src/interpreter/mod.rs

   1 use rustc::middle::const_val;
   2 use rustc::hir::def_id::DefId;
   3 use rustc::mir::mir_map::MirMap;
   4 use rustc::mir::repr as mir;
   5 use rustc::traits::{self, ProjectionMode};
   6 use rustc::ty::fold::TypeFoldable;
   7 use rustc::ty::layout::{self, Layout, Size};
   8 use rustc::ty::subst::{self, Subst, Substs};
   9 use rustc::ty::{self, Ty, TyCtxt};
  10 use rustc::util::nodemap::DefIdMap;
  11 use std::cell::RefCell;
  12 use std::ops::{Deref, 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 use std::collections::HashMap;
  24
  25 mod stepper;
  26
  27 struct GlobalEvalContext<'a, 'tcx: 'a> {
  28     /// The results of the type checker, from rustc.
  29     tcx: TyCtxt<'a, 'tcx, 'tcx>,
  30
  31     /// A mapping from NodeIds to Mir, from rustc. Only contains MIR for crate-local items.
  32     mir_map: &'a MirMap<'tcx>,
  33
  34     /// A local cache from DefIds to Mir for non-crate-local items.
  35     mir_cache: RefCell<DefIdMap<Rc<mir::Mir<'tcx>>>>,
  36
  37     /// The virtual memory system.
  38     memory: Memory,
  39
  40     /// Precomputed statics and constants
  41     statics: DefIdMap<Pointer>,
  42 }
  43
  44 struct FnEvalContext<'a, 'b: 'a + 'mir, 'mir, 'tcx: 'b> {
  45     gecx: &'a mut GlobalEvalContext<'b, 'tcx>,
  46
  47     /// The virtual call stack.
  48     stack: Vec<Frame<'mir, 'tcx>>,
  49 }
  50
  51 impl<'a, 'b, 'mir, 'tcx> Deref for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  52     type Target = GlobalEvalContext<'b, 'tcx>;
  53     fn deref(&self) -> &Self::Target {
  54         self.gecx
  55     }
  56 }
  57
  58 impl<'a, 'b, 'mir, 'tcx> DerefMut for FnEvalContext<'a, 'b, 'mir, 'tcx> {
  59     fn deref_mut(&mut self) -> &mut Self::Target {
  60         self.gecx
  61     }
  62 }
  63
  64 /// A stack frame.
  65 struct Frame<'a, 'tcx: 'a> {
  66     /// The def_id of the current function
  67     def_id: DefId,
  68
  69     /// The span of the call site
  70     span: codemap::Span,
  71
  72     /// type substitutions for the current function invocation
  73     substs: &'tcx Substs<'tcx>,
  74
  75     /// The MIR for the function called on this frame.
  76     mir: CachedMir<'a, 'tcx>,
  77
  78     /// The block that is currently executed (or will be executed after the above call stacks return)
  79     next_block: mir::BasicBlock,
  80
  81     /// A pointer for writing the return value of the current call if it's not a diverging call.
  82     return_ptr: Option<Pointer>,
  83
  84     /// The list of locals for the current function, stored in order as
  85     /// `[arguments..., variables..., temporaries...]`. The variables begin at `self.var_offset`
  86     /// and the temporaries at `self.temp_offset`.
  87     locals: Vec<Pointer>,
  88
  89     /// The offset of the first variable in `self.locals`.
  90     var_offset: usize,
  91
  92     /// The offset of the first temporary in `self.locals`.
  93     temp_offset: usize,
  94
  95     /// List of precomputed promoted constants
  96     promoted: HashMap<usize, Pointer>,
  97
  98     /// The index of the currently evaluated statment
  99     stmt: usize,
 100 }
 101
 102 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 103 struct Lvalue {
 104     ptr: Pointer,
 105     extra: LvalueExtra,
 106 }
 107
 108 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 109 enum LvalueExtra {
 110     None,
 111     Length(u64),
 112     // TODO(solson): Vtable(memory::AllocId),
 113     DowncastVariant(usize),
 114 }
 115
 116 #[derive(Clone)]
 117 enum CachedMir<'mir, 'tcx: 'mir> {
 118     Ref(&'mir mir::Mir<'tcx>),
 119     Owned(Rc<mir::Mir<'tcx>>)
 120 }
 121
 122 /// Represents the action to be taken in the main loop as a result of executing a terminator.
 123 enum TerminatorTarget {
 124     /// Make a local jump to the next block
 125     Block,
 126
 127     /// Start executing from the new current frame. (For function calls.)
 128     Call,
 129
 130     /// Stop executing the current frame and resume the previous frame.
 131     Return,
 132 }
 133
 134 #[derive(Clone, Debug, Eq, PartialEq, Hash)]
 135 enum ConstantId<'tcx> {
 136     Promoted { index: usize },
 137     Static { def_id: DefId, substs: &'tcx Substs<'tcx> },
 138 }
 139
 140
 141 impl<'a, 'tcx> GlobalEvalContext<'a, 'tcx> {
 142     fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir_map: &'a MirMap<'tcx>) -> Self {
 143         GlobalEvalContext {
 144             tcx: tcx,
 145             mir_map: mir_map,
 146             mir_cache: RefCell::new(DefIdMap()),
 147             memory: Memory::new(tcx.sess
 148                                    .target
 149                                    .uint_type
 150                                    .bit_width()
 151                                    .expect("Session::target::uint_type was usize")/8),
 152             statics: DefIdMap(),
 153         }
 154     }
 155
 156     fn call(&mut self, mir: &mir::Mir<'tcx>, def_id: DefId) -> EvalResult<Option<Pointer>> {
 157         let substs = self.tcx.mk_substs(subst::Substs::empty());
 158
 159         let mut nested_fecx = FnEvalContext::new(self);
 160
 161         nested_fecx.push_stack_frame(def_id, mir.span, CachedMir::Ref(mir), substs, None);
 162         let return_ptr = nested_fecx.alloc_ret_ptr(mir.return_ty);
 163         nested_fecx.frame_mut().return_ptr = return_ptr;
 164
 165         nested_fecx.run()?;
 166         Ok(return_ptr)
 167     }
 168 }
 169
 170 impl<'a, 'b, 'mir, 'tcx> FnEvalContext<'a, 'b, 'mir, 'tcx> {
 171     fn new(gecx: &'a mut GlobalEvalContext<'b, 'tcx>) -> Self {
 172         FnEvalContext {
 173             gecx: gecx,
 174             stack: Vec::new(),
 175         }
 176     }
 177
 178     fn alloc_ret_ptr(&mut self, ty: ty::FnOutput<'tcx>) -> Option<Pointer> {
 179         match ty {
 180             ty::FnConverging(ty) => {
 181                 let size = self.type_size(ty);
 182                 Some(self.memory.allocate(size))
 183             }
 184             ty::FnDiverging => None,
 185         }
 186     }
 187
 188     fn maybe_report<T>(&self, span: codemap::Span, r: EvalResult<T>) -> EvalResult<T> {
 189         if let Err(ref e) = r {
 190             let mut err = self.tcx.sess.struct_span_err(span, &e.to_string());
 191             for &Frame{ def_id, substs, span, .. } in self.stack.iter().rev() {
 192                 // FIXME(solson): Find a way to do this without this Display impl hack.
