[llvm] [SelectionDAG] Add PARTIAL_REDUCE_U/SMLA ISD Nodes (PR #125207)

[Paul Walker via llvm-commits]

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@@ -7883,6 +7854,30 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
 
     break;
   }
+  case ISD::PARTIAL_REDUCE_UMLA:
+  case ISD::PARTIAL_REDUCE_SMLA: {
+    EVT AccVT = N1.getValueType();
+    EVT Input1VT = N2.getValueType();
+    EVT Input2VT = N3.getValueType();
+    assert(Input1VT == Input2VT &&
+           "Expected the second and third operands of the PARTIAL_REDUCE_MLA "
+           "node to have the same type!");
+    assert(VT == AccVT &&
+           "Expected the first operand of the PARTIAL_REDUCE_MLA node to have "
+           "the same type as its result!");
+    assert(Input1VT.getVectorElementCount().getKnownMinValue() %
+                   AccVT.getVectorElementCount().getKnownMinValue() ==
+               0 &&
+           "Expected the element count of the second and third operands of the "
+           "PARTIAL_REDUCE_MLA node to be a positive integer multiple of the "
+           "element count of the first operand and result!");
+    assert(Input1VT.getVectorElementType().getSizeInBits() <=
+               AccVT.getVectorElementType().getSizeInBits() &&
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paulwalker-arm wrote:

I think you can shrink this a little by using `Input1VT.getScalarValueSizeInBits() <= AccVT.getScalarValueSizeInBits() &&`?

FYI: Scalar and VectorElementType are kind of used interchangeably within code generation based on what looks  best at the time :)

https://github.com/llvm/llvm-project/pull/125207