libraryDocs / jit

jit

librarysharedsource

The jit library is a standard Lua library which provides functions to manipulate the JIT compiler.

It's a wrapper for the native jit library from LuaJIT.

[SHARED AND MENU]

Sets the JIT compiler optimization flags and parameters.

It's an alias for jit.opt.start.

Flags: "-O0".."-O3", "+fold", "-dce", "+loop", "-abc", etc.

Parameters: "maxtrace=1000", "hotloop=56", "maxmcode=8192", etc.

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Fields

Name	Type	Description
`version_number`	`integer`	The version of the JIT compiler as a number, e.g. `20100` for `2.1.0`, `0` if not available.
`edge`	`boolean`	`true` if the JIT compiler is an edge version (LuaJIT 2.1+), `false` otherwise. = `false`
`version_byte`	`integer`	The major version of the JIT compiler: `1` for LuaJIT 2.0, `2` for LuaJIT 2.1+, `0` if unknown. = `0`
`os`	`"Windows" \| "Linux" \| "OSX" \| "BSD" \| "POSIX" \| "Other" \| "unknown" \| string`	The target OS name, `"unknown"` if not available.
`arch`	`"x86" \| "x64" \| "arm" \| "arm64" \| "arm64be" \| "ppc" \| "ppc64" \| "ppc64le" \| "mips" \| "mipsel" \| "mips64" \| "mips64el" \| "unknown" \| string`	The target architecture name, `"unknown"` if not available.
`version`	`string \| "unknown"`	The full name of the JIT compiler version, e.g. `"LuaJIT 2.1.0-beta3"`, `"unknown"` if not available.
`options`	`fun( ...: string )`

Functions

`jit.getfbc`	Returns the bytecode instruction at the given position of the given Lua function.
`jit.getfconst`	Returns the constant at the given index of the given Lua function.
`jit.getfinfo`	Returns the LuaJIT internal information about the given function.
`jit.getfupvalue`	Returns the name of the upvalue at the given index of the given Lua function.
`jit.isFFI`	Checks if the given function is a FFI function.
`jit.options`

#jit.getfbc

sharednodiscardsource

function jit.getfbc(location: function | integer, position: integer): integer | nil, integer | nil

Returns the bytecode instruction at the given position of the given Lua function.

Returns nil if the position is out of range or the function is not a Lua function.

Parameters

Name	Type	Description
`location`	`function \| integer`	The function or the stack level to get the main function from.
`position`	`integer`	The bytecode position (program counter), starting from `0`.

Returns

Type	Name	Description
`integer \| nil`	`ins`	The raw 32-bit bytecode instruction.
`integer \| nil`	`mode`	The opcode mode flags of the instruction.

#jit.getfconst

sharednodiscardsource

function jit.getfconst(location: function | integer, position: integer): any | nil

Returns the constant at the given index of the given Lua function.

Non-negative indices are for number constants, negative indices are for GC constants (strings, tables, child prototypes, etc.).

Returns nil if the index is out of range.

Parameters

Name	Type	Description
`location`	`function \| integer`	The function or the stack level to get the main function from.
`position`	`integer`	The index of the constant.

Returns

Type	Name	Description
`any \| nil`	`value`	The constant value.

#jit.getfinfo

sharednodiscardsource

function jit.getfinfo(location: function | integer, position?: integer): jit.funcinfo.c | jit.funcinfo.lua

Returns the LuaJIT internal information about the given function.

For Lua functions returns jit.funcinfo.lua (lines, stack slots, params, bytecodes count, constants, source, etc.), if position is given, currentline and loc will be related to the bytecode at this position.

For C functions returns jit.funcinfo.c (address, upvalues count and ffid for builtin fast functions).

Parameters

Name	Type	Description
`location`	`function \| integer`	The function or the stack level to get the main function from.
`position`optional	`integer`	The bytecode position (program counter) inside the function.

Returns

Type	Name	Description
`jit.funcinfo.c \| jit.funcinfo.lua`	`info`	The function information.

#jit.getfupvalue

sharednodiscardsource

function jit.getfupvalue(location: function | integer, position: integer): string | nil

Returns the name of the upvalue at the given index of the given Lua function.

Returns nil if the index is out of range.

Parameters

Name	Type	Description
`location`	`function \| integer`	The function or the stack level to get the main function from.
`position`	`integer`	The index of the upvalue, starting from `0`.

Returns

Type	Name	Description
`string \| nil`	`name`	The name of the upvalue.

#jit.isFFI

sharednodiscardsource

function jit.isFFI(fn: function): boolean

Checks if the given function is a FFI function.

Fallback, jit.util is not available, so any C function is treated as a fast function.

Parameters

Name	Type	Description
`fn`	`function`	The function to check.

Returns

Type	Name	Description
`boolean`	`is_ffi`	`true` if the function is a FFI function, `false` otherwise.

#jit.options

source

function jit.options()

Alias of debug.fempty.