[llvm] DenseMapInfo: support std::optional<T> (PR #147851)

[Elijah Kin via llvm-commits]

https://github.com/elijahkin updated https://github.com/llvm/llvm-project/pull/147851

>From c93c4c476b3fb07b56783b327ea2f63034b47b56 Mon Sep 17 00:00:00 2001
From: Elijah Kin <elijah.m.kin at gmail.com>
Date: Wed, 9 Jul 2025 16:05:28 -0700
Subject: [PATCH 1/3] [ADT] Implement DenseMapInfo of std::optional<T>

---
 llvm/include/llvm/ADT/DenseMapInfo.h | 29 ++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/llvm/include/llvm/ADT/DenseMapInfo.h b/llvm/include/llvm/ADT/DenseMapInfo.h
index 07c37e353a40b..65c607910d089 100644
--- a/llvm/include/llvm/ADT/DenseMapInfo.h
+++ b/llvm/include/llvm/ADT/DenseMapInfo.h
@@ -320,6 +320,35 @@ struct DenseMapInfo<Enum, std::enable_if_t<std::is_enum_v<Enum>>> {
 
   static bool isEqual(const Enum &LHS, const Enum &RHS) { return LHS == RHS; }
 };
+
+template <typename T>
+struct DenseMapInfo<std::optional<T>> {
+  using Optional = std::optional<T>;
+  using Info = DenseMapInfo<T>;
+
+  static inline Optional getEmptyKey() {
+    return std::make_optional(Info::getEmptyKey());
+  }
+
+  static inline Optional getTombstoneKey() {
+    return std::make_optional(Info::getTombstoneKey());
+  }
+
+  static unsigned getHashValue(const Optional &OptionalVal) {
+    return detail::combineHashValue(
+        OptionalVal.has_value(),
+        Info::getHashValue(OptionalVal.value_or(Info::getEmptyKey())));
+  }
+
+  static bool isEqual(const Optional &LHS, const Optional &RHS) {
+    if (LHS.has_value() && RHS.has_value()) {
+      return Info::isEqual(LHS.value(), RHS.value());
+    } else if (!LHS.has_value() && !RHS.has_value()) {
+      return true;
+    }
+    return false;
+  }
+};
 } // end namespace llvm
 
 #endif // LLVM_ADT_DENSEMAPINFO_H

>From f7a244c61bc7431a3fd4d7a3a5ecad215a2e4623 Mon Sep 17 00:00:00 2001
From: Elijah Kin <elijah.m.kin at gmail.com>
Date: Wed, 9 Jul 2025 16:23:33 -0700
Subject: [PATCH 2/3] Registering std::optional<uint32_t> for testing

---
 llvm/unittests/ADT/DenseMapTest.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/llvm/unittests/ADT/DenseMapTest.cpp b/llvm/unittests/ADT/DenseMapTest.cpp
index c95f96c4bb3c6..ca04dc055fd11 100644
--- a/llvm/unittests/ADT/DenseMapTest.cpp
+++ b/llvm/unittests/ADT/DenseMapTest.cpp
@@ -15,6 +15,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <map>
+#include <optional>
 #include <set>
 #include <utility>
 #include <variant>
@@ -117,11 +118,13 @@ typedef ::testing::Types<DenseMap<uint32_t, uint32_t>,
                          DenseMap<uint32_t *, uint32_t *>,
                          DenseMap<CtorTester, CtorTester, CtorTesterMapInfo>,
                          DenseMap<EnumClass, uint32_t>,
+                         DenseMap<std::optional<uint32_t>, uint32_t>,
                          SmallDenseMap<uint32_t, uint32_t>,
                          SmallDenseMap<uint32_t *, uint32_t *>,
                          SmallDenseMap<CtorTester, CtorTester, 4,
                                        CtorTesterMapInfo>,
-                         SmallDenseMap<EnumClass, uint32_t>
+                         SmallDenseMap<EnumClass, uint32_t>,
+                         SmallDenseMap<std::optional<uint32_t>, uint32_t>
                          > DenseMapTestTypes;
 // clang-format on
 

>From c8b3e811002abae1d05d4640d558789d88c22d33 Mon Sep 17 00:00:00 2001
From: Elijah Kin <elijah.m.kin at gmail.com>
Date: Wed, 9 Jul 2025 16:46:58 -0700
Subject: [PATCH 3/3] Avoiding else after return

---
 llvm/include/llvm/ADT/DenseMapInfo.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/llvm/include/llvm/ADT/DenseMapInfo.h b/llvm/include/llvm/ADT/DenseMapInfo.h
index 65c607910d089..2dd2ff4f6f022 100644
--- a/llvm/include/llvm/ADT/DenseMapInfo.h
+++ b/llvm/include/llvm/ADT/DenseMapInfo.h
@@ -341,12 +341,10 @@ struct DenseMapInfo<std::optional<T>> {
   }
 
   static bool isEqual(const Optional &LHS, const Optional &RHS) {
-    if (LHS.has_value() && RHS.has_value()) {
+    if (LHS && RHS) {
       return Info::isEqual(LHS.value(), RHS.value());
-    } else if (!LHS.has_value() && !RHS.has_value()) {
-      return true;
     }
-    return false;
+    return !LHS && !RHS;
   }
 };
 } // end namespace llvm