jextract woes

[Michael Zucchi]

On 1/2/20 1:57 am, Maurizio Cimadamore wrote:
> I'm not sure I get what you are asking here - I'm pretty sure the old 
> Libraries.bind could not be used for things like the ones you 
> described. The only difference between old and new is that in the old 
> world, Libraries.bind was actually generating a brand new class - at 
> runtime - to implement a given interface (generated by jextract) based 
> on the contents of some annotations. If you want to use something like 
> that in a core framework like the JDK you realize that you are pulling 
> in more dependencies than really needed - in fact the JDK wouldn't 
> even start if we tried to use the binder-based approach because that 
> was trying to parse annotation and spin classfiles _while_ the JDK 
> itself was still being initialized. So, in terms of footprint and 
> dependencies, the new approach is much better - some preliminary tests 
> I did using an OpenGL demo, the time to first drawn frame dropped 4x 
> when switching to the new bindings. And there's lots of room for 
> improvements (generating classfile could make all the MH 
> initialization lazy, which means you pay only for the MH you use). 

Above is regarding the dynamic binding, and yeah you could do it.  See 
below, this was one of my first experiments with panama.

Given that you were building classes dynamically and then loading them 
during initialisation, well it's perhaps no wonder it was slower?

Also, what I was asking was simple: "where is the performance hit" of 
using a call to downcallHandle() at runtime vs using a 
CONSTANT_MethodHandle_info.  Does it only affect startup-time (as you 
imply above), or does it affect the invokeExact() calls as well?

At some point I will try some startup-time experiments although I'm not 
sure of the best way to measure them.


     @NativeHeader()
     public interface APIExt {

         @NativeFunction(value="(i32)v")
         public void funca(int a);

         @NativeFunction(value="(i32)i32")
         public int funcb(short b);

         @NativeFunction(value="(f32)i32")
         public int funcc(float b);

         @NativeFunction(value="(f32)i32")
         public int funcd(float b);

         public static APIExt bind(APILib lib) {
             APIExt ext = Libraries.bind(APIExt.class, (String name)->{
                     Scope ss = s.fork();
                     Pointer<Byte> cname = ss.allocateCString(name);
*                    Pointer<?> p = lib.api_func(cname); // this 
resolves the address at runtime, it doesn't, but could take other arguments*
                     ss.close();

                     return new Library.Symbol() {
                         public String getName() {
                             return name;
                         }
                         public Pointer<?> getAddress() {
                             return p;
                         }
                     };
                 });
         }
         }