Program flow graph printer using luacheck.flow

pfg.lua

-- Requires luacheck scm-6
-- Reads a Lua program from stdin, prints program flow graph for top level closure.
-- Format: node id: (ids of previous nodes) -> ast node tag:line:column -> (ids of next nodes)
-- Crashes on `break` or `goto` or labels.
local flow = require "luacheck.flow"
local parser = require "metalua.compiler".new()

local src = assert(io.stdin:read("*a"))
local ast = assert(parser:src_to_ast(src))
local intel = {closures = {{stmts = ast}}, gotos = {}}
flow(intel)

local node_to_i = {}

for i=1, #intel.flow_nodes do
   local node = intel.flow_nodes[i]
   node_to_i[node] = i

   if node.ast_node then
      node.ast_node = ("%s:%d:%d"):format(node.ast_node.tag or "Block",
         node.ast_node.lineinfo.first.line,
         node.ast_node.lineinfo.first.column)
   end
end

local function pad(s, l)
   return s .. (" "):rep(math.max(l-#s, 0))
end

local function tuple(t)
   return "("..table.concat(t, ",")..")"
end

for i, node in ipairs(intel.flow_nodes) do
   local prevs = {}

   for _, prev in ipairs(node.prevs) do
      table.insert(prevs, tostring(node_to_i[prev]))
   end

   local nexts = {}

   for _, next_ in ipairs(node.nexts) do
      table.insert(nexts, tostring(node_to_i[next_]))
   end

   print(("%s %s  ->  %s  ->  %s"):format(
      pad(i..":", 4),
      pad(tuple(prevs), 10),
      pad(node.ast_node or "Virtual", 15),
      pad(tuple(nexts), 10)
   ))
end