[llvm-branch-commits] [clang] release/22.x: [C++20] [Modules] [Reduced BMI] Try not write merged lookup table (#186337) (PR #206421)
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Mon Jun 29 00:49:30 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: llvmbot
<details>
<summary>Changes</summary>
Backport 0e9f6532099fdcac69db142274c22fea29d062f6
Requested by: @<!-- -->ChuanqiXu9
---
Full diff: https://github.com/llvm/llvm-project/pull/206421.diff
3 Files Affected:
- (modified) clang/lib/Serialization/ASTWriter.cpp (+35-9)
- (modified) clang/test/Modules/no-transitive-decl-change-4.cppm (+1-1)
- (added) clang/test/Modules/pr184957.cppm (+216)
``````````diff
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 39104da10d0b7..1310848ba5d1d 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4603,7 +4603,16 @@ void ASTWriter::GenerateSpecializationInfoLookupTable(
Generator.insert(HashValue, Trait.getData(Specs, ExisitingSpecs), Trait);
}
- Generator.emit(LookupTable, Trait, Lookups ? &Lookups->Table : nullptr);
+ // Reduced BMI may not emit everything in the lookup table,
+ // If Reduced BMI **partially** emits some decls,
+ // then the generator may not emit the corresponding entry for the
+ // corresponding name is already there. See
+ // MultiOnDiskHashTableGenerator::insert and
+ // MultiOnDiskHashTableGenerator::emit for details.
+ // So we won't emit the lookup table if we're generating reduced BMI.
+ auto *ToEmitMaybeMergedLookupTable =
+ (!isGeneratingReducedBMI() && Lookups) ? &Lookups->Table : nullptr;
+ Generator.emit(LookupTable, Trait, ToEmitMaybeMergedLookupTable);
}
uint64_t ASTWriter::WriteSpecializationInfoLookupTable(
@@ -4800,7 +4809,16 @@ void ASTWriter::GenerateNameLookupTable(
// Create the on-disk hash table. Also emit the existing imported and
// merged table if there is one.
auto *Lookups = Chain ? Chain->getLoadedLookupTables(DC) : nullptr;
- Generator.emit(LookupTable, Trait, Lookups ? &Lookups->Table : nullptr);
+ // Reduced BMI may not emit everything in the lookup table,
+ // If Reduced BMI **partially** emits some decls,
+ // then the generator may not emit the corresponding entry for the
+ // corresponding name is already there. See
+ // MultiOnDiskHashTableGenerator::insert and
+ // MultiOnDiskHashTableGenerator::emit for details.
+ // So we won't emit the lookup table if we're generating reduced BMI.
+ auto *ToEmitMaybeMergedLookupTable =
+ (!isGeneratingReducedBMI() && Lookups) ? &Lookups->Table : nullptr;
+ Generator.emit(LookupTable, Trait, ToEmitMaybeMergedLookupTable);
const auto &ModuleLocalDecls = Trait.getModuleLocalDecls();
if (!ModuleLocalDecls.empty()) {
@@ -4816,11 +4834,15 @@ void ASTWriter::GenerateNameLookupTable(
ModuleLocalTrait);
}
+ // See the above comment. We won't emit the merged table if we're generating
+ // reduced BMI.
auto *ModuleLocalLookups =
- Chain ? Chain->getModuleLocalLookupTables(DC) : nullptr;
- ModuleLocalLookupGenerator.emit(
- ModuleLocalLookupTable, ModuleLocalTrait,
- ModuleLocalLookups ? &ModuleLocalLookups->Table : nullptr);
+ (isGeneratingReducedBMI() && Chain &&
+ Chain->getModuleLocalLookupTables(DC))
+ ? &Chain->getModuleLocalLookupTables(DC)->Table
+ : nullptr;
+ ModuleLocalLookupGenerator.emit(ModuleLocalLookupTable, ModuleLocalTrait,
+ ModuleLocalLookups);
}
const auto &TULocalDecls = Trait.getTULocalDecls();
@@ -4836,9 +4858,13 @@ void ASTWriter::GenerateNameLookupTable(
TULookupGenerator.insert(Key, TULocalTrait.getData(IDs), TULocalTrait);
}
- auto *TULocalLookups = Chain ? Chain->getTULocalLookupTables(DC) : nullptr;
- TULookupGenerator.emit(TULookupTable, TULocalTrait,
- TULocalLookups ? &TULocalLookups->Table : nullptr);
+ // See the above comment. We won't emit the merged table if we're generating
+ // reduced BMI.