 193                 use rustc::util::ppaux;
 194                 use std::fmt;
 195                 struct Instance<'tcx>(DefId, &'tcx Substs<'tcx>);
 196                 impl<'tcx> fmt::Display for Instance<'tcx> {
 197                     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 198                         ppaux::parameterized(f, self.1, self.0, ppaux::Ns::Value, &[],
 199                             |tcx| tcx.lookup_item_type(self.0).generics)
 200                     }
 201                 }
 202                 err.span_note(span, &format!("inside call to {}", Instance(def_id, substs)));
 203             }
 204             err.emit();
 205         }
 206         r
 207     }
 208
 209     fn run(&mut self) -> EvalResult<()> {
 210         let mut stepper = stepper::Stepper::new(self);
 211         'outer: loop {
 212             use self::stepper::Event::*;
 213             trace!("// {:?}", stepper.block());
 214
 215             loop {
 216                 match stepper.step()? {
 217                     Constant => trace!("next statement requires the computation of a constant"),
 218                     Assignment => trace!("{:?}", stepper.stmt()),
 219                     Terminator => {
 220                         trace!("{:?}", stepper.term().kind);
 221                         continue 'outer;
 222                     },
 223                     Done => return Ok(()),
 224                 }
 225             }
 226         }
 227     }
 228
 229     fn push_stack_frame(&mut self, def_id: DefId, span: codemap::Span, mir: CachedMir<'mir, 'tcx>, substs: &'tcx Substs<'tcx>,
 230         return_ptr: Option<Pointer>)
 231     {
 232         let arg_tys = mir.arg_decls.iter().map(|a| a.ty);
 233         let var_tys = mir.var_decls.iter().map(|v| v.ty);
 234         let temp_tys = mir.temp_decls.iter().map(|t| t.ty);
 235
 236         let num_args = mir.arg_decls.len();
 237         let num_vars = mir.var_decls.len();
 238
 239         ::log_settings::settings().indentation += 1;
 240
 241         self.stack.push(Frame {
 242             mir: mir.clone(),
 243             next_block: mir::START_BLOCK,
 244             return_ptr: return_ptr,
 245             locals: Vec::new(),
 246             var_offset: num_args,
 247             temp_offset: num_args + num_vars,
 248             promoted: HashMap::new(),
 249             span: span,
 250             def_id: def_id,
 251             substs: substs,
 252             stmt: 0,
 253         });
 254
 255         let locals: Vec<Pointer> = arg_tys.chain(var_tys).chain(temp_tys).map(|ty| {
 256             let size = self.type_size(ty);
 257             self.memory.allocate(size)
 258         }).collect();
 259
 260         self.frame_mut().locals = locals;
 261     }
 262
 263     fn pop_stack_frame(&mut self) {
 264         ::log_settings::settings().indentation -= 1;
 265         let _frame = self.stack.pop().expect("tried to pop a stack frame, but there were none");
 266         // TODO(solson): Deallocate local variables.
 267     }
 268
 269     fn eval_terminator(&mut self, terminator: &mir::Terminator<'tcx>)
 270             -> EvalResult<TerminatorTarget> {
 271         use rustc::mir::repr::TerminatorKind::*;
 272         let target = match terminator.kind {
 273             Return => TerminatorTarget::Return,
 274
 275             Goto { target } => {
 276                 self.frame_mut().next_block = target;
 277                 TerminatorTarget::Block
 278             },
 279
 280             If { ref cond, targets: (then_target, else_target) } => {
 281                 let cond_ptr = self.eval_operand(cond)?;
 282                 let cond_val = self.memory.read_bool(cond_ptr)?;
 283                 self.frame_mut().next_block = if cond_val { then_target } else { else_target };
 284                 TerminatorTarget::Block
 285             }
 286
 287             SwitchInt { ref discr, ref values, ref targets, .. } => {
 288                 let discr_ptr = self.eval_lvalue(discr)?.to_ptr();
 289                 let discr_size = self
 290                     .type_layout(self.lvalue_ty(discr))
 291                     .size(&self.tcx.data_layout)
 292                     .bytes() as usize;
 293                 let discr_val = self.memory.read_uint(discr_ptr, discr_size)?;
 294
 295                 // Branch to the `otherwise` case by default, if no match is found.
 296                 let mut target_block = targets[targets.len() - 1];
 297
 298                 for (index, val_const) in values.iter().enumerate() {
 299                     let ptr = self.const_to_ptr(val_const)?;
 300                     let val = self.memory.read_uint(ptr, discr_size)?;
 301                     if discr_val == val {
 302                         target_block = targets[index];
 303                         break;
 304                     }
 305                 }
 306
 307                 self.frame_mut().next_block = target_block;
 308                 TerminatorTarget::Block
 309             }
 310
 311             Switch { ref discr, ref targets, adt_def } => {
 312                 let adt_ptr = self.eval_lvalue(discr)?.to_ptr();
 313                 let adt_ty = self.lvalue_ty(discr);
 314                 let discr_val = self.read_discriminant_value(adt_ptr, adt_ty)?;
 315                 let matching = adt_def.variants.iter()
 316                     .position(|v| discr_val == v.disr_val.to_u64_unchecked());
 317
 318                 match matching {
 319                     Some(i) => {
 320                         self.frame_mut().next_block = targets[i];
 321                         TerminatorTarget::Block
 322                     },
 323                     None => return Err(EvalError::InvalidDiscriminant),
 324                 }
 325             }
 326
 327             Call { ref func, ref args, ref destination, .. } => {
 328                 let mut return_ptr = None;
 329                 if let Some((ref lv, target)) = *destination {
 330                     self.frame_mut().next_block = target;
 331                     return_ptr = Some(self.eval_lvalue(lv)?.to_ptr());
 332                 }
 333
 334                 let func_ty = self.operand_ty(func);
 335                 match func_ty.sty {
 336                     ty::TyFnDef(def_id, substs, fn_ty) => {
 337                         use syntax::abi::Abi;
 338                         match fn_ty.abi {
 339                             Abi::RustIntrinsic => {
 340                                 let name = self.tcx.item_name(def_id).as_str();
 341                                 match fn_ty.sig.0.output {
 342                                     ty::FnConverging(ty) => {
 343                                         let size = self.type_size(ty);
 344                                         let ret = return_ptr.unwrap();
 345                                         self.call_intrinsic(&name, substs, args, ret, size)?
 346                                     }
 347                                     ty::FnDiverging => unimplemented!(),
 348                                 }
 349                             }
 350
 351                             Abi::C => {
 352                                 match fn_ty.sig.0.output {
 353                                     ty::FnConverging(ty) => {
 354                                         let size = self.type_size(ty);
 355                                         self.call_c_abi(def_id, args, return_ptr.unwrap(), size)?
 356                                     }
 357                                     ty::FnDiverging => unimplemented!(),
 358                                 }
 359                             }
 360
 361                             Abi::Rust | Abi::RustCall => {
 362                                 // TODO(solson): Adjust the first argument when calling a Fn or
 363                                 // FnMut closure via FnOnce::call_once.
 364
 365                                 // Only trait methods can have a Self parameter.
 366                                 let (resolved_def_id, resolved_substs) = if substs.self_ty().is_some() {
 367                                     self.trait_method(def_id, substs)
 368                                 } else {
 369                                     (def_id, substs)
 370                                 };
 371
 372                                 let mut arg_srcs = Vec::new();
 373                                 for arg in args {
 374                                     let src = self.eval_operand(arg)?;
 375                                     let src_ty = self.operand_ty(arg);
 376                                     arg_srcs.push((src, src_ty));
 377                                 }
 378
 379                                 if fn_ty.abi == Abi::RustCall && !args.is_empty() {
 380                                     arg_srcs.pop();
 381                                     let last_arg = args.last().unwrap();
 382                                     let last = self.eval_operand(last_arg)?;
 383                                     let last_ty = self.operand_ty(last_arg);
 384                                     let last_layout = self.type_layout(last_ty);
 385                                     match (&last_ty.sty, last_layout) {
 386                                         (&ty::TyTuple(fields),
 387                                          &Layout::Univariant { ref variant, .. }) => {
 388                                             let offsets = iter::once(0)
 389                                                 .chain(variant.offset_after_field.iter()
 390                                                     .map(|s| s.bytes()));
 391                                             for (offset, ty) in offsets.zip(fields) {
 392                                                 let src = last.offset(offset as isize);
 393                                                 arg_srcs.push((src, ty));
 394                                             }
 395                                         }
 396                                         ty => panic!("expected tuple as last argument in function with 'rust-call' ABI, got {:?}", ty),
 397                                     }
 398                                 }
 399
 400                                 let mir = self.load_mir(resolved_def_id);
 401                                 self.push_stack_frame(def_id, terminator.span, mir, resolved_substs, return_ptr);
 402
 403                                 for (i, (src, src_ty)) in arg_srcs.into_iter().enumerate() {
 404                                     let dest = self.frame().locals[i];
 405                                     self.move_(src, dest, src_ty)?;
 406                                 }
 407
 408                                 TerminatorTarget::Call
 409                             }
 410
 411                             abi => return Err(EvalError::Unimplemented(format!("can't handle function with {:?} ABI", abi))),
 412                         }
 413                     }
 414
 415                     _ => return Err(EvalError::Unimplemented(format!("can't handle callee of type {:?}", func_ty))),
 416                 }
 417             }
 418
 419             Drop { ref value, target, .. } => {
 420                 let ptr = self.eval_lvalue(value)?.to_ptr();
 421                 let ty = self.lvalue_ty(value);
 422                 self.drop(ptr, ty)?;
 423                 self.frame_mut().next_block = target;
 424                 TerminatorTarget::Block
 425             }
 426
 427             Resume => unimplemented!(),
 428         };
 429
 430         Ok(target)
 431     }
 432
 433     fn drop(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
 434         if !self.type_needs_drop(ty) {
 435             debug!("no need to drop {:?}", ty);
 436             return Ok(());
 437         }
 438         trace!("-need to drop {:?}", ty);
 439
 440         // TODO(solson): Call user-defined Drop::drop impls.
