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Re: [patch] Enable -fweb and -frename-registers when unrolling



I hope one day these flags might be enabled by default always, but this
does not seem to be feasible at the moment due to compile time issues.

For -fweb, actually, it was not compile-time issues but performance issues. The benefit was subsumed by out-of-SSA live range splitting. Steven Bosscher disabled it.


Rename registers instead is really slow (8% of compile time). And look out for target bugs caused by rename registers.

However, they are most useful when loops are unrolled, and with
-funroll-loops, the compile time is not that much of a problem, so
perhaps it could be enabled at least then?

You are missing the documentation patch (before somebody else says it!).


-fweb makes debugging impossible, you may want to enable it only if variable tracking is working on the target (there's already code to do so, grep for default_debug_hooks).

Paolo


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