add support for storing extra data in an allocation

Author: RalfJung

src/librustc/mir/interpret/mod.rs

@@ -524,7 +524,7 @@ impl<'tcx, M: fmt::Debug + Eq + Hash + Clone> AllocMap<'tcx, M> {
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
-pub struct Allocation<Tag=()> {
+pub struct Allocation<Tag=(),Extra=()> {
     /// The actual bytes of the allocation.
     /// Note that the bytes of a pointer represent the offset of the pointer
     pub bytes: Vec<u8>,
@@ -541,9 +541,11 @@ pub struct Allocation<Tag=()> {
     /// Also used by codegen to determine if a static should be put into mutable memory,
     /// which happens for `static mut` and `static` with interior mutability.
     pub mutability: Mutability,
+    /// Extra state for the machine.
+    pub extra: Extra,
 }
 
-impl<Tag> Allocation<Tag> {
+impl<Tag, Extra: Default> Allocation<Tag, Extra> {
     /// Creates a read-only allocation initialized by the given bytes
     pub fn from_bytes(slice: &[u8], align: Align) -> Self {
         let mut undef_mask = UndefMask::new(Size::ZERO);
@@ -554,6 +556,7 @@ impl<Tag> Allocation<Tag> {
             undef_mask,
             align,
             mutability: Mutability::Immutable,
+            extra: Extra::default(),
         }
     }
 
@@ -569,6 +572,7 @@ impl<Tag> Allocation<Tag> {
             undef_mask: UndefMask::new(size),
             align,
             mutability: Mutability::Mutable,
+            extra: Extra::default(),
         }
     }
 }

src/librustc_mir/const_eval.rs

@@ -53,7 +53,7 @@ pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
 ) -> EvalResult<'tcx, CompileTimeEvalContext<'a, 'mir, 'tcx>> {
     debug!("mk_borrowck_eval_cx: {:?}", instance);
     let param_env = tcx.param_env(instance.def_id());
-    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new(), ());
+    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new());
     // insert a stack frame so any queries have the correct substs
     // cannot use `push_stack_frame`; if we do `const_prop` explodes
     ecx.stack.push(interpret::Frame {
@@ -76,7 +76,7 @@ pub fn mk_eval_cx<'a, 'tcx>(
 ) -> EvalResult<'tcx, CompileTimeEvalContext<'a, 'tcx, 'tcx>> {
     debug!("mk_eval_cx: {:?}, {:?}", instance, param_env);
     let span = tcx.def_span(instance.def_id());
-    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new(), ());
+    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new());
     let mir = ecx.load_mir(instance.def)?;
     // insert a stack frame so any queries have the correct substs
     ecx.push_stack_frame(
@@ -155,7 +155,7 @@ fn eval_body_and_ecx<'a, 'mir, 'tcx>(
     // and try improving it down the road when more information is available
     let span = tcx.def_span(cid.instance.def_id());
     let span = mir.map(|mir| mir.span).unwrap_or(span);
-    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new(), ());
+    let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeInterpreter::new());
     let r = eval_body_using_ecx(&mut ecx, cid, mir, param_env);
     (r, ecx)
 }
@@ -336,11 +336,11 @@ type CompileTimeEvalContext<'a, 'mir, 'tcx> =
 impl<'a, 'mir, 'tcx> interpret::Machine<'a, 'mir, 'tcx>
     for CompileTimeInterpreter<'a, 'mir, 'tcx>
 {
-    type MemoryData = ();
     type MemoryKinds = !;
+    type AllocExtra = ();
     type PointerTag = ();
 
-    type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation<()>)>;
+    type MemoryMap = FxHashMap<AllocId, (MemoryKind<!>, Allocation)>;
 
     const STATIC_KIND: Option<!> = None; // no copying of statics allowed
 

src/librustc_mir/interpret/eval_context.rs

@@ -205,13 +205,12 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tc
         tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         machine: M,
-        memory_data: M::MemoryData,
     ) -> Self {
         EvalContext {
             machine,
             tcx,
             param_env,
-            memory: Memory::new(tcx, memory_data),
+            memory: Memory::new(tcx),
             stack: Vec::new(),
             vtables: FxHashMap::default(),
         }

