[llvm-branch-commits] [clang] dceeb0d - Revert "[Serialization] Stop demote var definition as declaration (#172430)"

[via llvm-branch-commits]

Author: Jordan Rupprecht
Date: 2026-01-16T11:54:06-06:00
New Revision: dceeb0d22340d089ea788abc8b17671dad13f5c0

URL: https://github.com/llvm/llvm-project/commit/dceeb0d22340d089ea788abc8b17671dad13f5c0
DIFF: https://github.com/llvm/llvm-project/commit/dceeb0d22340d089ea788abc8b17671dad13f5c0.diff

LOG: Revert "[Serialization] Stop demote var definition as declaration (#172430)"

This reverts commit c560f1cf03aa06c0bdd00c5a9b558c16d882af6f.

Added: 
    

Modified: 
    clang/lib/Serialization/ASTReaderDecl.cpp

Removed: 
    clang/test/Modules/pr149404-02.cppm
    clang/test/Modules/pr172241.cppm


################################################################################
diff  --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index f0fb247f1afb9..f8e9caa3f5d1d 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -3642,9 +3642,23 @@ template<>
 void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
                                            Redeclarable<VarDecl> *D,
                                            Decl *Previous, Decl *Canon) {
+  auto *VD = static_cast<VarDecl *>(D);
   auto *PrevVD = cast<VarDecl>(Previous);
   D->RedeclLink.setPrevious(PrevVD);
   D->First = PrevVD->First;
+
+  // We should keep at most one definition on the chain.
+  // FIXME: Cache the definition once we've found it. Building a chain with
+  // N definitions currently takes O(N^2) time here.
+  if (VD->isThisDeclarationADefinition() == VarDecl::Definition) {
+    for (VarDecl *CurD = PrevVD; CurD; CurD = CurD->getPreviousDecl()) {
+      if (CurD->isThisDeclarationADefinition() == VarDecl::Definition) {
+        Reader.mergeDefinitionVisibility(CurD, VD);
+        VD->demoteThisDefinitionToDeclaration();
+        break;
+      }
+    }
+  }
 }
 
 static bool isUndeducedReturnType(QualType T) {

diff  --git a/clang/test/Modules/pr149404-02.cppm b/clang/test/Modules/pr149404-02.cppm
deleted file mode 100644
index 291619ea05b8a..0000000000000
--- a/clang/test/Modules/pr149404-02.cppm
+++ /dev/null
@@ -1,104 +0,0 @@
-// RUN: rm -rf %t
-// RUN: mkdir -p %t
-// RUN: split-file %s %t
-
-// RUN: %clang_cc1 -std=c++20 -emit-module-interface -o %t/format.pcm %t/format.cppm
-// RUN: %clang_cc1 -std=c++20  -emit-module-interface -o %t/includes_in_gmf.pcm %t/includes_in_gmf.cppm
-// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %t/test.cpp -verify -fsyntax-only
-
-// RUN: %clang_cc1 -std=c++20 -emit-reduced-module-interface -o %t/format.pcm %t/format.cppm
-// RUN: %clang_cc1 -std=c++20  -emit-reduced-module-interface -o %t/includes_in_gmf.pcm %t/includes_in_gmf.cppm
-// RUN: %clang_cc1 -std=c++20 -fprebuilt-module-path=%t %t/test.cpp -verify -fsyntax-only
-
-//--- format.h
-#pragma once
-
-namespace test {
-
-template <class _Tp>
-struct type_identity {
-    typedef _Tp type;
-};
-
-template <class _Tp>
-using type_identity_t = typename type_identity<_Tp>::type;
-
-
-template <class _Tp, class _CharT>
-struct formatter
-{
-    formatter() = delete;
-};
-
-template <>
-struct formatter<char, char>
-{};
-
-template <class _CharT, class... _Args>
-struct basic_format_string {
-    static inline const int __handles_{ [] {
-        formatter<char, _CharT> f;
-        (void)f;
-        return 0;
-        }() };
-    
-    consteval basic_format_string(const _CharT*) {
-        (void)__handles_;
-    }
-};
-
-template <class... _Args>
-using wformat_string = basic_format_string<wchar_t, type_identity_t<_Args>...>;
-
-template <class... _Args>
-using format_string = basic_format_string<char, type_identity_t<_Args>...>;
-
-template <class... _Args>
-void format(format_string<_Args...> __fmt, _Args&&... __args) {}
-
-template <class... _Args>
-void format(wformat_string<_Args...> __fmt, _Args&&... __args) {}
-
-}
-
-//--- format.cppm
-module;
-#include "format.h"
-export module format;
-
-export namespace test {
-	using test::format;
-	using test::formatter;
-	using test::format_string;
-}
-
-auto something() -> void
-{
-	auto a = 'a';
-	test::format("{}", a);
-}
-
-//--- includes_in_gmf.cppm
-module;
-#include "format.h"
-export module includes_in_gmf;
-
-namespace test {
-	using test::format;
-	using test::formatter;
-	using test::format_string;
-}
-
-//--- test.cpp
-// expected-no-diagnostics
-import format;
-import includes_in_gmf;
-
-auto what() -> void
-{
-    auto a = 'a';
-    test::format("{}", a);
-
-    constexpr auto fs = "{}"; // test::format_string<char>{ "{}" }; // <- same result even passing exact param type
-    test::format(fs, 'r');
-}

diff  --git a/clang/test/Modules/pr172241.cppm b/clang/test/Modules/pr172241.cppm
deleted file mode 100644
index 3eb885e8b2d9f..0000000000000
--- a/clang/test/Modules/pr172241.cppm
+++ /dev/null
@@ -1,47 +0,0 @@
-// RUN: rm -rf %t
-// RUN: mkdir -p %t
-// RUN: split-file %s %t
-//
-// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/m.cppm -emit-module-interface -o %t/m.pcm
-// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/use.cpp -fmodule-file=m=%t/m.pcm -emit-llvm -o - | FileCheck %t/use.cpp
-//
-// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/m.cppm -emit-reduced-module-interface -o %t/m.pcm
-// RUN: %clang_cc1 -std=c++20 -triple %itanium_abi_triple %t/use.cpp -fmodule-file=m=%t/m.pcm -emit-llvm -o - | FileCheck %t/use.cpp
-
-//--- header.h
-#pragma once
-
-template <unsigned T>
-class Templ {
-public:
-    void lock() { __set_locked_bit(); }
-
-private:
-    static constexpr auto __set_locked_bit = [](){};
-};
-
-class JT {
-public:
-    ~JT() {
-        Templ<4> state;
-        state.lock();
-    }
-};
-
-//--- m.cppm
-module;
-#include "header.h"
-export module m;
-export struct M {
-    JT jt;
-};
-//--- use.cpp
-#include "header.h"
-import m;
-
-int main() {
-    M m;
-    return 0;
-}
-
-// CHECK: @_ZN5TemplILj4EE16__set_locked_bitE = {{.*}}linkonce_odr