Add support for single reductions in ComplexDeinterleavingPass (llvm#112875)

The Complex Deinterleaving pass assumes that all values emitted will
result in complex numbers, this patch aims to remove that assumption and
adds support for emitting just the real or imaginary components, not
both.

Author: NickGuy-Arm

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 {