[PATCH] D126885: [SLP]Cost for a constant buildvector.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:5783
+           E->UserTreeIndices.front().UserTE->isAltShuffle())
+              ? 0
+              : E->UserTreeIndices.front().UserTE->getOpcode();
----------------
vdmitrie wrote:
> Just wondering is that possible for UserTreeIndices to be empty here? AFAIU it can be for root only but constants do not seed vtree.
> if alternate opcodes are for shl/shr but shift value is splat it is still can be immediate for both of them.
> 
1. If constants are reduced values in reduction ops.
2. That's why there is a TODO above.


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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:5802
+      } else {
+        InstructionCost ScalarCost = 0;
+        for (Value *V : VL) {
----------------
vdmitrie wrote:
> drop it?
What do you mean?


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  https://reviews.llvm.org/D126885/new/

https://reviews.llvm.org/D126885