[libc-commits] [libc] [libc] Change rand implementation so all tests pass in both 32- and 64-bit systems (PR #98692)

[Mikhail R. Gadelha via libc-commits]

mikhailramalho wrote:

> I still think these should just be separate functions, the constants aren't arbitrary and can't be mixed, making it a template is just confusing.

I can move the code to rand()'s body, wdyt? 
```
LLVM_LIBC_FUNCTION(int, rand, (void)) {
  unsigned long orig = rand_next.load(cpp::MemoryOrder::RELAXED);

  if constexpr (sizeof(void *) == sizeof(uint64_t)) {
    for (;;) {
      unsigned long x = orig;
      x ^= x >> 12;
      x ^= x << 25;
      x ^= x >> 27;
      if (rand_next.compare_exchange_strong(orig, x, cpp::MemoryOrder::ACQUIRE,
                                            cpp::MemoryOrder::RELAXED))
        return static_cast<int>((x * 0x2545F4914F6CDD1Dul) >> 32) & RAND_MAX;
      sleep_briefly();
    }
  } else {
    for (;;) {
      unsigned long x = orig;
      x ^= x >> 13;
      x ^= x << 27;
      x ^= x >> 5;
      if (rand_next.compare_exchange_strong(orig, x, cpp::MemoryOrder::ACQUIRE,
                                            cpp::MemoryOrder::RELAXED))
        return static_cast<int>(x * 1597334677ul) & RAND_MAX;
      sleep_briefly();
    }
  }
  __builtin_unreachable();
}
```


https://github.com/llvm/llvm-project/pull/98692