[clang] [clang][nullability] Don't discard expression state before end of full-expression. (PR #82611)
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Tue Mar 5 03:41:40 PST 2024
https://github.com/martinboehme updated https://github.com/llvm/llvm-project/pull/82611
>From 109e72445fb8da4dd0cf08b5985986ca864a3536 Mon Sep 17 00:00:00 2001
From: Martin Braenne <mboehme at google.com>
Date: Thu, 22 Feb 2024 11:23:30 +0000
Subject: [PATCH 1/2] [clang][nullability] Don't discard expression state
before end of full-expression.
In https://github.com/llvm/llvm-project/pull/72985, I made a change to discard
expression state (`ExprToLoc` and `ExprToVal`) at the beginning of each basic
block. I did so with the claim that "we never need to access entries from these
maps outside of the current basic block", noting that there are exceptions to
this claim when control flow happens inside a full-expression (the operands of
`&&`, `||`, and the conditional operator live in different basic blocks than the
operator itself) but that we already have a mechanism for retrieving the values
of these operands from the environment for the block they are computed in.
It turns out, however, that the operands of these operators aren't the only
expressions whose values can be accessed from a different basic block; when
control flow happens within a full-expression, that control flow can be
"interposed" between an expression and its parent. Here is an example:
```cxx
void f(int*, int);
bool cond();
void target() {
int i = 0;
f(&i, cond() ? 1 : 0);
}
```
([godbolt](https://godbolt.org/z/hrbj1Mj3o))
In the CFG[^1] , note how the expression for `&i` is computed in block B4,
but the parent of this expression (the `CallExpr`) is located in block B1.
The the argument expression `&i` and the `CallExpr` are essentially "torn apart"
into different basic blocks by the conditional operator in the second argument.
In other words, the edge between the `CallExpr` and its argument `&i` straddles
the boundary between two blocks.
I used to think that this scenario -- where an edge between an expression and
one of its children straddles a block boundary -- could only happen between the
expression that triggers the control flow (`&&`, `||`, or the conditional
operator) and its children, but the example above shows that other expressions
can be affected as well; the control flow is still triggered by `&&`, `||` or
the conditional operator, but the expressions affected lie outside these
operators.
Discarding expression state too soon is harmful. For example, an analysis that
checks the arguments of the `CallExpr` above would not be able to retrieve a
value for the `&i` argument.
This patch therefore ensures that we don't discard expression state before the
end of a full-expression. In other cases -- when the evaluation of a
full-expression is complete -- we still want to discard expression state for the
reasons explained in https://github.com/llvm/llvm-project/pull/72985 (avoid
performing joins on boolean values that are no longer needed, which
unnecessarily extends the flow condition; improve debuggability by removing
clutter from the expression state).
[^1]:
```
[B5 (ENTRY)]
Succs (1): B4
[B1]
1: [B4.9] ? [B2.1] : [B3.1]
2: [B4.4]([B4.6], [B1.1])
Preds (2): B2 B3
Succs (1): B0
[B2]
1: 1
Preds (1): B4
Succs (1): B1
[B3]
1: 0
Preds (1): B4
Succs (1): B1
[B4]
1: 0
2: int i = 0;
3: f
4: [B4.3] (ImplicitCastExpr, FunctionToPointerDecay, void (*)(int *, int))
5: i
6: &[B4.5]
7: cond
8: [B4.7] (ImplicitCastExpr, FunctionToPointerDecay, _Bool (*)(void))
9: [B4.8]()
T: [B4.9] ? ... : ...
