[LLVMdev] AliasAnalysis Documentation Ambiguity

Thomas B. Jablin tjablin at cs.princeton.edu
Fri Jun 11 10:12:30 PDT 2010

What do you think of this patch? I have added a check for the case I mentioned in the previous email as well as a similar situation I discovered later.

----- Original Message -----
From: "Dan Gohman" <gohman at apple.com>
To: "Thomas B. Jablin" <tjablin at CS.Princeton.EDU>
Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
Sent: Friday, June 11, 2010 12:22:03 PM GMT -05:00 US/Canada Eastern
Subject: Re: [LLVMdev] AliasAnalysis Documentation Ambiguity

On Jun 9, 2010, at 11:35 AM, "Thomas B. Jablin" <tjablin at cs.princeton.edu 
 > wrote:
> Should there be a check in BasicAliasAnalysis to ensure that O1 and  
> O2 belong to the same function, or should the documentation be  
> updated to indicate the limits of the alias method? Thanks.

I think there should be such a check.

A noalias Argument should still be NoAlias with Allocas in other  
functions, but a regular Argument should be MayAlias with them -- at  
least for the level of analysis that BasicAA does.

The noalias case is interesting though.  If you're doing extensive  
interprocedural analysis, it may be necessary to add a way to tell  
AliasAnalysis passes to completely ignore noalias.


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