[PATCH 3/4 GCC11] IVOPTs Consider cost_step on different forms during unrolling

[Wilco Dijkstra]

Hi Kewen,

Would it not make more sense to use the TARGET_ADDRESS_COST hook
to return different costs for immediate offset and register offset addressing,
and ensure IVOpts correctly takes this into account?

On AArch64 we've defined different costs for immediate offset, register offset,
register offset with extend, pre-increment and post-increment.

I don't see why this has been defined to always return 0 on rs6000...

Wilco