import type { Loc } from "./ir/loc"
import type { SSA } from "./ir/ssa"

export type LivenessInfo = Array<Set<Loc>>

export const liveness = (block: Array<SSA>): LivenessInfo => {
    const info: LivenessInfo = []

    for (let i = block.length - 1; i >= 0; --i) {
        const insn = block[i]
        const last = info[i + 1] || new Set()

        info[i] = new Set()

        if (typeof insn.source !== "number") {
            info[i].add(insn.source)
        }

        if ("source1" in insn && typeof insn.source1 !== "number") {
            info[i].add(insn.source1)
        }

        last.forEach(loc => {
            if (loc === insn.dest) {
                return
            }

            info[i].add(loc)
        })
    }

    return info
}