# split_build.ludic - the program's IR compiled on every core: llvm-split cuts it into N parts, one
# clang each runs at once, and the link takes their objects where it took the one .ll. Most of a
# build was one clang -O2 on one file (the game: 32 s of 41). Needs an llvm-split and a clang of
# the same LLVM (a newer LLVM's parts do not read in an older clang): $LUDIC_LLVM (a bin directory),
# else Homebrew's. Anything missing, or a part that does not compile, falls back to the one clang.

function split_there(p: pointer) -> bool {
  let f = file_open(p, "rb")
  if f == null { return false }
  file_close(f)
  return true
}

# the LLVM bin directory to split with, or null (Windows' shell cannot run the parts at once yet)
function split_dir() -> pointer {
  if host_is_windows() { return null }
  if getenv_or("LUDIC_SPLIT", "1") == "0" { return null }
  let d = getenv_or("LUDIC_LLVM", "/opt/homebrew/opt/llvm/bin")
  if not split_there(`{d}/llvm-split`) or not split_there(`{d}/clang`) { return null }
  return d
}

# how many parts: $LUDIC_JOBS, else the cores, no more than the free memory allows at 1.5 GB a clang
function split_jobs(tmp: pointer) -> int {
  let j = getenv("LUDIC_JOBS")
  if j != null { return split_int(j) }
  let probe = `{tmp}.cores`
  let aw = "awk '/Pages free/{f=$3} /Pages inactive/{i=$3} END{print int((f+i)*p/1073741824)}'"
  run(`echo $(sysctl -n hw.ncpu) $(vm_stat | {aw} p=$(sysctl -n hw.pagesize)) > "{probe}" 2>/dev/null`)
  let f = file_open(probe, "rb")
  if f == null { return 1 }
  let buf = bytes(64)
  let n = file_read(f, buf, 63)
  file_close(f)
  remove_file(`"{probe}"`)
  if n <= 0 { return 1 }
  buf[n] = 0
  var cores = 0
  var i = 0
  while i < n and buf[i] >= '0' and buf[i] <= '9' { cores = cores * 10 + (buf[i] - '0');  i += 1 }
  while i < n and buf[i] == ' ' { i += 1 }
  var gb = 0
  while i < n and buf[i] >= '0' and buf[i] <= '9' { gb = gb * 10 + (buf[i] - '0');  i += 1 }
  let by_mem = (gb * 2) / 3
  if by_mem < cores { return by_mem }
  return cores
}
function split_int(s: pointer) -> int {
  var v = 0
  var i = 0
  while i < len(s) and s[i] >= '0' and s[i] <= '9' { v = v * 10 + (s[i] - '0');  i += 1 }
  return v
}

# the IR at `ll` compiled in parts at -O`opt`: their objects, quoted and space-separated, for the
# link to take in place of the .ll; null when it was not split (the caller compiles the .ll whole)
function split_compile(ll: pointer, out: pointer, opt: pointer) -> pointer {
  let d = split_dir()
  if d == null { return null }
  let n = split_jobs(out)
  if n < 2 { return null }
  let pre = `{out}.part`
  if run(`"{d}/llvm-split" -j {n} -o "{pre}" "{ll}"`) != 0 { return null }
  var sh = ""
  var i = 0
  while i < n {
    sh = sh + `"{d}/clang" -x ir -O{opt} -mmacosx-version-min=11.0 -Wno-override-module -Wno-missing-sysroot -c "{pre}{itoa(i)}" -o "{pre}{itoa(i)}.o" & `
    i += 1
  }
  run(`/bin/sh -c '{sh}wait'`)
  var objs = ""
  var ok = true
  i = 0
  while i < n {
    remove_file(`"{pre}{itoa(i)}"`)
    if not split_there(`{pre}{itoa(i)}.o`) { ok = false }
    objs = objs + ` "{pre}{itoa(i)}.o"`
    i += 1
  }
  if not ok {
    split_clean(out)
    return null
  }
  return objs
}
# the parts' objects, once linked (or when a part failed)
function split_clean(out: pointer) -> void { run(`rm -f "{out}".part*.o`) }