Make gcmole execute in parallel.

tools/gcmole/gcmole.lua

 -- Copyright 2011 the V8 project authors. All rights reserved.
 -- Redistribution and use in source and binary forms, with or without
 -- modification, are permitted provided that the following conditions are
 -- met:
 --
 --     * Redistributions of source code must retain the above copyright
 --       notice, this list of conditions and the following disclaimer.
 --     * Redistributions in binary form must reproduce the above
 --       copyright notice, this list of conditions and the following
 --       disclaimer in the documentation and/or other materials provided
@@ skipping 16 matching lines @@
 
 -- This is main driver for gcmole tool. See README for more details.
 -- Usage: CLANG_BIN=clang-bin-dir lua tools/gcmole/gcmole.lua [arm|ia32|x64]
 
 local DIR = arg[0]:match("^(.+)/[^/]+$")
 
 local FLAGS = {
    -- Do not build gcsuspects file and reuse previously generated one.
    reuse_gcsuspects = false;
 
+   -- Don't use parallel python runner.
+   sequential = false;
+
    -- Print commands to console before executing them.
    verbose = false;
 
    -- Perform dead variable analysis (generates many false positives).
    -- TODO add some sort of whiteliste to filter out false positives.
    dead_vars = false;
 
    -- When building gcsuspects whitelist certain functions as if they
    -- can be causing GC. Currently used to reduce number of false
    -- positives in dead variables analysis. See TODO for WHITELIST
@@ skipping 57 matching lines @@
       .. (plugin_args or "")
       .. " -Xclang -triple -Xclang " .. triple
       .. " -D" .. arch_define
       .. " -DENABLE_DEBUGGER_SUPPORT"
       .. " -DV8_I18N_SUPPORT"
       .. " -I./"
       .. " -Ithird_party/icu/source/common"
       .. " -Ithird_party/icu/source/i18n"
 end
 
+function IterTable(t)

[Vyacheslav Egorov (Google), 2015/02/18 10:56:49]

I'd write it 

local function IterTable(t)
  return coroutine.wrap(function ()
    for i, v in ipairs(t) do
      coroutine.yield(v)
    end
  end)
end

or (which arguably is uglier)

local function IterTable(t)
  local f, n = ipairs(t), 0
  return function ()
    local v
    n, v = ipairs(t, n)
    return n
  end
end

but see the suggestion below which can eliminate the need for it entirely.

[Vyacheslav Egorov (Google), 2015/02/18 10:59:51]

my comment should obviously read:
at the end

[Michael Achenbach, 2015/02/18 14:48:59]

Done.

+   -- Iterator for arrays. Compatible with lua 5.0 and 5.1 as it doesn't
+   -- use getn.
+   local n = 0
+   for _ in pairs(t) do n = n + 1 end
+
+   local i = 0
+   return function ()
+      i = i + 1
+      if i <= n then return t[i] end
+   end
+end
+
+local function SplitResults(lines, func)
+   -- Splits the output of parallel.py and calls func on each result.
+   -- Bails out in case of an error in one of the executions.
+   local current = {}
+   local filename = ""
+   for line in lines do
+      local new_file = line:match "^______________ (.*)$"
+      local code = line:match "^______________ finish (%d+) ______________$"
+      if code then
+         if tonumber(code) > 0 then
+            log(table.concat(current, "\n"))
+            log("Failed to examine " .. filename)
+            return false
+         end
+         log("-- %s", filename)
+         func(filename, IterTable(current))
+      elseif new_file then
+         filename = new_file
+         current = {}
+      else
+         table.insert(current, line)
+      end
+   end
+   return true
+end
+
 function InvokeClangPluginForEachFile(filenames, cfg, func)
    local cmd_line = MakeClangCommandLine(cfg.plugin,
                                          cfg.plugin_args,
                                          cfg.triple,
                                          cfg.arch_define)
-   for _, filename in ipairs(filenames) do
-      log("-- %s", filename)
-      local action = cmd_line .. " " .. filename .. " 2>&1"
+   if FLAGS.sequential then
+      log("** Sequential execution.")

