On Tue, May 09, 2017 at 07:57:11PM +0800, Jin, Yao wrote:
SNIP
> > > > > +
> > > > > + type >>= 2; /* skip X86_BR_USER and X86_BR_KERNEL */
> > > > > + mask = ~(~0 << 1);
> > > > is that a fancy way to get 1 into the mask? what do I miss?
> > you did not comment on this one
>
> Sorry, I misunderstood that this comment and the next comment had the same
> meaning.
>
> In the previous version, I used the switch/case to convert from X86_BR to
> PERF_BR. I got a comment from community that it'd better use a lookup table
> for conversion.
>
> Since each bit in type represents a X86_BR type so I use a mask (0x1) to
> filter the bit. Yes, it looks I can also directly set 0x1 to mask.
>
> I write the code "mask = ~(~0 << 1)" according to my coding habits. If you
> think I should change the code to "mask = 0x1", that's OK :)
im ok with that.. was just wondering for the reason
I guess compiler will make it single constant assignment anyway
>
> > > > > +
> > > > > + for (i = 0; i < X86_BR_TYPE_MAP_MAX; i++) {
> > > > > + if (type & mask)
> > > > > + return branch_map[i];
> > > > I wonder some bit search would be faster in here, but maybe not big deal
> > > >
> > > > jirka
> > > I just think the branch_map[] doesn't contain many entries (16 entries
> > > here), so maybe checking 1 bit one time should be acceptable. I just want
> > > to
> > > keep the code simple.
> > >
> > > But if the number of entries is more (e.g. 64), maybe it'd better check 2
> > > or
> > > 4 bits one time.
> > ook
> >
> > jirka
> Sorry, what's the meaning of ook? Does it mean "OK"?
just means ok ;-)
thanks,
jirka
