[llvm] [CAS] OnDiskGraphDB - fix MSVC "not all control paths return a value" warnings. NFC. (PR #164369)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/164369

None

>From 342fcf41e060ea43637568b1741c09febe7598b5 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Tue, 21 Oct 2025 08:26:46 +0100
Subject: [PATCH] [CAS] OnDiskGraphDB - fix MSVC "not all control paths return
 a value" warnings. NFC.

---
 llvm/include/llvm/CAS/OnDiskGraphDB.h | 1 +
 llvm/lib/CAS/OnDiskGraphDB.cpp        | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/llvm/include/llvm/CAS/OnDiskGraphDB.h b/llvm/include/llvm/CAS/OnDiskGraphDB.h
index 83017a6a54fee..5f0ee0e131c0f 100644
--- a/llvm/include/llvm/CAS/OnDiskGraphDB.h
+++ b/llvm/include/llvm/CAS/OnDiskGraphDB.h
@@ -380,6 +380,7 @@ class OnDiskGraphDB {
     case ObjectPresence::OnlyInUpstreamDB:
       return true;
     }
+    llvm_unreachable("Unknown ObjectPresence enum");
   }
 
   /// When \p load is called for a node that doesn't exist, this function tries
diff --git a/llvm/lib/CAS/OnDiskGraphDB.cpp b/llvm/lib/CAS/OnDiskGraphDB.cpp
index 72bb98c4bf65d..64cbe9dc8e159 100644
--- a/llvm/lib/CAS/OnDiskGraphDB.cpp
+++ b/llvm/lib/CAS/OnDiskGraphDB.cpp
@@ -836,6 +836,7 @@ uint64_t DataRecordHandle::getDataSize() const {
   case DataSizeFlags::Uses8B:
     return support::endian::read64le(DataSizePtr);
   }
+  llvm_unreachable("Unknown DataSizeFlags enum");
 }
 
 void DataRecordHandle::skipDataSize(LayoutFlags LF, int64_t &RelOffset) const {
@@ -863,6 +864,7 @@ uint32_t DataRecordHandle::getNumRefs() const {
   case NumRefsFlags::Uses8B:
     return support::endian::read64le(NumRefsPtr);
   }
+  llvm_unreachable("Unknown NumRefsFlags enum");
 }
 
 void DataRecordHandle::skipNumRefs(LayoutFlags LF, int64_t &RelOffset) const {
@@ -1270,6 +1272,7 @@ Expected<bool> OnDiskGraphDB::isMaterialized(ObjectID Ref) {
       return FaultInResult.takeError();
     return true;
   }
+  llvm_unreachable("Unknown ObjectPresence enum");
 }
 
 Expected<OnDiskGraphDB::ObjectPresence>