Question about assembly in set bit function for x86 architecture

[nick]

Greetings All,
I am wondering what the below code in the asm modifier does:
static inline void set_bit(int nr, void *addr)
{
         asm("btsl %1,%0" : "+m" (*(u32 *)addr) : "Ir" (nr));
}
This would be very helpful as I am new to  x86 assembly and don't
even known what register(s)/instruction(s) this touches and therefore this
is impossible for me to look up in the Intel Manuals. If someone either
tells me the registers/instructions this uses or explains the code that
would be very helpful.
Nick