[llvm] [LV] Handle partial reductions with predication (PR #194859)

[Benjamin Maxwell via llvm-commits]

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@@ -6786,6 +6807,15 @@ getScaledReductions(VPReductionPHIRecipe *RedPhiR, VPCostContext &CostCtx,
   // Work backwards from the ExitValue examining each reduction operation.
   VPValue *CurrentValue = ExitValue;
   while (CurrentValue != RedPhiR) {
+    VPBlendRecipe *Blend = nullptr;
+    if (auto *B = dyn_cast<VPBlendRecipe>(CurrentValue)) {
+      if (B->getNumIncomingValues() != 2)
+        return std::nullopt;
+
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MacDue wrote:

It's important for the getMask(0) that's used later when transforming to  partial reductions. I guess the assert could be moved there.

https://github.com/llvm/llvm-project/pull/194859