[PATCH] D68128: [InstCombine] Fold PHIs with equal incoming pointers

[Artur Pilipenko via Phabricator via llvm-commits]

apilipenko added a comment.

Can we handle the case with inbounds offsets only first and extend with non-inbounds support in a follow up change? This way in the first change you'll not need to change IR interfaces at all.



================
Comment at: llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp:1163-1164
+      // Make sure the insertion point exists.
+      if (InsertPtIter != InsertBB->end())
+        InsertPt = &*InsertPtIter;
+    } else
----------------
It's ok to insert at the end of BB. 

Use `IRBuilder::SetInsertPoint(BasicBlock *TheBB, BasicBlock::iterator IP)` for that. After this change there will be no situation when `InsertPt` is available, so the code can structured slightly differently:
```
  if (auto *BaseInst = dyn_cast<Instruction>(Base)) {
    if (isa<PHINode>(BaseInst))
      Builder.SetInsertPoint(BaseInst->getParent(), BaseInst->getParent()->getFirstInsertionPt())
    else
      Builder.SetInsertPoint(BaseInst->getNextNode());
  } else
    Builder.SetInsertPoint(...);
``` 


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D68128/new/

https://reviews.llvm.org/D68128