 441
 442         match ty.sty {
 443             ty::TyBox(contents_ty) => {
 444                 match self.memory.read_ptr(ptr) {
 445                     Ok(contents_ptr) => {
 446                         self.drop(contents_ptr, contents_ty)?;
 447                         trace!("-deallocating box");
 448                         self.memory.deallocate(contents_ptr)?;
 449                     }
 450                     Err(EvalError::ReadBytesAsPointer) => {
 451                         let size = self.memory.pointer_size;
 452                         let possible_drop_fill = self.memory.read_bytes(ptr, size)?;
 453                         if possible_drop_fill.iter().all(|&b| b == mem::POST_DROP_U8) {
 454                             return Ok(());
 455                         } else {
 456                             return Err(EvalError::ReadBytesAsPointer);
 457                         }
 458                     }
 459                     Err(e) => return Err(e),
 460                 }
 461             }
 462
 463             // TODO(solson): Implement drop for other relevant types (e.g. aggregates).
 464             _ => {}
 465         }
 466
 467         // Filling drop.
 468         // FIXME(solson): Trait objects (with no static size) probably get filled, too.
 469         let size = self.type_size(ty);
 470         self.memory.drop_fill(ptr, size)?;
 471
 472         Ok(())
 473     }
 474
 475     fn read_discriminant_value(&self, adt_ptr: Pointer, adt_ty: Ty<'tcx>) -> EvalResult<u64> {
 476         use rustc::ty::layout::Layout::*;
 477         let adt_layout = self.type_layout(adt_ty);
 478
 479         let discr_val = match *adt_layout {
 480             General { discr, .. } | CEnum { discr, .. } => {
 481                 let discr_size = discr.size().bytes();
 482                 self.memory.read_uint(adt_ptr, discr_size as usize)?
 483             }
 484
 485             RawNullablePointer { nndiscr, .. } => {
 486                 self.read_nonnull_discriminant_value(adt_ptr, nndiscr)?
 487             }
 488
 489             StructWrappedNullablePointer { nndiscr, ref discrfield, .. } => {
 490                 let offset = self.nonnull_offset(adt_ty, nndiscr, discrfield)?;
 491                 let nonnull = adt_ptr.offset(offset.bytes() as isize);
 492                 self.read_nonnull_discriminant_value(nonnull, nndiscr)?
 493             }
 494
 495             // The discriminant_value intrinsic returns 0 for non-sum types.
 496             Array { .. } | FatPointer { .. } | Scalar { .. } | Univariant { .. } |
 497             Vector { .. } => 0,
 498         };
 499
 500         Ok(discr_val)
 501     }
 502
 503     fn read_nonnull_discriminant_value(&self, ptr: Pointer, nndiscr: u64) -> EvalResult<u64> {
 504         let not_null = match self.memory.read_usize(ptr) {
 505             Ok(0) => false,
 506             Ok(_) | Err(EvalError::ReadPointerAsBytes) => true,
 507             Err(e) => return Err(e),
 508         };
 509         assert!(nndiscr == 0 || nndiscr == 1);
 510         Ok(if not_null { nndiscr } else { 1 - nndiscr })
 511     }
 512
 513     fn call_intrinsic(
 514         &mut self,
 515         name: &str,
 516         substs: &'tcx Substs<'tcx>,
 517         args: &[mir::Operand<'tcx>],
 518         dest: Pointer,
 519         dest_size: usize
 520     ) -> EvalResult<TerminatorTarget> {
 521         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 522             .map(|arg| self.eval_operand(arg))
 523             .collect();
 524         let args = args_res?;
 525
 526         match name {
 527             // FIXME(solson): Handle different integer types correctly.
 528             "add_with_overflow" => {
 529                 let ty = *substs.types.get(subst::FnSpace, 0);
 530                 let size = self.type_size(ty);
 531                 let left = self.memory.read_int(args[0], size)?;
 532                 let right = self.memory.read_int(args[1], size)?;
 533                 let (n, overflowed) = unsafe {
 534                     ::std::intrinsics::add_with_overflow::<i64>(left, right)
 535                 };
 536                 self.memory.write_int(dest, n, size)?;
 537                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 538             }
 539
 540             "assume" => {}
 541
 542             "copy_nonoverlapping" => {
 543                 let elem_ty = *substs.types.get(subst::FnSpace, 0);
 544                 let elem_size = self.type_size(elem_ty);
 545                 let src = self.memory.read_ptr(args[0])?;
 546                 let dest = self.memory.read_ptr(args[1])?;
 547                 let count = self.memory.read_isize(args[2])?;
 548                 self.memory.copy(src, dest, count as usize * elem_size)?;
 549             }
 550
 551             "discriminant_value" => {
 552                 let ty = *substs.types.get(subst::FnSpace, 0);
 553                 let adt_ptr = self.memory.read_ptr(args[0])?;
 554                 let discr_val = self.read_discriminant_value(adt_ptr, ty)?;
 555                 self.memory.write_uint(dest, discr_val, dest_size)?;
 556             }
 557
 558             "forget" => {
 559                 let arg_ty = *substs.types.get(subst::FnSpace, 0);
 560                 let arg_size = self.type_size(arg_ty);
 561                 self.memory.drop_fill(args[0], arg_size)?;
 562             }
 563
 564             "init" => self.memory.write_repeat(dest, 0, dest_size)?,
 565
 566             "min_align_of" => {
 567                 self.memory.write_int(dest, 1, dest_size)?;
 568             }
 569
 570             "move_val_init" => {
 571                 let ty = *substs.types.get(subst::FnSpace, 0);
 572                 let ptr = self.memory.read_ptr(args[0])?;
 573                 self.move_(args[1], ptr, ty)?;
 574             }
 575
 576             // FIXME(solson): Handle different integer types correctly.
