[PATCH] D35609: [LICM] Make sinkRegion and hoistRegion non-recursive

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy added inline comments.


================
Comment at: lib/Transforms/Scalar/LICM.cpp:348
+  SmallVector<BasicBlock *, 16> Worklist;
+  DT->getDescendants(N->getBlock(), Worklist);
 
----------------
majnemer wrote:
> sanjoy wrote:
> > `getDescendants` seems to be doing a BFS.  Given that (and that DT is a tree), can you iterate `Worklist` in reverse to get a post order?  If you do this, we'd have to spec `getDescendants` as doing a BFS though (and not just have it be an implementation detail).
> > 
> > OTOH if you write the BFS by hand (instead of relying on `getDescendents`), you can add an early exit for `CurLoop->contains(BB)`.
> Do you mean BFS or DFS?
I meant BFS; since DT is a tree you can do a (slightly) cheaper in-place BFS as:

```
Order.push_back(N);
for (int i = 0; i < Order.size(); i++)
  Order.push_back(N->children());
```



https://reviews.llvm.org/D35609