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Re: Proposed major change to combine
- To: tege at swox dot com
- Subject: Re: Proposed major change to combine
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Date: Thu, 8 Mar 01 10:30:47 EST
- Cc: gcc at gcc dot gnu dot org
I think it would also be good to make combine use rtx_cost for
determining which rewrites to perform. By requiring each change to
decrease the rtx_cost, we could do things recursively without risk of
non-termination.
I don't think combine should do that. I think combine should continue
to always decrease the number of insns. CSE already does as you suggest
and if it had the same simplification routines available to it (which is
what my proposal was aimed at), it would have the effect you want.
The would open to allow define_split that generate more insns than
they "consume".
I'm sorry: why would that be useful? Can you give me an example?