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Another way to compile goto's

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The compilation of a goto or a label just create an entry and generate
boilerplate code for the gotos. As we don't know yet whether it needs a
CLOSE, we code a jump followed by a CLOSE, which is then dead code.

When a block ends (and then we know for sure whether there are variables
that need to be closed), we check the goto's against the labels of that
block. When closing a goto against a label, if it needs a CLOSE, the
compiler swaps the order of the jump and the CLOSE, making the CLOSE
active.
This commit is contained in:
Roberto Ierusalimschy 2025-01-10 13:54:51 -03:00
parent 8a3a49250c
commit 7ca3c40b50
6 changed files with 120 additions and 122 deletions
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13
testes/code.lua
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@ -412,13 +412,22 @@ checkequal(function (l) local a; return 0 <= a and a <= l end,
function (l) local a; return not (not(a >= 0) or not(a <= l)) end)
-- if-break optimizations
check(function (a, b)
while a do
if b then break else a = a + 1 end
end
end,
'TEST', 'JMP', 'TEST', 'JMP', 'ADDI', 'MMBINI', 'JMP', 'RETURN0')
'TEST', 'JMP', 'TEST', 'JMP', 'JMP', 'CLOSE', 'JMP', 'ADDI', 'MMBINI', 'JMP', 'RETURN0')
check(function ()
do
goto exit -- don't need to close
local x <close> = nil
goto exit -- must close
end
::exit::
end, 'JMP', 'CLOSE', 'LOADNIL', 'TBC',
'CLOSE', 'JMP', 'CLOSE', 'RETURN')
checkequal(function () return 6 or true or nil end,
function () return k6 or kTrue or kNil end)