[PATCH] D139927: [VPlan] Remove redundant blocks by merging them into predecessors.

[Ayal Zaks via Phabricator via llvm-commits]

Ayal added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp:310
+  ReversePostOrderTraversal<VPBlockRecursiveTraversalWrapper<VPBlockBase *>>
+      RPOT(Plan.getEntry());
+  for (VPBlockBase *VPB : RPOT)
----------------
fhahn wrote:
> Ayal wrote:
> > Is RPOT needed (due to destructive / make_early_inc_range) or would depth_first suffice?
> > 
> > Suffice to iterate over blocksOnly<VPBasicBlock> and tryToMerge[Basic]BlockIntoPredecessor(VPBasicBlock)?
> Unforunately `depth_first` doesn't support `make_early_inc_range` at the moment, I am not sure if that's because of VPBlockRecursiveTraversalWrapper or something else.
> 
> > Suffice to iterate over blocksOnly<VPBasicBlock> and tryToMerge[Basic]BlockIntoPredecessor(VPBasicBlock)?
> 
> Done, thanks!
Another option may be to scan depth_first and push candidates VPBB's onto a stack that is later traversed (succ before pred) to merge each candidate into its predecessor and delete it. This could potentially minimize RPOT copying overhead, although VPlan sizes are currently small(?)


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  https://reviews.llvm.org/D139927/new/

https://reviews.llvm.org/D139927