[Bug target/126438] [17 Regression] Building cross-compiler to powerpc64-apple-darwin9 fails since r17-2606-g2c421a5cbe9d2b

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126438

--- Comment #2 from Avinash Jayakar <avinashd at gcc dot gnu.org> ---
The build succeeds with the (In reply to Avinash Jayakar from comment #1)
> I see that the REGISTER_NAMES macro is defined separately for darwin.h as
> the assembler for darwin expects the register names differently. 
> 
> This should be the minimal fix to get a successful build.
> 
> diff --git a/gcc/config/rs6000/darwin.h b/gcc/config/rs6000/darwin.h
> index 175b6b1c3e0..8614052d8ca 100644
> --- a/gcc/config/rs6000/darwin.h
> +++ b/gcc/config/rs6000/darwin.h
> @@ -295,7 +295,9 @@
>    /* cr0..cr7 */                                                       \
>      "cr0", "cr1", "cr2", "cr3", "cr4", "cr5", "cr6", "cr7",            \
>    /* vrsave vscr sfp */                                                    
> \
> -    "vrsave", "vscr", "sfp"                                            \
> +    "vrsave", "vscr", "sfp",                                           \
> +  /* DMRs */                                                           \
> +      "dm0", "dm1", "dm2", "dm3", "dm4", "dm5", "dm6", "dm7"   \
>  }
>  
>  /* This outputs NAME to FILE.  */

The build succeeds with this change. But I am not sure on how to test it for
the darwin platform. Some help would be appreciated.