[PATCH] D96522: [LV] Try larger VFs if VF is unprofitable for small types.

[Florian Hahn via Phabricator via llvm-commits]

fhahn added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:5795
+  if (SmallestType <= 32 && SmallestType < WidestType &&
+      !MaxVectorSize.isScalable()) {
+    Type *SmallVT = FixedVectorType::get(
----------------
sdesmalen wrote:
> nit: this condition is currently always true. Can you change this into an assert?
I updated the code to support scalable vectors. But it seems like the cost model considers loads of `<vscale x 4 x i8>` as expensive as `<vscale x 16 x i8>` so the higher VF isn't chosen for scalable vectors. And the maximized fixed VF seems to be more profitable than the scalable one, so we end up choosing `<16 x i8>`  (see the scalable tests)


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  https://reviews.llvm.org/D96522/new/

https://reviews.llvm.org/D96522