src/interpreter.rs

   1 use rustc::middle::const_val;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::mir_map::MirMap;
   4 use rustc::mir::repr as mir;
   5 use rustc::traits::{self, ProjectionMode};
   6 use rustc::ty::fold::TypeFoldable;
   7 use rustc::ty::layout::{self, Layout, Size};
   8 use rustc::ty::subst::{self, Subst, Substs};
   9 use rustc::ty::{self, Ty, TyCtxt};
  10 use rustc::util::nodemap::DefIdMap;
  11 use std::cell::RefCell;
  12 use std::ops::{Deref, DerefMut};
  13 use std::rc::Rc;
  14 use std::{iter, mem};
  15 use syntax::ast;
  16 use syntax::attr;
  17 use syntax::codemap::{self, DUMMY_SP};
  18
  19 use error::{EvalError, EvalResult};
  20 use memory::{Memory, Pointer};
  21 use primval::{self, PrimVal};
  22
  23 const TRACE_EXECUTION: bool = true;
  24
  25 struct GlobalEvalContext<'a, 'tcx: 'a> {
  26     /// The results of the type checker, from rustc.
  27     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  28
  29     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  30     mir_map: &'a MirMap<'tcx>,
  31
  32     /// A local cache from DefIds to Mir for non-crate-local items.
  33     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  34
  35     /// The virtual memory system.
  36     memory: Memory,
  37
  38     /// Another stack containing the type substitutions for the current function invocation. It
  39     /// exists separately from `stack` because it must contain the `Substs` for a function while
  40     /// *creating* the `Frame` for that same function.
  41     substs_stack: Vec<&'tcx Substs<'tcx>>,
  42
  43     // TODO(solson): Merge with `substs_stack`. Also try restructuring `Frame` to accomodate.
  44     /// A stack of the things necessary to print good strack traces:
  45     ///   * Function DefIds and Substs to print proper substituted function names.
  46     ///   * Spans pointing to specific function calls in the source.
  47     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
  48 }
  49
  50 struct FnEvalContext<'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> {
  51     gecx: &'a mut GlobalEvalContext<'b, 'tcx>,
  52
  53     /// The virtual call stack.
  54     stack: Vec<Frame<'mir, 'tcx>>,
  55 }
  56
  57 impl<'a, 'b, 'mir, 'tcx> Deref for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  58     type Target = GlobalEvalContext<'b, 'tcx>;
  59     fn deref(&self) -> &Self::Target {
  60         self.gecx
  61     }
  62 }
  63
  64 impl<'a, 'b, 'mir, 'tcx> DerefMut for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  65     fn deref_mut(&mut self) -> &mut Self::Target {
  66         self.gecx
  67     }
  68 }
  69
  70 /// A stack frame.
  71 struct Frame<'a, 'tcx: 'a> {
  72     /// The MIR for the function called on this frame.
  73     mir: CachedMir<'a, 'tcx>,
  74
  75     /// The block this frame will execute when a function call returns back to this frame.
  76     next_block: mir::BasicBlock,
  77
  78     /// A pointer for writing the return value of the current call if it's not a diverging call.
  79     return_ptr: Option<Pointer>,
  80
  81     /// The list of locals for the current function, stored in order as
  82     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  83     /// and the temporaries at `self.temp_offset`.
  84     locals: Vec<Pointer>,
  85
  86     /// The offset of the first variable in `self.locals`.
  87     var_offset: usize,
  88
  89     /// The offset of the first temporary in `self.locals`.
  90     temp_offset: usize,
  91 }
  92
  93 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  94 struct Lvalue {
  95     ptr: Pointer,
  96     extra: LvalueExtra,
  97 }
  98
  99 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 100 enum LvalueExtra {
 101     None,
 102     Length(u64),
 103     // TODO(solson): Vtable(memory::AllocId),
 104     DowncastVariant(usize),
 105 }
 106
 107 #[derive(Clone)]
 108 enum CachedMir<'mir, 'tcx: 'mir> {
 109     Ref(&'mir mir::Mir<'tcx>),
 110     Owned(Rc<mir::Mir<'tcx>>)
 111 }
 112
 113 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 114 enum TerminatorTarget {
 115     /// Make a local jump to the given block.
 116     Block(mir::BasicBlock),
 117
 118     /// Start executing from the new current frame. (For function calls.)
 119     Call,
 120
 121     /// Stop executing the current frame and resume the previous frame.
 122     Return,
 123 }
 124
 125 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 126     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 127         GlobalEvalContext {
 128             tcx: tcx,
 129             mir_map: mir_map,
 130             mir_cache: RefCell::new(DefIdMap()),
 131             memory: Memory::new(),
 132             substs_stack: Vec::new(),
 133             name_stack: Vec::new(),
 134         }
 135     }
 136 }
 137
 138 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 139     fn new(gecx: &'a mut GlobalEvalContext<'b, 'tcx>) -> Self {
 140         FnEvalContext {
 141             gecx: gecx,
 142             stack: Vec::new(),
 143         }
 144     }
 145
 146     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 147         if let Err(ref e) = r {
 148             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 149             for &(def_id, substs, span) in self.name_stack.iter().rev() {
 150                 // FIXME(solson): Find a way to do this without this Display impl hack.
 151                 use rustc::util::ppaux;
 152                 use std::fmt;
 153                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 154                 impl<'tcx> fmt::Display for Instance<'tcx> {
 155                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 156                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 157                             |tcx| tcx.lookup_item_type(self.0).generics)
 158                     }
 159                 }
 160                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 161             }
 162             err.emit();
 163         }
 164         r
 165     }
 166
 167     fn log<F>(&self, extra_indent: usize, f: F) where F: FnOnce() {
 168         let indent = self.stack.len() + extra_indent;
 169         if !TRACE_EXECUTION { return; }
 170         for _ in 0..indent { print!("    "); }
 171         f();
 172         println!("");
 173     }
 174
 175     fn run(&mut self) -> EvalResult<()> {
 176         'outer: while !self.stack.is_empty() {
 177             let mut current_block = self.frame().next_block;
 178
 179             loop {
 180                 self.log(0, || print!("// {:?}", current_block));
 181                 let current_mir = self.mir().clone(); // Cloning a reference.
