src/interpreter.rs

   1 use rustc::middle::const_val;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::mir_map::MirMap;
   4 use rustc::mir::repr as mir;
   5 use rustc::traits::{self, ProjectionMode};
   6 use rustc::ty::fold::TypeFoldable;
   7 use rustc::ty::layout::{self, Layout, Size};
   8 use rustc::ty::subst::{self, Subst, Substs};
   9 use rustc::ty::{self, Ty, TyCtxt};
  10 use rustc::util::nodemap::DefIdMap;
  11 use std::cell::RefCell;
  12 use std::ops::{Deref, DerefMut};
  13 use std::rc::Rc;
  14 use std::{iter, mem};
  15 use syntax::ast;
  16 use syntax::attr;
  17 use syntax::codemap::{self, DUMMY_SP};
  18
  19 use error::{EvalError, EvalResult};
  20 use memory::{Memory, Pointer};
  21 use primval::{self, PrimVal};
  22
  23 const TRACE_EXECUTION: bool = true;
  24
  25 struct GlobalEvalContext<'a, 'tcx: 'a> {
  26     /// The results of the type checker, from rustc.
  27     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  28
  29     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  30     mir_map: &'a MirMap<'tcx>,
  31
  32     /// A local cache from DefIds to Mir for non-crate-local items.
  33     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  34
  35     /// The virtual memory system.
  36     memory: Memory,
  37
  38     /// Another stack containing the type substitutions for the current function invocation. It
  39     /// exists separately from `stack` because it must contain the `Substs` for a function while
  40     /// *creating* the `Frame` for that same function.
  41     substs_stack: Vec<&'tcx Substs<'tcx>>,
  42
  43     // TODO(solson): Merge with `substs_stack`. Also try restructuring `Frame` to accomodate.
  44     /// A stack of the things necessary to print good strack traces:
  45     ///   * Function DefIds and Substs to print proper substituted function names.
  46     ///   * Spans pointing to specific function calls in the source.
  47     name_stack: Vec<(DefId, &'tcx Substs<'tcx>, codemap::Span)>,
  48 }
  49
  50 struct FnEvalContext<'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> {
  51     gecx: &'a mut GlobalEvalContext<'b, 'tcx>,
  52
  53     /// The virtual call stack.
  54     stack: Vec<Frame<'mir, 'tcx>>,
  55 }
  56
  57 impl<'a, 'b, 'mir, 'tcx> Deref for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  58     type Target = GlobalEvalContext<'b, 'tcx>;
  59     fn deref(&self) -> &Self::Target {
  60         self.gecx
  61     }
  62 }
  63
  64 impl<'a, 'b, 'mir, 'tcx> DerefMut for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  65     fn deref_mut(&mut self) -> &mut Self::Target {
  66         self.gecx
  67     }
  68 }
  69
  70 /// A stack frame.
  71 struct Frame<'a, 'tcx: 'a> {
  72     /// The MIR for the function called on this frame.
  73     mir: CachedMir<'a, 'tcx>,
  74
  75     /// The block this frame will execute when a function call returns back to this frame.
  76     next_block: mir::BasicBlock,
  77
  78     /// A pointer for writing the return value of the current call if it's not a diverging call.
  79     return_ptr: Option<Pointer>,
  80
  81     /// The list of locals for the current function, stored in order as
  82     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  83     /// and the temporaries at `self.temp_offset`.
  84     locals: Vec<Pointer>,
  85
  86     /// The offset of the first variable in `self.locals`.
  87     var_offset: usize,
  88
  89     /// The offset of the first temporary in `self.locals`.
  90     temp_offset: usize,
  91 }
  92
  93 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
  94 struct Lvalue {
  95     ptr: Pointer,
  96     extra: LvalueExtra,
  97 }
  98
  99 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 100 enum LvalueExtra {
 101     None,
 102     Length(u64),
 103     // TODO(solson): Vtable(memory::AllocId),
 104     DowncastVariant(usize),
 105 }
 106
 107 #[derive(Clone)]
 108 enum CachedMir<'mir, 'tcx: 'mir> {
 109     Ref(&'mir mir::Mir<'tcx>),
 110     Owned(Rc<mir::Mir<'tcx>>)
 111 }
 112
 113 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 114 enum TerminatorTarget {
 115     /// Make a local jump to the given block.
 116     Block(mir::BasicBlock),
 117
 118     /// Start executing from the new current frame. (For function calls.)
 119     Call,
 120
 121     /// Stop executing the current frame and resume the previous frame.
 122     Return,
 123 }
 124
 125 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 126     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 127         GlobalEvalContext {
 128             tcx: tcx,
 129             mir_map: mir_map,
 130             mir_cache: RefCell::new(DefIdMap()),
 131             memory: Memory::new(tcx.sess
 132                                    .target
 133                                    .uint_type
 134                                    .bit_width()
 135                                    .expect("Session::target::uint_type was usize")/8),
 136             substs_stack: Vec::new(),
 137             name_stack: Vec::new(),
 138         }
 139     }
 140 }
 141
 142 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 143     fn new(gecx: &'a mut GlobalEvalContext<'b, 'tcx>) -> Self {
 144         FnEvalContext {
 145             gecx: gecx,
 146             stack: Vec::new(),
 147         }
 148     }
 149
 150     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 151         if let Err(ref e) = r {
 152             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 153             for &(def_id, substs, span) in self.name_stack.iter().rev() {
 154                 // FIXME(solson): Find a way to do this without this Display impl hack.
 155                 use rustc::util::ppaux;
 156                 use std::fmt;
 157                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 158                 impl<'tcx> fmt::Display for Instance<'tcx> {
 159                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 160                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 161                             |tcx| tcx.lookup_item_type(self.0).generics)
 162                     }
 163                 }
 164                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 165             }
 166             err.emit();
 167         }
 168         r
 169     }
 170
 171     fn log<F>(&self, extra_indent: usize, f: F) where F: FnOnce() {
 172         let indent = self.stack.len() + extra_indent;
 173         if !TRACE_EXECUTION { return; }
 174         for _ in 0..indent { print!("    "); }
 175         f();
 176         println!("");
 177     }
 178
 179     fn run(&mut self) -> EvalResult<()> {
 180         'outer: while !self.stack.is_empty() {
 181             let mut current_block = self.frame().next_block;
 182
 183             loop {
 184                 self.log(0, || print!("// {:?}", current_block));
 185                 let current_mir = self.mir().clone(); // Cloning a reference.