 577             "mul_with_overflow" => {
 578                 let ty = *substs.types.get(subst::FnSpace, 0);
 579                 let size = self.type_size(ty);
 580                 let left = self.memory.read_int(args[0], size)?;
 581                 let right = self.memory.read_int(args[1], size)?;
 582                 let (n, overflowed) = unsafe {
 583                     ::std::intrinsics::mul_with_overflow::<i64>(left, right)
 584                 };
 585                 self.memory.write_int(dest, n, size)?;
 586                 self.memory.write_bool(dest.offset(size as isize), overflowed)?;
 587             }
 588
 589             "offset" => {
 590                 let pointee_ty = *substs.types.get(subst::FnSpace, 0);
 591                 let pointee_size = self.type_size(pointee_ty) as isize;
 592                 let ptr_arg = args[0];
 593                 let offset = self.memory.read_isize(args[1])?;
 594
 595                 match self.memory.read_ptr(ptr_arg) {
 596                     Ok(ptr) => {
 597                         let result_ptr = ptr.offset(offset as isize * pointee_size);
 598                         self.memory.write_ptr(dest, result_ptr)?;
 599                     }
 600                     Err(EvalError::ReadBytesAsPointer) => {
 601                         let addr = self.memory.read_isize(ptr_arg)?;
 602                         let result_addr = addr + offset * pointee_size as i64;
 603                         self.memory.write_isize(dest, result_addr)?;
 604                     }
 605                     Err(e) => return Err(e),
 606                 }
 607             }
 608
 609             // FIXME(solson): Handle different integer types correctly. Use primvals?
 610             "overflowing_sub" => {
 611                 let ty = *substs.types.get(subst::FnSpace, 0);
 612                 let size = self.type_size(ty);
 613                 let left = self.memory.read_int(args[0], size)?;
 614                 let right = self.memory.read_int(args[1], size)?;
 615                 let n = left.wrapping_sub(right);
 616                 self.memory.write_int(dest, n, size)?;
 617             }
 618
 619             "size_of" => {
 620                 let ty = *substs.types.get(subst::FnSpace, 0);
 621                 let size = self.type_size(ty) as u64;
 622                 self.memory.write_uint(dest, size, dest_size)?;
 623             }
 624
 625             "size_of_val" => {
 626                 let ty = *substs.types.get(subst::FnSpace, 0);
 627                 if self.type_is_sized(ty) {
 628                     let size = self.type_size(ty) as u64;
 629                     self.memory.write_uint(dest, size, dest_size)?;
 630                 } else {
 631                     match ty.sty {
 632                         ty::TySlice(_) | ty::TyStr => {
 633                             let elem_ty = ty.sequence_element_type(self.tcx);
 634                             let elem_size = self.type_size(elem_ty) as u64;
 635                             let ptr_size = self.memory.pointer_size as isize;
 636                             let n = self.memory.read_usize(args[0].offset(ptr_size))?;
 637                             self.memory.write_uint(dest, n * elem_size, dest_size)?;
 638                         }
 639
 640                         _ => return Err(EvalError::Unimplemented(format!("unimplemented: size_of_val::<{:?}>", ty))),
 641                     }
 642                 }
 643             }
 644
 645             "transmute" => {
 646                 let ty = *substs.types.get(subst::FnSpace, 0);
 647                 self.move_(args[0], dest, ty)?;
 648             }
 649             "uninit" => self.memory.mark_definedness(dest, dest_size, false)?,
 650
 651             name => return Err(EvalError::Unimplemented(format!("unimplemented intrinsic: {}", name))),
 652         }
 653
 654         // Since we pushed no stack frame, the main loop will act
 655         // as if the call just completed and it's returning to the
 656         // current frame.
 657         Ok(TerminatorTarget::Call)
 658     }
 659
 660     fn call_c_abi(
 661         &mut self,
 662         def_id: DefId,
 663         args: &[mir::Operand<'tcx>],
 664         dest: Pointer,
 665         dest_size: usize,
 666     ) -> EvalResult<TerminatorTarget> {
 667         let name = self.tcx.item_name(def_id);
 668         let attrs = self.tcx.get_attrs(def_id);
 669         let link_name = match attr::first_attr_value_str_by_name(&attrs, "link_name") {
 670             Some(ln) => ln.clone(),
 671             None => name.as_str(),
 672         };
 673
 674         let args_res: EvalResult<Vec<Pointer>> = args.iter()
 675             .map(|arg| self.eval_operand(arg))
 676             .collect();
 677         let args = args_res?;
 678
 679         match &link_name[..] {
 680             "__rust_allocate" => {
 681                 let size = self.memory.read_usize(args[0])?;
 682                 let ptr = self.memory.allocate(size as usize);
 683                 self.memory.write_ptr(dest, ptr)?;
 684             }
 685
 686             "__rust_reallocate" => {
 687                 let ptr = self.memory.read_ptr(args[0])?;
 688                 let size = self.memory.read_usize(args[2])?;
 689                 self.memory.reallocate(ptr, size as usize)?;
 690                 self.memory.write_ptr(dest, ptr)?;
 691             }
 692
 693             "memcmp" => {
 694                 let left = self.memory.read_ptr(args[0])?;
 695                 let right = self.memory.read_ptr(args[1])?;
 696                 let n = self.memory.read_usize(args[2])? as usize;
 697
 698                 let result = {
 699                     let left_bytes = self.memory.read_bytes(left, n)?;
 700                     let right_bytes = self.memory.read_bytes(right, n)?;
 701
 702                     use std::cmp::Ordering::*;
 703                     match left_bytes.cmp(right_bytes) {
 704                         Less => -1,
 705                         Equal => 0,
 706                         Greater => 1,
 707                     }
 708                 };
 709
 710                 self.memory.write_int(dest, result, dest_size)?;
 711             }
 712
 713             _ => return Err(EvalError::Unimplemented(format!("can't call C ABI function: {}", link_name))),
 714         }
 715
 716         // Since we pushed no stack frame, the main loop will act
 717         // as if the call just completed and it's returning to the
 718         // current frame.
 719         Ok(TerminatorTarget::Call)
 720     }
 721
 722     fn assign_fields<I: IntoIterator<Item = u64>>(
 723         &mut self,
 724         dest: Pointer,
 725         offsets: I,
 726         operands: &[mir::Operand<'tcx>],
 727     ) -> EvalResult<()> {
 728         for (offset, operand) in offsets.into_iter().zip(operands) {
 729             let src = self.eval_operand(operand)?;
 730             let src_ty = self.operand_ty(operand);
 731             let field_dest = dest.offset(offset as isize);
 732             self.move_(src, field_dest, src_ty)?;
 733         }
 734         Ok(())
 735     }
 736
 737     fn eval_assignment(&mut self, lvalue: &mir::Lvalue<'tcx>, rvalue: &mir::Rvalue<'tcx>)
 738         -> EvalResult<()>
 739     {
 740         let dest = self.eval_lvalue(lvalue)?.to_ptr();
 741         let dest_ty = self.lvalue_ty(lvalue);
 742         let dest_layout = self.type_layout(dest_ty);
 743
 744         use rustc::mir::repr::Rvalue::*;
 745         match *rvalue {
 746             Use(ref operand) => {
 747                 let src = self.eval_operand(operand)?;
 748                 self.move_(src, dest, dest_ty)?;
 749             }
 750
 751             BinaryOp(bin_op, ref left, ref right) => {
 752                 let left_ptr = self.eval_operand(left)?;
 753                 let left_ty = self.operand_ty(left);
 754                 let left_val = self.read_primval(left_ptr, left_ty)?;
 755
 756                 let right_ptr = self.eval_operand(right)?;
 757                 let right_ty = self.operand_ty(right);
 758                 let right_val = self.read_primval(right_ptr, right_ty)?;
 759
 760                 let val = primval::binary_op(bin_op, left_val, right_val)?;
 761                 self.memory.write_primval(dest, val)?;
 762             }
 763
 764             UnaryOp(un_op, ref operand) => {
 765                 let ptr = self.eval_operand(operand)?;
 766                 let ty = self.operand_ty(operand);
 767                 let val = self.read_primval(ptr, ty)?;
 768                 self.memory.write_primval(dest, primval::unary_op(un_op, val)?)?;
 769             }
 770
 771             Aggregate(ref kind, ref operands) => {
 772                 use rustc::ty::layout::Layout::*;
 773                 match *dest_layout {
 774                     Univariant { ref variant, .. } => {
 775                         let offsets = iter::once(0)
 776                             .chain(variant.offset_after_field.iter().map(|s| s.bytes()));
 777                         self.assign_fields(dest, offsets, operands)?;
 778                     }
 779
 780                     Array { .. } => {
 781                         let elem_size = match dest_ty.sty {
 782                             ty::TyArray(elem_ty, _) => self.type_size(elem_ty) as u64,