 182                 let block_data = current_mir.basic_block_data(current_block);
 183
 184                 for stmt in &block_data.statements {
 185                     self.log(0, || print!("{:?}", stmt));
 186                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 187                     let result = self.eval_assignment(lvalue, rvalue);
 188                     self.maybe_report(stmt.span, result)?;
 189                 }
 190
 191                 let terminator = block_data.terminator();
 192                 self.log(0, || print!("{:?}", terminator.kind));
 193
 194                 let result = self.eval_terminator(terminator);
 195                 match self.maybe_report(terminator.span, result)? {
 196                     TerminatorTarget::Block(block) => current_block = block,
 197                     TerminatorTarget::Return => {
 198                         self.pop_stack_frame();
 199                         self.name_stack.pop();
 200                         continue 'outer;
 201                     }
 202                     TerminatorTarget::Call => continue 'outer,
 203                 }
 204             }
 205         }
 206
 207         Ok(())
 208     }
 209
 210     fn call_nested(&mut self, mir: &mir::Mir<'tcx>) -> EvalResult<Option<Pointer>> {
 211         let mut nested_fecx = FnEvalContext::new(self.gecx);
 212
 213         let return_ptr = match mir.return_ty {
 214             ty::FnConverging(ty) => {
 215                 let size = nested_fecx.type_size(ty);
 216                 Some(nested_fecx.memory.allocate(size))
 217             }
 218             ty::FnDiverging => None,
 219         };
 220
 221         let substs = nested_fecx.substs();
 222         nested_fecx.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
 223         nested_fecx.run()?;
 224         Ok(return_ptr)
 225     }
 226
 227     fn push_stack_frame(&mut self, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
 228         return_ptr: Option<Pointer>)
 229     {
 230         self.substs_stack.push(substs);
 231
 232         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 233         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 234         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 235
 236         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 237             let size = self.type_size(ty);
 238             self.memory.allocate(size)
 239         }).collect();
 240
 241         let num_args = mir.arg_decls.len();
 242         let num_vars = mir.var_decls.len();
 243
 244         self.stack.push(Frame {
 245             mir: mir.clone(),
 246             next_block: mir::START_BLOCK,
 247             return_ptr: return_ptr,
 248             locals: locals,
 249             var_offset: num_args,
 250             temp_offset: num_args + num_vars,
 251         });
 252     }
 253
 254     fn pop_stack_frame(&mut self) {
 255         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 256         // TODO(solson): Deallocate local variables.
 257         self.substs_stack.pop();
 258     }
 259
 260     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 261             -> EvalResult<TerminatorTarget> {
 262         use rustc::mir::repr::TerminatorKind::*;
 263         let target = match terminator.kind {
 264             Return => TerminatorTarget::Return,
 265
 266             Goto { target } => TerminatorTarget::Block(target),
 267
 268             If { ref cond, targets: (then_target, else_target) } => {
 269                 let cond_ptr = self.eval_operand(cond)?;
 270                 let cond_val = self.memory.read_bool(cond_ptr)?;
 271                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 272             }
 273
 274             SwitchInt { ref discr, ref values, ref targets, .. } => {
 275                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 276                 let discr_size = self
 277                     .type_layout(self.lvalue_ty(discr))
 278                     .size(&self.tcx.data_layout)
 279                     .bytes() as usize;
 280                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 281
 282                 // Branch to the `otherwise` case by default, if no match is found.
 283                 let mut target_block = targets[targets.len() - 1];
 284
 285                 for (index, val_const) in values.iter().enumerate() {
 286                     let ptr = self.const_to_ptr(val_const)?;
 287                     let val = self.memory.read_uint(ptr, discr_size)?;
 288                     if discr_val == val {
 289                         target_block = targets[index];
 290                         break;
 291                     }
 292                 }
 293
 294                 TerminatorTarget::Block(target_block)
 295             }
 296
 297             Switch { ref discr, ref targets, adt_def } => {
 298                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 299                 let adt_ty = self.lvalue_ty(discr);
 300                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 301                 let matching = adt_def.variants.iter()
 302                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 303
 304                 match matching {
 305                     Some(i) => TerminatorTarget::Block(targets[i]),
 306                     None => return Err(EvalError::InvalidDiscriminant),
 307                 }
 308             }
 309
 310             Call { ref func, ref args, ref destination, .. } => {
 311                 let mut return_ptr = None;
 312                 if let Some((ref lv, target)) = *destination {
 313                     self.frame_mut().next_block = target;
 314                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 315                 }
 316
 317                 let func_ty = self.operand_ty(func);
 318                 match func_ty.sty {
 319                     ty::TyFnDef(def_id, substs, fn_ty) => {
 320                         use syntax::abi::Abi;
 321                         match fn_ty.abi {
 322                             Abi::RustIntrinsic => {
 323                                 let name = self.tcx.item_name(def_id).as_str();
 324                                 match fn_ty.sig.0.output {
 325                                     ty::FnConverging(ty) => {
 326                                         let size = self.type_size(ty);
 327                                         let ret = return_ptr.unwrap();
 328                                         self.call_intrinsic(&name, substs, args, ret, size)?
 329                                     }
 330                                     ty::FnDiverging => unimplemented!(),
 331                                 }
 332                             }
 333
 334                             Abi::C => {
 335                                 match fn_ty.sig.0.output {
 336                                     ty::FnConverging(ty) => {
 337                                         let size = self.type_size(ty);
 338                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 339                                     }
 340                                     ty::FnDiverging => unimplemented!(),
 341                                 }
 342                             }
 343
 344                             Abi::Rust | Abi::RustCall => {
 345                                 // TODO(solson): Adjust the first argument when calling a Fn or
 346                                 // FnMut closure via FnOnce::call_once.
 347
 348                                 // Only trait methods can have a Self parameter.
