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, Span};
  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     // Constants that need to be evaluated before the next statement can be evaluated
  99     constants: Vec<(ConstantId<'tcx>, Span, Pointer, CachedMir<'a, 'tcx>)>,
 100 }
 101
 102 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 103 struct Lvalue {
 104     ptr: Pointer,
 105     extra: LvalueExtra,
 106 }
 107
 108 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 109 enum LvalueExtra {
 110     None,
 111     Length(u64),
 112     // TODO(solson): Vtable(memory::AllocId),
 113     DowncastVariant(usize),
 114 }
 115
 116 #[derive(Clone)]
 117 enum CachedMir<'mir, 'tcx: 'mir> {
 118     Ref(&'mir mir::Mir<'tcx>),
 119     Owned(Rc<mir::Mir<'tcx>>)
 120 }
 121
 122 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 123 enum TerminatorTarget {
 124     /// Make a local jump to the next block
 125     Block,
 126
 127     /// Start executing from the new current frame. (For function calls.)
 128     Call,
 129
 130     /// Stop executing the current frame and resume the previous frame.
 131     Return,
 132 }
 133
 134 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 135 enum ConstantId<'tcx> {
 136     Promoted { def_id: DefId, substs: &'tcx Substs<'tcx>, index: usize },
 137     Static { def_id: DefId, substs: &'tcx Substs<'tcx> },
 138 }
 139
 140 impl<'tcx> ConstantId<'tcx> {
 141     fn substs(&self) -> &'tcx Substs<'tcx> {
 142         use self::ConstantId::*;
 143         match *self {
 144             Promoted { substs, .. } |
 145             Static { substs, .. } => substs
 146         }
 147     }
 148
 149     fn def_id(&self) -> DefId {
 150         use self::ConstantId::*;
 151         match *self {
 152             Promoted { def_id, .. } |
 153             Static { def_id, .. } => def_id,
 154         }
 155     }
 156 }
 157
 158
 159 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 160     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 161         GlobalEvalContext {
 162             tcx: tcx,
 163             mir_map: mir_map,
 164             mir_cache: RefCell::new(DefIdMap()),
 165             memory: Memory::new(tcx.sess
 166                                    .target
 167                                    .uint_type
 168                                    .bit_width()
 169                                    .expect("Session::target::uint_type was usize")/8),
 170             statics: HashMap::new(),
 171         }
 172     }
 173
 174     fn call(&mut self, mir: &mir::Mir<'tcx>, def_id: DefId) -> EvalResult<Option<Pointer>> {
 175         let substs = self.tcx.mk_substs(subst::Substs::empty());
 176         let return_ptr = self.alloc_ret_ptr(mir.return_ty, substs);
 177
 178         let mut nested_fecx = FnEvalContext::new(self);
 179
 180         nested_fecx.push_stack_frame(def_id, mir.span, CachedMir::Ref(mir), substs, None);
 181
 182         nested_fecx.frame_mut().return_ptr = return_ptr;
 183
 184         nested_fecx.run()?;
 185         Ok(return_ptr)
 186     }
 187
 188     fn alloc_ret_ptr(&mut self, ty: ty::FnOutput<'tcx>, substs: &'tcx Substs<'tcx>) -> Option<Pointer> {
 189         match ty {
 190             ty::FnConverging(ty) => {
 191                 let size = self.type_size(ty, substs);
 192                 Some(self.memory.allocate(size))
 193             }
 194             ty::FnDiverging => None,
 195         }
 196     }
 197
 198     // TODO(solson): Try making const_to_primval instead.
 199     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
 200         use rustc::middle::const_val::ConstVal::*;
 201         match *const_val {
 202             Float(_f) => unimplemented!(),
 203             Integral(int) => {
 204                 // TODO(solson): Check int constant type.
 205                 let ptr = self.memory.allocate(8);
 206                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
 207                 Ok(ptr)
 208             }
 209             Str(ref s) => {
 210                 let psize = self.memory.pointer_size;
 211                 let static_ptr = self.memory.allocate(s.len());
 212                 let ptr = self.memory.allocate(psize * 2);
 213                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
 214                 self.memory.write_ptr(ptr, static_ptr)?;
 215                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
 216                 Ok(ptr)
 217             }
 218             ByteStr(ref bs) => {
 219                 let psize = self.memory.pointer_size;
 220                 let static_ptr = self.memory.allocate(bs.len());
 221                 let ptr = self.memory.allocate(psize);
 222                 self.memory.write_bytes(static_ptr, bs)?;
 223                 self.memory.write_ptr(ptr, static_ptr)?;
 224                 Ok(ptr)
 225             }
 226             Bool(b) => {
 227                 let ptr = self.memory.allocate(1);
 228                 self.memory.write_bool(ptr, b)?;
 229                 Ok(ptr)
 230             }
 231             Char(_c)          => unimplemented!(),
 232             Struct(_node_id)  => unimplemented!(),
 233             Tuple(_node_id)   => unimplemented!(),
 234             Function(_def_id) => unimplemented!(),
 235             Array(_, _)       => unimplemented!(),
 236             Repeat(_, _)      => unimplemented!(),
 237             Dummy             => unimplemented!(),
 238         }
 239     }
 240
 241     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
 242         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
 243     }
 244
 245     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
 246         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
 247     }
 248
 249     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
 250         // Do the initial selection for the obligation. This yields the shallow result we are
 251         // looking for -- that is, what specific impl.
 252         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 253             let mut selcx = traits::SelectionContext::new(&infcx);
 254
 255             let obligation = traits::Obligation::new(
 256                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
 257                 trait_ref.to_poly_trait_predicate(),
 258             );
 259             let selection = selcx.select(&obligation).unwrap().unwrap();
 260
 261             // Currently, we use a fulfillment context to completely resolve all nested obligations.
 262             // This is because they can inform the inference of the impl's type parameters.
 263             let mut fulfill_cx = traits::FulfillmentContext::new();
 264             let vtable = selection.map(|predicate| {
 265                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
 266             });
 267             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
 268         })
 269     }
 270
 271     /// Trait method, which has to be resolved to an impl method.
