src/interpreter.rs

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