 349                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 350                                     self.trait_method(def_id, substs)
 351                                 } else {
 352                                     (def_id, substs)
 353                                 };
 354
 355                                 let mut arg_srcs = Vec::new();
 356                                 for arg in args {
 357                                     let src = self.eval_operand(arg)?;
 358                                     let src_ty = self.operand_ty(arg);
 359                                     arg_srcs.push((src, src_ty));
 360                                 }
 361
 362                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 363                                     arg_srcs.pop();
 364                                     let last_arg = args.last().unwrap();
 365                                     let last = self.eval_operand(last_arg)?;
 366                                     let last_ty = self.operand_ty(last_arg);
 367                                     let last_layout = self.type_layout(last_ty);
 368                                     match (&last_ty.sty, last_layout) {
 369                                         (&ty::TyTuple(fields),
 370                                          &Layout::Univariant { ref variant, .. }) => {
 371                                             let offsets = iter::once(0)
 372                                                 .chain(variant.offset_after_field.iter()
 373                                                     .map(|s| s.bytes()));
 374                                             for (offset, ty) in offsets.zip(fields) {
 375                                                 let src = last.offset(offset as isize);
 376                                                 arg_srcs.push((src, ty));
 377                                             }
 378                                         }
 379                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 380                                     }
 381                                 }
 382
 383                                 let mir = self.load_mir(resolved_def_id);
 384                                 self.name_stack.push((def_id, substs, terminator.span));
 385                                 self.push_stack_frame(mir, resolved_substs, return_ptr);
 386
 387                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 388                                     let dest = self.frame().locals[i];
 389                                     self.move_(src, dest, src_ty)?;
 390                                 }
 391
 392                                 TerminatorTarget::Call
 393                             }
 394
 395                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 396                         }
 397                     }
 398
 399                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 400                 }
 401             }
 402
 403             Drop { ref value, target, .. } => {
 404                 let ptr = self.eval_lvalue(value)?.to_ptr();
 405                 let ty = self.lvalue_ty(value);
 406                 self.drop(ptr, ty)?;
 407                 TerminatorTarget::Block(target)
 408             }
 409
 410             Resume => unimplemented!(),
 411         };
 412
 413         Ok(target)
 414     }
 415
 416     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 417         if !self.type_needs_drop(ty) {
 418             self.log(1, || print!("no need to drop {:?}", ty));
 419             return Ok(());
 420         }
 421         self.log(1, || print!("need to drop {:?}", ty));
 422
 423         // TODO(solson): Call user-defined Drop::drop impls.
 424
 425         match ty.sty {
 426             ty::TyBox(contents_ty) => {
 427                 match self.memory.read_ptr(ptr) {
 428                     Ok(contents_ptr) => {
 429                         self.drop(contents_ptr, contents_ty)?;
 430                         self.log(1, || print!("deallocating box"));
 431                         self.memory.deallocate(contents_ptr)?;
 432                     }
 433                     Err(EvalError::ReadBytesAsPointer) => {
 434                         let size = self.memory.pointer_size;
 435                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 436                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 437                             return Ok(());
 438                         } else {
 439                             return Err(EvalError::ReadBytesAsPointer);
 440                         }
 441                     }
 442                     Err(e) => return Err(e),
 443                 }
 444             }
 445
 446             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 447             _ => {}
 448         }
 449
 450         // Filling drop.
 451         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 452         let size = self.type_size(ty);
 453         self.memory.drop_fill(ptr, size)?;
 454
 455         Ok(())
 456     }
 457
 458     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 459         use rustc::ty::layout::Layout::*;
 460         let adt_layout = self.type_layout(adt_ty);
 461
 462         let discr_val = match *adt_layout {
 463             General { discr, .. } | CEnum { discr, .. } => {
 464                 let discr_size = discr.size().bytes();
 465                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 466             }
 467
 468             RawNullablePointer { nndiscr, .. } => {
 469                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 470             }
 471
 472             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 473                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 474                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 475                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 476             }
 477
 478             // The discriminant_value intrinsic returns 0 for non-sum types.
 479             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 480             Vector { .. } => 0,
 481         };
 482
 483         Ok(discr_val)
 484     }
 485
 486     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 487         let not_null = match self.memory.read_usize(ptr) {
 488             Ok(0) => false,
 489             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 490             Err(e) => return Err(e),
 491         };
 492         assert!(nndiscr == 0 || nndiscr == 1);
 493         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 494     }
 495
 496     fn call_intrinsic(
 497         &mut self,
 498         name: &str,
 499         substs: &'tcx Substs<'tcx>,
 500         args: &[mir::Operand<'tcx>],
 501         dest: Pointer,
 502         dest_size: usize
 503     ) -> EvalResult<TerminatorTarget> {
 504         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 505             .map(|arg| self.eval_operand(arg))
 506             .collect();
 507         let args = args_res?;
 508
 509         match name {
 510             // FIXME(solson): Handle different integer types correctly.
 511             "add_with_overflow" => {
 512                 let ty = *substs.types.get(subst::FnSpace, 0);
 513                 let size = self.type_size(ty);
 514                 let left = self.memory.read_int(args[0], size)?;
 515                 let right = self.memory.read_int(args[1], size)?;
 516                 let (n, overflowed) = unsafe {
 517                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 518                 };
 519                 self.memory.write_int(dest, n, size)?;
 520                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 521             }
 522
 523             "assume" => {}
 524
 525             "copy_nonoverlapping" => {
 526                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 527                 let elem_size = self.type_size(elem_ty);
 528                 let src = self.memory.read_ptr(args[0])?;
 529                 let dest = self.memory.read_ptr(args[1])?;
 530                 let count = self.memory.read_isize(args[2])?;
 531                 self.memory.copy(src, dest, count as usize * elem_size)?;
 532             }
 533
 534             "discriminant_value" => {
 535                 let ty = *substs.types.get(subst::FnSpace, 0);
 536                 let adt_ptr = self.memory.read_ptr(args[0])?;
 537                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 538                 self.memory.write_uint(dest, discr_val, dest_size)?;
 539             }
 540
 541             "forget" => {
 542                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 543                 let arg_size = self.type_size(arg_ty);
 544                 self.memory.drop_fill(args[0], arg_size)?;
 545             }
 546
 547             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 548
 549             "min_align_of" => {
 550                 self.memory.write_int(dest, 1, dest_size)?;
 551             }
 552
 553             "move_val_init" => {
 554                 let ty = *substs.types.get(subst::FnSpace, 0);
 555                 let ptr = self.memory.read_ptr(args[0])?;
 556                 self.move_(args[1], ptr, ty)?;
 557             }
 558
 559             // FIXME(solson): Handle different integer types correctly.
