gistfile1.txt

// ABI: fastcall
asm (
   ".text\n"
   ASM_CO_SWAP_DEF
   "movl %esp, (%edx) # Save stack pointer, and restore it again.\n"
   "movl (%ecx), %esp\n"
   "popl %eax\n"

   "movl %ebp, 0x4(%edx) # Save non-volatile registers to buffer.\n"
   "movl %esi, 0x8(%edx)\n"
   "movl %edi, 0xc(%edx)\n"
   "movl %ebx, 0x10(%edx)\n"

   "movl 0x4(%ecx), %ebp # Restore non-volatile registers from buffer.\n"
   "movl 0x8(%ecx), %esi\n"
   "movl 0xc(%ecx), %edi\n"
   "movl 0x10(%ecx), %ebx\n"

   "jmp *%eax # Jump back to saved PC.\n"
);