Optimize loan propagation by separating persistent and block-local origins #165789
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@llvm/pr-subscribers-clang-temporal-safety Author: Utkarsh Saxena (usx95) ChangesSummaryOptimizes the lifetime analysis loan propagation by preventing block-local origins from participating in expensive join operations at block boundaries. ProblemThe lifetime analysis currently performs join operations on all origins at every block boundary. However, many origins are block-local: they exist only to propagate loans between persistent origins across temporary declarations within a single block. Including them in joins is unnecessary and expensive. SolutionThis PR classifies origins into two categories:
Implementation
Benefits
Fixes #165780 Full diff: https://github.com/llvm/llvm-project/pull/165789.diff 2 Files Affected:
diff --git a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
index 387097e705f94..3ee48facfeb57 100644
--- a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
@@ -7,10 +7,60 @@
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/LifetimeSafety/LoanPropagation.h"
#include "Dataflow.h"
+#include "llvm/Support/TimeProfiler.h"
#include <memory>
namespace clang::lifetimes::internal {
+
+// Pre-pass to find persistent origins. An origin is persistent if it is
+// referenced in more than one basic block.
+static llvm::DenseSet<OriginID> computePersistentOrigins(FactManager &FactMgr,
+ const CFG &C) {
+ llvm::TimeTraceScope("ComputePersistentOrigins");
+ llvm::DenseSet<OriginID> PersistentOrigins;
+
+ llvm::DenseMap<OriginID, const CFGBlock *> OriginToBlock;
+ for (const CFGBlock *B : C) {
+ for (const Fact *F : FactMgr.getFacts(B)) {
+ auto CheckOrigin = [&](OriginID OID) {
+ if (PersistentOrigins.count(OID))
+ return;
+ auto It = OriginToBlock.find(OID);
+ if (It == OriginToBlock.end()) {
+ OriginToBlock[OID] = B;
+ } else if (It->second != B) {
+ // We saw this origin in more than one block.
+ PersistentOrigins.insert(OID);
+ }
+ };
+
+ switch (F->getKind()) {
+ case Fact::Kind::Issue:
+ CheckOrigin(F->getAs<IssueFact>()->getOriginID());
+ break;
+ case Fact::Kind::OriginFlow: {
+ const auto *OF = F->getAs<OriginFlowFact>();
+ CheckOrigin(OF->getDestOriginID());
+ CheckOrigin(OF->getSrcOriginID());
+ break;
+ }
+ case Fact::Kind::ReturnOfOrigin:
+ CheckOrigin(F->getAs<ReturnOfOriginFact>()->getReturnedOriginID());
+ break;
+ case Fact::Kind::Use:
+ CheckOrigin(F->getAs<UseFact>()->getUsedOrigin(FactMgr.getOriginMgr()));
+ break;
+ case Fact::Kind::Expire:
+ case Fact::Kind::TestPoint:
+ break;
+ }
+ }
+ }
+ return PersistentOrigins;
+}
+
namespace {
+
/// Represents the dataflow lattice for loan propagation.
///
/// This lattice tracks which loans each origin may hold at a given program
@@ -20,21 +70,35 @@ namespace {
/// not expressions, because expressions are not visible across blocks.
struct Lattice {
/// The map from an origin to the set of loans it contains.
