[llvm-dev] TBAA for subset of a loaded value (original) (raw)

Sanjoy Das via llvm-dev llvm-dev at lists.llvm.org
Mon Apr 10 20:31:58 PDT 2017

Hi Hal,

On April 10, 2017 at 7:01:36 PM, Hal Finkel (hfinkel at anl.gov) wrote:

As I mentioned a few moments ago, I think we can just propagate the metadata.

Yes, that sounds a lot simpler. :)

The scheme I mentioned has the slight advantage that it further refines the metadata as we narrow accesses -- if we split up an i128 access into 4 i32 accesses, we'll be able to prove using TBAA metadata that those 4 i32 accesses do not alias each other.  However, I suspect that use case it not important.

-- Sanjoy

One thing which it worth pointing out is that, when TBAA checks an access, it does not actually check the access size (our struct path metadata has offsets in it, but we don't really use the sizes in conjunction with those, we're just checking for an offset match up the node hierarchy).

-Hal > > -- Sanjoy > > >> I would very much appreciate any guidance on the right approach to >> this (perfectly willing and planning to code this up myself - but >> would appreciate discussion on direction). >> >> Thanks, >> Keno _>> ________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> -- Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory

More information about the llvm-dev mailing list