 560             "mul_with_overflow" => {
 561                 let ty = *substs.types.get(subst::FnSpace, 0);
 562                 let size = self.type_size(ty);
 563                 let left = self.memory.read_int(args[0], size)?;
 564                 let right = self.memory.read_int(args[1], size)?;
 565                 let (n, overflowed) = unsafe {
 566                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 567                 };
 568                 self.memory.write_int(dest, n, size)?;
 569                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 570             }
 571
 572             "offset" => {
 573                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 574                 let pointee_size = self.type_size(pointee_ty) as isize;
 575                 let ptr_arg = args[0];
 576                 let offset = self.memory.read_isize(args[1])?;
 577
 578                 match self.memory.read_ptr(ptr_arg) {
 579                     Ok(ptr) => {
 580                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 581                         self.memory.write_ptr(dest, result_ptr)?;
 582                     }
 583                     Err(EvalError::ReadBytesAsPointer) => {
 584                         let addr = self.memory.read_isize(ptr_arg)?;
 585                         let result_addr = addr + offset * pointee_size as i64;
 586                         self.memory.write_isize(dest, result_addr)?;
 587                     }
 588                     Err(e) => return Err(e),
 589                 }
 590             }
 591
 592             // FIXME(solson): Handle different integer types correctly. Use primvals?
 593             "overflowing_sub" => {
 594                 let ty = *substs.types.get(subst::FnSpace, 0);
 595                 let size = self.type_size(ty);
 596                 let left = self.memory.read_int(args[0], size)?;
 597                 let right = self.memory.read_int(args[1], size)?;
 598                 let n = left.wrapping_sub(right);
 599                 self.memory.write_int(dest, n, size)?;
 600             }
 601
 602             "size_of" => {
 603                 let ty = *substs.types.get(subst::FnSpace, 0);
 604                 let size = self.type_size(ty) as u64;
 605                 self.memory.write_uint(dest, size, dest_size)?;
 606             }
 607
 608             "size_of_val" => {
 609                 let ty = *substs.types.get(subst::FnSpace, 0);
 610                 if self.type_is_sized(ty) {
 611                     let size = self.type_size(ty) as u64;
 612                     self.memory.write_uint(dest, size, dest_size)?;
 613                 } else {
 614                     match ty.sty {
 615                         ty::TySlice(_) | ty::TyStr => {
 616                             let elem_ty = ty.sequence_element_type(self.tcx);
 617                             let elem_size = self.type_size(elem_ty) as u64;
 618                             let ptr_size = self.memory.pointer_size as isize;
 619                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 620                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 621                         }
 622
 623                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 624                     }
 625                 }
 626             }
 627
 628             "transmute" => {
 629                 let ty = *substs.types.get(subst::FnSpace, 0);
 630                 self.move_(args[0], dest, ty)?;
 631             }
 632             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 633
 634             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 635         }
 636
 637         // Since we pushed no stack frame, the main loop will act
 638         // as if the call just completed and it's returning to the
 639         // current frame.
 640         Ok(TerminatorTarget::Call)
 641     }
 642
 643     fn call_c_abi(
 644         &mut self,
 645         def_id: DefId,
 646         args: &[mir::Operand<'tcx>],
 647         dest: Pointer,
 648         dest_size: usize,
 649     ) -> EvalResult<TerminatorTarget> {
 650         let name = self.tcx.item_name(def_id);
 651         let attrs = self.tcx.get_attrs(def_id);
 652         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 653             Some(ln) => ln.clone(),
 654             None => name.as_str(),
 655         };
 656
 657         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 658             .map(|arg| self.eval_operand(arg))
 659             .collect();
 660         let args = args_res?;
 661
 662         match &link_name[..] {
 663             "__rust_allocate" => {
 664                 let size = self.memory.read_usize(args[0])?;
 665                 let ptr = self.memory.allocate(size as usize);
 666                 self.memory.write_ptr(dest, ptr)?;
 667             }
 668
 669             "__rust_reallocate" => {
 670                 let ptr = self.memory.read_ptr(args[0])?;
 671                 let size = self.memory.read_usize(args[2])?;
 672                 self.memory.reallocate(ptr, size as usize)?;
 673                 self.memory.write_ptr(dest, ptr)?;
 674             }
 675
 676             "memcmp" => {
 677                 let left = self.memory.read_ptr(args[0])?;
 678                 let right = self.memory.read_ptr(args[1])?;
 679                 let n = self.memory.read_usize(args[2])? as usize;
 680
 681                 let result = {
 682                     let left_bytes = self.memory.read_bytes(left, n)?;
 683                     let right_bytes = self.memory.read_bytes(right, n)?;
 684
 685                     use std::cmp::Ordering::*;
 686                     match left_bytes.cmp(right_bytes) {
 687                         Less => -1,
 688                         Equal => 0,
 689                         Greater => 1,
 690                     }
 691                 };
 692
 693                 self.memory.write_int(dest, result, dest_size)?;
 694             }
 695
 696             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 697         }
 698
 699         // Since we pushed no stack frame, the main loop will act
 700         // as if the call just completed and it's returning to the
 701         // current frame.
