As can be seen in https://godbolt.org/z/qvMqY79cK, a urem by a power-2
constant will be code-generated as an And of a mask. The cost model for
funnel shifts tries to account for that by passing OP_PowerOf2 as the
operand info for the second operand. As far as I can tell returning a
lower cost for urem with a OP_PowerOf2 is only implemented on X86
though.
This patch short-cuts that by calling getArithmeticInstrCost(And, ..)
directly when we know the typesize will be a power-of-2. This is an
alternative to the patch in #126912 which is a more general solution for
power-2 udiv/urem costs, this more narrowly just fixes funnel shifts.
b2165f214e