 186                 let block_data = current_mir.basic_block_data(current_block);
 187
 188                 for stmt in &block_data.statements {
 189                     self.log(0, || print!("{:?}", stmt));
 190                     let mir::StatementKind::Assign(ref lvalue, ref rvalue) = stmt.kind;
 191                     let result = self.eval_assignment(lvalue, rvalue);
 192                     self.maybe_report(stmt.span, result)?;
 193                 }
 194
 195                 let terminator = block_data.terminator();
 196                 self.log(0, || print!("{:?}", terminator.kind));
 197
 198                 let result = self.eval_terminator(terminator);
 199                 match self.maybe_report(terminator.span, result)? {
 200                     TerminatorTarget::Block(block) => current_block = block,
 201                     TerminatorTarget::Return => {
 202                         self.pop_stack_frame();
 203                         self.name_stack.pop();
 204                         continue 'outer;
 205                     }
 206                     TerminatorTarget::Call => continue 'outer,
 207                 }
 208             }
 209         }
 210
 211         Ok(())
 212     }
 213
 214     fn call_nested(&mut self, mir: &mir::Mir<'tcx>) -> EvalResult<Option<Pointer>> {
 215         let mut nested_fecx = FnEvalContext::new(self.gecx);
 216
 217         let return_ptr = match mir.return_ty {
 218             ty::FnConverging(ty) => {
 219                 let size = nested_fecx.type_size(ty);
 220                 Some(nested_fecx.memory.allocate(size))
 221             }
 222             ty::FnDiverging => None,
 223         };
 224
 225         let substs = nested_fecx.substs();
 226         nested_fecx.push_stack_frame(CachedMir::Ref(mir), substs, return_ptr);
 227         nested_fecx.run()?;
 228         Ok(return_ptr)
 229     }
 230
 231     fn push_stack_frame(&mut self, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
 232         return_ptr: Option<Pointer>)
 233     {
 234         self.substs_stack.push(substs);
 235
 236         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 237         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 238         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 239
 240         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 241             let size = self.type_size(ty);
 242             self.memory.allocate(size)
 243         }).collect();
 244
 245         let num_args = mir.arg_decls.len();
 246         let num_vars = mir.var_decls.len();
 247
 248         self.stack.push(Frame {
 249             mir: mir.clone(),
 250             next_block: mir::START_BLOCK,
 251             return_ptr: return_ptr,
 252             locals: locals,
 253             var_offset: num_args,
 254             temp_offset: num_args + num_vars,
 255         });
 256     }
 257
 258     fn pop_stack_frame(&mut self) {
 259         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 260         // TODO(solson): Deallocate local variables.
 261         self.substs_stack.pop();
 262     }
 263
 264     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 265             -> EvalResult<TerminatorTarget> {
 266         use rustc::mir::repr::TerminatorKind::*;
 267         let target = match terminator.kind {
 268             Return => TerminatorTarget::Return,
 269
 270             Goto { target } => TerminatorTarget::Block(target),
 271
 272             If { ref cond, targets: (then_target, else_target) } => {
 273                 let cond_ptr = self.eval_operand(cond)?;
 274                 let cond_val = self.memory.read_bool(cond_ptr)?;
 275                 TerminatorTarget::Block(if cond_val { then_target } else { else_target })
 276             }
 277
 278             SwitchInt { ref discr, ref values, ref targets, .. } => {
 279                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 280                 let discr_size = self
 281                     .type_layout(self.lvalue_ty(discr))
 282                     .size(&self.tcx.data_layout)
 283                     .bytes() as usize;
 284                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 285
 286                 // Branch to the `otherwise` case by default, if no match is found.
 287                 let mut target_block = targets[targets.len() - 1];
 288
 289                 for (index, val_const) in values.iter().enumerate() {
 290                     let ptr = self.const_to_ptr(val_const)?;
 291                     let val = self.memory.read_uint(ptr, discr_size)?;
 292                     if discr_val == val {
 293                         target_block = targets[index];
 294                         break;
 295                     }
 296                 }
 297
 298                 TerminatorTarget::Block(target_block)
 299             }
 300
 301             Switch { ref discr, ref targets, adt_def } => {
 302                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 303                 let adt_ty = self.lvalue_ty(discr);
 304                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 305                 let matching = adt_def.variants.iter()
 306                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 307
 308                 match matching {
 309                     Some(i) => TerminatorTarget::Block(targets[i]),
 310                     None => return Err(EvalError::InvalidDiscriminant),
 311                 }
 312             }
 313
 314             Call { ref func, ref args, ref destination, .. } => {
 315                 let mut return_ptr = None;
 316                 if let Some((ref lv, target)) = *destination {
 317                     self.frame_mut().next_block = target;
 318                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 319                 }
 320
 321                 let func_ty = self.operand_ty(func);
 322                 match func_ty.sty {
 323                     ty::TyFnDef(def_id, substs, fn_ty) => {
 324                         use syntax::abi::Abi;
 325                         match fn_ty.abi {
 326                             Abi::RustIntrinsic => {
 327                                 let name = self.tcx.item_name(def_id).as_str();
 328                                 match fn_ty.sig.0.output {
 329                                     ty::FnConverging(ty) => {
 330                                         let size = self.type_size(ty);
 331                                         let ret = return_ptr.unwrap();
 332                                         self.call_intrinsic(&name, substs, args, ret, size)?
 333                                     }
 334                                     ty::FnDiverging => unimplemented!(),
 335                                 }
 336                             }
 337
 338                             Abi::C => {
 339                                 match fn_ty.sig.0.output {
 340                                     ty::FnConverging(ty) => {
 341                                         let size = self.type_size(ty);
 342                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 343                                     }
 344                                     ty::FnDiverging => unimplemented!(),
 345                                 }
 346                             }
 347
 348                             Abi::Rust | Abi::RustCall => {
 349                                 // TODO(solson): Adjust the first argument when calling a Fn or
 350                                 // FnMut closure via FnOnce::call_once.
