In lua, some operators and statements are optimized out when acting on literals
{1}, while others are not {2}. I tryed both with lua-5.3 and lua5.4-beta.
Given the constant propagation in the new lua, I think that some effort on this
kind of optimization could be worth. Or is it too complex?
pocomane
{1} Example of optimized code:
a)
return true and true
0+ params, 2 slots, 1 upvalue, 0 locals, 0 constants, 0 functions
1 [1] VARARGPREP 0
2 [1] LOADBOOL 0 1 0
3 [1] RETURN 0 2 1 ; 1 out
4 [1] RETURN 0 1 1 ; 0 out
b)
return 1 + 1
0+ params, 2 slots, 1 upvalue, 0 locals, 0 constants, 0 functions
1 [1] VARARGPREP 0
2 [1] LOADI 0 2
3 [1] RETURN 0 2 1 ; 1 out
4 [1] RETURN 0 1 1 ; 0 out
c)
if 1 then return 1 end
0+ params, 2 slots, 1 upvalue, 0 locals, 0 constants, 0 functions
1 [1] VARARGPREP 0
2 [1] LOADI 0 1
3 [1] RETURN 0 2 1 ; 1 out
4 [1] RETURN 0 1 1 ; 0 out
{2} Example of not-optimized code:
d)
return true == true
0+ params, 2 slots, 1 upvalue, 0 locals, 1 constant, 0 functions
1 [1] VARARGPREP 0
2 [1] LOADBOOL 0 1 0
3 [1] EQK 0 0 1 ; true
4 [1] JMP 1 ; to 6
5 [1] LOADBOOL 0 0 1 ; to 6
6 [1] LOADBOOL 0 1 0
7 [1] RETURN 0 2 1 ; 1 out
8 [1] RETURN 0 1 1 ; 0 out
e)
if 1 then return 1 elseif 1 then return 2 end
0+ params, 2 slots, 1 upvalue, 0 locals, 0 constants, 0 functions
1 [1] VARARGPREP 0
2 [1] LOADI 0 1
3 [1] RETURN 0 2 1 ; 1 out
4 [1] JMP 2 ; to 7
5 [1] LOADI 0 2
6 [1] RETURN 0 2 1 ; 1 out
7 [1] RETURN 0 1 1 ; 0 out
(Actually this is optimized too, it is just emitted some junk code)
