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. -- Pinski _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
