[PATCH] D57221: [LoopSimplifyCFG] Change logic of dead loops removal to avoid hitting asserts

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev marked an inline comment as done.
mkazantsev added inline comments.


================
Comment at: lib/Transforms/Scalar/LoopSimplifyCFG.cpp:408-409
+        Loop *DL = LI.getLoopFor(BB);
+        if (DL->getParentLoop()) {
+          for (auto *PL = DL->getParentLoop(); PL; PL = PL->getParentLoop())
+            for (auto *BB : DL->getBlocks())
----------------
uabelho wrote:
> mkazantsev wrote:
> > uabelho wrote:
> > > Perhaps replace
> > > 
> > >         if (DL->getParentLoop()) {
> > >           for (auto *PL = DL->getParentLoop(); PL; PL = PL->getParentLoop())
> > > 
> > > with
> > > 
> > >         while (auto *PL = DL->getParentLoop()) {
> > > 
> > > ?
> > And loop infinitely? :) We need to change DL somehow, otherwise PL is always the same loop.
> Doesn't
>  DL->getParentLoop()->removeChildLoop(DL);
> disconnect DL from PL, so in the next loop round DL doesn't have the old PL as parent anymore?
The line `DL->getParentLoop()->removeChildLoop(DL);` is executed once *after* this loop. You seem to be misreading the code. :)


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57221/new/

https://reviews.llvm.org/D57221