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Re: [RFC] type safe trees

Geoff Keating wrote:

On 24/06/2004, at 9:19 PM, Mark Mitchell wrote:

Geoff Keating wrote:

If you're using the current HEAD, you should know that there's a bad performance bug in which the GC settings are wrong when --disable-checking is in effect. If you're seeing GC happen when building combine.c in a bootstrap, you either forgot --disable-checking, you're seeing this bug, or you need to go buy more RAM (even my laptop, with 256Mb of RAM, doesn't GC while building combine.c with the computed --param ggc-min-heapsize=65536).

Would you please describe this bug in more detail? Do you know how to fix it?

Wasn't the above description sufficient?

I was looking for information like in what way the settings were wrong, or under what circumstances it manifests, or what change caused it. It wasn't clear to me whether you knew exactly what was going on (and were maybe even in the prcoess of fixing it) or whether you had just observed a mysterious problem.

The symptom is that the GC parameters are locked at 4k, even with --disable-checking.

Thanks for explaining.

No, I don't know how to fix it. I don't even know if it's really in FSF GCC, it may be a merge bug into our local tree.

OK; I'll hope for the latter. :-) Thanks for the heads-up.

Also, I understand what you're saying about CONST_DECLs living only in PCH memory which is never read -- but what about things like TREE_LISTs or VAR_DECLs that get built a lot even after the PCH has been read in as the remaining code is processed. Do you have any ideas about how profitable it might or might not be to shrink them? (We can get lots of these nodes as templates are instantiated and as code is processed.)

Also, on the identifier table issues you mention, I was actually thinking about how to reorganize that stuff today. We should avoid stepping on each other in that area. I think there are some data structure improvements we should make and also some ways in which we can seriously improve the case of entering/exiting class scopes, which happens a ton.

Mark Mitchell
CodeSourcery, LLC
(916) 791-8304

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