 702         Ok(TerminatorTarget::Call)
 703     }
 704
 705     fn assign_fields<I: IntoIterator<Item = u64>>(
 706         &mut self,
 707         dest: Pointer,
 708         offsets: I,
 709         operands: &[mir::Operand<'tcx>],
 710     ) -> EvalResult<()> {
 711         for (offset, operand) in offsets.into_iter().zip(operands) {
 712             let src = self.eval_operand(operand)?;
 713             let src_ty = self.operand_ty(operand);
 714             let field_dest = dest.offset(offset as isize);
 715             self.move_(src, field_dest, src_ty)?;
 716         }
 717         Ok(())
 718     }
 719
 720     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 721         -> EvalResult<()>
 722     {
 723         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 724         let dest_ty = self.lvalue_ty(lvalue);
 725         let dest_layout = self.type_layout(dest_ty);
 726
 727         use rustc::mir::repr::Rvalue::*;
 728         match *rvalue {
 729             Use(ref operand) => {
 730                 let src = self.eval_operand(operand)?;
 731                 self.move_(src, dest, dest_ty)?;
 732             }
 733
 734             BinaryOp(bin_op, ref left, ref right) => {
 735                 let left_ptr = self.eval_operand(left)?;
 736                 let left_ty = self.operand_ty(left);
 737                 let left_val = self.read_primval(left_ptr, left_ty)?;
 738
 739                 let right_ptr = self.eval_operand(right)?;
 740                 let right_ty = self.operand_ty(right);
 741                 let right_val = self.read_primval(right_ptr, right_ty)?;
 742
 743                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 744                 self.memory.write_primval(dest, val)?;
 745             }
 746
 747             UnaryOp(un_op, ref operand) => {
 748                 let ptr = self.eval_operand(operand)?;
 749                 let ty = self.operand_ty(operand);
 750                 let val = self.read_primval(ptr, ty)?;
 751                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 752             }
 753
 754             Aggregate(ref kind, ref operands) => {
 755                 use rustc::ty::layout::Layout::*;
 756                 match *dest_layout {
 757                     Univariant { ref variant, .. } => {
 758                         let offsets = iter::once(0)
 759                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 760                         self.assign_fields(dest, offsets, operands)?;
 761                     }
 762
 763                     Array { .. } => {
 764                         let elem_size = match dest_ty.sty {
 765                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 766                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 767                                         kind, dest_ty),
 768                         };
 769                         let offsets = (0..).map(|i| i * elem_size);
 770                         self.assign_fields(dest, offsets, operands)?;
 771                     }
 772
 773                     General { discr, ref variants, .. } => {
 774                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 775                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 776                             let discr_size = discr.size().bytes() as usize;
 777                             self.memory.write_uint(dest, discr_val, discr_size)?;
 778
 779                             let offsets = variants[variant].offset_after_field.iter()
 780                                 .map(|s| s.bytes());
 781                             self.assign_fields(dest, offsets, operands)?;
 782                         } else {
 783                             panic!("tried to assign {:?} to Layout::General", kind);
 784                         }
 785                     }
 786
 787                     RawNullablePointer { nndiscr, .. } => {
 788                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 789                             if nndiscr == variant as u64 {
 790                                 assert_eq!(operands.len(), 1);
 791                                 let operand = &operands[0];
 792                                 let src = self.eval_operand(operand)?;
 793                                 let src_ty = self.operand_ty(operand);
 794                                 self.move_(src, dest, src_ty)?;
 795                             } else {
 796                                 assert_eq!(operands.len(), 0);
 797                                 self.memory.write_isize(dest, 0)?;
 798                             }
 799                         } else {
 800                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 801                         }
 802                     }
 803
 804                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
 805                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 806                             if nndiscr == variant as u64 {
 807                                 let offsets = iter::once(0)
 808                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
 809                                 try!(self.assign_fields(dest, offsets, operands));
 810                             } else {
 811                                 assert_eq!(operands.len(), 0);
 812                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
 813                                 let dest = dest.offset(offset.bytes() as isize);
 814                                 try!(self.memory.write_isize(dest, 0));
 815                             }
 816                         } else {
 817                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 818                         }
 819                     }
 820
 821                     CEnum { discr, signed, .. } => {
 822                         assert_eq!(operands.len(), 0);
 823                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 824                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 825                             let size = discr.size().bytes() as usize;
 826
 827                             if signed {
 828                                 self.memory.write_int(dest, val as i64, size)?;
 829                             } else {
 830                                 self.memory.write_uint(dest, val, size)?;
 831                             }
 832                         } else {
 833                             panic!("tried to assign {:?} to Layout::CEnum", kind);
 834                         }
 835                     }
 836
 837                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
 838                 }
 839             }
 840
 841             Repeat(ref operand, _) => {
 842                 let (elem_size, length) = match dest_ty.sty {
 843                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
 844                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
 845                 };
 846
 847                 let src = self.eval_operand(operand)?;
 848                 for i in 0..length {
 849                     let elem_dest = dest.offset((i * elem_size) as isize);
 850                     self.memory.copy(src, elem_dest, elem_size)?;
 851                 }
 852             }
 853
 854             Len(ref lvalue) => {
 855                 let src = self.eval_lvalue(lvalue)?;
 856                 let ty = self.lvalue_ty(lvalue);
 857                 let len = match ty.sty {
 858                     ty::TyArray(_, n) => n as u64,
 859                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 860                         n
 861                     } else {
 862                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 863                     },
 864                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 865                 };
 866                 self.memory.write_usize(dest, len)?;
 867             }
 868
 869             Ref(_, _, ref lvalue) => {
 870                 let lv = self.eval_lvalue(lvalue)?;
 871                 self.memory.write_ptr(dest, lv.ptr)?;
 872                 match lv.extra {
 873                     LvalueExtra::None => {},
 874                     LvalueExtra::Length(len) => {
 875                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 876                         self.memory.write_usize(len_ptr, len)?;
 877                     }
 878                     LvalueExtra::DowncastVariant(..) =>
 879                         panic!("attempted to take a reference to an enum downcast lvalue"),
 880                 }
 881             }
 882
 883             Box(ty) => {
 884                 let size = self.type_size(ty);
 885                 let ptr = self.memory.allocate(size);
 886                 self.memory.write_ptr(dest, ptr)?;
 887             }
 888
 889             Cast(kind, ref operand, dest_ty) => {
 890                 let src = self.eval_operand(operand)?;
 891                 let src_ty = self.operand_ty(operand);
 892
 893                 use rustc::mir::repr::CastKind::*;
 894                 match kind {
 895                     Unsize => {
 896                         self.move_(src, dest, src_ty)?;
 897                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 898                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 899
 900                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 901                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 902                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 903                                 self.memory.write_usize(len_ptr, length as u64)?;
 904                             }
 905
 906                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 907                         }
 908                     }
 909
 910                     Misc => {
 911                         // FIXME(solson): Wrong for almost everything.
