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Virtual machines - how they work

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Bartosz Sypytkowski

This document discusses the fundamentals of virtual machines (VMs), explaining their workings, including stack and register-based VMs, bytecode, and interpreters. It includes technical details about program execution, virtual stacks, bytecode structure, and various operations such as arithmetic and conditional branches. The document also provides a demo of a minimal virtual machine implementation and its operations.

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VIRTUAL MACHINES HOW DO THEY WORK? DO THEY WORK? LET’S FIND OUT!
INTRODUCTION Bartosz Sypytkowski ▪ @Horusiath ▪ b.sypytkowski@gmail.com ▪ bartoszsypytkowski.com
 What virtual machines are all about.  Stack vs Register based VMs  Bytecode and interpreters  Demo AGENDA
MOTIVATION
VIRTUAL MACHINE
SYSTEM VIRTUAL MACHINE PROCESS VIRTUAL MACHINE
STACK VS. REGISTER
STACK const.i32 3 const.i32 2 add.i32 Stack
STACK const.i32 3 const.i32 2 add.i32 Stack 3
STACK const.i32 3 const.i32 2 add.i32 Stack 2 3
STACK const.i32 3 const.i32 2 add.i32 Stack 3 2 5
ACTIVATION FRAMES arity return address function arg0 Activation frame fib(5) arity return address function arg0 Activation frame fib(4) Frame pointer
BYTECODE
20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b TEXT FORMAT BINARY FORMAT get_local 0 i64.const 0 i64.eq if i64 i64.const 1 else get_local 0 get_local 0 i64.const 1 i64.sub call 0 i64.mul end
WHY NOT AST?
Intermediate representations 1. .NET CIL 2. JVM bytecode 3. WASM 4. LLVM IR 5. MemSQL bytecode BYTECODE
INTERPRETER VS. COMPILER
ASSEMBLY NOT LOW-LEVEL LANGUAGE ANYMORE
BUT SERIOUSLY… WHO USES BYTECODE INTERPRETER ON PROD?
COMPAR ING VECTOR CLOCKS CASE STUDIES • pre 1.9 – AST interpreter • v1.9 (25 Dec 207) – YARV: bytecode interpreter • v2.6 (25 Dec 2018) – JIT (experimental) RUBY MRI CPYTHON • ATM still bytecode interpreted • Bytecode generated and cached in .pyc files
MULTI TIER CODE EXECUTION TIME Query parsing interpreter compiler execution execution Switch point compilation
DEMO
A MINIMAL VIRTUAL MACHINE 1. Program to execute 2. Instruction counter / program counter 3. Virtual stack (LIFO) 4. Stack pointer 5. Frame pointer
REMARKS 1. Not optimal 2. No debugger 3. No error handling 4. No local/global variables 5. Only one primitive supporter (Int32)
SSVM Bytecode 1. Constant 2. Add 3. Sub 4. Mul 5. JumpIfTrue 6. JumpIfFalse 7. Equal 8. LessThan 9. GreaterThan 10. Call 11. LoadArgument 12. Return 13. Halt 14. Print
SAMPLE PROGRAM // int fib(n) { // if(n == 0) return 0; LoadArgument 0 // 0 - load last function argument N Constant 0 // 2 - put 0 Equals // 4 - check equality: N == 0 JumpIfFalse 10 // 5 - if they are NOT equal, goto 10 Constant 0 // 7 - otherwise put 0 Return // 9 - and return it // if(n < 3) return 1; LoadArgument 0 // 10 - load last function argument N Constant 3 // 12 - put 3 LessThan // 14 - check if 3 is less than N JumpIfFalse 20 // 15 - if 3 is NOT less than N, goto 20 Constant 1 // 17 - otherwise put 1 Return // 19 - and return it // else return fib(n-1) + fib(n-2); LoadArgument 0 // 20 - load last function argument N Constant 1 // 22 - put 1 Sub // 24 - calculate: N-1, result is on the stack Call fib 1 // 25 - call fib function with 1 arg. from the stack LoadArgument 0 // 28 - load N again Constant 2 // 30 - put 2 Sub // 32 - calculate: N-2, result is on the stack Call fib 1 // 33 - call fib function with 1 arg. from the stack Add // 36 - since 2 fibs pushed their ret values on the stack, just add them Return // 37 - return from procedure // entrypoint - main function Constant 6 // 38 - put 6 Call fib 1 // 40 - call function: fib(arg) where arg = 6; Print // 43 - print result Halt // 44 - stop program
Virtual Machine typedef struct { int* code; // program opcodes int* stack; // virtual stack int pc; // program counter int sp; // stack pointer int fp; // frame pointer } VM; // push value on top of the stack #define PUSH(vm, v) vm->stack[++vm->sp] = v // pop value from top of the stack #define POP(vm) vm->stack[vm->sp--] // get next bytecode #define NEXT(vm) vm->code[vm->pc++] stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer
Interpreter Loop void (*op_handles[])(VM*) = { // opcode function pointers }; void vm_run(VM* vm) { do { int opcode = NEXT(vm); if (opcode == Halt) { return; } op_handles[opcode](vm); } while(1); }
Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer
Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x STDOUT
Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a + b
Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1
Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1
Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1 addr
Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1 addr
Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer addr
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc activation frame
Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc
LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc
LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc argx
LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc v frame pointer – 3 - argx
LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc v
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 result
Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer result
SUMMARY
 Crafting interpreters: https://craftinginterpreters.com/contents.html#a-bytecode-virtual-machine  Register-based VM: https://github.com/skx/simple.vm  Konrad Kokosa: “Pro .NET Memory Management”  Database query compilation: https://www.youtube.com/watch?v=baOAbOdcnxs  Adding new CIL instruction to .NET: https://mattwarren.org/2017/05/19/Adding-a-new-Bytecode- Instruction-to-the-CLR/  and many many more… REFERENCES
THANK YOU