Preds (1): B5
Succs (2): B2 B3
[B0 (EXIT)]
Preds (1): B1
```
---
.../FlowSensitive/ControlFlowContext.h | 25 ++++-
.../FlowSensitive/DataflowEnvironment.h | 11 +-
.../FlowSensitive/ControlFlowContext.cpp | 36 +++++-
.../FlowSensitive/DataflowEnvironment.cpp | 28 ++++-
.../TypeErasedDataflowAnalysis.cpp | 32 ++++--
.../FlowSensitive/DataflowEnvironmentTest.cpp | 3 +-
.../TypeErasedDataflowAnalysisTest.cpp | 104 ++++++++++++------
7 files changed, 187 insertions(+), 52 deletions(-)
diff --git a/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h b/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
index 405e93287a05d3..9a0a00f3c01343 100644
--- a/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
+++ b/clang/include/clang/Analysis/FlowSensitive/ControlFlowContext.h
@@ -58,19 +58,36 @@ class ControlFlowContext {
return BlockReachable[B.getBlockID()];
}
+ /// Returns whether `B` contains an expression that is consumed in a
+ /// different block than `B` (i.e. the parent of the expression is in a
+ /// different block).
+ /// This happens if there is control flow within a full-expression (triggered
+ /// by `&&`, `||`, or the conditional operator). Note that the operands of
+ /// these operators are not the only expressions that can be consumed in a
+ /// different block. For example, in the function call
+ /// `f(&i, cond() ? 1 : 0)`, `&i` is in a different block than the `CallExpr`.
+ bool containsExprConsumedInDifferentBlock(const CFGBlock &B) const {
+ return ContainsExprConsumedInDifferentBlock.contains(&B);
+ }
+
private:
- ControlFlowContext(const Decl &D, std::unique_ptr<CFG> Cfg,
- llvm::DenseMap<const Stmt *, const CFGBlock *> StmtToBlock,
- llvm::BitVector BlockReachable)
+ ControlFlowContext(
+ const Decl &D, std::unique_ptr<CFG> Cfg,
+ llvm::DenseMap<const Stmt *, const CFGBlock *> StmtToBlock,
+ llvm::BitVector BlockReachable,
+ llvm::DenseSet<const CFGBlock *> ContainsExprConsumedInDifferentBlock)
: ContainingDecl(D), Cfg(std::move(Cfg)),
StmtToBlock(std::move(StmtToBlock)),
- BlockReachable(std::move(BlockReachable)) {}
+ BlockReachable(std::move(BlockReachable)),
+ ContainsExprConsumedInDifferentBlock(
+ std::move(ContainsExprConsumedInDifferentBlock)) {}
/// The `Decl` containing the statement used to construct the CFG.
const Decl &ContainingDecl;
std::unique_ptr<CFG> Cfg;
llvm::DenseMap<const Stmt *, const CFGBlock *> StmtToBlock;
llvm::BitVector BlockReachable;
+ llvm::DenseSet<const CFGBlock *> ContainsExprConsumedInDifferentBlock;
};
} // namespace dataflow
diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
index b3dc940705f870..75d43f67864b56 100644
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h
@@ -240,6 +240,14 @@ class Environment {
bool equivalentTo(const Environment &Other,
Environment::ValueModel &Model) const;
+ /// How to treat expression state (`ExprToLoc` and `ExprToVal`) in a join.
+ /// If the join happens within a full expression, expression state should be
+ /// kept; otherwise, we can discard it.
+ enum ExprJoinBehavior {
+ DiscardExprState,
+ KeepExprState,
+ };
+
/// Joins two environments by taking the intersection of storage locations and
/// values that are stored in them. Distinct values that are assigned to the
/// same storage locations in `EnvA` and `EnvB` are merged using `Model`.
@@ -248,7 +256,8 @@ class Environment {
///
/// `EnvA` and `EnvB` must use the same `DataflowAnalysisContext`.
static Environment join(const Environment &EnvA, const Environment &EnvB,
- Environment::ValueModel &Model);
+ Environment::ValueModel &Model,
+ ExprJoinBehavior ExprBehavior);
/// Widens the environment point-wise, using `PrevEnv` as needed to inform the
/// approximation.
