[Bug target/95704] PPC: int128 shifts should be implemented branchless

[jens.seifert at de dot ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95704

--- Comment #5 from Jens Seifert <jens.seifert at de dot ibm.com> ---
Power9 code is branchfree but not good at all.

_Z3shloy:
.LFB0:
        .cfi_startproc
        addi 8,5,-64
        subfic 6,5,63
        srdi 10,3,1
        li 7,0
        sld 4,4,5
        sld 5,3,5
        cmpwi 7,8,0
        srd 10,10,6
        sld 3,3,8
        or 4,10,4
        isel 5,5,7,28
        isel 4,4,3,28
        mr 3,5
        blr

13 instructions.