- OriginLoanMap Origins = OriginLoanMap(nullptr);
+ OriginLoanMap PersistentOrigins = OriginLoanMap(nullptr);
+ OriginLoanMap BlockLocalOrigins = OriginLoanMap(nullptr);
- explicit Lattice(const OriginLoanMap &S) : Origins(S) {}
+ explicit Lattice(const OriginLoanMap &Persistent,
+ const OriginLoanMap &BlockLocal)
+ : PersistentOrigins(Persistent), BlockLocalOrigins(BlockLocal) {}
Lattice() = default;
bool operator==(const Lattice &Other) const {
- return Origins == Other.Origins;
+ return PersistentOrigins == Other.PersistentOrigins &&
+ BlockLocalOrigins == Other.BlockLocalOrigins;
}
bool operator!=(const Lattice &Other) const { return !(*this == Other); }
void dump(llvm::raw_ostream &OS) const {
OS << "LoanPropagationLattice State:\n";
- if (Origins.isEmpty())
+ OS << " Persistent Origins:\n";
+ if (PersistentOrigins.isEmpty())
OS << " <empty>\n";
- for (const auto &Entry : Origins) {
+ for (const auto &Entry : PersistentOrigins) {
+ if (Entry.second.isEmpty())
+ OS << " Origin " << Entry.first << " contains no loans\n";
+ for (const LoanID &LID : Entry.second)
+ OS << " Origin " << Entry.first << " contains Loan " << LID << "\n";
+ }
+ OS << " Block-Local Origins:\n";
+ if (BlockLocalOrigins.isEmpty())
+ OS << " <empty>\n";
+ for (const auto &Entry : BlockLocalOrigins) {
if (Entry.second.isEmpty())
OS << " Origin " << Entry.first << " contains no loans\n";
for (const LoanID &LID : Entry.second)
@@ -50,7 +114,8 @@ class AnalysisImpl
OriginLoanMap::Factory &OriginLoanMapFactory,
LoanSet::Factory &LoanSetFactory)
: DataflowAnalysis(C, AC, F), OriginLoanMapFactory(OriginLoanMapFactory),
- LoanSetFactory(LoanSetFactory) {}
+ LoanSetFactory(LoanSetFactory),
+ PersistentOrigins(computePersistentOrigins(F, C)) {}
using Base::transfer;
@@ -59,10 +124,9 @@ class AnalysisImpl
Lattice getInitialState() { return Lattice{}; }
/// Merges two lattices by taking the union of loans for each origin.
- // TODO(opt): Keep the state small by removing origins which become dead.
Lattice join(Lattice A, Lattice B) {
OriginLoanMap JoinedOrigins = utils::join(
- A.Origins, B.Origins, OriginLoanMapFactory,
+ A.PersistentOrigins, B.PersistentOrigins, OriginLoanMapFactory,
[&](const LoanSet *S1, const LoanSet *S2) {
assert((S1 || S2) && "unexpectedly merging 2 empty sets");
if (!S1)
@@ -74,16 +138,15 @@ class AnalysisImpl
// Asymmetric join is a performance win. For origins present only on one
// branch, the loan set can be carried over as-is.
utils::JoinKind::Asymmetric);
- return Lattice(JoinedOrigins);
+ return Lattice(JoinedOrigins, OriginLoanMapFactory.getEmptyMap());
}
/// A new loan is issued to the origin. Old loans are erased.
Lattice transfer(Lattice In, const IssueFact &F) {
OriginID OID = F.getOriginID();
LoanID LID = F.getLoanID();
- return Lattice(OriginLoanMapFactory.add(
- In.Origins, OID,
- LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID)));
+ LoanSet NewLoans = LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID);
+ return setLoans(In, OID, NewLoans);
}
/// A flow from source to destination. If `KillDest` is true, this replaces
@@ -98,7 +161,7 @@ class AnalysisImpl
LoanSet SrcLoans = getLoans(In, SrcOID);
LoanSet MergedLoans = utils::join(DestLoans, SrcLoans, LoanSetFactory);
- return Lattice(OriginLoanMapFactory.add(In.Origins, DestOID, MergedLoans));
+ return setLoans(In, DestOID, MergedLoans);
}
LoanSet getLoans(OriginID OID, ProgramPoint P) const {
@@ -106,14 +169,30 @@ class AnalysisImpl
}
private:
+ bool isPersistent(OriginID OID) const {
+ return PersistentOrigins.contains(OID);
+ }
+
+ Lattice setLoans(Lattice L, OriginID OID, LoanSet Loans) {
+ if (isPersistent(OID)) {
+ return Lattice(OriginLoanMapFactory.add(L.PersistentOrigins, OID, Loans),
