[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
usx95 wrote: ### Merge activity * **Jul 21, 9:57 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/149199). https://github.com/llvm/llvm-project/pull/149199 ___ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
https://github.com/Xazax-hun approved this pull request. LG, thanks! https://github.com/llvm/llvm-project/pull/149199 ___ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
@@ -524,14 +531,20 @@ template
class DataflowAnalysis {
public:
using Lattice = LatticeType;
- using Base = DataflowAnalysis;
+ using Base = DataflowAnalysis;
private:
const CFG &Cfg;
AnalysisDeclContext ∾
+ /// The dataflow state before a basic block is processed.
llvm::DenseMap InStates;
+ /// The dataflow state after a basic block is processed.
llvm::DenseMap OutStates;
+ /// The dataflow state at a Program Point.
+ /// In a forward analysis, this is the state after the Fact at that point has
+ /// been applied, while in a backward analysis, it is the state before.
+ llvm::DenseMap PerPointStates;
Xazax-hun wrote:
Ah never mind. Now I remember you want to keep these states instead of
replaying the analysis for the blocks.
https://github.com/llvm/llvm-project/pull/149199
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[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
@@ -524,14 +531,20 @@ template
class DataflowAnalysis {
public:
using Lattice = LatticeType;
- using Base = DataflowAnalysis;
+ using Base = DataflowAnalysis;
private:
const CFG &Cfg;
AnalysisDeclContext ∾
+ /// The dataflow state before a basic block is processed.
llvm::DenseMap InStates;
+ /// The dataflow state after a basic block is processed.
llvm::DenseMap OutStates;
+ /// The dataflow state at a Program Point.
+ /// In a forward analysis, this is the state after the Fact at that point has
+ /// been applied, while in a backward analysis, it is the state before.
+ llvm::DenseMap PerPointStates;
Xazax-hun wrote:
Do you think all of the analyses need `PerPointStates`? E.g., what about the
`ExpiredLoansAnalysis`? I wonder if we should have a boolean policy here.
https://github.com/llvm/llvm-project/pull/149199
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[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
@@ -502,6 +502,12 @@ class FactGenerator : public
ConstStmtVisitor {
enum class Direction { Forward, Backward };
+/// A program point is a pair of a CFGBlock and a Fact within that block.
+///
+/// This is used to represent the state of the program *after* the Fact is
+/// executed.
+using ProgramPoint = std::pair;
usx95 wrote:
Hmm. Looks like an oversight. Thanks for spotting.
https://github.com/llvm/llvm-project/pull/149199
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[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
https://github.com/usx95 updated
https://github.com/llvm/llvm-project/pull/149199
>From 3e67c98b4a365948910a3da9ad5d56a6087a527a Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena
Date: Wed, 16 Jul 2025 21:57:03 +
Subject: [PATCH] address comment
---
clang/lib/Analysis/LifetimeSafety.cpp | 39 +--
1 file changed, 31 insertions(+), 8 deletions(-)
diff --git a/clang/lib/Analysis/LifetimeSafety.cpp
b/clang/lib/Analysis/LifetimeSafety.cpp
index e3a03cf93880e..a95db6d8013bd 100644
--- a/clang/lib/Analysis/LifetimeSafety.cpp
+++ b/clang/lib/Analysis/LifetimeSafety.cpp
@@ -502,6 +502,13 @@ class FactGenerator : public
ConstStmtVisitor {
enum class Direction { Forward, Backward };
+/// A `ProgramPoint` identifies a location in the CFG by pointing to a specific
+/// `Fact`. identified by a lifetime-related event (`Fact`).
+///
+/// A `ProgramPoint` has "after" semantics: it represents the location
+/// immediately after its corresponding `Fact`.
+using ProgramPoint = const Fact *;
+
/// A generic, policy-based driver for dataflow analyses. It combines
/// the dataflow runner and the transferer logic into a single class hierarchy.
///
@@ -524,14 +531,20 @@ template
class DataflowAnalysis {
public:
using Lattice = LatticeType;
- using Base = DataflowAnalysis;
+ using Base = DataflowAnalysis;
private:
const CFG &Cfg;
AnalysisDeclContext ∾
+ /// The dataflow state before a basic block is processed.
llvm::DenseMap InStates;
+ /// The dataflow state after a basic block is processed.
llvm::DenseMap OutStates;
+ /// The dataflow state at a Program Point.
+ /// In a forward analysis, this is the state after the Fact at that point has
+ /// been applied, while in a backward analysis, it is the state before.
+ llvm::DenseMap PerPointStates;
static constexpr bool isForward() { return Dir == Direction::Forward; }
@@ -577,6 +590,8 @@ class DataflowAnalysis {
}
}
+ Lattice getState(ProgramPoint P) const { return PerPointStates.lookup(P); }
+
Lattice getInState(const CFGBlock *B) const { return InStates.lookup(B); }
Lattice getOutState(const CFGBlock *B) const { return OutStates.lookup(B); }
@@ -590,18 +605,23 @@ class DataflowAnalysis {
getOutState(&B).dump(llvm::dbgs());
}
+private:
/// Computes the state at one end of a block by applying all its facts
/// sequentially to a given state from the other end.
- /// TODO: We might need to store intermediate states per-fact in the block
for
- /// later analysis.
Lattice transferBlock(const CFGBlock *Block, Lattice State) {
auto Facts = AllFacts.getFacts(Block);
-if constexpr (isForward())
- for (const Fact *F : Facts)
+if constexpr (isForward()) {
+ for (const Fact *F : Facts) {
State = transferFact(State, F);
-else
- for (const Fact *F : llvm::reverse(Facts))
+PerPointStates[F] = State;
+ }
+} else {
+ for (const Fact *F : llvm::reverse(Facts)) {
+// In backward analysis, capture the state before applying the fact.
+PerPointStates[F] = State;
State = transferFact(State, F);
+ }
+}
return State;
}
@@ -769,6 +789,10 @@ class LoanPropagationAnalysis
Factory.OriginMapFactory.add(In.Origins, DestOID, SrcLoans));
}
+ LoanSet getLoans(OriginID OID, ProgramPoint P) {
+return getLoans(getState(P), OID);
+ }
+
private:
LoanSet getLoans(Lattice L, OriginID OID) {
if (auto *Loans = L.Origins.lookup(OID))
@@ -779,7 +803,6 @@ class LoanPropagationAnalysis
// = //
// TODO:
-// - Modifying loan propagation to answer `LoanSet getLoans(Origin O, Point P)`
// - Modify loan expiry analysis to answer `bool isExpired(Loan L, Point P)`
// - Modify origin liveness analysis to answer `bool isLive(Origin O, Point P)`
// - Using the above three to perform the final error reporting.
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[clang] [LifetimeSafety] Add per-program-point lattice tracking (PR #149199)
@@ -502,6 +502,12 @@ class FactGenerator : public
ConstStmtVisitor {
enum class Direction { Forward, Backward };
+/// A program point is a pair of a CFGBlock and a Fact within that block.
+///
+/// This is used to represent the state of the program *after* the Fact is
+/// executed.
+using ProgramPoint = std::pair;
Xazax-hun wrote:
Why do we need the CfgBlock? Wouldn't a fact alone be sufficient?
https://github.com/llvm/llvm-project/pull/149199
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