Use SortedMap instead of BTreeMap for relocations in MIRI.

Author: michaelwoerister

src/librustc/mir/interpret/mod.rs

@@ -12,7 +12,6 @@ pub use self::error::{EvalError, EvalResult, EvalErrorKind, AssertMessage};
 
 pub use self::value::{PrimVal, PrimValKind, Value, Pointer, ConstValue};
 
-use std::collections::BTreeMap;
 use std::fmt;
 use mir;
 use hir::def_id::DefId;
@@ -21,9 +20,11 @@ use ty::layout::{self, Align, HasDataLayout, Size};
 use middle::region;
 use std::iter;
 use std::io;
+use std::ops::{Deref, DerefMut};
 use std::hash::Hash;
 use syntax::ast::Mutability;
 use rustc_serialize::{Encoder, Decoder, Decodable, Encodable};
+use rustc_data_structures::sorted_map::SortedMap;
 use rustc_data_structures::fx::FxHashMap;
 use byteorder::{WriteBytesExt, ReadBytesExt, LittleEndian, BigEndian};
 
@@ -341,7 +342,7 @@ pub struct Allocation {
     pub bytes: Vec<u8>,
     /// Maps from byte addresses to allocations.
     /// Only the first byte of a pointer is inserted into the map.
-    pub relocations: BTreeMap<Size, AllocId>,
+    pub relocations: Relocations,
     /// Denotes undefined memory. Reading from undefined memory is forbidden in miri
     pub undef_mask: UndefMask,
     /// The alignment of the allocation to detect unaligned reads.
@@ -358,7 +359,7 @@ impl Allocation {
         undef_mask.grow(Size::from_bytes(slice.len() as u64), true);
         Self {
             bytes: slice.to_owned(),
-            relocations: BTreeMap::new(),
+            relocations: Relocations::new(),
             undef_mask,
             align,
             runtime_mutability: Mutability::Immutable,
@@ -373,7 +374,7 @@ impl Allocation {
         assert_eq!(size.bytes() as usize as u64, size.bytes());
         Allocation {
             bytes: vec![0; size.bytes() as usize],
-            relocations: BTreeMap::new(),
+            relocations: Relocations::new(),
             undef_mask: UndefMask::new(size),
             align,
             runtime_mutability: Mutability::Immutable,
@@ -383,6 +384,35 @@ impl Allocation {
 
 impl<'tcx> ::serialize::UseSpecializedDecodable for &'tcx Allocation {}
 
+#[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+pub struct Relocations(SortedMap<Size, AllocId>);
+
+impl Relocations {
+    pub fn new() -> Relocations {
+        Relocations(SortedMap::new())
+    }
+
+    // The caller must guarantee that the given relocations are already sorted
+    // by address and contain no duplicates.
+    pub fn from_presorted(r: Vec<(Size, AllocId)>) -> Relocations {
+        Relocations(SortedMap::from_presorted_elements(r))
+    }
+}
+
+impl Deref for Relocations {
+    type Target = SortedMap<Size, AllocId>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for Relocations {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Methods to access integers in the target endianness
 ////////////////////////////////////////////////////////////////////////////////

src/librustc_codegen_llvm/mir/constant.rs

@@ -83,7 +83,7 @@ pub fn const_alloc_to_llvm(cx: &CodegenCx, alloc: &Allocation) -> ValueRef {
     let pointer_size = layout.pointer_size.bytes() as usize;
 
     let mut next_offset = 0;
-    for (&offset, &alloc_id) in &alloc.relocations {
+    for &(offset, alloc_id) in alloc.relocations.iter() {
         let offset = offset.bytes();
         assert_eq!(offset as usize as u64, offset);
         let offset = offset as usize;

src/librustc_mir/interpret/memory.rs

@@ -1,4 +1,4 @@
-use std::collections::{btree_map, VecDeque};
+use std::collections::VecDeque;
 use std::ptr;
 
 use rustc::hir::def_id::DefId;
@@ -519,7 +519,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
 
