Do not process slots and copy state for payload attributes post Fulu (#16168)

When computing payload attributes post-Fulu, we do not need to process
slots, nor copy the state if we need to find out if the node is
proposing in the next slot. This prevents an immediate epoch processing
after block 31 is processed unless we are actually proposing.

beacon-chain/blockchain/execution_engine.go

@@ -323,14 +323,17 @@ func (s *Service) getPayloadAttribute(ctx context.Context, st state.BeaconState,
 	var ok bool
 	e := slots.ToEpoch(slot)
 	stateEpoch := slots.ToEpoch(st.Slot())
-	if e == stateEpoch {
+	fuluAndNextEpoch := st.Version() >= version.Fulu && e == stateEpoch+1
+	if e == stateEpoch || fuluAndNextEpoch {
 		val, ok = s.trackedProposer(st, slot)
 		if !ok {
 			return emptyAttri
 		}
 	}
-	st = st.Copy()
 	if slot > st.Slot() {
+		// At this point either we know we are proposing on a future slot or we need to still compute the
+		// right proposer index pre-Fulu, either way we need to copy the state to process it.
+		st = st.Copy()
 		var err error
 		st, err = transition.ProcessSlotsUsingNextSlotCache(ctx, st, headRoot, slot)
 		if err != nil {
@@ -338,7 +341,7 @@ func (s *Service) getPayloadAttribute(ctx context.Context, st state.BeaconState,
 			return emptyAttri
 		}
 	}
-	if e > stateEpoch {
+	if e > stateEpoch && !fuluAndNextEpoch {
 		emptyAttri := payloadattribute.EmptyWithVersion(st.Version())
 		val, ok = s.trackedProposer(st, slot)
 		if !ok {

changelog/potuz_next_epoch_attributes.md

@@ -0,0 +1,3 @@
+### Fixed
+
+- Do not process slots and copy states for next epoch proposers after Fulu