[PATCH] D131028: [AArch64] Fix cost model for FADD vector reduction

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

I think the new costs are a lot better, but I worry about the implications of setting the fadd reduction costs. The SLP vectorizer will be the main user and whilst they might be correct in isolation, I worry about the comparative cost vs scalar fma. D125987 <https://reviews.llvm.org/D125987> for example was trying to fix the same thing.



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Comment at: llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp:2740
+    Type *EltType = ValTy->getElementType();
+    if (!EltType->isDoubleTy() && !EltType->isFloatTy() && !EltType->isHalfTy())
+      break;
----------------
HalfTy requires FullFP16, otherwise it gets unrolled. For example: https://godbolt.org/z/57WEb99q3


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D131028/new/

https://reviews.llvm.org/D131028