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Re: RFC: GC allocating everything with a type, part 1

Would it not be appropriate to have separate type codes for every rtx
and tree code?

There are a few problems with doing that i can think of off the top of my head that pretty much make it infeasible.

1. gengtype doesn't generate type codes like that, so we'd have to make up a hackish way to include them in the gtype file by puttering around in tree.def
2. This would require, among other things, large numbers of modifications all over the place (because everything that uses ggc_alloc_tree/rtx, including things that use it for a variety of tree/rtl codes, would have to have some large switch.

3. The only thing that these extra typecodes buy you is the ability to segregate different types of trees into different places. Most trees that are allocated around the same time should be close together in memory, even if they are of different sizes.
That's why i moved trees into the tree zone, rather than trying to further split up the tree zone.

4. The only immediate advantage to type coding everything to be able to determine what marker routine to call on a given chunk of memory (if we stop and restart marking, for example). You just need that code i had discussed with you once that generates an array mapping typecodes to marker routines (remember when i was trying to figure out an easy way to make sure the marking routines that only existed in some languages didn't get pulled into the common gtype-desc.h file, where the arrays were going to be?)

In this light, the tree marker knows how to mark all types of trees, so we'd end up calling the same marking routine even if the type codes were different anyway.
 This suffices to dispose of many, although not all, of
the cases where the type doesn't determine the size.


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