[PATCH] D115713: [LV] Don't apply "TinyTripCountVectorThreshold" for loops with compile time known TC.

[Dave Green via Phabricator via llvm-commits]

dmgreen added inline comments.


================
Comment at: llvm/test/Transforms/LoopVectorize/ARM/mve-known-trip-count.ll:7
 
-; Trip count of 5 - shouldn't be vectorized.
+; Trip count of 5 - vectorized with VF=4 plus one scalar iteration.
 ; CHECK-LABEL: tripcount5
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I don't think we want this - it is worse. At least that is what my benchmarks suggest.

That was the point of D101726. 1 vector + 1 masked vector iteration when unrolled was worse than 5 scalar because of the overheads of vector instructions. 1 vector + 1 scalar will be in the same boat.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115713/new/

https://reviews.llvm.org/D115713