+ L.BlockLocalOrigins);
+ }
+ return Lattice(L.PersistentOrigins,
+ OriginLoanMapFactory.add(L.BlockLocalOrigins, OID, Loans));
+ }
+
LoanSet getLoans(Lattice L, OriginID OID) const {
- if (auto *Loans = L.Origins.lookup(OID))
+ const OriginLoanMap *Map =
+ isPersistent(OID) ? &L.PersistentOrigins : &L.BlockLocalOrigins;
+ if (auto *Loans = Map->lookup(OID))
return *Loans;
return LoanSetFactory.getEmptySet();
}
OriginLoanMap::Factory &OriginLoanMapFactory;
LoanSet::Factory &LoanSetFactory;
+ llvm::DenseSet<OriginID> PersistentOrigins;
};
} // namespace
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index 0c051847f4d47..40205b9a8fd19 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -543,7 +543,6 @@ TEST_F(LifetimeAnalysisTest, PointersInACycle) {
EXPECT_THAT(Origin("p1"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p2"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p3"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
- EXPECT_THAT(Origin("temp"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
}
TEST_F(LifetimeAnalysisTest, PointersAndExpirationInACycle) {
|
|
@llvm/pr-subscribers-clang-analysis Author: Utkarsh Saxena (usx95) ChangesSummaryOptimizes the lifetime analysis loan propagation by preventing block-local origins from participating in expensive join operations at block boundaries. ProblemThe lifetime analysis currently performs join operations on all origins at every block boundary. However, many origins are block-local: they exist only to propagate loans between persistent origins across temporary declarations within a single block. Including them in joins is unnecessary and expensive. SolutionThis PR classifies origins into two categories:
Implementation
Benefits
Fixes #165780 Full diff: https://github.com/llvm/llvm-project/pull/165789.diff 2 Files Affected:
diff --git a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
index 387097e705f94..3ee48facfeb57 100644
--- a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
@@ -7,10 +7,60 @@
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/LifetimeSafety/LoanPropagation.h"
#include "Dataflow.h"
+#include "llvm/Support/TimeProfiler.h"
#include <memory>
namespace clang::lifetimes::internal {
+
+// Pre-pass to find persistent origins. An origin is persistent if it is
+// referenced in more than one basic block.
+static llvm::DenseSet<OriginID> computePersistentOrigins(FactManager &FactMgr,
+ const CFG &C) {
+ llvm::TimeTraceScope("ComputePersistentOrigins");
+ llvm::DenseSet<OriginID> PersistentOrigins;
+
+ llvm::DenseMap<OriginID, const CFGBlock *> OriginToBlock;
+ for (const CFGBlock *B : C) {
+ for (const Fact *F : FactMgr.getFacts(B)) {
+ auto CheckOrigin = [&](OriginID OID) {
+ if (PersistentOrigins.count(OID))
+ return;
+ auto It = OriginToBlock.find(OID);
+ if (It == OriginToBlock.end()) {
+ OriginToBlock[OID] = B;
+ } else if (It->second != B) {
+ // We saw this origin in more than one block.
+ PersistentOrigins.insert(OID);
+ }
+ };
+
+ switch (F->getKind()) {
+ case Fact::Kind::Issue:
+ CheckOrigin(F->getAs<IssueFact>()->getOriginID());
+ break;
+ case Fact::Kind::OriginFlow: {
+ const auto *OF = F->getAs<OriginFlowFact>();
+ CheckOrigin(OF->getDestOriginID());
+ CheckOrigin(OF->getSrcOriginID());
+ break;
+ }
+ case Fact::Kind::ReturnOfOrigin:
+ CheckOrigin(F->getAs<ReturnOfOriginFact>()->getReturnedOriginID());
+ break;
+ case Fact::Kind::Use:
+ CheckOrigin(F->getAs<UseFact>()->getUsedOrigin(FactMgr.getOriginMgr()));
+ break;
+ case Fact::Kind::Expire:
+ case Fact::Kind::TestPoint:
+ break;
+ }
+ }
+ }
+ return PersistentOrigins;
+}
+
namespace {
+
/// Represents the dataflow lattice for loan propagation.
