QLLVM: A Scalable Quantum-Classical Co-Compilation Framework based on LLVM

TL;DR

QLLVM is a scalable, LLVM-based quantum-classical co-compilation framework that unifies classical and quantum program building, optimizing quantum circuits and enabling efficient hybrid program compilation.

Contribution

It introduces an end-to-end LLVM-based workflow for quantum and classical program integration with high-level optimizations and hardware mapping.

Findings

QLLVM reduces circuit depth and gate counts on MQTBench.

It demonstrates advantages in compiling hybrid classical-quantum programs.

Provides an extensible architecture for quantum software development.

Abstract

To address the urgent need in the NISQ era for high-performance, scalable quantum compilers and to advance the integration of classical and quantum computing, we present QLLVM, an advanced Quantum-Classical co-compilation framework built on LLVM. To our knowledge, QLLVM delivers an end-to-end, LLVM-based compilation workflow that unifies the build of classical high-performance programs, including CUDA, MPI, and C++, together with quantum programs into a single executable. For quantum program compilation, QLLVM adopts a three-stage design: high-level optimizations are implemented in the MLIR Quantum dialect and then lowered to QIR, an LLVM IR-based representation, for low-level optimization and hardware mapping. Its extensible architecture and seamless interoperability with classical high-performance computing provide an efficient, flexible, industrial-grade compilation infrastructure for future quantum software development. Experimental results show that, on the MQTBench benchmark suite, QLLVM reduces circuit depth and gate counts compared with state-of-the-art compilers and demonstrates clear advantages in compiling hybrid classical-quantum programs.