use proper DECL_INITIAL for VTV

  Hi.

I am working on the early debug info emission that would benefit from a late
use of asm_put_file. This is last blocker where C++ emits early a section directive
in assemble_vtv_preinit_initializer. We can use a proper DECL_INITIAL for that.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
with --enable-vtable-verify.

Ready to be installed?
Thanks,
Martin

gcc/cp/ChangeLog:

	* vtable-class-hierarchy.cc (vtv_generate_init_routine): Emit
	an artificial variable that would be put into .preinit_array
	section.

gcc/ChangeLog:

	* output.h (assemble_vtv_preinit_initializer): Remove.
	* varasm.cc (assemble_vtv_preinit_initializer): Remove.
---
 gcc/cp/vtable-class-hierarchy.cc | 14 ++++++++++++--
 gcc/output.h                     |  4 ----
 gcc/varasm.cc                    | 17 -----------------
 3 files changed, 12 insertions(+), 23 deletions(-)
  

On 10/13/22 10:25, Martin Li?ka wrote:
> Hi.
> 
> I am working on the early debug info emission that would benefit from a late
> use of asm_put_file. This is last blocker where C++ emits early a section directive
> in assemble_vtv_preinit_initializer. We can use a proper DECL_INITIAL for that.
> 
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> with --enable-vtable-verify.
> 
> Ready to be installed?

OK.

> gcc/cp/ChangeLog:
> 
> 	* vtable-class-hierarchy.cc (vtv_generate_init_routine): Emit
> 	an artificial variable that would be put into .preinit_array
> 	section.
> 
> gcc/ChangeLog:
> 
> 	* output.h (assemble_vtv_preinit_initializer): Remove.
> 	* varasm.cc (assemble_vtv_preinit_initializer): Remove.
> ---
>   gcc/cp/vtable-class-hierarchy.cc | 14 ++++++++++++--
>   gcc/output.h                     |  4 ----
>   gcc/varasm.cc                    | 17 -----------------
>   3 files changed, 12 insertions(+), 23 deletions(-)
> 
> diff --git a/gcc/cp/vtable-class-hierarchy.cc b/gcc/cp/vtable-class-hierarchy.cc
> index 79cb5f8de02..cc1df1ebdb2 100644
> --- a/gcc/cp/vtable-class-hierarchy.cc
> +++ b/gcc/cp/vtable-class-hierarchy.cc
> @@ -1192,8 +1192,18 @@ vtv_generate_init_routine (void)
>         cgraph_node::add_new_function (vtv_fndecl, false);
>   
>         if (flag_vtable_verify == VTV_PREINIT_PRIORITY && !TARGET_PECOFF)
> -        assemble_vtv_preinit_initializer (vtv_fndecl);
> -
> +	{
> +	  tree vtv_var
> +	    = build_decl (BUILTINS_LOCATION, VAR_DECL,
> +			  get_identifier ("__vtv_preinit"),
> +			  build_pointer_type (TREE_TYPE (vtv_fndecl)));
> +	  TREE_STATIC (vtv_var) = 1;
> +	  DECL_ARTIFICIAL (vtv_var) = 1;
> +	  DECL_INITIAL (vtv_var) = build_fold_addr_expr (vtv_fndecl);
> +	  set_decl_section_name (vtv_var, ".preinit_array");
> +
> +	  varpool_node::add (vtv_var);
> +	}
>       }
>     pop_lang_context ();
>   }
> diff --git a/gcc/output.h b/gcc/output.h
> index 6dea630913a..6936bdeeb6c 100644
> --- a/gcc/output.h
> +++ b/gcc/output.h
> @@ -199,10 +199,6 @@ extern void assemble_end_function (tree, const char *);
>      initial value (that will be done by the caller).  */
>   extern void assemble_variable (tree, int, int, int);
>   
> -/* Put the vtable verification constructor initialization function
> -   into the preinit array.  */
> -extern void assemble_vtv_preinit_initializer (tree);
> -
>   /* Assemble everything that is needed for a variable declaration that has
>      no definition in the current translation unit.  */
>   extern void assemble_undefined_decl (tree);
> diff --git a/gcc/varasm.cc b/gcc/varasm.cc
> index 423f3f91af8..a11184584a2 100644
> --- a/gcc/varasm.cc
> +++ b/gcc/varasm.cc
> @@ -2419,23 +2419,6 @@ assemble_variable (tree decl, int top_level ATTRIBUTE_UNUSED,
>       }
>   }
>   
> -
> -/* Given a function declaration (FN_DECL), this function assembles the
> -   function into the .preinit_array section.  */
> -
> -void
> -assemble_vtv_preinit_initializer (tree fn_decl)
> -{
> -  section *sect;
> -  unsigned flags = SECTION_WRITE;
> -  rtx symbol = XEXP (DECL_RTL (fn_decl), 0);
> -
> -  flags |= SECTION_NOTYPE;
> -  sect = get_section (".preinit_array", flags, fn_decl);
> -  switch_to_section (sect);
> -  assemble_addr_to_section (symbol, sect);
> -}
> -
>   /* Return 1 if type TYPE contains any pointers.  */
>   
>   static int