[llvm] Store GUIDs in metadata (PR #133682)

[Mircea Trofin via llvm-commits]

================
@@ -78,6 +78,46 @@ GlobalValue::getGUIDAssumingExternalLinkage(StringRef GlobalIdentifier) {
   return MD5Hash(GlobalIdentifier);
 }
 
+void GlobalValue::assignGUID() {
+  if (isDeclaration()) {
+    // Declarations don't get an assigned GUID. Their definition is in another
+    // module, and it may have been promoted from local to external linkage
+    // during LTO. Because of this, we can only determine their GUID once the
+    // definition is available.
+    return;
+  }
+  if (getMetadata(LLVMContext::MD_unique_id) != nullptr)
+    return;
+
+  const GUID G =
+      GlobalValue::getGUIDAssumingExternalLinkage(getGlobalIdentifier());
+  setMetadata(
+      LLVMContext::MD_unique_id,
+      MDNode::get(getContext(), {ConstantAsMetadata::get(ConstantInt::get(
+                                    Type::getInt64Ty(getContext()), G))}));
+}
+
+GlobalValue::GUID GlobalValue::getGUID() const {
+  if (isa<GlobalAlias>(this)) {
+    return GlobalValue::getGUIDAssumingExternalLinkage(getGlobalIdentifier());
+  }
+
+  if (isDeclaration()) {
----------------
mtrofin wrote:

They can have a GUID tho, because the linkage won't be private or internal. So the GUID won't depend on the module defining them. 

https://github.com/llvm/llvm-project/pull/133682