 351
 352                                 // Only trait methods can have a Self parameter.
 353                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 354                                     self.trait_method(def_id, substs)
 355                                 } else {
 356                                     (def_id, substs)
 357                                 };
 358
 359                                 let mut arg_srcs = Vec::new();
 360                                 for arg in args {
 361                                     let src = self.eval_operand(arg)?;
 362                                     let src_ty = self.operand_ty(arg);
 363                                     arg_srcs.push((src, src_ty));
 364                                 }
 365
 366                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 367                                     arg_srcs.pop();
 368                                     let last_arg = args.last().unwrap();
 369                                     let last = self.eval_operand(last_arg)?;
 370                                     let last_ty = self.operand_ty(last_arg);
 371                                     let last_layout = self.type_layout(last_ty);
 372                                     match (&last_ty.sty, last_layout) {
 373                                         (&ty::TyTuple(fields),
 374                                          &Layout::Univariant { ref variant, .. }) => {
 375                                             let offsets = iter::once(0)
 376                                                 .chain(variant.offset_after_field.iter()
 377                                                     .map(|s| s.bytes()));
 378                                             for (offset, ty) in offsets.zip(fields) {
 379                                                 let src = last.offset(offset as isize);
 380                                                 arg_srcs.push((src, ty));
 381                                             }
 382                                         }
 383                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 384                                     }
 385                                 }
 386
 387                                 let mir = self.load_mir(resolved_def_id);
 388                                 self.name_stack.push((def_id, substs, terminator.span));
 389                                 self.push_stack_frame(mir, resolved_substs, return_ptr);
 390
 391                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 392                                     let dest = self.frame().locals[i];
 393                                     self.move_(src, dest, src_ty)?;
 394                                 }
 395
 396                                 TerminatorTarget::Call
 397                             }
 398
 399                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 400                         }
 401                     }
 402
 403                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 404                 }
 405             }
 406
 407             Drop { ref value, target, .. } => {
 408                 let ptr = self.eval_lvalue(value)?.to_ptr();
 409                 let ty = self.lvalue_ty(value);
 410                 self.drop(ptr, ty)?;
 411                 TerminatorTarget::Block(target)
 412             }
 413
 414             Resume => unimplemented!(),
 415         };
 416
 417         Ok(target)
 418     }
 419
 420     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 421         if !self.type_needs_drop(ty) {
 422             self.log(1, || print!("no need to drop {:?}", ty));
 423             return Ok(());
 424         }
 425         self.log(1, || print!("need to drop {:?}", ty));
 426
 427         // TODO(solson): Call user-defined Drop::drop impls.
 428
 429         match ty.sty {
 430             ty::TyBox(contents_ty) => {
 431                 match self.memory.read_ptr(ptr) {
 432                     Ok(contents_ptr) => {
 433                         self.drop(contents_ptr, contents_ty)?;
 434                         self.log(1, || print!("deallocating box"));
 435                         self.memory.deallocate(contents_ptr)?;
 436                     }
 437                     Err(EvalError::ReadBytesAsPointer) => {
 438                         let size = self.memory.pointer_size;
 439                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 440                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 441                             return Ok(());
 442                         } else {
 443                             return Err(EvalError::ReadBytesAsPointer);
 444                         }
 445                     }
 446                     Err(e) => return Err(e),
 447                 }
 448             }
 449
 450             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 451             _ => {}
 452         }
 453
 454         // Filling drop.
 455         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 456         let size = self.type_size(ty);
 457         self.memory.drop_fill(ptr, size)?;
 458
 459         Ok(())
 460     }
 461
 462     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 463         use rustc::ty::layout::Layout::*;
 464         let adt_layout = self.type_layout(adt_ty);
 465
 466         let discr_val = match *adt_layout {
 467             General { discr, .. } | CEnum { discr, .. } => {
 468                 let discr_size = discr.size().bytes();
 469                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 470             }
 471
 472             RawNullablePointer { nndiscr, .. } => {
 473                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 474             }
 475
 476             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 477                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 478                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 479                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 480             }
 481
 482             // The discriminant_value intrinsic returns 0 for non-sum types.
 483             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 484             Vector { .. } => 0,
 485         };
 486
 487         Ok(discr_val)
 488     }
 489
 490     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 491         let not_null = match self.memory.read_usize(ptr) {
 492             Ok(0) => false,
 493             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 494             Err(e) => return Err(e),
 495         };
 496         assert!(nndiscr == 0 || nndiscr == 1);
 497         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 498     }
 499
 500     fn call_intrinsic(
 501         &mut self,
 502         name: &str,
 503         substs: &'tcx Substs<'tcx>,
 504         args: &[mir::Operand<'tcx>],
 505         dest: Pointer,
 506         dest_size: usize
 507     ) -> EvalResult<TerminatorTarget> {
 508         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 509             .map(|arg| self.eval_operand(arg))
 510             .collect();
 511         let args = args_res?;
 512
 513         match name {
 514             // FIXME(solson): Handle different integer types correctly.
 515             "add_with_overflow" => {
 516                 let ty = *substs.types.get(subst::FnSpace, 0);
 517                 let size = self.type_size(ty);
 518                 let left = self.memory.read_int(args[0], size)?;
 519                 let right = self.memory.read_int(args[1], size)?;
 520                 let (n, overflowed) = unsafe {
 521                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 522                 };
 523                 self.memory.write_int(dest, n, size)?;
 524                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 525             }
 526
 527             "assume" => {}
 528
 529             "copy_nonoverlapping" => {
 530                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 531                 let elem_size = self.type_size(elem_ty);
 532                 let src = self.memory.read_ptr(args[0])?;
 533                 let dest = self.memory.read_ptr(args[1])?;
 534                 let count = self.memory.read_isize(args[2])?;
 535                 self.memory.copy(src, dest, count as usize * elem_size)?;
 536             }
 537
 538             "discriminant_value" => {
 539                 let ty = *substs.types.get(subst::FnSpace, 0);
 540                 let adt_ptr = self.memory.read_ptr(args[0])?;
 541                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 542                 self.memory.write_uint(dest, discr_val, dest_size)?;
 543             }
 544
 545             "forget" => {
 546                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 547                 let arg_size = self.type_size(arg_ty);
 548                 self.memory.drop_fill(args[0], arg_size)?;
 549             }
 550
 551             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 552
 553             "min_align_of" => {
 554                 self.memory.write_int(dest, 1, dest_size)?;
 555             }
 556
 557             "move_val_init" => {
 558                 let ty = *substs.types.get(subst::FnSpace, 0);
 559                 let ptr = self.memory.read_ptr(args[0])?;
 560                 self.move_(args[1], ptr, ty)?;
 561             }
 562
 563             // FIXME(solson): Handle different integer types correctly.
