[Bug target/51838] Inefficient add of 128 bit quantity represented as 64 bit tuple to 128 bit integer.

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51838

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|middle-end                  |target
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-08-28
     Ever confirmed|0                           |1
           Keywords|                            |missed-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We do get slightly better now:
        xorl    %eax, %eax
        movq    %rdi, %r8
        xorl    %edi, %edi
        addq    %rsi, %rax
        adcq    %rdi, %rdx
        addq    %rax, (%r8)
        adcq    %rdx, 8(%r8)
        ret

Note on arch64 we do get good code:
        ldp     x3, x4, [x0]
        adds    x3, x3, x1
        adc     x4, x4, x2
        stp     x3, x4, [x0]
        ret