[llvm-branch-commits] [llvm] [LV] Only create partial reductions when profitable. (PR #181706)

[Benjamin Maxwell via llvm-branch-commits]

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@@ -6216,10 +6195,17 @@ getScaledReductions(VPReductionPHIRecipe *RedPhiR, VPCostContext &CostCtx,
     if (!PHISize.hasKnownScalarFactor(ExtSrcSize))
       return std::nullopt;
 
+    /// Check if a partial reduction chain is supported by the target (i.e.
+    /// does not have an invalid cost) for the given VF range. Clamps the range
+    /// and returns true if feasible for any VF.
     VPPartialReductionChain Chain(
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MacDue wrote:

For another PR: I think we should also rename `VPPartialReductionChain` to just `VPPartialReduction`, calling it a "chain" is somewhat confusing when mixed with chained partial reductions. 

https://github.com/llvm/llvm-project/pull/181706