Originally we were inlining gen8_cs_irq_handler() and so expected the
compiler to constant-fold away the irq_shift (so we had hardcoded it as
opposed to use engine->irq_shift). However, we dropped the inline given
the proliferation of gen8_cs_irq_handler()s. If we pull the shifting
of the iir into
Quoting Chris Wilson (2018-03-09 01:08:08)
> Originally we were inlining gen8_cs_irq_handler() and so expected the
> compiler to constant-fold away the irq_shift (so we had hardcoded it as
> opposed to use engine->irq_shift). However, we dropped the inline given
> the proliferation of gen8_cs_irq_h