Patch ping - [PATCH] tree: Use comdat tree_code_{type,length} even for C++11/14 [PR108634]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

I'd like to ping this patch, which has been successfully
bootstrapped/regtested on x86_64-linux and i686-linux:

https://gcc.gnu.org/pipermail/gcc-patches/2023-February/611180.html
  - PR108634 - P3 - tree: Use comdat tree_code_{type,length} even for C++11/14

Thanks
	Jakub

On Thu, Feb 02, 2023 at 03:30:29PM +0100, Jakub Jelinek via Gcc-patches wrote:
> The recent change to undo the tree_code_type/tree_code_length
> excessive duplication apparently broke building the Linux kernel
> plugin.  While it is certainly desirable that GCC plugins are built
> with the same compiler as GCC has been built and with the same options
> (at least the important ones), it might be hard to arrange that,
> e.g. if gcc is built using a cross-compiler but the plugin then built
> natively, or GCC isn't bootstrapped for other reasons, or just as in
> the kernel case they were building the plugin with -std=gnu++11 while
> the bootstrapped GCC has been built without any such option and so with
> whatever the compiler defaulted to.
> 
> For C++17 and later tree_code_{type,length} are UNIQUE symbols with
> those assembler names, while for C++11/14 they were
> _ZL14tree_code_type and _ZL16tree_code_length.
> 
> The following patch uses a comdat var for those even for C++11/14
> as suggested by Maciej Cencora.  Relying on weak attribute is not an
> option because not all hosts support it and there are non-GNU system
> compilers.  While we could use it unconditionally,
> I think defining a template just to make it comdat is weird, and
> the compiler itself is always built with the same compiler.
> Plugins, being separate shared libraries, will have a separate copy of
> the arrays if they are ODR-used in the plugin, so there is not a big
> deal if e.g. cc1plus uses tree_code_type while plugin uses
> _ZN19tree_code_type_tmplILi0EE14tree_code_typeE or vice versa.
> 
> Tested in non-bootstrapped build with both -std=gnu++17 and -std=gnu++11,
> ok for trunk if it passes full bootstrap/regtest?
> 
> 2023-02-02  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR plugins/108634
> 	* tree-core.h (tree_code_type, tree_code_length): For C++11 or
> 	C++14, don't declare as extern const arrays.
> 	(tree_code_type_tmpl, tree_code_length_tmpl): New types with
> 	static constexpr member arrays for C++11 or C++14.
> 	* tree.h (TREE_CODE_CLASS): For C++11 or C++14 use
> 	tree_code_type_tmpl <0>::tree_code_type instead of tree_code_type.
> 	(TREE_CODE_LENGTH): For C++11 or C++14 use
> 	tree_code_length_tmpl <0>::tree_code_length instead of
> 	tree_code_length.
> 	* tree.cc (tree_code_type, tree_code_length): Remove.
> 
> --- gcc/tree-core.h.jj	2023-01-27 10:51:27.575399052 +0100
> +++ gcc/tree-core.h	2023-02-02 15:06:05.048665279 +0100
> @@ -2285,19 +2285,27 @@ struct floatn_type_info {
>  extern bool tree_contains_struct[MAX_TREE_CODES][64];
>  
>  /* Class of tree given its code.  */
> -#if __cpp_inline_variables >= 201606L
>  #define DEFTREECODE(SYM, NAME, TYPE, LENGTH) TYPE,
>  #define END_OF_BASE_TREE_CODES tcc_exceptional,
>  
> +#if __cpp_inline_variables < 201606L
> +template <int N>
> +struct tree_code_type_tmpl {
> +  static constexpr enum tree_code_class tree_code_type[] = {
> +#include "all-tree.def"
> +  };
> +};
> +
> +template <int N>
