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Re: RFC - Alternatives to gengtype
On Sun, Nov 25, 2012 at 4:21 PM, Diego Novillo <dnovillo@google.com> wrote:
> On Sun, Nov 25, 2012 at 10:09 AM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>
>> I'd say the most pragmatic solution is to stick with gengtype but
>> make it more dependent on annotations (thus, explicit). That is,
>
> Yes. That is the direction in which I've been leaning towards. My
> preference is to transitionally move to manual markers
> (http://gcc.gnu.org/wiki/cxx-conversion/gc-alternatives#Do_GC_marking_manually)
> and over time transition to memory pool management.
Note that the most GCed thing is a 'tree' and the solution is not
to move trees to memory pools but to use less trees in the first place!
If trees were not GCed GIMPLE would not be I bet, and thus if GIMPLE
would not refer to trees there would be no reason to GC it!
Improving things wrt tree usage also means to isolate C/C++ frontend
IL from the middle-end. I once proposed to cp tree.[ch] and at gimplification
time re-allocate and copy from the frontend tree "kind" to the gimple
tree "kind".
Of course our FE / middle-end separation enemy (debug info) makes this not
so viable at the moment.
>> I suppose I agree that garbage collection is not technically
>> required for writing a compiler, but getting rid of GC in GCC
>> entirely will be a hard and error-prone task (even if you
>> factor out PCH which is an entirely different mess).
>
> Agreed. As far as PCH is concerned, my preferred long term approach
> is to move to streamable types. We have an almost working
> implementation in the PPH branch and we already have a streaming
> framework in LTO.
Of course that's not all we preserve in PCH ... (look for "interesting" global
data marked as GC root just for the sake of PCH).
Richard.
>
> Diego.