diff --git a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
index 8aed19544be6a2..6058b557d353f6 100644
--- a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
+++ b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
@@ -94,6 +94,36 @@ static llvm::BitVector findReachableBlocks(const CFG &Cfg) {
return BlockReachable;
}
+static llvm::DenseSet<const CFGBlock *>
+buildContainsExprConsumedInDifferentBlock(
+ const CFG &Cfg,
+ const llvm::DenseMap<const Stmt *, const CFGBlock *> &StmtToBlock) {
+ llvm::DenseSet<const CFGBlock *> Result;
+
+ auto CheckChildExprs = [&Result, &StmtToBlock](const Stmt *S,
+ const CFGBlock *Block) {
+ for (const Stmt *Child : S->children()) {
+ const CFGBlock *ChildBlock = StmtToBlock.lookup(Child);
+ if (isa<Expr>(Child) && ChildBlock != Block)
+ Result.insert(ChildBlock);
+ }
+ };
+
+ for (const CFGBlock *Block : Cfg) {
+ if (Block == nullptr)
+ continue;
+
+ for (const CFGElement &Element : *Block)
+ if (auto S = Element.getAs<CFGStmt>())
+ CheckChildExprs(S->getStmt(), Block);
+
+ if (const Stmt *TerminatorCond = Block->getTerminatorCondition())
+ CheckChildExprs(TerminatorCond, Block);
+ }
+
+ return Result;
+}
+
llvm::Expected<ControlFlowContext>
ControlFlowContext::build(const FunctionDecl &Func) {
if (!Func.doesThisDeclarationHaveABody())
@@ -140,8 +170,12 @@ ControlFlowContext::build(const Decl &D, Stmt &S, ASTContext &C) {
llvm::BitVector BlockReachable = findReachableBlocks(*Cfg);
+ llvm::DenseSet<const CFGBlock *> ContainsExprConsumedInDifferentBlock =
+ buildContainsExprConsumedInDifferentBlock(*Cfg, StmtToBlock);
+
return ControlFlowContext(D, std::move(Cfg), std::move(StmtToBlock),
- std::move(BlockReachable));
+ std::move(BlockReachable),
+ std::move(ContainsExprConsumedInDifferentBlock));
}
} // namespace dataflow
diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
index 0cfc26ea952cda..df1c5aa245007a 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -48,6 +48,24 @@ static llvm::DenseMap<const ValueDecl *, StorageLocation *> intersectDeclToLoc(
return Result;
}
+// Performs a join on either `ExprToLoc` or `ExprToVal`.
+// The maps must be consistent in the sense that any entries for the same
+// expression must map to the same location / value. This is the case if we are
+// performing a join for control flow within a full-expression (which is the
+// only case when this function should be used).
+template <typename MapT> MapT joinExprMaps(const MapT &Map1, const MapT &Map2) {
+ MapT Result = Map1;
+
+ for (const auto &Entry : Map2) {
+ [[maybe_unused]] auto [It, Inserted] = Result.insert(Entry);
+ // If there was an existing entry, its value should be the same as for the
+ // entry we were trying to insert.
+ assert(It->second == Entry.second);
+ }
+
+ return Result;
+}
+
// Whether to consider equivalent two values with an unknown relation.
//
// FIXME: this function is a hack enabling unsoundness to support
@@ -627,7 +645,8 @@ LatticeJoinEffect Environment::widen(const Environment &PrevEnv,
}
Environment Environment::join(const Environment &EnvA, const Environment &EnvB,
- Environment::ValueModel &Model) {
+ Environment::ValueModel &Model,
+ ExprJoinBehavior ExprBehavior) {
assert(EnvA.DACtx == EnvB.DACtx);
assert(EnvA.ThisPointeeLoc == EnvB.ThisPointeeLoc);
assert(EnvA.CallStack == EnvB.CallStack);
@@ -675,9 +694,10 @@ Environment Environment::join(const Environment &EnvA, const Environment &EnvB,
JoinedEnv.LocToVal =
joinLocToVal(EnvA.LocToVal, EnvB.LocToVal, EnvA, EnvB, JoinedEnv, Model);
- // We intentionally leave `JoinedEnv.ExprToLoc` and `JoinedEnv.ExprToVal`
- // empty, as we never need to access entries in these maps outside of the
- // basic block that sets them.
