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

[pinskia at gcc dot gnu.org]

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

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #7)
> (In reply to Andrew Pinski from comment #6)
> > (In reply to Li Jia He from comment #5)
> > > Could we consider doing this optimization on gimple? I use the following
> > > code on gimple to produce optimized results on powerpc64.
> > 
> > It might make sense.  But fold-const.c might not be the correct location;
> > match.pd might be a better place for it.
> 
> Something like:
> (simplify
>  (rshift @0 (mod @1 integer_pow2p@2))
>  (rshift @0 (bit_and @1 (minus @1 { build_int_cst (TREE_TYPE (@1), 1); }))))

Some typos:
(simplify
 (rshift @0 (mod @1 integer_pow2p@2))
 (rshift @0 (bit_and @1 (minus @2 { build_int_cst (TREE_TYPE (@2), 1); }))))

This would be under the for:
(for mod (ceil_mod floor_mod round_mod trunc_mod)