CS 301 Homework 4 Solutions

/* C function prototype (C++ requires 'extern "C"' here; otherwise the same) */
int mul_vcheck(int a,int b);

__asm__( // Assembly subroutine
"mul_vcheck:\n"  
"  mov 4(%esp),%eax\n"  // Load a into eax
"  mov 8(%esp),%ebx\n"  // Load b into ebx
"  mul %ebx\n"
"  jb overflow\n" // Jumps if CF is set
"  ret\n" /* Normal return -- returns product eax */
"overflow:\n"
"  mov $-1,%eax\n"
"  ret\n" /* Return -1 on overflow */
);

unsigned int fact(unsigned int n) { 
	if (n<=1) return 1; /* fact(1)==1 */ 
	else return mul_vcheck(n,fact(n-1)); /* fact(n)==n*fact(n-1) */
}

int foo(void) {
	int i;
	for (i=1;i<=20;i++) print_int(fact(i));
	return 0;
}

extern "C" void sort_ints(int *arr,int n);

/* qsort-compatible comparison routine */
extern "C" int compare(int *a,int *b)
{ return *a-*b; }

__asm__( /* Assembly function body */
"sort_ints:\n"
"  push %ebp\n"
"  mov %esp,%ebp\n"
"  push $compare\n"
"  push $4\n"
"  push 12(%ebp)\n" /* n */
"  push 8(%ebp)\n" /* Arr */
"  # call print_stack\n"
"  call qsort\n"
"  leave\n"
"  ret\n"
);

int foo(void) {
   int i,n=read_input();
   int *arr=new int[n];
   for (i=0;i<n;i++)    
      arr[i]=rand()&0xf;
   sort_ints(arr,n);
   for (i=0;i<n;i++)
      std::cout<<i<<" = "<<arr[i]<<std::endl;
   delete[] arr;
   return 0;
}

fooextern "C" void add_ints(int *arr,int n);

__asm__( /* Assembly function body */
"add_ints:\n"
"  mov 4(%esp),%eax\n" /* arr */
"  mov 8(%esp),%ecx\n" /* n */
"  mov $0,%ebx\n" /* i=0 */
"  jmp Lcompare\n"
"Lstart:\n"
"  add $100,(%eax,%ebx,4)\n" /* adds 100 to memory at eax+ebx*4 */
"  inc %ebx\n" /* i++ */
"Lcompare:\n"
"  cmp %ecx,%ebx\n" /* if i<n goto start */
"  jl Lstart\n"
"  ret\n"
);

int foo(void) {
   int i,n=read_input();
   int *arr=new int[n];
   for (i=0;i<n;i++)    
      arr[i]=rand()&0xf;
   add_ints(arr,n);
   for (i=0;i<n;i++)
      std::cout<<i<<" = "<<arr[i]<<std::endl;
   delete[] arr;
   return 0;
}

extern "C" int call_rdtsc(void);

__asm__(
"call_rdtsc:\n"
"  rdtsc\n"  /* Returns tsc in %eax (low) and %edx (high, ignored) */
"  ret\n"
);

int foo(void) {
  int t1=call_rdtsc();
  int t2=call_rdtsc();
  return t2-t1;
}