> +constexpr enum tree_code_class tree_code_type_tmpl<N>::tree_code_type[];
> +#else
>  constexpr inline enum tree_code_class tree_code_type[] = {
>  #include "all-tree.def"
>  };
> +#endif
>  
>  #undef DEFTREECODE
>  #undef END_OF_BASE_TREE_CODES
> -#else
> -extern const enum tree_code_class tree_code_type[];
> -#endif
>  
>  /* Each tree code class has an associated string representation.
>     These must correspond to the tree_code_class entries.  */
> @@ -2305,18 +2313,27 @@ extern const char *const tree_code_class
>  
>  /* Number of argument-words in each kind of tree-node.  */
>  
> -#if __cpp_inline_variables >= 201606L
>  #define DEFTREECODE(SYM, NAME, TYPE, LENGTH) LENGTH,
>  #define END_OF_BASE_TREE_CODES 0,
> +
> +#if __cpp_inline_variables < 201606L
> +template <int N>
> +struct tree_code_length_tmpl {
> +  static constexpr unsigned char tree_code_length[] = {
> +#include "all-tree.def"
> +  };
> +};
> +
> +template <int N>
> +constexpr unsigned char tree_code_length_tmpl<N>::tree_code_length[];
> +#else
>  constexpr inline unsigned char tree_code_length[] = {
>  #include "all-tree.def"
>  };
> +#endif
>  
>  #undef DEFTREECODE
>  #undef END_OF_BASE_TREE_CODES
> -#else
> -extern const unsigned char tree_code_length[];
> -#endif
>  
>  /* Vector of all alias pairs for global symbols.  */
>  extern GTY(()) vec<alias_pair, va_gc> *alias_pairs;
> --- gcc/tree.h.jj	2023-01-27 20:09:16.183970583 +0100
> +++ gcc/tree.h	2023-02-02 14:37:17.255004291 +0100
> @@ -177,7 +177,12 @@ code_helper::is_builtin_fn () const
>  #define TREE_CODE_CLASS_STRING(CLASS)\
>          tree_code_class_strings[(int) (CLASS)]
>  
> +#if __cpp_inline_variables < 201606L
> +#define TREE_CODE_CLASS(CODE)	\
> +  tree_code_type_tmpl <0>::tree_code_type[(int) (CODE)]
> +#else
>  #define TREE_CODE_CLASS(CODE)	tree_code_type[(int) (CODE)]
> +#endif
>  
>  /* Nonzero if NODE represents an exceptional code.  */
>  
> @@ -271,7 +276,12 @@ code_helper::is_builtin_fn () const
>  
>  #define EXPR_P(NODE) IS_EXPR_CODE_CLASS (TREE_CODE_CLASS (TREE_CODE (NODE)))
>  
> +#if __cpp_inline_variables < 201606L
> +#define TREE_CODE_LENGTH(CODE)	\
> +  tree_code_length_tmpl <0>::tree_code_length[(int) (CODE)]
> +#else
>  #define TREE_CODE_LENGTH(CODE)	tree_code_length[(int) (CODE)]
> +#endif
>  
>  
>  /* Helper macros for math builtins.  */
> --- gcc/tree.cc.jj	2023-02-02 10:54:44.302473853 +0100
> +++ gcc/tree.cc	2023-02-02 14:20:58.712251654 +0100
> @@ -74,34 +74,6 @@ along with GCC; see the file COPYING3.
>  #include "asan.h"
>  #include "ubsan.h"
>  
> -#if __cpp_inline_variables < 201606L
> -/* Tree code classes.  */
> -
> -#define DEFTREECODE(SYM, NAME, TYPE, LENGTH) TYPE,
> -#define END_OF_BASE_TREE_CODES tcc_exceptional,
> -
> -const enum tree_code_class tree_code_type[] = {
> -#include "all-tree.def"
> -};
> -
> -#undef DEFTREECODE
> -#undef END_OF_BASE_TREE_CODES
> -
> -/* Table indexed by tree code giving number of expression
> -   operands beyond the fixed part of the node structure.
> -   Not used for types or decls.  */
> -
> -#define DEFTREECODE(SYM, NAME, TYPE, LENGTH) LENGTH,
> -#define END_OF_BASE_TREE_CODES 0,
> -
> -const unsigned char tree_code_length[] = {
> -#include "all-tree.def"
> -};
> -
> -#undef DEFTREECODE
> -#undef END_OF_BASE_TREE_CODES
> -#endif
> -
>  /* Names of tree components.
>     Used for printing out the tree and error messages.  */
>  #define DEFTREECODE(SYM, NAME, TYPE, LEN) NAME,