[llvm-dev] Disable combining of loads and stores in instcombine

JF Bastien via llvm-dev llvm-dev at lists.llvm.org
Wed Apr 17 10:48:27 PDT 2019

> On Apr 17, 2019, at 10:40 AM, Neil Ryan <neilryan at cs.washington.edu> wrote:
>> But why is it desirable to avoid combining adjacent stores? If you’ve got DRF code then the combination can’t be observed. 
> It’s more that the consecutive stores would be going to different tiles. If multiple stores are combined in IR, I don’t think they’d be able to decoupled in IR, unless there’s a way to always determine which global object an arbitrary GEP is pointing to.

That does seem like a valid use case, albeit one that C / C++ and LLVM IR can’t really help you with today. Volatile has the limitations you’ve described, and relaxed atomics could be combined as you’d like to avoid (though they probably won’t be right now).
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