Decouple dllexport/dllimport from linkage

Representing dllexport/dllimport as distinct linkage types prevents using
these attributes on templates and inline functions.

Instead of introducing further mixed linkage types to include linkonce and
weak ODR, the old import/export linkage types are replaced with a new
separate visibility-like specifier:

  define available_externally dllimport void @f() {}
  @Var = dllexport global i32 1, align 4

Linkage for dllexported globals and functions is now equal to their linkage
without dllexport. Imported globals and functions must be either
declarations with external linkage, or definitions with
AvailableExternallyLinkage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199204 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 14 deletions

diff --git a/include/llvm-c/Core.h b/include/llvm-c/Core.h
index 269869ef0d..a84a031321 100644
--- a/include/llvm-c/Core.h
+++ b/include/llvm-c/Core.h
@@ -284,8 +284,8 @@ typedef enum {
   LLVMInternalLinkage,    /**< Rename collisions when linking (static
                                functions) */
   LLVMPrivateLinkage,     /**< Like Internal, but omit from symbol table */
-  LLVMDLLImportLinkage,   /**< Function to be imported from DLL */
-  LLVMDLLExportLinkage,   /**< Function to be accessible from DLL */
+  LLVMDLLImportLinkage,   /**< Obsolete */
+  LLVMDLLExportLinkage,   /**< Obsolete */
   LLVMExternalWeakLinkage,/**< ExternalWeak linkage description */
   LLVMGhostLinkage,       /**< Obsolete */
   LLVMCommonLinkage,      /**< Tentative definitions */
diff --git a/include/llvm/IR/GlobalValue.h b/include/llvm/IR/GlobalValue.h
index 4f20a31a29..5fdf6611e9 100644
--- a/include/llvm/IR/GlobalValue.h
+++ b/include/llvm/IR/GlobalValue.h
@@ -42,8 +42,6 @@ public:
     PrivateLinkage,     ///< Like Internal, but omit from symbol table.
     LinkerPrivateLinkage, ///< Like Private, but linker removes.
     LinkerPrivateWeakLinkage, ///< Like LinkerPrivate, but weak.
-    DLLImportLinkage,   ///< Function to be imported from DLL
-    DLLExportLinkage,   ///< Function to be accessible from DLL.
     ExternalWeakLinkage,///< ExternalWeak linkage description.
     CommonLinkage       ///< Tentative definitions.
   };
@@ -55,11 +53,19 @@ public:
     ProtectedVisibility     ///< The GV is protected
   };
 
+  /// @brief Storage classes of global values for PE targets.
+  enum DLLStorageClassTypes {
+    DefaultStorageClass   = 0,
+    DLLImportStorageClass = 1, ///< Function to be imported from DLL
+    DLLExportStorageClass = 2  ///< Function to be accessible from DLL.
+  };
+
 protected:
   GlobalValue(Type *ty, ValueTy vty, Use *Ops, unsigned NumOps,
               LinkageTypes linkage, const Twine &Name)
     : Constant(ty, vty, Ops, NumOps), Linkage(linkage),
-      Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0), Parent(0) {
+      Visibility(DefaultVisibility), Alignment(0), UnnamedAddr(0),
+      DllStorageClass(DefaultStorageClass), Parent(0) {
     setName(Name);
   }
 
@@ -69,6 +75,7 @@ protected:
   unsigned Visibility : 2;    // The visibility style of this global
   unsigned Alignment : 16;    // Alignment of this symbol, must be power of two
   unsigned UnnamedAddr : 1;   // This value's address is not significant
+  unsigned DllStorageClass : 2; // DLL storage class
   Module *Parent;             // The containing module.
   std::string Section;        // Section to emit this into, empty mean default
 public:
@@ -91,7 +98,18 @@ public:
     return Visibility == ProtectedVisibility;
   }
   void setVisibility(VisibilityTypes V) { Visibility = V; }
-  
+
+  DLLStorageClassTypes getDLLStorageClass() const {
+    return DLLStorageClassTypes(DllStorageClass);
+  }
+  bool hasDLLImportStorageClass() const {
+    return DllStorageClass == DLLImportStorageClass;
+  }
+  bool hasDLLExportStorageClass() const {
+    return DllStorageClass == DLLExportStorageClass;
+  }
+  void setDLLStorageClass(DLLStorageClassTypes C) { DllStorageClass = C; }
+
   bool hasSection() const { return !Section.empty(); }
   const std::string &getSection() const { return Section; }
   void setSection(StringRef S) { Section = S; }
@@ -146,12 +164,6 @@ public:
     return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage) ||
       isLinkerPrivateLinkage(Linkage) || isLinkerPrivateWeakLinkage(Linkage);
   }
-  static bool isDLLImportLinkage(LinkageTypes Linkage) {
-    return Linkage == DLLImportLinkage;
-  }
-  static bool isDLLExportLinkage(LinkageTypes Linkage) {
-    return Linkage == DLLExportLinkage;
-  }
   static bool isExternalWeakLinkage(LinkageTypes Linkage) {
     return Linkage == ExternalWeakLinkage;
   }
@@ -209,8 +221,6 @@ public:
     return isLinkerPrivateWeakLinkage(Linkage);
   }
   bool hasLocalLinkage() const { return isLocalLinkage(Linkage); }
-  bool hasDLLImportLinkage() const { return isDLLImportLinkage(Linkage); }
-  bool hasDLLExportLinkage() const { return isDLLExportLinkage(Linkage); }
   bool hasExternalWeakLinkage() const { return isExternalWeakLinkage(Linkage); }
   bool hasCommonLinkage() const { return isCommonLinkage(Linkage); }