[llvm] [SelectionDAG][RISCV] Move VP_REDUCE* legalization to LegalizeDAG.cpp. (PR #90522)

[Pengcheng Wang via llvm-commits]

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@@ -2979,6 +2986,49 @@ SDValue SelectionDAGLegalize::ExpandPARITY(SDValue Op, const SDLoc &dl) {
   return DAG.getNode(ISD::AND, dl, VT, Result, DAG.getConstant(1, dl, VT));
 }
 
+void SelectionDAGLegalize::PromoteReduction(SDNode *Node,
+                                            SmallVectorImpl<SDValue> &Results) {
+  MVT VecVT = Node->getOperand(1).getSimpleValueType();
+  MVT NewVecVT = TLI.getTypeToPromoteTo(Node->getOpcode(), VecVT);
+  MVT ScalarVT = Node->getSimpleValueType(0);
+  MVT NewScalarVT = NewVecVT.getVectorElementType();
+
+  SDLoc DL(Node);
+  SmallVector<SDValue, 4> Operands(Node->getNumOperands());
+
+  // promote the initial value.
+  // FIXME: Support integer.
+  assert(Node->getOperand(0).getValueType().isFloatingPoint() &&
+         "Only FP promotion is supported");
+  Operands[0] =
+      DAG.getNode(ISD::FP_EXTEND, DL, NewScalarVT, Node->getOperand(0));
+
+  for (unsigned j = 1; j != Node->getNumOperands(); ++j)
+    if (Node->getOperand(j).getValueType().isVector() &&
+        !(ISD::isVPOpcode(Node->getOpcode()) &&
+          ISD::getVPMaskIdx(Node->getOpcode()) == j)) { // Skip mask operand.
+      // promote the vector operand.
+      // FIXME: Support integer.
+      assert(Node->getOperand(j).getValueType().isFloatingPoint() &&
+             "Only FP promotion is supported");
+      Operands[j] =
+          DAG.getNode(ISD::FP_EXTEND, DL, NewVecVT, Node->getOperand(j));
+    } else {
+      Operands[j] = Node->getOperand(j); // Skip VL operand.
+    }
+
+  SDValue Res = DAG.getNode(Node->getOpcode(), DL, NewScalarVT, Operands,
+                            Node->getFlags());
+
+  if (ScalarVT.isFloatingPoint())
+    Res = DAG.getNode(ISD::FP_ROUND, DL, ScalarVT, Res,
+                      DAG.getIntPtrConstant(0, DL, /*isTarget=*/true));
+  else
+    Res = DAG.getNode(ISD::TRUNCATE, DL, ScalarVT, Res);
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wangpc-pp wrote:

Is this a dead code now?

https://github.com/llvm/llvm-project/pull/90522