[llvm] ADT: Add constructor from uint64_t array for Bitset (PR #162703)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/162703

>From 58d602f9180402f59484045bfa92647fa069e374 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Thu, 9 Oct 2025 11:41:29 +0900
Subject: [PATCH 1/3] ADT: Add constructor from uint64_t array for Bitset

Avoids exposing the implementation detail of uintptr_t to
the constructor.

This is a replacement of b738f630f73975bc591a82fdcb4858ae5da67477
which avoids needing tablegen to know the underlying storage type.
---
 llvm/include/llvm/ADT/Bitset.h    | 13 ++++++++-
 llvm/unittests/ADT/BitsetTest.cpp | 44 +++++++++++++++++++++++++++++++
 llvm/unittests/ADT/CMakeLists.txt |  1 +
 3 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 llvm/unittests/ADT/BitsetTest.cpp

diff --git a/llvm/include/llvm/ADT/Bitset.h b/llvm/include/llvm/ADT/Bitset.h
index b1e539e39aff7..b64648f9bccc4 100644
--- a/llvm/include/llvm/ADT/Bitset.h
+++ b/llvm/include/llvm/ADT/Bitset.h
@@ -45,7 +45,18 @@ class Bitset {
   StorageType Bits{};
 
 protected:
-  constexpr Bitset(const StorageType &B) : Bits{B} {}
+  constexpr Bitset(const std::array<uint64_t, (NumBits + 63) / 64> &B) {
+    if (sizeof(BitWord) == sizeof(uint64_t)) {
+      for (size_t I = 0; I != B.size(); ++I)
+        Bits[I] = B[I];
+    } else {
+      for (size_t I = 0; I != B.size(); ++I) {
+        uint64_t Elt = B[I];
+        Bits[2 * I] = static_cast<uint32_t>(Elt);
+        Bits[2 * I + 1] = static_cast<uint32_t>(Elt >> 32);
+      }
+    }
+  }
 
 public:
   constexpr Bitset() = default;
diff --git a/llvm/unittests/ADT/BitsetTest.cpp b/llvm/unittests/ADT/BitsetTest.cpp
new file mode 100644
index 0000000000000..8877397b30c53
--- /dev/null
+++ b/llvm/unittests/ADT/BitsetTest.cpp
@@ -0,0 +1,44 @@
+//===- llvm/unittest/Support/BitsetTest.cpp -------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/Bitset.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+template <unsigned NumBits>
+class TestBitsetUInt64Array : public Bitset<NumBits> {
+  static constexpr unsigned NumElts = (NumBits + 63) / 64;
+
+public:
+  TestBitsetUInt64Array(const std::array<uint64_t, NumElts> &B)
+      : Bitset<NumBits>(B) {}
+
+  bool verifyValue(const std::array<uint64_t, NumElts> &B) const {
+    for (unsigned I = 0; I != NumBits; ++I) {
+      bool ReferenceVal =
+          (B[(I / 64)] & (static_cast<uint64_t>(1) << (I % 64))) != 0;
+      if (ReferenceVal != this->test(I))
+        return false;
+    }
+
+    return true;
+  }
+};
+
+TEST(BitsetTest, Construction) {
+  std::array<uint64_t, 2> TestVals = {0x123456789abcdef3, 0x1337d3a0b22c24};
+  TestBitsetUInt64Array<96> Test(TestVals);
+  EXPECT_TRUE(Test.verifyValue(TestVals));
+
+  TestBitsetUInt64Array<65> Test1(TestVals);
+  EXPECT_TRUE(Test1.verifyValue(TestVals));
+}
+} // namespace
diff --git a/llvm/unittests/ADT/CMakeLists.txt b/llvm/unittests/ADT/CMakeLists.txt
index dafd73518aedb..848ccba696e76 100644
--- a/llvm/unittests/ADT/CMakeLists.txt
+++ b/llvm/unittests/ADT/CMakeLists.txt
@@ -12,6 +12,7 @@ add_llvm_unittest(ADTTests
   BitFieldsTest.cpp
   BitmaskEnumTest.cpp
   BitTest.cpp
+  BitsetTest.cpp
   BitVectorTest.cpp
   BreadthFirstIteratorTest.cpp
   BumpPtrListTest.cpp

>From 93b0df66a345f08fb2633874b8286ab98e86a83c Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 10 Oct 2025 11:16:27 +0900
Subject: [PATCH 2/3] Use if constexpr

---
 llvm/include/llvm/ADT/Bitset.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/include/llvm/ADT/Bitset.h b/llvm/include/llvm/ADT/Bitset.h
index b64648f9bccc4..851ae19d12def 100644
--- a/llvm/include/llvm/ADT/Bitset.h
+++ b/llvm/include/llvm/ADT/Bitset.h
@@ -46,7 +46,7 @@ class Bitset {
 
 protected:
   constexpr Bitset(const std::array<uint64_t, (NumBits + 63) / 64> &B) {
-    if (sizeof(BitWord) == sizeof(uint64_t)) {
+    if constexpr (sizeof(BitWord) == sizeof(uint64_t)) {
       for (size_t I = 0; I != B.size(); ++I)
         Bits[I] = B[I];
     } else {

>From af2ebac24519d4e049918419dc126c48125a1dc7 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Fri, 10 Oct 2025 11:17:21 +0900
Subject: [PATCH 3/3] Make StorageType private

---
 llvm/include/llvm/ADT/Bitset.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/llvm/include/llvm/ADT/Bitset.h b/llvm/include/llvm/ADT/Bitset.h
index 851ae19d12def..0dfeb2088dfa0 100644
--- a/llvm/include/llvm/ADT/Bitset.h
+++ b/llvm/include/llvm/ADT/Bitset.h
@@ -38,10 +38,7 @@ class Bitset {
   static constexpr unsigned NumWords =
       (NumBits + BitwordBits - 1) / BitwordBits;
 
-protected:
   using StorageType = std::array<BitWord, NumWords>;
-
-private:
   StorageType Bits{};
 
 protected: