[IR] Add @llvm.complex.multiply intrinsic (WIP)

[fhahn]

rebased, still WIP

llvm/include/llvm/IR/Intrinsics.td

let IntrProperties = [IntrNoMem] in {
   def int_vector_reduce_umin : DefaultAttrsIntrinsic<[LLVMVectorElementType<0>],
                                          [llvm_anyvector_ty]>;
   def int_vector_reduce_fmax : DefaultAttrsIntrinsic<[LLVMVectorElementType<0>],
                                          [llvm_anyvector_ty]>;
   def int_vector_reduce_fmin : DefaultAttrsIntrinsic<[LLVMVectorElementType<0>],
                                          [llvm_anyvector_ty]>;
 }
 
+//===----- Complex math intrinsics ----------------------------------------===//
+
+def int_complex_multiply: DefaultAttrsIntrinsic<[llvm_anyvector_ty],
+                                                [LLVMMatchType<0>,LLVMMatchType<0>],
+                                                [IntrNoMem]>;
+
 //===----- Matrix intrinsics ---------------------------------------------===//
 
 def int_matrix_transpose
   : DefaultAttrsIntrinsic<[llvm_anyvector_ty],
               [LLVMMatchType<0>, llvm_i32_ty, llvm_i32_ty],
               [ IntrNoSync, IntrWillReturn, IntrNoMem, IntrSpeculatable, ImmArg<ArgIndex<1>>,
                ImmArg<ArgIndex<2>>]>;