[Bug target/89093] [9 Regression] C++ exception handling clobbers d8 VFP register

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89093

--- Comment #53 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Bernd Edlinger from comment #52)
> I digged a bit, and found a D syntax for the target attribute,
> it is a bit of a complication since D does not have a pre-processor,
> but an empty target attribute does seem to be ignored without warnings.
> 
> 
> --- libphobos/libdruntime/gcc/deh.d	2019-01-01 13:31:55.000000000 +0100
> +++ libphobos/libdruntime/gcc/deh.d	2019-04-17 11:24:24.171579381 +0200
> @@ -28,6 +28,7 @@ import gcc.unwind;
>  import gcc.unwind.pe;
>  import gcc.builtins;
>  import gcc.config;
> +import gcc.attribute;
>  
>  extern(C)
>  {
> @@ -519,10 +520,19 @@ extern(C) void _d_throw(Throwable object
>      terminate("unwind error", __LINE__);
>  }
>  
> +static if (GNU_ARM_EABI_Unwinder)
> +{
> +    enum TARGET_ATTRIBUTE = "general-regs-only";
> +}
> +else
> +{
> +    enum TARGET_ATTRIBUTE = "";
> +}
>  
>  /**
>   * Read and extract information from the LSDA (.gcc_except_table section).
>   */
> +@attribute("target", (TARGET_ATTRIBUTE))
>  _Unwind_Reason_Code scanLSDA(const(ubyte)* lsda, _Unwind_Exception_Class
> exceptionClass,
>                               _Unwind_Action actions, _Unwind_Exception*
> unwindHeader,
>                               _Unwind_Context* context, _Unwind_Word cfa,
> @@ -772,6 +782,7 @@ int actionTableLookup(_Unwind_Action act
>   * Called when the personality function has found neither a cleanup or
> handler.
>   * To support ARM EABI personality routines, that must also unwind the
> stack.
>   */
> +@attribute("target", (TARGET_ATTRIBUTE))
>  _Unwind_Reason_Code CONTINUE_UNWINDING(_Unwind_Exception* unwindHeader,
> _Unwind_Context* context)
>  {
>      static if (GNU_ARM_EABI_Unwinder)
> @@ -814,6 +825,7 @@ else
>  static if (GNU_ARM_EABI_Unwinder)
>  {
>      pragma(mangle, PERSONALITY_FUNCTION)
> +    @attribute("target", (TARGET_ATTRIBUTE))
>      extern(C) _Unwind_Reason_Code gdc_personality(_Unwind_State state,
>                                                    _Unwind_Exception*
> unwindHeader,
>                                                    _Unwind_Context* context)
> @@ -873,6 +885,7 @@ else
>      }
>  }
>  
> +@attribute("target", (TARGET_ATTRIBUTE))
>  private _Unwind_Reason_Code __gdc_personality(_Unwind_Action actions,
>                                                _Unwind_Exception_Class
> exceptionClass,
>                                                _Unwind_Exception*
> unwindHeader,

That is not going to work I'm afraid, many targets don't support target
attribute at all.
default_target_option_valid_attribute_p
will then just complain.
Only i386, rs6000, s390, arm, aarch64 and nios2 backends do support those.
On the other side, given the above, I thought all you want to ensure is that
the attribute is on the personality routine, not on the other ones, and the
gdc_personality definition is in
static if (GNU_ARM_EABI_Unwinder)
{
    pragma(mangle, PERSONALITY_FUNCTION)
    extern(C) _Unwind_Reason_Code gdc_personality(_Unwind_State state,
so can't you just stick @attribute("target", "general-regs-only") to there?