+ if (ExprBehavior == KeepExprState) {
+ JoinedEnv.ExprToVal = joinExprMaps(EnvA.ExprToVal, EnvB.ExprToVal);
+ JoinedEnv.ExprToLoc = joinExprMaps(EnvA.ExprToLoc, EnvB.ExprToLoc);
+ }
return JoinedEnv;
}
diff --git a/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp b/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
index 4c88c46142d64d..06acc95346fa9d 100644
--- a/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
+++ b/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
@@ -221,6 +221,7 @@ class PrettyStackTraceCFGElement : public llvm::PrettyStackTraceEntry {
// Avoids unneccesary copies of the environment.
class JoinedStateBuilder {
AnalysisContext &AC;
+ Environment::ExprJoinBehavior ExprBehavior;
std::vector<const TypeErasedDataflowAnalysisState *> All;
std::deque<TypeErasedDataflowAnalysisState> Owned;
@@ -228,11 +229,13 @@ class JoinedStateBuilder {
join(const TypeErasedDataflowAnalysisState &L,
const TypeErasedDataflowAnalysisState &R) {
return {AC.Analysis.joinTypeErased(L.Lattice, R.Lattice),
- Environment::join(L.Env, R.Env, AC.Analysis)};
+ Environment::join(L.Env, R.Env, AC.Analysis, ExprBehavior)};
}
public:
- JoinedStateBuilder(AnalysisContext &AC) : AC(AC) {}
+ JoinedStateBuilder(AnalysisContext &AC,
+ Environment::ExprJoinBehavior ExprBehavior)
+ : AC(AC), ExprBehavior(ExprBehavior) {}
void addOwned(TypeErasedDataflowAnalysisState State) {
Owned.push_back(std::move(State));
@@ -248,12 +251,12 @@ class JoinedStateBuilder {
// initialize the state of each basic block differently.
return {AC.Analysis.typeErasedInitialElement(), AC.InitEnv.fork()};
if (All.size() == 1)
- // Join the environment with itself so that we discard the entries from
- // `ExprToLoc` and `ExprToVal`.
+ // Join the environment with itself so that we discard expression state if
+ // desired.
// FIXME: We could consider writing special-case code for this that only
// does the discarding, but it's not clear if this is worth it.
- return {All[0]->Lattice,
- Environment::join(All[0]->Env, All[0]->Env, AC.Analysis)};
+ return {All[0]->Lattice, Environment::join(All[0]->Env, All[0]->Env,
+ AC.Analysis, ExprBehavior)};
auto Result = join(*All[0], *All[1]);
for (unsigned I = 2; I < All.size(); ++I)
@@ -307,7 +310,22 @@ computeBlockInputState(const CFGBlock &Block, AnalysisContext &AC) {
}
}
- JoinedStateBuilder Builder(AC);
+ // If any of the predecessor blocks contains an expression consumed in a
+ // different block, we need to keep expression state.
+ // Note that in this case, we keep expression state for all predecessors,
+ // rather than only those predecessors that actually contain an expression
+ // consumed in a different block. While this is potentially suboptimal, it's
+ // actually likely, if we have control flow within a full expression, that
+ // all predecessors have expression state consumed in a different block.
+ Environment::ExprJoinBehavior ExprBehavior = Environment::DiscardExprState;
+ for (const CFGBlock *Pred : Preds) {
+ if (Pred && AC.CFCtx.containsExprConsumedInDifferentBlock(*Pred)) {
+ ExprBehavior = Environment::KeepExprState;
+ break;
+ }
+ }
+
+ JoinedStateBuilder Builder(AC, ExprBehavior);
for (const CFGBlock *Pred : Preds) {
// Skip if the `Block` is unreachable or control flow cannot get past it.
