[llvm] [RISCV] Add codegen support for ri.vinsert.v.x and ri.vextract.x.v (PR #136708)

[Luke Lau via llvm-commits]

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@@ -9705,6 +9712,26 @@ SDValue RISCVTargetLowering::lowerINSERT_VECTOR_ELT(SDValue Op,
         return Vec;
       return convertFromScalableVector(VecVT, Vec, DAG, Subtarget);
     }
+
+    // Use ri.vinsert.v.x if available.
+    if (Subtarget.hasVendorXRivosVisni() && VecVT.isInteger() &&
+        isValidVisniInsertExtractIndex(Idx)) {
+      unsigned Policy = RISCVVType::TAIL_UNDISTURBED_MASK_UNDISTURBED;
+      if (VecVT.isFixedLengthVector() && isa<ConstantSDNode>(Idx) &&
+          Idx->getAsZExtVal() + 1 == VecVT.getVectorNumElements())
+        Policy = RISCVVType::TAIL_AGNOSTIC;
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lukel97 wrote:

I'm aware that this is copied from the existing case below, but if the VL here is always going to be >= VLMAX then can we not always set RISCVVType::TAIL_AGNOSTIC? 

https://github.com/llvm/llvm-project/pull/136708