
1132                 "non-enum for StructWrappedNullablePointer: {}",
1133                 ty,
1134             ),
1135         };
1136
1137         self.field_path_offset(inner_ty, path)
1138     }
1139
1140     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
1141         let mut offset = Size::from_bytes(0);
1142
1143         // Skip the initial 0 intended for LLVM GEP.
1144         for field_index in path {
1145             let field_offset = self.get_field_offset(ty, field_index)?;
1146             ty = self.get_field_ty(ty, field_index)?;
1147             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
1148         }
1149
1150         Ok(offset)
1151     }
1152
1153     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
1154         match ty.sty {
1155             ty::TyStruct(adt_def, substs) => {
1156                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
1157             }
1158
1159             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1160             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1161             ty::TyBox(ty) => {
1162                 assert_eq!(field_index, 0);
1163                 Ok(ty)
1164             }
1165             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
1166         }
1167     }
1168
1169     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
1170         let layout = self.type_layout(ty);
1171
1172         use rustc::ty::layout::Layout::*;
1173         match *layout {
1174             Univariant { .. } => {
1175                 assert_eq!(field_index, 0);
1176                 Ok(Size::from_bytes(0))
1177             }
1178             FatPointer { .. } => {
1179                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
1180                 Ok(Size::from_bytes(bytes as u64))
1181             }
1182             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
1183         }
1184     }
1185
1186     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
1187         use rustc::mir::repr::Operand::*;
1188         match *op {
1189             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
1190             Constant(mir::Constant { ref literal, .. }) => {
1191                 use rustc::mir::repr::Literal::*;
1192                 match *literal {
1193                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1194                     Item { def_id, substs } => {
1195                         let item_ty = self.tcx.lookup_item_type(def_id).subst(self.tcx, substs);
1196                         if item_ty.ty.is_fn() {
1197                             Err(EvalError::Unimplemented("unimplemented: mentions of function items".to_string()))
1198                         } else {
1199                             let cid = ConstantId {
1200                                 def_id: def_id,
1201                                 substs: substs,
1202                                 kind: ConstantKind::Static,
1203                             };
1204                             Ok(*self.statics.get(&cid).expect("static should have been cached (rvalue)"))
1205                         }
1206                     },
1207                     Promoted { index } => {
1208                         let cid = ConstantId {
1209                             def_id: self.frame().def_id,
1210                             substs: self.substs(),
1211                             kind: ConstantKind::Promoted(index),
1212                         };
1213                         Ok(*self.statics.get(&cid).expect("a promoted constant hasn't been precomputed"))
1214                     },
1215                 }
1216             }
1217         }
1218     }
1219
1220     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1221         use rustc::mir::repr::Lvalue::*;
1222         let ptr = match *lvalue {
1223             ReturnPointer => self.frame().return_ptr
1224                 .expect("ReturnPointer used in a function with no return value"),
1225             Arg(i) => self.frame().locals[i as usize],
1226             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1227             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1228
1229             Static(def_id) => {
1230                 let substs = self.tcx.mk_substs(subst::Substs::empty());
1231                 let cid = ConstantId {
1232                     def_id: def_id,
1233                     substs: substs,
1234                     kind: ConstantKind::Static,
1235                 };
1236                 *self.gecx.statics.get(&cid).expect("static should have been cached (lvalue)")
1237             },
1238
1239             Projection(ref proj) => {
1240                 let base = self.eval_lvalue(&proj.base)?;
1241                 let base_ty = self.lvalue_ty(&proj.base);
1242                 let base_layout = self.type_layout(base_ty);
1243
1244                 use rustc::mir::repr::ProjectionElem::*;
1245                 match proj.elem {
1246                     Field(field, _) => {
1247                         use rustc::ty::layout::Layout::*;
1248                         let variant = match *base_layout {
1249                             Univariant { ref variant, .. } => variant,
1250                             General { ref variants, .. } => {
1251                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1252                                     &variants[variant_idx]
1253                                 } else {
1254                                     panic!("field access on enum had no variant index");
1255                                 }
1256                             }
1257                             RawNullablePointer { .. } => {
1258                                 assert_eq!(field.index(), 0);
1259                                 return Ok(base);
1260                             }
1261                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1262                             _ => panic!("field access on non-product type: {:?}", base_layout),
1263                         };
1264
1265                         let offset = variant.field_offset(field.index()).bytes();
1266                         base.ptr.offset(offset as isize)
1267                     },
1268
1269                     Downcast(_, variant) => {
1270                         use rustc::ty::layout::Layout::*;
1271                         match *base_layout {
1272                             General { discr, .. } => {
1273                                 return Ok(Lvalue {
1274                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1275                                     extra: LvalueExtra::DowncastVariant(variant),
1276                                 });
1277                             }
