[llvm] [LLVM][CodeGen][SVE] Add isel for bfloat unordered reductions. (PR #143540)

[Matt Arsenault via llvm-commits]

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@@ -688,6 +683,22 @@ void VectorLegalizer::PromoteSTRICT(SDNode *Node,
   Results.push_back(Round.getValue(1));
 }
 
+void VectorLegalizer::PromoteVECREDUCE(SDNode *Node,
+                                       SmallVectorImpl<SDValue> &Results) {
+  MVT OpVT = Node->getOperand(0).getSimpleValueType();
+  assert(OpVT.isFloatingPoint() && "Expected floating point reduction!");
+  MVT NewOpVT = TLI.getTypeToPromoteTo(Node->getOpcode(), OpVT);
+
+  SDLoc DL(Node);
+  SDValue NewOp = DAG.getNode(ISD::FP_EXTEND, DL, NewOpVT, Node->getOperand(0));
+  SDValue Rdx =
+      DAG.getNode(Node->getOpcode(), DL, NewOpVT.getVectorElementType(), NewOp,
+                  Node->getFlags());
+  SDValue Res = DAG.getNode(ISD::FP_ROUND, DL, Node->getValueType(0), Rdx,
+                            DAG.getIntPtrConstant(0, DL, /*isTarget=*/true));
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arsenm wrote:

Can we use 1 here? We are converting back so it should be exactly representable, but the other cases seem to not do this 

https://github.com/llvm/llvm-project/pull/143540