}
			// Count arguments which will need a register.
			narg := 0
			for _, a := range v.Args {
				// SP and SB are special registers and have no effect on
				// the allocation of general-purpose registers.
				if a.needRegister() && a.Op != OpSB && a.Op != OpSP {
					narg++
				}
			}
			if narg >= 2 && !v.Type.IsFlags() {
				// Don't move values with more than one input, as that may
				// increase register pressure.

				// tail call is not counted as it does not save the return PC or need a frame
				return false
			}
		}
	}
	return true
}

// needRegister reports whether v needs a register.
func (v *Value) needRegister() bool {
	return !v.Type.IsMemory() && !v.Type.IsVoid() && !v.Type.IsFlags() && !v.Type.IsTuple()
}

func (s *regAllocState) init(f *Func) {
	s.f = f