On 5 February 2016 at 16:17, Alex Bennée <alex.ben...@linaro.org> wrote: > > Peter Maydell <peter.mayd...@linaro.org> writes: >> 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.
The register in question is going to be caller-saves anyway, so no effect on spilling in the TCG code I think. thanks -- PMM
