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