 564             "mul_with_overflow" => {
 565                 let ty = *substs.types.get(subst::FnSpace, 0);
 566                 let size = self.type_size(ty);
 567                 let left = self.memory.read_int(args[0], size)?;
 568                 let right = self.memory.read_int(args[1], size)?;
 569                 let (n, overflowed) = unsafe {
 570                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 571                 };
 572                 self.memory.write_int(dest, n, size)?;
 573                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 574             }
 575
 576             "offset" => {
 577                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 578                 let pointee_size = self.type_size(pointee_ty) as isize;
 579                 let ptr_arg = args[0];
 580                 let offset = self.memory.read_isize(args[1])?;
 581
 582                 match self.memory.read_ptr(ptr_arg) {
 583                     Ok(ptr) => {
 584                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 585                         self.memory.write_ptr(dest, result_ptr)?;
 586                     }
 587                     Err(EvalError::ReadBytesAsPointer) => {
 588                         let addr = self.memory.read_isize(ptr_arg)?;
 589                         let result_addr = addr + offset * pointee_size as i64;
 590                         self.memory.write_isize(dest, result_addr)?;
 591                     }
 592                     Err(e) => return Err(e),
 593                 }
 594             }
 595
 596             // FIXME(solson): Handle different integer types correctly. Use primvals?
 597             "overflowing_sub" => {
 598                 let ty = *substs.types.get(subst::FnSpace, 0);
 599                 let size = self.type_size(ty);
 600                 let left = self.memory.read_int(args[0], size)?;
 601                 let right = self.memory.read_int(args[1], size)?;
 602                 let n = left.wrapping_sub(right);
 603                 self.memory.write_int(dest, n, size)?;
 604             }
 605
 606             "size_of" => {
 607                 let ty = *substs.types.get(subst::FnSpace, 0);
 608                 let size = self.type_size(ty) as u64;
 609                 self.memory.write_uint(dest, size, dest_size)?;
 610             }
 611
 612             "size_of_val" => {
 613                 let ty = *substs.types.get(subst::FnSpace, 0);
 614                 if self.type_is_sized(ty) {
 615                     let size = self.type_size(ty) as u64;
 616                     self.memory.write_uint(dest, size, dest_size)?;
 617                 } else {
 618                     match ty.sty {
 619                         ty::TySlice(_) | ty::TyStr => {
 620                             let elem_ty = ty.sequence_element_type(self.tcx);
 621                             let elem_size = self.type_size(elem_ty) as u64;
 622                             let ptr_size = self.memory.pointer_size as isize;
 623                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 624                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 625                         }
 626
 627                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 628                     }
 629                 }
 630             }
 631
 632             "transmute" => {
 633                 let ty = *substs.types.get(subst::FnSpace, 0);
 634                 self.move_(args[0], dest, ty)?;
 635             }
 636             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 637
 638             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 639         }
 640
 641         // Since we pushed no stack frame, the main loop will act
 642         // as if the call just completed and it's returning to the
 643         // current frame.
 644         Ok(TerminatorTarget::Call)
 645     }
 646
 647     fn call_c_abi(
 648         &mut self,
 649         def_id: DefId,
 650         args: &[mir::Operand<'tcx>],
 651         dest: Pointer,
 652         dest_size: usize,
 653     ) -> EvalResult<TerminatorTarget> {
 654         let name = self.tcx.item_name(def_id);
 655         let attrs = self.tcx.get_attrs(def_id);
 656         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 657             Some(ln) => ln.clone(),
 658             None => name.as_str(),
 659         };
 660
 661         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 662             .map(|arg| self.eval_operand(arg))
 663             .collect();
 664         let args = args_res?;
 665
 666         match &link_name[..] {
 667             "__rust_allocate" => {
 668                 let size = self.memory.read_usize(args[0])?;
 669                 let ptr = self.memory.allocate(size as usize);
 670                 self.memory.write_ptr(dest, ptr)?;
 671             }
 672
 673             "__rust_reallocate" => {
 674                 let ptr = self.memory.read_ptr(args[0])?;
 675                 let size = self.memory.read_usize(args[2])?;
 676                 self.memory.reallocate(ptr, size as usize)?;
 677                 self.memory.write_ptr(dest, ptr)?;
 678             }
 679
 680             "memcmp" => {
 681                 let left = self.memory.read_ptr(args[0])?;
 682                 let right = self.memory.read_ptr(args[1])?;
 683                 let n = self.memory.read_usize(args[2])? as usize;
 684
 685                 let result = {
 686                     let left_bytes = self.memory.read_bytes(left, n)?;
 687                     let right_bytes = self.memory.read_bytes(right, n)?;
 688
 689                     use std::cmp::Ordering::*;
 690                     match left_bytes.cmp(right_bytes) {
 691                         Less => -1,
 692                         Equal => 0,
 693                         Greater => 1,
 694                     }
 695                 };
 696
 697                 self.memory.write_int(dest, result, dest_size)?;
 698             }
 699
 700             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 701         }
 702
 703         // Since we pushed no stack frame, the main loop will act
 704         // as if the call just completed and it's returning to the
 705         // current frame.
