Get rid of literal_alloc_cache

src/librustc/ty/context.rs

@@ -960,10 +960,6 @@ struct InterpretInternerInner<'tcx> {
     /// 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.
-    literal_alloc_cache: FxHashMap<Vec<u8>, interpret::AllocId>,
 }
 
 impl<'tcx> InterpretInterner<'tcx> {
@@ -1123,22 +1119,14 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     /// Allocates a byte or string literal for `mir::interpret`
-    pub fn allocate_cached(self, bytes: &[u8]) -> interpret::AllocId {
-        // check whether we already allocated this literal or a constant with the same memory
-        if let Some(&alloc_id) = self.interpret_interner.inner.borrow()
-                                     .literal_alloc_cache.get(bytes) {
-            return alloc_id;
-        }
+    pub fn allocate_bytes(self, bytes: &[u8]) -> interpret::AllocId {
         // create an allocation that just contains these bytes
         let alloc = interpret::Allocation::from_byte_aligned_bytes(bytes);
         let alloc = self.intern_const_alloc(alloc);
 
         // the next unique id
         let id = self.interpret_interner.reserve();
-        // make the allocation identifiable
-        self.interpret_interner.inner.borrow_mut().alloc_by_id.insert(id, alloc);
-        // cache it for the future
-        self.interpret_interner.inner.borrow_mut().literal_alloc_cache.insert(bytes.to_owned(), id);
+        self.interpret_interner.intern_at_reserved(id, alloc);
         id
     }
 

src/librustc/ty/sty.rs

@@ -1860,6 +1860,14 @@ impl<'tcx> Const<'tcx> {
         }
     }
 
+    #[inline]
+    pub fn to_byval_value(&self) -> Option<Value> {
+        match self.val {
+            ConstVal::Value(val) => val.to_byval_value(),
+            _ => None,
+        }
+    }
+
     #[inline]
     pub fn to_primval(&self) -> Option<PrimVal> {
         match self.val {

src/librustc_mir/hair/cx/mod.rs

@@ -181,7 +181,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
         let lit = match *lit {
             LitKind::Str(ref s, _) => {
                 let s = s.as_str();
-                let id = self.tcx.allocate_cached(s.as_bytes());
+                let id = self.tcx.allocate_bytes(s.as_bytes());
                 let ptr = MemoryPointer::new(id, Size::from_bytes(0));
                 ConstValue::ByValPair(
                     PrimVal::Ptr(ptr),
@@ -189,7 +189,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
                 )
             },
             LitKind::ByteStr(ref data) => {
-                let id = self.tcx.allocate_cached(data);
+                let id = self.tcx.allocate_bytes(data);
                 let ptr = MemoryPointer::new(id, Size::from_bytes(0));
                 ConstValue::ByVal(PrimVal::Ptr(ptr))
             },

src/librustc_mir/hair/pattern/mod.rs

@@ -20,7 +20,7 @@ use interpret::{const_val_field, const_variant_index, self};
 
