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Re: RFC: merging MEM_ATTRS
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: joern dot rennecke at superh dot com
- Cc: gcc at gcc dot gnu dot org
- Date: Tue, 10 Feb 04 13:29:26 EST
- Subject: Re: RFC: merging MEM_ATTRS
> I think that it's simpler just to use zero: the information isn't
> that useful by then.
It isn't that useful to enable more optimizations, but necessary to avoid
incorrect ones, as discussede here:
http://gcc.gnu.org/ml/gcc-patches/2004-01/msg03234.html
I don't see the discussion from there, but certainly something is
wrong: zeroing a field like MEM_EXPR means you don't know anything, so
I don't see how doing do can produce an incorrect optimization.
If we zero the MEM_EXPR if one or more of the alternatives accesses a
variable that never has its address taken and that we reasoned thus
can only be accessed with explicit accesses, we would incorrectly
assume the MEM can't affect/use the variable any more.
I don't follow.