Comment by bonzini

Copy and patch is a variant of QEMU's original "dyngen" backend by Fabrice Bellard[1][2], with more help from the compiler to avoid the maintainability issues that ultimately led QEMU to use a custom code generator.

[1] https://www.usenix.org/legacy/event/usenix05/tech/freenix/fu...

[2] https://review.gerrithub.io/plugins/gitiles/spdk/qemu/+/5a24...