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simplify slot constant tracking

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This commit is contained in:
Niko Matsakis 2019-06-21 20:48:24 -07:00
parent 30714022fd
commit e480e08013
1 changed files with 15 additions and 35 deletions
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50
src/derived/slot.rs
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@ -71,10 +71,9 @@ where
/// Last revision when the memoized value was observed to change.
changed_at: Revision,
/// If `Some`, then this value was considered constant at the
/// given revision. If no constants have changed since then, we
/// don't need to check the inputs to see if they've changed.
constant_in_revision: Option<Revision>,
/// If true, then this value was considered a constant when last
/// verified.
is_constant: bool,
/// The inputs that went into our query, if we are tracking them.
inputs: MemoInputs<DB>,
@ -221,8 +220,7 @@ where
if let Some(old_value) = &old_memo.value {
// Careful: the "constant-ness" must also not have
// changed, see the test `constant_to_non_constant`.
let memo_was_constant = old_memo.constant_in_revision.is_some();
if memo_was_constant == result.is_constant
if old_memo.is_constant == result.is_constant
&& MP::memoized_value_eq(&old_value, &result.value)
{
debug!(
@ -249,18 +247,9 @@ where
};
debug!(
"read_upgrade({:?}): result.changed_at={:?}, result.dependencies = {:#?}",
self, result.changed_at, result.dependencies,
);
let constant_in_revision = if result.is_constant {
Some(revision_now)
} else {
None
};
debug!(
"read_upgrade({:?}): constant_in_revision={:?}",
self, constant_in_revision
"read_upgrade({:?}): result.changed_at={:?}, \
result.is_constant={:?}, result.dependencies = {:#?}",
self, result.changed_at, result.is_constant, result.dependencies,
);
let inputs = match result.dependencies {
@ -283,7 +272,7 @@ where
changed_at: result.changed_at,
verified_at: revision_now,
inputs,
constant_in_revision,
is_constant: result.is_constant,
});
panic_guard.proceed(&new_value);
@ -628,17 +617,15 @@ where
/// True if this memo should still be considered constant
/// (presuming it ever was).
fn is_still_constant(&self, db: &DB) -> bool {
if let Some(constant_at) = self.constant_in_revision {
self.is_constant && {
let last_changed = db.salsa_runtime().revision_when_constant_last_changed();
debug!(
"is_still_constant(last_changed={:?} <= constant_at={:?}) = {:?}",
"is_still_constant(last_changed={:?} <= verified_at={:?}) = {:?}",
last_changed,
constant_at,
last_changed <= constant_at,
self.verified_at,
last_changed <= self.verified_at,
);
last_changed <= constant_at
} else {
false
last_changed <= self.verified_at
}
}
@ -711,13 +698,8 @@ where
};
self.verified_at = revision_now;
let is_constant = self.constant_in_revision.is_some();
if is_constant {
self.constant_in_revision = Some(revision_now);
}
StampedValue {
is_constant,
is_constant: self.is_constant,
changed_at: self.changed_at,
value,
}
@ -733,10 +715,8 @@ where
);
if self.verified_at == revision_now {
let is_constant = self.constant_in_revision.is_some();
return Some(StampedValue {
is_constant,
is_constant: self.is_constant,
changed_at: self.changed_at,
value: value.clone(),
});