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Re: [tree-ssa] Eliminating unnecessary variables during out-of-ssa
- From: Daniel Berlin <dberlin at dberlin dot org>
- To: Andrew MacLeod <amacleod at redhat dot com>
- Cc: gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Mon, 12 May 2003 14:43:06 -0400
- Subject: Re: [tree-ssa] Eliminating unnecessary variables during out-of-ssa
Currently, I dont think we need anything that has a derefernced
variable
as a PHI_RESULT.
For SSAPRE store movement and load movement, I need it.
In particular, i need the vdefs for load movement, and the uses/phi
results for store movement.
Otherwise, i can't tell when a load is possibly killed without
calculating the exact same info (in the case of vdefs), or the possible
insertion points for the store (that's what the PHI's give us).
There are other optimizations i'm working on (loop related) that need
this info, too.
Just because our basic opts don't need it, doesn't mean you should
remove it.
Can't you just ignore it in out-of-ssa, rather than remove it
altogether?
--Dan