diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index db8791e1..02b0c582 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -340,7 +340,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.14.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=d8bcf90991224cfe06153689b14c3e1eea0e025e#d8bcf90991224cfe06153689b14c3e1eea0e025e"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=76131c493be38e421f5fb157f9900f850584554f#76131c493be38e421f5fb157f9900f850584554f"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -363,7 +363,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.14.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=d8bcf90991224cfe06153689b14c3e1eea0e025e#d8bcf90991224cfe06153689b14c3e1eea0e025e"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=76131c493be38e421f5fb157f9900f850584554f#76131c493be38e421f5fb157f9900f850584554f"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index f8ea0764..1c916c26 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -29,7 +29,7 @@ once_cell = "1.10.0"
 # - change branch
 # - change repo name
 # But other changes including adding/removing whitespaces in commented lines may break the CI.
-mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "d8bcf90991224cfe06153689b14c3e1eea0e025e" }
+mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "76131c493be38e421f5fb157f9900f850584554f" }
 # Uncomment the following to build locally
 # mmtk = { path = "../repos/mmtk-core" }
 
diff --git a/mmtk/src/gc_work.rs b/mmtk/src/gc_work.rs
index 098092e5..8d1ccb45 100644
--- a/mmtk/src/gc_work.rs
+++ b/mmtk/src/gc_work.rs
@@ -1,6 +1,6 @@
 use std::sync::atomic::Ordering;
 
-use super::{OpenJDK, UPCALLS};
+use super::{OpenJDK, OpenJDKEdge, UPCALLS};
 use mmtk::scheduler::*;
 use mmtk::vm::RootsWorkFactory;
 use mmtk::MMTK;
@@ -8,17 +8,17 @@ use scanning::to_edges_closure;
 
 macro_rules! scan_roots_work {
     ($struct_name: ident, $func_name: ident) => {
-        pub struct $struct_name<F: RootsWorkFactory> {
+        pub struct $struct_name<F: RootsWorkFactory<OpenJDKEdge>> {
             factory: F,
         }
 
-        impl<F: RootsWorkFactory> $struct_name<F> {
+        impl<F: RootsWorkFactory<OpenJDKEdge>> $struct_name<F> {
             pub fn new(factory: F) -> Self {
                 Self { factory }
             }
         }
 
-        impl<F: RootsWorkFactory> GCWork<OpenJDK> for $struct_name<F> {
+        impl<F: RootsWorkFactory<OpenJDKEdge>> GCWork<OpenJDK> for $struct_name<F> {
             fn do_work(&mut self, _worker: &mut GCWorker<OpenJDK>, _mmtk: &'static MMTK<OpenJDK>) {
                 unsafe {
                     ((*UPCALLS).$func_name)(to_edges_closure(&mut self.factory));
@@ -43,17 +43,17 @@ scan_roots_work!(
 scan_roots_work!(ScanWeakProcessorRoots, scan_weak_processor_roots);
 scan_roots_work!(ScanVMThreadRoots, scan_vm_thread_roots);
 
-pub struct ScanCodeCacheRoots<F: RootsWorkFactory> {
+pub struct ScanCodeCacheRoots<F: RootsWorkFactory<OpenJDKEdge>> {
     factory: F,
 }
 
-impl<F: RootsWorkFactory> ScanCodeCacheRoots<F> {
+impl<F: RootsWorkFactory<OpenJDKEdge>> ScanCodeCacheRoots<F> {
     pub fn new(factory: F) -> Self {
         Self { factory }
     }
 }
 
-impl<F: RootsWorkFactory> GCWork<OpenJDK> for ScanCodeCacheRoots<F> {
+impl<F: RootsWorkFactory<OpenJDKEdge>> GCWork<OpenJDK> for ScanCodeCacheRoots<F> {
     fn do_work(&mut self, _worker: &mut GCWorker<OpenJDK>, _mmtk: &'static MMTK<OpenJDK>) {
         // Collect all the cached roots
         let mut edges = Vec::with_capacity(crate::CODE_CACHE_ROOTS_SIZE.load(Ordering::Relaxed));
diff --git a/mmtk/src/lib.rs b/mmtk/src/lib.rs
index 45898b6b..5656a544 100644
--- a/mmtk/src/lib.rs
+++ b/mmtk/src/lib.rs
@@ -114,12 +114,21 @@ pub static GLOBAL_ALLOC_BIT_ADDRESS: uintptr_t =
 #[derive(Default)]
 pub struct OpenJDK;
 
