Use 64bit int instead of emulation on metal (#8180)

Metal's popcount prototype is `T popcount(T x)` but we want to use it to
implement `countbits` where the prototype always returns `uint`.

Using `popcount` directly would implicitly cast successfully to the
32-bit return value in all cases except when the argument is a 64-bit
type. Thus, this change always explicitly casts the result to `$TR`,
which should be one of the `uint[N]` types, and should always be able to
hold the number of bits in the type.

Addresses #6877

0 files changed, 0 insertions, 0 deletions