[Bug rtl-optimization/106705] constant prop is not undone for switches

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106705

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
So you expect us to somehow generate

        val2 = -len;
        switch (len) {
        case 7:
                do_sd(val, mem, val2++);
        case 6:
                do_sd(val, mem, val2++);
        case 5:
                do_sd(val, mem, val2++);
        case 4:
                do_sd(val, mem, val2++);
        case 3:
                do_sd(val, mem, val2++);
        case 2:
                do_sd(val, mem, val2++);
        case 1:
                do_sd(val, mem, val2++);

?  (VRP on GIMPLE would undo that I suppose)