+The functions in this built-in module control the behavior of the JIT +compiler engine. Note that JIT-compilation is fully automatic — +you probably won't need to use any of the following functions unless +you have special needs. +
+ +jit.on()
+jit.off()
++Turns the whole JIT compiler on (default) or off. +
++These functions are typically used with the command line options +-j on or -j off. +
+ +jit.flush()
++Flushes the whole cache of compiled code. +
+ +jit.on(func|true [,true|false])
+jit.off(func|true [,true|false])
+jit.flush(func|true [,true|false])
++jit.on enables JIT compilation for a Lua function (this is +the default). +
++jit.off disables JIT compilation for a Lua function and +flushes any already compiled code from the code cache. +
++jit.flush flushes the code, but doesn't affect the +enable/disable status. +
++The current function, i.e. the Lua function calling this library +function, can also be specified by passing true as the first +argument. +
++If the second argument is true, JIT compilation is also +enabled, disabled or flushed recursively for all sub-functions of a +function. With false only the sub-functions are affected. +
++The jit.on and jit.off functions only set a flag +which is checked when the function is about to be compiled. They do +not trigger immediate compilation. +
++Typical usage is jit.off(true, true) in the main chunk +of a module to turn off JIT compilation for the whole module for +debugging purposes. +
+ +jit.flush(tr)
++Flushes the root trace, specified by its number, and all of its side +traces from the cache. The code for the trace will be retained as long +as there are any other traces which link to it. +
+ +status, ... = jit.status()
++Returns the current status of the JIT compiler. The first result is +either true or false if the JIT compiler is turned +on or off. The remaining results are strings for CPU-specific features +and enabled optimizations. +
+ +jit.version
++Contains the LuaJIT version string. +
+ +jit.version_num
++Contains the version number of the LuaJIT core. Version xx.yy.zz +is represented by the decimal number xxyyzz. +
+ +jit.os
++Contains the target OS name: +"Windows", "Linux", "OSX", "BSD", "POSIX" or "Other". +
+ +jit.arch
++Contains the target architecture name: +"x86", "x64" or "ppcspe". +
+ +jit.opt.* — JIT compiler optimization control
++This sub-module provides the backend for the -O command line +option. +
++You can also use it programmatically, e.g.: +
+
+jit.opt.start(2) -- same as -O2
+jit.opt.start("-dce")
+jit.opt.start("hotloop=10", "hotexit=2")
+
++Unlike in LuaJIT 1.x, the module is built-in and +optimization is turned on by default! +It's no longer necessary to run require("jit.opt").start(), +which was one of the ways to enable optimization. +
+ +jit.util.* — JIT compiler introspection
++This sub-module holds functions to introspect the bytecode, generated +traces, the IR and the generated machine code. The functionality +provided by this module is still in flux and therefore undocumented. +
++The debug modules -jbc, -jv and -jdump make +extensive use of these functions. Please check out their source code, +if you want to know more. +
++