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.

llvm-svn: 199218

1 files changed, 4 insertions, 6 deletions

diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
index ff4976bcbf9..6e920a2daa4 100644
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -1164,10 +1164,6 @@ LLVMLinkage LLVMGetLinkage(LLVMValueRef Global) {
     return LLVMLinkerPrivateLinkage;
   case GlobalValue::LinkerPrivateWeakLinkage:
     return LLVMLinkerPrivateWeakLinkage;
-  case GlobalValue::DLLImportLinkage:
-    return LLVMDLLImportLinkage;
-  case GlobalValue::DLLExportLinkage:
-    return LLVMDLLExportLinkage;
   case GlobalValue::ExternalWeakLinkage:
     return LLVMExternalWeakLinkage;
   case GlobalValue::CommonLinkage:
@@ -1219,10 +1215,12 @@ void LLVMSetLinkage(LLVMValueRef Global, LLVMLinkage Linkage) {
     GV->setLinkage(GlobalValue::LinkerPrivateWeakLinkage);
     break;
   case LLVMDLLImportLinkage:
-    GV->setLinkage(GlobalValue::DLLImportLinkage);
+    DEBUG(errs()
+          << "LLVMSetLinkage(): LLVMDLLImportLinkage is no longer supported.");
     break;
   case LLVMDLLExportLinkage:
-    GV->setLinkage(GlobalValue::DLLExportLinkage);
+    DEBUG(errs()
+          << "LLVMSetLinkage(): LLVMDLLExportLinkage is no longer supported.");
     break;
   case LLVMExternalWeakLinkage:
     GV->setLinkage(GlobalValue::ExternalWeakLinkage);