 use rustc::middle::const_val::ConstVal;
 use rustc::mir::{fmt_const_val, Field, BorrowKind, Mutability};
-use rustc::mir::interpret::{PrimVal, GlobalId, ConstValue};
+use rustc::mir::interpret::{PrimVal, GlobalId, ConstValue, Value};
 use rustc::ty::{self, TyCtxt, AdtDef, Ty, Region};
 use rustc::ty::layout::Size;
 use rustc::ty::subst::{Substs, Kind};
@@ -1040,11 +1040,27 @@ pub fn compare_const_vals<'a, 'tcx>(
     ty: Ty<'tcx>,
 ) -> Option<Ordering> {
     trace!("compare_const_vals: {:?}, {:?}", a, b);
+
+    let from_bool = |v: bool| {
+        if v {
+            Some(Ordering::Equal)
+        } else {
+            None
+        }
+    };
+
+    let fallback = || from_bool(a == b);
+
+    // Use the fallback if any type differs
+    if a.ty != b.ty || a.ty != ty {
+        return fallback();
+    }
+
     // FIXME: This should use assert_bits(ty) instead of use_bits
     // but triggers possibly bugs due to mismatching of arrays and slices
     if let (Some(a), Some(b)) = (a.to_bits(ty), b.to_bits(ty)) {
         use ::rustc_apfloat::Float;
-        match ty.sty {
+        return match ty.sty {
             ty::TyFloat(ast::FloatTy::F32) => {
                 let l = ::rustc_apfloat::ieee::Single::from_bits(a);
                 let r = ::rustc_apfloat::ieee::Single::from_bits(b);
@@ -1062,13 +1078,36 @@ pub fn compare_const_vals<'a, 'tcx>(
             },
             _ => Some(a.cmp(&b)),
         }
-    } else {
-        if a == b {
-            Some(Ordering::Equal)
-        } else {
-            None
+    }
+
+    if let ty::TyRef(_, rty, _) = ty.sty {
+        if let ty::TyStr = rty.sty {
+            match (a.to_byval_value(), b.to_byval_value()) {
+                (
+                    Some(Value::ByValPair(
+                        PrimVal::Ptr(ptr_a),
+                        PrimVal::Bytes(size_a))
+                    ),
+                    Some(Value::ByValPair(
+                        PrimVal::Ptr(ptr_b),
+                        PrimVal::Bytes(size_b))
+                    )
+                ) if size_a == size_b => {
+                    if ptr_a.offset == Size::from_bytes(0) && ptr_b.offset == Size::from_bytes(0) {
+                        let map = tcx.alloc_map.lock();
+                        let alloc_a = map.unwrap_memory(ptr_a.alloc_id);
+                        let alloc_b = map.unwrap_memory(ptr_b.alloc_id);
+                        if alloc_a.bytes.len() as u64 == size_a as u64 {
+                            return from_bool(alloc_a == alloc_b);
+                        }
+                    }
+                }
+                _ => (),
+            }
         }
     }
+
+    fallback()
 }
 
 // FIXME: Combine with rustc_mir::hair::cx::const_eval_literal
@@ -1083,7 +1122,7 @@ fn lit_to_const<'a, 'tcx>(lit: &'tcx ast::LitKind,
     let lit = match *lit {
         LitKind::Str(ref s, _) => {
             let s = s.as_str();
-            let id = tcx.allocate_cached(s.as_bytes());
+            let id = tcx.allocate_bytes(s.as_bytes());
             let ptr = MemoryPointer::new(id, Size::from_bytes(0));
             ConstValue::ByValPair(
                 PrimVal::Ptr(ptr),
@@ -1091,7 +1130,7 @@ fn lit_to_const<'a, 'tcx>(lit: &'tcx ast::LitKind,
             )
         },
         LitKind::ByteStr(ref data) => {
-            let id = tcx.allocate_cached(data);
+            let id = tcx.allocate_bytes(data);
             let ptr = MemoryPointer::new(id, Size::from_bytes(0));
             ConstValue::ByVal(PrimVal::Ptr(ptr))
         },

src/librustc_mir/interpret/eval_context.rs

@@ -229,7 +229,7 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
     }
 
     pub fn str_to_value(&mut self, s: &str) -> EvalResult<'tcx, Value> {
-        let ptr = self.memory.allocate_cached(s.as_bytes());
+        let ptr = self.memory.allocate_bytes(s.as_bytes());
         Ok(Value::ByValPair(
             PrimVal::Ptr(ptr),
             PrimVal::from_u128(s.len() as u128),

src/librustc_mir/interpret/memory.rs

@@ -76,8 +76,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         MemoryPointer::new(id, Size::from_bytes(0))
     }
 
-    pub fn allocate_cached(&mut self, bytes: &[u8]) -> MemoryPointer {
-        let id = self.tcx.allocate_cached(bytes);
+    pub fn allocate_bytes(&mut self, bytes: &[u8]) -> MemoryPointer {
+        let id = self.tcx.allocate_bytes(bytes);
         MemoryPointer::new(id, Size::from_bytes(0))
     }