[Bug rtl-optimization/66552] Missed optimization when shift amount is result of signed modulus

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66552

--- Comment #10 from Segher Boessenkool <segher at gcc dot gnu.org> ---
What makes shift amount special at all, for those gimple simplifications?