 272     pub fn trait_method(
 273         &self,
 274         def_id: DefId,
 275         substs: &'tcx Substs<'tcx>
 276     ) -> (DefId, &'tcx Substs<'tcx>) {
 277         let method_item = self.tcx.impl_or_trait_item(def_id);
 278         let trait_id = method_item.container().id();
 279         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
 280         match self.fulfill_obligation(trait_ref) {
 281             traits::VtableImpl(vtable_impl) => {
 282                 let impl_did = vtable_impl.impl_def_id;
 283                 let mname = self.tcx.item_name(def_id);
 284                 // Create a concatenated set of substitutions which includes those from the impl
 285                 // and those from the method:
 286                 let impl_substs = vtable_impl.substs.with_method_from(substs);
 287                 let substs = self.tcx.mk_substs(impl_substs);
 288                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
 289
 290                 (mth.method.def_id, mth.substs)
 291             }
 292
 293             traits::VtableClosure(vtable_closure) =>
 294                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
 295
 296             traits::VtableFnPointer(_fn_ty) => {
 297                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
 298                 unimplemented!()
 299                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
 300
 301                 // let method_ty = def_ty(tcx, def_id, substs);
 302                 // let fn_ptr_ty = match method_ty.sty {
 303                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
 304                 //     _ => unreachable!("expected fn item type, found {}",
 305                 //                       method_ty)
 306                 // };
 307                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
 308             }
 309
 310             traits::VtableObject(ref _data) => {
 311                 unimplemented!()
 312                 // Callee {
 313                 //     data: Virtual(traits::get_vtable_index_of_object_method(
 314                 //                   tcx, data, def_id)),
 315                 //                   ty: def_ty(tcx, def_id, substs)
 316                 // }
 317             }
 318             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
 319         }
 320     }
 321
 322     fn load_mir(&self, def_id: DefId) -> CachedMir<'a, 'tcx> {
 323         match self.tcx.map.as_local_node_id(def_id) {
 324             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
 325             None => {
 326                 let mut mir_cache = self.mir_cache.borrow_mut();
 327                 if let Some(mir) = mir_cache.get(&def_id) {
 328                     return CachedMir::Owned(mir.clone());
 329                 }
 330
 331                 let cs = &self.tcx.sess.cstore;
 332                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
 333                     panic!("no mir for {:?}", def_id);
 334                 });
 335                 let cached = Rc::new(mir);
 336                 mir_cache.insert(def_id, cached.clone());
 337                 CachedMir::Owned(cached)
 338             }
 339         }
 340     }
 341
 342     fn monomorphize(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> Ty<'tcx> {
 343         let substituted = ty.subst(self.tcx, substs);
 344         self.tcx.normalize_associated_type(&substituted)
 345     }
 346
 347     fn type_size(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> usize {
 348         self.type_layout(ty, substs).size(&self.tcx.data_layout).bytes() as usize
 349     }
 350
 351     fn type_layout(&self, ty: Ty<'tcx>, substs: &'tcx Substs<'tcx>) -> &'tcx Layout {
 352         // TODO(solson): Is this inefficient? Needs investigation.
 353         let ty = self.monomorphize(ty, substs);
 354
 355         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
 356             // TODO(solson): Report this error properly.
 357             ty.layout(&infcx).unwrap()
 358         })
 359     }
 360 }
 361
 362 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 363     fn new(gecx: &'a mut GlobalEvalContext<'b, 'tcx>) -> Self {
 364         FnEvalContext {
 365             gecx: gecx,
 366             stack: Vec::new(),
 367         }
 368     }
 369
 370     #[inline(never)]
 371     #[cold]
 372     fn report(&self, e: &EvalError) {
 373         let stmt = self.frame().stmt;
 374         let block = self.basic_block();
 375         let span = if stmt < block.statements.len() {
 376             block.statements[stmt].span
 377         } else {
 378             block.terminator().span
 379         };
 380         let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 381         for &Frame{ def_id, substs, span, .. } in self.stack.iter().rev() {
 382             // FIXME(solson): Find a way to do this without this Display impl hack.
 383             use rustc::util::ppaux;
 384             use std::fmt;
 385             struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 386             impl<'tcx> fmt::Display for Instance<'tcx> {
 387                 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 388                     ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 389                         |tcx| tcx.lookup_item_type(self.0).generics)
 390                 }
 391             }
 392             err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 393         }
 394         err.emit();
 395     }
 396
 397     fn maybe_report<T>(&self, r: EvalResult<T>) -> EvalResult<T> {
 398         if let Err(ref e) = r {
 399             self.report(e);
 400         }
 401         r
 402     }
 403
 404     fn run(&mut self) -> EvalResult<()> {
 405         let mut stepper = stepper::Stepper::new(self);
 406         'outer: loop {
 407             use self::stepper::Event::*;
 408             trace!("// {:?}", stepper.block());
 409
 410             loop {
 411                 match stepper.step()? {
 412                     Constant => trace!("next statement requires the computation of a constant"),
 413                     Assignment => trace!("{:?}", stepper.stmt()),
 414                     Terminator => {
 415                         trace!("{:?}", stepper.term().kind);
 416                         continue 'outer;
 417                     },
 418                     Done => return Ok(()),
 419                 }
 420             }
 421         }
 422     }
 423
 424     fn push_stack_frame(&mut self, def_id: DefId, span: codemap::Span, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
 425         return_ptr: Option<Pointer>)
 426     {
 427         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 428         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 429         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 430
 431         let num_args = mir.arg_decls.len();
 432         let num_vars = mir.var_decls.len();
 433
 434         ::log_settings::settings().indentation += 1;
 435
 436         self.stack.push(Frame {
 437             mir: mir.clone(),
 438             next_block: mir::START_BLOCK,
 439             return_ptr: return_ptr,
 440             locals: Vec::new(),
 441             var_offset: num_args,
 442             temp_offset: num_args + num_vars,
 443             span: span,
 444             def_id: def_id,
 445             substs: substs,
 446             stmt: 0,
 447             constants: Vec::new(),
 448         });
 449
 450         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 451             let size = self.type_size(ty);
 452             self.memory.allocate(size)
 453         }).collect();
 454
 455         self.frame_mut().locals = locals;
 456     }
 457
 458     fn pop_stack_frame(&mut self) {
 459         ::log_settings::settings().indentation -= 1;
 460         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 461         // TODO(solson): Deallocate local variables.
