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Re: [tcb] Incremental SSA updates

Zdenek Dvorak wrote:

I did not try to measure.  But if the patch is really used in an
incremental fashion, scanning long basic blocks most definitely is not

You need numbers to back that up. We do very many IL scans in the course of the optimizers. I've never seen IL scans too high in the list.

No it is not; update_ssa features for example
rewrite_blocks (start_bb, REWRITE_UPDATE);

Certainly, but blocks that have no uses nor defs of affected names are ignored (local patch for now). So, it doesn't really matter.

It is supposed to be used for example during updates of loop closed ssa
form, where you know that only some of the uses are affected.


Your approach scans whole subgraph dominated by start_bb, which
may be significantly more than necessary area.  In the use in vrp,
it will usually be almost whole program.

Not at all, only the affected blocks and in those affected blocks, the affected statements are scanned.

In any case, give me a couple of days to do some timings and take a good look at your patch. I still haven't had the time to examine it closely.


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