Complex deinterleaving/single reductions build fix Reapply "Add suppo…

…rt for single reductions in ComplexDeinterleavingPass (llvm#112875)"  (llvm#120441)

This reverts commit 76714be, fixing the
build failure that caused the revert.

The failure stemmed from the complex deinterleaving pass identifying a
series of add operations as a "complex to single reduction", so when it
tried to transform this erroneously identified pattern, it faulted. The
fix applied is to ensure that complex numbers (or patterns that match
them) are used throughout, by checking if there is a deinterleave node
amidst the graph.

llvm/include/llvm/CodeGen/ComplexDeinterleavingPass.h

@@ -35,6 +35,7 @@ struct ComplexDeinterleavingPass
 enum class ComplexDeinterleavingOperation {
   CAdd,
   CMulPartial,
+  CDot,
   // The following 'operations' are used to represent internal states. Backends
   // are not expected to try and support these in any capacity.
   Deinterleave,
@@ -43,6 +44,7 @@ enum class ComplexDeinterleavingOperation {
   ReductionPHI,
   ReductionOperation,
   ReductionSelect,
+  ReductionSingle
 };
 
 enum class ComplexDeinterleavingRotation {