Re: [PowerPC 64]r12 is not updated to GEP when control transferred from virtual thunk function .

[Umesh Kalappa <umesh dot kalappa0 at gmail dot com>]

Thank you Eric for the suggestion and say that we support in the  loader
part ,can you please point on elfv2 reference that says implementation for
this specific case.

~Umesh

On Wed, May 15, 2019, 21:35 Eric Botcazou <ebotcazou@adacore.com> wrote:

> > like above the control  from "_ZThn8_N12Intermediate1vEv" (support
> > function for this pointer update)  is transferred
> > "_ZN12Intermediate1vEv" by b  inst (where its not updating the r12)
> > and in the beginning  of   "_ZN12Intermediate1vEv" we are loading the
> > toc base from r12 (which is incorrect ) ,we are investigating the
> > issue and one way to fix the issue is that make THUNK to update the
> > r12 ,the cal like bctrl  or  load the r12 with the function address in
> > the _ZN12Intermediate1vEv prologue code .
>
> Is that on VxWorks in kernel mode?  If so, the loader doesn't abide by the
> ELFv2 ABI so the simple way out is to disable asm thunks altogether:
>
> #undef TARGET_ASM_CAN_OUTPUT_MI_THUNK
> #define TARGET_ASM_CAN_OUTPUT_MI_THUNK rs6000_can_output_mi_thunk
>
> /* Return true if rs6000_output_mi_thunk would be able to output the
>    assembler code for the thunk function specified by the arguments
>    it is passed, and false otherwise.  */
>
> static bool
> rs6000_can_output_mi_thunk (const_tree, HOST_WIDE_INT, HOST_WIDE_INT,
>                             const_tree)
> {
>   /* The only possible issue is for VxWorks in kernel mode.  */
>   if (!TARGET_VXWORKS || TARGET_VXWORKS_RTP)
>     return true;
>
>   /* The loader neither creates the glue code sequence that loads r12 nor
> uses
>      the local entry point for the sibcall's target in the ELFv2 ABI.  */
>   return DEFAULT_ABI != ABI_ELFv2;
> }
>
> --
> Eric Botcazou
>