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pop AND frames when safe to do so, suspend resizing of AND frames until a proper GC is implemented (#244)

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This commit is contained in:
Mark Thom
2019-11-30 14:08:02 -07:00
parent 3e49db1a29
commit 0eb20a5d8e
4 changed files with 29 additions and 20 deletions
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7
src/prolog/machine/and_stack.rs
View File

@@ -55,6 +55,10 @@ impl AndStack {
self.0.clear()
}
/*
// See MachineState::allocate for why this is commented out.
pub fn resize(&mut self, fr: usize, n: usize) {
let len = self[fr].perms.len();
@@ -66,7 +70,8 @@ impl AndStack {
}
}
}
*/
#[inline]
pub fn truncate(&mut self, len: usize) {
self.0.truncate(len);

12
src/prolog/machine/machine_state.rs
View File

@@ -423,8 +423,6 @@ pub(crate) trait CallPolicy: Any {
machine_st.e = machine_st.or_stack[b].e;
machine_st.cp = machine_st.or_stack[b].cp.clone();
machine_st.pop_stack_frames();
machine_st.or_stack[b].bp = machine_st.p.clone() + offset;
let old_tr = machine_st.or_stack[b].tr;
@@ -471,8 +469,6 @@ pub(crate) trait CallPolicy: Any {
machine_st.e = machine_st.or_stack[b].e;
machine_st.cp = machine_st.or_stack[b].cp.clone();
machine_st.pop_stack_frames();
machine_st.or_stack[b].bp = machine_st.p.clone() + 1;
let old_tr = machine_st.or_stack[b].tr;
@@ -515,6 +511,8 @@ pub(crate) trait CallPolicy: Any {
machine_st.registers[i] = machine_st.or_stack[b][i].clone();
}
machine_st.pop_stack_frames();
machine_st.num_of_args = n;
machine_st.e = machine_st.or_stack[b].e;
machine_st.cp = machine_st.or_stack[b].cp.clone();
@@ -548,8 +546,6 @@ pub(crate) trait CallPolicy: Any {
machine_st.b = machine_st.or_stack[b].b;
machine_st.or_stack.truncate(machine_st.b);
machine_st.pop_stack_frames();
machine_st.hb = machine_st.heap.h;
machine_st.p += offset;
@@ -564,6 +560,8 @@ pub(crate) trait CallPolicy: Any {
machine_st.registers[i] = machine_st.or_stack[b][i].clone();
}
machine_st.pop_stack_frames();
machine_st.num_of_args = n;
machine_st.e = machine_st.or_stack[b].e;
machine_st.cp = machine_st.or_stack[b].cp.clone();
@@ -597,8 +595,6 @@ pub(crate) trait CallPolicy: Any {
machine_st.b = machine_st.or_stack[b].b;
machine_st.or_stack.truncate(machine_st.b);
machine_st.pop_stack_frames();
machine_st.hb = machine_st.heap.h;
machine_st.p += 1;

20
src/prolog/machine/machine_state_impl.rs
View File

@@ -123,7 +123,7 @@ impl MachineState {
self.flags
}
fn next_global_index(&self) -> usize {
pub(super) fn next_global_index(&self) -> usize {
max(
if self.and_stack.len() > 0 {
self.and_stack[self.e].global_index
@@ -3127,10 +3127,18 @@ impl MachineState {
pub(super) fn allocate(&mut self, num_cells: usize) {
let gi = self.next_global_index();
// let new_e = self.e + 1;
self.p += 1;
if self.e + 1 < self.and_stack.len() {
/*
/* See issue #244 for an example of a program broken (at the
top level) by the inclusion of this code. A proper GC must determine if an
existing AND frame is safe to resize; the check here is not
enough.
*/
if new_e < self.and_stack.len() {
let and_gi = self.and_stack[self.e].global_index;
let or_gi = self
.or_stack
@@ -3139,10 +3147,8 @@ impl MachineState {
.unwrap_or(0);
if and_gi > or_gi {
let new_e = self.e + 1;
self.and_stack[new_e].e = self.e;
self.and_stack[new_e].cp = self.cp.clone();
self.and_stack[new_e].cp = self.cp;
self.and_stack[new_e].global_index = gi;
self.and_stack.resize(new_e, num_cells);
@@ -3151,7 +3157,7 @@ impl MachineState {
return;
}
}
*/
self.and_stack.push(gi, self.e, self.cp.clone(), num_cells);
self.e = self.and_stack.len() - 1;
}
@@ -3353,7 +3359,7 @@ impl MachineState {
self.b = self.or_stack.len();
let b = self.b - 1;
for i in 1..n + 1 {
for i in 1 .. n + 1 {
self.or_stack[b][i] = self.registers[i].clone();
}