On Wed, Jun 26, 2024 at 3:09 PM Bernhard Übelacker <[email protected]> wrote: > > Hello list, > I was trying to do some debugging in bug [1071656]. > > But for some reason I receive with arm64 > in a process running with valgrind > and one without valgrind different results > from the following floating point instruction: > > => 0xaaaaaaaa4948 <ConvertToRational+104>: fcvtas w5, d8 > > With plain GDB: > (gdb) print $w5 > $2 = 323 > > > With valgrind+GDB: > (gdb) print $w5 > $2 = 322 > > And therefore the CI run fails and led to this bug [1071656] (at least with > arm64). > I was trying this first in a qemu arm64 VM on amd64, > but could observe this on real arm64 hardware too. > > Is there some knowledge about such an issue, or how to avoid this? > > [1071656] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1071656
I'm not sure if it matters, but Valgrind added support for the fcvtas using the following register types. See <https://valgrind.org/docs/manual/dist.news.old.html> and <https://bugs.kde.org/show_bug.cgi?id=340509>. fcvtas w12, s1 I think the difference between dN (your example) and sN (valgrind) register are bit widths. dN is 32-bit, and sN is 16-bit. (This may be a rabbit hole). Jeff
