2 use rustc::ty::{self, Ty};
3 use rustc::ty::layout::{self, Align, LayoutOf, TyLayout};
4 use rustc_data_structures::indexed_vec::Idx;
6 use rustc::mir::interpret::{GlobalId, Value, PrimVal, EvalResult, Pointer, MemoryPointer};
7 use super::{EvalContext, Machine, ValTy};
8 use interpret::memory::HasMemory;
10 #[derive(Copy, Clone, Debug)]
12 /// An place referring to a value allocated in the `Memory` system.
14 /// An place may have an invalid (integral or undef) pointer,
15 /// since it might be turned back into a reference
16 /// before ever being dereferenced.
22 /// An place referring to a value on the stack. Represented by a stack frame index paired with
23 /// a Mir local index.
24 Local { frame: usize, local: mir::Local },
27 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
31 Vtable(MemoryPointer),
32 DowncastVariant(usize),
36 /// Produces an Place that will error if attempted to be read from
37 pub fn undef() -> Self {
38 Self::from_primval_ptr(PrimVal::Undef.into(), Align::from_bytes(1, 1).unwrap())
41 pub fn from_primval_ptr(ptr: Pointer, align: Align) -> Self {
45 extra: PlaceExtra::None,
49 pub fn from_ptr(ptr: MemoryPointer, align: Align) -> Self {
50 Self::from_primval_ptr(ptr.into(), align)
53 pub fn to_ptr_align_extra(self) -> (Pointer, Align, PlaceExtra) {
55 Place::Ptr { ptr, align, extra } => (ptr, align, extra),
56 _ => bug!("to_ptr_and_extra: expected Place::Ptr, got {:?}", self),
61 pub fn to_ptr_align(self) -> (Pointer, Align) {
62 let (ptr, align, _extra) = self.to_ptr_align_extra();
66 pub fn to_ptr(self) -> EvalResult<'tcx, MemoryPointer> {
67 // At this point, we forget about the alignment information -- the place has been turned into a reference,
68 // and no matter where it came from, it now must be aligned.
69 self.to_ptr_align().0.to_ptr()
72 pub(super) fn elem_ty_and_len(self, ty: Ty<'tcx>) -> (Ty<'tcx>, u64) {
74 ty::TyArray(elem, n) => (elem, n.val.to_const_int().unwrap().to_u64().unwrap() as u64),
76 ty::TySlice(elem) => {
78 Place::Ptr { extra: PlaceExtra::Length(len), .. } => (elem, len),
81 "elem_ty_and_len of a TySlice given non-slice place: {:?}",
88 _ => bug!("elem_ty_and_len expected array or slice, got {:?}", ty),
93 impl<'a, 'tcx, M: Machine<'tcx>> EvalContext<'a, 'tcx, M> {
94 /// Reads a value from the place without going through the intermediate step of obtaining
96 pub fn try_read_place(
98 place: &mir::Place<'tcx>,
99 ) -> EvalResult<'tcx, Option<Value>> {
100 use rustc::mir::Place::*;
102 // Might allow this in the future, right now there's no way to do this from Rust code anyway
103 Local(mir::RETURN_PLACE) => err!(ReadFromReturnPointer),
104 // Directly reading a local will always succeed
105 Local(local) => self.frame().get_local(local).map(Some),
106 // Directly reading a static will always succeed
107 Static(ref static_) => {
108 let instance = ty::Instance::mono(self.tcx, static_.def_id);
109 Ok(Some(self.read_global_as_value(GlobalId {
112 }, self.layout_of(self.place_ty(place))?)))
114 Projection(ref proj) => self.try_read_place_projection(proj),
118 fn try_read_place_projection(
120 proj: &mir::PlaceProjection<'tcx>,
121 ) -> EvalResult<'tcx, Option<Value>> {
122 use rustc::mir::ProjectionElem::*;
123 let base = match self.try_read_place(&proj.base)? {
125 None => return Ok(None),
127 let base_ty = self.place_ty(&proj.base);
130 let base_layout = self.layout_of(base_ty)?;
131 let field_index = field.index();
132 let field = base_layout.field(&self, field_index)?;
133 let offset = base_layout.fields.offset(field_index);
135 // the field covers the entire type
136 Value::ByValPair(..) |
137 Value::ByVal(_) if offset.bytes() == 0 && field.size == base_layout.size => Ok(Some(base)),
138 // split fat pointers, 2 element tuples, ...
