PR45535: Check for variables with non-trivial destruction when

determining whether a statement expression has side-effects.

Author: zygoloid

clang/lib/AST/Expr.cpp

@@ -3270,6 +3270,26 @@ namespace {
 
     bool hasSideEffects() const { return HasSideEffects; }
 
+    void VisitDecl(const Decl *D) {
+      if (!D)
+        return;
+
+      // We assume the caller checks subexpressions (eg, the initializer, VLA
+      // bounds) for side-effects on our behalf.
+      if (auto *VD = dyn_cast<VarDecl>(D)) {
+        // Registering a destructor is a side-effect.
+        if (IncludePossibleEffects && VD->isThisDeclarationADefinition() &&
+            VD->needsDestruction(Context))
+          HasSideEffects = true;
+      }
+    }
+
+    void VisitDeclStmt(const DeclStmt *DS) {
+      for (auto *D : DS->decls())
+        VisitDecl(D);
+      Inherited::VisitDeclStmt(DS);
+    }
+
     void VisitExpr(const Expr *E) {
       if (!HasSideEffects &&
           E->HasSideEffects(Context, IncludePossibleEffects))

clang/test/CodeGenCXX/builtin-constant-p.cpp

@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -triple=x86_64-linux-gnu -emit-llvm -o - %s
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -emit-llvm -o - %s | FileCheck %s
 
 // Don't crash if the argument to __builtin_constant_p isn't scalar.
 template <typename T>
@@ -22,3 +22,27 @@ class numeric {
 bool bcp() {
   return is_constant(numeric<int>(1));
 }
+
+// PR45535
+struct with_dtor {
+  ~with_dtor();
+};
+// CHECK: define {{.*}}bcp_stmt_expr_1
+bool bcp_stmt_expr_1() {
+  // CHECK-NOT: call {{.*}}with_dtorD
+  return __builtin_constant_p(({with_dtor wd; 123;}));
+}
+
+int do_not_call();
+// CHECK: define {{.*}}bcp_stmt_expr_2
+bool bcp_stmt_expr_2(int n) {
+  // CHECK-NOT: call {{.*}}do_not_call
+  return __builtin_constant_p(({
+    // This has a side-effect due to the VLA bound, so CodeGen should fold it
+    // to false.
+    typedef int arr[do_not_call()];
+    n;
+  }));
+  // CHECK-NOT: }
+  // CHECK: ret i1 false
+}