Wirth's compilers generated reasonably good code: 80% of the performance of optimizing compilers with 20% of the effort.
The first Java client jit compiler, was developed by Robert Griesemer (former PhD student of Wirth). The design of the compiler is described in the paper "A compiler for the java hotspot virtual machine", published in the same book: "The School of Niklaus Wirth: The Art of Simplicity".