A "high-level" language for the Gameboy
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import { colorGreedy, createGraph, Graph, maxCardinalitySearch } from "./data/graph"
import { setEquals, union } from "./data/set"
import { BasicBlock } from "./ir/block"
import { Loc } from "./ir/loc"
import { StackOffset } from "./sm83/cpu"
export type LivenessInfo = Array<Set<Loc>>
export const liveness = (block: BasicBlock): LivenessInfo => {
const info: LivenessInfo = []
info[block.insns.length] = new Set()
for (let i = block.insns.length - 1; i >= 0; --i) {
const insn = block.insns[i]
const last = info[i + 1]
info[i] = new Set()
if (insn.type === "goto") {
continue
}
if ("source" in insn && typeof insn.source !== "number") {
info[i].add(insn.source)
}
last.forEach(loc => {
if (insn.dest instanceof Loc && loc.ppName() === insn.dest.ppName()) {
return
}
info[i].add(loc)
})
}
let dirty = true
while (dirty) {
dirty = false
for (let i = block.insns.length - 1; i >= 0; --i) {
if (block.insns[i].type !== "goto") {
continue
}
const labelSet = info[getLabelIndex(block, block.insns[i].dest as string)]
if (setEquals(info[i], labelSet)) {
continue
}
dirty = true
info[i] = union(info[i], labelSet)
}
}
return info
}
export const getLabelIndex = (block: BasicBlock, label: string): number => {
let idx = -1
for (let i = 0; i < block.insns.length; ++i) {
if (block.insns[i].type === "label" && block.insns[i].dest === label) {
idx = i
break
}
}
return idx
}
export const interference = (block: BasicBlock, live: LivenessInfo): Graph<Loc> =>
createGraph((v, e) => {
block.locs().forEach(loc => {
v(loc.ppName(), loc)
})
block.insns.forEach((insn, i) =>
live[i + 1].forEach(u => {
if (insn.dest instanceof Loc && insn.dest.ppName() !== u.ppName()) {
e(insn.dest.ppName(), u.ppName())
}
})
)
})
export type RegAlloc = {
[s: string]: string | StackOffset,
}
export const allocateRegisters = (block: BasicBlock, registers: Array<string>): RegAlloc => {
const info = liveness(block)
const graph = interference(block, info)
const ordering = maxCardinalitySearch(graph)
const coloring = colorGreedy(graph, ordering)
const allocation: RegAlloc = {}
const availableRegisters = new Set(registers)
const colorMap: { [c: number]: string | StackOffset } = {}
let nextStackOffset = 0
Object.entries(coloring.colors).forEach(([vertex, color]) => {
if (typeof colorMap[color] !== 'undefined') {
allocation[vertex] = colorMap[color]
return
}
let value = null
if (availableRegisters.size == 0) {
value = { offset: nextStackOffset++ }
} else {
const result = availableRegisters.values().next()
value = result.value
availableRegisters.delete(value)
}
allocation[vertex] = value
colorMap[color] = value
})
return allocation
}