Objective-C Class Properties: Autoupgrade "Class Properties" module flag.

When we have "Image Info Version" module flag but don't have "Class Properties"
module flag, set "Class Properties" module flag to 0, so we can correctly emit
errors when one module has the flag set and another module does not.

rdar://26469641

llvm-svn: 270791

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/lib/IR/AutoUpgrade.cpp b/llvm/lib/IR/AutoUpgrade.cpp
index aff89775a5a..d05bb47a68c 100644
--- a/llvm/lib/IR/AutoUpgrade.cpp
+++ b/llvm/lib/IR/AutoUpgrade.cpp
@@ -958,6 +958,37 @@ bool llvm::UpgradeDebugInfo(Module &M) {
   return RetCode;
 }
 
+bool llvm::UpgradeModuleFlags(Module &M) {
+  const NamedMDNode *ModFlags = M.getModuleFlagsMetadata();
+  if (!ModFlags)
+    return false;
+
+  bool HasObjCFlag = false, HasClassProperties = false;
+  for (unsigned I = 0, E = ModFlags->getNumOperands(); I != E; ++I) {
+    MDNode *Op = ModFlags->getOperand(I);
+    if (Op->getNumOperands() < 2)
+      continue;
+    MDString *ID = dyn_cast_or_null<MDString>(Op->getOperand(1));
+    if (!ID)
+      continue;
+    if (ID->getString() == "Objective-C Image Info Version")
+      HasObjCFlag = true;
+    if (ID->getString() == "Objective-C Class Properties")
+      HasClassProperties = true;
+  }
+  // "Objective-C Class Properties" is recently added for Objective-C. We
+  // upgrade ObjC bitcodes to contain a "Objective-C Class Properties" module
+  // flag of value 0, so we can correclty report error when trying to link
+  // an ObjC bitcode without this module flag with an ObjC bitcode with this
+  // module flag.
+  if (HasObjCFlag && !HasClassProperties) {
+    M.addModuleFlag(llvm::Module::Error, "Objective-C Class Properties",
+                    (uint32_t)0);
+    return true;
+  }
+  return false;
+}
+
 static bool isOldLoopArgument(Metadata *MD) {
   auto *T = dyn_cast_or_null<MDTuple>(MD);
   if (!T)