///
/// This lattice tracks which loans each origin may hold at a given program
@@ -20,21 +70,35 @@ namespace {
/// not expressions, because expressions are not visible across blocks.
struct Lattice {
/// The map from an origin to the set of loans it contains.
- OriginLoanMap Origins = OriginLoanMap(nullptr);
+ OriginLoanMap PersistentOrigins = OriginLoanMap(nullptr);
+ OriginLoanMap BlockLocalOrigins = OriginLoanMap(nullptr);
- explicit Lattice(const OriginLoanMap &S) : Origins(S) {}
+ explicit Lattice(const OriginLoanMap &Persistent,
+ const OriginLoanMap &BlockLocal)
+ : PersistentOrigins(Persistent), BlockLocalOrigins(BlockLocal) {}
Lattice() = default;
bool operator==(const Lattice &Other) const {
- return Origins == Other.Origins;
+ return PersistentOrigins == Other.PersistentOrigins &&
+ BlockLocalOrigins == Other.BlockLocalOrigins;
}
bool operator!=(const Lattice &Other) const { return !(*this == Other); }
void dump(llvm::raw_ostream &OS) const {
OS << "LoanPropagationLattice State:\n";
- if (Origins.isEmpty())
+ OS << " Persistent Origins:\n";
+ if (PersistentOrigins.isEmpty())
OS << " <empty>\n";
- for (const auto &Entry : Origins) {
+ for (const auto &Entry : PersistentOrigins) {
+ if (Entry.second.isEmpty())
+ OS << " Origin " << Entry.first << " contains no loans\n";
+ for (const LoanID &LID : Entry.second)
+ OS << " Origin " << Entry.first << " contains Loan " << LID << "\n";
+ }
+ OS << " Block-Local Origins:\n";
+ if (BlockLocalOrigins.isEmpty())
+ OS << " <empty>\n";
+ for (const auto &Entry : BlockLocalOrigins) {
if (Entry.second.isEmpty())
OS << " Origin " << Entry.first << " contains no loans\n";
for (const LoanID &LID : Entry.second)
@@ -50,7 +114,8 @@ class AnalysisImpl
OriginLoanMap::Factory &OriginLoanMapFactory,
LoanSet::Factory &LoanSetFactory)
: DataflowAnalysis(C, AC, F), OriginLoanMapFactory(OriginLoanMapFactory),
- LoanSetFactory(LoanSetFactory) {}
+ LoanSetFactory(LoanSetFactory),
+ PersistentOrigins(computePersistentOrigins(F, C)) {}
using Base::transfer;
@@ -59,10 +124,9 @@ class AnalysisImpl
Lattice getInitialState() { return Lattice{}; }
/// Merges two lattices by taking the union of loans for each origin.
- // TODO(opt): Keep the state small by removing origins which become dead.
Lattice join(Lattice A, Lattice B) {
OriginLoanMap JoinedOrigins = utils::join(
- A.Origins, B.Origins, OriginLoanMapFactory,
+ A.PersistentOrigins, B.PersistentOrigins, OriginLoanMapFactory,
[&](const LoanSet *S1, const LoanSet *S2) {
assert((S1 || S2) && "unexpectedly merging 2 empty sets");
if (!S1)
@@ -74,16 +138,15 @@ class AnalysisImpl
// Asymmetric join is a performance win. For origins present only on one
// branch, the loan set can be carried over as-is.
utils::JoinKind::Asymmetric);
- return Lattice(JoinedOrigins);
+ return Lattice(JoinedOrigins, OriginLoanMapFactory.getEmptyMap());
}
/// A new loan is issued to the origin. Old loans are erased.
