[clang] [llvm] Disentangle DISubprogram ODR type method uniquing from metadata uniquing (PR #217042)

[Orlando Cazalet-Hyams via cfe-commits]

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@@ -0,0 +1,97 @@
+//===- llvm/IR/DebugInfoODRUniquer.h - Debug info metadata ------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines a class used to merge debug info for ODR types.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Metadata.h"
+
+namespace llvm {
+class MDString;
+class Metadata;
+class DICompositeType;
+
+/// Dense set/map find_as key for use alongside DISubprogramODRInfo to
+/// merge function declarations of ODR types.
+struct DISubprogramODRKey {
+  StringRef ScopeIdentifier;
+  StringRef LinkageName;
+
+  DISubprogramODRKey(StringRef ScopeIdentifier, StringRef LinkageName)
+      : ScopeIdentifier(ScopeIdentifier), LinkageName(LinkageName) {}
+
+  DISubprogramODRKey(const DISubprogram *SP) {
+    auto *CT = dyn_cast_or_null<DICompositeType>(SP->getRawScope());
+    ScopeIdentifier = CT ? CT->getIdentifier() : StringRef();
+    LinkageName = SP->getLinkageName();
+  }
+
+  static bool isEqual(const DISubprogramODRKey &LHS, const DISubprogram *RHS) {
+    if (LHS.LinkageName.empty() || LHS.ScopeIdentifier.empty())
+      return false;
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OCHyams wrote:

Hrm. Good point, I think it is fine, but no reason to keep it this way. Fixed

https://github.com/llvm/llvm-project/pull/217042