Cross-ISA Testing of the Pharo VM: Lessons Learned While Porting to ARMv8

Guillermo Polito (1) , Pablo Tesone (2) , Stéphane Ducasse (2) , Luc Fabresse (3) , Théo Rogliano (2) , Pierre Misse-Chanabier (2) , Carolina Hernandez Phillips (2)

1 CRIStAL - Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189
2 RMOD - Analyses and Languages Constructs for Object-Oriented Application Evolution
3 IMT Nord Europe - Ecole nationale supérieure Mines-Télécom Lille Douai

Testing and debugging a Virtual Machine is a laborious task without the proper tooling. This is particularly true for VMs with JIT compilation and dynamic code patching for techniques such as inline caching. In addition, this situation is getting worse when the VM builds and runs on multiple target architectures. In this paper, we report on several lessons we learned while testing the Pharo VM, particularly during the port of its Cogit JIT compiler to the AArch64 architecture. The Pharo VM presented already a simulation environment that is very handy to simulate full executions and live-develop the VM. However, this full simulation environment makes it difficult to reproduce short and simple testing scenarios. We extended the pre-existing simulation environment with a testing infrastructure and a methodology that allow us to have fine-grained control of testing scenarios, making tests small, fast, reproducible, and cross-ISA. We report on how this testing infrastructure allowed us to cope with two different development scenarios: (1) porting the Cogit JIT compiler to AArch64 without early access to real hardware and (2) debugging memory corruptions due to GC bugs. CCS Concepts: • Software and its engineering → Runtime environments.

Mots clés: just-in-time compilers; virtual machines; ARM; testing; ports; Cross-ISA

Domaines: Langage de programmation [cs.PL]

Guillermo Polito, Pablo Tesone, Stéphane Ducasse, Luc Fabresse, Théo Rogliano, et al.. Cross-ISA Testing of the Pharo VM: Lessons Learned While Porting to ARMv8. MPLR ’21, Germany, Sep 2021, Münster, Germany. ⟨10.1145/3475738.3480715⟩. ⟨hal-03332033⟩