Liveness & copies

[vbgl]

Register allocation sees that x and y conflict and therefore does not consider allocating them to the same register, hence fails at compiling this program:

param int N = 13;
export fn test(reg u64 out y) {
  reg u64 x;
  reg u64[N] t;
  inline int i;
  for i = 0 to N { t[i] = i; }
  x = y;
  x += y;
  [out] = x;
  for i = 1 to N { t[0] += t[i]; }
  [out] = t[0];
}

[vbgl]

This is related to coalescing.