 706         Ok(TerminatorTarget::Call)
 707     }
 708
 709     fn assign_fields<I: IntoIterator<Item = u64>>(
 710         &mut self,
 711         dest: Pointer,
 712         offsets: I,
 713         operands: &[mir::Operand<'tcx>],
 714     ) -> EvalResult<()> {
 715         for (offset, operand) in offsets.into_iter().zip(operands) {
 716             let src = self.eval_operand(operand)?;
 717             let src_ty = self.operand_ty(operand);
 718             let field_dest = dest.offset(offset as isize);
 719             self.move_(src, field_dest, src_ty)?;
 720         }
 721         Ok(())
 722     }
 723
 724     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 725         -> EvalResult<()>
 726     {
 727         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 728         let dest_ty = self.lvalue_ty(lvalue);
 729         let dest_layout = self.type_layout(dest_ty);
 730
 731         use rustc::mir::repr::Rvalue::*;
 732         match *rvalue {
 733             Use(ref operand) => {
 734                 let src = self.eval_operand(operand)?;
 735                 self.move_(src, dest, dest_ty)?;
 736             }
 737
 738             BinaryOp(bin_op, ref left, ref right) => {
 739                 let left_ptr = self.eval_operand(left)?;
 740                 let left_ty = self.operand_ty(left);
 741                 let left_val = self.read_primval(left_ptr, left_ty)?;
 742
 743                 let right_ptr = self.eval_operand(right)?;
 744                 let right_ty = self.operand_ty(right);
 745                 let right_val = self.read_primval(right_ptr, right_ty)?;
 746
 747                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 748                 self.memory.write_primval(dest, val)?;
 749             }
 750
 751             UnaryOp(un_op, ref operand) => {
 752                 let ptr = self.eval_operand(operand)?;
 753                 let ty = self.operand_ty(operand);
 754                 let val = self.read_primval(ptr, ty)?;
 755                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 756             }
 757
 758             Aggregate(ref kind, ref operands) => {
 759                 use rustc::ty::layout::Layout::*;
 760                 match *dest_layout {
 761                     Univariant { ref variant, .. } => {
 762                         let offsets = iter::once(0)
 763                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 764                         self.assign_fields(dest, offsets, operands)?;
 765                     }
 766
 767                     Array { .. } => {
 768                         let elem_size = match dest_ty.sty {
 769                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 770                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 771                                         kind, dest_ty),
 772                         };
 773                         let offsets = (0..).map(|i| i * elem_size);
 774                         self.assign_fields(dest, offsets, operands)?;
 775                     }
 776
 777                     General { discr, ref variants, .. } => {
 778                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 779                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 780                             let discr_size = discr.size().bytes() as usize;
 781                             self.memory.write_uint(dest, discr_val, discr_size)?;
 782
 783                             let offsets = variants[variant].offset_after_field.iter()
 784                                 .map(|s| s.bytes());
 785                             self.assign_fields(dest, offsets, operands)?;
 786                         } else {
 787                             panic!("tried to assign {:?} to Layout::General", kind);
 788                         }
 789                     }
 790
 791                     RawNullablePointer { nndiscr, .. } => {
 792                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 793                             if nndiscr == variant as u64 {
 794                                 assert_eq!(operands.len(), 1);
 795                                 let operand = &operands[0];
 796                                 let src = self.eval_operand(operand)?;
 797                                 let src_ty = self.operand_ty(operand);
 798                                 self.move_(src, dest, src_ty)?;
 799                             } else {
 800                                 assert_eq!(operands.len(), 0);
 801                                 self.memory.write_isize(dest, 0)?;
 802                             }
 803                         } else {
 804                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 805                         }
 806                     }
 807
 808                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
 809                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 810                             if nndiscr == variant as u64 {
 811                                 let offsets = iter::once(0)
 812                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
 813                                 try!(self.assign_fields(dest, offsets, operands));
 814                             } else {
 815                                 assert_eq!(operands.len(), 0);
 816                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
 817                                 let dest = dest.offset(offset.bytes() as isize);
 818                                 try!(self.memory.write_isize(dest, 0));
 819                             }
 820                         } else {
 821                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 822                         }
 823                     }
 824
 825                     CEnum { discr, signed, .. } => {
 826                         assert_eq!(operands.len(), 0);
 827                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 828                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 829                             let size = discr.size().bytes() as usize;
 830
 831                             if signed {
 832                                 self.memory.write_int(dest, val as i64, size)?;
 833                             } else {
 834                                 self.memory.write_uint(dest, val, size)?;
 835                             }
 836                         } else {
 837                             panic!("tried to assign {:?} to Layout::CEnum", kind);
 838                         }
 839                     }
 840
 841                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
 842                 }
 843             }
 844
 845             Repeat(ref operand, _) => {
 846                 let (elem_size, length) = match dest_ty.sty {
 847                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
 848                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
 849                 };
 850
 851                 let src = self.eval_operand(operand)?;
 852                 for i in 0..length {
 853                     let elem_dest = dest.offset((i * elem_size) as isize);
 854                     self.memory.copy(src, elem_dest, elem_size)?;
 855                 }
 856             }
 857
 858             Len(ref lvalue) => {
 859                 let src = self.eval_lvalue(lvalue)?;
 860                 let ty = self.lvalue_ty(lvalue);
 861                 let len = match ty.sty {
 862                     ty::TyArray(_, n) => n as u64,
 863                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 864                         n
 865                     } else {
 866                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 867                     },
 868                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 869                 };
 870                 self.memory.write_usize(dest, len)?;
 871             }
 872
 873             Ref(_, _, ref lvalue) => {
 874                 let lv = self.eval_lvalue(lvalue)?;
 875                 self.memory.write_ptr(dest, lv.ptr)?;
 876                 match lv.extra {
 877                     LvalueExtra::None => {},
 878                     LvalueExtra::Length(len) => {
 879                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 880                         self.memory.write_usize(len_ptr, len)?;
 881                     }
 882                     LvalueExtra::DowncastVariant(..) =>
 883                         panic!("attempted to take a reference to an enum downcast lvalue"),
 884                 }
 885             }
 886
 887             Box(ty) => {
 888                 let size = self.type_size(ty);
 889                 let ptr = self.memory.allocate(size);
 890                 self.memory.write_ptr(dest, ptr)?;
 891             }
 892
 893             Cast(kind, ref operand, dest_ty) => {
 894                 let src = self.eval_operand(operand)?;
 895                 let src_ty = self.operand_ty(operand);
 896
 897                 use rustc::mir::repr::CastKind::*;
 898                 match kind {
 899                     Unsize => {
 900                         self.move_(src, dest, src_ty)?;
 901                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 902                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 903
 904                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 905                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 906                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 907                                 self.memory.write_usize(len_ptr, length as u64)?;
 908                             }
 909
 910                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 911                         }
 912                     }
 913
 914                     Misc => {
 915                         // FIXME(solson): Wrong for almost everything.
