Local variables optimization

[Hanzac Chen]

Hi,

Some idea: Maybe local stack use in the code compiled by GCC should be
optimized 'cause some local variables are conditional. If the condition
is not satisfied, then these variables don't need to be allocated from
the stack (e.g. sub $VAR_SIZE, %esp).

For example:

int *func(unsigned int cond, unsigned i)
{
   switch (cond)
   {
	case 1:
	{  int d[0x10];
	   i = memset(d, i, 0x10);
	}
	case 2:
	{  int e[0x10];
	   i = memset(e, i, 0x10);
	}
	case 3:
	{  int f[0x10];
	   i = memset(f, i, 0x10);
	}
	default:
	  break;
   }
   return 1;
}

After compiled by GCC, you'll see GCC allocated all the local variables
in case 1/case 2/case 3, this is stupid.

Hanzac