+/// The type of edges in OpenJDK.
+///
+/// TODO: We currently make it an alias to Address to make the change minimal.
+/// If we support CompressedOOPs, we should define an enum type to support both
+/// compressed and uncompressed OOPs.
+pub type OpenJDKEdge = Address;
+
 impl VMBinding for OpenJDK {
     type VMObjectModel = object_model::VMObjectModel;
     type VMScanning = scanning::VMScanning;
     type VMCollection = collection::VMCollection;
     type VMActivePlan = active_plan::VMActivePlan;
     type VMReferenceGlue = reference_glue::VMReferenceGlue;
+
+    type VMEdge = OpenJDKEdge;
 }
 
 use std::sync::atomic::AtomicBool;
diff --git a/mmtk/src/object_scanning.rs b/mmtk/src/object_scanning.rs
index ae9277dc..4ad2b43a 100644
--- a/mmtk/src/object_scanning.rs
+++ b/mmtk/src/object_scanning.rs
@@ -1,5 +1,5 @@
 use super::abi::*;
-use super::UPCALLS;
+use super::{OpenJDKEdge, UPCALLS};
 use mmtk::util::constants::*;
 use mmtk::util::opaque_pointer::*;
 use mmtk::util::{Address, ObjectReference};
@@ -7,12 +7,12 @@ use mmtk::vm::EdgeVisitor;
 use std::{mem, slice};
 
 trait OopIterate: Sized {
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor);
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>);
 }
 
 impl OopIterate for OopMapBlock {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         let start = oop.get_field_address(self.offset);
         for i in 0..self.count as usize {
             let edge = start + (i << LOG_BYTES_IN_ADDRESS);
@@ -23,7 +23,7 @@ impl OopIterate for OopMapBlock {
 
 impl OopIterate for InstanceKlass {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         let oop_maps = self.nonstatic_oop_maps();
         for map in oop_maps {
             map.oop_iterate(oop, closure)
@@ -33,7 +33,7 @@ impl OopIterate for InstanceKlass {
 
 impl OopIterate for InstanceMirrorKlass {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         self.instance_klass.oop_iterate(oop, closure);
         // if (Devirtualizer::do_metadata(closure)) {
         //     Klass* klass = java_lang_Class::as_Klass(obj);
@@ -74,7 +74,7 @@ impl OopIterate for InstanceMirrorKlass {
 
 impl OopIterate for InstanceClassLoaderKlass {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         self.instance_klass.oop_iterate(oop, closure);
         // if (Devirtualizer::do_metadata(closure)) {
         //     ClassLoaderData* cld = java_lang_ClassLoader::loader_data(obj);
@@ -88,7 +88,7 @@ impl OopIterate for InstanceClassLoaderKlass {
 
 impl OopIterate for ObjArrayKlass {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         let array = unsafe { oop.as_array_oop() };
         for oop in unsafe { array.data::<Oop>(BasicType::T_OBJECT) } {
             closure.visit_edge(Address::from_ref(oop as &Oop));
@@ -98,7 +98,7 @@ impl OopIterate for ObjArrayKlass {
 
 impl OopIterate for TypeArrayKlass {
     #[inline]
-    fn oop_iterate(&self, _oop: Oop, _closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, _oop: Oop, _closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         // Performance tweak: We skip processing the klass pointer since all
         // TypeArrayKlasses are guaranteed processed via the null class loader.
     }
@@ -106,7 +106,7 @@ impl OopIterate for TypeArrayKlass {
 
 impl OopIterate for InstanceRefKlass {
     #[inline]
-    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn oop_iterate(&self, oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         use crate::abi::*;
         use crate::api::{add_phantom_candidate, add_soft_candidate, add_weak_candidate};
         self.instance_klass.oop_iterate(oop, closure);
@@ -139,7 +139,7 @@ impl InstanceRefKlass {
         !*SINGLETON.get_options().no_reference_types
     }
     #[inline]
-    fn process_ref_as_strong(oop: Oop, closure: &mut impl EdgeVisitor) {
+    fn process_ref_as_strong(oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
         let referent_addr = Self::referent_address(oop);
         closure.visit_edge(referent_addr);
         let discovered_addr = Self::discovered_address(oop);
@@ -148,14 +148,14 @@ impl InstanceRefKlass {
 }
 
 #[allow(unused)]
-fn oop_iterate_slow(oop: Oop, closure: &mut impl EdgeVisitor, tls: OpaquePointer) {
+fn oop_iterate_slow(oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>, tls: OpaquePointer) {
     unsafe {
         ((*UPCALLS).scan_object)(closure as *mut _ as _, mem::transmute(oop), tls);
     }
 }
 
