[clang] [PATCH] [clang][modules] Fix serialization and de-serialization of PCH module file refs (#105994) (PR #132802)

[Paul Schwabauer via cfe-commits]

https://github.com/koplas updated https://github.com/llvm/llvm-project/pull/132802

>From 2d143ca15476df04063e9e7e2c5fd1938c4f705b Mon Sep 17 00:00:00 2001
From: koplas <paul at schwabauer.co>
Date: Mon, 24 Mar 2025 19:20:52 +0100
Subject: [PATCH 1/2] [PATCH] [clang][modules] Fix serialization and
 de-serialization of PCH module file refs  (#105994)

Co-authored-by: ShaderKeeper <no-reply at shaderkeeper.com>
---
 clang/lib/Serialization/ASTReader.cpp        |  4 +-
 clang/test/Modules/MixedModulePrecompile.cpp | 63 ++++++++++++++++++++
 2 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Modules/MixedModulePrecompile.cpp

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 2728e93c69516..7540ff5a3a95c 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -9615,7 +9615,7 @@ ModuleFile *ASTReader::getLocalModuleFile(ModuleFile &M, unsigned ID) const {
     // It's a prefix (preamble, PCH, ...). Look it up by index.
     unsigned IndexFromEnd = ID >> 1;
     assert(IndexFromEnd && "got reference to unknown module file");
-    return getModuleManager().pch_modules().end()[-IndexFromEnd];
+    return getModuleManager().pch_modules().end()[-static_cast<int>(IndexFromEnd)];
   }
 }
 
@@ -9633,7 +9633,7 @@ unsigned ASTReader::getModuleFileID(ModuleFile *M) {
   auto PCHModules = getModuleManager().pch_modules();
   auto I = llvm::find(PCHModules, M);
   assert(I != PCHModules.end() && "emitting reference to unknown file");
-  return (I - PCHModules.end()) << 1;
+  return std::distance(I, PCHModules.end()) << 1;
 }
 
 std::optional<ASTSourceDescriptor> ASTReader::getSourceDescriptor(unsigned ID) {
diff --git a/clang/test/Modules/MixedModulePrecompile.cpp b/clang/test/Modules/MixedModulePrecompile.cpp
new file mode 100644
index 0000000000000..473817ef71de6
--- /dev/null
+++ b/clang/test/Modules/MixedModulePrecompile.cpp
@@ -0,0 +1,63 @@
+// Tests mixed usage of precompiled headers and modules.
+//
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -std=c++20 -x c++-header -emit-pch %t/a.hpp \
+// RUN: -o %t/a.pch
+
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/Part1.cppm \
+// RUN: -include-pch %t/a.pch -o %t/Part1.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/Part2.cppm \
+// RUN: -include-pch %t/a.pch -o %t/Part2.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/Part3.cppm \
+// RUN: -include-pch %t/a.pch -o %t/Part3.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/Part4.cppm \
+// RUN: -include-pch %t/a.pch -o %t/Part4.pcm
+
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface \
+// RUN: -fmodule-file=mod:part1=%t/Part1.pcm \
+// RUN: -fmodule-file=mod:part2=%t/Part2.pcm \
+// RUN: -fmodule-file=mod:part3=%t/Part3.pcm \
+// RUN: -fmodule-file=mod:part4=%t/Part4.pcm \
+// RUN: %t/Mod.cppm \
+// RUN: -include-pch %t/a.pch -o %t/Mod.pcm
+
+// RUN: %clang_cc1 -std=c++20 -emit-obj \
+// RUN: -main-file-name Mod.cppm \
+// RUN: -fmodule-file=mod:part1=%t/Part1.pcm \
+// RUN: -fmodule-file=mod:part2=%t/Part2.pcm \
+// RUN: -fmodule-file=mod:part3=%t/Part3.pcm \
+// RUN: -fmodule-file=mod:part4=%t/Part4.pcm \
+// RUN: -x pcm %t/Mod.pcm \
+// RUN: -include-pch %t/a.pch -o %t/Mod.o
+
+
+//--- a.hpp
+#pragma once
+
+class a {
+  virtual ~a();
+  a() {}
+};
+
+//--- Part1.cppm
+export module mod:part1;
+
+//--- Part2.cppm
+export module mod:part2;
+
+//--- Part3.cppm
+export module mod:part3;
+
+//--- Part4.cppm
+export module mod:part4;
+
+//--- Mod.cppm
+export module mod;
+export import :part1;
+export import :part2;
+export import :part3;
+export import :part4;
+

>From 5dff7f9854c412f803d9b3e1931612f2dd2192f6 Mon Sep 17 00:00:00 2001
From: Paul Schwabauer <pschwabauer at intevation.de>
Date: Tue, 25 Mar 2025 06:18:28 +0100
Subject: [PATCH 2/2] Address comment

Co-authored-by: Chuanqi Xu <yedeng.yd at linux.alibaba.com>
---
 clang/lib/Serialization/ASTReader.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 7540ff5a3a95c..0cd2cedb48dd9 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -9613,7 +9613,7 @@ ModuleFile *ASTReader::getLocalModuleFile(ModuleFile &M, unsigned ID) const {
     return I == GlobalSubmoduleMap.end() ? nullptr : I->second;
   } else {
     // It's a prefix (preamble, PCH, ...). Look it up by index.
-    unsigned IndexFromEnd = ID >> 1;
+   int IndexFromEnd = static_cast<int>(ID >> 1);
     assert(IndexFromEnd && "got reference to unknown module file");
     return getModuleManager().pch_modules().end()[-static_cast<int>(IndexFromEnd)];
   }