 783                             _ => panic!("tried to assign {:?} to non-array type {:?}",
 784                                         kind, dest_ty),
 785                         };
 786                         let offsets = (0..).map(|i| i * elem_size);
 787                         self.assign_fields(dest, offsets, operands)?;
 788                     }
 789
 790                     General { discr, ref variants, .. } => {
 791                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 792                             let discr_val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 793                             let discr_size = discr.size().bytes() as usize;
 794                             self.memory.write_uint(dest, discr_val, discr_size)?;
 795
 796                             let offsets = variants[variant].offset_after_field.iter()
 797                                 .map(|s| s.bytes());
 798                             self.assign_fields(dest, offsets, operands)?;
 799                         } else {
 800                             panic!("tried to assign {:?} to Layout::General", kind);
 801                         }
 802                     }
 803
 804                     RawNullablePointer { nndiscr, .. } => {
 805                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 806                             if nndiscr == variant as u64 {
 807                                 assert_eq!(operands.len(), 1);
 808                                 let operand = &operands[0];
 809                                 let src = self.eval_operand(operand)?;
 810                                 let src_ty = self.operand_ty(operand);
 811                                 self.move_(src, dest, src_ty)?;
 812                             } else {
 813                                 assert_eq!(operands.len(), 0);
 814                                 self.memory.write_isize(dest, 0)?;
 815                             }
 816                         } else {
 817                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 818                         }
 819                     }
 820
 821                     StructWrappedNullablePointer { nndiscr, ref nonnull, ref discrfield } => {
 822                         if let mir::AggregateKind::Adt(_, variant, _) = *kind {
 823                             if nndiscr == variant as u64 {
 824                                 let offsets = iter::once(0)
 825                                     .chain(nonnull.offset_after_field.iter().map(|s| s.bytes()));
 826                                 try!(self.assign_fields(dest, offsets, operands));
 827                             } else {
 828                                 assert_eq!(operands.len(), 0);
 829                                 let offset = self.nonnull_offset(dest_ty, nndiscr, discrfield)?;
 830                                 let dest = dest.offset(offset.bytes() as isize);
 831                                 try!(self.memory.write_isize(dest, 0));
 832                             }
 833                         } else {
 834                             panic!("tried to assign {:?} to Layout::RawNullablePointer", kind);
 835                         }
 836                     }
 837
 838                     CEnum { discr, signed, .. } => {
 839                         assert_eq!(operands.len(), 0);
 840                         if let mir::AggregateKind::Adt(adt_def, variant, _) = *kind {
 841                             let val = adt_def.variants[variant].disr_val.to_u64_unchecked();
 842                             let size = discr.size().bytes() as usize;
 843
 844                             if signed {
 845                                 self.memory.write_int(dest, val as i64, size)?;
 846                             } else {
 847                                 self.memory.write_uint(dest, val, size)?;
 848                             }
 849                         } else {
 850                             panic!("tried to assign {:?} to Layout::CEnum", kind);
 851                         }
 852                     }
 853
 854                     _ => return Err(EvalError::Unimplemented(format!("can't handle destination layout {:?} when assigning {:?}", dest_layout, kind))),
 855                 }
 856             }
 857
 858             Repeat(ref operand, _) => {
 859                 let (elem_size, length) = match dest_ty.sty {
 860                     ty::TyArray(elem_ty, n) => (self.type_size(elem_ty), n),
 861                     _ => panic!("tried to assign array-repeat to non-array type {:?}", dest_ty),
 862                 };
 863
 864                 let src = self.eval_operand(operand)?;
 865                 for i in 0..length {
 866                     let elem_dest = dest.offset((i * elem_size) as isize);
 867                     self.memory.copy(src, elem_dest, elem_size)?;
 868                 }
 869             }
 870
 871             Len(ref lvalue) => {
 872                 let src = self.eval_lvalue(lvalue)?;
 873                 let ty = self.lvalue_ty(lvalue);
 874                 let len = match ty.sty {
 875                     ty::TyArray(_, n) => n as u64,
 876                     ty::TySlice(_) => if let LvalueExtra::Length(n) = src.extra {
 877                         n
 878                     } else {
 879                         panic!("Rvalue::Len of a slice given non-slice pointer: {:?}", src);
 880                     },
 881                     _ => panic!("Rvalue::Len expected array or slice, got {:?}", ty),
 882                 };
 883                 self.memory.write_usize(dest, len)?;
 884             }
 885
 886             Ref(_, _, ref lvalue) => {
 887                 let lv = self.eval_lvalue(lvalue)?;
 888                 self.memory.write_ptr(dest, lv.ptr)?;
 889                 match lv.extra {
 890                     LvalueExtra::None => {},
 891                     LvalueExtra::Length(len) => {
 892                         let len_ptr = dest.offset(self.memory.pointer_size as isize);
 893                         self.memory.write_usize(len_ptr, len)?;
 894                     }
 895                     LvalueExtra::DowncastVariant(..) =>
 896                         panic!("attempted to take a reference to an enum downcast lvalue"),
 897                 }
 898             }
 899
 900             Box(ty) => {
 901                 let size = self.type_size(ty);
 902                 let ptr = self.memory.allocate(size);
 903                 self.memory.write_ptr(dest, ptr)?;
 904             }
 905
 906             Cast(kind, ref operand, dest_ty) => {
 907                 let src = self.eval_operand(operand)?;
 908                 let src_ty = self.operand_ty(operand);
 909
 910                 use rustc::mir::repr::CastKind::*;
 911                 match kind {
 912                     Unsize => {
 913                         self.move_(src, dest, src_ty)?;
 914                         let src_pointee_ty = pointee_type(src_ty).unwrap();
 915                         let dest_pointee_ty = pointee_type(dest_ty).unwrap();
 916
 917                         match (&src_pointee_ty.sty, &dest_pointee_ty.sty) {
 918                             (&ty::TyArray(_, length), &ty::TySlice(_)) => {
 919                                 let len_ptr = dest.offset(self.memory.pointer_size as isize);
 920                                 self.memory.write_usize(len_ptr, length as u64)?;
 921                             }
 922
 923                             _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 924                         }
 925                     }
 926
 927                     Misc => {
 928                         // FIXME(solson): Wrong for almost everything.
 929                         let size = dest_layout.size(&self.tcx.data_layout).bytes() as usize;
 930                         self.memory.copy(src, dest, size)?;
 931                     }
 932
 933                     _ => return Err(EvalError::Unimplemented(format!("can't handle cast: {:?}", rvalue))),
 934                 }
 935             }
 936
 937             Slice { .. } => unimplemented!(),
 938             InlineAsm { .. } => unimplemented!(),
 939         }
 940
 941         Ok(())
 942     }
 943
 944     fn nonnull_offset(&self, ty: Ty<'tcx>, nndiscr: u64, discrfield: &[u32]) -> EvalResult<Size> {
 945         // Skip the constant 0 at the start meant for LLVM GEP.
 946         let mut path = discrfield.iter().skip(1).map(|&i| i as usize);
 947
 948         // Handle the field index for the outer non-null variant.
 949         let inner_ty = match ty.sty {
 950             ty::TyEnum(adt_def, substs) => {
 951                 let variant = &adt_def.variants[nndiscr as usize];
 952                 let index = path.next().unwrap();
 953                 let field = &variant.fields[index];
 954                 field.ty(self.tcx, substs)
 955             }
 956             _ => panic!(
 957                 "non-enum for StructWrappedNullablePointer: {}",
 958                 ty,
 959             ),
 960         };
 961
 962         self.field_path_offset(inner_ty, path)
 963     }
 964
 965     fn field_path_offset<I: Iterator<Item = usize>>(&self, mut ty: Ty<'tcx>, path: I) -> EvalResult<Size> {
 966         let mut offset = Size::from_bytes(0);
 967
 968         // Skip the initial 0 intended for LLVM GEP.