 912                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
 913                         self.memory.copy(src, dest, size)?;
 914                     }
 915
 916                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 917                 }
 918             }
 919
 920             Slice { .. } => unimplemented!(),
 921             InlineAsm { .. } => unimplemented!(),
 922         }
 923
 924         Ok(())
 925     }
 926
 927     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
 928         // Skip the constant 0 at the start meant for LLVM GEP.
 929         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
 930
 931         // Handle the field index for the outer non-null variant.
 932         let inner_ty = match ty.sty {
 933             ty::TyEnum(adt_def, substs) => {
 934                 let variant = &adt_def.variants[nndiscr as usize];
 935                 let index = path.next().unwrap();
 936                 let field = &variant.fields[index];
 937                 field.ty(self.tcx, substs)
 938             }
 939             _ => panic!(
 940                 "non-enum for StructWrappedNullablePointer: {}",
 941                 ty,
 942             ),
 943         };
 944
 945         self.field_path_offset(inner_ty, path)
 946     }
 947
 948     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
 949         let mut offset = Size::from_bytes(0);
 950
 951         // Skip the initial 0 intended for LLVM GEP.
 952         for field_index in path {
 953             let field_offset = self.get_field_offset(ty, field_index)?;
 954             ty = self.get_field_ty(ty, field_index)?;
 955             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
 956         }
 957
 958         Ok(offset)
 959     }
 960
 961     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
 962         match ty.sty {
 963             ty::TyStruct(adt_def, substs) => {
 964                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
 965             }
 966
 967             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 968             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 969             ty::TyBox(ty) => {
 970                 assert_eq!(field_index, 0);
 971                 Ok(ty)
 972             }
 973             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
 974         }
 975     }
 976
 977     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
 978         let layout = self.type_layout(ty);
 979
 980         use rustc::ty::layout::Layout::*;
 981         match *layout {
 982             Univariant { .. } => {
 983                 assert_eq!(field_index, 0);
 984                 Ok(Size::from_bytes(0))
 985             }
 986             FatPointer { .. } => {
 987                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
 988                 Ok(Size::from_bytes(bytes as u64))
 989             }
 990             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
 991         }
 992     }
 993
 994     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 995         use rustc::mir::repr::Operand::*;
 996         match *op {
 997             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
 998             Constant(mir::Constant { ref literal, .. }) => {
 999                 use rustc::mir::repr::Literal::*;
1000                 match *literal {
1001                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1002                     Item { .. } => unimplemented!(),
1003                     Promoted { index } => {
1004                         // TODO(solson): Mark constants and statics as read-only and cache their
1005                         // values.
1006                         let current_mir = self.mir();
1007                         let mir = &current_mir.promoted[index];
1008                         self.call_nested(mir).map(Option::unwrap)
1009                     }
1010                 }
1011             }
1012         }
1013     }
1014
1015     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1016         use rustc::mir::repr::Lvalue::*;
1017         let ptr = match *lvalue {
1018             ReturnPointer => self.frame().return_ptr
1019                 .expect("ReturnPointer used in a function with no return value"),
1020             Arg(i) => self.frame().locals[i as usize],
1021             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1022             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1023
1024             Static(def_id) => {
1025                 // TODO(solson): Mark constants and statics as read-only and cache their values.
1026                 let mir = self.load_mir(def_id);
1027                 self.call_nested(&mir)?.unwrap()
1028             }
1029
1030             Projection(ref proj) => {
1031                 let base = self.eval_lvalue(&proj.base)?;
1032                 let base_ty = self.lvalue_ty(&proj.base);
1033                 let base_layout = self.type_layout(base_ty);
1034
1035                 use rustc::mir::repr::ProjectionElem::*;
1036                 match proj.elem {
1037                     Field(field, _) => {
1038                         use rustc::ty::layout::Layout::*;
1039                         let variant = match *base_layout {
1040                             Univariant { ref variant, .. } => variant,
1041                             General { ref variants, .. } => {
1042                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1043                                     &variants[variant_idx]
1044                                 } else {
1045                                     panic!("field access on enum had no variant index");
1046                                 }
1047                             }
1048                             RawNullablePointer { .. } => {
1049                                 assert_eq!(field.index(), 0);
1050                                 return Ok(base);
1051                             }
1052                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1053                             _ => panic!("field access on non-product type: {:?}", base_layout),
1054                         };
1055
1056                         let offset = variant.field_offset(field.index()).bytes();
1057                         base.ptr.offset(offset as isize)
1058                     },
1059
1060                     Downcast(_, variant) => {
1061                         use rustc::ty::layout::Layout::*;
1062                         match *base_layout {
1063                             General { discr, .. } => {
1064                                 return Ok(Lvalue {
1065                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1066                                     extra: LvalueExtra::DowncastVariant(variant),
1067                                 });
1068                             }
1069                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1070                                 return Ok(base);
1071                             }
1072                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1073                         }
1074                     },
1075
1076                     Deref => {
1077                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1078                         let ptr = self.memory.read_ptr(base.ptr)?;
1079                         let extra = match pointee_ty.sty {
1080                             ty::TySlice(_) | ty::TyStr => {
1081                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1082                                 let len = self.memory.read_usize(len_ptr)?;
1083                                 LvalueExtra::Length(len)
1084                             }
1085                             ty::TyTrait(_) => unimplemented!(),
1086                             _ => LvalueExtra::None,
1087                         };
1088                         return Ok(Lvalue { ptr: ptr, extra: extra });
1089                     }
1090
1091                     Index(ref operand) => {
1092                         let elem_size = match base_ty.sty {
1093                             ty::TyArray(elem_ty, _) |
1094                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
1095                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1096                         };
1097                         let n_ptr = self.eval_operand(operand)?;
1098                         let n = self.memory.read_usize(n_ptr)?;
1099                         base.ptr.offset(n as isize * elem_size as isize)
1100                     }
1101
1102                     ConstantIndex { .. } => unimplemented!(),
1103                 }
1104             }
1105         };
1106
1107         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1108     }
1109
1110     // TODO(solson): Try making const_to_primval instead.
