5 ms·

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 t

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/full_papers/bellard/bellard.pdf https://www.usenix.org/legacy/event/usenix05/tech/freenix/fu... [2] https://review.gerrithub.io/plugins/gitiles/spdk/qemu/+/5a246934eb737c242e28995641c9ebf80477b0b7/dyngen.c https://review.gerrithub.io/plugins/gitiles/spdk/qemu/+/5a24...

monocasa 3y ago
Which itself is how I understand the compilation step of quaject code in the synthesis kernel to have worked. Ie. do constant propagation and dead code elimination on the input format, and use a simple template driven backend to dump out native machine code. In fact I wouldn't be surprised if the earliest compilers were template based, as that's about the only implementation that would fit in a RAM as a compiler pass.
twbarr 3y ago
Ultimately, most good ideas were first implemented by Fabrice Bellard.
- KRAKRISMOTT 3y ago
  Copy and patch goes all the way back to Grace Hopper's original compiler implementation
  - lifthrasiir 3y ago
    They were called "template-based" JIT and copy-and-patch approach is not new in this regard. The novel idea of copy-and-patch JIT was an automatic code generation via relocatable objects. (By the way, QEMU is indeed cited as an inspiration for copy-and-patch JIT.)
- darknavi 3y ago
  I am happy to see him working on QuickJS in the last month or so. It could really use some ES2023 love!
- fuzztester 3y ago
  Heard of him; he's done a lot of stuff. So is he the Bourbaki of software? https://en.m.wikipedia.org/wiki/Nicolas_Bourbaki https://en.m.wikipedia.org/wiki/Nicolas_Bourbaki
  - vanderZwan 3y ago
    While I'm sure some people theorize that Fabrice Bellard is actually a pseudonym of a collective of 10x programmers, he is as far as I know just one person.
    - fuzztester 3y ago
      He he, I forgot to add a wink at the end of my question above.

monocasa 3y ago

Which itself is how I understand the compilation step of quaject code in the synthesis kernel to have worked. Ie. do constant propagation and dead code elimination on the input format, and use a simple template driven backend to dump out native machine code. In fact I wouldn't be surprised if the earliest compilers were template based, as that's about the only implementation that would fit in a RAM as a compiler pass.

twbarr 3y ago

Ultimately, most good ideas were first implemented by Fabrice Bellard.

KRAKRISMOTT 3y ago
Copy and patch goes all the way back to Grace Hopper's original compiler implementation
- lifthrasiir 3y ago
  They were called "template-based" JIT and copy-and-patch approach is not new in this regard. The novel idea of copy-and-patch JIT was an automatic code generation via relocatable objects. (By the way, QEMU is indeed cited as an inspiration for copy-and-patch JIT.)
darknavi 3y ago
I am happy to see him working on QuickJS in the last month or so. It could really use some ES2023 love!
fuzztester 3y ago
Heard of him; he's done a lot of stuff. So is he the Bourbaki of software? https://en.m.wikipedia.org/wiki/Nicolas_Bourbaki https://en.m.wikipedia.org/wiki/Nicolas_Bourbaki
- vanderZwan 3y ago
  While I'm sure some people theorize that Fabrice Bellard is actually a pseudonym of a collective of 10x programmers, he is as far as I know just one person.
  - fuzztester 3y ago
    He he, I forgot to add a wink at the end of my question above.