s.allocatable &^= 1 << s.SPReg
	s.allocatable &^= 1 << s.SBReg
	if s.f.Config.hasGReg {
		s.allocatable &^= 1 << s.GReg
	}
	if buildcfg.FramePointerEnabled && s.f.Config.FPReg >= 0 {
		s.allocatable &^= 1 << uint(s.f.Config.FPReg)
	}
	if s.f.Config.LinkReg != -1 {
		if isLeaf(f) {
			// Leaf functions don't save/restore the link register.
			s.allocatable &^= 1 << uint(s.f.Config.LinkReg)
		}
	}