 462     }
 463
 464     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 465             -> EvalResult<TerminatorTarget> {
 466         use rustc::mir::repr::TerminatorKind::*;
 467         let target = match terminator.kind {
 468             Return => TerminatorTarget::Return,
 469
 470             Goto { target } => {
 471                 self.frame_mut().next_block = target;
 472                 TerminatorTarget::Block
 473             },
 474
 475             If { ref cond, targets: (then_target, else_target) } => {
 476                 let cond_ptr = self.eval_operand(cond)?;
 477                 let cond_val = self.memory.read_bool(cond_ptr)?;
 478                 self.frame_mut().next_block = if cond_val { then_target } else { else_target };
 479                 TerminatorTarget::Block
 480             }
 481
 482             SwitchInt { ref discr, ref values, ref targets, .. } => {
 483                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 484                 let discr_size = self
 485                     .type_layout(self.lvalue_ty(discr))
 486                     .size(&self.tcx.data_layout)
 487                     .bytes() as usize;
 488                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 489
 490                 // Branch to the `otherwise` case by default, if no match is found.
 491                 let mut target_block = targets[targets.len() - 1];
 492
 493                 for (index, val_const) in values.iter().enumerate() {
 494                     let ptr = self.const_to_ptr(val_const)?;
 495                     let val = self.memory.read_uint(ptr, discr_size)?;
 496                     if discr_val == val {
 497                         target_block = targets[index];
 498                         break;
 499                     }
 500                 }
 501
 502                 self.frame_mut().next_block = target_block;
 503                 TerminatorTarget::Block
 504             }
 505
 506             Switch { ref discr, ref targets, adt_def } => {
 507                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 508                 let adt_ty = self.lvalue_ty(discr);
 509                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 510                 let matching = adt_def.variants.iter()
 511                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 512
 513                 match matching {
 514                     Some(i) => {
 515                         self.frame_mut().next_block = targets[i];
 516                         TerminatorTarget::Block
 517                     },
 518                     None => return Err(EvalError::InvalidDiscriminant),
 519                 }
 520             }
 521
 522             Call { ref func, ref args, ref destination, .. } => {
 523                 let mut return_ptr = None;
 524                 if let Some((ref lv, target)) = *destination {
 525                     self.frame_mut().next_block = target;
 526                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 527                 }
 528
 529                 let func_ty = self.operand_ty(func);
 530                 match func_ty.sty {
 531                     ty::TyFnDef(def_id, substs, fn_ty) => {
 532                         use syntax::abi::Abi;
 533                         match fn_ty.abi {
 534                             Abi::RustIntrinsic => {
 535                                 let name = self.tcx.item_name(def_id).as_str();
 536                                 match fn_ty.sig.0.output {
 537                                     ty::FnConverging(ty) => {
 538                                         let size = self.type_size(ty);
 539                                         let ret = return_ptr.unwrap();
 540                                         self.call_intrinsic(&name, substs, args, ret, size)?
 541                                     }
 542                                     ty::FnDiverging => unimplemented!(),
 543                                 }
 544                             }
 545
 546                             Abi::C => {
 547                                 match fn_ty.sig.0.output {
 548                                     ty::FnConverging(ty) => {
 549                                         let size = self.type_size(ty);
 550                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 551                                     }
 552                                     ty::FnDiverging => unimplemented!(),
 553                                 }
 554                             }
 555
 556                             Abi::Rust | Abi::RustCall => {
 557                                 // TODO(solson): Adjust the first argument when calling a Fn or
 558                                 // FnMut closure via FnOnce::call_once.
 559
 560                                 // Only trait methods can have a Self parameter.
 561                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 562                                     self.trait_method(def_id, substs)
 563                                 } else {
 564                                     (def_id, substs)
 565                                 };
 566
 567                                 let mut arg_srcs = Vec::new();
 568                                 for arg in args {
 569                                     let src = self.eval_operand(arg)?;
 570                                     let src_ty = self.operand_ty(arg);
 571                                     arg_srcs.push((src, src_ty));
 572                                 }
 573
 574                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 575                                     arg_srcs.pop();
 576                                     let last_arg = args.last().unwrap();
 577                                     let last = self.eval_operand(last_arg)?;
 578                                     let last_ty = self.operand_ty(last_arg);
 579                                     let last_layout = self.type_layout(last_ty);
 580                                     match (&last_ty.sty, last_layout) {
 581                                         (&ty::TyTuple(fields),
 582                                          &Layout::Univariant { ref variant, .. }) => {
 583                                             let offsets = iter::once(0)
 584                                                 .chain(variant.offset_after_field.iter()
 585                                                     .map(|s| s.bytes()));
 586                                             for (offset, ty) in offsets.zip(fields) {
 587                                                 let src = last.offset(offset as isize);
 588                                                 arg_srcs.push((src, ty));
 589                                             }
 590                                         }
 591                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 592                                     }
 593                                 }
 594
 595                                 let mir = self.load_mir(resolved_def_id);
 596                                 self.push_stack_frame(def_id, terminator.span, mir, resolved_substs, return_ptr);
 597
 598                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 599                                     let dest = self.frame().locals[i];
 600                                     self.move_(src, dest, src_ty)?;
 601                                 }
 602
 603                                 TerminatorTarget::Call
 604                             }
 605
 606                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 607                         }
 608                     }
 609
 610                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 611                 }
 612             }
 613
 614             Drop { ref value, target, .. } => {
 615                 let ptr = self.eval_lvalue(value)?.to_ptr();
 616                 let ty = self.lvalue_ty(value);
 617                 self.drop(ptr, ty)?;
 618                 self.frame_mut().next_block = target;
 619                 TerminatorTarget::Block
 620             }
 621
 622             Resume => unimplemented!(),
 623         };
 624
 625         Ok(target)
 626     }
 627
 628     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 629         if !self.type_needs_drop(ty) {
 630             debug!("no need to drop {:?}", ty);
 631             return Ok(());
 632         }
 633         trace!("-need to drop {:?}", ty);
 634
 635         // TODO(solson): Call user-defined Drop::drop impls.
