[Bug middle-end/80131] powerpc: 1U << (31 - x) doesn't generate optimised code

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80131

--- Comment #5 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
And even with unsigned c, a shift by (30 - 0xffffffffU) is perfectly valid 
in C; that shift count evaluates to 31U.  Whereas a shift by 0xffffffffU 
is not valid C.