 969         for field_index in path {
 970             let field_offset = self.get_field_offset(ty, field_index)?;
 971             ty = self.get_field_ty(ty, field_index)?;
 972             offset = offset.checked_add(field_offset, &self.tcx.data_layout).unwrap();
 973         }
 974
 975         Ok(offset)
 976     }
 977
 978     fn get_field_ty(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Ty<'tcx>> {
 979         match ty.sty {
 980             ty::TyStruct(adt_def, substs) => {
 981                 Ok(adt_def.struct_variant().fields[field_index].ty(self.tcx, substs))
 982             }
 983
 984             ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
 985             ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
 986             ty::TyBox(ty) => {
 987                 assert_eq!(field_index, 0);
 988                 Ok(ty)
 989             }
 990             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}", ty))),
 991         }
 992     }
 993
 994     fn get_field_offset(&self, ty: Ty<'tcx>, field_index: usize) -> EvalResult<Size> {
 995         let layout = self.type_layout(ty);
 996
 997         use rustc::ty::layout::Layout::*;
 998         match *layout {
 999             Univariant { .. } => {
1000                 assert_eq!(field_index, 0);
1001                 Ok(Size::from_bytes(0))
1002             }
1003             FatPointer { .. } => {
1004                 let bytes = layout::FAT_PTR_ADDR * self.memory.pointer_size;
1005                 Ok(Size::from_bytes(bytes as u64))
1006             }
1007             _ => Err(EvalError::Unimplemented(format!("can't handle type: {:?}, with layout: {:?}", ty, layout))),
1008         }
1009     }
1010
1011     fn eval_operand(&mut self, op: &mir::Operand<'tcx>) -> EvalResult<Pointer> {
1012         use rustc::mir::repr::Operand::*;
1013         match *op {
1014             Consume(ref lvalue) => Ok(self.eval_lvalue(lvalue)?.to_ptr()),
1015             Constant(mir::Constant { ref literal, .. }) => {
1016                 use rustc::mir::repr::Literal::*;
1017                 match *literal {
1018                     Value { ref value } => Ok(self.const_to_ptr(value)?),
1019                     Item { def_id, substs } => {
1020                         let item_ty = self.tcx.lookup_item_type(def_id).subst(self.tcx, substs);
1021                         if item_ty.ty.is_fn() {
1022                             Err(EvalError::Unimplemented("unimplemented: mentions of function items".to_string()))
1023                         } else {
1024                             Ok(*self.statics.get(&def_id).expect("static should have been cached (rvalue)"))
1025                         }
1026                     },
1027                     Promoted { index } => Ok(*self.frame().promoted.get(&index).expect("a promoted constant hasn't been precomputed")),
1028                 }
1029             }
1030         }
1031     }
1032
1033     fn eval_lvalue(&mut self, lvalue: &mir::Lvalue<'tcx>) -> EvalResult<Lvalue> {
1034         use rustc::mir::repr::Lvalue::*;
1035         let ptr = match *lvalue {
1036             ReturnPointer => self.frame().return_ptr
1037                 .expect("ReturnPointer used in a function with no return value"),
1038             Arg(i) => self.frame().locals[i as usize],
1039             Var(i) => self.frame().locals[self.frame().var_offset + i as usize],
1040             Temp(i) => self.frame().locals[self.frame().temp_offset + i as usize],
1041
1042             Static(def_id) => *self.gecx.statics.get(&def_id).expect("static should have been cached (lvalue)"),
1043
1044             Projection(ref proj) => {
1045                 let base = self.eval_lvalue(&proj.base)?;
1046                 let base_ty = self.lvalue_ty(&proj.base);
1047                 let base_layout = self.type_layout(base_ty);
1048
1049                 use rustc::mir::repr::ProjectionElem::*;
1050                 match proj.elem {
1051                     Field(field, _) => {
1052                         use rustc::ty::layout::Layout::*;
1053                         let variant = match *base_layout {
1054                             Univariant { ref variant, .. } => variant,
1055                             General { ref variants, .. } => {
1056                                 if let LvalueExtra::DowncastVariant(variant_idx) = base.extra {
1057                                     &variants[variant_idx]
1058                                 } else {
1059                                     panic!("field access on enum had no variant index");
1060                                 }
1061                             }
1062                             RawNullablePointer { .. } => {
1063                                 assert_eq!(field.index(), 0);
1064                                 return Ok(base);
1065                             }
1066                             StructWrappedNullablePointer { ref nonnull, .. } => nonnull,
1067                             _ => panic!("field access on non-product type: {:?}", base_layout),
1068                         };
1069
1070                         let offset = variant.field_offset(field.index()).bytes();
1071                         base.ptr.offset(offset as isize)
1072                     },
1073
1074                     Downcast(_, variant) => {
1075                         use rustc::ty::layout::Layout::*;
1076                         match *base_layout {
1077                             General { discr, .. } => {
1078                                 return Ok(Lvalue {
1079                                     ptr: base.ptr.offset(discr.size().bytes() as isize),
1080                                     extra: LvalueExtra::DowncastVariant(variant),
1081                                 });
1082                             }
1083                             RawNullablePointer { .. } | StructWrappedNullablePointer { .. } => {
1084                                 return Ok(base);
1085                             }
1086                             _ => panic!("variant downcast on non-aggregate: {:?}", base_layout),
1087                         }
1088                     },
1089
1090                     Deref => {
1091                         let pointee_ty = pointee_type(base_ty).expect("Deref of non-pointer");
1092                         let ptr = self.memory.read_ptr(base.ptr)?;
1093                         let extra = match pointee_ty.sty {
1094                             ty::TySlice(_) | ty::TyStr => {
1095                                 let len_ptr = base.ptr.offset(self.memory.pointer_size as isize);
1096                                 let len = self.memory.read_usize(len_ptr)?;
1097                                 LvalueExtra::Length(len)
1098                             }
1099                             ty::TyTrait(_) => unimplemented!(),
1100                             _ => LvalueExtra::None,
1101                         };
1102                         return Ok(Lvalue { ptr: ptr, extra: extra });
1103                     }
1104
1105                     Index(ref operand) => {
1106                         let elem_size = match base_ty.sty {
1107                             ty::TyArray(elem_ty, _) |
1108                             ty::TySlice(elem_ty) => self.type_size(elem_ty),
1109                             _ => panic!("indexing expected an array or slice, got {:?}", base_ty),
1110                         };
1111                         let n_ptr = self.eval_operand(operand)?;
1112                         let n = self.memory.read_usize(n_ptr)?;
1113                         base.ptr.offset(n as isize * elem_size as isize)
1114                     }
1115
1116                     ConstantIndex { .. } => unimplemented!(),
1117                 }
1118             }
1119         };
1120
1121         Ok(Lvalue { ptr: ptr, extra: LvalueExtra::None })
1122     }
1123
1124     // TODO(solson): Try making const_to_primval instead.
1125     fn const_to_ptr(&mut self, const_val: &const_val::ConstVal) -> EvalResult<Pointer> {
1126         use rustc::middle::const_val::ConstVal::*;
1127         match *const_val {
1128             Float(_f) => unimplemented!(),
1129             Integral(int) => {
1130                 // TODO(solson): Check int constant type.