 636
 637         match ty.sty {
 638             ty::TyBox(contents_ty) => {
 639                 match self.memory.read_ptr(ptr) {
 640                     Ok(contents_ptr) => {
 641                         self.drop(contents_ptr, contents_ty)?;
 642                         trace!("-deallocating box");
 643                         self.memory.deallocate(contents_ptr)?;
 644                     }
 645                     Err(EvalError::ReadBytesAsPointer) => {
 646                         let size = self.memory.pointer_size;
 647                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 648                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 649                             return Ok(());
 650                         } else {
 651                             return Err(EvalError::ReadBytesAsPointer);
 652                         }
 653                     }
 654                     Err(e) => return Err(e),
 655                 }
 656             }
 657
 658             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 659             _ => {}
 660         }
 661
 662         // Filling drop.
 663         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 664         let size = self.type_size(ty);
 665         self.memory.drop_fill(ptr, size)?;
 666
 667         Ok(())
 668     }
 669
 670     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 671         use rustc::ty::layout::Layout::*;
 672         let adt_layout = self.type_layout(adt_ty);
 673
 674         let discr_val = match *adt_layout {
 675             General { discr, .. } | CEnum { discr, .. } => {
 676                 let discr_size = discr.size().bytes();
 677                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 678             }
 679
 680             RawNullablePointer { nndiscr, .. } => {
 681                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 682             }
 683
 684             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 685                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 686                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 687                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 688             }
 689
 690             // The discriminant_value intrinsic returns 0 for non-sum types.
 691             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 692             Vector { .. } => 0,
 693         };
 694
 695         Ok(discr_val)
 696     }
 697
 698     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 699         let not_null = match self.memory.read_usize(ptr) {
 700             Ok(0) => false,
 701             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 702             Err(e) => return Err(e),
 703         };
 704         assert!(nndiscr == 0 || nndiscr == 1);
 705         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 706     }
 707
 708     fn call_intrinsic(
 709         &mut self,
 710         name: &str,
 711         substs: &'tcx Substs<'tcx>,
 712         args: &[mir::Operand<'tcx>],
 713         dest: Pointer,
 714         dest_size: usize
 715     ) -> EvalResult<TerminatorTarget> {
 716         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 717             .map(|arg| self.eval_operand(arg))
 718             .collect();
 719         let args = args_res?;
 720
 721         match name {
 722             // FIXME(solson): Handle different integer types correctly.
 723             "add_with_overflow" => {
 724                 let ty = *substs.types.get(subst::FnSpace, 0);
 725                 let size = self.type_size(ty);
 726                 let left = self.memory.read_int(args[0], size)?;
 727                 let right = self.memory.read_int(args[1], size)?;
 728                 let (n, overflowed) = unsafe {
 729                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 730                 };
 731                 self.memory.write_int(dest, n, size)?;
 732                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 733             }
 734
 735             "assume" => {}
 736
 737             "copy_nonoverlapping" => {
 738                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 739                 let elem_size = self.type_size(elem_ty);
 740                 let src = self.memory.read_ptr(args[0])?;
 741                 let dest = self.memory.read_ptr(args[1])?;
 742                 let count = self.memory.read_isize(args[2])?;
 743                 self.memory.copy(src, dest, count as usize * elem_size)?;
 744             }
 745
 746             "discriminant_value" => {
 747                 let ty = *substs.types.get(subst::FnSpace, 0);
 748                 let adt_ptr = self.memory.read_ptr(args[0])?;
 749                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 750                 self.memory.write_uint(dest, discr_val, dest_size)?;
 751             }
 752
 753             "forget" => {
 754                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 755                 let arg_size = self.type_size(arg_ty);
 756                 self.memory.drop_fill(args[0], arg_size)?;
 757             }
 758
 759             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 760
 761             "min_align_of" => {
 762                 self.memory.write_int(dest, 1, dest_size)?;
 763             }
 764
 765             "move_val_init" => {
 766                 let ty = *substs.types.get(subst::FnSpace, 0);
 767                 let ptr = self.memory.read_ptr(args[0])?;
 768                 self.move_(args[1], ptr, ty)?;
 769             }
 770
 771             // FIXME(solson): Handle different integer types correctly.
 772             "mul_with_overflow" => {
 773                 let ty = *substs.types.get(subst::FnSpace, 0);
 774                 let size = self.type_size(ty);
 775                 let left = self.memory.read_int(args[0], size)?;
 776                 let right = self.memory.read_int(args[1], size)?;
 777                 let (n, overflowed) = unsafe {
 778                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 779                 };
 780                 self.memory.write_int(dest, n, size)?;
 781                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 782             }
 783
 784             "offset" => {
 785                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 786                 let pointee_size = self.type_size(pointee_ty) as isize;
 787                 let ptr_arg = args[0];
 788                 let offset = self.memory.read_isize(args[1])?;
 789
 790                 match self.memory.read_ptr(ptr_arg) {
 791                     Ok(ptr) => {
 792                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 793                         self.memory.write_ptr(dest, result_ptr)?;
 794                     }
 795                     Err(EvalError::ReadBytesAsPointer) => {
 796                         let addr = self.memory.read_isize(ptr_arg)?;
 797                         let result_addr = addr + offset * pointee_size as i64;
 798                         self.memory.write_isize(dest, result_addr)?;
 799                     }
 800                     Err(e) => return Err(e),
 801                 }
 802             }
 803
 804             // FIXME(solson): Handle different integer types correctly. Use primvals?
