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Re: RFC: merging MEM_ATTRS
- From: Joern Rennecke <joern dot rennecke at superh dot com>
- To: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Cc: joern dot rennecke at superh dot com, gcc at gcc dot gnu dot org
- Date: Tue, 10 Feb 2004 20:06:08 +0000 (GMT)
- Subject: Re: RFC: merging MEM_ATTRS
> But that soon leads to a combinatorial explosion when you have thirty
> such variables... most of the time, you'll want the set that contains
> none of these variables, sometimes you'll want to include one or more
> likely two of them, but conceptually we could have many of them.
>
> No, that's not what I meant: I meant one alias set for all.
For all what exactly? One alias set to include all variables that didn't
have their address taken is not useful; most of these accesses are
already described exactly by their MEM_EXPRs.
Do you mean one alias set that excludes all of them, to be used for
indirect references? We could use that, i.e. a MEM with a MEM_EXPR for
something that hasn't its address taken can't alias a MEM with that
alias set.
We couldn't express a merge of this alias set with just one single variable,
though, so we'd loose a bit more information when we do such a merge
than with a solution that is based solely on MEM_EXPRs.