[PATCH] D34619: [ARM] Enable partial and runtime unrolling

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

I don't see how a trip count which varies for each iteration of the parent loop implies the trip count is small.  I mean, it's possible it does for your particular benchmarks, but it seems unlikely to generalize to other code.



================
Comment at: lib/Target/ARM/ARMTargetTransformInfo.cpp:585
+    while (Parent) {
+      if (!SE.isLoopInvariant(ExitCount, Parent))
+        return;
----------------
There isn't any reason to check isLoopInvariant for each loop: if the count is invariant relative to the topmost loop, it will be invariant relative to every loop it contains.


https://reviews.llvm.org/D34619