[LLVMdev] How can i differentiate pointer type int 32* from int 32** ? (original) (raw)

Shen Liu shl413 at lehigh.edu
Sat Jul 18 06:51:11 PDT 2015

Yes i agree, so for the data dependencies through pointers, i first use inter-procedure alias analysis to find the alias pointer sets, and set up dependency between those store/load instructions whose memory locations are aliases.

The reason I want to exactly know point-to level is, for a function with multi-level pointer as arguments, like func(int ***p), i hope to demonstrate the memory read/write process for each level on my graph, if necessary i will add some dummy nodes to represent the intermediate memory read/write.

Best regards,

Shen

On Fri, Jul 17, 2015 at 10:48 PM, Daniel Berlin <dberlin at dberlin.org> wrote:

Points-to level does not tell you much.

It is entirely possible for the relationship to go in the wrong direction. LLVM does not say it is illegal :) (IE it does not say that int *** can only point to int **)

On Fri, Jul 17, 2015 at 6:32 PM, Shen Liu <shl413 at lehigh.edu> wrote: > John, thanks for your helpful advice. > > My ultimate goal is to construct a full instruction-level program dependence > graph for a given IR file. The hard point is how to establish the correct > data dependence edges when some function arguments are multi-level pointers. > To solve this problem I hope to check the point-to level for each pointer > variable. I think the data dependence through pointers can be described more > accurately in this way. Unfortunately i didn't find any available interface > to finish this job, so i guess i have to write it by myself. > > Best regards, > > Shen > > > > On Fri, Jul 17, 2015 at 2:22 PM, John Criswell <jtcriswel at gmail.com> wrote: >> >> On 7/17/15 1:06 PM, Shen Liu wrote: >> >> John, thanks for you answer! But as far as I know LLVM doesn't provide >> any interface for finding the pointee of a pointer directly, so i have to >> process a multi-level pointer i need to write my own function to check >> pointers level by level, is that right? >> >> >> I'm not sure what you're trying to do. If you're trying to determine the >> LLVM pointer type and the LLVM type to which it points, what I've said will >> work. >> >> If you're trying to do something more complicated, then you need to >> explain more clearly what you want to do. I think it would also help if you >> "jumped up a level" and explained what your end goal is so that the >> community can give you better advice. Based on your previous emails, it >> seems like you're asking very specific questions instead of asking how to >> best achieve your overall goal. >> >> Regards, >> >> John Criswell >> >> >> >> On Fri, Jul 17, 2015 at 1:47 PM, John Criswell <jtcriswel at gmail.com> >> wrote: >>> >>> On 7/17/15 12:38 PM, Shen Liu wrote: >>> >>> Hi all, as a LLVM beginner I would like to know how can i check the >>> pointer types with different levels like int 32* and int 32**, int 32***? >>> >>> By using value->getType()->isPointerTy() i can just know they are >>> pointers. But the dump results clearly show they are different. Is there a >>> good way to calculate their actual point to levels? Thanks! >>> >>> >>> You will need to use dyncast to cast the Type * into a >>> PointerType *. Once you do that, you can find the Type * that the >>> PointerType points to. >>> >>> Regards, >>> >>> John Criswell >>> >>> >>> >>> Best regards, >>> >>> Shen >>> >>> _>>> ________________________ >>> LLVM Developers mailing list >>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu >>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev >>> >>> >>> >>> -- >>> John Criswell >>> Assistant Professor >>> Department of Computer Science, University of Rochester >>> http://www.cs.rochester.edu/u/criswell >> >> >> >> >> -- >> John Criswell >> Assistant Professor >> Department of Computer Science, University of Rochester >> http://www.cs.rochester.edu/u/criswell > > > _> ________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150718/161f289e/attachment.html>

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