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Peephole optimizations for NULLs in lists and scalar lists #23523

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Peephole optimizations for NULLs in lists and scalar lists #23523

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e95ec34
peep.c: remove childless OP_NULL nodes in a list
richardleach Jul 31, 2025
3a09ea4
peep.c: optimise OP_LIST in scalar context
richardleach Jul 31, 2025
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37 changes: 37 additions & 0 deletions peep.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3124,6 +3124,43 @@ Perl_rpeep(pTHX_ OP *o)

case OP_PUSHMARK:

/* Given
pushmark
null
something_else
Take out the null wherever possible.
*/
while (OP_TYPE_IS(o->op_next, OP_NULL)) {
OP* next = o->op_next;
o->op_next = next->op_next;
if (OpSIBLING(o) == next &&
next->op_moresib &&
!(next->op_flags & OPf_KIDS)) {
op_sibling_splice(NULL, o, 1, NULL);
op_free(next);
}
}

/* Given
list (in scalar context)
pushmark
something
The pushmark & list OPs are unnecessary.
*/

{
OP *nn = o->op_next->op_next;
if (OP_TYPE_IS(nn, OP_LIST) &&
((nn->op_flags & OPf_WANT) == OPf_WANT_SCALAR) ) {
if (oldop)
oldop->op_next = o->op_next;
o->op_next->op_next = nn->op_next;
op_null(nn);
op_null(o);
oldop = NULL; oldoldop = NULL;
}
}

/* Given
5 repeat/DOLIST
3 ex-list
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