From 8420bb157cd82b7afb91c58e4b644f5cca0b10b9 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@google.com>
Date: Tue, 18 Mar 2025 00:43:53 -0700
Subject: [PATCH 1/3] [ADT] Add DenseSet(llvm::from_t, Range)

This patch adds a constructor of the form:

  DenseSet Set(llvm::from_range, Range)

while forward-porting std::from_range from c++23.
---
 llvm/include/llvm/ADT/DenseSet.h         | 5 +++++
 llvm/include/llvm/ADT/STLForwardCompat.h | 6 ++++++
 llvm/unittests/ADT/DenseSetTest.cpp      | 6 ++++++
 3 files changed, 17 insertions(+)

diff --git a/llvm/include/llvm/ADT/DenseSet.h b/llvm/include/llvm/ADT/DenseSet.h
index ac766e778df0d..5642f1400bc39 100644
--- a/llvm/include/llvm/ADT/DenseSet.h
+++ b/llvm/include/llvm/ADT/DenseSet.h
@@ -17,6 +17,7 @@
 #include "llvm/ADT/ADL.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/type_traits.h"
 #include <cstddef>
@@ -78,6 +79,10 @@ class DenseSetImpl {
     insert(Elems.begin(), Elems.end());
   }
 
+  template <typename Range>
+  DenseSetImpl(llvm::from_range_t, Range &&R)
+      : DenseSetImpl(adl_begin(R), adl_end(R)) {}
+
   bool empty() const { return TheMap.empty(); }
   size_type size() const { return TheMap.size(); }
   size_t getMemorySize() const { return TheMap.getMemorySize(); }
diff --git a/llvm/include/llvm/ADT/STLForwardCompat.h b/llvm/include/llvm/ADT/STLForwardCompat.h
index 6afe3610b257f..10c274ea8e23e 100644
--- a/llvm/include/llvm/ADT/STLForwardCompat.h
+++ b/llvm/include/llvm/ADT/STLForwardCompat.h
@@ -67,6 +67,12 @@ template <typename Enum>
   return static_cast<std::underlying_type_t<Enum>>(E);
 }
 
+// A tag for constructors accepting ranges.
+struct from_range_t {
+  explicit from_range_t() = default;
+};
+inline constexpr from_range_t from_range{};
+
 } // namespace llvm
 
 #endif // LLVM_ADT_STLFORWARDCOMPAT_H
diff --git a/llvm/unittests/ADT/DenseSetTest.cpp b/llvm/unittests/ADT/DenseSetTest.cpp
index 8fc2bab44b124..3f668b831a450 100644
--- a/llvm/unittests/ADT/DenseSetTest.cpp
+++ b/llvm/unittests/ADT/DenseSetTest.cpp
@@ -33,6 +33,12 @@ TEST(DenseSetTest, DoubleEntrySetTest) {
   EXPECT_EQ(0u, set.count(2));
 }
 
+TEST(DenseSetTest, CtorRange) {
+  constexpr unsigned Args[] = {3, 1, 2};
+  llvm::DenseSet<unsigned> set(llvm::from_range, Args);
+  EXPECT_THAT(set, ::testing::UnorderedElementsAre(1, 2, 3));
+}
+
 TEST(DenseSetTest, InsertRange) {
   llvm::DenseSet<unsigned> set;
   constexpr unsigned Args[] = {3, 1, 2};

From 28e915b67697df503303fce94689df6016233832 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@google.com>
Date: Sat, 22 Mar 2025 11:16:38 -0700
Subject: [PATCH 2/3] Address a comment.

---
 llvm/unittests/ADT/DenseSetTest.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/llvm/unittests/ADT/DenseSetTest.cpp b/llvm/unittests/ADT/DenseSetTest.cpp
index 3f668b831a450..2b62324c469a0 100644
--- a/llvm/unittests/ADT/DenseSetTest.cpp
+++ b/llvm/unittests/ADT/DenseSetTest.cpp
@@ -39,6 +39,12 @@ TEST(DenseSetTest, CtorRange) {
   EXPECT_THAT(set, ::testing::UnorderedElementsAre(1, 2, 3));
 }
 
+TEST(SmallDenseSetTest, CtorRange) {
+  constexpr unsigned Args[] = {9, 7, 8};
+  llvm::SmallDenseSet<unsigned> set(llvm::from_range, Args);
+  EXPECT_THAT(set, ::testing::UnorderedElementsAre(7, 8, 9));
+}
+
 TEST(DenseSetTest, InsertRange) {
   llvm::DenseSet<unsigned> set;
   constexpr unsigned Args[] = {3, 1, 2};

From 26e020aa0663f5cde22ab268a3e469531acf5f30 Mon Sep 17 00:00:00 2001
From: Kazu Hirata <kazu@google.com>
Date: Sat, 22 Mar 2025 16:28:39 -0700
Subject: [PATCH 3/3] Add a test with implicit conversion.

---
 llvm/unittests/ADT/DenseSetTest.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/llvm/unittests/ADT/DenseSetTest.cpp b/llvm/unittests/ADT/DenseSetTest.cpp
index 2b62324c469a0..5a8ee592ddfc7 100644
--- a/llvm/unittests/ADT/DenseSetTest.cpp
+++ b/llvm/unittests/ADT/DenseSetTest.cpp
@@ -39,6 +39,12 @@ TEST(DenseSetTest, CtorRange) {
   EXPECT_THAT(set, ::testing::UnorderedElementsAre(1, 2, 3));
 }
 
+TEST(DenseSetTest, CtorRangeImplicitConversion) {
+  constexpr char Args[] = {3, 1, 2};
+  llvm::DenseSet<unsigned> set(llvm::from_range, Args);
+  EXPECT_THAT(set, ::testing::UnorderedElementsAre(1, 2, 3));
+}
+
 TEST(SmallDenseSetTest, CtorRange) {
   constexpr unsigned Args[] = {9, 7, 8};
   llvm::SmallDenseSet<unsigned> set(llvm::from_range, Args);