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Not Yet Implemented

All aspects of Lua are implemented in LuaJIT's interpreter, but not all of them are implemented in LuaJIT's JIT compiler. This page serves as a quick reference to identify whether certain things are implemented or not. Hopefully meaning that you can avoid them in performance-critical code rather than puzzle over why you're seeing poorly performing code and NYI messages from -jv.


The following tables list whether or not calls to various library functions will get compiled:

  • yes - Calls to these functions are always JIT-compiled.
  • partial - Depending on the arguments and circumstances, some calls can be JIT-compiled, others will fall back to the interpreter.
  • no - Calls to these functions will not be JIT-compiled, and will always fall back to the interpreter.

Base Library

Function Compiled? Remarks
assert **yes**
collectgarbage no
dofile no
error no
getfenv no
getmetatable **yes**
ipairs partial Won't compile if string coercion is invoked.
load no
loadfile no
loadstring no
next no
pairs no
pcall **yes**
print no
rawequal **yes**
rawget **yes**
rawset **yes**
select partial Only compiled when first argument is a constant.
setfenv no
setmetatable **yes**
tonumber partial Won't compile for bases other than 10, other exceptions apply.
tostring partial Only compiled for strings, numbers, booleans, nil, and values with a __tostring metamethod.
type **yes**
unpack no
xpcall **yes**

String Library

Function Compiled? Remarks
string.byte **yes**
string.char no
string.dump no
string.find no
string.format no
string.gmatch no
string.gsub no
string.len **yes**
string.lower no
string.match no
string.rep no
string.reverse no
string.sub **yes**
string.upper no

Table Library

Function Compiled? Remarks
table.concat no
table.foreach no
table.foreachi no
table.getn **yes**
table.insert partial Only when pushing.
table.maxn no
table.remove partial Only when popping.
table.sort no

Math Library

Function Compiled? Remarks
math.abs **yes**
math.acos **yes**
math.asin **yes**
math.atan **yes**
math.atan2 **yes**
math.ceil **yes**
math.cos **yes**
math.cosh **yes**
math.deg **yes**
math.exp **yes**
math.floor **yes**
math.fmod no
math.frexp no
math.ldexp **yes**
math.log **yes**
math.log10 **yes**
math.max **yes**
math.min **yes**
math.modf **yes**
math.pow **yes**
math.rad **yes**
math.random **yes**
math.randomseed no
math.sin **yes**
math.sinh **yes**
math.sqrt **yes**
math.tan **yes**
math.tanh **yes**

IO Library

Function Compiled? Remarks
io.close no
io.flush **yes**
io.input no
io.lines no no
io.output no
io.popen no no
io.tmpfile no
io.type no
io.write **yes**

Bit Library

Function Compiled? Remarks
bit.arshift **yes** **yes**
bit.bnot **yes**
bit.bor **yes**
bit.bswap **yes**
bit.bxor **yes**
bit.lshift **yes**
bit.rol **yes**
bit.ror **yes**
bit.rshift **yes**
bit.tobit **yes**
bit.tohex no

FFI Library

Function Compiled? Remarks
ffi.alignof no
ffi.abi **yes**
ffi.cast partial Same restrictions as (as casting is a form of cdata creation).
ffi.cdef no
ffi.copy **yes**
ffi.errno partial Not when setting a new value.
ffi.fill **yes**
ffi.gc no
ffi.istype **yes**
ffi.load no
ffi.metatype no partial Not when the allocation is for more than 64 bytes, other exceptions apply.
ffi.offsetof no
ffi.sizeof no
ffi.string **yes**
ffi.typeof no

Coroutine Library

No functions are compiled.

OS Library

No functions are compiled.

Package Library

No functions are compiled.

Debug Library

No functions are compiled.

JIT Library

No functions are compiled.