[llvm] [ADT] Modernize Bitset (NFC) (PR #162430)

[Jakub Kuderski via llvm-commits]

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@@ -28,9 +28,9 @@ namespace llvm {
 /// initialization.
 template <unsigned NumBits>
 class Bitset {
-  typedef uintptr_t BitWord;
+  using BitWord = uintptr_t;
 
-  enum { BITWORD_SIZE = (unsigned)sizeof(BitWord) * CHAR_BIT };
+  static constexpr unsigned BITWORD_SIZE = sizeof(BitWord) * CHAR_BIT;
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kuhar wrote:

While at it, can we add the unit to this define? It's not immediately obvious if it's bits or bytes unless you go to the definition. Maybe `BitwordBits` or `BitwordSizeInBits`?

https://github.com/llvm/llvm-project/pull/162430