Is RegisterMap updated?

[David Griffiths]

Oops, ignore that last message!

On Tue, 29 Jan 2019 at 15:41, David Griffiths <david.griffiths at gmail.com> wrote:
>
> Oh, I'm looking at the jdk8u code which has the following code commented out:
>
>     /*
>     if (map.getUpdateMap()) {
>       // Tell GC to use argument oopmaps for some runtime stubs that need it.
>       // For C1, the runtime stub might not have oop maps, so set this flag
>       // outside of update_register_map.
>       map.setIncludeArgumentOops(cb.callerMustGCArguments());
>
>       if (cb.getOopMaps() != null) {
>         OopMapSet.updateRegisterMap(this, cb, map, true);
>       }
>
>       // Since the prolog does the save and restore of EBP there is no oopmap
>       // for it so we must fill in its location as if there was an oopmap entry
>       // since if our caller was compiled code there could be live jvm
> state in it.
>       updateMapWithSavedLink(map, savedFPAddr);
>     }
>     */
>
> I see that is no longer commented out in jdk9 so maybe that's the
> cause. (There is nothing else that calls setLocation).
>
> Cheers,
>
> David
>
> On Tue, 29 Jan 2019 at 13:41, Andrew Haley <aph at redhat.com> wrote:
> >
> > On 1/29/19 11:24 AM, David Griffiths wrote:
> > > Hi, in CompiledVFrame.createStackValue there is the following code:
> > >
> > >       // First find address of value
> > >       Address valueAddr = loc.isRegister()
> > >         // Value was in a callee-save register
> > >         ? getRegisterMap().getLocation(new VMReg(loc.getRegisterNumber()))
> > >         // Else value was directly saved on the stack. The frame's
> > > original stack pointer,
> > >         // before any extension by its callee (due to Compiler1
> > > linkage on SPARC), must be used.
> > >         : ((Address)fr.getUnextendedSP()).addOffsetTo(loc.getStackOffset());
> > >
> > > It appears from what I can make out that for the register case the map
> > > is not updated and so valueAddr is null. The only thing I can see that
> > > calls setLocation is updateMapWithSavedLink. Seems like it should be
> > > possible to return the register value for the frame at the top of the
> > > stack though?
> >
> > It could be, but we don't do that. The registers in the map are those
> > pushed onto the stack by generated Java code.
> >
> > --
> > Andrew Haley
> > Java Platform Lead Engineer
> > Red Hat UK Ltd. <https://www.redhat.com>
> > EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671