139 Value::ByValPair(a, b) if base_layout.fields.count() == 2 => {
140 let val = [a, b][field_index];
141 Ok(Some(Value::ByVal(val)))
146 // The NullablePointer cases should work fine, need to take care for normal enums
149 // reading index 0 or index 1 from a ByVal or ByVal pair could be optimized
150 ConstantIndex { .. } | Index(_) |
151 // No way to optimize this projection any better than the normal place path
156 /// Returns a value and (in case of a ByRef) if we are supposed to use aligned accesses.
157 pub(super) fn eval_and_read_place(
159 place: &mir::Place<'tcx>,
160 ) -> EvalResult<'tcx, Value> {
161 // Shortcut for things like accessing a fat pointer's field,
162 // which would otherwise (in the `eval_place` path) require moving a `ByValPair` to memory
163 // and returning an `Place::Ptr` to it
164 if let Some(val) = self.try_read_place(place)? {
167 let place = self.eval_place(place)?;
168 self.read_place(place)
171 pub fn read_place(&self, place: Place) -> EvalResult<'tcx, Value> {
173 Place::Ptr { ptr, align, extra } => {
174 assert_eq!(extra, PlaceExtra::None);
175 Ok(Value::ByRef(ptr, align))
177 Place::Local { frame, local } => self.stack[frame].get_local(local),
181 pub fn eval_place(&mut self, mir_place: &mir::Place<'tcx>) -> EvalResult<'tcx, Place> {
182 use rustc::mir::Place::*;
183 let place = match *mir_place {
184 Local(mir::RETURN_PLACE) => self.frame().return_place,
185 Local(local) => Place::Local {
186 frame: self.cur_frame(),
190 Static(ref static_) => {
191 let instance = ty::Instance::mono(self.tcx, static_.def_id);
196 let layout = self.layout_of(self.place_ty(mir_place))?;
197 let alloc = self.tcx.interpret_interner.borrow().get_cached(gid).expect("uncached global");
199 ptr: MemoryPointer::new(alloc, 0).into(),
201 extra: PlaceExtra::None,
205 Projection(ref proj) => {
206 let ty = self.place_ty(&proj.base);
207 let place = self.eval_place(&proj.base)?;
208 return self.eval_place_projection(place, ty, &proj.elem);
212 if log_enabled!(::log::LogLevel::Trace) {
213 self.dump_local(place);
223 mut base_layout: TyLayout<'tcx>,
224 ) -> EvalResult<'tcx, (Place, TyLayout<'tcx>)> {
226 Place::Ptr { extra: PlaceExtra::DowncastVariant(variant_index), .. } => {
227 base_layout = base_layout.for_variant(&self, variant_index);
231 let field_index = field.index();
232 let field = base_layout.field(&self, field_index)?;
233 let offset = base_layout.fields.offset(field_index);
235 // Do not allocate in trivial cases
236 let (base_ptr, base_align, base_extra) = match base {
237 Place::Ptr { ptr, align, extra } => (ptr, align, extra),
238 Place::Local { frame, local } => {
239 match (&self.stack[frame].get_local(local)?, &base_layout.abi) {
240 // in case the field covers the entire type, just return the value
241 (&Value::ByVal(_), &layout::Abi::Scalar(_)) |
242 (&Value::ByValPair(..), &layout::Abi::ScalarPair(..))
