sort {$b cmp $a} and the peephole optimiser
Where does the op for cmp go in this?
$ perl -MO=Concise -e '@a = sort {$b cmp $a} @b'
I see:
c @ leave[1 ref] vKP/REFC -(end)
1 0 enter -2
2 ; nextstate(main 2 -e:1) v -3
b 2 aassign[t2] vKS -c
-1 ex-list lK -8
3 0 pushmark s -4
7 @ sort lK/DESC -8
4 0 pushmark s -5
6 1 rv2av[t3] lK/1 -7
5 $ gv(*b) s -6
-1 ex-list lK -b
8 0 pushmark s -9
a 1 rv2av[t1] lKRM*/1 -b
9 $ gv(*a) s -a
I expected to see an ex-scmp in there. Is the cmp ever compiled to ops?
Nicholas Clark
'
Re: sort {$b cmp $a} and the peephole optimiser
Nicholas Clark wrote:
Where does the op for cmp go in this?
$ perl -MO=Concise -e '@a = sort {$b cmp $a} @b'
I see:
c @ leave[1 ref] vKP/REFC -(end)
1 0 enter -2
2 ; nextstate(main 2 -e:1) v -3
b 2 aassign[t2] vKS -c
-1 ex-list lK -8
3 0 pushmark s -4
7 @ sort lK/DESC -8
4 0 pushmark s -5
6 1 rv2av[t3] lK/1 -7
5 $ gv(*b) s -6
-1 ex-list lK -b
8 0 pushmark s -9
a 1 rv2av[t1] lKRM*/1 -b
9 $ gv(*a) s -a
I expected to see an ex-scmp in there. Is the cmp ever compiled to ops?
yes, but it's freed in S_simplify_sort, called by ck_sort during optree
construction, i.e. before the peephole optimizer is called.
Concise shows the DESC flag on the sort op that indicates this is a reverse
sort.
Re: sort {$b cmp $a} and the peephole optimiser
On Thu, Sep 01, 2005 at 10:59:52AM +0200, Rafael Garcia-Suarez wrote: Nicholas Clark wrote: I expected to see an ex-scmp in there. Is the cmp ever compiled to ops? yes, but it's freed in S_simplify_sort, called by ck_sort during optree construction, i.e. before the peephole optimizer is called. Aha. This was what I was wondering, and also why the departure from perl's usual policy of not free-ing ops during optimisation. Concise shows the DESC flag on the sort op that indicates this is a reverse sort. and there are also NUM and now REVERSE (IIRC) Nicholas Clark