Lattice transfer(Lattice In, const IssueFact &F) {
OriginID OID = F.getOriginID();
LoanID LID = F.getLoanID();
- return Lattice(OriginLoanMapFactory.add(
- In.Origins, OID,
- LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID)));
+ LoanSet NewLoans = LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID);
+ return setLoans(In, OID, NewLoans);
}
/// A flow from source to destination. If `KillDest` is true, this replaces
@@ -98,7 +161,7 @@ class AnalysisImpl
LoanSet SrcLoans = getLoans(In, SrcOID);
LoanSet MergedLoans = utils::join(DestLoans, SrcLoans, LoanSetFactory);
- return Lattice(OriginLoanMapFactory.add(In.Origins, DestOID, MergedLoans));
+ return setLoans(In, DestOID, MergedLoans);
}
LoanSet getLoans(OriginID OID, ProgramPoint P) const {
@@ -106,14 +169,30 @@ class AnalysisImpl
}
private:
+ bool isPersistent(OriginID OID) const {
+ return PersistentOrigins.contains(OID);
+ }
+
+ Lattice setLoans(Lattice L, OriginID OID, LoanSet Loans) {
+ if (isPersistent(OID)) {
+ return Lattice(OriginLoanMapFactory.add(L.PersistentOrigins, OID, Loans),
+ L.BlockLocalOrigins);
+ }
+ return Lattice(L.PersistentOrigins,
+ OriginLoanMapFactory.add(L.BlockLocalOrigins, OID, Loans));
+ }
+
LoanSet getLoans(Lattice L, OriginID OID) const {
- if (auto *Loans = L.Origins.lookup(OID))
+ const OriginLoanMap *Map =
+ isPersistent(OID) ? &L.PersistentOrigins : &L.BlockLocalOrigins;
+ if (auto *Loans = Map->lookup(OID))
return *Loans;
return LoanSetFactory.getEmptySet();
}
OriginLoanMap::Factory &OriginLoanMapFactory;
LoanSet::Factory &LoanSetFactory;
+ llvm::DenseSet<OriginID> PersistentOrigins;
};
} // namespace
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index 0c051847f4d47..40205b9a8fd19 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -543,7 +543,6 @@ TEST_F(LifetimeAnalysisTest, PointersInACycle) {
EXPECT_THAT(Origin("p1"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p2"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p3"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
- EXPECT_THAT(Origin("temp"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
}
TEST_F(LifetimeAnalysisTest, PointersAndExpirationInACycle) {
|
|
@llvm/pr-subscribers-clang Author: Utkarsh Saxena (usx95) ChangesSummaryOptimizes the lifetime analysis loan propagation by preventing block-local origins from participating in expensive join operations at block boundaries. ProblemThe lifetime analysis currently performs join operations on all origins at every block boundary. However, many origins are block-local: they exist only to propagate loans between persistent origins across temporary declarations within a single block. Including them in joins is unnecessary and expensive. SolutionThis PR classifies origins into two categories:
Implementation
Benefits
Fixes #165780 Full diff: https://github.com/llvm/llvm-project/pull/165789.diff 2 Files Affected:
diff --git a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
index 387097e705f94..3ee48facfeb57 100644
--- a/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LoanPropagation.cpp
@@ -7,10 +7,60 @@
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/LifetimeSafety/LoanPropagation.h"
#include "Dataflow.h"
+#include "llvm/Support/TimeProfiler.h"
#include <memory>
namespace clang::lifetimes::internal {
+
+// Pre-pass to find persistent origins. An origin is persistent if it is
+// referenced in more than one basic block.
+static llvm::DenseSet<OriginID> computePersistentOrigins(FactManager &FactMgr,
+ const CFG &C) {
+ llvm::TimeTraceScope("ComputePersistentOrigins");
+ llvm::DenseSet<OriginID> PersistentOrigins;
+
+ llvm::DenseMap<OriginID, const CFGBlock *> OriginToBlock;
+ for (const CFGBlock *B : C) {
+ for (const Fact *F : FactMgr.getFacts(B)) {
+ auto CheckOrigin = [&](OriginID OID) {
+ if (PersistentOrigins.count(OID))
+ return;
+ auto It = OriginToBlock.find(OID);
+ if (It == OriginToBlock.end()) {
+ OriginToBlock[OID] = B;
+ } else if (It->second != B) {
+ // We saw this origin in more than one block.
