[Bug target/85669] fail on s-case-cfn-macros: build/gencfn-macros: DEF_INTERNAL_FLT/INT_FN (%smth%) has no associated built-in functions

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85669

--- Comment #29 from Segher Boessenkool <segher at gcc dot gnu.org> ---
It aligns the stack to 16:

        # r3 is size, at entry
        addi r3,r3,18
        ...
        rlwinm r3,r3,0,0,27
        ...
        neg r3,r3
        ...
        lwz r2,0(r1)
        ...
        stwux r2,r1,r3

(the rlwinm is  r3 &= ~15;  )