With the advent of advanced energy management systems in distribution systems, there is a growing interest in rapid and reliable code for distribution system state estimation (DSSE) in large-scale systems. Fast DSSE methods employed in the industry are based on load scaling as they are well suited to the abundance of pseudo-measurements. Due to the paucity of real-time measurements in DSSE, phasor measurement units (PMUs) have been proposed as a potential solution to increase the estimation accuracy. However, load scaling methodologies are not extendable for exploiting PMUs. This paper proposes a high-performance DSSE method that can handle the PMUs together with all common measurement types in industrial DSSE. By using Wirtinger calculus, the method operates entirely in complex variables and employs the latest version of advanced vector extensions (AVX-2) to reap the maximum potential of computer processing units. The paper highlights the derivation of complex DSSE in matrix form, from which one can infer the implications on code reliability and maintenance. Numerical results are reported on large-scale multi-phase distribution systems, and they are contrasted with a publicly available code for DSSE in real variables. The simulation results show that loop unrolling in AVX-2 contributes about a two-fold increase in the solving speed.