make specs work

vmkit/Cargo.toml

@@ -32,7 +32,7 @@ uncooperative = ["cooperative", "mmtk/immix_non_moving", "mmtk/immix_zero_on_rel
 # VMKit is built for use in cooperative runtime. Such runtime
 # would be able to use write barriers and safepoints. Such environment
 # must also provide precise object layout (stack can be uncooperative).
-cooperative = ["mmtk/vo_bit", "mmtk/is_mmtk_object", "mmtk/vo_bit_access", "mmtk/immix_non_moving"]
+cooperative = ["object_pinning", "mmtk/vo_bit", "mmtk/is_mmtk_object", "mmtk/vo_bit_access", "mmtk/immix_non_moving"]
 # VMKit is built for use in full-precise runtime. Such runtime
 # would be able to use precise write barriers and safepoints, object
 # layout is fully precise.

vmkit/examples/binarytrees.rs

@@ -72,7 +72,7 @@ impl VirtualMachine for BenchVM {
     #[cfg(feature="vmside_forwarding")]
     const LOCAL_FORWARDING_POINTER_SPEC: mmtk::vm::VMLocalForwardingPointerSpec = mmtk::vm::VMLocalForwardingPointerSpec::in_header(0);
     #[cfg(feature="vmside_forwarding")]
-    const LOCAL_FORWARDING_BITS_SPEC: mmtk::vm::VMLocalForwardingBitsSpec = mmtk::vm::VMLocalForwardingBitsSpec::side_first();
+    const LOCAL_FORWARDING_BITS_SPEC: mmtk::vm::VMLocalForwardingBitsSpec = mmtk::vm::VMLocalForwardingBitsSpec::in_header(62);
 
     fn get() -> &'static Self {
         VM.get().unwrap()

vmkit/src/lib.rs

@@ -27,13 +27,20 @@ pub trait VirtualMachine: Sized + 'static + Send + Sync {
     type Slot: SlotExtra;
     type MemorySlice: MemorySlice<SlotType = Self::Slot>;
 
-
+    /// 1-word local metadata for spaces that may copy objects.
-    #[cfg(feature="vmside_forwarding")]
+    /// This metadata has to be stored in the header.
+    /// This metadata can be defined at a position within the object payload.
+    /// As a forwarding pointer is only stored in dead objects which is not
+    /// accessible by the language, it is okay that store a forwarding pointer overwrites object payload
+    ///
+    #[cfg(feature = "vmside_forwarding")]
     const LOCAL_FORWARDING_POINTER_SPEC: mmtk::vm::VMLocalForwardingPointerSpec;
-    #[cfg(feature="vmside_forwarding")]
+    /// 2-bit local metadata for spaces that store a forwarding state for objects.
+    /// If this spec is defined in the header, it can be defined with a position of the lowest 2 bits in the forwarding pointer.
+    /// If this spec is defined on the side it must be defined after the [`MARK_BIT_SPEC`](crate::object_model::MARK_BIT_SPEC).
+    #[cfg(feature = "vmside_forwarding")]
     const LOCAL_FORWARDING_BITS_SPEC: mmtk::vm::VMLocalForwardingBitsSpec;
 
-
     const ALIGNMENT_VALUE: u32 = 0xdead_beef;
     const MAX_ALIGNMENT: usize = 32;
     const MIN_ALIGNMENT: usize = 8;
@@ -164,7 +171,9 @@ pub trait VirtualMachine: Sized + 'static + Send + Sync {
     /// invocation.
     fn compute_hashcode(object: VMKitObject) -> usize {
         let _ = object;
-        unimplemented!("VM currently does not support hashcode computation, override this method to do so");
+        unimplemented!(
+            "VM currently does not support hashcode computation, override this method to do so"
+        );
     }
 }
 

vmkit/src/object_model.rs

@@ -16,55 +16,53 @@ pub mod object;
 
 pub struct VMKitObjectModel<VM: VirtualMachine>(PhantomData<VM>);
 
-/*
-pub const LOGGING_SIDE_METADATA_SPEC: VMGlobalLogBitSpec = VMGlobalLogBitSpec::side_first();
-pub const FORWARDING_POINTER_METADATA_SPEC: VMLocalForwardingPointerSpec =
-    VMLocalForwardingPointerSpec::in_header(0);
-pub const FORWARDING_BITS_METADATA_SPEC: VMLocalForwardingBitsSpec =
-    VMLocalForwardingBitsSpec::in_header(HashStateField::NEXT_BIT as _);
-pub const MARKING_METADATA_SPEC: VMLocalMarkBitSpec = VMLocalMarkBitSpec::side_first();
-pub const LOS_METADATA_SPEC: VMLocalLOSMarkNurserySpec =
-    VMLocalLOSMarkNurserySpec::in_header(HashStateField::NEXT_BIT as _);*/
-
-pub const LOGGING_SIDE_METADATA_SPEC: VMGlobalLogBitSpec = VMGlobalLogBitSpec::side_first();
-/// Overwrite first field of the object header
-pub const LOCAL_FORWARDING_POINTER_SPEC: VMLocalForwardingPointerSpec =
-    VMLocalForwardingPointerSpec::in_header(OBJECT_REF_OFFSET);
 
