Peter Maydell <peter.mayd...@linaro.org> writes: > On 5 February 2016 at 14:20, Alex Bennée <alex.ben...@linaro.org> wrote: >> >> Peter Maydell <peter.mayd...@linaro.org> writes: >>> -typedef CPAccessResult CPAccessFn(CPUARMState *env, const ARMCPRegInfo >>> *opaque); >>> +typedef CPAccessResult CPAccessFn(CPUARMState *env, >>> + const ARMCPRegInfo *opaque, >>> + bool isread); >> >> I guess my only comment here is we've extended the call for every access >> check with another parameter (and associated TCG activity) for something >> only one handler currently cares about. >> >> Is there an argument for an rwaccessfn() that we use for just those >> registers that care about the detail? I know system registers are hardly >> a fast path priority but I'm concerned about knock on effects on >> performance. Have you done any measurements? > > I haven't measured, no, but since there are only 3 arguments the > third argument is going to be in a register on any host architecture > we care about, which means the overhead is just going to be a single > "load constant 0 or 1 into register before the call". I think that's > going to be lost in the noise compared to actually having to make > the function call at all, the work the function call does, and then > the second function call later to do the read or write.
I was thinking of knock on effects on spilling other registers in the TCG code. I guess this depends on how complex the code is around system register access. > > thanks > -- PMM -- Alex Bennée
