Question

ATT syntax.

I’m trying to understand what the following piece of assembly code does:

movl  8(%ebp), %edx
movl  $0, %eax
testl %edx, %edx
je    .L7
.L10:
xorl  %edx, %eax
shrl  %edx
jne   .L10
.L7:
andl  $1, %eax

It’s supposed to be the body of a function with one parameter: unsigned x. I know that this is a do-while loop but how can I completely convert it to C code?

Answer 1

unsigned int function(unsigned int x)
{
  unsigned int a = 0;

  while (x != 0)
  {
    a = a ^ x;
    x = x >> 1;
  }

  a = a & 1;

  return a;
}