[llvm] [ADT] Rename identity_cxx20 to identity (PR #164927)

[Kazu Hirata via llvm-commits]

https://github.com/kazutakahirata created https://github.com/llvm/llvm-project/pull/164927

Now that the old llvm::identity has moved into IndexedMap.h under a
different name, this patch renames identity_cxx20 to identity.  Note
that llvm::identity closely models std::identity from C++20.


>From c4d29b97186e1b0963e85b5f362c77881bb7a254 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu at google.com>
Date: Wed, 22 Oct 2025 13:17:28 -0700
Subject: [PATCH] [ADT] Rename identity_cxx20 to identity

Now that the old llvm::identity has moved into IndexedMap.h under a
different name, this patch renames identity_cxx20 to identity.  Note
that llvm::identity closely models std::identity from C++20.
---
 llvm/include/llvm/ADT/STLForwardCompat.h                       | 2 +-
 llvm/include/llvm/ADT/SparseMultiSet.h                         | 2 +-
 llvm/include/llvm/ADT/SparseSet.h                              | 2 +-
 llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h                  | 2 +-
 llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h | 2 +-
 llvm/lib/CodeGen/RegAllocFast.cpp                              | 2 +-
 llvm/unittests/ADT/STLForwardCompatTest.cpp                    | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/llvm/include/llvm/ADT/STLForwardCompat.h b/llvm/include/llvm/ADT/STLForwardCompat.h
index 9c81981534506..e02694f043fbb 100644
--- a/llvm/include/llvm/ADT/STLForwardCompat.h
+++ b/llvm/include/llvm/ADT/STLForwardCompat.h
@@ -125,7 +125,7 @@ struct detector<std::void_t<Op<Args...>>, Op, Args...> {
 template <template <class...> class Op, class... Args>
 using is_detected = typename detail::detector<void, Op, Args...>::value_t;
 
-struct identity_cxx20 // NOLINT(readability-identifier-naming)
+struct identity // NOLINT(readability-identifier-naming)
 {
   using is_transparent = void;
 
diff --git a/llvm/include/llvm/ADT/SparseMultiSet.h b/llvm/include/llvm/ADT/SparseMultiSet.h
index 5e4e1703373a9..59de4cf6a553b 100644
--- a/llvm/include/llvm/ADT/SparseMultiSet.h
+++ b/llvm/include/llvm/ADT/SparseMultiSet.h
@@ -82,7 +82,7 @@ namespace llvm {
 /// @tparam SparseT     An unsigned integer type. See above.
 ///
 template <typename ValueT, typename KeyT = unsigned,
-          typename KeyFunctorT = identity_cxx20, typename SparseT = uint8_t>
+          typename KeyFunctorT = identity, typename SparseT = uint8_t>
 class SparseMultiSet {
   static_assert(std::is_unsigned_v<SparseT>,
                 "SparseT must be an unsigned integer type");
diff --git a/llvm/include/llvm/ADT/SparseSet.h b/llvm/include/llvm/ADT/SparseSet.h
index 4697de097e7eb..99c140f40d1c6 100644
--- a/llvm/include/llvm/ADT/SparseSet.h
+++ b/llvm/include/llvm/ADT/SparseSet.h
@@ -117,7 +117,7 @@ struct SparseSetValFunctor<KeyT, KeyT, KeyFunctorT> {
 /// @tparam SparseT     An unsigned integer type. See above.
 ///
 template <typename ValueT, typename KeyT = unsigned,
-          typename KeyFunctorT = identity_cxx20, typename SparseT = uint8_t>
+          typename KeyFunctorT = identity, typename SparseT = uint8_t>
 class SparseSet {
   static_assert(std::is_unsigned_v<SparseT>,
                 "SparseT must be an unsigned integer type");
diff --git a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
index 26d708060ed6d..ab0d7e334df44 100644
--- a/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
+++ b/llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h
@@ -89,7 +89,7 @@ namespace llvm {
   /// allocated once for the pass. It can be cleared in constant time and reused
   /// without any frees.
   using RegUnit2SUnitsMap =
-      SparseMultiSet<PhysRegSUOper, unsigned, identity_cxx20, uint16_t>;
+      SparseMultiSet<PhysRegSUOper, unsigned, identity, uint16_t>;
 
   /// Track local uses of virtual registers. These uses are gathered by the DAG
   /// builder and may be consulted by the scheduler to avoid iterating an entire
diff --git a/llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h b/llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h
index 4a32113b460e1..6adaa8ae43895 100644
--- a/llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h
+++ b/llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h
@@ -34,7 +34,7 @@ using ExecutorAddrDiff = uint64_t;
 class ExecutorAddr {
 public:
   /// A wrap/unwrap function that leaves pointers unmodified.
-  using rawPtr = llvm::identity_cxx20;
+  using rawPtr = llvm::identity;
 
 #if __has_feature(ptrauth_calls)
   template <typename T> class PtrauthSignDefault {
diff --git a/llvm/lib/CodeGen/RegAllocFast.cpp b/llvm/lib/CodeGen/RegAllocFast.cpp
index 72b364c5668e2..697b779e10106 100644
--- a/llvm/lib/CodeGen/RegAllocFast.cpp
+++ b/llvm/lib/CodeGen/RegAllocFast.cpp
@@ -211,7 +211,7 @@ class RegAllocFastImpl {
     unsigned getSparseSetIndex() const { return VirtReg.virtRegIndex(); }
   };
 
-  using LiveRegMap = SparseSet<LiveReg, unsigned, identity_cxx20, uint16_t>;
+  using LiveRegMap = SparseSet<LiveReg, unsigned, identity, uint16_t>;
   /// This map contains entries for each virtual register that is currently
   /// available in a physical register.
   LiveRegMap LiveVirtRegs;
diff --git a/llvm/unittests/ADT/STLForwardCompatTest.cpp b/llvm/unittests/ADT/STLForwardCompatTest.cpp
index 2a97e8d6a552f..c6ae6e36cfbff 100644
--- a/llvm/unittests/ADT/STLForwardCompatTest.cpp
+++ b/llvm/unittests/ADT/STLForwardCompatTest.cpp
@@ -185,7 +185,7 @@ TEST(TransformTest, ToUnderlying) {
 }
 
 TEST(STLForwardCompatTest, IdentityCxx20) {
-  llvm::identity_cxx20 identity;
+  llvm::identity identity;
 
   // Test with an lvalue.
   int X = 42;