diff --git a/src/components/util/smallvec.rs b/src/components/util/smallvec.rs
new file mode 100644
index 00000000000..67b796d673e
--- /dev/null
+++ b/src/components/util/smallvec.rs
@@ -0,0 +1,498 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//! Small vectors in various sizes. These store a certain number of elements inline and fall back
+//! to the heap for larger allocations.
+
+use i = std::unstable::intrinsics::init;
+use std::cast;
+use std::libc::c_char;
+use std::mem;
+use std::num;
+use std::ptr;
+use std::rt::global_heap;
+use std::rt::local_heap;
+use std::unstable::intrinsics;
+use std::unstable::raw::Slice;
+use std::util;
+
+// Generic code for all small vectors
+
+trait SmallVecPrivate<T> {
+    unsafe fn set_len(&mut self, new_len: uint);
+    unsafe fn set_cap(&mut self, new_cap: uint);
+    fn data(&self, index: uint) -> *T;
+    fn mut_data(&mut self, index: uint) -> *mut T;
+    unsafe fn ptr(&self) -> *T;
+    unsafe fn mut_ptr(&mut self) -> *mut T;
+    unsafe fn set_ptr(&mut self, new_ptr: *mut T);
+}
+
+pub trait SmallVec<T> : SmallVecPrivate<T> {
+    fn inline_size(&self) -> uint;
+    fn len(&self) -> uint;
+    fn cap(&self) -> uint;
+
+    fn spilled(&self) -> bool {
+        self.cap() > self.inline_size()
+    }
+
+    fn begin(&self) -> *T {
+        unsafe {
+            if self.spilled() {
+                self.ptr()
+            } else {
+                self.data(0)
+            }
+        }
+    }
+
+    fn end(&self) -> *T {
+        unsafe {
+            self.begin().offset(self.len() as int)
+        }
+    }
+
+    fn iter<'a>(&'a self) -> SmallVecIterator<'a,T> {
+        SmallVecIterator {
+            ptr: self.begin(),
+            end: self.end(),
+            lifetime: None,
+        }
+    }
+
+    /// NB: For efficiency reasons (avoiding making a second copy of the inline elements), this
+    /// actually clears out the original array instead of moving it.
+    fn move_iter<'a>(&'a mut self) -> SmallVecMoveIterator<'a,T> {
+        unsafe {
+            let iter = cast::transmute(self.iter());
+            let ptr_opt = if self.spilled() {
+                Some(cast::transmute(self.ptr()))
+            } else {
+                None
+            };
+            let inline_size = self.inline_size();
+            self.set_cap(inline_size);
+            self.set_len(0);
+            SmallVecMoveIterator {
+                allocation: ptr_opt,
+                iter: iter,
+                lifetime: None,
+            }
+        }
+    }
+
+    fn push(&mut self, value: T) {
+        let cap = self.cap();
+        if self.len() == cap {
+            self.grow(num::max(cap * 2, 1))
+        }
+        unsafe {
+            let end: &mut T = cast::transmute(self.end());
+            intrinsics::move_val_init(end, value);
+            let len = self.len();
+            self.set_len(len + 1)
+        }
+    }
+
+    fn grow(&mut self, new_cap: uint) {
+        unsafe {
+            let new_alloc: *mut T = cast::transmute(global_heap::malloc_raw(mem::size_of::<T>() *
+                                                                            new_cap));
+            ptr::copy_nonoverlapping_memory(new_alloc, self.begin(), self.len());
+
+            if self.spilled() {
+                if intrinsics::owns_managed::<T>() {
+                    local_heap::local_free(self.ptr() as *u8 as *c_char)