1131                 let ptr = self.memory.allocate(8);
1132                 self.memory.write_uint(ptr, int.to_u64_unchecked(), 8)?;
1133                 Ok(ptr)
1134             }
1135             Str(ref s) => {
1136                 let psize = self.memory.pointer_size;
1137                 let static_ptr = self.memory.allocate(s.len());
1138                 let ptr = self.memory.allocate(psize * 2);
1139                 self.memory.write_bytes(static_ptr, s.as_bytes())?;
1140                 self.memory.write_ptr(ptr, static_ptr)?;
1141                 self.memory.write_usize(ptr.offset(psize as isize), s.len() as u64)?;
1142                 Ok(ptr)
1143             }
1144             ByteStr(ref bs) => {
1145                 let psize = self.memory.pointer_size;
1146                 let static_ptr = self.memory.allocate(bs.len());
1147                 let ptr = self.memory.allocate(psize);
1148                 self.memory.write_bytes(static_ptr, bs)?;
1149                 self.memory.write_ptr(ptr, static_ptr)?;
1150                 Ok(ptr)
1151             }
1152             Bool(b) => {
1153                 let ptr = self.memory.allocate(1);
1154                 self.memory.write_bool(ptr, b)?;
1155                 Ok(ptr)
1156             }
1157             Char(_c)          => unimplemented!(),
1158             Struct(_node_id)  => unimplemented!(),
1159             Tuple(_node_id)   => unimplemented!(),
1160             Function(_def_id) => unimplemented!(),
1161             Array(_, _)       => unimplemented!(),
1162             Repeat(_, _)      => unimplemented!(),
1163             Dummy             => unimplemented!(),
1164         }
1165     }
1166
1167     fn lvalue_ty(&self, lvalue: &mir::Lvalue<'tcx>) -> Ty<'tcx> {
1168         self.monomorphize(self.mir().lvalue_ty(self.tcx, lvalue).to_ty(self.tcx))
1169     }
1170
1171     fn operand_ty(&self, operand: &mir::Operand<'tcx>) -> Ty<'tcx> {
1172         self.monomorphize(self.mir().operand_ty(self.tcx, operand))
1173     }
1174
1175     fn monomorphize(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1176         let substituted = ty.subst(self.tcx, self.substs());
1177         self.tcx.normalize_associated_type(&substituted)
1178     }
1179
1180     fn type_needs_drop(&self, ty: Ty<'tcx>) -> bool {
1181         self.tcx.type_needs_drop_given_env(ty, &self.tcx.empty_parameter_environment())
1182     }
1183
1184     fn move_(&mut self, src: Pointer, dest: Pointer, ty: Ty<'tcx>) -> EvalResult<()> {
1185         let size = self.type_size(ty);
1186         self.memory.copy(src, dest, size)?;
1187         if self.type_needs_drop(ty) {
1188             self.memory.drop_fill(src, size)?;
1189         }
1190         Ok(())
1191     }
1192
1193     fn type_is_sized(&self, ty: Ty<'tcx>) -> bool {
1194         ty.is_sized(self.tcx, &self.tcx.empty_parameter_environment(), DUMMY_SP)
1195     }
1196
1197     fn type_size(&self, ty: Ty<'tcx>) -> usize {
1198         self.type_layout(ty).size(&self.tcx.data_layout).bytes() as usize
1199     }
1200
1201     fn type_layout(&self, ty: Ty<'tcx>) -> &'tcx Layout {
1202         // TODO(solson): Is this inefficient? Needs investigation.
1203         let ty = self.monomorphize(ty);
1204
1205         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1206             // TODO(solson): Report this error properly.
1207             ty.layout(&infcx).unwrap()
1208         })
1209     }
1210
1211     pub fn read_primval(&mut self, ptr: Pointer, ty: Ty<'tcx>) -> EvalResult<PrimVal> {
1212         use syntax::ast::{IntTy, UintTy};
1213         let val = match (self.memory.pointer_size, &ty.sty) {
1214             (_, &ty::TyBool)              => PrimVal::Bool(self.memory.read_bool(ptr)?),
1215             (_, &ty::TyInt(IntTy::I8))    => PrimVal::I8(self.memory.read_int(ptr, 1)? as i8),
1216             (2, &ty::TyInt(IntTy::Is)) |
1217             (_, &ty::TyInt(IntTy::I16))   => PrimVal::I16(self.memory.read_int(ptr, 2)? as i16),
1218             (4, &ty::TyInt(IntTy::Is)) |
1219             (_, &ty::TyInt(IntTy::I32))   => PrimVal::I32(self.memory.read_int(ptr, 4)? as i32),
1220             (8, &ty::TyInt(IntTy::Is)) |
1221             (_, &ty::TyInt(IntTy::I64))   => PrimVal::I64(self.memory.read_int(ptr, 8)? as i64),
1222             (_, &ty::TyUint(UintTy::U8))  => PrimVal::U8(self.memory.read_uint(ptr, 1)? as u8),
1223             (2, &ty::TyUint(UintTy::Us)) |
1224             (_, &ty::TyUint(UintTy::U16)) => PrimVal::U16(self.memory.read_uint(ptr, 2)? as u16),
1225             (4, &ty::TyUint(UintTy::Us)) |
1226             (_, &ty::TyUint(UintTy::U32)) => PrimVal::U32(self.memory.read_uint(ptr, 4)? as u32),
1227             (8, &ty::TyUint(UintTy::Us)) |
1228             (_, &ty::TyUint(UintTy::U64)) => PrimVal::U64(self.memory.read_uint(ptr, 8)? as u64),
1229
1230             (_, &ty::TyRef(_, ty::TypeAndMut { ty, .. })) |
1231             (_, &ty::TyRawPtr(ty::TypeAndMut { ty, .. })) => {
1232                 if self.type_is_sized(ty) {
1233                     match self.memory.read_ptr(ptr) {
1234                         Ok(p) => PrimVal::AbstractPtr(p),
1235                         Err(EvalError::ReadBytesAsPointer) => {
1236                             PrimVal::IntegerPtr(self.memory.read_usize(ptr)?)
1237                         }
1238                         Err(e) => return Err(e),
1239                     }
1240                 } else {
1241                     return Err(EvalError::Unimplemented(format!("unimplemented: primitive read of fat pointer type: {:?}", ty)));
1242                 }
1243             }
1244
1245             _ => panic!("primitive read of non-primitive type: {:?}", ty),
1246         };
1247         Ok(val)
1248     }
1249
1250     fn frame(&self) -> &Frame<'mir, 'tcx> {
1251         self.stack.last().expect("no call frames exist")
1252     }
1253
1254     fn basic_block(&self) -> &mir::BasicBlockData<'tcx> {
1255         let frame = self.frame();
1256         frame.mir.basic_block_data(frame.next_block)
1257     }
1258
1259     fn frame_mut(&mut self) -> &mut Frame<'mir, 'tcx> {
1260         self.stack.last_mut().expect("no call frames exist")
1261     }
1262
1263     fn mir(&self) -> CachedMir<'mir, 'tcx> {
1264         self.frame().mir.clone()
1265     }
1266
1267     fn substs(&self) -> &'tcx Substs<'tcx> {
1268         self.frame().substs
1269     }
1270
1271     fn load_mir(&self, def_id: DefId) -> CachedMir<'mir, 'tcx> {
1272         match self.tcx.map.as_local_node_id(def_id) {
1273             Some(node_id) => CachedMir::Ref(self.mir_map.map.get(&node_id).unwrap()),
1274             None => {
1275                 let mut mir_cache = self.mir_cache.borrow_mut();
1276                 if let Some(mir) = mir_cache.get(&def_id) {
1277                     return CachedMir::Owned(mir.clone());
1278                 }
1279
1280                 let cs = &self.tcx.sess.cstore;
1281                 let mir = cs.maybe_get_item_mir(self.tcx, def_id).unwrap_or_else(|| {
1282                     panic!("no mir for {:?}", def_id);
1283                 });
1284                 let cached = Rc::new(mir);
1285                 mir_cache.insert(def_id, cached.clone());
1286                 CachedMir::Owned(cached)
1287             }
1288         }
1289     }
1290
1291     fn fulfill_obligation(&self, trait_ref: ty::PolyTraitRef<'tcx>) -> traits::Vtable<'tcx, ()> {
1292         // Do the initial selection for the obligation. This yields the shallow result we are
1293         // looking for -- that is, what specific impl.
1294         self.tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1295             let mut selcx = traits::SelectionContext::new(&infcx);
1296
1297             let obligation = traits::Obligation::new(
1298                 traits::ObligationCause::misc(DUMMY_SP, ast::DUMMY_NODE_ID),
1299                 trait_ref.to_poly_trait_predicate(),
1300             );
1301             let selection = selcx.select(&obligation).unwrap().unwrap();
1302
1303             // Currently, we use a fulfillment context to completely resolve all nested obligations.