 #[inline]
-fn oop_iterate(oop: Oop, closure: &mut impl EdgeVisitor) {
+fn oop_iterate(oop: Oop, closure: &mut impl EdgeVisitor<OpenJDKEdge>) {
     let klass_id = oop.klass.id;
     debug_assert!(
         klass_id as i32 >= 0 && (klass_id as i32) < 6,
@@ -192,7 +192,11 @@ fn oop_iterate(oop: Oop, closure: &mut impl EdgeVisitor) {
 }
 
 #[inline]
-pub fn scan_object(object: ObjectReference, closure: &mut impl EdgeVisitor, _tls: VMWorkerThread) {
+pub fn scan_object(
+    object: ObjectReference,
+    closure: &mut impl EdgeVisitor<OpenJDKEdge>,
+    _tls: VMWorkerThread,
+) {
     // println!("*****scan_object(0x{:x}) -> \n 0x{:x}, 0x{:x} \n",
     //     object,
     //     unsafe { *(object.value() as *const usize) },
diff --git a/mmtk/src/scanning.rs b/mmtk/src/scanning.rs
index 8323d9eb..eeef2fc5 100644
--- a/mmtk/src/scanning.rs
+++ b/mmtk/src/scanning.rs
@@ -1,5 +1,5 @@
 use super::gc_work::*;
-use super::{NewBuffer, SINGLETON, UPCALLS};
+use super::{NewBuffer, OpenJDKEdge, SINGLETON, UPCALLS};
 use crate::{EdgesClosure, OpenJDK};
 use mmtk::memory_manager;
 use mmtk::scheduler::WorkBucketStage;
@@ -13,7 +13,7 @@ pub struct VMScanning {}
 
 const WORK_PACKET_CAPACITY: usize = 4096;
 
-extern "C" fn report_edges_and_renew_buffer<F: RootsWorkFactory>(
+extern "C" fn report_edges_and_renew_buffer<F: RootsWorkFactory<OpenJDKEdge>>(
     ptr: *mut Address,
     length: usize,
     capacity: usize,
@@ -34,7 +34,7 @@ extern "C" fn report_edges_and_renew_buffer<F: RootsWorkFactory>(
     NewBuffer { ptr, capacity }
 }
 
-pub(crate) fn to_edges_closure<F: RootsWorkFactory>(factory: &mut F) -> EdgesClosure {
+pub(crate) fn to_edges_closure<F: RootsWorkFactory<OpenJDKEdge>>(factory: &mut F) -> EdgesClosure {
     EdgesClosure {
         func: report_edges_and_renew_buffer::<F> as *const _,
         data: factory as *mut F as *mut libc::c_void,
@@ -45,7 +45,7 @@ impl Scanning<OpenJDK> for VMScanning {
     const SCAN_MUTATORS_IN_SAFEPOINT: bool = false;
     const SINGLE_THREAD_MUTATOR_SCANNING: bool = false;
 
-    fn scan_object<EV: EdgeVisitor>(
+    fn scan_object<EV: EdgeVisitor<OpenJDKEdge>>(
         tls: VMWorkerThread,
         object: ObjectReference,
         edge_visitor: &mut EV,
@@ -58,7 +58,7 @@ impl Scanning<OpenJDK> for VMScanning {
         // TODO
     }
 
-    fn scan_thread_roots(_tls: VMWorkerThread, mut factory: impl RootsWorkFactory) {
+    fn scan_thread_roots(_tls: VMWorkerThread, mut factory: impl RootsWorkFactory<OpenJDKEdge>) {
         unsafe {
             ((*UPCALLS).scan_all_thread_roots)(to_edges_closure(&mut factory));
         }
@@ -67,7 +67,7 @@ impl Scanning<OpenJDK> for VMScanning {
     fn scan_thread_root(
         _tls: VMWorkerThread,
         mutator: &'static mut Mutator<OpenJDK>,
-        mut factory: impl RootsWorkFactory,
+        mut factory: impl RootsWorkFactory<OpenJDKEdge>,
     ) {
         let tls = mutator.get_tls();
         unsafe {
@@ -75,7 +75,7 @@ impl Scanning<OpenJDK> for VMScanning {
         }
     }
 
-    fn scan_vm_specific_roots(_tls: VMWorkerThread, factory: impl RootsWorkFactory) {
+    fn scan_vm_specific_roots(_tls: VMWorkerThread, factory: impl RootsWorkFactory<OpenJDKEdge>) {
         memory_manager::add_work_packets(
             &SINGLETON,
             WorkBucketStage::Prepare,