[llvm] [llubi] Implement experimental vector intrinsics (PR #206899)

[Yingwei Zheng via llvm-commits]

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@@ -1629,6 +1727,159 @@ class InstExecutor : public InstVisitor<InstExecutor, void>,
     case Intrinsic::experimental_noalias_scope_decl:
       // FIXME: Not implemented yet. Currently it acts as a noop.
       return AnyValue();
+    case Intrinsic::experimental_cttz_elts: {
+      auto *IsZeroPoisonC = cast<ConstantInt>(CB.getArgOperand(1));
+      const bool IsZeroPoison = IsZeroPoisonC->isOne();
+
+      const auto &Vec = Args[0].asAggregate();
+      const unsigned RetBW = RetTy->getIntegerBitWidth();
+
+      if (!isUIntN(RetBW, Vec.size()))
+        return AnyValue::poison();
+
+      uint64_t Count = 0;
+      for (const AnyValue &V : Vec) {
+        if (V.isPoison())
+          return AnyValue::poison();
+        if (!V.asInteger().isZero())
+          break;
+        ++Count;
+      }
+
+      if (Count == Vec.size() && IsZeroPoison)
+        return AnyValue::poison();
+      return APInt(RetBW, Count);
+    }
+    case Intrinsic::experimental_get_vector_length: {
+      auto *VFC = cast<ConstantInt>(CB.getArgOperand(1));
+      auto *ScalableC = cast<ConstantInt>(CB.getArgOperand(2));
+
+      if (Args[0].isPoison())
+        return AnyValue::poison();
+
+      const APInt &Cnt = Args[0].asInteger();
+      const uint64_t VF = VFC->getZExtValue();
+      const bool Scalable = ScalableC->isOne();
+
+      const uint64_t MaxLanes = Ctx.getEVL(ElementCount::get(VF, Scalable));
+
+      uint64_t Res = 0;
+      if (!Cnt.isZero()) {
+        if (Cnt.getActiveBits() <= 64 && Cnt.getZExtValue() <= MaxLanes) {
+          Res = Cnt.getZExtValue();
+        } else {
+          auto ceilUDiv = [](const APInt &N, const APInt &D) {
+            APInt Q = N.udiv(D);
+            if (!N.urem(D).isZero())
+              ++Q;
+            return Q;
+          };
+
+          APInt Max(Cnt.getBitWidth(), MaxLanes);
+          APInt NumIters = ceilUDiv(Cnt, Max);
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dtcxzyw wrote:

Use `APIntOps::RoundingUDiv`.

https://github.com/llvm/llvm-project/pull/206899