On Sun, Feb 17, 2008 at 01:45:23AM -0800, Andrew Pinski wrote: > On Feb 16, 2008 9:58 AM, Willy Tarreau <[EMAIL PROTECTED]> wrote: > > Last but not least, gcc 4 tends to emit stupid checks, to the point that I > > have replaced unlikely(x) with (x) in my code when gcc >= 4 is detected. > > What > > I observe is that the following code : > > > > if (unlikely(p == NULL)) ... > > > > often gets coded like this : > > > > reg1 = (p == NULL) > > if (reg1 != 0) ... > > > > ... which clobbers reg1 for nothing and performs a double test. > > This really only can happen in GCC 4.0.x and 4.1.x and cannot happen > for 4.2 or 4.3 really because of the way __builtin_expect is handled > for those two.
Happy to know that, thanks for the info Andrew! Willy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
