[ADT] Add DenseSet::insert_range

[kazutakahirata]

This pach adds DenseSet::insert_range, named after
std::map::insert_range from C++23. The intent is to allow a heavy
operation as the argument like:

Set.insert_range(Map[Key]);

Without insert_range, we would have to do:

Set.insert(Map[Key].begin(), Map[Key].end());

or:

auto &M = Map[Key];
Set.insert(M.begin(), M.end());

Neither is elegant.

[llvmbot]

@llvm/pr-subscribers-llvm-adt

Author: Kazu Hirata (kazutakahirata)

Changes

This pach adds DenseSet::insert_range, named after
std::map::insert_range from C++23. The intent is to allow a heavy
operation as the argument like:

Set.insert_range(Map[Key]);

Without insert_range, we would have to do:

Set.insert(Map[Key].begin(), Map[Key].end());

or:

auto &M = Map[Key];
Set.insert(M.begin(), M.end());

Neither is elegant.

---

Full diff: https://github.com/llvm/llvm-project/pull/131567.diff

2 Files Affected:

• (modified) llvm/include/llvm/ADT/DenseSet.h (+5)
• (modified) llvm/unittests/ADT/DenseSetTest.cpp (+11)

diff --git a/llvm/include/llvm/ADT/DenseSet.h b/llvm/include/llvm/ADT/DenseSet.h
index a307bd8c9198b..ac766e778df0d 100644
--- a/llvm/include/llvm/ADT/DenseSet.h
+++ b/llvm/include/llvm/ADT/DenseSet.h
@@ -14,6 +14,7 @@
 #ifndef LLVM_ADT_DENSESET_H
 #define LLVM_ADT_DENSESET_H
 
+#include "llvm/ADT/ADL.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include "llvm/Support/MathExtras.h"
@@ -237,6 +238,10 @@ class DenseSetImpl {
     for (; I != E; ++I)
       insert(*I);
   }
+
+  template <typename Range> void insert_range(Range &&R) {
+    insert(adl_begin(R), adl_end(R));
+  }
 };
 
 /// Equality comparison for DenseSet.
diff --git a/llvm/unittests/ADT/DenseSetTest.cpp b/llvm/unittests/ADT/DenseSetTest.cpp
index f14542eafc251..14cef2ab678f9 100644
--- a/llvm/unittests/ADT/DenseSetTest.cpp
+++ b/llvm/unittests/ADT/DenseSetTest.cpp
@@ -32,6 +32,17 @@ TEST(DenseSetTest, DoubleEntrySetTest) {
   EXPECT_EQ(0u, set.count(2));
 }
 
+TEST(DenseSetTest, InsertRange) {
+  llvm::DenseSet<unsigned> set1;
+  llvm::DenseSet<unsigned> set2;
+  set1.insert(1);
+  set1.insert(2);
+  set1.insert(3);
+  constexpr unsigned Args[] = {3, 1, 2};
+  set2.insert_range(Args);
+  EXPECT_EQ(set1, set2);
+}
+
 struct TestDenseSetInfo {
   static inline unsigned getEmptyKey() { return ~0; }
   static inline unsigned getTombstoneKey() { return ~0U - 1; }

[kuhar]

Can't we use 'append_range'?

[kazutakahirata]

Can't we use 'append_range'?

We cannot quite use append_range with std::map or DenseSet because it is implemented like so:

template <typename Container, typename Range>
void append_range(Container &C, Range &&R) {
  C.insert(C.end(), adl_begin(R), adl_end(R));
}

Note that neither std::map::insert nor DenseSet accepts C.end().

[kuhar]

If the right .insert is not available, then this makes sense to me.