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[CodeGen] Avoid repeated hash lookups (NFC) #128300

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Merged
merged 2 commits into from
Feb 22, 2025
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[CodeGen] Avoid repeated hash lookups (NFC) #128300

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[CodeGen] Avoid repeated hash lookups (NFC)
kazutakahirata Feb 21, 2025
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kazutakahirata Feb 22, 2025
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19 changes: 8 additions & 11 deletions llvm/lib/CodeGen/InlineSpiller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1545,24 +1545,21 @@ void HoistSpillHelper::runHoistSpills(
for (MachineDomTreeNode *Child : (*RIt)->children()) {
if (!SpillsInSubTreeMap.contains(Child))
continue;
// The stmt "SpillsInSubTree = SpillsInSubTreeMap[*RIt].first" below
// The stmt "auto &[...] = SpillsInSubTreeMap[*RIt]" below
// should be placed before getting the begin and end iterators of
// SpillsInSubTreeMap[Child].first, or else the iterators may be
// invalidated when SpillsInSubTreeMap[*RIt] is seen the first time
// and the map grows and then the original buckets in the map are moved.
SmallPtrSet<MachineDomTreeNode *, 16> &SpillsInSubTree =
SpillsInSubTreeMap[*RIt].first;
BlockFrequency &SubTreeCost = SpillsInSubTreeMap[*RIt].second;
SubTreeCost += SpillsInSubTreeMap[Child].second;
auto BI = SpillsInSubTreeMap[Child].first.begin();
auto EI = SpillsInSubTreeMap[Child].first.end();
auto &[SpillsInSubTree, SubTreeCost] = SpillsInSubTreeMap[*RIt];
auto ChildIt = SpillsInSubTreeMap.find(Child);
SubTreeCost += ChildIt->second.second;
auto BI = ChildIt->second.first.begin();
auto EI = ChildIt->second.first.end();
SpillsInSubTree.insert(BI, EI);
SpillsInSubTreeMap.erase(Child);
SpillsInSubTreeMap.erase(ChildIt);
}

SmallPtrSet<MachineDomTreeNode *, 16> &SpillsInSubTree =
SpillsInSubTreeMap[*RIt].first;
BlockFrequency &SubTreeCost = SpillsInSubTreeMap[*RIt].second;
auto &[SpillsInSubTree, SubTreeCost] = SpillsInSubTreeMap[*RIt];
// No spills in subtree, simply continue.
if (SpillsInSubTree.empty())
continue;
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