+ auto *TULocalLookups =
+ (isGeneratingReducedBMI() && Chain && Chain->getTULocalLookupTables(DC))
+ ? &Chain->getTULocalLookupTables(DC)->Table
+ : nullptr;
+ TULookupGenerator.emit(TULookupTable, TULocalTrait, TULocalLookups);
}
}
diff --git a/clang/test/Modules/no-transitive-decl-change-4.cppm b/clang/test/Modules/no-transitive-decl-change-4.cppm
index 944878be8df63..bb7e47f32669e 100644
--- a/clang/test/Modules/no-transitive-decl-change-4.cppm
+++ b/clang/test/Modules/no-transitive-decl-change-4.cppm
@@ -27,7 +27,7 @@
// RUN: %clang_cc1 -std=c++20 -emit-reduced-module-interface %t/B.cppm -o %t/B.v1.pcm \
// RUN: -fprebuilt-module-path=%t -fmodule-file=AWrapper=%t/AWrapper.v1.pcm -fmodule-file=A=%t/A.v1.pcm
//
-// RUN: not diff %t/B.pcm %t/B.v1.pcm &> /dev/null
+// RUN: diff %t/B.pcm %t/B.v1.pcm &> /dev/null
//--- T.cppm
export module T;
diff --git a/clang/test/Modules/pr184957.cppm b/clang/test/Modules/pr184957.cppm
new file mode 100644
index 0000000000000..c08c10d978938
--- /dev/null
+++ b/clang/test/Modules/pr184957.cppm
@@ -0,0 +1,216 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: split-file %s %t
+// RUN: mkdir %t/tmp
+//
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std %t/wrap.std.tt.cppm -emit-reduced-module-interface -o %t/wrap.std.tt.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std %t/wrap.std.vec.cppm -emit-reduced-module-interface -o %t/wrap.std.vec.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std %t/not_std.cppm -emit-reduced-module-interface -o %t/not_std.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std %t/wrap.std.tt2.cppm -emit-reduced-module-interface -o %t/wrap.std.tt2.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std -fmodule-file=wrap.std.vec=%t/wrap.std.vec.pcm %t/wrap.std.vec.reexport.cppm -emit-reduced-module-interface -o %t/wrap.std.vec.reexport.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std -fmodule-file=wrap.std.tt=%t/wrap.std.tt.pcm -fmodule-file=wrap.std.vec=%t/wrap.std.vec.pcm -fmodule-file=wrap.std.vec.reexport=%t/wrap.std.vec.reexport.pcm -fmodule-file=wrap.std.tt2=%t/wrap.std.tt2.pcm -fmodule-file=not_std=%t/not_std.pcm %t/k.repro_dep.cppm -emit-reduced-module-interface -o %t/k.repro_dep.pcm
+// RUN: %clang_cc1 -std=c++23 -nostdinc++ -I %t/std -fmodule-file=wrap.std.tt=%t/wrap.std.tt.pcm -fmodule-file=wrap.std.vec=%t/wrap.std.vec.pcm -fmodule-file=wrap.std.tt2=%t/wrap.std.tt2.pcm -fmodule-file=wrap.std.vec.reexport=%t/wrap.std.vec.reexport.pcm -fmodule-file=not_std=%t/not_std.pcm -fmodule-file=k.repro_dep=%t/k.repro_dep.pcm %t/k.repro.cxx -fsyntax-only -verify
+
+//--- std/allocator.h
+#ifndef _LIBCPP___MEMORY_ALLOCATOR_H
+#define _LIBCPP___MEMORY_ALLOCATOR_H
+
+#include <size_t.h>
+
+namespace std {
+
+enum align_val_t { __zero = 0, __max = (size_t)-1 };
+
+template <class _Tp>
+inline _Tp*
+__libcpp_allocate(size_t __n, [[__maybe_unused__]] size_t __align = 8) {
+ size_t __size = static_cast<size_t>(__n) * sizeof(_Tp);
+ return static_cast<_Tp*>(__builtin_operator_new(__size, static_cast<align_val_t>(__align)));
+}
+
+template <class _Tp>
+class allocator
+{
+public:
+ typedef _Tp value_type;
+
+ [[__nodiscard__]] _Tp* allocate(size_t __n) {
