Auto merge of rust-lang#49833 - oli-obk:incremental_miri_regression, r=michaelwoerister

Don't recurse into allocations, use a global table instead

r? @michaelwoerister

fixes rust-lang#49663

Author: bors

src/librustc/ich/impls_ty.rs

@@ -398,12 +398,12 @@ impl_stable_hash_for!(struct mir::interpret::MemoryPointer {
 
 enum AllocDiscriminant {
     Alloc,
-    ExternStatic,
+    Static,
     Function,
 }
 impl_stable_hash_for!(enum self::AllocDiscriminant {
     Alloc,
-    ExternStatic,
+    Static,
     Function
 });
 
@@ -414,24 +414,25 @@ impl<'a> HashStable<StableHashingContext<'a>> for mir::interpret::AllocId {
         hasher: &mut StableHasher<W>,
     ) {
         ty::tls::with_opt(|tcx| {
+            trace!("hashing {:?}", *self);
             let tcx = tcx.expect("can't hash AllocIds during hir lowering");
-            if let Some(alloc) = tcx.interpret_interner.get_alloc(*self) {
+            if let Some(def_id) = tcx.interpret_interner.get_static(*self) {
+                AllocDiscriminant::Static.hash_stable(hcx, hasher);
+                trace!("hashing {:?} as static {:?}", *self, def_id);
+                def_id.hash_stable(hcx, hasher);
+            } else if let Some(alloc) = tcx.interpret_interner.get_alloc(*self) {
                 AllocDiscriminant::Alloc.hash_stable(hcx, hasher);
                 if hcx.alloc_id_recursion_tracker.insert(*self) {
-                    tcx
-                        .interpret_interner
-                        .get_corresponding_static_def_id(*self)
-                        .hash_stable(hcx, hasher);
+                    trace!("hashing {:?} as alloc {:#?}", *self, alloc);
                     alloc.hash_stable(hcx, hasher);
                     assert!(hcx.alloc_id_recursion_tracker.remove(self));
+                } else {
+                    trace!("skipping hashing of {:?} due to recursion", *self);
                 }
             } else if let Some(inst) = tcx.interpret_interner.get_fn(*self) {
+                trace!("hashing {:?} as fn {:#?}", *self, inst);
                 AllocDiscriminant::Function.hash_stable(hcx, hasher);
                 inst.hash_stable(hcx, hasher);
-            } else if let Some(def_id) = tcx.interpret_interner
-                                            .get_corresponding_static_def_id(*self) {
-                AllocDiscriminant::ExternStatic.hash_stable(hcx, hasher);
-                def_id.hash_stable(hcx, hasher);
             } else {
                 bug!("no allocation for {}", self);
             }

src/librustc/mir/interpret/mod.rs

@@ -154,10 +154,12 @@ pub struct AllocId(pub u64);
 impl ::rustc_serialize::UseSpecializedEncodable for AllocId {}
 impl ::rustc_serialize::UseSpecializedDecodable for AllocId {}
 
-pub const ALLOC_DISCRIMINANT: usize = 0;
-pub const FN_DISCRIMINANT: usize = 1;
-pub const EXTERN_STATIC_DISCRIMINANT: usize = 2;
-pub const SHORTHAND_START: usize = 3;
+#[derive(RustcDecodable, RustcEncodable)]
+enum AllocKind {
+    Alloc,
+    Fn,
+    Static,
+}
 
 pub fn specialized_encode_alloc_id<
     'a, 'tcx,
@@ -166,26 +168,18 @@ pub fn specialized_encode_alloc_id<
     encoder: &mut E,
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     alloc_id: AllocId,
-    shorthand: Option<usize>,
 ) -> Result<(), E::Error> {
-    if let Some(shorthand) = shorthand {
-        return shorthand.encode(encoder);
-    }
     if let Some(alloc) = tcx.interpret_interner.get_alloc(alloc_id) {
         trace!("encoding {:?} with {:#?}", alloc_id, alloc);
-        ALLOC_DISCRIMINANT.encode(encoder)?;
+        AllocKind::Alloc.encode(encoder)?;
         alloc.encode(encoder)?;
-        // encode whether this allocation is the root allocation of a static
-        tcx.interpret_interner
-            .get_corresponding_static_def_id(alloc_id)
-            .encode(encoder)?;
     } else if let Some(fn_instance) = tcx.interpret_interner.get_fn(alloc_id) {
         trace!("encoding {:?} with {:#?}", alloc_id, fn_instance);
-        FN_DISCRIMINANT.encode(encoder)?;
+        AllocKind::Fn.encode(encoder)?;
         fn_instance.encode(encoder)?;
-    } else if let Some(did) = tcx.interpret_interner.get_corresponding_static_def_id(alloc_id) {
-        // extern "C" statics don't have allocations, just encode its def_id
-        EXTERN_STATIC_DISCRIMINANT.encode(encoder)?;
+    } else if let Some(did) = tcx.interpret_interner.get_static(alloc_id) {
+        // referring to statics doesn't need to know about their allocations, just about its DefId
+        AllocKind::Static.encode(encoder)?;
         did.encode(encoder)?;
     } else {
         bug!("alloc id without corresponding allocation: {}", alloc_id);
@@ -196,53 +190,42 @@ pub fn specialized_encode_alloc_id<
 pub fn specialized_decode_alloc_id<
     'a, 'tcx,
     D: Decoder,
-    CACHE: FnOnce(&mut D, usize, AllocId),
-    SHORT: FnOnce(&mut D, usize) -> Result<AllocId, D::Error>
+    CACHE: FnOnce(&mut D, AllocId),
 >(
     decoder: &mut D,
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    pos: usize,
     cache: CACHE,
-    short: SHORT,
 ) -> Result<AllocId, D::Error> {
-    match usize::decode(decoder)? {
-        ALLOC_DISCRIMINANT => {
+    match AllocKind::decode(decoder)? {
+        AllocKind::Alloc => {
             let alloc_id = tcx.interpret_interner.reserve();
-            trace!("creating alloc id {:?} at {}", alloc_id, pos);
+            trace!("creating alloc id {:?}", alloc_id);
             // insert early to allow recursive allocs
-            cache(decoder, pos, alloc_id);
+            cache(decoder, alloc_id);
 
