[llvm] [VPlan] Unroll VPReplicateRecipe by VF. (PR #142433)

[David Sherwood via llvm-commits]

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@@ -907,6 +907,12 @@ class VPInstruction : public VPRecipeWithIRFlags,
     BranchOnCount,
     BranchOnCond,
     Broadcast,
+    /// Creates a vector containing all operands. The vector element count
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david-arm wrote:

How does this work with scalable vectors? It sounds very similar to the BuildVector ISD node in codegen. If it's not expected to work for scalable element counts it's worth spelling it out explicitly in the comments I think.

https://github.com/llvm/llvm-project/pull/142433