     fn get_bytes(&self, ptr: MemoryPointer, size: Size, align: Align) -> EvalResult<'tcx, &[u8]> {
         assert_ne!(size.bytes(), 0);
-        if self.relocations(ptr, size)?.count() != 0 {
+        if self.relocations(ptr, size)?.len() != 0 {
             return err!(ReadPointerAsBytes);
         }
         self.check_defined(ptr, size)?;
@@ -614,9 +614,9 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         // first copy the relocations to a temporary buffer, because
         // `get_bytes_mut` will clear the relocations, which is correct,
         // since we don't want to keep any relocations at the target.
-
         let relocations: Vec<_> = self.relocations(src, size)?
-            .map(|(&offset, &alloc_id)| {
+            .iter()
+            .map(|&(offset, alloc_id)| {
                 // Update relocation offsets for the new positions in the destination allocation.
                 (offset + dest.offset - src.offset, alloc_id)
             })
@@ -648,7 +648,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
 
         self.copy_undef_mask(src, dest, size)?;
         // copy back the relocations
-        self.get_mut(dest.alloc_id)?.relocations.extend(relocations);
+        self.get_mut(dest.alloc_id)?.relocations.insert_presorted(relocations);
 
         Ok(())
     }
@@ -660,7 +660,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         match alloc.bytes[offset..].iter().position(|&c| c == 0) {
             Some(size) => {
                 let p1 = Size::from_bytes((size + 1) as u64);
-                if self.relocations(ptr, p1)?.count() != 0 {
+                if self.relocations(ptr, p1)?.len() != 0 {
                     return err!(ReadPointerAsBytes);
                 }
                 self.check_defined(ptr, p1)?;
@@ -720,7 +720,7 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         let bytes = read_target_uint(endianness, bytes).unwrap();
         // See if we got a pointer
         if size != self.pointer_size() {
-            if self.relocations(ptr, size)?.count() != 0 {
+            if self.relocations(ptr, size)?.len() != 0 {
                 return err!(ReadPointerAsBytes);
             }
         } else {
@@ -808,24 +808,26 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         &self,
         ptr: MemoryPointer,
         size: Size,
-    ) -> EvalResult<'tcx, btree_map::Range<Size, AllocId>> {
+    ) -> EvalResult<'tcx, &[(Size, AllocId)]> {
         let start = ptr.offset.bytes().saturating_sub(self.pointer_size().bytes() - 1);
         let end = ptr.offset + size;
         Ok(self.get(ptr.alloc_id)?.relocations.range(Size::from_bytes(start)..end))
     }
 
     fn clear_relocations(&mut self, ptr: MemoryPointer, size: Size) -> EvalResult<'tcx> {
-        // Find all relocations overlapping the given range.
-        let keys: Vec<_> = self.relocations(ptr, size)?.map(|(&k, _)| k).collect();
-        if keys.is_empty() {
-            return Ok(());
-        }
-
         // Find the start and end of the given range and its outermost relocations.
+        let (first, last) = {
+            // Find all relocations overlapping the given range.
+            let relocations = self.relocations(ptr, size)?;
+            if relocations.is_empty() {
+                return Ok(());
+            }
+
+            (relocations.first().unwrap().0,
+             relocations.last().unwrap().0 + self.pointer_size())
+        };
         let start = ptr.offset;
         let end = start + size;
-        let first = *keys.first().unwrap();
-        let last = *keys.last().unwrap() + self.pointer_size();
 
         let alloc = self.get_mut(ptr.alloc_id)?;
 
@@ -839,16 +841,14 @@ impl<'a, 'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'a, 'mir, 'tcx, M> {
         }
 
         // Forget all the relocations.
-        for k in keys {
-            alloc.relocations.remove(&k);
-        }
+        alloc.relocations.remove_range(first ..= last);
 
         Ok(())
     }
 
     fn check_relocation_edges(&self, ptr: MemoryPointer, size: Size) -> EvalResult<'tcx> {
-        let overlapping_start = self.relocations(ptr, Size::from_bytes(0))?.count();
-        let overlapping_end = self.relocations(ptr.offset(size, self)?, Size::from_bytes(0))?.count();
+        let overlapping_start = self.relocations(ptr, Size::from_bytes(0))?.len();
+        let overlapping_end = self.relocations(ptr.offset(size, self)?, Size::from_bytes(0))?.len();
         if overlapping_start + overlapping_end != 0 {
             return err!(ReadPointerAsBytes);
         }