On 2011-12-07, at 21:28, Arnaud Lacombe wrote: > Hi, > > On Sat, Nov 19, 2011 at 5:01 AM, Gleb Kurtsou <gleb.kurt...@gmail.com> wrote: >> Hi, >> >> I was lucky to write a bit of code which gcc 4.2 fails to compile >> correctly with -O2. Too keep long story short the code fails for gcc >> from base system and last gcc 4.2 snapshot from ports. It works with gcc >> 4.3, gcc 4.4 on FreeBSD and Linux. Clang from base is also good. -O and >> -Os optimization levels are fine (I've tried with all -f* flags >> mentioned in documentation) >> >> -O2 -fno-omit-frame-pointer combination is troublesome on amd64. I >> presume i386 should be fine. These options are also used for >> compilation of kernel (with debugging enabled) and modules. >> >> I'm not able to share the code, but have a test case reproducing the >> bug. I've encountered the issue over a week ago and tried narrowing it down >> to a simple test I could share but without much success. >> >> The code itself is very common: initialize two structs on stack, call a >> function with pointers to those stucts as arguments. A number of inlined >> assertion functions. gcc fails to correctly optimize struct assignments >> with -fno-omit-frame-pointer, I have a number of small structs assigned, >> gcc decides not to use data coping but to assign fields directly. I've >> tried disabling sra, tweaking sra parameters -- no luck in forcing it >> to copy data. Replacing one particular assignment with memcpy produces >> correct code, but that's not a solution. >> >> -O2 -fno-omit-frame-pointer -fno-inline is buggy >> -O2 -fno-omit-frame-pointer -frename-registers is buggy >> >> I found similar issue with gcc 4.6, but I'm not able to reproduce it >> with gcc test case: >> https://bugzilla.redhat.com/show_bug.cgi?id=679924 >> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47893 >> > this PR seems highly irrelevant, the cause has been identified to a > commit made in mid-2010, that's 3 years older than gcc in base. > >> I'll be glad to help debugging it and will be hanging on #bsddev during >> weekend as glk. >> > at least, can you share the testcase and miscompilation details ?
I believe we suffer from a very similar issue on PowerPC as well, we'll provide detailed information shortly. Rafal _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