[Michael Achenbach, 2015/02/18 10:04:54]

This is the original piece of code c/p 1:1 (codereview not smart)

+      for _, filename in ipairs(filenames) do
+         log("-- %s", filename)
+         local action = cmd_line .. " " .. filename .. " 2>&1"
+         if FLAGS.verbose then print('popen ', action) end
+         local pipe = io.popen(action)
+         func(filename, pipe:lines())
+         local success = pipe:close()
+         if not success then error("Failed to run: " .. action) end
+      end
+   else
+      log("** Parallel execution.")
+      local parallel_cmd_line = {
+         "python",
+         "tools/gcmole/parallel.py",
+         "\"" .. cmd_line .. "\""
+      }
+      for _, filename in ipairs(filenames) do
+         table.insert(parallel_cmd_line, filename)
+      end
+      action = table.concat(parallel_cmd_line, " ")

[Vyacheslav Egorov (Google), 2015/02/18 10:56:49]

arguably you can just do

action = table.concat(parallel_cmd_line, " ") .. " " .. table.concat(filenames,
" ")

and kill the loop above

[Michael Achenbach, 2015/02/18 14:48:59]

Made it even shorter.

       if FLAGS.verbose then print('popen ', action) end
       local pipe = io.popen(action)
-      func(filename, pipe:lines())
-      local success = pipe:close()
+      local success = SplitResults(pipe:lines(), func) and pipe:close()

[Vyacheslav Egorov (Google), 2015/02/18 10:56:49]

pipe will not be closed if SplitResults returns false. 

[Michael Achenbach, 2015/02/18 14:48:59]

Done.

       if not success then error("Failed to run: " .. action) end
    end
 end
 
 -------------------------------------------------------------------------------
 -- GYP file parsing
 
 local function ParseGYPFile()
    local gyp = ""
    local gyp_files = { "tools/gyp/v8.gyp", "test/cctest/cctest.gyp" }
@@ skipping 203 matching lines @@
 local function CheckCorrectnessForArch(arch)
    local files = FilesForArch(arch)
    local cfg = ARCHITECTURES[arch]
 
    if not FLAGS.reuse_gcsuspects then
       GenerateGCSuspects(arch, files, cfg)
    end
 
    local processed_files = 0
    local errors_found = false
    local function SearchForErrors(filename, lines)

[Vyacheslav Egorov (Google), 2015/02/18 10:56:49]

if you change signature of this function and `parse` to (filename, iterator,
lines) and do

for l in iterator(lines) do ... end

then you can write

func(..., ipairs, current) instead of IterTable.

and 

func(..., pipe.lines, pipe) instead of func(..., pipe:lines())

[Michael Achenbach, 2015/02/18 11:42:03]

hmm but that would lead to
for l in ipairs(current) do ... end
and then l is a number not the value. I think I still need to wrap the iterator
somehow, either in the sequential case or the other - or is there another way?

[Vyacheslav Egorov (Google), 2015/02/18 11:58:11]

Yeah, true. Guh. 

Yeah, this does not work results are different, was stupid of me to suggest.
Sorry.

Then just a simpler IterTable is the only answer I have.

       processed_files = processed_files + 1
       for l in lines do
          errors_found = errors_found or
             l:match "^[^:]+:%d+:%d+:" or
             l:match "error" or
             l:match "warning"
          print(l)
       end
    end
 
@@ skipping 26 matching lines @@
 
 for _, arch in ipairs(ARCHS) do
    if not ARCHITECTURES[arch] then
       error ("Unknown arch: " .. arch)
    end
 
    errors = SafeCheckCorrectnessForArch(arch, report) or errors
 end
 
 os.exit(errors and 1 or 0)