On 09/24/2010 10:37 AM, Stefan Hajnoczi wrote:
On Fri, Sep 24, 2010 at 01:50:39AM +0400, malc wrote:
On Thu, 23 Sep 2010, Stefan Hajnoczi wrote:
The get_bits_from_size() calculates the log base-2 of a number. This is
useful in bit manipulation code working with power-of-2s.
Currently used by qcow2 and needed by qed in a follow-on patch.
int ilog2 (size_t size)
{
if (size& (size - 1))
return -1;
return __builtin_ctzl (size);
}
Ifdef WIN64 omitted for brevity.
What is the situation with WIN64?
long is only 32 bit, so you need __builtin_ctzll.
Paolo
