[PATCH] D108253: [WIP][X86] Introduce 'blend with broadcast' shuffle lowering strategy (PR50971)

Wed Sep 29 09:29:12 PDT 2021

RKSimon added inline comments.

================
Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:12798
+                                              /*BlendOfIdentitiesOnly=*/true);
+}
+
----------------
lebedev.ri wrote:
> RKSimon wrote:
> > lowerShuffleAsDecomposedShuffleMerge does some of this already - can we not extend that?
> I'm not following. That is exactly what i'm doing here, extending `lowerShuffleAsDecomposedShuffleMerge()`.
> The point of `lowerShuffleAsBlendOfIdentities()` is to be able to run the relevant portion
> of `lowerShuffleAsDecomposedShuffleMerge()` at some earlier point
> (before the full ` lowerShuffleAsDecomposedShuffleMerge()` invocation),
> catching the target pattern only.
I'm sorry, that was very badly worded - I was looking at the MVT::v4i64 case which is calling lowerShuffleAsBlendOfIdentities directly before lowerShuffleAsDecomposedShuffleMerge - not sure why I put the comment up here instead.

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https://reviews.llvm.org/D108253