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Revert "op_scope/newCONDOP: Optimise away empty else blocks in OP_COND_EXPR #22870

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Dec 20, 2024
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Revert "op_scope/newCONDOP: Optimise away empty else blocks in OP_COND_EXPR #22870

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23 changes: 7 additions & 16 deletions lib/B/Deparse.pm
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Original file line number Diff line number Diff line change
Expand Up @@ -3966,22 +3966,13 @@ sub pp_cond_expr {
my $true = $cond->sibling;
my $false = $true->sibling;
my $cuddle = $self->{'cuddle'};

if (class($false) eq "NULL") { # Empty else {} block was optimised away
unless ($cx < 1 and (is_scope($true) and $true->name ne "null")) {
$cond = $self->deparse($cond, 8);
$true = $self->deparse($true, 6);
return $self->maybe_parens("$cond ? $true : ()", $cx, 8);
}
} else { # Both true and false branches are present
unless ($cx < 1 and (is_scope($true) and $true->name ne "null")
and (is_scope($false) || is_ifelse_cont($false))
and $self->{'expand'} < 7) {
$cond = $self->deparse($cond, 8);
$true = $self->deparse($true, 6);
$false = $self->deparse($false, 8);
return $self->maybe_parens("$cond ? $true : $false", $cx, 8);
}
unless ($cx < 1 and (is_scope($true) and $true->name ne "null") and
(is_scope($false) || is_ifelse_cont($false))
and $self->{'expand'} < 7) {
$cond = $self->deparse($cond, 8);
$true = $self->deparse($true, 6);
$false = $self->deparse($false, 8);
return $self->maybe_parens("$cond ? $true : $false", $cx, 8);
}

$cond = $self->deparse($cond, 1);
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4 changes: 0 additions & 4 deletions lib/B/Deparse.t
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Expand Up @@ -3378,7 +3378,3 @@ $_ = (!$p) isa 'Some::Class';
$_ = (!$p) =~ tr/1//;
$_ = (!$p) =~ /1/;
$_ = (!$p) =~ s/1//r;
####
# Else block of a ternary is optimised away
my $x;
my(@y) = $x ? [1, 2] : ();
23 changes: 4 additions & 19 deletions op.c
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Expand Up @@ -4517,12 +4517,6 @@ Perl_op_scope(pTHX_ OP *o)
{
if (o) {
if (o->op_flags & OPf_PARENS || PERLDB_NOOPT || TAINTING_get) {

/* There's no need to wrap an empty stub in an enter/leave.
* This also makes eliding empty if/else blocks simpler. */
if (OP_TYPE_IS(o, OP_STUB) && (o->op_flags & OPf_PARENS))
return o;

o = op_prepend_elem(OP_LINESEQ,
newOP(OP_ENTER, (o->op_flags & OPf_WANT)), o);
OpTYPE_set(o, OP_LEAVE);
Expand Down Expand Up @@ -9274,6 +9268,7 @@ Perl_newCONDOP(pTHX_ I32 flags, OP *first, OP *trueop, OP *falseop)
logop = alloc_LOGOP(OP_COND_EXPR, first, LINKLIST(trueop));
logop->op_flags |= (U8)flags;
logop->op_private = (U8)(1 | (flags >> 8));
logop->op_next = LINKLIST(falseop);

CHECKOP(OP_COND_EXPR, /* that's logop->op_type */
logop);
Expand All @@ -9282,23 +9277,13 @@ Perl_newCONDOP(pTHX_ I32 flags, OP *first, OP *trueop, OP *falseop)
start = LINKLIST(first);
first->op_next = (OP*)logop;

/* make first & trueop siblings */
/* falseop may also be a sibling, if not optimised away */
/* make first, trueop, falseop siblings */
op_sibling_splice((OP*)logop, first, 0, trueop);
op_sibling_splice((OP*)logop, trueop, 0, falseop);

o = newUNOP(OP_NULL, 0, (OP*)logop);

if (OP_TYPE_IS(falseop, OP_STUB) && (falseop->op_flags & OPf_PARENS)) {
/* The `else` block is empty. Optimise it away. */
logop->op_next = o;
op_free(falseop);
} else {
op_sibling_splice((OP*)logop, trueop, 0, falseop);
logop->op_next = LINKLIST(falseop);
falseop->op_next = o;
}

trueop->op_next = o;
trueop->op_next = falseop->op_next = o;

o->op_next = start;
return o;
Expand Down
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