LuaJIT

Last updated
LuaJIT
Original author(s) Mike Pall
Stable release
v2.1.ROLLING [1] / August 21, 2023;2 years ago (2023-08-21)
Repository github.com/LuaJIT/LuaJIT
Written in C, Lua
Operating system Unix-like, MacOS, Windows, iOS, Android, PlayStation
Platform x86, x86-64, PowerPC, ARM, MIPS [2]
Type Just-in-time compiler
License MIT License [3]
Website luajit.org

LuaJIT is a tracing just-in-time compiler and interpreter for the Lua programming language.

Contents

History

The LuaJIT project was started in 2005 by developer Mike Pall, released under the MIT open source license. [4]

The second major release of the compiler, 2.0.0, featured major performance increases. [5]

LuaJIT uses rolling releases. Mike Pall, the creator and maintainer recommends using the tip of the v2.1 branch, and does not believe in releases. [6]

Mike Pall resigned in 2015 making only occasional patching to the future 2.1 version since then. [7]

Notable users

Performance

LuaJIT is often the fastest Lua runtime. [13] LuaJIT has also been named the fastest implementation of a dynamic programming language. [14] [15]

LuaJIT includes a Foreign Function Interface compatible with C data structures. Its use is encouraged for numerical computation. [16]

Tracing

LuaJIT is a tracing just-in-time compiler. LuaJIT chooses loops and function calls as trace anchors to begin recording possible hot paths. Function calls will require twice as many invocations to begin recording as a loop. Once LuaJIT begins recording, all control flow, including jumps and calls, are inlined to form a linear trace. All executed bytecode instructions are stored and incrementally converted into LuaJIT's static single-assignment intermediate representation. LuaJIT's trace compiler is often capable of inlining and removing dispatches from object orientation, operators, and type modifications. [17]

Internal representation

LuaJIT uses two types of internal representation. A stack-based bytecode is used for the interpreter, and a static single-assignment form is used for the just-in-time compiler. The interpreter bytecode is frequently patched by the JIT compiler, often to begin executing a compiled trace or to mark a segment of bytecode for causing too many trace aborts. [15] 

-- Loop with if-statementlocalx=0fori=1,1e4dox=x+11ifi%10==0then-- if-statementx=x+22endx=x+33end
---- TRACE 1 start Ex.lua:5---- TRACE 1 IR0001 int SLOAD #2 CI0002 > num SLOAD #1 T0003 num ADD 0002 +110004 int MOD 0001 +100005 > int NE 0004 +00006 + num ADD 0003 +330007 + int ADD 0001 +10008 > int LE 0007 +100000009 ------ LOOP ------------0010 num ADD 0006 +110011 int MOD 0007 +100012 > int NE 0011 +00013 + num ADD 0010 +330014 + int ADD 0007 +10015 > int LE 0014 +100000016 int PHI 0007 00140017 num PHI 0006 0013---- TRACE 1 stop -> loop---- TRACE 2 start 1/4 Ex.lua:8---- TRACE 2 IR0001 num SLOAD #1 PI0002 int SLOAD #2 PI0003 num ADD 0001 +220004 num ADD 0003 +330005 int ADD 0002 +10006 > int LE 0005 +100000007 num CONV 0005 num.int---- TRACE 2 stop -> 1

Extensions

LuaJIT adds several extensions to its base implementation, Lua 5.1, most of which do not break compatibility. [18]

DynASM

DynASM
Developer(s) Mike Pall
Repository
Written in Lua, C [23]
Platform x86, X86-64, PowerPC, ARM, MIPS
Type Preprocessor, Linker
License MIT License [3]
Website luajit.org/dynasm.html

DynASM is a lightweight preprocessor for C that provides its own flavor of inline assembler, independent of the C compiler. DynASM replaces assembly code in C files with runtime writes to a 'code buffer', such that a developer may generate and then evoke code at runtime from a C program. It was created for LuaJIT 1.0.0 to make developing the just-in-time compiler easier.[ citation needed ]

DynASM includes a bare-bones C header file which is used at compile time for logic the preprocessor generates. The actual preprocessor is written in Lua.

References

  1. ↑ LuaJIT tags
  2. ↑ "LuaJIT". LuaJIT. Retrieved 25 February 2022.
  3. 1 2 "LuaJIT/COPYRIGHT at v2.1 · LuaJIT/LuaJIT". GitHub . 7 January 2022.
  4. ↑ "The LuaJIT Project". luajit.org. Retrieved 2023-06-17.
  5. ↑ Pall, Mike. "Re: [ANN] llvm-lua 1.0". lua-users.org. Retrieved 25 February 2022.
  6. ↑ "Project status - Issue #665 - LuaJIT/LuaJIT". GitHub. Retrieved 3 February 2023.
  7. ↑ "[ANN] Looking for new LuaJIT maintainers - luajit - FreeLists". www.freelists.org. Retrieved 2023-03-29.
  8. ↑ Deniau, Laurent. "Lua(Jit) for computing accelerator beam physics". CERN Document Server. CERN. Retrieved 25 February 2022.
  9. ↑ "OpenResty® - Official Site". openresty.org.
  10. ↑ "Lua - Neovim docs". neovim.io. Retrieved 2024-05-07.
  11. ↑ "Kong/kong". GitHub. Kong. 25 February 2022. Retrieved 25 February 2022.
  12. ↑ "Helping to make Luajit faster". blog.cloudflare.com. 19 October 2017. Retrieved 25 February 2022.
  13. ↑ "LuaJIT Performance".
  14. ↑ "Laurence Tratt: The Impact of Meta-Tracing on VM Design and Implementation". tratt.net. Retrieved 2 March 2022.
  15. 1 2 d'Andrea, Laurent (2019). Behavioural Analysis of Tracing JIT Compiler Embedded in the Methodical Accelerator Design Software (Thesis). CERN. Retrieved 31 July 2022.
  16. ↑ Pall, Mike. "Tuning numerical computations for LuaJIT (was Re: [ANN] Sci-1.0-beta1) - luajit - FreeLists". www.freelists.org.
  17. ↑ Rottenkolber, Max. "Later Binding: Just-in-Time Compilation of a Younger Dynamic Programming Language." ELS. 2020
  18. ↑ "Extensions". LuaJIT. Retrieved 25 February 2022.
  19. ↑ "BitOp Semantics". LuaJIT. Retrieved 25 February 2022.
  20. ↑ "Coco - True C Coroutines". LuaJIT. Retrieved 25 February 2022.
  21. ↑ "FFI Library". LuaJIT. Retrieved 25 February 2022.
  22. ↑ "Extensions". luajit.org. Retrieved 2022-08-25.
  23. ↑ "DynASM Features". DynASM. Retrieved 25 February 2022.
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