[llvm] [IR] Use persistent metadata IDs for pass snapshots (PR #216838)

[Alexis Engelke via llvm-commits]

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@@ -785,6 +786,14 @@ AbstractSlotTrackerStorage::~AbstractSlotTrackerStorage() = default;
 //===----------------------------------------------------------------------===//
 // SlotTracker Class: Enumerate slot numbers for unnamed values
 //===----------------------------------------------------------------------===//
+namespace {
+enum class MetadataPrintMode {
+  Compact,
+  PersistentReferences,
+  PersistentDefinitions,
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aengelke wrote:

Why three modes (and no documentation)?

https://github.com/llvm/llvm-project/pull/216838