243 if offset.bytes() == 0 && field.size == base_layout.size =>
245 return Ok((base, field));
247 _ => self.force_allocation(base)?.to_ptr_align_extra(),
252 let offset = match base_extra {
253 PlaceExtra::Vtable(tab) => {
254 let (_, align) = self.size_and_align_of_dst(
256 base_ptr.to_value_with_vtable(tab),
258 offset.abi_align(align).bytes()
263 let ptr = base_ptr.offset(offset, &self)?;
264 let align = base_align.min(base_layout.align).min(field.align);
265 let extra = if !field.is_unsized() {
269 PlaceExtra::None => bug!("expected fat pointer"),
270 PlaceExtra::DowncastVariant(..) => {
271 bug!("Rust doesn't support unsized fields in enum variants")
273 PlaceExtra::Vtable(_) |
274 PlaceExtra::Length(_) => {}
279 Ok((Place::Ptr { ptr, align, extra }, field))
282 pub fn val_to_place(&self, val: Value, ty: Ty<'tcx>) -> EvalResult<'tcx, Place> {
283 let layout = self.layout_of(ty)?;
284 Ok(match self.tcx.struct_tail(ty).sty {
285 ty::TyDynamic(..) => {
286 let (ptr, vtable) = self.into_ptr_vtable_pair(val)?;
290 extra: PlaceExtra::Vtable(vtable),
293 ty::TyStr | ty::TySlice(_) => {
294 let (ptr, len) = self.into_slice(val)?;
298 extra: PlaceExtra::Length(len),
301 _ => Place::from_primval_ptr(self.into_ptr(val)?, layout.align),
310 ) -> EvalResult<'tcx, Place> {
311 // Taking the outer type here may seem odd; it's needed because for array types, the outer type gives away the length.
312 let base = self.force_allocation(base)?;
313 let (base_ptr, align) = base.to_ptr_align();
315 let (elem_ty, len) = base.elem_ty_and_len(outer_ty);
316 let elem_size = self.layout_of(elem_ty)?.size.bytes();
319 "Tried to access element {} of array/slice with length {}",
323 let ptr = base_ptr.offset(n * elem_size, &*self)?;
327 extra: PlaceExtra::None,
331 pub(super) fn place_downcast(
335 ) -> EvalResult<'tcx, Place> {
337 let base = self.force_allocation(base)?;
338 let (ptr, align) = base.to_ptr_align();
339 let extra = PlaceExtra::DowncastVariant(variant);
340 Ok(Place::Ptr { ptr, align, extra })
343 pub fn eval_place_projection(
347 proj_elem: &mir::ProjectionElem<'tcx, mir::Local, Ty<'tcx>>,
348 ) -> EvalResult<'tcx, Place> {
349 use rustc::mir::ProjectionElem::*;
352 let layout = self.layout_of(base_ty)?;
353 Ok(self.place_field(base, field, layout)?.0)
356 Downcast(_, variant) => {
357 self.place_downcast(base, variant)
361 let val = self.read_place(base)?;
363 let pointee_type = match base_ty.sty {
364 ty::TyRawPtr(ref tam) |
365 ty::TyRef(_, ref tam) => tam.ty,
366 ty::TyAdt(def, _) if def.is_box() => base_ty.boxed_ty(),
367 _ => bug!("can only deref pointer types"),
370 trace!("deref to {} on {:?}", pointee_type, val);
372 self.val_to_place(val, pointee_type)
376 let value = self.frame().get_local(local)?;
377 let ty = self.tcx.types.usize;
378 let n = self.value_to_primval(ValTy { value, ty })?.to_u64()?;
379 self.place_index(base, base_ty, n)
388 let base = self.force_allocation(base)?;
389 let (base_ptr, align) = base.to_ptr_align();
391 let (elem_ty, n) = base.elem_ty_and_len(base_ty);
392 let elem_size = self.layout_of(elem_ty)?.size.bytes();
393 assert!(n >= min_length as u64);
395 let index = if from_end {
396 n - u64::from(offset)
401 let ptr = base_ptr.offset(index * elem_size, &self)?;
402 Ok(Place::Ptr { ptr, align, extra: PlaceExtra::None })
405 Subslice { from, to } => {
407 let base = self.force_allocation(base)?;
408 let (base_ptr, align) = base.to_ptr_align();
410 let (elem_ty, n) = base.elem_ty_and_len(base_ty);
411 let elem_size = self.layout_of(elem_ty)?.size.bytes();
412 assert!(u64::from(from) <= n - u64::from(to));
413 let ptr = base_ptr.offset(u64::from(from) * elem_size, &self)?;
414 // sublicing arrays produces arrays
415 let extra = if self.type_is_sized(base_ty) {
418 PlaceExtra::Length(n - u64::from(to) - u64::from(from))
420 Ok(Place::Ptr { ptr, align, extra })
425 pub fn place_ty(&self, place: &mir::Place<'tcx>) -> Ty<'tcx> {
427 place.ty(self.mir(), self.tcx).to_ty(self.tcx),