1304             // This is because they can inform the inference of the impl's type parameters.
1305             let mut fulfill_cx = traits::FulfillmentContext::new();
1306             let vtable = selection.map(|predicate| {
1307                 fulfill_cx.register_predicate_obligation(&infcx, predicate);
1308             });
1309             infcx.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &vtable)
1310         })
1311     }
1312
1313     /// Trait method, which has to be resolved to an impl method.
1314     pub fn trait_method(
1315         &self,
1316         def_id: DefId,
1317         substs: &'tcx Substs<'tcx>
1318     ) -> (DefId, &'tcx Substs<'tcx>) {
1319         let method_item = self.tcx.impl_or_trait_item(def_id);
1320         let trait_id = method_item.container().id();
1321         let trait_ref = ty::Binder(substs.to_trait_ref(self.tcx, trait_id));
1322         match self.fulfill_obligation(trait_ref) {
1323             traits::VtableImpl(vtable_impl) => {
1324                 let impl_did = vtable_impl.impl_def_id;
1325                 let mname = self.tcx.item_name(def_id);
1326                 // Create a concatenated set of substitutions which includes those from the impl
1327                 // and those from the method:
1328                 let impl_substs = vtable_impl.substs.with_method_from(substs);
1329                 let substs = self.tcx.mk_substs(impl_substs);
1330                 let mth = get_impl_method(self.tcx, impl_did, substs, mname);
1331
1332                 (mth.method.def_id, mth.substs)
1333             }
1334
1335             traits::VtableClosure(vtable_closure) =>
1336                 (vtable_closure.closure_def_id, vtable_closure.substs.func_substs),
1337
1338             traits::VtableFnPointer(_fn_ty) => {
1339                 let _trait_closure_kind = self.tcx.lang_items.fn_trait_kind(trait_id).unwrap();
1340                 unimplemented!()
1341                 // let llfn = trans_fn_pointer_shim(ccx, trait_closure_kind, fn_ty);
1342
1343                 // let method_ty = def_ty(tcx, def_id, substs);
1344                 // let fn_ptr_ty = match method_ty.sty {
1345                 //     ty::TyFnDef(_, _, fty) => tcx.mk_ty(ty::TyFnPtr(fty)),
1346                 //     _ => unreachable!("expected fn item type, found {}",
1347                 //                       method_ty)
1348                 // };
1349                 // Callee::ptr(immediate_rvalue(llfn, fn_ptr_ty))
1350             }
1351
1352             traits::VtableObject(ref _data) => {
1353                 unimplemented!()
1354                 // Callee {
1355                 //     data: Virtual(traits::get_vtable_index_of_object_method(
1356                 //                   tcx, data, def_id)),
1357                 //                   ty: def_ty(tcx, def_id, substs)
1358                 // }
1359             }
1360             vtable => unreachable!("resolved vtable bad vtable {:?} in trans", vtable),
1361         }
1362     }
1363 }
1364
1365 fn pointee_type(ptr_ty: ty::Ty) -> Option<ty::Ty> {
1366     match ptr_ty.sty {
1367         ty::TyRef(_, ty::TypeAndMut { ty, .. }) |
1368         ty::TyRawPtr(ty::TypeAndMut { ty, .. }) |
1369         ty::TyBox(ty) => {
1370             Some(ty)
1371         }
1372         _ => None,
1373     }
1374 }
1375
1376 impl Lvalue {
1377     fn to_ptr(self) -> Pointer {
1378         assert_eq!(self.extra, LvalueExtra::None);
1379         self.ptr
1380     }
1381 }
1382
1383 impl<'mir, 'tcx: 'mir> Deref for CachedMir<'mir, 'tcx> {
1384     type Target = mir::Mir<'tcx>;
1385     fn deref(&self) -> &mir::Mir<'tcx> {
1386         match *self {
1387             CachedMir::Ref(r) => r,
1388             CachedMir::Owned(ref rc) => rc,
1389         }
1390     }
1391 }
1392
1393 #[derive(Debug)]
1394 pub struct ImplMethod<'tcx> {
1395     pub method: Rc<ty::Method<'tcx>>,
1396     pub substs: &'tcx Substs<'tcx>,
1397     pub is_provided: bool,
1398 }
1399
1400 /// Locates the applicable definition of a method, given its name.
1401 pub fn get_impl_method<'a, 'tcx>(
1402     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1403     impl_def_id: DefId,
1404     substs: &'tcx Substs<'tcx>,
1405     name: ast::Name,
1406 ) -> ImplMethod<'tcx> {
1407     assert!(!substs.types.needs_infer());
1408
1409     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
1410     let trait_def = tcx.lookup_trait_def(trait_def_id);
1411
1412     match trait_def.ancestors(impl_def_id).fn_defs(tcx, name).next() {
1413         Some(node_item) => {
1414             let substs = tcx.normalizing_infer_ctxt(ProjectionMode::Any).enter(|infcx| {
1415                 let substs = traits::translate_substs(&infcx, impl_def_id,
1416                                                       substs, node_item.node);
1417                 tcx.lift(&substs).unwrap_or_else(|| {
1418                     bug!("trans::meth::get_impl_method: translate_substs \
1419                           returned {:?} which contains inference types/regions",
1420                          substs);
1421                 })
1422             });
1423             ImplMethod {
1424                 method: node_item.item,
1425                 substs: substs,
1426                 is_provided: node_item.node.is_from_trait(),
1427             }
1428         }
1429         None => {
1430             bug!("method {:?} not found in {:?}", name, impl_def_id)
1431         }
1432     }
1433 }
1434
1435 pub fn interpret_start_points<'a, 'tcx>(
1436     tcx: TyCtxt<'a, 'tcx, 'tcx>,
1437     mir_map: &MirMap<'tcx>,
1438 ) {
1439     let initial_indentation = ::log_settings::settings().indentation;
1440     for (&id, mir) in &mir_map.map {
1441         for attr in tcx.map.attrs(id) {
1442             use syntax::attr::AttrMetaMethods;
1443             if attr.check_name("miri_run") {
1444                 let item = tcx.map.expect_item(id);
1445
1446                 ::log_settings::settings().indentation = initial_indentation;
1447
1448                 debug!("Interpreting: {}", item.name);
1449
1450                 let mut gecx = GlobalEvalContext::new(tcx, mir_map);
1451                 match gecx.call(mir, tcx.map.local_def_id(id)) {
1452                     Ok(Some(return_ptr)) => if log_enabled!(::log::LogLevel::Debug) {
1453                         gecx.memory.dump(return_ptr.alloc_id);
1454                     },
1455                     Ok(None) => warn!("diverging function returned"),
1456                     Err(_e) => {
1457                         // TODO(solson): Detect whether the error was already reported or not.
1458                         // tcx.sess.err(&e.to_string());
1459                     }
1460                 }
1461             }
1462         }
1463     }
1464 }
1465
1466 // TODO(solson): Upstream these methods into rustc::ty::layout.
1467
1468 trait IntegerExt {
1469     fn size(self) -> Size;
1470 }
1471
1472 impl IntegerExt for layout::Integer {
1473     fn size(self) -> Size {
1474         use rustc::ty::layout::Integer::*;
1475         match self {
1476             I1 | I8 => Size::from_bits(8),
1477             I16 => Size::from_bits(16),
1478             I32 => Size::from_bits(32),
1479             I64 => Size::from_bits(64),
1480         }
1481     }
1482 }
1483
1484 trait StructExt {
1485     fn field_offset(&self, index: usize) -> Size;
1486 }
1487
1488 impl StructExt for layout::Struct {
1489     fn field_offset(&self, index: usize) -> Size {
1490         if index == 0 {
1491             Size::from_bytes(0)
1492         } else {
1493             self.offset_after_field[index - 1]
1494         }
1495     }
1496 }