[PATCH] D20379: Codegen: Fix broken assumption in Tail Merge.

[Haicheng Wu via llvm-commits]

haicheng added a comment.

I checked the modifications to the broken test cases.

I think you still break v8_IT_5.ll and licm-dominance.ll.  What is your plan about these two?

Your modifications to missinglabel.ll and eh.ll are reasonable.

Your patch causes unnecessary branches in thumb2-cbnz.ll and br-fold.ll, but I think it is not your fault.  I will try to create a patch to merge empty blocks so that your change would not break these two.


================
Comment at: lib/CodeGen/BranchFolding.cpp:969
@@ -966,1 +968,3 @@
     MachineBasicBlock *PredBB = &*std::prev(I);
+    if (PredBB && !PredBB->isSuccessor(IBB))
+      PredBB = nullptr;
----------------
iteratee wrote:
> That to me implies that it will be null if there is no such predecessor.
> I need to know if you want me to remove it from this patch.
Please remove it from this patch.  I think it is not closely related to the rest of the change.

I understand your concern and do not have strong opinion about it.  If you insist, it might be better to do it in your next patch.


http://reviews.llvm.org/D20379