[PATCH] D91718: [LV] Legalize scalable VF hints

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:5375
+
+    unsigned FixedVF = PowerOf2Floor(MaxSafeRegisterWidth / WidestType);
+    // If scalable, scale VF by vscale before checking if it's safe.
----------------
nit: `MaxSafeElements`?


================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:5377
+    // If scalable, scale VF by vscale before checking if it's safe.
+    ElementCount MaxSafeVF =
+        UserVF.isScalable()
----------------
Instead of returning an Optional<ElementCount>, I'd prefer the code here to just clamp to MaxFixedVF,
in this order:
* first try to see if it can use the requested scalable VF.
* if not, then try to see if it can use the requested VF with vscale = 1 (i.e. fixed width)
* if not, then try if it can use a clamped fixed VF.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91718/new/

https://reviews.llvm.org/D91718