[llvm] [RISCV][TTI] Implement cost of llvm.experimental.vector.extract.last.active (PR #184067)

[Luke Lau via llvm-commits]

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@@ -1702,6 +1702,29 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
                                CmpInst::FCMP_UNO, CostKind);
     return Cost;
   }
+  case Intrinsic::experimental_vector_extract_last_active: {
+    Type *ValTy = ICA.getArgTypes()[0];
+    Type *MaskTy = ICA.getArgTypes()[1];
+
+    auto ValLT = getTypeLegalizationCost(ValTy);
+    auto MaskLT = getTypeLegalizationCost(MaskTy);
+
+    if (!ValLT.first.isValid() || !MaskLT.first.isValid())
+      return InstructionCost::getInvalid();
+
+    // TODO: Return free when the entire lane is inactive.
+    // The expected asm sequence is:
+    // vid v10, v0.t
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lukel97 wrote:

Is there not also a vcpop.m emitted? This is checking llvm/test/codegen/riscv/rvv/vector-extract-last-active.ll

https://github.com/llvm/llvm-project/pull/184067