Ruby JIT Hacking Guide / RubyKaigi 2023

Ruby JIT Hacking Guide
https://rubykaigi.org/2023/

1. Ruby JIT Hacking Guide @k0kubun
2. @k0kubun
3. RJIT ERB Haml Slim I maintain
4. What's JIT?
5. Ruby JITs MJIT Ruby 2.6
6. Ruby JITs YJIT Ruby 3.1 MJIT Ruby 2.6
7. Ruby JITs YJIT Ruby 3.1 MJIT Ruby 2.6 RJIT Ruby 3.3
8. Railsbench Speedup relative to 2.5 No JIT (s/s) 0 0.5 1 1.5 2 Ruby 2.5 Ruby 2.6 Ruby 2.7 Ruby 3.0 Ruby 3.1 Ruby 3.2 Ruby 3.3 1.93 1.85 1.54 1.59 1.2 1.25 1.08 1.05 1.07 1.26 1.24 1.12 1.09 1.05 1.07 1 No JIT MJIT / RJIT YJIT
9. Ruby 3.2 YJIT
10. Ruby 3.3 YJIT
11. Using YJIT • Install Rust and then build Ruby • Use --yjit or export RUBY_YJIT_ENABLE=1
12. Ruby JIT Hacking Guide
13. Ruby Hacking Guide
14. Ruby JIT Hacking Guide JIT JIT
15. How Ruby JIT works Ruby
16. How Ruby JIT works 1 + 2 Ruby Abstract 
 Syntax 
 Tree
17. How Ruby JIT works 1 + 2 putobject 1 putobject 2 opt_plus leave Ruby Abstract 
 Syntax 
 Tree Instruction 
 Sequence 
 (Bytecode)
18. How Ruby JIT works 1 + 2 putobject 1 putobject 2 opt_plus leave Ruby Abstract 
 Syntax 
 Tree Instruction 
 Sequence 
 (Bytecode) Machine 
 Code
19. x86_64 assembly
20. • Read asm comments •--yjit-dump-disasm •--rjit-dump-disasm x86_64 assembly
21. • mov: assignment instruction • esi: register for stack[0] x86_64 assembly stack[0] = 3
22. x86_64 assembly • mov: assignment instruction • edi: register for stack[1] stack[0] = 3 stack[1] = 5
23. x86_64 assembly • add,sub: arithmetic instruction • rax: temporary register stack[0] = 3 stack[1] = 5 temp = stack[0] temp -= 1 temp += stack[1]
24. x86_64 assembly • jo: jump if over fl ow • rsi: register for stack[0] stack[0] = 3 stack[1] = 5 temp = stack[0] temp -= 1 temp += stack[1] jump if overflow stack[0] = temp
25. x86_64 encoding
26. x86_64 encoding opv86: https://hikalium.github.io/opv86/
27. x86_64 encoding opv86: https://hikalium.github.io/opv86/
28. Calling a custom JIT Ruby 3.2 Ruby 3.3+ 1. Run Ruby with --mjit=pause --rjit=pause 2. Override RubyVM::MJIT.compile RubyVM::RJIT#compile 3. Call RubyVM::MJIT.resume RubyVM::RJIT.resume
29. Building JIT is fun
30. k0kubun/ruby-jit-challenge Ruby JIT Challenge
31. Ruby JIT Challenge Hashtag: #ruby-jit-challenge Speedup relative to No JIT (s/s) 0 3 6 9 12 No JIT RJIT YJIT Ruby JIT 11.08 6.31 3.75 1 Fibonatti benchmark
32. Optimizing Ruby JIT
33. Side exits side exit
34. Method rede fi nition Rede fi nition Hook Invalidate
35. Method rede fi nition Rede fi nition Hook Invalidate side exit
36. Constant rede fi nition
37. Register allocation: Stack 0: rsi 1: rdi 4: r10 2: r8 3: r9 VM stack
38. Register allocation: Stack 0: rsi 1: rdi 4: r10 2: r8 3: r9 VM stack
39. Register allocation: Local variables • Spill registers on C function calls • Binding • debug_inspector API
40. Polymorphic method cache
41. Splitting
42. Method inlining
43. Conclusion • Enjoy custom JIT development • Let's make YJIT the best Ruby JIT