[llvm] [Float2Int] Resolve FIXME: Pick the smallest legal type that fits (PR #79158)

[via llvm-commits]

AtariDreams wrote:

> int main() {
>     volatile int x = 1;
>     int c = (x > 0) ? 1 : 0;
>     return static_cast<unsigned char>(255.f * c);
> }

give me a sec to investigate.

https://github.com/llvm/llvm-project/pull/79158