src/librustc_mir/interpret/machine.rs

@@ -62,23 +62,25 @@ pub trait AllocMap<K: Hash + Eq, V> {
 /// Methods of this trait signifies a point where CTFE evaluation would fail
 /// and some use case dependent behaviour can instead be applied.
 pub trait Machine<'a, 'mir, 'tcx>: Sized {
-    /// Additional data that can be accessed via the Memory
-    type MemoryData;
-
     /// Additional memory kinds a machine wishes to distinguish from the builtin ones
-    type MemoryKinds: ::std::fmt::Debug + Copy + Eq;
+    type MemoryKinds: ::std::fmt::Debug + Copy + Eq + 'static;
+
+    /// Tag tracked alongside every pointer.  This is used to implement "Stacked Borrows"
+    /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
+    type PointerTag: ::std::fmt::Debug + Default + Copy + Eq + Hash + 'static;
+
+    /// Extra data stored in every allocation.
+    type AllocExtra: ::std::fmt::Debug + Default + Clone;
 
     /// Memory's allocation map
     type MemoryMap:
-        AllocMap<AllocId, (MemoryKind<Self::MemoryKinds>, Allocation<Self::PointerTag>)> +
+        AllocMap<
+            AllocId,
+            (MemoryKind<Self::MemoryKinds>, Allocation<Self::PointerTag, Self::AllocExtra>)
+        > +
         Default +
         Clone;
 
-    /// Tag tracked alongside every pointer.  This is inert for now, in preparation for
-    /// a future implementation of "Stacked Borrows"
-    /// <https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html>.
-    type PointerTag: ::std::fmt::Debug + Default + Copy + Eq + Hash + 'static;
-
     /// The memory kind to use for copied statics -- or None if those are not supported.
     /// Statics are copied under two circumstances: When they are mutated, and when
     /// `static_with_default_tag` or `find_foreign_static` (see below) returns an owned allocation
@@ -127,7 +129,7 @@ pub trait Machine<'a, 'mir, 'tcx>: Sized {
     fn find_foreign_static(
         tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
         def_id: DefId,
-    ) -> EvalResult<'tcx, Cow<'tcx, Allocation<Self::PointerTag>>>;
+    ) -> EvalResult<'tcx, Cow<'tcx, Allocation<Self::PointerTag, Self::AllocExtra>>>;
 
     /// Called to turn an allocation obtained from the `tcx` into one that has
     /// the appropriate tags on each pointer.
@@ -138,7 +140,7 @@ pub trait Machine<'a, 'mir, 'tcx>: Sized {
     /// owned allocation to the map even when the map is shared.)
     fn static_with_default_tag(
         alloc: &'_ Allocation
-    ) -> Cow<'_, Allocation<Self::PointerTag>>;
+    ) -> Cow<'_, Allocation<Self::PointerTag, Self::AllocExtra>>;
 
     /// Called for all binary operations on integer(-like) types when one operand is a pointer
     /// value, and for the `Offset` operation that is inherently about pointers.

src/librustc_mir/interpret/memory.rs

@@ -47,9 +47,6 @@ pub enum MemoryKind<T> {
 // `Memory` has to depend on the `Machine` because some of its operations
 // (e.g. `get`) call a `Machine` hook.
 pub struct Memory<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'a, 'mir, 'tcx>> {
-    /// Additional data required by the Machine
-    pub data: M::MemoryData,
-
     /// Allocations local to this instance of the miri engine.  The kind
     /// helps ensure that the same mechanism is used for allocation and
     /// deallocation.  When an allocation is not found here, it is a
@@ -91,11 +88,9 @@ impl<'a, 'b, 'c, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> HasDataLayout
 // carefully copy only the reachable parts.
 impl<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'a, 'mir, 'tcx>>
     Clone for Memory<'a, 'mir, 'tcx, M>
-    where M::MemoryData: Clone
 {
     fn clone(&self) -> Self {
         Memory {
-            data: self.data.clone(),
             alloc_map: self.alloc_map.clone(),
             dead_alloc_map: self.dead_alloc_map.clone(),
             tcx: self.tcx,
@@ -104,9 +99,8 @@ impl<'a, 'mir, 'tcx: 'a + 'mir, M: Machine<'a, 'mir, 'tcx>>
 }
 
