b.c

// Test case for Xcode 11 broken stack alignment
// See https://forums.developer.apple.com/thread/121887
// Compile with `cc -mavx -O2 a.c`

int main(void) {
  register char a __asm("rbx") = 0;
  char b[5000];
  char c[100] = {0};
  asm volatile("" : : "r,m"(a), "r,m"(b), "r,m"(c) : "memory");
  return 0;
}