 805             "overflowing_sub" => {
 806                 let ty = *substs.types.get(subst::FnSpace, 0);
 807                 let size = self.type_size(ty);
 808                 let left = self.memory.read_int(args[0], size)?;
 809                 let right = self.memory.read_int(args[1], size)?;
 810                 let n = left.wrapping_sub(right);
 811                 self.memory.write_int(dest, n, size)?;
 812             }
 813
 814             "size_of" => {
 815                 let ty = *substs.types.get(subst::FnSpace, 0);
 816                 let size = self.type_size(ty) as u64;
 817                 self.memory.write_uint(dest, size, dest_size)?;
 818             }
 819
 820             "size_of_val" => {
 821                 let ty = *substs.types.get(subst::FnSpace, 0);
 822                 if self.type_is_sized(ty) {
 823                     let size = self.type_size(ty) as u64;
 824                     self.memory.write_uint(dest, size, dest_size)?;
 825                 } else {
 826                     match ty.sty {
 827                         ty::TySlice(_) | ty::TyStr => {
 828                             let elem_ty = ty.sequence_element_type(self.tcx);
 829                             let elem_size = self.type_size(elem_ty) as u64;
 830                             let ptr_size = self.memory.pointer_size as isize;
 831                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 832                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 833                         }
 834
 835                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 836                     }
 837                 }
 838             }
 839
 840             "transmute" => {
 841                 let ty = *substs.types.get(subst::FnSpace, 0);
 842                 self.move_(args[0], dest, ty)?;
 843             }
 844             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 845
 846             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 847         }
 848
 849         // Since we pushed no stack frame, the main loop will act
 850         // as if the call just completed and it's returning to the
 851         // current frame.
 852         Ok(TerminatorTarget::Call)
 853     }
 854
 855     fn call_c_abi(
 856         &mut self,
 857         def_id: DefId,
 858         args: &[mir::Operand<'tcx>],
 859         dest: Pointer,
 860         dest_size: usize,
 861     ) -> EvalResult<TerminatorTarget> {
 862         let name = self.tcx.item_name(def_id);
 863         let attrs = self.tcx.get_attrs(def_id);
 864         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 865             Some(ln) => ln.clone(),
 866             None => name.as_str(),
 867         };
 868
 869         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 870             .map(|arg| self.eval_operand(arg))
 871             .collect();
 872         let args = args_res?;
 873
 874         match &link_name[..] {
 875             "__rust_allocate" => {
 876                 let size = self.memory.read_usize(args[0])?;
 877                 let ptr = self.memory.allocate(size as usize);
 878                 self.memory.write_ptr(dest, ptr)?;
 879             }
 880
 881             "__rust_reallocate" => {
 882                 let ptr = self.memory.read_ptr(args[0])?;
 883                 let size = self.memory.read_usize(args[2])?;
 884                 self.memory.reallocate(ptr, size as usize)?;
 885                 self.memory.write_ptr(dest, ptr)?;
 886             }
 887
 888             "memcmp" => {
 889                 let left = self.memory.read_ptr(args[0])?;
 890                 let right = self.memory.read_ptr(args[1])?;
 891                 let n = self.memory.read_usize(args[2])? as usize;
 892
 893                 let result = {
 894                     let left_bytes = self.memory.read_bytes(left, n)?;
 895                     let right_bytes = self.memory.read_bytes(right, n)?;
 896
 897                     use std::cmp::Ordering::*;
 898                     match left_bytes.cmp(right_bytes) {
 899                         Less => -1,
 900                         Equal => 0,
 901                         Greater => 1,
 902                     }
 903                 };
 904
 905                 self.memory.write_int(dest, result, dest_size)?;
 906             }
 907
 908             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 909         }
 910
 911         // Since we pushed no stack frame, the main loop will act
 912         // as if the call just completed and it's returning to the
 913         // current frame.
 914         Ok(TerminatorTarget::Call)
 915     }
 916
 917     fn assign_fields<I: IntoIterator<Item = u64>>(
 918         &mut self,
 919         dest: Pointer,
 920         offsets: I,
 921         operands: &[mir::Operand<'tcx>],
 922     ) -> EvalResult<()> {
 923         for (offset, operand) in offsets.into_iter().zip(operands) {
 924             let src = self.eval_operand(operand)?;
 925             let src_ty = self.operand_ty(operand);
 926             let field_dest = dest.offset(offset as isize);
 927             self.move_(src, field_dest, src_ty)?;
 928         }
 929         Ok(())
 930     }
 931
 932     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 933         -> EvalResult<()>
 934     {
 935         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 936         let dest_ty = self.lvalue_ty(lvalue);
 937         let dest_layout = self.type_layout(dest_ty);
 938
 939         use rustc::mir::repr::Rvalue::*;
 940         match *rvalue {
 941             Use(ref operand) => {
 942                 let src = self.eval_operand(operand)?;
 943                 self.move_(src, dest, dest_ty)?;
 944             }
 945
 946             BinaryOp(bin_op, ref left, ref right) => {
 947                 let left_ptr = self.eval_operand(left)?;
 948                 let left_ty = self.operand_ty(left);
 949                 let left_val = self.read_primval(left_ptr, left_ty)?;
 950
 951                 let right_ptr = self.eval_operand(right)?;
 952                 let right_ty = self.operand_ty(right);
 953                 let right_val = self.read_primval(right_ptr, right_ty)?;
 954
 955                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 956                 self.memory.write_primval(dest, val)?;
 957             }
 958
 959             UnaryOp(un_op, ref operand) => {
 960                 let ptr = self.eval_operand(operand)?;
 961                 let ty = self.operand_ty(operand);
 962                 let val = self.read_primval(ptr, ty)?;
 963                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 964             }
 965
 966             Aggregate(ref kind, ref operands) => {
 967                 use rustc::ty::layout::Layout::*;
 968                 match *dest_layout {
 969                     Univariant { ref variant, .. } => {
 970                         let offsets = iter::once(0)
 971                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 972                         self.assign_fields(dest, offsets, operands)?;
 973                     }
 974
 975                     Array { .. } => {
 976                         let elem_size = match dest_ty.sty {
 977                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 978                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 979                                         kind, dest_ty),
 980                         };
 981                         let offsets = (0..).map(|i| i * elem_size);
 982                         self.assign_fields(dest, offsets, operands)?;
 983                     }
 984
 985                     General { discr, ref variants, .. } => {
 986                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 987                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 988                             let discr_size = discr.size().bytes() as usize;
 989                             self.memory.write_uint(dest, discr_val, discr_size)?;
