Where to attach backend builtin decl?

[FX Coudert]

>> If I replace the decl with its backend builtin decl, which has name
>> "__builtin_spu_add_1",later the function is not expanded.
>
> That is weird (and slightly worrying). Can you show me the tree dump
> for the function call, where you have manually replaced the decl by
> the builtin decl?

I was so intrigued that this doesn't work that I have tried it  
myself... and it works! I use the following code:

> module m
> implicit none
>
>   interface
>     function sqrt_builtin (a) result(c) bind(c, name="__builtin_sqrt")
>     use iso_c_binding
>     real(c_double), intent(in), value :: a
>     real(c_double) :: c
>     end function
>   end interface
> end module
>
> program test
>   use m
>   use iso_c_binding
>   real(c_double) :: x
>
>   x = 2
>   x = sqrt_builtin (x)
>   print *, x
> end

and I have made the following crude modification to trans-decl.c to  
substitute the builtin fndecl instead of creating a call to an  
external function, just like I explained in my previous mails:

> Index: trans-decl.c
> ===================================================================
> --- trans-decl.c        (revision 132578)
> +++ trans-decl.c        (working copy)
> @@ -1118,6 +1118,10 @@
>       to know that.  */
>    gcc_assert (!(sym->attr.entry || sym->attr.entry_master));
>
> +  if (sym->attr.is_bind_c == 1
> +      && strncmp (sym->binding_label, "__builtin_", 10) == 0)
> +    return (sym->backend_decl = built_in_decls[BUILT_IN_SQRT]);
> +
>    if (sym->attr.intrinsic)
>      {
>        /* Call the resolution function to get the actual name.   
> This is



Without the patch, compiling fails with "Undefined symbols:  
___builtin_sqrt", but with the patch, both the tree dump (-fdump- 
original-tree) and assembler show it working fine:

[excerpt from the tree dump]
>   x = 2.0e+0;
>   x = __builtin_sqrt (x);

[excerpt from the assembler code generated]
>         movsd   %xmm0, -16(%ebp)
>         movsd   -16(%ebp), %xmm0
>         sqrtsd  %xmm0, %xmm0
>         movsd   %xmm0, -16(%ebp)



Now, to the question of why this fails for you... that I can't say,  
but I hope I have given enough information to help you track it down!

FX


-- 
François-Xavier Coudert
http://www.homepages.ucl.ac.uk/~uccafco/