+ PersistentOrigins.insert(OID);
+ }
+ };
+
+ switch (F->getKind()) {
+ case Fact::Kind::Issue:
+ CheckOrigin(F->getAs<IssueFact>()->getOriginID());
+ break;
+ case Fact::Kind::OriginFlow: {
+ const auto *OF = F->getAs<OriginFlowFact>();
+ CheckOrigin(OF->getDestOriginID());
+ CheckOrigin(OF->getSrcOriginID());
+ break;
+ }
+ case Fact::Kind::ReturnOfOrigin:
+ CheckOrigin(F->getAs<ReturnOfOriginFact>()->getReturnedOriginID());
+ break;
+ case Fact::Kind::Use:
+ CheckOrigin(F->getAs<UseFact>()->getUsedOrigin(FactMgr.getOriginMgr()));
+ break;
+ case Fact::Kind::Expire:
+ case Fact::Kind::TestPoint:
+ break;
+ }
+ }
+ }
+ return PersistentOrigins;
+}
+
namespace {
+
/// Represents the dataflow lattice for loan propagation.
///
/// This lattice tracks which loans each origin may hold at a given program
@@ -20,21 +70,35 @@ namespace {
/// not expressions, because expressions are not visible across blocks.
struct Lattice {
/// The map from an origin to the set of loans it contains.
- OriginLoanMap Origins = OriginLoanMap(nullptr);
+ OriginLoanMap PersistentOrigins = OriginLoanMap(nullptr);
+ OriginLoanMap BlockLocalOrigins = OriginLoanMap(nullptr);
- explicit Lattice(const OriginLoanMap &S) : Origins(S) {}
+ explicit Lattice(const OriginLoanMap &Persistent,
+ const OriginLoanMap &BlockLocal)
+ : PersistentOrigins(Persistent), BlockLocalOrigins(BlockLocal) {}
Lattice() = default;
bool operator==(const Lattice &Other) const {
- return Origins == Other.Origins;
+ return PersistentOrigins == Other.PersistentOrigins &&
+ BlockLocalOrigins == Other.BlockLocalOrigins;
}
bool operator!=(const Lattice &Other) const { return !(*this == Other); }
void dump(llvm::raw_ostream &OS) const {
OS << "LoanPropagationLattice State:\n";
- if (Origins.isEmpty())
+ OS << " Persistent Origins:\n";
+ if (PersistentOrigins.isEmpty())
OS << " <empty>\n";
- for (const auto &Entry : Origins) {
+ for (const auto &Entry : PersistentOrigins) {
+ if (Entry.second.isEmpty())
+ OS << " Origin " << Entry.first << " contains no loans\n";
+ for (const LoanID &LID : Entry.second)
+ OS << " Origin " << Entry.first << " contains Loan " << LID << "\n";
+ }
+ OS << " Block-Local Origins:\n";
+ if (BlockLocalOrigins.isEmpty())
+ OS << " <empty>\n";
+ for (const auto &Entry : BlockLocalOrigins) {
if (Entry.second.isEmpty())
OS << " Origin " << Entry.first << " contains no loans\n";
for (const LoanID &LID : Entry.second)
@@ -50,7 +114,8 @@ class AnalysisImpl
OriginLoanMap::Factory &OriginLoanMapFactory,
LoanSet::Factory &LoanSetFactory)
: DataflowAnalysis(C, AC, F), OriginLoanMapFactory(OriginLoanMapFactory),
- LoanSetFactory(LoanSetFactory) {}
+ LoanSetFactory(LoanSetFactory),
+ PersistentOrigins(computePersistentOrigins(F, C)) {}
using Base::transfer;
@@ -59,10 +124,9 @@ class AnalysisImpl
Lattice getInitialState() { return Lattice{}; }
/// Merges two lattices by taking the union of loans for each origin.
- // TODO(opt): Keep the state small by removing origins which become dead.
Lattice join(Lattice A, Lattice B) {
OriginLoanMap JoinedOrigins = utils::join(
- A.Origins, B.Origins, OriginLoanMapFactory,
+ A.PersistentOrigins, B.PersistentOrigins, OriginLoanMapFactory,
[&](const LoanSet *S1, const LoanSet *S2) {
assert((S1 || S2) && "unexpectedly merging 2 empty sets");
if (!S1)
@@ -74,16 +138,15 @@ class AnalysisImpl
// Asymmetric join is a performance win. For origins present only on one
// branch, the loan set can be carried over as-is.
utils::JoinKind::Asymmetric);
- return Lattice(JoinedOrigins);
+ return Lattice(JoinedOrigins, OriginLoanMapFactory.getEmptyMap());
}
/// A new loan is issued to the origin. Old loans are erased.
