https://github.com/tenderlove/tenderjit TenderJIT Intro Short Intro to TenderJIT

Pure Ruby JIT Compiler For Ruby

Agenda Why? Machine Types What is JIT? TenderJIT & Code

Why?

1. I’m not good at JITs

2. To See If I Could

I ❤ Ruby

Is this “real”?

Yes. It is Le JIT

But is it really “real”?

Is this a “real” JIT or a learning project?

No content

Code Execution How do machines work?

Two Machine Types Stack Machines Register Machines

Stack Machines

Stack Machine 5 + 3 push 5 push 3 plus Source Code Machine Code 5 3 8 Machine Stack

YARV is a Stack Machine

YARV Instructions $ cat thing.rb 5 + 3 $ ruby --dump=insns thing.rb == disasm: #@thing.rb:1 (1,0)-(1,5)> (catch: FALSE) 0000 putobject 5 ( 1)[Li] 0002 putobject 3 0004 opt_plus [CcCr] 0006 leave

Terminology

Stack Machine 5 + 3 push 5 push 3 plus Source Code Machine Code 5 3 Machine Stack PC (Program Counter) SP (Stack Pointer)

Stack Machine 5 + 3 push 5 push 3 plus Source Code Machine Code 5 3 Machine Stack 0 1 2 … -1 1 0

CFP = “Control Frame Pointer”

Control Frame Pointer Contains Information About the Current Frame def baz end def bar baz end def foo bar end foo Main Control Frame Pointers foo bar baz

Control Frame Pointer Contains Information About the Current Frame def add 5 + 3 end Field Description iseq Instruction Sequence (the method) PC Program Counter (what are we running right now?) SP Stack Pointer (what is on the stack?) opt_plus 3 5

EC = “Execution Context”

Register Machine (x86, ARM, etc)

Register Machine 5 + 3 mov r1, 5 mov r2, 3 add r1, r2 Source Code Machine Code Machine Registers Register Name Value r1 r2 r3 … 5 3 8

x86 Instructions int main(int argc, char *argv[]) { int x = 5; int y = 3; return x + y; } 100003fa2: mov dword ptr [rbp - 20], 5 100003fa9: mov dword ptr [rbp - 24], 3 100003fb0: mov eax, dword ptr [rbp - 20] 100003fb3: add eax, dword ptr [rbp - 24] Source Code Machine Code

x86 Instructions int main(int argc, char *argv[]) { int x = 5; int y = 3; return x + y; } 100003fa2: mov dword ptr [rbp - 20], 5 100003fa9: mov dword ptr [rbp - 24], 3 100003fb0: mov eax, dword ptr [rbp - 20] 100003fb3: add eax, dword ptr [rbp - 24] Source Code Machine Code

x86 Instructions int main(int argc, char *argv[]) { int x = 5; int y = 3; return x + y; } 100003fa2: mov dword ptr [rbp - 20], 5 100003fa9: mov dword ptr [rbp - 24], 3 100003fb0: mov eax, dword ptr [rbp - 20] 100003fb3: add eax, dword ptr [rbp - 24] Source Code Machine Code

x86 Instructions int main(int argc, char *argv[]) { int x = 5; int y = 3; return x + y; } 100003fa2: mov dword ptr [rbp - 20], 5 100003fa9: mov dword ptr [rbp - 24], 3 100003fb0: mov eax, dword ptr [rbp - 20] 100003fb3: add eax, dword ptr [rbp - 24] Source Code Machine Code Register “EAX”

x86 Instructions int main(int argc, char *argv[]) { int x = 5; int y = 3; return x + y; } 100003fa2: mov dword ptr [rbp - 20], 5 100003fa9: mov dword ptr [rbp - 24], 3 100003fb0: mov eax, dword ptr [rbp - 20] 100003fb3: add eax, dword ptr [rbp - 24] Source Code Machine Code

What is a JIT?

JIT: Machine Code at Runtime

Machine Code in Ruby require "fisk" require "fisk/helpers" # Allocate executable memory jitbuf = Fisk::Helpers.jitbuffer 4096 fisk = Fisk.new # Add 5 and 3 in machine language, and write to the JIT buffer fisk.asm(jitbuf) do mov rax, imm(5) # Store 5 in RAX mov r9, imm(3) # Store 3 in R9 add rax, r9 # Add R9 to RAX ret # Return from this function end # Define an add method define_method :add, &jitbuf.to_function([], Fiddle::TYPE_INT) p add # Call add and print it

TenderJIT: Translate YARV to Machine Code

Stack Machine to Register Machine