[clang] [clang analysis] ExprMutationAnalyzer support recursive forwarding reference (PR #87954)

via cfe-commits cfe-commits at lists.llvm.org
Sun Apr 7 18:43:04 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Congcong Cai (HerrCai0907)

<details>
<summary>Changes</summary>

Partialy fixes: #<!-- -->60895


---
Full diff: https://github.com/llvm/llvm-project/pull/87954.diff


3 Files Affected:

- (modified) clang/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h (+33-7) 
- (modified) clang/lib/Analysis/ExprMutationAnalyzer.cpp (+14-8) 
- (modified) clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp (+30) 


``````````diff
diff --git a/clang/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h b/clang/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h
index 1ceef944fbc34e..af6106fe303afd 100644
--- a/clang/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h
+++ b/clang/include/clang/Analysis/Analyses/ExprMutationAnalyzer.h
@@ -8,11 +8,10 @@
 #ifndef LLVM_CLANG_ANALYSIS_ANALYSES_EXPRMUTATIONANALYZER_H
 #define LLVM_CLANG_ANALYSIS_ANALYSES_EXPRMUTATIONANALYZER_H
 
-#include <type_traits>
-
 #include "clang/AST/AST.h"
 #include "clang/ASTMatchers/ASTMatchers.h"
 #include "llvm/ADT/DenseMap.h"
+#include <variant>
 
 namespace clang {
 
@@ -22,8 +21,15 @@ class FunctionParmMutationAnalyzer;
 /// a given statement.
 class ExprMutationAnalyzer {
 public:
+  friend class FunctionParmMutationAnalyzer;
+  struct Cache {
+    llvm::DenseMap<const FunctionDecl *,
+                   std::unique_ptr<FunctionParmMutationAnalyzer>>
+        FuncParmAnalyzer;
+  };
+
   ExprMutationAnalyzer(const Stmt &Stm, ASTContext &Context)
-      : Stm(Stm), Context(Context) {}
+      : ExprMutationAnalyzer(Stm, Context, nullptr) {}
 
   bool isMutated(const Expr *Exp) { return findMutation(Exp) != nullptr; }
   bool isMutated(const Decl *Dec) { return findMutation(Dec) != nullptr; }
@@ -45,6 +51,19 @@ class ExprMutationAnalyzer {
   using MutationFinder = const Stmt *(ExprMutationAnalyzer::*)(const Expr *);
   using ResultMap = llvm::DenseMap<const Expr *, const Stmt *>;
 
+  ExprMutationAnalyzer(const Stmt &Stm, ASTContext &Context, Cache *ParentCache)
+      : Stm(Stm), Context(Context) {
+    if (ParentCache != nullptr) {
+      CrossAnalysisCache = ParentCache;
+    } else {
+      CrossAnalysisCache = std::make_unique<Cache>();
+    }
+  }
+  ExprMutationAnalyzer(const Stmt &Stm, ASTContext &Context,
+                       std::unique_ptr<Cache> CrossAnalysisCache)
+      : Stm(Stm), Context(Context),
+        CrossAnalysisCache(std::move(CrossAnalysisCache)) {}
+
   const Stmt *findMutationMemoized(const Expr *Exp,
                                    llvm::ArrayRef<MutationFinder> Finders,
                                    ResultMap &MemoizedResults);
@@ -67,11 +86,15 @@ class ExprMutationAnalyzer {
   const Stmt *findReferenceMutation(const Expr *Exp);
   const Stmt *findFunctionArgMutation(const Expr *Exp);
 
+  Cache *getCache() {
+    return std::holds_alternative<Cache *>(CrossAnalysisCache)
+               ? std::get<Cache *>(CrossAnalysisCache)
+               : std::get<std::unique_ptr<Cache>>(CrossAnalysisCache).get();
+  }
+
   const Stmt &Stm;
   ASTContext &Context;
-  llvm::DenseMap<const FunctionDecl *,
-                 std::unique_ptr<FunctionParmMutationAnalyzer>>
-      FuncParmAnalyzer;
+  std::variant<Cache *, std::unique_ptr<Cache>> CrossAnalysisCache;
   ResultMap Results;
   ResultMap PointeeResults;
 };
@@ -80,7 +103,10 @@ class ExprMutationAnalyzer {
 // params.
 class FunctionParmMutationAnalyzer {
 public:
-  FunctionParmMutationAnalyzer(const FunctionDecl &Func, ASTContext &Context);
+  FunctionParmMutationAnalyzer(const FunctionDecl &Func, ASTContext &Context)
+      : FunctionParmMutationAnalyzer(Func, Context, nullptr) {}
+  FunctionParmMutationAnalyzer(const FunctionDecl &Func, ASTContext &Context,
+                               ExprMutationAnalyzer::Cache *CrossAnalysisCache);
 
   bool isMutated(const ParmVarDecl *Parm) {
     return findMutation(Parm) != nullptr;
diff --git a/clang/lib/Analysis/ExprMutationAnalyzer.cpp b/clang/lib/Analysis/ExprMutationAnalyzer.cpp
index bb042760d297a7..dba6f2a3c02112 100644
--- a/clang/lib/Analysis/ExprMutationAnalyzer.cpp
+++ b/clang/lib/Analysis/ExprMutationAnalyzer.cpp
@@ -638,9 +638,10 @@ const Stmt *ExprMutationAnalyzer::findFunctionArgMutation(const Expr *Exp) {