 916                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
 917                         self.memory.copy(src, dest, size)?;
 918                     }
 919
 920                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 921                 }
 922             }
 923
 924             Slice { .. } => unimplemented!(),
 925             InlineAsm { .. } => unimplemented!(),
 926         }
 927
 928         Ok(())
 929     }
 930
 931     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
 932         // Skip the constant 0 at the start meant for LLVM GEP.
 933         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
 934
 935         // Handle the field index for the outer non-null variant.
 936         let inner_ty = match ty.sty {
 937             ty::TyEnum(adt_def, substs) => {
 938                 let variant = &adt_def.variants[nndiscr as usize];
 939                 let index = path.next().unwrap();
 940                 let field = &variant.fields[index];
 941                 field.ty(self.tcx, substs)
 942             }
 943             _ => panic!(
 944                 "non-enum for StructWrappedNullablePointer: {}",
 945                 ty,
 946             ),
 947         };
 948
 949         self.field_path_offset(inner_ty, path)
 950     }
 951
 952     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
 953         let mut offset = Size::from_bytes(0);
 954
 955         // Skip the initial 0 intended for LLVM GEP.
 956         for field_index in path {
 957             let field_offset = self.get_field_offset(ty, field_index)?;
 958             ty = self.get_field_ty(ty, field_index)?;
 959             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
 960         }
 961
 962         Ok(offset)
 963     }
 964
 965     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
 966         match ty.sty {
 967             ty::TyStruct(adt_def, substs) => {
 968                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
 969             }
 970
 971             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 972             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 973             ty::TyBox(ty) => {
 974                 assert_eq!(field_index, 0);
 975                 Ok(ty)
 976             }
 977             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
 978         }
 979     }
 980
 981     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
 982         let layout = self.type_layout(ty);
 983
 984         use rustc::ty::layout::Layout::*;
 985         match *layout {
 986             Univariant { .. } => {
 987                 assert_eq!(field_index, 0);
 988                 Ok(Size::from_bytes(0))
 989             }
 990             FatPointer { .. } => {
 991                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
 992                 Ok(Size::from_bytes(bytes as u64))
 993             }
 994             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
 995         }
 996     }
 997
 998     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
 999         use rustc::mir::repr::Operand::*;
1000         match *op {
1001             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
1002             Constant(mir::Constant { ref literal, .. }) => {
1003                 use rustc::mir::repr::Literal::*;
1004                 match *literal {
1005                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1006                     Item { .. } => unimplemented!(),
1007                     Promoted { index } => {
1008                         // TODO(solson): Mark constants and statics as read-only and cache their
1009                         // values.
1010                         let current_mir = self.mir();
1011                         let mir = &current_mir.promoted[index];
1012                         self.call_nested(mir).map(Option::unwrap)
1013                     }
1014                 }
1015             }
1016         }
1017     }
1018
1019     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1020         use rustc::mir::repr::Lvalue::*;
1021         let ptr = match *lvalue {
1022             ReturnPointer => self.frame().return_ptr
1023                 .expect("ReturnPointer used in a function with no return value"),
1024             Arg(i) => self.frame().locals[i as usize],
1025             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1026             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1027
1028             Static(def_id) => {
1029                 // TODO(solson): Mark constants and statics as read-only and cache their values.
1030                 let mir = self.load_mir(def_id);
1031                 self.call_nested(&mir)?.unwrap()
1032             }
1033
1034             Projection(ref proj) => {
1035                 let base = self.eval_lvalue(&proj.base)?;
1036                 let base_ty = self.lvalue_ty(&proj.base);
1037                 let base_layout = self.type_layout(base_ty);
1038
1039                 use rustc::mir::repr::ProjectionElem::*;
1040                 match proj.elem {
1041                     Field(field, _) => {
1042                         use rustc::ty::layout::Layout::*;
1043                         let variant = match *base_layout {
1044                             Univariant { ref variant, .. } => variant,
1045                             General { ref variants, .. } => {
1046                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1047                                     &variants[variant_idx]
1048                                 } else {
1049                                     panic!("field access on enum had no variant index");
1050                                 }
1051                             }
1052                             RawNullablePointer { .. } => {
1053                                 assert_eq!(field.index(), 0);
1054                                 return Ok(base);
1055                             }
1056                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1057                             _ => panic!("field access on non-product type: {:?}", base_layout),
1058                         };
1059
1060                         let offset = variant.field_offset(field.index()).bytes();
1061                         base.ptr.offset(offset as isize)
1062                     },
1063
1064                     Downcast(_, variant) => {
1065                         use rustc::ty::layout::Layout::*;
1066                         match *base_layout {
1067                             General { discr, .. } => {
1068                                 return Ok(Lvalue {
1069                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1070                                     extra: LvalueExtra::DowncastVariant(variant),
1071                                 });
1072                             }
1073                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1074                                 return Ok(base);
1075                             }
1076                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1077                         }
1078                     },
1079
1080                     Deref => {
1081                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1082                         let ptr = self.memory.read_ptr(base.ptr)?;
1083                         let extra = match pointee_ty.sty {
1084                             ty::TySlice(_) | ty::TyStr => {
1085                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1086                                 let len = self.memory.read_usize(len_ptr)?;
1087                                 LvalueExtra::Length(len)
1088                             }
1089                             ty::TyTrait(_) => unimplemented!(),
1090                             _ => LvalueExtra::None,
1091                         };
1092                         return Ok(Lvalue { ptr: ptr, extra: extra });
1093                     }
1094
1095                     Index(ref operand) => {
1096                         let elem_size = match base_ty.sty {
1097                             ty::TyArray(elem_ty, _) |
1098                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
1099                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1100                         };
1101                         let n_ptr = self.eval_operand(operand)?;
1102                         let n = self.memory.read_usize(n_ptr)?;
1103                         base.ptr.offset(n as isize * elem_size as isize)
1104                     }
1105
1106                     ConstantIndex { .. } => unimplemented!(),
1107                 }
1108             }
1109         };
1110
1111         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1112     }
1113
1114     // TODO(solson): Try making const_to_primval instead.
