[DomTree] Avoid duplicate hash lookups in runDFS() (NFCI) (#96460)

runDFS() currently performs three hash table lookups. One in the main
loop, one when checking whether a successor has already been visited and
another when adding parent and reverse children to the successor.

We can avoid the two additional lookups by making the parent number part
of the stack, and then making the parent / reverse children update part
of the main loop.

The main loop already has a check for already visited nodes, so we don't
have to check this in advance -- we can simply push the node to the
worklist and skip it later.

0 files changed, 0 insertions, 0 deletions