[PATCH] D45535: [DSE] Teach the pass that atomic memory intrinsics are stores.

[Daniel Neilson via Phabricator via llvm-commits]

dneilson added inline comments.


================
Comment at: lib/Transforms/Scalar/DeadStoreElimination.cpp:868
       LoadedLoc = MemoryLocation::get(V);
     } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(BBI)) {
       LoadedLoc = MemoryLocation::getForSource(MTI);
----------------
dneilson wrote:
> dmgreen wrote:
> > This one? This function does it's own special version of DSE. It's about removing stores to dead stack objects iirc.
> Good catch. Thanks!
> 
> Looks like there might not be a test for this case at all. I'll try to add one of those as well.
Made the change, but I'm having difficulty creating a test that gets to here. Calls to the memtransfer intrinsics end up getting into the conditional at line 838, above:

```
      // If the call might load from any of our allocas, then any store above
      // the call is live.
      DeadStackObjects.remove_if([&](Value *I) {
        // See if the call site touches the value.
        return isRefSet(AA->getModRefInfo(CS, I, getPointerSize(I, DL, *TLI)));
      });
```

The source argument for the intrinsic aliases the stack object(s), and this bit of code at 868 ends up having no effect. 


Repository:
  rL LLVM

https://reviews.llvm.org/D45535