https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95766
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Richard Biener from comment #2) > The ABI specifies 'a' is appropriately extended to %rdi IIRC I don't think so. This is one of the things where GCC and LLVM use different ABI: https://bugs.llvm.org/buglist.cgi?quicksearch=42439%2C19909%2C44228%2C12207 and from what I remember, Micha or Honza expressed the intent of the ABI to be undefined upper bits.