if (!Pred || Pred->hasNoReturnElement())
diff --git a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
index 8799d03dfd3c58..465a8e21690c4a 100644
--- a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
@@ -190,7 +190,8 @@ TEST_F(EnvironmentTest, JoinRecords) {
Env2.setValue(Loc, Val2);
Environment::ValueModel Model;
- Environment EnvJoined = Environment::join(Env1, Env2, Model);
+ Environment EnvJoined =
+ Environment::join(Env1, Env2, Model, Environment::DiscardExprState);
auto *JoinedVal = cast<RecordValue>(EnvJoined.getValue(Loc));
EXPECT_NE(JoinedVal, &Val1);
EXPECT_NE(JoinedVal, &Val2);
diff --git a/clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp b/clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp
index 34f9b0b23719fe..9d05a0d6ca4010 100644
--- a/clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/TypeErasedDataflowAnalysisTest.cpp
@@ -244,15 +244,17 @@ TEST_F(DiscardExprStateTest, WhileStatement) {
EXPECT_NE(NotEqOpState.Env.getValue(NotEqOp), nullptr);
// In the block that calls `foo(p)`, the value for `p != nullptr` is discarded
- // because it is not consumed by this block.
+ // because it is not consumed outside the block it is in.
const auto &CallFooState = blockStateForStmt(BlockStates, CallFoo);
EXPECT_EQ(CallFooState.Env.getValue(NotEqOp), nullptr);
}
TEST_F(DiscardExprStateTest, BooleanOperator) {
std::string Code = R"(
- bool target(bool b1, bool b2) {
- return b1 && b2;
+ void f();
+ void target(bool b1, bool b2) {
+ if (b1 && b2)
+ f();
}
)";
auto BlockStates = llvm::cantFail(runAnalysis<NoopAnalysis>(
@@ -260,46 +262,80 @@ TEST_F(DiscardExprStateTest, BooleanOperator) {
const auto &AndOp =
matchNode<BinaryOperator>(binaryOperator(hasOperatorName("&&")));
- const auto &Return = matchNode<ReturnStmt>(returnStmt());
+ const auto &CallF =
+ matchNode<CallExpr>(callExpr(callee(functionDecl(hasName("f")))));
// In the block that evaluates the LHS of the `&&` operator, the LHS is
// associated with a value, while the right-hand side is not (unsurprisingly,
// as it hasn't been evaluated yet).
const auto &LHSState = blockStateForStmt(BlockStates, *AndOp.getLHS());
auto *LHSValue = cast<BoolValue>(LHSState.Env.getValue(*AndOp.getLHS()));
- ASSERT_NE(LHSValue, nullptr);
+ EXPECT_NE(LHSValue, nullptr);
EXPECT_EQ(LHSState.Env.getValue(*AndOp.getRHS()), nullptr);
- // In the block that evaluates the RHS, the RHS is associated with a
- // value. The value for the LHS has been discarded as it is not consumed by
- // this block.
+ // In the block that evaluates the RHS, both the LHS and RHS are associated
+ // with values, as they are both subexpressions of the `&&` operator, which
+ // is evaluated in a later block.
const auto &RHSState = blockStateForStmt(BlockStates, *AndOp.getRHS());
- EXPECT_EQ(RHSState.Env.getValue(*AndOp.getLHS()), nullptr);
- auto *RHSValue = cast<BoolValue>(RHSState.Env.getValue(*AndOp.getRHS()));
- ASSERT_NE(RHSValue, nullptr);
-
- // In the block that evaluates the return statement, the expression `b1 && b2`
- // is associated with a value (and check that it's the right one).
- // The expressions `b1` and `b2` are _not_ associated with a value in this
- // block, even though they are consumed by the block, because:
- // * This block has two prececessor blocks (the one that evaluates `b1` and
- // the one that evaluates `b2`).
- // * `b1` is only associated with a value in the block that evaluates `b1` but
- // not the block that evalutes `b2`, so the join operation discards the
- // value for `b1`.
- // * `b2` is only associated with a value in the block that evaluates `b2` but
- // not the block that evaluates `b1`, the the join operation discards the
- // value for `b2`.
- // Nevertheless, the analysis generates the correct formula for `b1 && b2`
- // because the transfer function for the `&&` operator retrieves the values
- // for its operands from the environments for the blocks that compute the
- // operands, rather than from the environment for the block that contains the
- // `&&`.
