Allocation optimizations

From: Antonio Nikishaev <a@xxxxxxx>
To: luajit@xxxxxxxxxxxxx
Date: Wed, 17 Sep 2014 20:02:22 +0400

Help me to understand causes for how things work.
luajit v2.1 HEAD


-----------------------------------------
local function qux (state)
   state.x = 1
   state.y = state.x
end


local function main1 ()         -- gc
   local state = {}
   qux (state)
end

local function main2 ()         -- no gc
   local state = { x=0 }
   qux (state)
end

local function main3 ()         -- gc
   local state = { }
   state.x = 0
   qux (state)
end

local function main4 ()         -- gc
   local state = { x=0, z={} }
   qux (state)
end




local function quux (state)
   state.z = {}
end


local function main5 ()         -- gc
   local state = {}
   quux (state)
end


for i = 1, 1e7 do
   main1()
end
----------------------------------------- code end



1) Are there any particular reasons for this behaviour I don't see?
2) I'm very interested in the main5 case. Any way to do it gc-free?



-- 
lelf

Follow-Ups:
- Re: Allocation optimizations
  - From: Mike Pall

Allocation optimizations

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