Re: [C++ patch] Move FINAL flag to middle-end trees.

[Gabriel Dos Reis <gdr at integrable-solutions dot net>]

On Sun, Aug 25, 2013 at 10:38 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> On 08/24/2013 05:18 AM, Jan Hubicka wrote:
>> >In the next step I would like to introduce the DECL_CPP_CONSTRUCTOR/DESTRUCTOR macro.
>> >The catch I run into is that these flags are tested on TEMPLATE_DECL so the middle-end
>> >macro bombs on type checking.  I wonder what is best approach here.
>>
>> I think fix the front end to use STRIP_TEMPLATE to make sure we're
>> checking/setting the flag on a FUNCTION_DECL.
>
> Thank you!
> I did not know the FUNCTION_DECLs are already there.  The following patch seems
> to work.  Of course if it seems cleaner, I can update the users of the CPP
> macros into the expanded variants.  I want to have CPP in name in middle-end to
> signify that we actually understand language specific properties of these
> functions (so constructors/destructors in other languages probably don't
> want to do that).
>
> Bootstrapped/regtested ppc64-linux, OK?
>
>         * tree.h (tree_decl_with_vis): Add cpp_constructor and cpp_destructor.
>         (DECL_CPP_CONSTRUCTOR_P, DECL_CPP_DESTRUCTOR_P): New macros.
>
>         * cp-tree.h (DECL_CONSTRUCTOR_P, DECL_DESTRUCTOR_P): Change to
>         strip templates and set the middle-end flag.
> Index: tree.h
> ===================================================================
> --- tree.h      (revision 201977)
> +++ tree.h      (working copy)
> @@ -3232,8 +3232,12 @@ struct GTY(()) tree_decl_with_vis {
>   /* Used by C++ only.  Might become a generic decl flag.  */
>   unsigned shadowed_for_var_p : 1;
>   /* Belong to FUNCTION_DECL exclusively.  */
> + unsigned cpp_constructor : 1;
> + /* Belong to FUNCTION_DECL exclusively.  */
> + unsigned cpp_destructor : 1;
> + /* Belong to FUNCTION_DECL exclusively.  */

Naming suggestion:  we already use cpp_ as prefix for the C preprocessor.
Could we please not use it for C++, given that tree is used by so
many clients for just about anything.   cxx_ is a good alternative.

>   unsigned final : 1;
> - /* 13 unused bits. */
> + /* 11 unused bits. */
>  };
>
>  extern tree decl_debug_expr_lookup (tree);
> @@ -3483,6 +3487,18 @@ extern vec<tree, va_gc> **decl_debug_arg
>  #define DECL_FUNCTION_VERSIONED(NODE)\
>     (FUNCTION_DECL_CHECK (NODE)->function_decl.versioned_function)
>
> +/* In FUNCTION_DECL, this is set if this function is a C++ constructor.
> +   Devirtualization machinery uses this knowledge for determing type of the
> +   object constructed.  Also we assume that constructor address is not
> +   important.  */
> +#define DECL_CPP_CONSTRUCTOR_P(NODE)\

Same here.

> +   (FUNCTION_DECL_CHECK (NODE)->decl_with_vis.cpp_constructor)
> +
> +/* In FUNCTION_DECL, this is set if this function is a C++ destructor.
> +   Devirtualization machinery uses this to track types in destruction.  */
> +#define DECL_CPP_DESTRUCTOR_P(NODE)\
> +   (FUNCTION_DECL_CHECK (NODE)->decl_with_vis.cpp_destructor)
> +

Likewise.

>  /* In FUNCTION_DECL that represent an virtual method this is set when
>     the method is final.  */
>  #define DECL_FINAL_P(NODE)\
> Index: cp/cp-tree.h
> ===================================================================
> --- cp/cp-tree.h        (revision 201977)
> +++ cp/cp-tree.h        (working copy)
> @@ -2121,9 +2121,10 @@ struct GTY((variable_size)) lang_decl {
>  #define SET_DECL_LANGUAGE(NODE, LANGUAGE) \
>    (DECL_LANG_SPECIFIC (NODE)->u.base.language = (LANGUAGE))
>
> -/* For FUNCTION_DECLs: nonzero means that this function is a constructor.  */
> +/* For FUNCTION_DECLs and TEMPLATE_DECLs: nonzero means that this function
> +   is a constructor.  */
>  #define DECL_CONSTRUCTOR_P(NODE) \
> -  (LANG_DECL_FN_CHECK (NODE)->constructor_attr)
> +  DECL_CPP_CONSTRUCTOR_P (STRIP_TEMPLATE (NODE))
>
>  /* Nonzero if NODE (a FUNCTION_DECL) is a constructor for a complete
>     object.  */
> @@ -2152,9 +2153,10 @@ struct GTY((variable_size)) lang_decl {
>  #define DECL_MOVE_CONSTRUCTOR_P(NODE) \
>    (DECL_CONSTRUCTOR_P (NODE) && move_fn_p (NODE))
>
> -/* Nonzero if NODE is a destructor.  */
> +/* Nonzero if NODE (a FUNCTION_DECL or TEMPLATE_DECL)
> +   is a destructor.  */
>  #define DECL_DESTRUCTOR_P(NODE)                                \
> -  (LANG_DECL_FN_CHECK (NODE)->destructor_attr)
> +  DECL_CPP_DESTRUCTOR_P (STRIP_TEMPLATE (NODE))
>
>  /* Nonzero if NODE (a FUNCTION_DECL) is a destructor, but not the
>     specialized in-charge constructor, in-charge deleting constructor,