[clang] 198fb5e - [clang][dataflow] Add captured parameters to ReferencedDecls for lamb… (#117771)

[via cfe-commits]

Author: Samira Bazuzi
Date: 2024-11-27T10:08:57-05:00
New Revision: 198fb5ed4ac7d096da03ea4a0a27832d18b1350f

URL: https://github.com/llvm/llvm-project/commit/198fb5ed4ac7d096da03ea4a0a27832d18b1350f
DIFF: https://github.com/llvm/llvm-project/commit/198fb5ed4ac7d096da03ea4a0a27832d18b1350f.diff

LOG: [clang][dataflow] Add captured parameters to ReferencedDecls for lamb… (#117771)

…da call operators.

This doesn't require that they be used in the operator's body, unlike
other ReferencedDecls. This is most obviously different from captured
local variables, which can be captured but will not appear in
ReferencedDecls unless they appear in the operator's body.

This difference simplifies the collection of the captured parameters,
but probably could be eliminated if desirable.

Added: 
    

Modified: 
    clang/include/clang/Analysis/FlowSensitive/ASTOps.h
    clang/lib/Analysis/FlowSensitive/ASTOps.cpp
    clang/unittests/Analysis/FlowSensitive/ASTOpsTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/Analysis/FlowSensitive/ASTOps.h b/clang/include/clang/Analysis/FlowSensitive/ASTOps.h
index 6294c810626a70..8c7ee86d15c069 100644
--- a/clang/include/clang/Analysis/FlowSensitive/ASTOps.h
+++ b/clang/include/clang/Analysis/FlowSensitive/ASTOps.h
@@ -146,6 +146,10 @@ struct ReferencedDecls {
   /// Free functions and member functions which are referenced (but not
   /// necessarily called).
   llvm::DenseSet<const FunctionDecl *> Functions;
+  /// When analyzing a lambda's call operator, the set of all parameters (from
+  /// the surrounding function) that the lambda captures. Captured local
+  /// variables are already included in `Locals` above.
+  llvm::DenseSet<const ParmVarDecl *> LambdaCapturedParams;
 };
 
 /// Returns declarations that are declared in or referenced from `FD`.

diff  --git a/clang/lib/Analysis/FlowSensitive/ASTOps.cpp b/clang/lib/Analysis/FlowSensitive/ASTOps.cpp
index 9e7821bfc1e89e..9a46e79cf4a676 100644
--- a/clang/lib/Analysis/FlowSensitive/ASTOps.cpp
+++ b/clang/lib/Analysis/FlowSensitive/ASTOps.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Analysis/FlowSensitive/ASTOps.h"
+#include "clang/AST/ASTLambda.h"
 #include "clang/AST/ComputeDependence.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
@@ -282,6 +283,28 @@ ReferencedDecls getReferencedDecls(const FunctionDecl &FD) {
   if (const auto *CtorDecl = dyn_cast<CXXConstructorDecl>(&FD))
     Visitor.traverseConstructorInits(CtorDecl);
 
+  // If analyzing a lambda call operator, collect all captures of parameters (of
+  // the surrounding function). This collects them even if they are not
+  // referenced in the body of the lambda call operator. Non-parameter local
+  // variables that are captured are already collected into
+  // `ReferencedDecls.Locals` when traversing the call operator body, but we
+  // collect parameters here to avoid needing to check at each referencing node
+  // whether the parameter is a lambda capture from a surrounding function or is
+  // a parameter of the current function. If it becomes necessary to limit this
+  // set to the parameters actually referenced in the body, alternative
+  // optimizations can be implemented to minimize duplicative work.
+  if (const auto *Method = dyn_cast<CXXMethodDecl>(&FD);
+      Method && isLambdaCallOperator(Method)) {
+    for (const auto &Capture : Method->getParent()->captures()) {
+      if (Capture.capturesVariable()) {
+        if (const auto *Param =
+                dyn_cast<ParmVarDecl>(Capture.getCapturedVar())) {
+          Result.LambdaCapturedParams.insert(Param);
+        }
+      }
+    }
+  }
+
   return Result;
 }
 

diff  --git a/clang/unittests/Analysis/FlowSensitive/ASTOpsTest.cpp b/clang/unittests/Analysis/FlowSensitive/ASTOpsTest.cpp
index 834aa7f4c2ac2e..e086ea3c892f16 100644
--- a/clang/unittests/Analysis/FlowSensitive/ASTOpsTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/ASTOpsTest.cpp
@@ -8,15 +8,23 @@
 
 #include "clang/Analysis/FlowSensitive/ASTOps.h"
 #include "TestingSupport.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/DeclCXX.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/LLVM.h"
+#include "clang/Frontend/ASTUnit.h"
+#include "clang/Tooling/Tooling.h"
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <memory>
+#include <string>
 
 namespace {
 
 using namespace clang;
 using namespace dataflow;
 
+using ast_matchers::cxxMethodDecl;
 using ast_matchers::cxxRecordDecl;
 using ast_matchers::hasName;
 using ast_matchers::hasType;
@@ -107,4 +115,37 @@ TEST(ASTOpsTest, ReferencedDeclsLocalsNotParamsOrStatics) {
               UnorderedElementsAre(LocalDecl));
 }
 
+TEST(ASTOpsTest, LambdaCaptures) {
+  std::string Code = R"cc(
+    void func(int CapturedByRef, int CapturedByValue, int NotCaptured) {
+    int Local;
+      auto Lambda = [&CapturedByRef, CapturedByValue, &Local](int LambdaParam) {
+      };
+    }
+  )cc";
+  std::unique_ptr<ASTUnit> Unit =
+      tooling::buildASTFromCodeWithArgs(Code, {"-fsyntax-only", "-std=c++17"});
+  auto &ASTCtx = Unit->getASTContext();
+
+  ASSERT_EQ(ASTCtx.getDiagnostics().getClient()->getNumErrors(), 0U);
+
+  auto *LambdaCallOp = selectFirst<CXXMethodDecl>(
+      "l", match(cxxMethodDecl(hasName("operator()")).bind("l"), ASTCtx));
+  ASSERT_NE(LambdaCallOp, nullptr);
+  auto *Func = cast<FunctionDecl>(findValueDecl(ASTCtx, "func"));
+  ASSERT_NE(Func, nullptr);
+  auto *CapturedByRefDecl = Func->getParamDecl(0);
+  ASSERT_NE(CapturedByRefDecl, nullptr);
+  auto *CapturedByValueDecl = Func->getParamDecl(1);
+  ASSERT_NE(CapturedByValueDecl, nullptr);
+
+  EXPECT_THAT(getReferencedDecls(*Func).LambdaCapturedParams, IsEmpty());
+  ReferencedDecls ForLambda = getReferencedDecls(*LambdaCallOp);
+  EXPECT_THAT(ForLambda.LambdaCapturedParams,
+              UnorderedElementsAre(CapturedByRefDecl, CapturedByValueDecl));
+  // Captured locals must be seen in the body for them to appear in
+  // ReferencedDecls.
+  EXPECT_THAT(ForLambda.Locals, IsEmpty());
+}
+
 } // namespace