1115     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
1116         use rustc::middle::const_val::ConstVal::*;
1117         match *const_val {
1118             Float(_f) => unimplemented!(),
1119             Integral(int) => {
1120                 // TODO(solson): Check int constant type.
1121                 let ptr = self.memory.allocate(8);
1122                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
1123                 Ok(ptr)
1124             }
1125             Str(ref s) => {
1126                 let psize = self.memory.pointer_size;
1127                 let static_ptr = self.memory.allocate(s.len());
1128                 let ptr = self.memory.allocate(psize * 2);
1129                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
1130                 self.memory.write_ptr(ptr, static_ptr)?;
1131                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
1132                 Ok(ptr)
1133             }
1134             ByteStr(ref bs) => {
1135                 let psize = self.memory.pointer_size;
1136                 let static_ptr = self.memory.allocate(bs.len());
1137                 let ptr = self.memory.allocate(psize);
1138                 self.memory.write_bytes(static_ptr, bs)?;
1139                 self.memory.write_ptr(ptr, static_ptr)?;
1140                 Ok(ptr)
1141             }
1142             Bool(b) => {
1143                 let ptr = self.memory.allocate(1);
1144                 self.memory.write_bool(ptr, b)?;
1145                 Ok(ptr)
1146             }
1147             Char(_c)          => unimplemented!(),
1148             Struct(_node_id)  => unimplemented!(),
1149             Tuple(_node_id)   => unimplemented!(),
1150             Function(_def_id) => unimplemented!(),
1151             Array(_, _)       => unimplemented!(),
1152             Repeat(_, _)      => unimplemented!(),
1153             Dummy             => unimplemented!(),
1154         }
1155     }
1156
1157     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1158         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
1159     }
1160
1161     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1162         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
1163     }
1164
1165     fn monomorphize(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1166         let substituted = ty.subst(self.tcx, self.substs());
1167         self.tcx.normalize_associated_type(&substituted)
1168     }
1169
1170     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
1171         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
1172     }
1173
1174     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1175         let size = self.type_size(ty);
1176         self.memory.copy(src, dest, size)?;
1177         if self.type_needs_drop(ty) {
1178             self.memory.drop_fill(src, size)?;
1179         }
1180         Ok(())
1181     }
1182
1183     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
1184         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
1185     }
1186
1187     fn type_size(&self, ty: Ty<'tcx>) -> usize {
1188         self.type_layout(ty).size(&self.tcx.data_layout).bytes() as usize
1189     }
1190
1191     fn type_layout(&self, ty: Ty<'tcx>) -> &'tcx Layout {
1192         // TODO(solson): Is this inefficient? Needs investigation.
1193         let ty = self.monomorphize(ty);
1194
1195         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1196             // TODO(solson): Report this error properly.
1197             ty.layout(&infcx).unwrap()
1198         })
1199     }
1200
1201     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1202         use syntax::ast::{IntTy, UintTy};
1203         let val = match (self.memory.pointer_size, &ty.sty) {
1204             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1205             (_, &ty::TyInt(IntTy::I8))    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1206             (2, &ty::TyInt(IntTy::Is)) |
1207             (_, &ty::TyInt(IntTy::I16))   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1208             (4, &ty::TyInt(IntTy::Is)) |
1209             (_, &ty::TyInt(IntTy::I32))   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1210             (8, &ty::TyInt(IntTy::Is)) |
1211             (_, &ty::TyInt(IntTy::I64))   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1212             (_, &ty::TyUint(UintTy::U8))  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1213             (2, &ty::TyUint(UintTy::Us)) |
1214             (_, &ty::TyUint(UintTy::U16)) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1215             (4, &ty::TyUint(UintTy::Us)) |
1216             (_, &ty::TyUint(UintTy::U32)) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1217             (8, &ty::TyUint(UintTy::Us)) |
1218             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1219
1220             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
1221             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
1222                 if self.type_is_sized(ty) {
1223                     match self.memory.read_ptr(ptr) {
1224                         Ok(p) => PrimVal::AbstractPtr(p),
1225                         Err(EvalError::ReadBytesAsPointer) => {
1226                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1227                         }
1228                         Err(e) => return Err(e),
1229                     }
1230                 } else {
1231                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1232                 }
1233             }
1234
1235             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1236         };
1237         Ok(val)
1238     }
1239
1240     fn frame(&self) -> &Frame<'mir, 'tcx> {
1241         self.stack.last().expect("no call frames exist")
1242     }
1243
1244     fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1245         self.stack.last_mut().expect("no call frames exist")
1246     }
1247
1248     fn mir(&self) -> CachedMir<'mir, 'tcx> {
1249         self.frame().mir.clone()
1250     }
1251
1252     fn substs(&self) -> &'tcx Substs<'tcx> {
1253         self.substs_stack.last().cloned().unwrap_or_else(|| self.tcx.mk_substs(Substs::empty()))
1254     }
1255
1256     fn load_mir(&self, def_id: DefId) -> CachedMir<'mir, 'tcx> {
1257         match self.tcx.map.as_local_node_id(def_id) {
1258             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
1259             None => {
1260                 let mut mir_cache = self.mir_cache.borrow_mut();
1261                 if let Some(mir) = mir_cache.get(&def_id) {
1262                     return CachedMir::Owned(mir.clone());
1263                 }
1264
1265                 let cs = &self.tcx.sess.cstore;
1266                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1267                     panic!("no mir for {:?}", def_id);
1268                 });
1269                 let cached = Rc::new(mir);
1270                 mir_cache.insert(def_id, cached.clone());
1271                 CachedMir::Owned(cached)
1272             }
1273         }
1274     }
1275
1276     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1277         // Do the initial selection for the obligation. This yields the shallow result we are
1278         // looking for -- that is, what specific impl.
1279         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1280             let mut selcx = traits::SelectionContext::new(&infcx);
1281
1282             let obligation = traits::Obligation::new(
1283                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1284                 trait_ref.to_poly_trait_predicate(),
1285             );
1286             let selection = selcx.select(&obligation).unwrap().unwrap();
1287
1288             // Currently, we use a fulfillment context to completely resolve all nested obligations.
1289             // This is because they can inform the inference of the impl's type parameters.
