openresty/luajit2 - OpenResty's LuaJIT branch

• Name
• Description
  • New API
    • table.isempty
    • table.isarray
    • table.nkeys
    • thread.exdata
    • table.clone
    • jit.prngstate
  • New JIT parameter defaults
  • String table hashing optimization
  • New command-line option -bL
  • More detailed LuaJIT bytecode textual listing
  • New macros
  • Miscellaneous
• Copyright & License

This is the official OpenResty branch for LuaJIT. This is not really a fork since we still synchronize any upstream changes all the time.

We introduce our own changes which will never merge or haven't yet merged into the upstream LuaJIT (https://github.com/LuaJIT/LuaJIT), which are as follows

We added the table.isempty() builtin Lua API.

This Lua API can be JIT compiled.

Returns true when the table contains non-nil array elements or non-nil key-value pairs.

Usage:

local isempty = require "table.isempty"
print(isempty({}))  -- true
print(isempty({nil, dog = nil}))  -- true
print(isempty({"a", "b"}))  -- false
print(isempty({nil, 3}))  -- false
print(isempty({cat = 3}))  -- false

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We implemented the new table.isarray() builtin function which returns true for purely array-like Lua tables and false otherwise.

Empty Lua tables are treated as arrays.

Use it like this:

isarr = require "table.isarray"
print(isarr{"a", true, 3.14})  -- true
print(isarr{"dog" = 3})  -- false
print(isarr{})  -- true

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We added the new table.nkeys Lua API.

This Lua builtin returns the number of elements in a Lua table, i.e., the number of non-nil array elements plus the number of non-nil key-value pairs in a single Lua table.

It can be used like this:

local nkeys = require "table.nkeys"

print(nkeys({}))  -- 0
print(nkeys({ "a", nil, "b" }))  -- 2
print(nkeys({ dog = 3, cat = 4, bird = nil }))  -- 2
print(nkeys({ "a", dog = 3, cat = 4 }))  -- 3

This Lua API can be JIT compiled.

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We implemented the new Lua and C API functions for thread exdata.

The Lua API can be used like below:

local exdata = require "thread.exdata"
exdata(0xdeadbeefLL)  -- set the exdata of the current Lua thread
local ptr = exdata()  -- fetch the exdata of the current Lua thread

The exdata value on the Lua land is represented as a cdata object of the ctype void*.

Right now the reading API, i.e., exdata() calls without any arguments, can be JIT compiled.

Also exposed the following public C API functions for manipulating exdata on the C land:

void lua_setexdata(lua_State *L, void *exdata);
void *lua_getexdata(lua_State *L);

The exdata pointer is initialized to NULL when the main thread is created. Any child Lua threads created will inherit the parent's exdata but still have their own exdata storage. So child Lua threads can always override the inherited parent exdata pointer values.

This API is used internally by the OpenResty core so never ever mess with it yourself in the context of OpenResty.

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We implemented the table.clone() builtin Lua API.

This change only support shallow clone. e.g

local tab_clone = require "table.clone"
local x = {x=12, y={5, 6, 7}}
local y = tab_clone(x)
... use y ...

Deep clone will be supported by adding 'true' as the 2nd argument to table.clone

We observe 7% over-all speedup in the edgelang-fan compiler's compiling speed whose Lua is generated by the fanlang compiler.

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We implemented new API function jit.prngstate() for reading or setting the current PRNG state number used in the JIT compiler.

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We use more appressive JIT compiler parameters as the default to help large OpenResty Lua apps.

We now use the following jit.opt defaults:

maxtrace=8000
maxrecord=16000
minstitch=3
maxmcode=40960  -- in KB

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The lj_str_new() primitiven now uses randomized hash functions based on crc32 when -msse4.2 is specified for Intel CPUs supporting SSE 4.2 instruction set.

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We added the bytecode option L to display lua source line numbers. For example, luajit -bL -e 'print(1)' now produces bytecode dump like below:

-- BYTECODE -- "print(1)":0-1
0001     [1]    GGET     0   0      ; "print"
0002     [1]    KSHORT   1   1
0003     [1]    CALL     0   1   2
0004     [1]    RET0     0   1

The column [N] is the Lua source line number. For example, [1] means on the first source line.

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The -bl option also prints out the constant tables of each Lua prototype. For example,

-- BYTECODE -- a.lua:0-48
KGC    0    "print"
KGC    1    "hi"
KGC    2    table
KGC    3    a.lua:17
KN    1    1000000
KN    2    1.390671161567e-309
...

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In the header file luajit.h, we defined the macro OPENRESTY_LUAJIT for our branch of LuaJIT.

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• various important fixes for bugs in the JIT compiler and the VM which have not been merged in upstream LuaJIT.
• removed the GCC 4 requirement for x86 for older systems like Solaris i386.
• In the Makefile file, make sure we always install the symlink for "luajit" even for alpha or beta versions.
• feature: jit.dump: output Lua source location after every BC.
• feature: added internal memory-buffer-based trace entry/exit/start-recording event logging, mainly for debugging bugs in the JIT compiler. it requires -DLUA_USE_TRACE_LOGS when building LuaJIT.
• feature: save g->jit_base to g->saved_jit_base before lj_err_throw clears g->jit_base which makes it impossible to get Lua backtrace in such states.
• applied a patch to fix DragonFlyBSD compatibility. Note: this is not an officially supported target.
• turned off string comparison optimizations for 64-bit architectures when the build option LUAJIT_USE_VALGRIND is specified. now LuaJIT is (almost) valgrind clean.

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LuaJIT is a Just-In-Time (JIT) compiler for the Lua programming language.

Project Homepage: http://luajit.org/

LuaJIT is Copyright (C) 2005-2019 Mike Pall.

Additional patches for OpenResty are copyrighted by Yichun Zhang and OpenResty Inc.:

Copyright (C) 2017-2019 Yichun Zhang. All rights reserved.

Copyright (C) 2017-2019 OpenResty Inc. All rights reserved.

LuaJIT is free software, released under the MIT license. See full Copyright Notice in the COPYRIGHT file or in luajit.h.

Documentation for the official LuaJIT is available in HTML format. Please point your favorite browser to:

doc/luajit.html

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