On Wed, 23 Oct 2019 at 18:06, Richard Henderson <richard.hender...@linaro.org> wrote: > > Using a variable that is declared "const" for this tells the > compiler that it may read the value once and assume that it > does not change across function calls. > > For target_page_size, this means we have only one assert per > function, and one read of the variable. > > This reduces the size of qemu-system-aarch64 by 8k. > > Reviewed-by: Paolo Bonzini <pbonz...@redhat.com> > Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> + * We want to declare the "target_page" variable as const, which tells > + * the compiler that it can cache any value that it reads across calls. > + * This avoids multiple assertions and multiple reads within any one user. > + * > + * This works because we initialize the target_page data very early, in a > + * location far removed from the functions that require the final results. I have to say that this feels like a worryingly large amount of magic. Is this actually guaranteed to work by the compiler? thanks -- PMM
