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@199218 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 38 insertions, 16 deletions

diff --git a/lib/Target/CppBackend/CPPBackend.cpp b/lib/Target/CppBackend/CPPBackend.cpp
index 6e2dd0a8e7..b13709914b 100644
--- a/lib/Target/CppBackend/CPPBackend.cpp
+++ b/lib/Target/CppBackend/CPPBackend.cpp
@@ -131,6 +131,7 @@ namespace {
   private:
     void printLinkageType(GlobalValue::LinkageTypes LT);
     void printVisibilityType(GlobalValue::VisibilityTypes VisTypes);
+    void printDLLStorageClassType(GlobalValue::DLLStorageClassTypes DSCType);
     void printThreadLocalMode(GlobalVariable::ThreadLocalMode TLM);
     void printCallingConv(CallingConv::ID cc);
     void printEscapedString(const std::string& str);
@@ -300,10 +301,6 @@ void CppWriter::printLinkageType(GlobalValue::LinkageTypes LT) {
     Out << "GlobalValue::AppendingLinkage"; break;
   case GlobalValue::ExternalLinkage:
     Out << "GlobalValue::ExternalLinkage"; break;
-  case GlobalValue::DLLImportLinkage:
-    Out << "GlobalValue::DLLImportLinkage"; break;
-  case GlobalValue::DLLExportLinkage:
-    Out << "GlobalValue::DLLExportLinkage"; break;
   case GlobalValue::ExternalWeakLinkage:
     Out << "GlobalValue::ExternalWeakLinkage"; break;
   case GlobalValue::CommonLinkage:
@@ -325,6 +322,21 @@ void CppWriter::printVisibilityType(GlobalValue::VisibilityTypes VisType) {
   }
 }
 
+void CppWriter::printDLLStorageClassType(
+                                    GlobalValue::DLLStorageClassTypes DSCType) {
+  switch (DSCType) {
+  case GlobalValue::DefaultStorageClass:
+    Out << "GlobalValue::DefaultStorageClass";
+    break;
+  case GlobalValue::DLLImportStorageClass:
+    Out << "GlobalValue::DLLImportStorageClass";
+    break;
+  case GlobalValue::DLLExportStorageClass:
+    Out << "GlobalValue::DLLExportStorageClass";
+    break;
+  }
+}
+
 void CppWriter::printThreadLocalMode(GlobalVariable::ThreadLocalMode TLM) {
   switch (TLM) {
     case GlobalVariable::NotThreadLocal:
@@ -1028,6 +1040,13 @@ void CppWriter::printVariableHead(const GlobalVariable *GV) {
     Out << ");";
     nl(Out);
   }
+  if (GV->getDLLStorageClass() != GlobalValue::DefaultStorageClass) {
+    printCppName(GV);
+    Out << "->setDLLStorageClass(";
+    printDLLStorageClassType(GV->getDLLStorageClass());
+    Out << ");";
+    nl(Out);
+  }
   if (GV->isThreadLocal()) {
     printCppName(GV);
     Out << "->setThreadLocalMode(";
@@ -1746,6 +1765,13 @@ void CppWriter::printFunctionHead(const Function* F) {
     Out << ");";
     nl(Out);
   }
+  if (F->getDLLStorageClass() != GlobalValue::DefaultStorageClass) {
+    printCppName(F);
+    Out << "->setDLLStorageClass(";
+    printDLLStorageClassType(F->getDLLStorageClass());
+    Out << ");";
+    nl(Out);
+  }
   if (F->hasGC()) {
     printCppName(F);
     Out << "->setGC(\"" << F->getGC() << "\");";
diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index a2c3f770d3..ad7d3e0fdc 100644
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -649,20 +649,20 @@ void X86AsmPrinter::EmitEndOfAsmFile(Module &M) {
     // Necessary for dllexport support
     std::vector<const MCSymbol*> DLLExportedFns, DLLExportedGlobals;
 
-    const TargetLoweringObjectFileCOFF &TLOFCOFF =
-      static_cast<const TargetLoweringObjectFileCOFF&>(getObjFileLowering());
-
     for (Module::const_iterator I = M.begin(), E = M.end(); I != E; ++I)
-      if (I->hasDLLExportLinkage())
+      if (I->hasDLLExportStorageClass())
         DLLExportedFns.push_back(getSymbol(I));
 
     for (Module::const_global_iterator I = M.global_begin(),
            E = M.global_end(); I != E; ++I)
-      if (I->hasDLLExportLinkage())
+      if (I->hasDLLExportStorageClass())
         DLLExportedGlobals.push_back(getSymbol(I));
 
     // Output linker support code for dllexported globals on windows.
     if (!DLLExportedGlobals.empty() || !DLLExportedFns.empty()) {
+      const TargetLoweringObjectFileCOFF &TLOFCOFF =
+        static_cast<const TargetLoweringObjectFileCOFF&>(getObjFileLowering());
+
       OutStreamer.SwitchSection(TLOFCOFF.getDrectveSection());
       SmallString<128> name;
       for (unsigned i = 0, e = DLLExportedGlobals.size(); i != e; ++i) {
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index fd10a4a09e..7b2d1d7776 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -697,7 +697,7 @@ bool X86FastISel::X86SelectCallAddress(const Value *V, X86AddressMode &AM) {
       return false;
 
     // Can't handle DLLImport.
-    if (GV->hasDLLImportLinkage())
+    if (GV->hasDLLImportStorageClass())
       return false;
 
     // Can't handle TLS.
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 9fa7f7461f..677cdbdee8 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2796,7 +2796,7 @@ X86TargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
     // We should use extra load for direct calls to dllimported functions in
     // non-JIT mode.
     const GlobalValue *GV = G->getGlobal();
-    if (!GV->hasDLLImportLinkage()) {
+    if (!GV->hasDLLImportStorageClass()) {
       unsigned char OpFlags = 0;
       bool ExtraLoad = false;
       unsigned WrapperKind = ISD::DELETED_NODE;
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index b183ed0314..6f724b42d9 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -55,7 +55,7 @@ unsigned char X86Subtarget::
 ClassifyGlobalReference(const GlobalValue *GV, const TargetMachine &TM) const {
   // DLLImport only exists on windows, it is implemented as a load from a
   // DLLIMPORT stub.
-  if (GV->hasDLLImportLinkage())
+  if (GV->hasDLLImportStorageClass())
     return X86II::MO_DLLIMPORT;
 
   // Determine whether this is a reference to a definition or a declaration.
diff --git a/lib/Target/XCore/XCoreAsmPrinter.cpp b/lib/Target/XCore/XCoreAsmPrinter.cpp
index ee84aa4a88..778bf9ca39 100644
--- a/lib/Target/XCore/XCoreAsmPrinter.cpp
+++ b/lib/Target/XCore/XCoreAsmPrinter.cpp
@@ -135,10 +135,6 @@ void XCoreAsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
   case GlobalValue::InternalLinkage:
   case GlobalValue::PrivateLinkage:
     break;
-  case GlobalValue::DLLImportLinkage:
-    llvm_unreachable("DLLImport linkage is not supported by this target!");
-  case GlobalValue::DLLExportLinkage:
-    llvm_unreachable("DLLExport linkage is not supported by this target!");
   default:
     llvm_unreachable("Unknown linkage type!");
   }