Compiling Functions, Continued

Example of a simple function

source program

  def add(x:int,y:int)-> int :
	return x + y
  print(add(40, 2))

shrink

  def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
	return x + y
  def main()-> <class 'int'> :
	print(add(40, 2))
	return 0

reveal functions

  def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
	return x + y
  def main()-> <class 'int'> :
	print(add(%rip)(40, 2))
	return 0

limit functions

  def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
	return x + y
  def main()-> <class 'int'> :
	print(add(%rip)(40, 2))
	return 0

expose allocation

  def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
	return x + y
  def main()-> <class 'int'> :
	print(add(%rip)(40, 2))
	return 0

remove complex operands

  def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
	return x + y
  def main()-> <class 'int'> :
	fun.0 = add(%rip)
	tmp.1 = fun.0(40, 2)
	print(tmp.1)
	return 0

explicate control

def add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
_addstart:
	return x + y

def main()-> <class 'int'> :
_mainstart:
	fun.0 = add(%rip)
	tmp.1 = fun.0(40, 2)
	print(tmp.1)
	return 0

select

def _add()-> <class 'int'> :
_addstart:
	movq %rdi, x
	movq %rsi, y
	movq x, %rax
	addq y, %rax
	jmp _addconclusion

def _main()-> <class 'int'> :
_mainstart:
	leaq _add(%rip), fun.0
	movq $40, %rdi
	movq $2, %rsi
	callq *fun.0
	movq %rax, tmp.1
	movq tmp.1, %rdi
	callq _print_int
	movq $0, %rax
	jmp _mainconclusion

register allocation

def _add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
_addstart:
	movq %rdi, %rcx
	movq %rsi, %rdx
	movq %rcx, %rax
	addq %rdx, %rax
	jmp _addconclusion

def _main()-> <class 'int'> :
_mainstart:
	leaq _add(%rip), %rcx
	movq $40, %rdi
	movq $2, %rsi
	callq *%rcx
	movq %rax, %rcx
	movq %rcx, %rdi
	callq _print_int
	movq $0, %rax
	jmp _mainconclusion

patch instructions

def _add(x:<class 'int'>,y:<class 'int'>)-> <class 'int'> :
_addstart:
	movq %rdi, %rcx
	movq %rsi, %rdx
	movq %rcx, %rax
	addq %rdx, %rax
	jmp _addconclusion

def _main()-> <class 'int'> :
_mainstart:
	leaq _add(%rip), %rcx
	movq $40, %rdi
	movq $2, %rsi
	callq *%rcx
	movq %rax, %rcx
	movq %rcx, %rdi
	callq _print_int
	movq $0, %rax
	jmp _mainconclusion

prelude and conclusion

	.align 16
_addstart:
  movq %rdi, %rcx
  movq %rsi, %rdx
  movq %rcx, %rax
  addq %rdx, %rax
  jmp _addconclusion

	.align 16
_add:
  pushq %rbp
  movq %rsp, %rbp
  subq $0, %rsp
  jmp _addstart

	.align 16
_addconclusion:
  subq $0, %r15
  addq $0, %rsp
  popq %rbp
  retq 

	.align 16
_mainstart:
  leaq _add(%rip), %rcx
  movq $40, %rdi
  movq $2, %rsi
  callq *%rcx
  movq %rax, %rcx
  movq %rcx, %rdi
  callq _print_int
  movq $0, %rax
  jmp _mainconclusion

	.globl _main
	.align 16
_main:
  pushq %rbp
  movq %rsp, %rbp
  subq $0, %rsp
  movq $65536, %rdi
  movq $65536, %rsi
  callq _initialize
  movq _rootstack_begin(%rip), %r15
  jmp _mainstart

	.align 16
_mainconclusion:
  subq $0, %r15
  addq $0, %rsp
  popq %rbp
  retq