[llvm] [RISCV] Remove last use of @llvm.experimental.vp.splat in RISCVCodeGenPrepare. NFCI (PR #170543)

[Luke Lau via llvm-commits]

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@@ -271,8 +271,10 @@ bool RISCVCodeGenPrepare::expandVPStrideLoad(IntrinsicInst &II) {
   IRBuilder<> Builder(&II);
   Type *STy = VTy->getElementType();
   Value *Val = Builder.CreateLoad(STy, BasePtr);
-  Value *Res = Builder.CreateIntrinsic(Intrinsic::experimental_vp_splat, {VTy},
-                                       {Val, II.getOperand(2), VL});
+  Value *Res = Builder.CreateIntrinsic(
+      Intrinsic::vp_merge, VTy,
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lukel97 wrote:

Now that I think about it, the original motivation for vp.splat was to avoid VL toggles if this expansion occurred in a loop: https://github.com/llvm/llvm-project/pull/98140#discussion_r1671314147

But I think that should be a solved problem now with RISCVVLOptimizer. So if a vp_merge gets folded to poison then it should still be fine in practice because the VL will get reduced anyway.

The vp_merge here is really only needed to preserve the test cases which return the vector instead of storing it with an EVL.

https://github.com/llvm/llvm-project/pull/170543