 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
-    pub fn new(tcx: TyCtxtAt<'a, 'tcx, 'tcx>, data: M::MemoryData) -> Self {
+    pub fn new(tcx: TyCtxtAt<'a, 'tcx, 'tcx>) -> Self {
         Memory {
-            data,
             alloc_map: Default::default(),
             dead_alloc_map: FxHashMap::default(),
             tcx,
@@ -123,7 +117,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
 
     pub fn allocate_with(
         &mut self,
-        alloc: Allocation<M::PointerTag>,
+        alloc: Allocation<M::PointerTag, M::AllocExtra>,
         kind: MemoryKind<M::MemoryKinds>,
     ) -> EvalResult<'tcx, AllocId> {
         let id = self.tcx.alloc_map.lock().reserve();
@@ -334,7 +328,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
     fn get_static_alloc(
         tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
         id: AllocId,
-    ) -> EvalResult<'tcx, Cow<'tcx, Allocation<M::PointerTag>>> {
+    ) -> EvalResult<'tcx, Cow<'tcx, Allocation<M::PointerTag, M::AllocExtra>>> {
         let alloc = tcx.alloc_map.lock().get(id);
         let def_id = match alloc {
             Some(AllocType::Memory(mem)) => {
@@ -376,7 +370,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         })
     }
 
-    pub fn get(&self, id: AllocId) -> EvalResult<'tcx, &Allocation<M::PointerTag>> {
+    pub fn get(&self, id: AllocId) -> EvalResult<'tcx, &Allocation<M::PointerTag, M::AllocExtra>> {
         // The error type of the inner closure here is somewhat funny.  We have two
         // ways of "erroring": An actual error, or because we got a reference from
         // `get_static_alloc` that we can actually use directly without inserting anything anywhere.
@@ -409,7 +403,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
     pub fn get_mut(
         &mut self,
         id: AllocId,
-    ) -> EvalResult<'tcx, &mut Allocation<M::PointerTag>> {
+    ) -> EvalResult<'tcx, &mut Allocation<M::PointerTag, M::AllocExtra>> {
         let tcx = self.tcx;
         let a = self.alloc_map.get_mut_or(id, || {
             // Need to make a copy, even if `get_static_alloc` is able
@@ -482,12 +476,12 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         self.dump_allocs(vec![id]);
     }
 
-    fn dump_alloc_helper<Tag>(
+    fn dump_alloc_helper<Tag, Extra>(
         &self,
         allocs_seen: &mut FxHashSet<AllocId>,
         allocs_to_print: &mut VecDeque<AllocId>,
         mut msg: String,
-        alloc: &Allocation<Tag>,
+        alloc: &Allocation<Tag, Extra>,
         extra: String,
     ) {
         use std::fmt::Write;
@@ -687,8 +681,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
 /// Interning (for CTFE)
 impl<'a, 'mir, 'tcx, M> Memory<'a, 'mir, 'tcx, M>
 where
-    M: Machine<'a, 'mir, 'tcx, PointerTag=()>,
-    M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<()>)>,
+    M: Machine<'a, 'mir, 'tcx, PointerTag=(), AllocExtra=()>,
+    M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation)>,
 {
     /// mark an allocation as static and initialized, either mutable or not
     pub fn intern_static(

src/librustc_mir/interpret/place.rs

@@ -267,7 +267,7 @@ impl<'a, 'mir, 'tcx, Tag, M> EvalContext<'a, 'mir, 'tcx, M>
 where
     Tag: ::std::fmt::Debug+Default+Copy+Eq+Hash+'static,
     M: Machine<'a, 'mir, 'tcx, PointerTag=Tag>,
-    M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag>)>,
+    M::MemoryMap: AllocMap<AllocId, (MemoryKind<M::MemoryKinds>, Allocation<Tag, M::AllocExtra>)>,
 {
     /// Take a value, which represents a (thin or fat) reference, and make it a place.
     /// Alignment is just based on the type.  This is the inverse of `MemPlace::to_ref`.

src/librustc_mir/interpret/snapshot.rs

@@ -305,7 +305,7 @@ impl<'a, Ctx> Snapshot<'a, Ctx> for &'a Allocation
     type Item = AllocationSnapshot<'a>;
 
     fn snapshot(&self, ctx: &'a Ctx) -> Self::Item {
-        let Allocation { bytes, relocations, undef_mask, align, mutability } = self;
+        let Allocation { bytes, relocations, undef_mask, align, mutability, extra: () } = self;
 
         AllocationSnapshot {
             bytes,