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Virtual machines - how they work

  • 1. VIRTUAL MACHINES HOW DO THEY WORK? DO THEY WORK? LET’S FIND OUT!
  • 2. INTRODUCTION Bartosz Sypytkowski ▪ @Horusiath ▪ b.sypytkowski@gmail.com ▪ bartoszsypytkowski.com
  • 3.  What virtual machines are all about.  Stack vs Register based VMs  Bytecode and interpreters  Demo AGENDA
  • 12. ACTIVATION FRAMES arity return address function arg0 Activation frame fib(5) arity return address function arg0 Activation frame fib(4) Frame pointer
  • 14. 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b TEXT FORMAT BINARY FORMAT get_local 0 i64.const 0 i64.eq if i64 i64.const 1 else get_local 0 get_local 0 i64.const 1 i64.sub call 0 i64.mul end
  • 16. Intermediate representations 1. .NET CIL 2. JVM bytecode 3. WASM 4. LLVM IR 5. MemSQL bytecode BYTECODE
  • 18. ASSEMBLY NOT LOW-LEVEL LANGUAGE ANYMORE
  • 19. BUT SERIOUSLY… WHO USES BYTECODE INTERPRETER ON PROD?
  • 20. COMPAR ING VECTOR CLOCKS CASE STUDIES • pre 1.9 – AST interpreter • v1.9 (25 Dec 207) – YARV: bytecode interpreter • v2.6 (25 Dec 2018) – JIT (experimental) RUBY MRI CPYTHON • ATM still bytecode interpreted • Bytecode generated and cached in .pyc files
  • 22. DEMO
  • 23. A MINIMAL VIRTUAL MACHINE 1. Program to execute 2. Instruction counter / program counter 3. Virtual stack (LIFO) 4. Stack pointer 5. Frame pointer
  • 24. REMARKS 1. Not optimal 2. No debugger 3. No error handling 4. No local/global variables 5. Only one primitive supporter (Int32)
  • 25. SSVM Bytecode 1. Constant 2. Add 3. Sub 4. Mul 5. JumpIfTrue 6. JumpIfFalse 7. Equal 8. LessThan 9. GreaterThan 10. Call 11. LoadArgument 12. Return 13. Halt 14. Print
  • 26. SAMPLE PROGRAM // int fib(n) { // if(n == 0) return 0; LoadArgument 0 // 0 - load last function argument N Constant 0 // 2 - put 0 Equals // 4 - check equality: N == 0 JumpIfFalse 10 // 5 - if they are NOT equal, goto 10 Constant 0 // 7 - otherwise put 0 Return // 9 - and return it // if(n < 3) return 1; LoadArgument 0 // 10 - load last function argument N Constant 3 // 12 - put 3 LessThan // 14 - check if 3 is less than N JumpIfFalse 20 // 15 - if 3 is NOT less than N, goto 20 Constant 1 // 17 - otherwise put 1 Return // 19 - and return it // else return fib(n-1) + fib(n-2); LoadArgument 0 // 20 - load last function argument N Constant 1 // 22 - put 1 Sub // 24 - calculate: N-1, result is on the stack Call fib 1 // 25 - call fib function with 1 arg. from the stack LoadArgument 0 // 28 - load N again Constant 2 // 30 - put 2 Sub // 32 - calculate: N-2, result is on the stack Call fib 1 // 33 - call fib function with 1 arg. from the stack Add // 36 - since 2 fibs pushed their ret values on the stack, just add them Return // 37 - return from procedure // entrypoint - main function Constant 6 // 38 - put 6 Call fib 1 // 40 - call function: fib(arg) where arg = 6; Print // 43 - print result Halt // 44 - stop program
  • 27. Virtual Machine typedef struct { int* code; // program opcodes int* stack; // virtual stack int pc; // program counter int sp; // stack pointer int fp; // frame pointer } VM; // push value on top of the stack #define PUSH(vm, v) vm->stack[++vm->sp] = v // pop value from top of the stack #define POP(vm) vm->stack[vm->sp--] // get next bytecode #define NEXT(vm) vm->code[vm->pc++] stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer
  • 28. Interpreter Loop void (*op_handles[])(VM*) = { // opcode function pointers }; void vm_run(VM* vm) { do { int opcode = NEXT(vm); if (opcode == Halt) { return; } op_handles[opcode](vm); } while(1); }
  • 29. Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer
