The constants in function prototype could be string, number, boolean, and nil now. But some times we want to use a table as a constant object, like this:
-- iterate a immutable sequence :
for _, v in ipairs { "one", "two", "three" } do
or like this :
function f()
return { x=1, y = 2}
end
{ x=1, y=2 } may be a constant table. We don't modify it later.
If these kind of table constants can be hold in function prototype, it would be faster (maybe 3-4 times faster, see the test below) and cheaper. We only need create a table proxy hold a c pointer to the table constant in the prototype.
If we modify the table later, simply clone the constant to turn the table proxy into a real table first.
I have already try to do a quick and dirty implementation,
It add two opcode OP_NEWTABLEK and OP_NEWTABLEKX to support table constants. If table constructor in parser find all the keys and values of the table are constants , it add a constant table in prototype, and use new opcode .
btw, I haven't implement dump/undump now.
---- test 1 ---
function f(a)
end
local t = os.clock()
for i=1, 10000000 do
f { x=1, y=2 }
end
print(os.clock() -t)
-------------
Origin version of lua 5.3.2 : 4.977s
Modified version of lua 5.3.2: 1.278s
---- test 2 ---
function f(a)
a.x = 3
end
local t = os.clock()
for i=1, 10000000 do
f { x=1, y=2 }
end
print(os.clock() -t)
-------------
Origin version of lua 5.3.2 : 5.234s
Modified version of lua 5.3.2: 1.413s
