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, 15 insertions, 4 deletions

diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index be19b781d4a..1d763d66ddc 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -481,8 +481,6 @@ static unsigned getEncodedLinkage(const GlobalValue *GV) {
   case GlobalValue::AppendingLinkage:                return 2;
   case GlobalValue::InternalLinkage:                 return 3;
   case GlobalValue::LinkOnceAnyLinkage:              return 4;
-  case GlobalValue::DLLImportLinkage:                return 5;
-  case GlobalValue::DLLExportLinkage:                return 6;
   case GlobalValue::ExternalWeakLinkage:             return 7;
   case GlobalValue::CommonLinkage:                   return 8;
   case GlobalValue::PrivateLinkage:                  return 9;
@@ -504,6 +502,15 @@ static unsigned getEncodedVisibility(const GlobalValue *GV) {
   llvm_unreachable("Invalid visibility");
 }
 
+static unsigned getEncodedDLLStorageClass(const GlobalValue *GV) {
+  switch (GV->getDLLStorageClass()) {
+  case GlobalValue::DefaultStorageClass:   return 0;
+  case GlobalValue::DLLImportStorageClass: return 1;
+  case GlobalValue::DLLExportStorageClass: return 2;
+  }
+  llvm_unreachable("Invalid DLL storage class");
+}
+
 static unsigned getEncodedThreadLocalMode(const GlobalVariable *GV) {
   switch (GV->getThreadLocalMode()) {
     case GlobalVariable::NotThreadLocal:         return 0;
@@ -607,7 +614,7 @@ static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
 
     // GLOBALVAR: [type, isconst, initid,
     //             linkage, alignment, section, visibility, threadlocal,
-    //             unnamed_addr, externally_initialized]
+    //             unnamed_addr, externally_initialized, dllstorageclass]
     Vals.push_back(VE.getTypeID(GV->getType()));
     Vals.push_back(GV->isConstant());
     Vals.push_back(GV->isDeclaration() ? 0 :
@@ -617,11 +624,13 @@ static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
     Vals.push_back(GV->hasSection() ? SectionMap[GV->getSection()] : 0);
     if (GV->isThreadLocal() ||
         GV->getVisibility() != GlobalValue::DefaultVisibility ||
-        GV->hasUnnamedAddr() || GV->isExternallyInitialized()) {
+        GV->hasUnnamedAddr() || GV->isExternallyInitialized() ||
+        GV->getDLLStorageClass() != GlobalValue::DefaultStorageClass) {
       Vals.push_back(getEncodedVisibility(GV));
       Vals.push_back(getEncodedThreadLocalMode(GV));
       Vals.push_back(GV->hasUnnamedAddr());
       Vals.push_back(GV->isExternallyInitialized());
+      Vals.push_back(getEncodedDLLStorageClass(GV));
     } else {
       AbbrevToUse = SimpleGVarAbbrev;
     }
@@ -646,6 +655,7 @@ static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
     Vals.push_back(F->hasUnnamedAddr());
     Vals.push_back(F->hasPrefixData() ? (VE.getValueID(F->getPrefixData()) + 1)
                                       : 0);
+    Vals.push_back(getEncodedDLLStorageClass(F));
 
     unsigned AbbrevToUse = 0;
     Stream.EmitRecord(bitc::MODULE_CODE_FUNCTION, Vals, AbbrevToUse);
@@ -660,6 +670,7 @@ static void WriteModuleInfo(const Module *M, const ValueEnumerator &VE,
     Vals.push_back(VE.getValueID(AI->getAliasee()));
     Vals.push_back(getEncodedLinkage(AI));
     Vals.push_back(getEncodedVisibility(AI));
+    Vals.push_back(getEncodedDLLStorageClass(AI));
     unsigned AbbrevToUse = 0;
     Stream.EmitRecord(bitc::MODULE_CODE_ALIAS, Vals, AbbrevToUse);
     Vals.clear();