1278                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1279                                 return Ok(base);
1280                             }
1281                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1282                         }
1283                     },
1284
1285                     Deref => {
1286                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1287                         let ptr = self.memory.read_ptr(base.ptr)?;
1288                         let extra = match pointee_ty.sty {
1289                             ty::TySlice(_) | ty::TyStr => {
1290                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1291                                 let len = self.memory.read_usize(len_ptr)?;
1292                                 LvalueExtra::Length(len)
1293                             }
1294                             ty::TyTrait(_) => unimplemented!(),
1295                             _ => LvalueExtra::None,
1296                         };
1297                         return Ok(Lvalue { ptr: ptr, extra: extra });
1298                     }
1299
1300                     Index(ref operand) => {
1301                         let elem_size = match base_ty.sty {
1302                             ty::TyArray(elem_ty, _) |
1303                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
1304                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1305                         };
1306                         let n_ptr = self.eval_operand(operand)?;
1307                         let n = self.memory.read_usize(n_ptr)?;
1308                         base.ptr.offset(n as isize * elem_size as isize)
1309                     }
1310
1311                     ConstantIndex { .. } => unimplemented!(),
1312                 }
1313             }
1314         };
1315
1316         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1317     }
1318
1319     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1320         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
1321     }
1322
1323     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1324         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
1325     }
1326
1327     fn monomorphize(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1328         self.gecx.monomorphize(ty, self.substs())
1329     }
1330
1331     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1332         let size = self.type_size(ty);
1333         self.memory.copy(src, dest, size)?;
1334         if self.type_needs_drop(ty) {
1335             self.memory.drop_fill(src, size)?;
1336         }
1337         Ok(())
1338     }
1339
1340     fn type_size(&self, ty: Ty<'tcx>) -> usize {
1341         self.gecx.type_size(ty, self.substs())
1342     }
1343
1344     fn type_layout(&self, ty: Ty<'tcx>) -> &'tcx Layout {
1345         self.gecx.type_layout(ty, self.substs())
1346     }
1347
1348     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1349         use syntax::ast::{IntTy, UintTy};
1350         let val = match (self.memory.pointer_size, &ty.sty) {
1351             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1352             (_, &ty::TyInt(IntTy::I8))    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1353             (2, &ty::TyInt(IntTy::Is)) |
1354             (_, &ty::TyInt(IntTy::I16))   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1355             (4, &ty::TyInt(IntTy::Is)) |
1356             (_, &ty::TyInt(IntTy::I32))   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1357             (8, &ty::TyInt(IntTy::Is)) |
1358             (_, &ty::TyInt(IntTy::I64))   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1359             (_, &ty::TyUint(UintTy::U8))  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1360             (2, &ty::TyUint(UintTy::Us)) |
1361             (_, &ty::TyUint(UintTy::U16)) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1362             (4, &ty::TyUint(UintTy::Us)) |
1363             (_, &ty::TyUint(UintTy::U32)) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1364             (8, &ty::TyUint(UintTy::Us)) |
1365             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1366
1367             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
1368             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
1369                 if self.type_is_sized(ty) {
1370                     match self.memory.read_ptr(ptr) {
1371                         Ok(p) => PrimVal::AbstractPtr(p),
1372                         Err(EvalError::ReadBytesAsPointer) => {
1373                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1374                         }
1375                         Err(e) => return Err(e),
1376                     }
1377                 } else {
1378                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1379                 }
1380             }
1381
1382             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1383         };
1384         Ok(val)
1385     }
1386
1387     fn frame(&self) -> &Frame<'mir, 'tcx> {
1388         self.stack.last().expect("no call frames exist")
1389     }
1390
1391     fn basic_block(&self) -> &mir::BasicBlockData<'tcx> {
1392         let frame = self.frame();
1393         frame.mir.basic_block_data(frame.next_block)
1394     }
1395
1396     fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1397         self.stack.last_mut().expect("no call frames exist")
1398     }
1399
1400     fn mir(&self) -> CachedMir<'mir, 'tcx> {
1401         self.frame().mir.clone()
1402     }
1403
1404     fn substs(&self) -> &'tcx Substs<'tcx> {
1405         self.frame().substs
1406     }
1407 }
1408
1409 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1410     match ptr_ty.sty {
1411         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1412         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1413         ty::TyBox(ty) => {
1414             Some(ty)
1415         }
1416         _ => None,
1417     }
1418 }
1419
1420 impl Lvalue {
1421     fn to_ptr(self) -> Pointer {
1422         assert_eq!(self.extra, LvalueExtra::None);
1423         self.ptr
1424     }
1425 }
1426
1427 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1428     type Target = mir::Mir<'tcx>;
1429     fn deref(&self) -> &mir::Mir<'tcx> {
1430         match *self {
1431             CachedMir::Ref(r) => r,
1432             CachedMir::Owned(ref rc) => rc,
1433         }
1434     }
1435 }
1436
1437 #[derive(Debug)]
1438 pub struct ImplMethod<'tcx> {
1439     pub method: Rc<ty::Method<'tcx>>,
1440     pub substs: &'tcx Substs<'tcx>,
1441     pub is_provided: bool,
1442 }
1443
1444 /// Locates the applicable definition of a method, given its name.