1290             let mut fulfill_cx = traits::FulfillmentContext::new();
1291             let vtable = selection.map(|predicate| {
1292                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
1293             });
1294             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
1295         })
1296     }
1297
1298     /// Trait method, which has to be resolved to an impl method.
1299     pub fn trait_method(
1300         &self,
1301         def_id: DefId,
1302         substs: &'tcx Substs<'tcx>
1303     ) -> (DefId, &'tcx Substs<'tcx>) {
1304         let method_item = self.tcx.impl_or_trait_item(def_id);
1305         let trait_id = method_item.container().id();
1306         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1307         match self.fulfill_obligation(trait_ref) {
1308             traits::VtableImpl(vtable_impl) => {
1309                 let impl_did = vtable_impl.impl_def_id;
1310                 let mname = self.tcx.item_name(def_id);
1311                 // Create a concatenated set of substitutions which includes those from the impl
1312                 // and those from the method:
1313                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1314                 let substs = self.tcx.mk_substs(impl_substs);
1315                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1316
1317                 (mth.method.def_id, mth.substs)
1318             }
1319
1320             traits::VtableClosure(vtable_closure) =>
1321                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1322
1323             traits::VtableFnPointer(_fn_ty) => {
1324                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1325                 unimplemented!()
1326                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1327
1328                 // let method_ty = def_ty(tcx, def_id, substs);
1329                 // let fn_ptr_ty = match method_ty.sty {
1330                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1331                 //     _ => unreachable!("expected fn item type, found {}",
1332                 //                       method_ty)
1333                 // };
1334                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1335             }
1336
1337             traits::VtableObject(ref _data) => {
1338                 unimplemented!()
1339                 // Callee {
1340                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1341                 //                   tcx, data, def_id)),
1342                 //                   ty: def_ty(tcx, def_id, substs)
1343                 // }
1344             }
1345             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1346         }
1347     }
1348 }
1349
1350 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1351     match ptr_ty.sty {
1352         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1353         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1354         ty::TyBox(ty) => {
1355             Some(ty)
1356         }
1357         _ => None,
1358     }
1359 }
1360
1361 impl Lvalue {
1362     fn to_ptr(self) -> Pointer {
1363         assert_eq!(self.extra, LvalueExtra::None);
1364         self.ptr
1365     }
1366 }
1367
1368 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1369     type Target = mir::Mir<'tcx>;
1370     fn deref(&self) -> &mir::Mir<'tcx> {
1371         match *self {
1372             CachedMir::Ref(r) => r,
1373             CachedMir::Owned(ref rc) => rc,
1374         }
1375     }
1376 }
1377
1378 #[derive(Debug)]
1379 pub struct ImplMethod<'tcx> {
1380     pub method: Rc<ty::Method<'tcx>>,
1381     pub substs: &'tcx Substs<'tcx>,
1382     pub is_provided: bool,
1383 }
1384
1385 /// Locates the applicable definition of a method, given its name.
1386 pub fn get_impl_method<'a, 'tcx>(
1387     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1388     impl_def_id: DefId,
1389     substs: &'tcx Substs<'tcx>,
1390     name: ast::Name,
1391 ) -> ImplMethod<'tcx> {
1392     assert!(!substs.types.needs_infer());
1393
1394     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1395     let trait_def = tcx.lookup_trait_def(trait_def_id);
1396
1397     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1398         Some(node_item) => {
1399             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1400                 let substs = traits::translate_substs(&infcx, impl_def_id,
1401                                                       substs, node_item.node);
1402                 tcx.lift(&substs).unwrap_or_else(|| {
1403                     bug!("trans::meth::get_impl_method: translate_substs \
1404                           returned {:?} which contains inference types/regions",
1405                          substs);
1406                 })
1407             });
1408             ImplMethod {
1409                 method: node_item.item,
1410                 substs: substs,
1411                 is_provided: node_item.node.is_from_trait(),
1412             }
1413         }
1414         None => {
1415             bug!("method {:?} not found in {:?}", name, impl_def_id)
1416         }
1417     }
1418 }
1419
1420 pub fn interpret_start_points<'a, 'tcx>(
1421     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1422     mir_map: &MirMap<'tcx>,
1423 ) {
1424     for (&id, mir) in &mir_map.map {
1425         for attr in tcx.map.attrs(id) {
1426             use syntax::attr::AttrMetaMethods;
1427             if attr.check_name("miri_run") {
1428                 let item = tcx.map.expect_item(id);
1429
1430                 if TRACE_EXECUTION {
1431                     println!("Interpreting: {}", item.name);
1432                 }
1433
1434                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1435                 let mut fecx = FnEvalContext::new(&mut gecx);
1436                 match fecx.call_nested(mir) {
1437                     Ok(Some(return_ptr)) => if TRACE_EXECUTION {
1438                         fecx.memory.dump(return_ptr.alloc_id);
1439                     },
1440                     Ok(None) => println!("(diverging function returned)"),
1441                     Err(_e) => {
1442                         // TODO(solson): Detect whether the error was already reported or not.
1443                         // tcx.sess.err(&e.to_string());
1444                     }
1445                 }
1446
1447                 if TRACE_EXECUTION {
1448                     println!("");
1449                 }
1450             }
1451         }
1452     }
1453 }
1454
1455 // TODO(solson): Upstream these methods into rustc::ty::layout.
1456
1457 trait IntegerExt {
1458     fn size(self) -> Size;
1459 }
1460
1461 impl IntegerExt for layout::Integer {
1462     fn size(self) -> Size {
1463         use rustc::ty::layout::Integer::*;
1464         match self {
1465             I1 | I8 => Size::from_bits(8),
1466             I16 => Size::from_bits(16),
1467             I32 => Size::from_bits(32),
1468             I64 => Size::from_bits(64),
1469         }
1470     }
1471 }
1472
1473 trait StructExt {
1474     fn field_offset(&self, index: usize) -> Size;
1475 }
1476
1477 impl StructExt for layout::Struct {
1478     fn field_offset(&self, index: usize) -> Size {
1479         if index == 0 {
1480             Size::from_bytes(0)
1481         } else {
1482             self.offset_after_field[index - 1]
1483         }
1484     }
1485 }