When is an opcode's ->seq empty?

diotalevi has asked for the wisdom of the Perl Monks concerning the following question:

In B::Utils::parent I read that Simon is not sure how to find the parent of nodes where ->seq is false. When does this happen?

sub B::OP::parent {
    my $target = shift;
    die "I'm not sure how to do this yet. I'm sure there is a way. If 
+you know, please email me."
        if (!$target->seq);
    ...
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Re: When is an opcode's ->seq empty? by diotalevi (Canon) on Jun 14, 2004 at 20:53 UTC
Some source code reading revealed the answer. I thought that this was a deeper thing than it is. op_seq is zero before the peep-hole optimizer runs on some code and non-zero afterwards as a flag to prevent the optimizer from running again. I now wonder how Simon got a handle to some code before the optimizer took hold of it. Hmm...	[reply]

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