1445 pub fn get_impl_method<'a, 'tcx>(
1446     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1447     impl_def_id: DefId,
1448     substs: &'tcx Substs<'tcx>,
1449     name: ast::Name,
1450 ) -> ImplMethod<'tcx> {
1451     assert!(!substs.types.needs_infer());
1452
1453     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1454     let trait_def = tcx.lookup_trait_def(trait_def_id);
1455
1456     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1457         Some(node_item) => {
1458             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1459                 let substs = traits::translate_substs(&infcx, impl_def_id,
1460                                                       substs, node_item.node);
1461                 tcx.lift(&substs).unwrap_or_else(|| {
1462                     bug!("trans::meth::get_impl_method: translate_substs \
1463                           returned {:?} which contains inference types/regions",
1464                          substs);
1465                 })
1466             });
1467             ImplMethod {
1468                 method: node_item.item,
1469                 substs: substs,
1470                 is_provided: node_item.node.is_from_trait(),
1471             }
1472         }
1473         None => {
1474             bug!("method {:?} not found in {:?}", name, impl_def_id)
1475         }
1476     }
1477 }
1478
1479 pub fn interpret_start_points<'a, 'tcx>(
1480     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1481     mir_map: &MirMap<'tcx>,
1482 ) {
1483     let initial_indentation = ::log_settings::settings().indentation;
1484     for (&id, mir) in &mir_map.map {
1485         for attr in tcx.map.attrs(id) {
1486             use syntax::attr::AttrMetaMethods;
1487             if attr.check_name("miri_run") {
1488                 let item = tcx.map.expect_item(id);
1489
1490                 ::log_settings::settings().indentation = initial_indentation;
1491
1492                 debug!("Interpreting: {}", item.name);
1493
1494                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1495                 match gecx.call(mir, tcx.map.local_def_id(id)) {
1496                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
1497                         gecx.memory.dump(return_ptr.alloc_id);
1498                     },
1499                     Ok(None) => warn!("diverging function returned"),
1500                     Err(_e) => {
1501                         // TODO(solson): Detect whether the error was already reported or not.
1502                         // tcx.sess.err(&e.to_string());
1503                     }
1504                 }
1505             }
1506         }
1507     }
1508 }
1509
1510 // TODO(solson): Upstream these methods into rustc::ty::layout.
1511
1512 trait IntegerExt {
1513     fn size(self) -> Size;
1514 }
1515
1516 impl IntegerExt for layout::Integer {
1517     fn size(self) -> Size {
1518         use rustc::ty::layout::Integer::*;
1519         match self {
1520             I1 | I8 => Size::from_bits(8),
1521             I16 => Size::from_bits(16),
1522             I32 => Size::from_bits(32),
1523             I64 => Size::from_bits(64),
1524         }
1525     }
1526 }
1527
1528 trait StructExt {
1529     fn field_offset(&self, index: usize) -> Size;
1530 }
1531
1532 impl StructExt for layout::Struct {
1533     fn field_offset(&self, index: usize) -> Size {
1534         if index == 0 {
1535             Size::from_bytes(0)
1536         } else {
1537             self.offset_after_field[index - 1]
1538         }
1539     }
1540 }