[PCH] constant pools rewrite

[Richard Henderson]

On Mon, Feb 18, 2002 at 09:09:57AM -0800, Geoffrey Keating wrote:
> Some future work, which I don't have time for right now but which
> might be interesting for someone in the future:

Given that you poked at this at all, I think it is a mistake
that you didn't simply rip out all of the rtx_const nonsense.
This is left over from when we had per-function obstacks, and
should be irrelevant with GC.

> - Work out why the RTX constant pool is per-function, when the tree
>   constant pool is per-file.  If (as I suspect) there's no real
>   reason, make the RTX constant pool per-file.  Delete the code in the
>   rs6000 backend that creates its own per-file RTX constant pool.

Because some ports ...

> - Work out why the ARM backend has its own constant pool handling, and
>   merge that functionality back into the middle-end.  I'm sure lots of
>   ports could benefit from it.

... require constant pools *within* the function, so that 
they can address them with 8-bit pc-relative relocs.

See arm, mcore, sh, s390 to name a few.

But for everyone else, we should indeed be using per-file pools.


r~