Re: Sparse 0.5.1 RC5 released.

[Luc Van Oostenryck <luc.vanoostenryck@gmail.com>]

> OTOH with -rc4, it takes only 0.05s !
>
> The situation is really weird, it's an interaction between the patches:
> - remove single-store shortcut (first slowdown to 0.8s)
> - fix ptrlist corruption while killing unreachable BBs (second slowdown to 2.9s)
> - mark pseudo users as deleted instead of removing them (third slowdown to 5.5s)
>
> All three patches were expected to create *some* slowdown,
> the first one very obviously and much more than the others.
>
> It's interesting to note that without the 'remove single shortcut' patch, the
> two others ones don't seem to have a significative effect on the time.
>
> My guess here is that indeed, with this input, the single-store shortcut
> is a huge optimization and without it much much more code is created
> (phi-nodes, I suppose) and this impact very negatively the two other fixes.
>
> I'll see what can be done.

It's also interesting to note that with the new SSA construction, there is no
slowdown (0.064s here but too small to be measured accurately).
This confirms me that the single-store shortcut was very much needed for
performance (not simply because it's faster than the general case but that
it creates much less intermediate code) but it created bad code ...

-- Luc