- const auto &ReturnState = blockStateForStmt(BlockStates, Return);
- EXPECT_EQ(ReturnState.Env.getValue(*AndOp.getLHS()), nullptr);
- EXPECT_EQ(ReturnState.Env.getValue(*AndOp.getRHS()), nullptr);
- EXPECT_EQ(ReturnState.Env.getValue(AndOp),
- &ReturnState.Env.makeAnd(*LHSValue, *RHSValue));
+ EXPECT_EQ(RHSState.Env.getValue(*AndOp.getLHS()), LHSValue);
+ auto *RHSValue = RHSState.Env.get<BoolValue>(*AndOp.getRHS());
+ EXPECT_NE(RHSValue, nullptr);
+
+ // In the block that evaluates `b1 && b2`, the `&&` as well as its operands
+ // are associated with values.
+ const auto &AndOpState = blockStateForStmt(BlockStates, AndOp);
+ EXPECT_EQ(AndOpState.Env.getValue(*AndOp.getLHS()), LHSValue);
+ EXPECT_EQ(AndOpState.Env.getValue(*AndOp.getRHS()), RHSValue);
+ EXPECT_EQ(AndOpState.Env.getValue(AndOp),
+ &AndOpState.Env.makeAnd(*LHSValue, *RHSValue));
+
+ // In the block that calls `f()`, none of `b1`, `b2`, or `b1 && b2` should be
+ // associated with values.
+ const auto &CallFState = blockStateForStmt(BlockStates, CallF);
+ EXPECT_EQ(CallFState.Env.getValue(*AndOp.getLHS()), nullptr);
+ EXPECT_EQ(CallFState.Env.getValue(*AndOp.getRHS()), nullptr);
+ EXPECT_EQ(CallFState.Env.getValue(AndOp), nullptr);
+}
+
+TEST_F(DiscardExprStateTest, ConditionalOperator) {
+ std::string Code = R"(
+ void f(int*, int);
+ void g();
+ bool cond();
+
+ void target() {
+ int i = 0;
+ if (cond())
+ f(&i, cond() ? 1 : 0);
+ g();
+ }
+ )";
+ auto BlockStates = llvm::cantFail(runAnalysis<NoopAnalysis>(
+ Code, [](ASTContext &C) { return NoopAnalysis(C); }));
+
+ const auto &AddrOfI =
+ matchNode<UnaryOperator>(unaryOperator(hasOperatorName("&")));
+ const auto &CallF =
+ matchNode<CallExpr>(callExpr(callee(functionDecl(hasName("f")))));
+ const auto &CallG =
+ matchNode<CallExpr>(callExpr(callee(functionDecl(hasName("g")))));
+
+ // In the block that evaluates `&i`, it should obviously have a value.
+ const auto &AddrOfIState = blockStateForStmt(BlockStates, AddrOfI);
+ auto *AddrOfIVal = AddrOfIState.Env.get<PointerValue>(AddrOfI);
+ EXPECT_NE(AddrOfIVal, nullptr);
+
+ // Because of the conditional operator, the `f(...)` call is evaluated in a
+ // different block than `&i`, but `&i` still needs to have a value here
+ // because it's a subexpression of the call.
+ const auto &CallFState = blockStateForStmt(BlockStates, CallF);
+ EXPECT_NE(&CallFState, &AddrOfIState);
+ EXPECT_EQ(CallFState.Env.get<PointerValue>(AddrOfI), AddrOfIVal);
+
+ // In the block that calls `g()`, `&i` should no longer be associated with a
+ // value.
+ const auto &CallGState = blockStateForStmt(BlockStates, CallG);
+ EXPECT_EQ(CallGState.Env.get<PointerValue>(AddrOfI), nullptr);
}
struct NonConvergingLattice {
>From 6efacbe479e7de334d696727a98bacc1522f7f20 Mon Sep 17 00:00:00 2001
From: Martin Braenne <mboehme at google.com>
Date: Tue, 5 Mar 2024 11:41:01 +0000
Subject: [PATCH 2/2] fixup! [clang][nullability] Don't discard expression
state before end of full-expression.
