perf: pre-compile embedded Lua source into bytecode (#16631)

The Lua modules that make up vim.lua are embedded as raw source files into the
nvim binary. These sources are loaded by the Lua runtime on startuptime. We can
pre-compile these sources into Lua bytecode before embedding them into the
binary, which minimizes the size of the binary and improves startuptime.

1 files changed, 36 insertions, 14 deletions

diff --git a/src/nvim/generators/gen_char_blob.lua b/src/nvim/generators/gen_char_blob.lua
index a7dad50d48..70c034abc5 100644
--- a/src/nvim/generators/gen_char_blob.lua
+++ b/src/nvim/generators/gen_char_blob.lua
@@ -1,12 +1,26 @@
 if arg[1] == '--help' then
   print('Usage:')
-  print('  '..arg[0]..' target source varname [source varname]...')
+  print('  '..arg[0]..' [-c] target source varname [source varname]...')
   print('')
   print('Generates C file with big uint8_t blob.')
   print('Blob will be stored in a static const array named varname.')
   os.exit()
 end
 
+-- Recognized options:
+--   -c   compile Lua bytecode
+local options = {}
+
+while true do
+  local opt = string.match(arg[1], "^-(%w)")
+  if not opt then
+    break
+  end
+
+  options[opt] = true
+  table.remove(arg, 1)
+end
+
 assert(#arg >= 3 and (#arg - 1) % 2 == 0)
 
 local target_file = arg[1] or error('Need a target file')
@@ -23,11 +37,25 @@ for argi = 2, #arg, 2 do
   end
   varnames[varname] = source_file
 
-  local source = io.open(source_file, 'r')
-      or error(string.format("source_file %q doesn't exist", source_file))
-
   target:write(('static const uint8_t %s[] = {\n'):format(varname))
 
+  local output
+  if options.c then
+    local luac = os.getenv("LUAC_PRG")
+    if luac then
+      output = io.popen(luac:format(source_file), "r"):read("*a")
+    else
+      print("LUAC_PRG is undefined")
+    end
+  end
+
+  if not output then
+    local source = io.open(source_file, "r")
+        or error(string.format("source_file %q doesn't exist", source_file))
+    output = source:read("*a")
+    source:close()
+  end
+
   local num_bytes = 0
   local MAX_NUM_BYTES = 15  -- 78 / 5: maximum number of bytes on one line
   target:write(' ')
@@ -41,19 +69,13 @@ for argi = 2, #arg, 2 do
     end
   end
 
-  for line in source:lines() do
-    for i = 1, string.len(line) do
-      local byte = line:byte(i)
-      assert(byte ~= 0)
-      target:write(string.format(' %3u,', byte))
-      increase_num_bytes()
-    end
-    target:write(string.format(' %3u,', string.byte('\n', 1)))
+  for i = 1, string.len(output) do
+    local byte = output:byte(i)
+    target:write(string.format(' %3u,', byte))
     increase_num_bytes()
   end
 
-  target:write('   0};\n')
-  source:close()
+  target:write('  0};\n')
 end
 
 target:close()