Shockwave/boundary-layer interactions (SBLI) are an important design consideration for many aeronautical flows, including supersonic engine intakes and transonic wings. In many simulations of these phenomena span-periodicity is assumed, neglecting complex flow phenomena resulting from physical flow confinement. In this paper 3D SBLI with sidewall confinement effects are simulated for laminar and transitional boundary layers, in the automatic source code generation framework OpenSBLI. An incident shock of wave angle 31.6◦ impinges on a laminar boundary layer for a Mach 2 inlet. The incident shock interacts with both the sidewall and bottom wall boundary layers, causing large regions of flow reversal. A laminar base flow is obtained, which is then forced to transition by the introduction of upstream disturbances. A 6th order Targeted Essentially non-Oscillatory (TENO) scheme is used for shock capturing. OpenSBLI generates code in the domain specific language of the Oxford Parallel Structured software (OPS), which is then translated to a range of parallel programming paradigms. All computations were performed on multi-GPU configurations of NVIDIA P100/V100 GPUs.