[llvm] [RISCV] Merge zeroing stores into wider LMUL vector stores (PR #223908)

[Luke Lau via llvm-commits]

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@@ -217,8 +217,16 @@ class RISCVTargetLowering : public TargetLowering {
 
   bool storeOfVectorConstantIsCheap(bool IsZero, EVT MemVT, unsigned NumElem,
                                     unsigned AddrSpace) const override {
-    // If we can replace 4 or more scalar stores, there will be a reduction
-    // in instructions even after we add a vector constant load.
+    // A zero splat is free to materialize, so merging is a win once it
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lukel97 wrote:

Is this comment accurate? A zero splat isn't free since it needs a vmv.v.i

https://github.com/llvm/llvm-project/pull/223908