[Bug tree-optimization/71336] Suboptimal x86 code generated for "(a & 1) ? (CST1 + CST2) : CST1"

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71336

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|rtl-optimization            |tree-optimization

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #3)
> I guess it could be useful even without lea.

Pretty much.
Even on aarch64 we get for the original case:
        ubfiz   w0, w0, 2, 1
        add     w0, w0, 3
        ret
vs
        tst     x0, 1
        mov     w2, 7
        mov     w1, 3
        csel    w0, w2, w1, ne
        ret

For something slightly different:
unsigned test(unsigned a) {
    return a & 4 ? 7 : 3;
}

unsigned test1(unsigned a)
{
  a &= 4;
  a >>= 2;
  return a*4 + 3;
}

----
We get:
        tst     x0, 4
        mov     w2, 7
        mov     w1, 3
        csel    w0, w2, w1, ne
        ret
vs
        and     w0, w0, 4
        add     w0, w0, 3
        ret