+ if (__builtin_is_constant_evaluated()) {
+ return static_cast<_Tp*>(::operator new(__n * sizeof(_Tp)));
+ } else {
+ return std::__libcpp_allocate<_Tp>(size_t(__n));
+ }
+ }
+};
+
+template <class _Tp, class _Up>
+inline bool
+operator==(const allocator<_Tp>&, const allocator<_Up>&) noexcept {
+ return true;
+}
+
+}
+
+#endif // _LIBCPP___MEMORY_ALLOCATOR_H
+
+//--- std/sys_wchar.h
+#ifndef _WCHAR_H
+#define _WCHAR_H 1
+
+#ifndef __FILE_defined
+ #define __FILE_defined 1
+
+ struct _IO_FILE;
+
+ typedef struct _IO_FILE FILE;
+#endif
+
+#endif /* wchar.h */
+
+//--- std/char_traits.h
+#ifndef _LIBCPP___STRING_CHAR_TRAITS_H
+#define _LIBCPP___STRING_CHAR_TRAITS_H
+
+namespace std {
+
+template <class _Tp>
+inline size_t constexpr __constexpr_strlen(const _Tp* __str) noexcept {
+ if (__builtin_is_constant_evaluated()) {
+ size_t __i = 0;
+ for (; __str[__i] != '\0'; ++__i)
+ ;
+ return __i;
+ }
+ return 0;
+}
+
+template <class _CharT>
+struct char_traits;
+
+template <>
+struct char_traits<char> {
+ using char_type = char;
+
+ [[__nodiscard__]] static inline size_t constexpr
+ length(const char_type* __s) noexcept {
+ return std::__constexpr_strlen(__s);
+ }
+};
+
+}
+
+#endif // _LIBCPP___STRING_CHAR_TRAITS_H
+
+//--- std/type_traits
+#ifndef _LIBCPP_TYPE_TRAITS
+#define _LIBCPP_TYPE_TRAITS
+
+namespace std
+{}
+
+#endif // _LIBCPP_TYPE_TRAITS
+
+//--- std/ptrdiff_t.h
+#ifndef _LIBCPP___CSTDDEF_PTRDIFF_T_H
+#define _LIBCPP___CSTDDEF_PTRDIFF_T_H
+
+namespace std {
+
+using ptrdiff_t = decltype(static_cast<int*>(nullptr) - static_cast<int*>(nullptr));
+
+}
+
+#endif // _LIBCPP___CSTDDEF_PTRDIFF_T_H
+
+//--- std/size_t.h
+#ifndef _LIBCPP___CSTDDEF_SIZE_T_H
+#define _LIBCPP___CSTDDEF_SIZE_T_H
+
+namespace std {
+
+using size_t = decltype(sizeof(int));
+
+}
+
+#endif // _LIBCPP___CSTDDEF_SIZE_T_H
+
+//--- wrap.std.tt.cppm
+module;
+
+#include <type_traits>
+
+export module wrap.std.tt;
+
+//--- wrap.std.vec.cppm
+module;
+
+#include <allocator.h>
+#include <sys_wchar.h>
+
+export module wrap.std.vec;
+
+//--- not_std.cppm
+module;
+
+#include <allocator.h>
+
+
+export module not_std;
+
+namespace std {
+ template <class _Tp, class _Allocator>
+ class __split_buffer {
+ public:
+ __split_buffer() {
+ _Allocator a;
+ (void)a.allocate(1);
+ }
+ };
+}
+
+export namespace std {
+ template <typename T>
+ using problem = std::__split_buffer<T, std::allocator<T>>;
+}
+
+export using ::operator new;
+
+//--- wrap.std.tt2.cppm
+module;
+
+#include <type_traits>
+
+export module wrap.std.tt2;
+
+//--- wrap.std.vec.reexport.cppm
+export module wrap.std.vec.reexport;
+
+export import wrap.std.vec;
+
+//--- k.repro_dep.cppm
+module;
+
+#include <allocator.h>
+#include <sys_wchar.h>
+#include <char_traits.h>
+
+export module k.repro_dep;
+
+import wrap.std.tt;
+import wrap.std.vec.reexport;
+import wrap.std.vec;
+import wrap.std.tt2;
+
+import not_std;
+
+using XYZ = std::char_traits<char>;
+
+//--- k.repro.cxx
+// expected-no-diagnostics
+import not_std;
+import k.repro_dep;
+
+auto f() -> void
+{
+ std::problem< int > x;
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/206421
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