[clang] [clang][dataflow] Propagate storage location of compound assignment operators. (PR #94332)

[via cfe-commits]

https://github.com/martinboehme created https://github.com/llvm/llvm-project/pull/94332

To avoid generating unnecessary values, we don't create a new value but instead
leave it to the specific analysis to do this if desired.


>From 6c3273f278cc497992e9a7ed7fc7fbec439d6207 Mon Sep 17 00:00:00 2001
From: Martin Braenne <mboehme at google.com>
Date: Tue, 4 Jun 2024 10:29:13 +0000
Subject: [PATCH] [clang][dataflow] Propagate storage location of compound
 assignment operators.

To avoid generating unnecessary values, we don't create a new value but instead
leave it to the specific analysis to do this if desired.
---
 clang/lib/Analysis/FlowSensitive/Transfer.cpp |  7 +++++++
 .../Analysis/FlowSensitive/TransferTest.cpp   | 20 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/clang/lib/Analysis/FlowSensitive/Transfer.cpp b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
index d161b231c0b6f..8109ac6a781e7 100644
--- a/clang/lib/Analysis/FlowSensitive/Transfer.cpp
+++ b/clang/lib/Analysis/FlowSensitive/Transfer.cpp
@@ -147,6 +147,13 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
     const Expr *RHS = S->getRHS();
     assert(RHS != nullptr);
 
+    // Do compound assignments up-front, as there are so many of them and we
+    // don't want to list all of them in the switch statement below.
+    // To avoid generating unnecessary values, we don't create a new value but
+    // instead leave it to the specific analysis to do this if desired.
+    if (S->isCompoundAssignmentOp())
+      propagateStorageLocation(*S->getLHS(), *S, Env);
+
     switch (S->getOpcode()) {
     case BO_Assign: {
       auto *LHSLoc = Env.getStorageLocation(*LHS);
diff --git a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
index cdaee9b2c9288..f7e6b0c22e8db 100644
--- a/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
@@ -3796,6 +3796,26 @@ TEST(TransferTest, Postincrement) {
       });
 }
 
+// We test just one of the compound assignment operators because we know the
+// code for propagating the storage location is shared among all of them.
+TEST(TransferTest, AddAssign) {
+  std::string Code = R"(
+    void target(int I) {
+      int &IRef = (I += 1);
+      // [[p]]
+    }
+  )";
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        EXPECT_EQ(&getLocForDecl(ASTCtx, Env, "IRef"),
+                  &getLocForDecl(ASTCtx, Env, "I"));
+      });
+}
+
 TEST(TransferTest, CannotAnalyzeFunctionTemplate) {
   std::string Code = R"(
     template <typename T>