1111     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
1112         use rustc::middle::const_val::ConstVal::*;
1113         match *const_val {
1114             Float(_f) => unimplemented!(),
1115             Integral(int) => {
1116                 // TODO(solson): Check int constant type.
1117                 let ptr = self.memory.allocate(8);
1118                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
1119                 Ok(ptr)
1120             }
1121             Str(ref s) => {
1122                 let psize = self.memory.pointer_size;
1123                 let static_ptr = self.memory.allocate(s.len());
1124                 let ptr = self.memory.allocate(psize * 2);
1125                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
1126                 self.memory.write_ptr(ptr, static_ptr)?;
1127                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
1128                 Ok(ptr)
1129             }
1130             ByteStr(ref bs) => {
1131                 let psize = self.memory.pointer_size;
1132                 let static_ptr = self.memory.allocate(bs.len());
1133                 let ptr = self.memory.allocate(psize);
1134                 self.memory.write_bytes(static_ptr, bs)?;
1135                 self.memory.write_ptr(ptr, static_ptr)?;
1136                 Ok(ptr)
1137             }
1138             Bool(b) => {
1139                 let ptr = self.memory.allocate(1);
1140                 self.memory.write_bool(ptr, b)?;
1141                 Ok(ptr)
1142             }
1143             Char(_c)          => unimplemented!(),
1144             Struct(_node_id)  => unimplemented!(),
1145             Tuple(_node_id)   => unimplemented!(),
1146             Function(_def_id) => unimplemented!(),
1147             Array(_, _)       => unimplemented!(),
1148             Repeat(_, _)      => unimplemented!(),
1149             Dummy             => unimplemented!(),
1150         }
1151     }
1152
1153     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1154         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
1155     }
1156
1157     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1158         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
1159     }
1160
1161     fn monomorphize(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1162         let substituted = ty.subst(self.tcx, self.substs());
1163         self.tcx.normalize_associated_type(&substituted)
1164     }
1165
1166     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
1167         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
1168     }
1169
1170     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1171         let size = self.type_size(ty);
1172         self.memory.copy(src, dest, size)?;
1173         if self.type_needs_drop(ty) {
1174             self.memory.drop_fill(src, size)?;
1175         }
1176         Ok(())
1177     }
1178
1179     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
1180         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
1181     }
1182
1183     fn type_size(&self, ty: Ty<'tcx>) -> usize {
1184         self.type_layout(ty).size(&self.tcx.data_layout).bytes() as usize
1185     }
1186
1187     fn type_layout(&self, ty: Ty<'tcx>) -> &'tcx Layout {
1188         // TODO(solson): Is this inefficient? Needs investigation.
1189         let ty = self.monomorphize(ty);
1190
1191         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1192             // TODO(solson): Report this error properly.
1193             ty.layout(&infcx).unwrap()
1194         })
1195     }
1196
1197     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1198         use syntax::ast::{IntTy, UintTy};
1199         let val = match ty.sty {
1200             ty::TyBool              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1201             ty::TyInt(IntTy::I8)    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1202             ty::TyInt(IntTy::I16)   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1203             ty::TyInt(IntTy::I32)   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1204             ty::TyInt(IntTy::I64)   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1205             ty::TyUint(UintTy::U8)  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1206             ty::TyUint(UintTy::U16) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1207             ty::TyUint(UintTy::U32) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1208             ty::TyUint(UintTy::U64) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1209
1210             // TODO(solson): Pick the PrimVal dynamically.
1211             ty::TyInt(IntTy::Is)   => PrimVal::I64(self.memory.read_isize(ptr)?),
1212             ty::TyUint(UintTy::Us) => PrimVal::U64(self.memory.read_usize(ptr)?),
1213
1214             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1215             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) => {
1216                 if self.type_is_sized(ty) {
1217                     match self.memory.read_ptr(ptr) {
1218                         Ok(p) => PrimVal::AbstractPtr(p),
1219                         Err(EvalError::ReadBytesAsPointer) => {
1220                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1221                         }
1222                         Err(e) => return Err(e),
1223                     }
1224                 } else {
1225                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1226                 }
1227             }
1228
1229             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1230         };
1231         Ok(val)
1232     }
1233
1234     fn frame(&self) -> &Frame<'mir, 'tcx> {
1235         self.stack.last().expect("no call frames exist")
1236     }
1237
1238     fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1239         self.stack.last_mut().expect("no call frames exist")
1240     }
1241
1242     fn mir(&self) -> CachedMir<'mir, 'tcx> {
1243         self.frame().mir.clone()
1244     }
1245
1246     fn substs(&self) -> &'tcx Substs<'tcx> {
1247         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
1248     }
1249
1250     fn load_mir(&self, def_id: DefId) -> CachedMir<'mir, 'tcx> {
1251         match self.tcx.map.as_local_node_id(def_id) {
1252             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
1253             None => {
1254                 let mut mir_cache = self.mir_cache.borrow_mut();
1255                 if let Some(mir) = mir_cache.get(&def_id) {
1256                     return CachedMir::Owned(mir.clone());
1257                 }
1258
1259                 let cs = &self.tcx.sess.cstore;
1260                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1261                     panic!("no mir for {:?}", def_id);
1262                 });
1263                 let cached = Rc::new(mir);
1264                 mir_cache.insert(def_id, cached.clone());
1265                 CachedMir::Owned(cached)
1266             }
1267         }
1268     }
1269
1270     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1271         // Do the initial selection for the obligation. This yields the shallow result we are
1272         // looking for -- that is, what specific impl.
1273         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1274             let mut selcx = traits::SelectionContext::new(&infcx);
1275
1276             let obligation = traits::Obligation::new(
1277                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1278                 trait_ref.to_poly_trait_predicate(),
1279             );
1280             let selection = selcx.select(&obligation).unwrap().unwrap();
1281
1282             // Currently, we use a fulfillment context to completely resolve all nested obligations.
1283             // This is because they can inform the inference of the impl's type parameters.
