[PATCH] D101924: [X86] Improve costmodel for scalar byte swaps

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


================
Comment at: llvm/lib/Target/X86/X86.td:519
+    : SubtargetFeature<"fast-movbe", "HasFastMOVBE", "true",
+    "Prefer a movbe over a single-use load + bswap / single-use bswap + store">;
+
----------------
lebedev.ri wrote:
> RKSimon wrote:
> > You say 'prefer' - is a future intention to alter isel depending on this? I'm not sure that's actually useful.
> > You say 'prefer' - is a future intention to alter isel depending on this?
> 
> Not really. I was only interested in doing what is contained in this patch,
> i.e. modelling bswap as free in costmodel, if it will be free.
I guess technically different codegen might still occur if the costs come out slightly different and the vectorizer 'prefers' scalar code - sorry for the noise.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101924/new/

https://reviews.llvm.org/D101924