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