       if (!RefType->getPointeeType().getQualifiers() &&
           RefType->getPointeeType()->getAs<TemplateTypeParmType>()) {
         std::unique_ptr<FunctionParmMutationAnalyzer> &Analyzer =
-            FuncParmAnalyzer[Func];
+            getCache()->FuncParmAnalyzer[Func];
         if (!Analyzer)
-          Analyzer.reset(new FunctionParmMutationAnalyzer(*Func, Context));
+          Analyzer.reset(
+              new FunctionParmMutationAnalyzer(*Func, Context, getCache()));
         if (Analyzer->findMutation(Parm))
           return Exp;
         continue;
@@ -653,13 +654,15 @@ const Stmt *ExprMutationAnalyzer::findFunctionArgMutation(const Expr *Exp) {
 }
 
 FunctionParmMutationAnalyzer::FunctionParmMutationAnalyzer(
-    const FunctionDecl &Func, ASTContext &Context)
-    : BodyAnalyzer(*Func.getBody(), Context) {
+    const FunctionDecl &Func, ASTContext &Context,
+    ExprMutationAnalyzer::Cache *CrossAnalysisCache)
+    : BodyAnalyzer(*Func.getBody(), Context, CrossAnalysisCache) {
   if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(&Func)) {
     // CXXCtorInitializer might also mutate Param but they're not part of
     // function body, check them eagerly here since they're typically trivial.
     for (const CXXCtorInitializer *Init : Ctor->inits()) {
-      ExprMutationAnalyzer InitAnalyzer(*Init->getInit(), Context);
+      ExprMutationAnalyzer InitAnalyzer(*Init->getInit(), Context,
+                                        CrossAnalysisCache);
       for (const ParmVarDecl *Parm : Ctor->parameters()) {
         if (Results.contains(Parm))
           continue;
@@ -675,11 +678,14 @@ FunctionParmMutationAnalyzer::findMutation(const ParmVarDecl *Parm) {
   const auto Memoized = Results.find(Parm);
   if (Memoized != Results.end())
     return Memoized->second;
-
+  // To handle call A -> call B -> call A. Assume parameters of A is not mutated
+  // before analyzing parameters of A. Then when analyzing the second "call A",
+  // FunctionParmMutationAnalyzer can use this memoized value to avoid infinite
+  // recursion.
+  Results[Parm] = nullptr;
   if (const Stmt *S = BodyAnalyzer.findMutation(Parm))
     return Results[Parm] = S;
-
-  return Results[Parm] = nullptr;
+  return Results[Parm];
 }
 
 } // namespace clang
diff --git a/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp b/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
index f58ce4aebcbfc8..9c1dc1a76db63d 100644
--- a/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
+++ b/clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp
@@ -977,6 +977,36 @@ TEST(ExprMutationAnalyzerTest, FollowFuncArgModified) {
                          "void f() { int x; g(x); }");
   Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
   EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("g(x)"));
+
+  AST = buildASTFromCode(
+      StdRemoveReference + StdForward +
+      "template <class T> void f1(T &&a);"
+      "template <class T> void f2(T &&a);"
+      "template <class T> void f1(T &&a) { f2<T>(std::forward<T>(a)); }"
+      "template <class T> void f2(T &&a) { f1<T>(std::forward<T>(a)); }"
+      "void f() { int x; f1(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_FALSE(isMutated(Results, AST.get()));
+
+  AST = buildASTFromCode(
+      StdRemoveReference + StdForward +
+      "template <class T> void f1(T &&a);"
+      "template <class T> void f2(T &&a);"
+      "template <class T> void f1(T &&a) { f2<T>(std::forward<T>(a)); }"
+      "template <class T> void f2(T &&a) { f1<T>(std::forward<T>(a)); a++; }"
+      "void f() { int x; f1(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("f1(x)"));
+
+  AST = buildASTFromCode(
+      StdRemoveReference + StdForward +
+      "template <class T> void f1(T &&a);"
+      "template <class T> void f2(T &&a);"
+      "template <class T> void f1(T &&a) { f2<T>(std::forward<T>(a)); a++; }"
+      "template <class T> void f2(T &&a) { f1<T>(std::forward<T>(a)); }"
+      "void f() { int x; f1(x); }");
+  Results = match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_THAT(mutatedBy(Results, AST.get()), ElementsAre("f1(x)"));
 }
 
 TEST(ExprMutationAnalyzerTest, FollowFuncArgNotModified) {

``````````

</details>


https://github.com/llvm/llvm-project/pull/87954


More information about the cfe-commits mailing list