+                } else {
+                    global_heap::exchange_free(self.ptr() as *u8 as *c_char)
+                }
+            } else {
+                let mut_begin: *mut T = cast::transmute(self.begin());
+                intrinsics::set_memory(mut_begin, 0, self.len())
+            }
+
+            self.set_ptr(new_alloc);
+            self.set_cap(new_cap)
+        }
+    }
+
+    fn get<'a>(&'a self, index: uint) -> &'a T {
+        if index >= self.len() {
+            self.fail_bounds_check(index)
+        }
+        unsafe {
+            cast::transmute(self.begin().offset(index as int))
+        }
+    }
+
+    fn get_mut<'a>(&'a mut self, index: uint) -> &'a mut T {
+        if index >= self.len() {
+            self.fail_bounds_check(index)
+        }
+        unsafe {
+            cast::transmute(self.begin().offset(index as int))
+        }
+    }
+
+    fn slice<'a>(&'a self, start: uint, end: uint) -> &'a [T] {
+        assert!(start <= end);
+        assert!(end <= self.len());
+        unsafe {
+            cast::transmute(Slice {
+                data: self.begin().offset(start as int),
+                len: (end - start)
+            })
+        }
+    }
+
+    fn as_slice<'a>(&'a self) -> &'a [T] {
+        self.slice(0, self.len())
+    }
+
+    fn mut_slice<'a>(&'a mut self, start: uint, end: uint) -> &'a mut [T] {
+        assert!(start <= end);
+        assert!(end <= self.len());
+        unsafe {
+            cast::transmute(Slice {
+                data: self.begin().offset(start as int),
+                len: (end - start)
+            })
+        }
+    }
+
+    fn mut_slice_from<'a>(&'a mut self, start: uint) -> &'a mut [T] {
+        let len = self.len();
+        self.mut_slice(start, len)
+    }
+
+    fn fail_bounds_check(&self, index: uint) {
+        fail!("index {} beyond length ({})", index, self.len())
+    }
+}
+
+pub struct SmallVecIterator<'a,T> {
+    priv ptr: *T,
+    priv end: *T,
+    priv lifetime: Option<&'a T>
+}
+
+impl<'a,T> Iterator<&'a T> for SmallVecIterator<'a,T> {
+    #[inline]
+    fn next(&mut self) -> Option<&'a T> {
+        unsafe {
+            if self.ptr == self.end {
+                return None
+            }
+            let old = self.ptr;
+            self.ptr = if mem::size_of::<T>() == 0 {
+                cast::transmute(self.ptr as uint + 1)
+            } else {
+                self.ptr.offset(1)
+            };
+            Some(cast::transmute(old))
+        }
+    }
+}
+
+pub struct SmallVecMoveIterator<'a,T> {
+    priv allocation: Option<*mut u8>,
+    priv iter: SmallVecIterator<'static,T>,
+    priv lifetime: Option<&'a T>,
+}
+
+impl<'a,T> Iterator<T> for SmallVecMoveIterator<'a,T> {
+    #[inline]
+    fn next(&mut self) -> Option<T> {
+        unsafe {
+            match self.iter.next() {
+                None => None,
+                Some(reference) => {
+                    // Zero out the values as we go so they don't get double-freed.
+                    let reference: &mut T = cast::transmute(reference);
+                    Some(util::replace(reference, intrinsics::init()))
+                }
+            }
+        }
+    }
+}
+
+#[unsafe_destructor]
+impl<'a,T> Drop for SmallVecMoveIterator<'a,T> {
+    fn drop(&mut self) {
+        // Destroy the remaining elements.