 990
 991                             let offsets = variants[variant].offset_after_field.iter()
 992                                 .map(|s| s.bytes());
 993                             self.assign_fields(dest, offsets, operands)?;
 994                         } else {
 995                             panic!("tried to assign {:?} to Layout::General", kind);
 996                         }
 997                     }
 998
 999                     RawNullablePointer { nndiscr, .. } => {
1000                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
1001                             if nndiscr == variant as u64 {
1002                                 assert_eq!(operands.len(), 1);
1003                                 let operand = &operands[0];
1004                                 let src = self.eval_operand(operand)?;
1005                                 let src_ty = self.operand_ty(operand);
1006                                 self.move_(src, dest, src_ty)?;
1007                             } else {
1008                                 assert_eq!(operands.len(), 0);
1009                                 self.memory.write_isize(dest, 0)?;
1010                             }
1011                         } else {
1012                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
1013                         }
1014                     }
1015
1016                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
1017                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
1018                             if nndiscr == variant as u64 {
1019                                 let offsets = iter::once(0)
1020                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
1021                                 try!(self.assign_fields(dest, offsets, operands));
1022                             } else {
1023                                 assert_eq!(operands.len(), 0);
1024                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
1025                                 let dest = dest.offset(offset.bytes() as isize);
1026                                 try!(self.memory.write_isize(dest, 0));
1027                             }
1028                         } else {
1029                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
1030                         }
1031                     }
1032
1033                     CEnum { discr, signed, .. } => {
1034                         assert_eq!(operands.len(), 0);
1035                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
1036                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
1037                             let size = discr.size().bytes() as usize;
1038
1039                             if signed {
1040                                 self.memory.write_int(dest, val as i64, size)?;
1041                             } else {
1042                                 self.memory.write_uint(dest, val, size)?;
1043                             }
1044                         } else {
1045                             panic!("tried to assign {:?} to Layout::CEnum", kind);
1046                         }
1047                     }
1048
1049                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
1050                 }
1051             }
1052
1053             Repeat(ref operand, _) => {
1054                 let (elem_size, length) = match dest_ty.sty {
1055                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
1056                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
1057                 };
1058
1059                 let src = self.eval_operand(operand)?;
1060                 for i in 0..length {
1061                     let elem_dest = dest.offset((i * elem_size) as isize);
1062                     self.memory.copy(src, elem_dest, elem_size)?;
1063                 }
1064             }
1065
1066             Len(ref lvalue) => {
1067                 let src = self.eval_lvalue(lvalue)?;
1068                 let ty = self.lvalue_ty(lvalue);
1069                 let len = match ty.sty {
1070                     ty::TyArray(_, n) => n as u64,
1071                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
1072                         n
1073                     } else {
1074                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
1075                     },
1076                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
1077                 };
1078                 self.memory.write_usize(dest, len)?;
1079             }
1080
1081             Ref(_, _, ref lvalue) => {
1082                 let lv = self.eval_lvalue(lvalue)?;
1083                 self.memory.write_ptr(dest, lv.ptr)?;
1084                 match lv.extra {
1085                     LvalueExtra::None => {},
1086                     LvalueExtra::Length(len) => {
1087                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
1088                         self.memory.write_usize(len_ptr, len)?;
1089                     }
1090                     LvalueExtra::DowncastVariant(..) =>
1091                         panic!("attempted to take a reference to an enum downcast lvalue"),
1092                 }
1093             }
1094
1095             Box(ty) => {
1096                 let size = self.type_size(ty);
1097                 let ptr = self.memory.allocate(size);
1098                 self.memory.write_ptr(dest, ptr)?;
1099             }
1100
1101             Cast(kind, ref operand, dest_ty) => {
1102                 let src = self.eval_operand(operand)?;
1103                 let src_ty = self.operand_ty(operand);
1104
1105                 use rustc::mir::repr::CastKind::*;
1106                 match kind {
1107                     Unsize => {
1108                         self.move_(src, dest, src_ty)?;
1109                         let src_pointee_ty = pointee_type(src_ty).unwrap();
1110                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
1111
1112                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
1113                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
1114                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
1115                                 self.memory.write_usize(len_ptr, length as u64)?;
1116                             }
1117
1118                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1119                         }
1120                     }
1121
1122                     Misc => {
1123                         // FIXME(solson): Wrong for almost everything.
1124                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
1125                         self.memory.copy(src, dest, size)?;
1126                     }
1127
1128                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
1129                 }
1130             }
1131
1132             Slice { .. } => unimplemented!(),
1133             InlineAsm { .. } => unimplemented!(),
1134         }
1135
1136         Ok(())
1137     }
1138
1139     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
1140         // Skip the constant 0 at the start meant for LLVM GEP.
1141         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
1142
1143         // Handle the field index for the outer non-null variant.
1144         let inner_ty = match ty.sty {
1145             ty::TyEnum(adt_def, substs) => {
1146                 let variant = &adt_def.variants[nndiscr as usize];
1147                 let index = path.next().unwrap();
1148                 let field = &variant.fields[index];
1149                 field.ty(self.tcx, substs)
1150             }
1151             _ => panic!(
1152                 "non-enum for StructWrappedNullablePointer: {}",
1153                 ty,
1154             ),
1155         };
1156
1157         self.field_path_offset(inner_ty, path)
1158     }
1159
1160     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
1161         let mut offset = Size::from_bytes(0);
1162
1163         // Skip the initial 0 intended for LLVM GEP.