1284             let mut fulfill_cx = traits::FulfillmentContext::new();
1285             let vtable = selection.map(|predicate| {
1286                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
1287             });
1288             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
1289         })
1290     }
1291
1292     /// Trait method, which has to be resolved to an impl method.
1293     pub fn trait_method(
1294         &self,
1295         def_id: DefId,
1296         substs: &'tcx Substs<'tcx>
1297     ) -> (DefId, &'tcx Substs<'tcx>) {
1298         let method_item = self.tcx.impl_or_trait_item(def_id);
1299         let trait_id = method_item.container().id();
1300         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1301         match self.fulfill_obligation(trait_ref) {
1302             traits::VtableImpl(vtable_impl) => {
1303                 let impl_did = vtable_impl.impl_def_id;
1304                 let mname = self.tcx.item_name(def_id);
1305                 // Create a concatenated set of substitutions which includes those from the impl
1306                 // and those from the method:
1307                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1308                 let substs = self.tcx.mk_substs(impl_substs);
1309                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1310
1311                 (mth.method.def_id, mth.substs)
1312             }
1313
1314             traits::VtableClosure(vtable_closure) =>
1315                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1316
1317             traits::VtableFnPointer(_fn_ty) => {
1318                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1319                 unimplemented!()
1320                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1321
1322                 // let method_ty = def_ty(tcx, def_id, substs);
1323                 // let fn_ptr_ty = match method_ty.sty {
1324                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1325                 //     _ => unreachable!("expected fn item type, found {}",
1326                 //                       method_ty)
1327                 // };
1328                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1329             }
1330
1331             traits::VtableObject(ref _data) => {
1332                 unimplemented!()
1333                 // Callee {
1334                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1335                 //                   tcx, data, def_id)),
1336                 //                   ty: def_ty(tcx, def_id, substs)
1337                 // }
1338             }
1339             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1340         }
1341     }
1342 }
1343
1344 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1345     match ptr_ty.sty {
1346         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1347         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1348         ty::TyBox(ty) => {
1349             Some(ty)
1350         }
1351         _ => None,
1352     }
1353 }
1354
1355 impl Lvalue {
1356     fn to_ptr(self) -> Pointer {
1357         assert_eq!(self.extra, LvalueExtra::None);
1358         self.ptr
1359     }
1360 }
1361
1362 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1363     type Target = mir::Mir<'tcx>;
1364     fn deref(&self) -> &mir::Mir<'tcx> {
1365         match *self {
1366             CachedMir::Ref(r) => r,
1367             CachedMir::Owned(ref rc) => rc,
1368         }
1369     }
1370 }
1371
1372 #[derive(Debug)]
1373 pub struct ImplMethod<'tcx> {
1374     pub method: Rc<ty::Method<'tcx>>,
1375     pub substs: &'tcx Substs<'tcx>,
1376     pub is_provided: bool,
1377 }
1378
1379 /// Locates the applicable definition of a method, given its name.
1380 pub fn get_impl_method<'a, 'tcx>(
1381     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1382     impl_def_id: DefId,
1383     substs: &'tcx Substs<'tcx>,
1384     name: ast::Name,
1385 ) -> ImplMethod<'tcx> {
1386     assert!(!substs.types.needs_infer());
1387
1388     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1389     let trait_def = tcx.lookup_trait_def(trait_def_id);
1390
1391     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1392         Some(node_item) => {
1393             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1394                 let substs = traits::translate_substs(&infcx, impl_def_id,
1395                                                       substs, node_item.node);
1396                 tcx.lift(&substs).unwrap_or_else(|| {
1397                     bug!("trans::meth::get_impl_method: translate_substs \
1398                           returned {:?} which contains inference types/regions",
1399                          substs);
1400                 })
1401             });
1402             ImplMethod {
1403                 method: node_item.item,
1404                 substs: substs,
1405                 is_provided: node_item.node.is_from_trait(),
1406             }
1407         }
1408         None => {
1409             bug!("method {:?} not found in {:?}", name, impl_def_id)
1410         }
1411     }
1412 }
1413
1414 pub fn interpret_start_points<'a, 'tcx>(
1415     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1416     mir_map: &MirMap<'tcx>,
1417 ) {
1418     for (&id, mir) in &mir_map.map {
1419         for attr in tcx.map.attrs(id) {
1420             use syntax::attr::AttrMetaMethods;
1421             if attr.check_name("miri_run") {
1422                 let item = tcx.map.expect_item(id);
1423
1424                 if TRACE_EXECUTION {
1425                     println!("Interpreting: {}", item.name);
1426                 }
1427
1428                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1429                 let mut fecx = FnEvalContext::new(&mut gecx);
1430                 match fecx.call_nested(mir) {
1431                     Ok(Some(return_ptr)) => if TRACE_EXECUTION {
1432                         fecx.memory.dump(return_ptr.alloc_id);
1433                     },
1434                     Ok(None) => println!("(diverging function returned)"),
1435                     Err(_e) => {
1436                         // TODO(solson): Detect whether the error was already reported or not.
1437                         // tcx.sess.err(&e.to_string());
1438                     }
1439                 }
1440
1441                 if TRACE_EXECUTION {
1442                     println!("");
1443                 }
1444             }
1445         }
1446     }
1447 }
1448
1449 // TODO(solson): Upstream these methods into rustc::ty::layout.
1450
1451 trait IntegerExt {
1452     fn size(self) -> Size;
1453 }
1454
1455 impl IntegerExt for layout::Integer {
1456     fn size(self) -> Size {
1457         use rustc::ty::layout::Integer::*;
1458         match self {
1459             I1 | I8 => Size::from_bits(8),
1460             I16 => Size::from_bits(16),
1461             I32 => Size::from_bits(32),
1462             I64 => Size::from_bits(64),
1463         }
1464     }
1465 }
1466
1467 trait StructExt {
1468     fn field_offset(&self, index: usize) -> Size;
1469 }
1470
1471 impl StructExt for layout::Struct {
1472     fn field_offset(&self, index: usize) -> Size {
1473         if index == 0 {
1474             Size::from_bytes(0)
1475         } else {
1476             self.offset_after_field[index - 1]
1477         }
1478     }
1479 }