Out params / Merge += with previous line

[laurentlb]

Input:

vec3 Segment(vec3 p, out float h)
{
  h = 2.;
  return p;
}
vec3 meter4(vec2 uv, float value) {
  float dummy;
  return Segment(uv.xyy, dummy);
}
vec3 dash(vec2 uv)
{
    vec3 color;
    color = vec3(1);
    color += meter4(uv, 1.);
    color += meter4(uv, 2.);
    return color;
}

Current output:

vec3 Segment(vec3 p,out float h)
{
  h=2.;
  return p;
}
vec3 meter4(vec2 uv,float value)
{
  return Segment(uv.xyy,value);
}
vec3 dash(vec2 uv)
{
  vec3 color=vec3(1);
  color+=meter4(uv,1.);
  return color+meter4(uv,2.);
}

The function dash is not simplified as much as it should be. It appears that the out parameter in Segment disables those optimizations.