[PATCH] D112717: [IR] Replace *all* uses of a constant expression by corresponding instruction

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added inline comments.


================
Comment at: llvm/lib/IR/ReplaceConstant.cpp:93
+  for (auto Item : Visited)
+    Item.first->removeDeadConstantUsers();
 }
----------------
hsmhsm wrote:
> rampitec wrote:
> > Why not to remove it immediately?
> Consider below example, where C2 uses lds.  In this case, we have two paths, but both the paths have same sequence, that is (C1, C2).  So,  it again causes the same bug which https://reviews.llvm.org/D104425 has fixed. That is, we land up replacing already dead constant expression. 
> 
> 
> ```
>                                    I
>                                  /  \
>                                C1   C1
>                               /        \
>                              C2        C2
> ```
> 
I mean, dead users are already dead users. In this case you would just call `removeDeadConstantUsers` twice, which shall not be a problem as far as I understand. Just why a separate loop is needed?


Repository:
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  https://reviews.llvm.org/D112717/new/

https://reviews.llvm.org/D112717