Q_rsqrt - Fast inverse square root ported to luau

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#1

This is a proof-of-concept code that shows how to make C-like bitwise manipulations using only native luau features. Despite the name, it is actually slower and less precise than if you were to use 1/math.sqrt(). So don’t use it seriously.

--!strict
--!native

local evil = buffer.create(4)

local function Q_rsqrt(number:number) : number
	local x2:number = number * 0.5
	buffer.writef32(evil,0,number)	-- evil floating point bit manipulation
	buffer.writei32(evil,0,0x5f3759df - bit32.rshift(buffer.readi32(evil,0),1)) -- what the ####?
	local y:number  = buffer.readf32(evil,0)
	y  = y * ( 1.5 - ( x2 * y * y ) ) -- 1st iteration
	--y  = y * ( 1.5 - ( x2 * y * y ) )	-- 2nd iteration, this can be removed
	return y
end

This also retains the original comments. I would like to hear what you think of it.

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