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: 199204

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index 91684c9c70e..eba05c5f28e 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -1367,8 +1367,6 @@ static void PrintLinkage(GlobalValue::LinkageTypes LT,
   case GlobalValue::WeakODRLinkage:       Out << "weak_odr ";       break;
   case GlobalValue::CommonLinkage:        Out << "common ";         break;
   case GlobalValue::AppendingLinkage:     Out << "appending ";      break;
-  case GlobalValue::DLLImportLinkage:     Out << "dllimport ";      break;
-  case GlobalValue::DLLExportLinkage:     Out << "dllexport ";      break;
   case GlobalValue::ExternalWeakLinkage:  Out << "extern_weak ";    break;
   case GlobalValue::AvailableExternallyLinkage:
     Out << "available_externally ";
@@ -1386,6 +1384,15 @@ static void PrintVisibility(GlobalValue::VisibilityTypes Vis,
   }
 }
 
+static void PrintDLLStorageClass(GlobalValue::DLLStorageClassTypes SCT,
+                                 formatted_raw_ostream &Out) {
+  switch (SCT) {
+  case GlobalValue::DefaultStorageClass: break;
+  case GlobalValue::DLLImportStorageClass: Out << "dllimport "; break;
+  case GlobalValue::DLLExportStorageClass: Out << "dllexport "; break;
+  }
+}
+
 static void PrintThreadLocalModel(GlobalVariable::ThreadLocalMode TLM,
                                   formatted_raw_ostream &Out) {
   switch (TLM) {
@@ -1418,6 +1425,7 @@ void AssemblyWriter::printGlobal(const GlobalVariable *GV) {
 
   PrintLinkage(GV->getLinkage(), Out);
   PrintVisibility(GV->getVisibility(), Out);
+  PrintDLLStorageClass(GV->getDLLStorageClass(), Out);
   PrintThreadLocalModel(GV->getThreadLocalMode(), Out);
 
   if (unsigned AddressSpace = GV->getType()->getAddressSpace())
@@ -1455,6 +1463,7 @@ void AssemblyWriter::printAlias(const GlobalAlias *GA) {
     Out << " = ";
   }
   PrintVisibility(GA->getVisibility(), Out);
+  PrintDLLStorageClass(GA->getDLLStorageClass(), Out);
 
   Out << "alias ";
 
@@ -1552,6 +1561,7 @@ void AssemblyWriter::printFunction(const Function *F) {
 
   PrintLinkage(F->getLinkage(), Out);
   PrintVisibility(F->getVisibility(), Out);
+  PrintDLLStorageClass(F->getDLLStorageClass(), Out);
 
   // Print the calling convention.
   if (F->getCallingConv() != CallingConv::C) {