             let allocation = Allocation::decode(decoder)?;
             trace!("decoded alloc {:?} {:#?}", alloc_id, allocation);
             let allocation = tcx.intern_const_alloc(allocation);
             tcx.interpret_interner.intern_at_reserved(alloc_id, allocation);
 
-            if let Some(glob) = Option::<DefId>::decode(decoder)? {
-                tcx.interpret_interner.cache(glob, alloc_id);
-            }
-
             Ok(alloc_id)
         },
-        FN_DISCRIMINANT => {
-            trace!("creating fn alloc id at {}", pos);
+        AllocKind::Fn => {
+            trace!("creating fn alloc id");
             let instance = ty::Instance::decode(decoder)?;
             trace!("decoded fn alloc instance: {:?}", instance);
             let id = tcx.interpret_interner.create_fn_alloc(instance);
             trace!("created fn alloc id: {:?}", id);
-            cache(decoder, pos, id);
+            cache(decoder, id);
             Ok(id)
         },
-        EXTERN_STATIC_DISCRIMINANT => {
-            trace!("creating extern static alloc id at {}", pos);
+        AllocKind::Static => {
+            trace!("creating extern static alloc id at");
             let did = DefId::decode(decoder)?;
-            let alloc_id = tcx.interpret_interner.reserve();
-            tcx.interpret_interner.cache(did, alloc_id);
+            let alloc_id = tcx.interpret_interner.cache_static(did);
+            cache(decoder, alloc_id);
             Ok(alloc_id)
         },
-        shorthand => {
-            trace!("loading shorthand {}", shorthand);
-            short(decoder, shorthand)
-        },
     }
 }
 

src/librustc/ty/context.rs

@@ -956,18 +956,16 @@ struct InterpretInternerInner<'tcx> {
     /// Allows obtaining const allocs via a unique identifier
     alloc_by_id: FxHashMap<interpret::AllocId, &'tcx interpret::Allocation>,
 
-    /// Reverse map of `alloc_cache`
-    global_cache: FxHashMap<interpret::AllocId, DefId>,
+    /// Allows obtaining static def ids via a unique id
+    statics: FxHashMap<interpret::AllocId, DefId>,
 
     /// The AllocId to assign to the next new regular allocation.
     /// Always incremented, never gets smaller.
     next_id: interpret::AllocId,
 
-    /// Allows checking whether a static already has an allocation
-    ///
-    /// This is only important for detecting statics referring to themselves
-    // FIXME(oli-obk) move it to the EvalContext?
-    alloc_cache: FxHashMap<DefId, interpret::AllocId>,
+    /// Inverse map of `statics`
+    /// Used so we don't allocate a new pointer every time we need one
+    static_cache: FxHashMap<DefId, interpret::AllocId>,
 
     /// A cache for basic byte allocations keyed by their contents. This is used to deduplicate
     /// allocations for string and bytestring literals.
@@ -1001,30 +999,25 @@ impl<'tcx> InterpretInterner<'tcx> {
         self.inner.borrow().alloc_by_id.get(&id).cloned()
     }
 
-    pub fn get_cached(
-        &self,
-        static_id: DefId,
-    ) -> Option<interpret::AllocId> {
-        self.inner.borrow().alloc_cache.get(&static_id).cloned()
-    }
-
-    pub fn cache(
+    pub fn cache_static(
         &self,
         static_id: DefId,
-        alloc_id: interpret::AllocId,
-    ) {
-        let mut inner = self.inner.borrow_mut();
-        inner.global_cache.insert(alloc_id, static_id);
-        if let Some(old) = inner.alloc_cache.insert(static_id, alloc_id) {
-            bug!("tried to cache {:?}, but was already existing as {:#?}", static_id, old);
+    ) -> interpret::AllocId {
+        if let Some(alloc_id) = self.inner.borrow().static_cache.get(&static_id).cloned() {
+            return alloc_id;
         }
+        let alloc_id = self.reserve();
+        let mut inner = self.inner.borrow_mut();
+        inner.static_cache.insert(static_id, alloc_id);
+        inner.statics.insert(alloc_id, static_id);
+        alloc_id
     }
 
-    pub fn get_corresponding_static_def_id(
+    pub fn get_static(
         &self,
         ptr: interpret::AllocId,
     ) -> Option<DefId> {
-        self.inner.borrow().global_cache.get(&ptr).cloned()
+        self.inner.borrow().statics.get(&ptr).cloned()
     }
 
     pub fn intern_at_reserved(