+        for _ in *self {}
+
+        match self.allocation {
+            None => {}
+            Some(allocation) => {
+                unsafe {
+                    if intrinsics::owns_managed::<T>() {
+                        local_heap::local_free(allocation as *u8 as *c_char)
+                    } else {
+                        global_heap::exchange_free(allocation as *u8 as *c_char)
+                    }
+                }
+            }
+        }
+    }
+}
+
+// Concrete implementations
+
+macro_rules! def_small_vector(
+    ($name:ident, $size:expr) => (
+        pub struct $name<T> {
+            len: uint,
+            cap: uint,
+            ptr: *T,
+            data: [T, ..$size],
+        }
+    )
+)
+
+macro_rules! def_small_vector_private_trait_impl(
+    ($name:ident, $size:expr) => (
+        impl<T> SmallVecPrivate<T> for $name<T> {
+            unsafe fn set_len(&mut self, new_len: uint) {
+                self.len = new_len
+            }
+            unsafe fn set_cap(&mut self, new_cap: uint) {
+                self.cap = new_cap
+            }
+            fn data(&self, index: uint) -> *T {
+                let ptr: *T = &self.data[index];
+                ptr
+            }
+            fn mut_data(&mut self, index: uint) -> *mut T {
+                let ptr: *mut T = &mut self.data[index];
+                ptr
+            }
+            unsafe fn ptr(&self) -> *T {
+                self.ptr
+            }
+            unsafe fn mut_ptr(&mut self) -> *mut T {
+                cast::transmute(self.ptr)
+            }
+            unsafe fn set_ptr(&mut self, new_ptr: *mut T) {
+                self.ptr = cast::transmute(new_ptr)
+            }
+        }
+    )
+)
+
+macro_rules! def_small_vector_trait_impl(
+    ($name:ident, $size:expr) => (
+        impl<T> SmallVec<T> for $name<T> {
+            fn inline_size(&self) -> uint {
+                $size
+            }
+            fn len(&self) -> uint {
+                self.len
+            }
+            fn cap(&self) -> uint {
+                self.cap
+            }
+        }
+    )
+)
+
+macro_rules! def_small_vector_drop_impl(
+    ($name:ident, $size:expr) => (
+        #[unsafe_destructor]
+        impl<T> Drop for $name<T> {
+            fn drop(&mut self) {
+                if !self.spilled() {
+                    return
+                }
+
+                unsafe {
+                    let ptr = self.mut_ptr();
+                    for i in range(0, self.len()) {
+                        *ptr.offset(i as int) = intrinsics::uninit();
+                    }
+
+                    if intrinsics::owns_managed::<T>() {
+                        local_heap::local_free(self.ptr() as *u8 as *c_char)
+                    } else {
+                        global_heap::exchange_free(self.ptr() as *u8 as *c_char)
+                    }
+                }
+            }
+        }
+    )
+)
+
+macro_rules! def_small_vector_impl(
+    ($name:ident, $size:expr) => (
+        impl<T> $name<T> {
+            #[inline]
+            pub fn new() -> $name<T> {
+                unsafe {
+                    $name {
+                        len: 0,
+                        cap: $size,
+                        ptr: ptr::null(),
+                        data: intrinsics::init(),
+                    }
+                }
+            }
+        }
+    )
+)
+
+/// TODO(pcwalton): Remove in favor of `vec_ng` after a Rust upgrade.
+pub struct SmallVec0<T> {
+    len: uint,
+    cap: uint,
+    ptr: *mut T,
+}
+
+impl<T> SmallVecPrivate<T> for SmallVec0<T> {
+    unsafe fn set_len(&mut self, new_len: uint) {
+        self.len = new_len
+    }
+    unsafe fn set_cap(&mut self, new_cap: uint) {
+        self.cap = new_cap
+    }
+    fn data(&self, _: uint) -> *T {
+        ptr::null()
+    }
+    fn mut_data(&mut self, _: uint) -> *mut T {
+        ptr::mut_null()
+    }
+    unsafe fn ptr(&self) -> *T {
+        cast::transmute(self.ptr)