1164         for field_index in path {
1165             let field_offset = self.get_field_offset(ty, field_index)?;
1166             ty = self.get_field_ty(ty, field_index)?;
1167             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
1168         }
1169
1170         Ok(offset)
1171     }
1172
1173     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
1174         match ty.sty {
1175             ty::TyStruct(adt_def, substs) => {
1176                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
1177             }
1178
1179             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1180             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1181             ty::TyBox(ty) => {
1182                 assert_eq!(field_index, 0);
1183                 Ok(ty)
1184             }
1185             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
1186         }
1187     }
1188
1189     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
1190         let layout = self.type_layout(ty);
1191
1192         use rustc::ty::layout::Layout::*;
1193         match *layout {
1194             Univariant { .. } => {
1195                 assert_eq!(field_index, 0);
1196                 Ok(Size::from_bytes(0))
1197             }
1198             FatPointer { .. } => {
1199                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
1200                 Ok(Size::from_bytes(bytes as u64))
1201             }
1202             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
1203         }
1204     }
1205
1206     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
1207         use rustc::mir::repr::Operand::*;
1208         match *op {
1209             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
1210             Constant(mir::Constant { ref literal, .. }) => {
1211                 use rustc::mir::repr::Literal::*;
1212                 match *literal {
1213                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1214                     Item { def_id, substs } => {
1215                         let item_ty = self.tcx.lookup_item_type(def_id).subst(self.tcx, substs);
1216                         if item_ty.ty.is_fn() {
1217                             Err(EvalError::Unimplemented("unimplemented: mentions of function items".to_string()))
1218                         } else {
1219                             let cid = ConstantId::Static{ def_id: def_id, substs: substs };
1220                             Ok(*self.statics.get(&cid).expect("static should have been cached (rvalue)"))
1221                         }
1222                     },
1223                     Promoted { index } => {
1224                         let cid = ConstantId::Promoted {
1225                             def_id: self.frame().def_id,
1226                             substs: self.substs(),
1227                             index: index,
1228                         };
1229                         Ok(*self.statics.get(&cid).expect("a promoted constant hasn't been precomputed"))
1230                     },
1231                 }
1232             }
1233         }
1234     }
1235
1236     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1237         use rustc::mir::repr::Lvalue::*;
1238         let ptr = match *lvalue {
1239             ReturnPointer => self.frame().return_ptr
1240                 .expect("ReturnPointer used in a function with no return value"),
1241             Arg(i) => self.frame().locals[i as usize],
1242             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1243             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1244
1245             Static(def_id) => {
1246                 let substs = self.tcx.mk_substs(subst::Substs::empty());
1247                 let cid = ConstantId::Static{ def_id: def_id, substs: substs };
1248                 *self.gecx.statics.get(&cid).expect("static should have been cached (lvalue)")
1249             },
1250
1251             Projection(ref proj) => {
1252                 let base = self.eval_lvalue(&proj.base)?;
1253                 let base_ty = self.lvalue_ty(&proj.base);
1254                 let base_layout = self.type_layout(base_ty);
1255
1256                 use rustc::mir::repr::ProjectionElem::*;
1257                 match proj.elem {
1258                     Field(field, _) => {
1259                         use rustc::ty::layout::Layout::*;
1260                         let variant = match *base_layout {
1261                             Univariant { ref variant, .. } => variant,
1262                             General { ref variants, .. } => {
1263                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1264                                     &variants[variant_idx]
1265                                 } else {
1266                                     panic!("field access on enum had no variant index");
1267                                 }
1268                             }
1269                             RawNullablePointer { .. } => {
1270                                 assert_eq!(field.index(), 0);
1271                                 return Ok(base);
1272                             }
1273                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1274                             _ => panic!("field access on non-product type: {:?}", base_layout),
1275                         };
1276
1277                         let offset = variant.field_offset(field.index()).bytes();
1278                         base.ptr.offset(offset as isize)
1279                     },
1280
1281                     Downcast(_, variant) => {
1282                         use rustc::ty::layout::Layout::*;
1283                         match *base_layout {
1284                             General { discr, .. } => {
1285                                 return Ok(Lvalue {
1286                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1287                                     extra: LvalueExtra::DowncastVariant(variant),
1288                                 });
1289                             }
1290                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1291                                 return Ok(base);
1292                             }
1293                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1294                         }
1295                     },
1296
1297                     Deref => {
1298                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1299                         let ptr = self.memory.read_ptr(base.ptr)?;
1300                         let extra = match pointee_ty.sty {
1301                             ty::TySlice(_) | ty::TyStr => {
1302                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1303                                 let len = self.memory.read_usize(len_ptr)?;
1304                                 LvalueExtra::Length(len)
1305                             }
1306                             ty::TyTrait(_) => unimplemented!(),
1307                             _ => LvalueExtra::None,
1308                         };
1309                         return Ok(Lvalue { ptr: ptr, extra: extra });
1310                     }
1311
1312                     Index(ref operand) => {
1313                         let elem_size = match base_ty.sty {
1314                             ty::TyArray(elem_ty, _) |
1315                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
1316                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1317                         };
1318                         let n_ptr = self.eval_operand(operand)?;
1319                         let n = self.memory.read_usize(n_ptr)?;
1320                         base.ptr.offset(n as isize * elem_size as isize)
1321                     }
1322
1323                     ConstantIndex { .. } => unimplemented!(),
1324                 }
1325             }
1326         };
1327
1328         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1329     }
1330
1331     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1332         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
1333     }
1334
