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Re: [tree-ssa]: Reduce size of phi nodes by 31 bits
- From: law at redhat dot com
- To: Daniel Berlin <dberlin at dberlin dot org>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, Diego Novillo <dnovillo at redhat dot com>
- Date: Mon, 05 Jan 2004 23:35:50 -0700
- Subject: Re: [tree-ssa]: Reduce size of phi nodes by 31 bits
- Reply-to: law at redhat dot com
In message <CA51D1BD-3A5C-11D8-8825-000A95DA505C@dberlin.org>, Daniel Berlin wr
ites:
>We only ever set rewritten to be 1 or 0.
>I noticed this when someone else asked me about phi nodes and i had to
>lookup the structure.
>
>Bootstrapped and regtested on i686
As Richard said, this isn't actually going to save any space.
Using a bit from tree_common would result in real savings. The only reason
I didn't do that was lazyness -- it's a royal pain to prove that a bit in
tree_common is free for any purpose these days....
One could presumably use one of the lang_flags since the PHI node itself
should only be seen by the tree-ssa bits which shouldn't care about the
lang_flags. I avoided that simply because I didn't like the idea of
stealing a flag explicitly mean for language front-ends to use outside
the language front-ends.
We could also steal a bit from num_args or capacity. It wouldn't be
terribly difficult to verify we never try to grow the PHI too big if we
steal bits from those fields.
jeff