---
.../FlowSensitive/ControlFlowContext.cpp | 4 +++-
.../FlowSensitive/TypeErasedDataflowAnalysis.cpp | 16 ++++++++--------
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
index 6058b557d353f6..7c9f8fbb0a7009 100644
--- a/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
+++ b/clang/lib/Analysis/FlowSensitive/ControlFlowContext.cpp
@@ -103,8 +103,10 @@ buildContainsExprConsumedInDifferentBlock(
auto CheckChildExprs = [&Result, &StmtToBlock](const Stmt *S,
const CFGBlock *Block) {
for (const Stmt *Child : S->children()) {
+ if (!isa<Expr>(Child))
+ continue;
const CFGBlock *ChildBlock = StmtToBlock.lookup(Child);
- if (isa<Expr>(Child) && ChildBlock != Block)
+ if (ChildBlock != Block)
Result.insert(ChildBlock);
}
};
diff --git a/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp b/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
index 06acc95346fa9d..a9f39e153d0ce1 100644
--- a/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
+++ b/clang/lib/Analysis/FlowSensitive/TypeErasedDataflowAnalysis.cpp
@@ -221,7 +221,7 @@ class PrettyStackTraceCFGElement : public llvm::PrettyStackTraceEntry {
// Avoids unneccesary copies of the environment.
class JoinedStateBuilder {
AnalysisContext &AC;
- Environment::ExprJoinBehavior ExprBehavior;
+ Environment::ExprJoinBehavior JoinBehavior;
std::vector<const TypeErasedDataflowAnalysisState *> All;
std::deque<TypeErasedDataflowAnalysisState> Owned;
@@ -229,13 +229,13 @@ class JoinedStateBuilder {
join(const TypeErasedDataflowAnalysisState &L,
const TypeErasedDataflowAnalysisState &R) {
return {AC.Analysis.joinTypeErased(L.Lattice, R.Lattice),
- Environment::join(L.Env, R.Env, AC.Analysis, ExprBehavior)};
+ Environment::join(L.Env, R.Env, AC.Analysis, JoinBehavior)};
}
public:
JoinedStateBuilder(AnalysisContext &AC,
- Environment::ExprJoinBehavior ExprBehavior)
- : AC(AC), ExprBehavior(ExprBehavior) {}
+ Environment::ExprJoinBehavior JoinBehavior)
+ : AC(AC), JoinBehavior(JoinBehavior) {}
void addOwned(TypeErasedDataflowAnalysisState State) {
Owned.push_back(std::move(State));
@@ -256,7 +256,7 @@ class JoinedStateBuilder {
// FIXME: We could consider writing special-case code for this that only
// does the discarding, but it's not clear if this is worth it.
return {All[0]->Lattice, Environment::join(All[0]->Env, All[0]->Env,
- AC.Analysis, ExprBehavior)};
+ AC.Analysis, JoinBehavior)};
auto Result = join(*All[0], *All[1]);
for (unsigned I = 2; I < All.size(); ++I)
@@ -317,15 +317,15 @@ computeBlockInputState(const CFGBlock &Block, AnalysisContext &AC) {
// consumed in a different block. While this is potentially suboptimal, it's
// actually likely, if we have control flow within a full expression, that
// all predecessors have expression state consumed in a different block.
- Environment::ExprJoinBehavior ExprBehavior = Environment::DiscardExprState;
+ Environment::ExprJoinBehavior JoinBehavior = Environment::DiscardExprState;
for (const CFGBlock *Pred : Preds) {
if (Pred && AC.CFCtx.containsExprConsumedInDifferentBlock(*Pred)) {
- ExprBehavior = Environment::KeepExprState;
+ JoinBehavior = Environment::KeepExprState;
break;
}
}
- JoinedStateBuilder Builder(AC, ExprBehavior);
+ JoinedStateBuilder Builder(AC, JoinBehavior);
for (const CFGBlock *Pred : Preds) {
// Skip if the `Block` is unreachable or control flow cannot get past it.
if (!Pred || Pred->hasNoReturnElement())
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