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add padrange op
This single op can, in some circumstances, replace the sequence of a
pushmark followed by one or more padsv/padav/padhv ops, and possibly
a trailing 'list' op, but only where the targs of the pad ops form
a continuous range.
This is generally more efficient, but is particularly so in the case
of void-context my declarations, such as:
my ($a,@b);
Formerly this would be executed as the following set of ops:
pushmark pushes a new mark
padsv[$a] pushes $a, does a SAVEt_CLEARSV
padav[@b] pushes all the flattened elements (i.e. none) of @a,
does a SAVEt_CLEARSV
list pops the mark, and pops all stack elements except the last
nextstate pops the remaining stack element
It's now:
padrange[$a..@b] does two SAVEt_CLEARSV's
nextstate nothing needing doing to the stack
Note that in the case above, this commit changes user-visible behaviour in
pathological cases; in particular, it has always been possible to modify a
lexical var *before* the my is executed, using goto or closure tricks.
So in principle someone could tie an array, then could notice that FETCH
is no longer being called, e.g.
f();
my ($s, @a); # this no longer triggers two FETCHES
sub f {
tie @a, ...;
push @a, 1,2;
}
But I think we can live with that.
Note also that having a padrange operator will allow us shortly to have
a corresponding SAVEt_CLEARPADRANGE save type, that will replace multiple
individual SAVEt_CLEARSV's.
18 files changed: