[PATCH] D65088: [AMDGPU][RFC] New llvm.amdgcn.ballot intrinsic

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

Also should add GlobalISel tests



================
Comment at: llvm/lib/Target/AMDGPU/SIISelLowering.cpp:8684
+
+      return DCI.DAG.getCopyFromReg(DCI.DAG.getEntryNode(), SDLoc(N), Exec, VT);
+    }
----------------
Flakebi wrote:
> arsenm wrote:
> > I didn't think of it before, but reading exec this way could potentially be dangerous due to the fact that we have the terrible operations that modify exec in the middle of IR blocks, and we split them later. We might have to do this fold later
> What are these operations and how can I fix them?
> And shouldn’t this work as the instruction reads exec and thus should not be touched?
You can't really fix them in SelectionDAG. Things like the wwm/wqm intrinsics, and kills can exist in the middle of blocks (plus inline asm)


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  https://reviews.llvm.org/D65088/new/

https://reviews.llvm.org/D65088