  • 30. Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
  • 31. Constant X void op_constant(VM* vm) { int x = NEXT(vm); PUSH(vm, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
  • 32. Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
  • 33. Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x
  • 34. Print void op_print(VM* vm) { int x = POP(vm); printf(“%dn”, x); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer x STDOUT
  • 35. Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 36. Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 37. Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 38. Add / Sub / Mul / Div void op_add(VM* vm) { int b = POP(vm); int a = POP(vm); //TODO: check overflow PUSH(vm, a + b); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a + b
  • 39. Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 40. Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 41. Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer a b
  • 42. Equal / Less / etc. void op_eq(VM* vm) { int b = POP(vm); int a = POP(vm); PUSH(vm, a == b ? 1 : 0); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1
  • 43. Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1
  • 44. Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1 addr
  • 45. Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer 1 addr
  • 46. Conditional Branches void op_jmp_eq(VM* vm) { int address = NEXT(vm); if (POP(vm)) { vm->pc = address; } } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer addr
  • 47. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer
  • 48. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr
  • 49. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc
  • 50. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc
  • 51. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp
  • 52. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc
  • 53. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc activation frame
  • 54. Call void op_call(VM* vm) { int addr = NEXT(vm); int argc = NEXT(vm); PUSH(vm, argc); PUSH(vm, vm->fp); PUSH(vm, vm->pc); vm->fp = vm->sp; vm->pc = addr; } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer addr argc fp pc
  • 55. LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc
  • 56. LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc argx
  • 57. LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc v frame pointer – 3 - argx
  • 58. LoadArgument void op_lda(VM* vm) { int argx = NEXT(vm); int v = vm->stack[vm->fp-argx-3]; PUSH(vm, v); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc v
  • 59. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
  • 60. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
  • 61. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp pc result
  • 62. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc fp result
  • 63. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 argc result
  • 64. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer arg0 result
  • 65. Return void op_ret(VM* vm) { int result = POP(vm); vm->pc = POP(vm); vm->fp = POP(vm); int argc = POP(vm); vm->sp -= argc; PUSH(vm, result); } stack 20 00 42 00 51 04 7e 42 01 05 20 00 20 00 42 01 7d 10 00 7e 0b code stack pointer program pointer frame pointer result
  • 67.  Crafting interpreters: https://craftinginterpreters.com/contents.html#a-bytecode-virtual-machine  Register-based VM: https://github.com/skx/simple.vm  Konrad Kokosa: “Pro .NET Memory Management”  Database query compilation: https://www.youtube.com/watch?v=baOAbOdcnxs  Adding new CIL instruction to .NET: https://mattwarren.org/2017/05/19/Adding-a-new-Bytecode- Instruction-to-the-CLR/  and many many more… REFERENCES