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[ADT] Skip DenseMapBase::destroyAll on trivially destructible types #165080

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Merged
merged 1 commit into from
Oct 25, 2025
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[ADT] Skip DenseMapBase::destroyAll on trivially destructible types #165080

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6 changes: 6 additions & 0 deletions llvm/include/llvm/ADT/DenseMap.h
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Original file line number Diff line number Diff line change
Expand Up @@ -353,6 +353,12 @@ class DenseMapBase : public DebugEpochBase {
DenseMapBase() = default;

void destroyAll() {
// No need to iterate through the buckets if both KeyT and ValueT are
// trivially destructible.
if constexpr (std::is_trivially_destructible_v<KeyT> &&
std::is_trivially_destructible_v<ValueT>)
return;

if (getNumBuckets() == 0) // Nothing to do.
return;

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70 changes: 70 additions & 0 deletions llvm/unittests/ADT/DenseMapTest.cpp
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Expand Up @@ -70,6 +70,16 @@ class CtorTester {

int getValue() const { return Value; }
bool operator==(const CtorTester &RHS) const { return Value == RHS.Value; }

// Return the number of live CtorTester objects, excluding the empty and
// tombstone keys.
static size_t getNumConstructed() {
return std::count_if(Constructed.begin(), Constructed.end(),
[](const CtorTester *Obj) {
int V = Obj->getValue();
return V != -1 && V != -2;
});
}
};

std::set<CtorTester *> CtorTester::Constructed;
Expand Down Expand Up @@ -1031,4 +1041,64 @@ TEST(SmallDenseMapCustomTest, InitSize) {
}
}

TEST(DenseMapCustomTest, KeyDtor) {
// This test relies on CtorTester being non-trivially destructible.
static_assert(!std::is_trivially_destructible_v<CtorTester>,
"CtorTester must not be trivially destructible");

// Test that keys are destructed on scope exit.
EXPECT_EQ(0u, CtorTester::getNumConstructed());
{
DenseMap<CtorTester, int, CtorTesterMapInfo> Map;
Map.try_emplace(CtorTester(0), 1);
Map.try_emplace(CtorTester(1), 2);
EXPECT_EQ(2u, CtorTester::getNumConstructed());
}
EXPECT_EQ(0u, CtorTester::getNumConstructed());

// Test that keys are destructed on erase and shrink_and_clear.
EXPECT_EQ(0u, CtorTester::getNumConstructed());
{
DenseMap<CtorTester, int, CtorTesterMapInfo> Map;
Map.try_emplace(CtorTester(0), 1);
Map.try_emplace(CtorTester(1), 2);
EXPECT_EQ(2u, CtorTester::getNumConstructed());
Map.erase(CtorTester(1));
EXPECT_EQ(1u, CtorTester::getNumConstructed());
Map.shrink_and_clear();
EXPECT_EQ(0u, CtorTester::getNumConstructed());
}
EXPECT_EQ(0u, CtorTester::getNumConstructed());
}

TEST(DenseMapCustomTest, ValueDtor) {
// This test relies on CtorTester being non-trivially destructible.
static_assert(!std::is_trivially_destructible_v<CtorTester>,
"CtorTester must not be trivially destructible");

// Test that values are destructed on scope exit.
EXPECT_EQ(0u, CtorTester::getNumConstructed());
{
DenseMap<int, CtorTester> Map;
Map.try_emplace(0, CtorTester(1));
Map.try_emplace(1, CtorTester(2));
EXPECT_EQ(2u, CtorTester::getNumConstructed());
}
EXPECT_EQ(0u, CtorTester::getNumConstructed());

// Test that values are destructed on erase and shrink_and_clear.
EXPECT_EQ(0u, CtorTester::getNumConstructed());
{
DenseMap<int, CtorTester> Map;
Map.try_emplace(0, CtorTester(1));
Map.try_emplace(1, CtorTester(2));
EXPECT_EQ(2u, CtorTester::getNumConstructed());
Map.erase(1);
EXPECT_EQ(1u, CtorTester::getNumConstructed());
Map.shrink_and_clear();
EXPECT_EQ(0u, CtorTester::getNumConstructed());
}
EXPECT_EQ(0u, CtorTester::getNumConstructed());
}

} // namespace