On May 31, 2011, at 3:46 AM, Alexander Best <arun...@freebsd.org> wrote:
> On Tue May 31 11, Dimitry Andric wrote: >> On 2011-05-31 11:57, Alexander Best wrote: >> ... >>>>> however i've often read messages - mostly by bruce evans - claiming that >>>>> anything greater than -O will in fact decrease a kernel's ability to be >>>>> debugged just as well as a kernel with -O. >>>> The critical option when -O2 is used is -fno-omit-frame-pointers, since >>>> removing >>>> frame pointers makes debugging impossible (on i386). With -O2 code is >>>> moved around and >>>> removed, so debugging is more difficult, but can still provide useful >>>> information. >>> any reason we cannot use -O2 -fno-omit-frame-pointers -fno-strict-aliasing >>> as >>> standard COPTFLAGS with debugging enabled for *all* archs? >> >> Most likely, the performance gain from -O2 is rather small, except for >> special cases, but the pain during debugging is increased a great deal. >> >> Even if you add frame pointers, with -O2 large pieces of code can be >> transformed, variables or even entire functions can be completely >> eliminated, and so on, making debugging much more difficult. > > *lol* we're moving in circles. so back to the beginning: why not use -O > for all archs, if debugging was enabled? for amd64 -O2 is always set, no > matter, if debugging is enabled or disabled. I don't know, but I've run into cases where gcc has inlined or shuffled around code on amd64 with -O2 -fno-strict-aliasing, so I changed my make.conf to use -O0 when DEBUG_FLAGS was defined. Thanks, -Garrett_______________________________________________ freebsd-toolchain@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-toolchain To unsubscribe, send any mail to "freebsd-toolchain-unsubscr...@freebsd.org"
