[PATCH] D55974: [GVN] Update BlockRPONumber prior to use.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

This generally makes sense, I think.

The assumption here that blocks won't get erased during a GVN iteration is a little fragile... but probably okay.  Please make BlockRPONumber a `DenseMap<AssertingVH<BasicBlock>, uint32_t>` to make sure no future change erases a block at an unexpected point.



================
Comment at: lib/Transforms/Scalar/GVN.cpp:1652
+  // if some blocks have been split and added to F.
+  if (F.size() == BlockRPONumber.size())
+    return;
----------------
This doesn't have the performance characteristics you want: `F.size()` is linear in the size of the function.  Please use an explicit boolean to track invalidation.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55974/new/

https://reviews.llvm.org/D55974