[PATCH] D145886: [C++2x][Modules] Amend module purview constant linkage [P2788R0].

[Iain Sandoe via Phabricator via cfe-commits]

iains created this revision.
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iains added a reviewer: ChuanqiXu.
iains updated this revision to Diff 504524.
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iains updated this revision to Diff 504591.
iains added a reviewer: rsmith.
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rebase, remove use of fmodule-file=X=path to attempt to resolve Windows fail.


iains added a comment.

rebased, try to fix Windows CI, take 2.


iains added a comment.

I should definitely check to make sure that this was adopted as a DR against C++20 (otherwise we would need to use the previous test conditionally on < 2b).


This paper has been applied to the working draft and is believed to be
a DR against C++20, so that the patch here makes the change unconditionally.

for:

  export module A;
  
  const int mod_cst = 10;

Before the change, mod_cst would have internal linkage; after the change it
has module linkage.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D145886

Files:
  clang/lib/AST/Decl.cpp
  clang/test/CXX/module/basic/basic.def.odr/p4.cppm
  clang/test/CXX/module/basic/basic.link/p3.cppm


Index: clang/test/CXX/module/basic/basic.link/p3.cppm
===================================================================
--- clang/test/CXX/module/basic/basic.link/p3.cppm
+++ clang/test/CXX/module/basic/basic.link/p3.cppm
@@ -3,7 +3,7 @@
 
 export module M;
 
-// CHECK-NOT: @_ZW1M1a ={{.*}}
+// CHECK: @_ZW1M1a ={{.*}} constant i32 1
 const int a = 1;
 // CHECK: @_ZW1M1b ={{.*}} constant i32 2
 export const int b = 2;
Index: clang/test/CXX/module/basic/basic.def.odr/p4.cppm
===================================================================
--- clang/test/CXX/module/basic/basic.def.odr/p4.cppm
+++ clang/test/CXX/module/basic/basic.def.odr/p4.cppm
@@ -5,9 +5,9 @@
 // RUN: %clang_cc1 -std=c++20 %t/Module.cppm -triple %itanium_abi_triple -emit-llvm -o - | FileCheck %t/Module.cppm --implicit-check-not unused
 //
 // RUN: %clang_cc1 -std=c++20 %t/Module.cppm -triple %itanium_abi_triple -emit-module-interface -o %t/Module.pcm
-// RUN: %clang_cc1 -std=c++20 %t/module.cpp -triple %itanium_abi_triple -fmodule-file=%t/Module.pcm -emit-llvm -o - | FileCheck %t/module.cpp --implicit-check-not=unused --implicit-check-not=global_module
+// RUN: %clang_cc1 -std=c++20 %t/module.cpp -triple %itanium_abi_triple -fmodule-file=Module=%t/Module.pcm -emit-llvm -o - | FileCheck %t/module.cpp --implicit-check-not=unused --implicit-check-not=global_module
 //
-// RUN: %clang_cc1 -std=c++20 %t/user.cpp -triple %itanium_abi_triple -fmodule-file=%t/Module.pcm -emit-llvm -o - | FileCheck %t/user.cpp --implicit-check-not=unused --implicit-check-not=global_module
+// RUN: %clang_cc1 -std=c++20 %t/user.cpp -triple %itanium_abi_triple -fmodule-file=Module=%t/Module.pcm -emit-llvm -o - | FileCheck %t/user.cpp --implicit-check-not=unused --implicit-check-not=global_module
 
 //--- Module.cppm
 // CHECK-DAG: @extern_var_global_module = external {{(dso_local )?}}global
@@ -30,7 +30,7 @@
 // permitted to run the initializer for this variable.
 // CHECK-DAG: @_ZW6Module25inline_var_module_linkage = linkonce_odr {{(dso_local )?}}global
 // CHECK-DAG: @_ZL25static_var_module_linkage = internal
-// CHECK-DAG: @_ZL24const_var_module_linkage = internal
+// CHECK-DAG: @_ZW6Module24const_var_module_linkage = {{(dso_local )?}}constant
 //
 // CHECK-DAG: @_ZW6Module25unused_var_module_linkage = {{(dso_local )?}}global i32 4
 
@@ -129,7 +129,7 @@
 // CHECK-DAG: @_ZW6Module25extern_var_module_linkage = external {{(dso_local )?}}global
 // CHECK-DAG: @_ZW6Module25inline_var_module_linkage = linkonce_odr {{(dso_local )?}}global
 // CHECK-DAG: @_ZL25static_var_module_linkage = internal {{(dso_local )?}}global i32 0,
-// CHECK-DAG: @_ZL24const_var_module_linkage = internal {{(dso_local )?}}constant i32 3,
+// CHECK-DAG: @_ZW6Module24const_var_module_linkage = available_externally {{(dso_local )?}}constant i32 3,
 
 module Module;
 
Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -600,6 +600,12 @@
   llvm_unreachable("unexpected module ownership kind");
 }
 
+static bool isDeclaredInModuleInterfaceOrPartition(const NamedDecl *D) {
+  if (auto *M = D->getOwningModule())
+    return M->isInterfaceOrPartition();
+  return false;
+}
+
 static LinkageInfo getInternalLinkageFor(const NamedDecl *D) {
   return LinkageInfo::internal();
 }
@@ -642,15 +648,15 @@
   if (const auto *Var = dyn_cast<VarDecl>(D)) {
     // - a non-template variable of non-volatile const-qualified type, unless
     //   - it is explicitly declared extern, or
-    //   - it is inline or exported, or
+    //   - it is declared in the purview of a module interface unit
+    //     (outside the private-module-fragment, if any) or module partition, or
+    //   - it is inline, or
     //   - it was previously declared and the prior declaration did not have
     //     internal linkage
     // (There is no equivalent in C99.)
-    if (Context.getLangOpts().CPlusPlus &&
-        Var->getType().isConstQualified() &&
-        !Var->getType().isVolatileQualified() &&
-        !Var->isInline() &&
-        !isExportedFromModuleInterfaceUnit(Var) &&
+    if (Context.getLangOpts().CPlusPlus && Var->getType().isConstQualified() &&
+        !Var->getType().isVolatileQualified() && !Var->isInline() &&
+        !isDeclaredInModuleInterfaceOrPartition(Var) &&
         !isa<VarTemplateSpecializationDecl>(Var) &&
         !Var->getDescribedVarTemplate()) {
       const VarDecl *PrevVar = Var->getPreviousDecl();


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