fn:         fn,
		f:          f,
		vars:       vars,
		idx:        idx,
		stkptrsize: stkptrsize,
	}

	// Significant sources of allocation are kept in the ssa.Cache
	// and reused. Surprisingly, the bit vectors themselves aren't
	// a major source of allocation, but the liveness maps are.
	if lc, _ := f.Cache.Liveness.(*livenessFuncCache); lc == nil {
		// Prep the cache so liveness can fill it later.