+/// 1-bit local metadata for spaces that need to mark an object.
+/// 
+/// Always defined on the side in VMKit.
+pub const MARK_BIT_SPEC: VMLocalMarkBitSpec = VMLocalMarkBitSpec::side_first();
 impl<VM: VirtualMachine> ObjectModel<MemoryManager<VM>> for VMKitObjectModel<VM> {
-    /*const GLOBAL_LOG_BIT_SPEC: mmtk::vm::VMGlobalLogBitSpec = LOGGING_SIDE_METADATA_SPEC;
-    const LOCAL_FORWARDING_POINTER_SPEC: mmtk::vm::VMLocalForwardingPointerSpec =
-        FORWARDING_POINTER_METADATA_SPEC;
-    const LOCAL_FORWARDING_BITS_SPEC: mmtk::vm::VMLocalForwardingBitsSpec =
-        FORWARDING_BITS_METADATA_SPEC;
-    const LOCAL_MARK_BIT_SPEC: mmtk::vm::VMLocalMarkBitSpec = MARKING_METADATA_SPEC;
-    const LOCAL_LOS_MARK_NURSERY_SPEC: mmtk::vm::VMLocalLOSMarkNurserySpec = LOS_METADATA_SPEC;*/
 
     const GLOBAL_LOG_BIT_SPEC: VMGlobalLogBitSpec = VMGlobalLogBitSpec::side_first();
 
-    #[cfg(not(feature = "vmside_forwarding"))]
+    const LOCAL_MARK_BIT_SPEC: VMLocalMarkBitSpec = MARK_BIT_SPEC;
-    const LOCAL_FORWARDING_BITS_SPEC: VMLocalForwardingBitsSpec =
+    const LOCAL_FORWARDING_BITS_SPEC: VMLocalForwardingBitsSpec = {
-        VMLocalForwardingBitsSpec::side_first();
-    #[cfg(not(feature = "vmside_forwarding"))]
-    const LOCAL_FORWARDING_POINTER_SPEC: VMLocalForwardingPointerSpec =
-        VMLocalForwardingPointerSpec::in_header(0);
-
         #[cfg(feature = "vmside_forwarding")]
-    const LOCAL_FORWARDING_BITS_SPEC: VMLocalForwardingBitsSpec = VM::LOCAL_FORWARDING_BITS_SPEC;
+        {
-    #[cfg(feature = "vmside_forwarding")]
+            VM::LOCAL_FORWARDING_BITS_SPEC
-    const LOCAL_FORWARDING_POINTER_SPEC: VMLocalForwardingPointerSpec =
+        }
-        VM::LOCAL_FORWARDING_POINTER_SPEC;
+        #[cfg(not(feature = "vmside_forwarding"))]
-    const LOCAL_MARK_BIT_SPEC: VMLocalMarkBitSpec =
+        {
-        if Self::LOCAL_FORWARDING_BITS_SPEC.as_spec().is_on_side() {
+            VMLocalForwardingBitsSpec::side_after(&MARK_BIT_SPEC.as_spec())
-            VMLocalMarkBitSpec::side_after(&Self::LOCAL_FORWARDING_BITS_SPEC.as_spec())
+        }
-        } else {
-            VMLocalMarkBitSpec::side_first()
     };
 
-    const LOCAL_LOS_MARK_NURSERY_SPEC: VMLocalLOSMarkNurserySpec =
+    const LOCAL_FORWARDING_POINTER_SPEC: VMLocalForwardingPointerSpec = {
-        VMLocalLOSMarkNurserySpec::side_after(&Self::LOCAL_MARK_BIT_SPEC.as_spec());
+        #[cfg(feature = "vmside_forwarding")]
-    const LOCAL_PINNING_BIT_SPEC: VMLocalPinningBitSpec =
+        {
-        VMLocalPinningBitSpec::side_after(&Self::LOCAL_LOS_MARK_NURSERY_SPEC.as_spec());
+            VM::LOCAL_FORWARDING_POINTER_SPEC
+        }
+        #[cfg(not(feature = "vmside_forwarding"))]
+        {
+            VMLocalForwardingPointerSpec::in_header(0)
+        }
+    };
+
+    const LOCAL_LOS_MARK_NURSERY_SPEC: VMLocalLOSMarkNurserySpec = {
+        let spec_after = if Self::LOCAL_FORWARDING_BITS_SPEC.as_spec().is_in_header() {
+            Self::LOCAL_MARK_BIT_SPEC.as_spec()
+        } else {
+            Self::LOCAL_FORWARDING_BITS_SPEC.as_spec()
+        };
+        VMLocalLOSMarkNurserySpec::side_after(&spec_after)
+    };
+
+    #[cfg(feature="object_pinning")]
+    const LOCAL_PINNING_BIT_SPEC: VMLocalPinningBitSpec = {
+        VMLocalPinningBitSpec::side_after(&Self::LOCAL_LOS_MARK_NURSERY_SPEC.as_spec())
+    };
+    
+
 
     const OBJECT_REF_OFFSET_LOWER_BOUND: isize = OBJECT_REF_OFFSET;
     const UNIFIED_OBJECT_REFERENCE_ADDRESS: bool = false;