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Handle conflict-related liverange splits arising from stack constraints without falling back to spill bundle. #49

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Merged
cfallin merged 2 commits into from
May 17, 2022
Merged

Handle conflict-related liverange splits arising from stack constraints without falling back to spill bundle. #49

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11f6855
Handle conflict-related liverange splits arising from stack constrain…
cfallin May 17, 2022
5fdb172
Inline-always pragmas needed to avoid slight regression in regalloc t…
cfallin May 17, 2022
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291 changes: 150 additions & 141 deletions src/ion/process.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,12 +18,9 @@ use super::{
Requirement, SpillWeight, UseList,
};
use crate::{
ion::{
data_structures::{
CodeRange, BUNDLE_MAX_NORMAL_SPILL_WEIGHT, MINIMAL_BUNDLE_SPILL_WEIGHT,
MINIMAL_FIXED_BUNDLE_SPILL_WEIGHT,
},
requirement::RequirementConflictAt,
ion::data_structures::{
CodeRange, BUNDLE_MAX_NORMAL_SPILL_WEIGHT, MINIMAL_BUNDLE_SPILL_WEIGHT,
MINIMAL_FIXED_BUNDLE_SPILL_WEIGHT,
},
Allocation, Function, Inst, InstPosition, OperandConstraint, OperandKind, PReg, ProgPoint,
RegAllocError,
Expand Down Expand Up @@ -395,6 +392,9 @@ impl<'a, F: Function> Env<'a, F> {
bundle: LiveBundleIndex,
mut split_at: ProgPoint,
reg_hint: PReg,
// Do we trim the parts around the split and put them in the
// spill bundle?
trim_ends_into_spill_bundle: bool,
) {
self.stats.splits += 1;
trace!(
Expand Down Expand Up @@ -567,149 +567,151 @@ impl<'a, F: Function> Env<'a, F> {
}
self.bundles[new_bundle.index()].ranges = new_lr_list;

