[libc] Fix implicit conversion warnings.

libc/src/__support/CPP/bit.h

@@ -162,7 +162,7 @@ ADD_SPECIALIZATION(countl_zero, unsigned long long, __builtin_clzll)
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
 countl_one(T value) {
-  return cpp::countl_zero<T>(~value);
+  return cpp::countl_zero<T>(static_cast<T>(~value));
 }
 
 /// Count the number of ones from the least significant bit to the first
@@ -175,7 +175,7 @@ countl_one(T value) {
 template <typename T>
 [[nodiscard]] LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_unsigned_v<T>, int>
 countr_one(T value) {
-  return cpp::countr_zero<T>(~value);
+  return cpp::countr_zero<T>(static_cast<T>(~value));
 }
 
 /// Returns the number of bits needed to represent value if value is nonzero.

libc/src/__support/float_to_string.h

@@ -287,7 +287,7 @@ LIBC_INLINE UInt<MID_INT_SIZE> get_table_negative(int exponent, size_t i) {
   size_t ten_blocks = i;
   size_t five_blocks = 0;
   if (shift_amount < 0) {
-    int block_shifts = (-shift_amount) / BLOCK_SIZE;
+    int block_shifts = (-shift_amount) / static_cast<int>(BLOCK_SIZE);
     if (block_shifts < static_cast<int>(ten_blocks)) {
       ten_blocks = ten_blocks - block_shifts;
       five_blocks = block_shifts;