[llvm] [libc] [libc] Add more functions in CPP/bit.h (PR #73814)

[Clement Courbet via llvm-commits]

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@@ -36,41 +36,53 @@ template <> class numeric_limits<int> {
 public:
   LIBC_INLINE static constexpr int max() { return INT_MAX; }
   LIBC_INLINE static constexpr int min() { return INT_MIN; }
+  LIBC_INLINE_VAR static constexpr int digits = CHAR_BIT * sizeof(int) - 1;
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legrosbuffle wrote:

Refactor all these to a `consteval int digits_for<T>()` ? Or maybe even:

```
template <> class numeric_limits<int> : public numeric_limits_impl<int, INT_MAX, INT_MIN> {};
```

and derive everything in `numeric_limits_impl` ?

https://github.com/llvm/llvm-project/pull/73814