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

[ppalka at gcc dot gnu.org]

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

--- Comment #4 from Patrick Palka <ppalka at gcc dot gnu.org> ---
On a related note I noticed the final code for

int test(int a) {
    return (a & CST) * 4 + 3;
}

is not optimal when CST is a power of two, e.g. when CST=8:

_Z4testi:
.LFB0:
        .cfi_startproc
        andl    $8, %edi
        leal    0(,%rdi,4), %eax
        addl    $3, %eax
        ret

The leal and the addl could be combined into a single leal.  When CST is not a
power of two then there is no addl.