[PATCH] D22025: AMDGPU/SI: Do not insert EndCf in an unreachable block

[Changpeng Fang via llvm-commits]

cfang added inline comments.

================
Comment at: test/CodeGen/AMDGPU/si-annotate-cf-unreachable.ll:30-34
@@ +29,7 @@
+
+bb4:                                              ; preds = %bb3
+  unreachable
+
+bb5:                                              ; preds = %bb3, %bb1
+  unreachable
+}
----------------
arsenm wrote:
> cfang wrote:
> > arsenm wrote:
> > > There should still be another copy of this function with blocks with code (like a volatile store) before the unreachable
> > The issue is: for an unreachable block, if we insert EndCf, we will hit "Instruction does not dominate all uses!" assert!
> > 
> > The "fix" here is actually just a workaround: if there is no instruction before unreachable, we don't insert EndCf.
> > 
> > If as you suggested there are instructions before unreachable, we will have to insert endCF, and the problem is still there.
> > 
> > This is a special case in control flow that both "else" and "then" is unreachable. Maybe we need to insert endCF on 
> > both paths. 
> > 
> You check at the insertion point if it is unreachable, not that the block ends in unreachable. That's what I want the other test for, to make sure it doesn't crash in that case. I think what you might really want to be doing is checking for no successors
Can you use a simple example to show me what do you want to test? I am afraid that the test you request should still fail with this patch.


https://reviews.llvm.org/D22025