Lattice transfer(Lattice In, const IssueFact &F) {
OriginID OID = F.getOriginID();
LoanID LID = F.getLoanID();
- return Lattice(OriginLoanMapFactory.add(
- In.Origins, OID,
- LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID)));
+ LoanSet NewLoans = LoanSetFactory.add(LoanSetFactory.getEmptySet(), LID);
+ return setLoans(In, OID, NewLoans);
}
/// A flow from source to destination. If `KillDest` is true, this replaces
@@ -98,7 +161,7 @@ class AnalysisImpl
LoanSet SrcLoans = getLoans(In, SrcOID);
LoanSet MergedLoans = utils::join(DestLoans, SrcLoans, LoanSetFactory);
- return Lattice(OriginLoanMapFactory.add(In.Origins, DestOID, MergedLoans));
+ return setLoans(In, DestOID, MergedLoans);
}
LoanSet getLoans(OriginID OID, ProgramPoint P) const {
@@ -106,14 +169,30 @@ class AnalysisImpl
}
private:
+ bool isPersistent(OriginID OID) const {
+ return PersistentOrigins.contains(OID);
+ }
+
+ Lattice setLoans(Lattice L, OriginID OID, LoanSet Loans) {
+ if (isPersistent(OID)) {
+ return Lattice(OriginLoanMapFactory.add(L.PersistentOrigins, OID, Loans),
+ L.BlockLocalOrigins);
+ }
+ return Lattice(L.PersistentOrigins,
+ OriginLoanMapFactory.add(L.BlockLocalOrigins, OID, Loans));
+ }
+
LoanSet getLoans(Lattice L, OriginID OID) const {
- if (auto *Loans = L.Origins.lookup(OID))
+ const OriginLoanMap *Map =
+ isPersistent(OID) ? &L.PersistentOrigins : &L.BlockLocalOrigins;
+ if (auto *Loans = Map->lookup(OID))
return *Loans;
return LoanSetFactory.getEmptySet();
}
OriginLoanMap::Factory &OriginLoanMapFactory;
LoanSet::Factory &LoanSetFactory;
+ llvm::DenseSet<OriginID> PersistentOrigins;
};
} // namespace
diff --git a/clang/unittests/Analysis/LifetimeSafetyTest.cpp b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
index 0c051847f4d47..40205b9a8fd19 100644
--- a/clang/unittests/Analysis/LifetimeSafetyTest.cpp
+++ b/clang/unittests/Analysis/LifetimeSafetyTest.cpp
@@ -543,7 +543,6 @@ TEST_F(LifetimeAnalysisTest, PointersInACycle) {
EXPECT_THAT(Origin("p1"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p2"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
EXPECT_THAT(Origin("p3"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
- EXPECT_THAT(Origin("temp"), HasLoansTo({"v1", "v2", "v3"}, "after_loop"));
}
TEST_F(LifetimeAnalysisTest, PointersAndExpirationInACycle) {
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Summary
Optimizes the lifetime analysis loan propagation by preventing block-local origins from participating in expensive join operations at block boundaries.
Problem
The lifetime analysis currently performs join operations on all origins at every block boundary. However, many origins are block-local: they exist only to propagate loans between persistent origins across temporary declarations and expressions within a single block. Including them in joins is unnecessary and expensive.
Solution
This PR classifies origins into two categories:
Implementation
computePersistentOrigins): Analyzes all facts in the CFG to identify which origins appear in multiple blocksOriginLoanMaps:PersistentOrigins: participates in join operationsBlockLocalOrigins: used during block execution, discarded at boundariesBenefits
Fixes: #165780
Fixes: #164625. It brings down regression from 150% to 2%.