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New semantics for the integer 'for' loop

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The numerical 'for' loop over integers now uses a precomputed counter
to control its number of iteractions. This change eliminates several
weird cases caused by overflows (wrap-around) in the control variable.
(It also ensures that every integer loop halts.)

Also, the special opcodes for the usual case of step==1 were removed.
(The new code is already somewhat complex for the usual case,
but efficient.)
This commit is contained in:
Roberto Ierusalimschy
2019-03-19 10:53:18 -03:00
parent 1e0c73d5b6
commit 9b37a4695e
10 changed files with 213 additions and 185 deletions
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2
lopcodes.c
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@@ -93,8 +93,6 @@ LUAI_DDEF const lu_byte luaP_opmodes[NUM_OPCODES] = {
,opmode(0, 1, 0, 0, iABC) /* OP_RETURN */
,opmode(0, 0, 0, 0, iABC) /* OP_RETURN0 */
,opmode(0, 0, 0, 0, iABC) /* OP_RETURN1 */
,opmode(0, 0, 0, 1, iABx) /* OP_FORLOOP1 */
,opmode(0, 0, 0, 1, iABx) /* OP_FORPREP1 */
,opmode(0, 0, 0, 1, iABx) /* OP_FORLOOP */
,opmode(0, 0, 0, 1, iABx) /* OP_FORPREP */
,opmode(0, 0, 0, 0, iABx) /* OP_TFORPREP */