[Bug target/82580] Optimize comparisons for __int128 on x86-64

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82580

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Nice.  I wonder about one further thing.
With your patch, we generate e.g. in f0:
        xorq    %rdx, %rdi
        xorq    %rcx, %rsi
        xorl    %eax, %eax
        orq     %rsi, %rdi
        sete    %al
i.e. for the flags we first clear %eax and then setX %al, but for f2
        cmpq    %rdi, %rdx
        sbbq    %rsi, %rcx
        setb    %al
        movzbl  %al, %eax
Seems this is done in
;; Convert setcc + movzbl to xor + setcc if operands don't overlap.
peephole2s, do we need a peephole for this as well, or some more general
peephole2 or other means of optimizing this?