1335     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1336         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
1337     }
1338
1339     fn monomorphize(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1340         self.gecx.monomorphize(ty, self.substs())
1341     }
1342
1343     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1344         let size = self.type_size(ty);
1345         self.memory.copy(src, dest, size)?;
1346         if self.type_needs_drop(ty) {
1347             self.memory.drop_fill(src, size)?;
1348         }
1349         Ok(())
1350     }
1351
1352     fn type_size(&self, ty: Ty<'tcx>) -> usize {
1353         self.gecx.type_size(ty, self.substs())
1354     }
1355
1356     fn type_layout(&self, ty: Ty<'tcx>) -> &'tcx Layout {
1357         self.gecx.type_layout(ty, self.substs())
1358     }
1359
1360     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1361         use syntax::ast::{IntTy, UintTy};
1362         let val = match (self.memory.pointer_size, &ty.sty) {
1363             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1364             (_, &ty::TyInt(IntTy::I8))    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1365             (2, &ty::TyInt(IntTy::Is)) |
1366             (_, &ty::TyInt(IntTy::I16))   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1367             (4, &ty::TyInt(IntTy::Is)) |
1368             (_, &ty::TyInt(IntTy::I32))   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1369             (8, &ty::TyInt(IntTy::Is)) |
1370             (_, &ty::TyInt(IntTy::I64))   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1371             (_, &ty::TyUint(UintTy::U8))  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1372             (2, &ty::TyUint(UintTy::Us)) |
1373             (_, &ty::TyUint(UintTy::U16)) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1374             (4, &ty::TyUint(UintTy::Us)) |
1375             (_, &ty::TyUint(UintTy::U32)) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1376             (8, &ty::TyUint(UintTy::Us)) |
1377             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1378
1379             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
1380             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
1381                 if self.type_is_sized(ty) {
1382                     match self.memory.read_ptr(ptr) {
1383                         Ok(p) => PrimVal::AbstractPtr(p),
1384                         Err(EvalError::ReadBytesAsPointer) => {
1385                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1386                         }
1387                         Err(e) => return Err(e),
1388                     }
1389                 } else {
1390                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1391                 }
1392             }
1393
1394             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1395         };
1396         Ok(val)
1397     }
1398
1399     fn frame(&self) -> &Frame<'mir, 'tcx> {
1400         self.stack.last().expect("no call frames exist")
1401     }
1402
1403     fn basic_block(&self) -> &mir::BasicBlockData<'tcx> {
1404         let frame = self.frame();
1405         frame.mir.basic_block_data(frame.next_block)
1406     }
1407
1408     fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1409         self.stack.last_mut().expect("no call frames exist")
1410     }
1411
1412     fn mir(&self) -> CachedMir<'mir, 'tcx> {
1413         self.frame().mir.clone()
1414     }
1415
1416     fn substs(&self) -> &'tcx Substs<'tcx> {
1417         self.frame().substs
1418     }
1419 }
1420
1421 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1422     match ptr_ty.sty {
1423         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1424         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1425         ty::TyBox(ty) => {
1426             Some(ty)
1427         }
1428         _ => None,
1429     }
1430 }
1431
1432 impl Lvalue {
1433     fn to_ptr(self) -> Pointer {
1434         assert_eq!(self.extra, LvalueExtra::None);
1435         self.ptr
1436     }
1437 }
1438
1439 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1440     type Target = mir::Mir<'tcx>;
1441     fn deref(&self) -> &mir::Mir<'tcx> {
1442         match *self {
1443             CachedMir::Ref(r) => r,
1444             CachedMir::Owned(ref rc) => rc,
1445         }
1446     }
1447 }
1448
1449 #[derive(Debug)]
1450 pub struct ImplMethod<'tcx> {
1451     pub method: Rc<ty::Method<'tcx>>,
1452     pub substs: &'tcx Substs<'tcx>,
1453     pub is_provided: bool,
1454 }
1455
1456 /// Locates the applicable definition of a method, given its name.
1457 pub fn get_impl_method<'a, 'tcx>(
1458     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1459     impl_def_id: DefId,
1460     substs: &'tcx Substs<'tcx>,
1461     name: ast::Name,
1462 ) -> ImplMethod<'tcx> {
1463     assert!(!substs.types.needs_infer());
1464
1465     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1466     let trait_def = tcx.lookup_trait_def(trait_def_id);
1467
1468     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1469         Some(node_item) => {
1470             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1471                 let substs = traits::translate_substs(&infcx, impl_def_id,
1472                                                       substs, node_item.node);
1473                 tcx.lift(&substs).unwrap_or_else(|| {
1474                     bug!("trans::meth::get_impl_method: translate_substs \
1475                           returned {:?} which contains inference types/regions",
1476                          substs);
1477                 })
1478             });
1479             ImplMethod {
1480                 method: node_item.item,
1481                 substs: substs,
1482                 is_provided: node_item.node.is_from_trait(),
1483             }
1484         }
1485         None => {
1486             bug!("method {:?} not found in {:?}", name, impl_def_id)
1487         }
1488     }
1489 }
1490
1491 pub fn interpret_start_points<'a, 'tcx>(
1492     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1493     mir_map: &MirMap<'tcx>,
1494 ) {
1495     let initial_indentation = ::log_settings::settings().indentation;
1496     for (&id, mir) in &mir_map.map {
1497         for attr in tcx.map.attrs(id) {
1498             use syntax::attr::AttrMetaMethods;
1499             if attr.check_name("miri_run") {
1500                 let item = tcx.map.expect_item(id);
1501
1502                 ::log_settings::settings().indentation = initial_indentation;
1503
1504                 debug!("Interpreting: {}", item.name);
1505
1506                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1507                 match gecx.call(mir, tcx.map.local_def_id(id)) {
1508                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
1509                         gecx.memory.dump(return_ptr.alloc_id);
1510                     },
1511                     Ok(None) => warn!("diverging function returned"),
1512                     Err(_e) => {
1513                         // TODO(solson): Detect whether the error was already reported or not.
1514                         // tcx.sess.err(&e.to_string());
1515                     }
1516                 }
1517             }
1518         }
1519     }
1520 }
1521
1522 // TODO(solson): Upstream these methods into rustc::ty::layout.
1523
1524 trait IntegerExt {
1525     fn size(self) -> Size;
1526 }
1527
1528 impl IntegerExt for layout::Integer {
1529     fn size(self) -> Size {
1530         use rustc::ty::layout::Integer::*;
1531         match self {
1532             I1 | I8 => Size::from_bits(8),
1533             I16 => Size::from_bits(16),
1534             I32 => Size::from_bits(32),
1535             I64 => Size::from_bits(64),
1536         }
1537     }
1538 }
1539
1540 trait StructExt {
1541     fn field_offset(&self, index: usize) -> Size;
1542 }
1543
1544 impl StructExt for layout::Struct {
1545     fn field_offset(&self, index: usize) -> Size {
1546         if index == 0 {
1547             Size::from_bytes(0)
1548         } else {
1549             self.offset_after_field[index - 1]
1550         }
1551     }
1552 }