+    }
+    unsafe fn mut_ptr(&mut self) -> *mut T {
+        self.ptr
+    }
+    unsafe fn set_ptr(&mut self, new_ptr: *mut T) {
+        self.ptr = new_ptr
+    }
+}
+
+impl<T> SmallVec<T> for SmallVec0<T> {
+    fn inline_size(&self) -> uint {
+        0
+    }
+    fn len(&self) -> uint {
+        self.len
+    }
+    fn cap(&self) -> uint {
+        self.cap
+    }
+}
+
+impl<T> SmallVec0<T> {
+    pub fn new() -> SmallVec0<T> {
+        SmallVec0 {
+            len: 0,
+            cap: 0,
+            ptr: ptr::mut_null(),
+        }
+    }
+}
+
+def_small_vector_drop_impl!(SmallVec0, 0)
+
+def_small_vector!(SmallVec1, 1)
+def_small_vector_private_trait_impl!(SmallVec1, 1)
+def_small_vector_trait_impl!(SmallVec1, 1)
+def_small_vector_drop_impl!(SmallVec1, 1)
+def_small_vector_impl!(SmallVec1, 1)
+
+def_small_vector!(SmallVec2, 2)
+def_small_vector_private_trait_impl!(SmallVec2, 2)
+def_small_vector_trait_impl!(SmallVec2, 2)
+def_small_vector_drop_impl!(SmallVec2, 2)
+def_small_vector_impl!(SmallVec2, 2)
+
+def_small_vector!(SmallVec4, 4)
+def_small_vector_private_trait_impl!(SmallVec4, 4)
+def_small_vector_trait_impl!(SmallVec4, 4)
+def_small_vector_drop_impl!(SmallVec4, 4)
+def_small_vector_impl!(SmallVec4, 4)
+
+def_small_vector!(SmallVec8, 8)
+def_small_vector_private_trait_impl!(SmallVec8, 8)
+def_small_vector_trait_impl!(SmallVec8, 8)
+def_small_vector_drop_impl!(SmallVec8, 8)
+def_small_vector_impl!(SmallVec8, 8)
+
+def_small_vector!(SmallVec16, 16)
+def_small_vector_private_trait_impl!(SmallVec16, 16)
+def_small_vector_trait_impl!(SmallVec16, 16)
+def_small_vector_drop_impl!(SmallVec16, 16)
+def_small_vector_impl!(SmallVec16, 16)
+
+def_small_vector!(SmallVec24, 24)
+def_small_vector_private_trait_impl!(SmallVec24, 24)
+def_small_vector_trait_impl!(SmallVec24, 24)
+def_small_vector_drop_impl!(SmallVec24, 24)
+def_small_vector_impl!(SmallVec24, 24)
+
+def_small_vector!(SmallVec32, 32)
+def_small_vector_private_trait_impl!(SmallVec32, 32)
+def_small_vector_trait_impl!(SmallVec32, 32)
+def_small_vector_drop_impl!(SmallVec32, 32)
+def_small_vector_impl!(SmallVec32, 32)
+
+#[cfg(test)]
+pub mod tests {
+    use smallvec::{SmallVec, SmallVec0, SmallVec2, SmallVec16};
+
+    // We heap allocate all these strings so that double frees will show up under valgrind.
+
+    #[test]
+    pub fn test_inline() {
+        let mut v = SmallVec16::new();
+        v.push(~"hello");
+        v.push(~"there");
+        assert_eq!(v.as_slice(), &[~"hello", ~"there"]);
+    }
+
+    #[test]
+    pub fn test_spill() {
+        let mut v = SmallVec2::new();
+        v.push(~"hello");
+        v.push(~"there");
+        v.push(~"burma");
+        v.push(~"shave");
+        assert_eq!(v.as_slice(), &[~"hello", ~"there", ~"burma", ~"shave"]);
+    }
+
+    #[test]
+    pub fn test_double_spill() {
+        let mut v = SmallVec2::new();
+        v.push(~"hello");
+        v.push(~"there");
+        v.push(~"burma");
+        v.push(~"shave");
+        v.push(~"hello");
+        v.push(~"there");
+        v.push(~"burma");
+        v.push(~"shave");
+        assert_eq!(v.as_slice(), &[
+            ~"hello", ~"there", ~"burma", ~"shave", ~"hello", ~"there", ~"burma", ~"shave",
+        ]);
+    }
+
+    #[test]
+    pub fn test_smallvec0() {
+        let mut v = SmallVec0::new();
+        v.push(~"hello");
+        v.push(~"there");
+        v.push(~"burma");
+        v.push(~"shave");
+        v.push(~"hello");
+        v.push(~"there");
+        v.push(~"burma");
+        v.push(~"shave");
+        assert_eq!(v.as_slice(), &[
+            ~"hello", ~"there", ~"burma", ~"shave", ~"hello", ~"there", ~"burma", ~"shave",
+        ]);
+    }
+}
+
diff --git a/src/components/util/util.rc b/src/components/util/util.rc
index e8acfeab1f5..bfcb086c075 100644
--- a/src/components/util/util.rc
+++ b/src/components/util/util.rc
@@ -23,3 +23,5 @@ pub mod task;
 pub mod workqueue;
 pub mod namespace;
 pub mod sort;
+pub mod smallvec;
+