On Thu, Mar 7, 2013 at 12:24 AM, Mike Hommey <mh-...@glandium.org> wrote: > Hi, > > At Mozilla, we've encountered a GCC 4.6 miscompilation in the ARMv6 > build of Firefox for Android. We'd like to evaluate whether this bug is > hitting us in more places than the one we spotted. To that end, we'd > need to know what particular bug in GCC leads to this miscompilation. > > The attached file is the preprocessed source, slightly simplified. I was > able to reproduce the miscompilation with both the GCC 4.6 from the > Android NDK r8d and 4.6.3 from Debian unstable. It apparently happens > for any -march, with -marm, but not -mthumb. It happens at -Os but not > -O2.
No attached file. Also does -fno-strict-aliasing fix it? Thanks, Andrew > > The problematic assembly looks like the following. It corresponds to > the C code after the second call to DER_SetUInteger in sftk_mkPrivKey:: > > bl DER_SetUInteger(PLT) > mov r3, #0 > cmp sl, r3 > movne r0, #2 > moveq r0, r3 > > sl/r10 is never set anywhere in the function, so we're getting random > behaviour. > > This doesn't happen with GCC 4.7, which suggests it may be a known bug. > Any ideas? > > Cheers, > > Mike