// Finally, handle moving LRs to the spill bundle when
// appropriate: If the first range in `new_bundle` or last
// range in `bundle` has "empty space" beyond the first or
// last use (respectively), trim it and put an empty LR into
// the spill bundle. (We are careful to treat the "starts at
// def" flag as an implicit first def even if no def-type Use
// is present.)
while let Some(entry) = self.bundles[bundle.index()].ranges.last().cloned() {
let end = entry.range.to;
let vreg = self.ranges[entry.index.index()].vreg;
let last_use = self.ranges[entry.index.index()].uses.last().map(|u| u.pos);
if last_use.is_none() {
let spill = self
.get_or_create_spill_bundle(bundle, /* create_if_absent = */ true)
.unwrap();
trace!(
" -> bundle {:?} range {:?}: no uses; moving to spill bundle {:?}",
bundle,
entry.index,
spill
);
self.bundles[spill.index()].ranges.push(entry);
self.bundles[bundle.index()].ranges.pop();
self.ranges[entry.index.index()].bundle = spill;
continue;
}
let last_use = last_use.unwrap();
let split = ProgPoint::before(last_use.inst().next());
if split < end {
let spill = self
.get_or_create_spill_bundle(bundle, /* create_if_absent = */ true)
.unwrap();
self.bundles[bundle.index()]
.ranges
.last_mut()
.unwrap()
if trim_ends_into_spill_bundle {
// Finally, handle moving LRs to the spill bundle when
// appropriate: If the first range in `new_bundle` or last
// range in `bundle` has "empty space" beyond the first or
// last use (respectively), trim it and put an empty LR into
// the spill bundle. (We are careful to treat the "starts at
// def" flag as an implicit first def even if no def-type Use
// is present.)
while let Some(entry) = self.bundles[bundle.index()].ranges.last().cloned() {
let end = entry.range.to;
let vreg = self.ranges[entry.index.index()].vreg;
let last_use = self.ranges[entry.index.index()].uses.last().map(|u| u.pos);
if last_use.is_none() {
let spill = self
.get_or_create_spill_bundle(bundle, /* create_if_absent = */ true)
.unwrap();
trace!(
" -> bundle {:?} range {:?}: no uses; moving to spill bundle {:?}",
bundle,
entry.index,
spill
);
self.bundles[spill.index()].ranges.push(entry);
self.bundles[bundle.index()].ranges.pop();
self.ranges[entry.index.index()].bundle = spill;
continue;
}
let last_use = last_use.unwrap();
let split = ProgPoint::before(last_use.inst().next());
if split < end {
let spill = self
.get_or_create_spill_bundle(bundle, /* create_if_absent = */ true)
.unwrap();
self.bundles[bundle.index()]
.ranges
.last_mut()
.unwrap()
.range
.to = split;
self.ranges[self.bundles[bundle.index()]
.ranges
.last()
.unwrap()
.index
.index()]
.range
.to = split;
self.ranges[self.bundles[bundle.index()]
.ranges
.last()
.unwrap()
.index
.index()]
.range
.to = split;
let range = CodeRange {
from: split,
to: end,
};
let empty_lr = self.create_liverange(range);
self.bundles[spill.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
self.ranges[empty_lr.index()].bundle = spill;
self.vregs[vreg.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
trace!(
" -> bundle {:?} range {:?}: last use implies split point {:?}",
bundle,
entry.index,
split
);
trace!(
let range = CodeRange {
from: split,
to: end,
};
let empty_lr = self.create_liverange(range);
self.bundles[spill.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
self.ranges[empty_lr.index()].bundle = spill;
self.vregs[vreg.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
trace!(
" -> bundle {:?} range {:?}: last use implies split point {:?}",
bundle,
entry.index,
split
);
trace!(
" -> moving trailing empty region to new spill bundle {:?} with new LR {:?}",
spill,
empty_lr
);
}
break;
}
while let Some(entry) = self.bundles[new_bundle.index()].ranges.first().cloned() {
if self.ranges[entry.index.index()].has_flag(LiveRangeFlag::StartsAtDef) {
}
break;
}
let start = entry.range.from;
let vreg = self.ranges[entry.index.index()].vreg;
let first_use = self.ranges[entry.index.index()].uses.first().map(|u| u.pos);
if first_use.is_none() {
let spill = self
.get_or_create_spill_bundle(new_bundle, /* create_if_absent = */ true)
.unwrap();
trace!(
" -> bundle {:?} range {:?}: no uses; moving to spill bundle {:?}",
new_bundle,
entry.index,
spill
);
self.bundles[spill.index()].ranges.push(entry);
self.bundles[new_bundle.index()].ranges.drain(..1);
self.ranges[entry.index.index()].bundle = spill;
continue;
}
let first_use = first_use.unwrap();
let split = ProgPoint::before(first_use.inst());
if split > start {
let spill = self
.get_or_create_spill_bundle(new_bundle, /* create_if_absent = */ true)
.unwrap();
self.bundles[new_bundle.index()]
.ranges
.first_mut()
.unwrap()
while let Some(entry) = self.bundles[new_bundle.index()].ranges.first().cloned() {
if self.ranges[entry.index.index()].has_flag(LiveRangeFlag::StartsAtDef) {
break;
}
let start = entry.range.from;
let vreg = self.ranges[entry.index.index()].vreg;
let first_use = self.ranges[entry.index.index()].uses.first().map(|u| u.pos);
if first_use.is_none() {
let spill = self
.get_or_create_spill_bundle(new_bundle, /* create_if_absent = */ true)
.unwrap();
trace!(
" -> bundle {:?} range {:?}: no uses; moving to spill bundle {:?}",
new_bundle,
entry.index,
spill
);
self.bundles[spill.index()].ranges.push(entry);
self.bundles[new_bundle.index()].ranges.drain(..1);
self.ranges[entry.index.index()].bundle = spill;
continue;
}
let first_use = first_use.unwrap();
let split = ProgPoint::before(first_use.inst());
if split > start {
let spill = self
.get_or_create_spill_bundle(new_bundle, /* create_if_absent = */ true)
.unwrap();
self.bundles[new_bundle.index()]
.ranges
.first_mut()
.unwrap()
.range
.from = split;
self.ranges[self.bundles[new_bundle.index()]
.ranges
.first()
.unwrap()
.index
.index()]
.range
.from = split;
self.ranges[self.bundles[new_bundle.index()]
.ranges
.first()
.unwrap()
.index
.index()]
.range
.from = split;
let range = CodeRange {
from: start,
to: split,
};
let empty_lr = self.create_liverange(range);
self.bundles[spill.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
self.ranges[empty_lr.index()].bundle = spill;
self.vregs[vreg.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
trace!(
" -> bundle {:?} range {:?}: first use implies split point {:?}",
bundle,
entry.index,
first_use,
);
trace!(
" -> moving leading empty region to new spill bundle {:?} with new LR {:?}",
spill,
empty_lr
);
let range = CodeRange {
from: start,
to: split,
};
let empty_lr = self.create_liverange(range);
self.bundles[spill.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
self.ranges[empty_lr.index()].bundle = spill;
self.vregs[vreg.index()].ranges.push(LiveRangeListEntry {
range,
index: empty_lr,
});
trace!(
" -> bundle {:?} range {:?}: first use implies split point {:?}",
bundle,
entry.index,
first_use,
);
trace!(
" -> moving leading empty region to new spill bundle {:?} with new LR {:?}",
spill,
empty_lr
);
}
break;
}
break;
}

if self.bundles[bundle.index()].ranges.len() > 0 {
Expand Down Expand Up @@ -745,7 +747,7 @@ impl<'a, F: Function> Env<'a, F> {

let req = match self.compute_requirement(bundle) {
Ok(req) => req,
Err(RequirementConflictAt(split_point)) => {
Err(conflict) => {
// We have to split right away. We'll find a point to
// split that would allow at least the first half of the
// split to be conflict-free.
Expand All @@ -755,8 +757,10 @@ impl<'a, F: Function> Env<'a, F> {
);
self.split_and_requeue_bundle(
bundle,
/* split_at_point = */ split_point,
/* split_at_point = */ conflict.suggested_split_point(),
reg_hint,
/* trim_ends_into_spill_bundle = */
conflict.should_trim_edges_around_split(),
);
return Ok(());
}
Expand Down Expand Up @@ -1047,7 +1051,12 @@ impl<'a, F: Function> Env<'a, F> {
}
}

self.split_and_requeue_bundle(bundle, split_at_point, requeue_with_reg);
self.split_and_requeue_bundle(
bundle,
split_at_point,
requeue_with_reg,
/* should_trim = */ true,
);
return Ok(());
} else {
// Evict all bundles in `conflicting bundles` and try again.
Expand Down
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