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add backward looking cyclicity check for variables in cycle detecting stackless iterator (#2111, #2117)

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Mark
2023-10-15 13:07:41 -06:00
parent 3a6aee72a3
commit e2000859b6
2 changed files with 33 additions and 8 deletions
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27
src/machine/gc.rs
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@@ -12,12 +12,15 @@ pub(crate) trait UnmarkPolicy {
fn invert_marker(iter: &mut StacklessPreOrderHeapIter<Self>) where Self: Sized;
fn cycle_detected(&mut self) where Self: Sized;
fn mark_phase(&self) -> bool;
fn var_rooted_cycle(_iter: &mut StacklessPreOrderHeapIter<Self>, _var_loc: usize, _next: usize)
where
Self: Sized {}
fn detect_list_tail_cycle(_iter: &mut StacklessPreOrderHeapIter<Self>) where Self: Sized {}
fn list_head_cycle_detecting_backward(
iter: &mut StacklessPreOrderHeapIter<Self>,
) -> bool where Self: Sized {
iter.backward()
}
fn detect_list_tail_cycle(_iter: &mut StacklessPreOrderHeapIter<Self>) where Self: Sized {}
}
pub(crate) struct IteratorUMP {
@@ -89,7 +92,7 @@ impl UnmarkPolicy for CycleDetectorUMP {
iter: &mut StacklessPreOrderHeapIter<Self>,
) -> bool {
if !iter.iter_state.cycle_detected && iter.iter_state.mark_phase {
iter.iter_state.cycle_detected = iter.detect_list_cycle();
iter.iter_state.cycle_detected = iter.detect_list_cycle(iter.current);
}
iter.backward()
@@ -97,7 +100,13 @@ impl UnmarkPolicy for CycleDetectorUMP {
fn detect_list_tail_cycle(iter: &mut StacklessPreOrderHeapIter<Self>) {
if iter.iter_state.mark_phase && !iter.iter_state.cycle_detected {
iter.iter_state.cycle_detected = iter.detect_list_cycle();
iter.iter_state.cycle_detected = iter.detect_list_cycle(iter.current);
}
}
fn var_rooted_cycle(iter: &mut StacklessPreOrderHeapIter<Self>, var_loc: usize, next: usize) {
if var_loc != next && iter.iter_state.mark_phase && !iter.iter_state.cycle_detected {
iter.iter_state.cycle_detected = iter.detect_list_cycle(next);
}
}
}
@@ -200,7 +209,7 @@ impl<'a> StacklessPreOrderHeapIter<'a, CycleDetectorUMP> {
self.iter_state.cycle_detected
}
pub(crate) fn detect_list_cycle(&self) -> bool {
pub(crate) fn detect_list_cycle(&self, next: usize) -> bool {
use crate::machine::system_calls::BrentAlgState;
let mut brent_alg_st = BrentAlgState::new(self.current);
@@ -208,12 +217,12 @@ impl<'a> StacklessPreOrderHeapIter<'a, CycleDetectorUMP> {
while self.heap[brent_alg_st.hare].get_mark_bit() {
let temp = self.heap[brent_alg_st.hare].get_value() as usize;
if brent_alg_st.step(temp).is_some() || temp == self.current {
if brent_alg_st.step(temp).is_some() || temp == next {
return true;
}
if temp == self.start {
return self.heap[temp].get_value() == self.current as u64;
break;
}
}
@@ -272,7 +281,7 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
#[inline]
fn is_cyclic(&self, var_current: usize, var_next: usize) -> bool {
if self.heap[var_next].is_var() {
!self.heap[var_next].get_forwarding_bit() && var_current != var_next
self.heap[var_next].get_mark_bit() && var_current != var_next
} else if self.heap[var_next].is_ref() {
self.heap[var_next].get_mark_bit()
} else {
@@ -296,6 +305,8 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
}
return Some(cell);
} else if self.heap[next as usize].get_mark_bit() == self.iter_state.mark_phase() {
UMP::var_rooted_cycle(self, current, next as usize);
}
if self.next < self.heap.len() as u64 {
@@ -315,6 +326,8 @@ impl<'a, UMP: UnmarkPolicy> StacklessPreOrderHeapIter<'a, UMP> {
}
return Some(cell);
} else if self.heap[next as usize].get_mark_bit() == self.iter_state.mark_phase() {
UMP::var_rooted_cycle(self, current, next as usize);
}
if self.next < self.heap.len() as u64 {