Re: Metatable check helper API proposal

[云风 Cloud Wu <cloudwu@...>]

云风 Cloud Wu <cloudwu@gmail.com> 于2020年8月20日周四 上午10:57写道：

> ```lua
> local N = 100000000
>
> local a = {}
> local meta = {} ; meta.__index = meta
>
> function meta:foo()
> end
>
> setmetatable(a, meta)
>
> local t = os.clock()
>
> for i = 1, N do
>   local foo = a.foo
> end
>
> local t1 = os.clock()
>
> for i = 1, N do
>   local foo = a:foo()
> end
>
> local t2 = os.clock()
>
> print(t1 - t, t2 - t1)
> ```
>
> Intel i7-7700 @ 3.60GHz Windows 10 mingw64 gcc 8.2.0
>
> lua 5.4 (https://github.com/lua/lua master) 1.524   2.887
> After patch (See attachment):                     1.271   2.492

I added the empty loop test.

local N = 100000000

local a = {}
local meta = {} ; meta.__index = meta

function meta:foo()
end

setmetatable(a, meta)

local t = os.clock()

for i = 1, N do
  local foo = a.foo
end

local t1 = os.clock()

for i = 1, N do
  local foo = a:foo()
end

local t2 = os.clock()

for i = 1, N do
  local foo = a
end

local t3 = os.clock()

print(t1 - t, t2 - t1, t3 - t2)
```

Intel i7-7700 @ 3.60GHz Windows 10 mingw64 gcc 8.2.0

lua 5.4                         1.551   2.807   0.378
After patch                   1.259   2.593   0.378

(1.551-0.378) / (1.259-0.378) = 1.331

I think it's 33% faster.

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