LuaVela Compiler Support

Introduction

Note

This page originates from the LuaJIT 2.0 NYI reference.

All aspects of Lua are implemented in interpreter, but not all of them are implemented in JIT compiler. This page serves as a quick reference to identify whether certain things are compiled or not.

It’s not a stated goal to compile everything, since the interpreter is fast enough for many tasks. And speed doesn’t matter for anything that’s done only a couple of times during the runtime of a program. E.g. it would be absolutely pointless to compile require() or module() (in fact, these should eventually be rewritten as plain Lua functions).

However, the number of JIT-compiled cases will grow over time, based on demand and user feedback.

The following tables provide an indication whether a feature is JIT-compiled or not:

• yes: Always JIT-compiled.

• partial: May be JIT-compiled, depending on the circumstances. Otherwise will fall back to the interpreter.

• no: Not JIT-compiled (yet), will always fall back to the interpreter.

• never: Ditto. Will not be JIT-compiled, even in future versions.

Bytecode

Almost all bytecodes are compiled, except for these:

Bytecode	Compiled?	Remarks
CALLT	partial	Tailcall. Some tailcalls to frames lower than the starting frame of the trace are not compiled.
CAT	partial	Concatenation operator ... Compiled with -Ojitcat. __concat metamethod is not compiled.
FNEW	no	Create closure.
FUNC*	partial	Call built-in function. See below.
ISNEXT	yes	Check for next() loop optimization. Compiled with -Ojitpairs enabled (since 0.22).
ITERN	partial	Optimized call to next() in a loop. Compiled with -Ojitpairs enabled except for the last iteration (since 0.22).
RET*	partial	Return from function. Returns to C frames and some returns to frames lower than the starting frame of the trace are not compiled.
TSETM	no	Initialize table with multiple return values. Compiled in LuaJIT 2.1.
UCLO	no	Close upvalues.
VARG	partial	Vararg operator .... Multi-result VARG is only compiled when used with select().

Notes:

• Table accesses to mixed dense/sparse tables are not compiled.

• Bytecode execution that would cause an error in the interpreter is never compiled.

Libraries

The following tables list whether or not calls to the various built-in library functions will get compiled. This may depend on the arguments passed (esp. their types) and the exact circumstances of the call.

Base Library

Function	Compiled?	Remarks
assert	yes
collectgarbage	no
dofile	never
error	never
gcinfo	no
getfenv	partial	Only getfenv(0) is compiled.
getmetatable	yes
ipairs	yes
load	never
loadfile	never
loadstring	never
module	never
newproxy	never
next	partial	Compiled with -Ojitpairs except for the case when the last element is passed as a second arg (since 0.22).
pairs	yes	Compiled with -Ojitpairs (since 0.22).
pcall	yes
print	no
rawequal	yes
rawget	yes
rawlen	yes
rawset	yes
require	never
select	partial	Only compiled when the 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	Compiled in LuaJIT 2.1.
string.dump	never
string.find	partial	Compiled for plain string searches (no patterns) with -Ojitstr (since 0.20).
string.format	partial	Compiled for non-%p and non-string arguments for %s.
string.gmatch	no
string.gsub	no
string.len	yes
string.lower	yes	Compiled with -Ojitstr (since 0.20).
string.match	no
string.rep	no	Compiled in LuaJIT 2.1.
string.reverse	no	Compiled in LuaJIT 2.1.
string.sub	yes
string.upper	yes	Compiled with -Ojitstr (since 0.20).

Table Library

Function	Compiled?	Remarks
table.concat	yes	Compiled with -Ojittabcat (since 0.20).
table.foreach	never	Deprecated in Lua 5.1. Use pairs() instead.
table.foreachi	never	Deprecated in Lua 5.1. Use ipairs() instead, which is compiled.
table.getn	yes
table.insert	partial	Only when pushing.
table.maxn	no
table.pack	no
table.remove	partial	Only when popping; compiled in LuaJIT 2.1.
table.sort	no
table.unpack	no

Math Library

Function	Compiled?	Remarks
math.abs	yes
math.acos	yes	Since 0.23.
math.asin	yes	Since 0.23.
math.atan	yes	Since 0.23.
math.atan2	yes	Since 0.23.
math.ceil	yes
math.cos	yes
math.cosh	yes	Since 0.23.
math.deg	yes
math.exp	yes
math.floor	yes
math.fmod	no
math.frexp	no
math.huge	yes
math.ldexp	yes
math.log	yes
math.log10	yes
math.max	yes
math.min	yes
math.mod	no	Same as math.fmod.
math.modf	no
math.pi	yes
math.pow	yes
math.rad	yes
math.random	yes
math.randomseed	no
math.sin	yes
math.sinh	yes	Since 0.23.
math.sqrt	yes
math.tan	yes
math.tanh	yes	Since 0.23.

IO Library

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

Bit Library

Function	Compiled?	Remarks
bit.arshift	yes
bit.band	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	Compiled in LuaJIT 2.1.

FFI Library

Function	Compiled?	Remarks
ffi.alignof	yes
ffi.abi	yes	Since 0.22.
ffi.cast	partial	Same restrictions as ffi.new (casting is a form of cdata creation).
ffi.cdef	never
ffi.copy	yes
ffi.errno	partial	Not when setting a new value.
ffi.fill	yes
ffi.gc	partial	Not when clearing a finalizer. Compiled in LuaJIT 2.1.
ffi.istype	yes
ffi.load	never
ffi.metatype	never
ffi.new	partial	2.0: Not for VLA/VLS, > 8 byte alignment or > 128 bytes.
ffi.offsetof	yes
ffi.sizeof	partial	Not for VLA/VLS types (see below).
ffi.string	yes
ffi.typeof	partial	Only for cdata arguments. Never for cdecl strings.

Coroutine Library

No functions are compiled.

OS Library

No functions are compiled.

Package Library

No functions are compiled.

Debug Library

Function	Compiled?	Remarks
debug.getmetatable	no	Compiled in LuaJIT 2.1.
debug.*	no/never	Unlikely to change.

JIT Library

No functions are compiled.

uJIT Library

Function	Compiled?	Remarks
ujit.coverage.pause	never
ujit.coverage.start	never
ujit.coverage.stop	never
ujit.coverage.unpause	never
ujit.debug.gettableinfo	never
ujit.dump.bc	never
ujit.dump.bcins	never
ujit.dump.mcode	never
ujit.dump.stack	never
ujit.dump.start	never
ujit.dump.stop	never
ujit.dump.trace	never
ujit.getmetrics	no
ujit.immutable	yes	Since 0.18.
ujit.iprof.start	no
ujit.iprof.stop	no
ujit.math.isfinite	yes
ujit.math.isinf	yes
ujit.math.isnan	yes
ujit.math.isninf	yes
ujit.math.ispinf	yes
ujit.math.nan	yes
ujit.memprof.start	never
ujit.memprof.stop	never
ujit.profile.available	never
ujit.profile.init	never
ujit.profile.start	never
ujit.profile.stop	never
ujit.profile.terminate	never
ujit.seal	no
ujit.string.split	no
ujit.string.trim	yes
ujit.table.keys	yes	Since 0.20, via IR_CALLL.
ujit.table.rindex	partial	Since 0.23, compiles for tables without metatables (including nested lookups).
ujit.table.shallowcopy	yes	Since 0.20, via IR_TDUP.
ujit.table.size	yes	Since 0.22, via IR_CALLL.
ujit.table.toset	yes	Since 0.20, via IR_CALLL.
ujit.table.values	yes	Since 0.20, via IR_CALLL.
ujit.usesfenv	no