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[69.118.112.187]) by smtp.gmail.com with ESMTPSA id o25-20020ac84299000000b003b8238114d9sm865306qtl.12.2023.01.27.04.40.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Jan 2023 04:40:38 -0800 (PST) From: Patrick Palka X-Google-Original-From: Patrick Palka Date: Fri, 27 Jan 2023 07:40:37 -0500 (EST) To: Patrick Palka cc: Jakub Jelinek , Richard Biener , Jeff Law , Andrew Pinski , gcc-patches@gcc.gnu.org Subject: Re: [PATCH] tree: Fix up tree_code_{length,type} In-Reply-To: Message-ID: <5461bdac-a26e-8988-3fdb-0dbc0e748ccb@idea> References: <1668794731-9349-1-git-send-email-apinski@marvell.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Thu, 26 Jan 2023, Patrick Palka wrote: > On Thu, 26 Jan 2023, Jakub Jelinek wrote: > > > On Thu, Jan 26, 2023 at 09:45:35AM -0500, Patrick Palka via Gcc-patches wrote: > > > > +#define DEFTREECODE(SYM, NAME, TYPE, LENGTH) TYPE, > > > > +#define END_OF_BASE_TREE_CODES tcc_exceptional, > > > > + > > > > + > > > > /* Class of tree given its code. */ > > > > -extern const enum tree_code_class tree_code_type[]; > > > > +constexpr enum tree_code_class tree_code_type[] = { > > > > +#include "all-tree.def" > > > > +}; > > > > + > > > > +#undef DEFTREECODE > > > > +#undef END_OF_BASE_TREE_CODES > > > > > > > > /* Each tree code class has an associated string representation. > > > > These must correspond to the tree_code_class entries. */ > > > > extern const char *const tree_code_class_strings[]; > > > > > > > > /* Number of argument-words in each kind of tree-node. */ > > > > -extern const unsigned char tree_code_length[]; > > > > + > > > > +#define DEFTREECODE(SYM, NAME, TYPE, LENGTH) LENGTH, > > > > +#define END_OF_BASE_TREE_CODES 0, > > > > +constexpr unsigned char tree_code_length[] = { > > > > +#include "all-tree.def" > > > > +}; > > > > + > > > > +#undef DEFTREECODE > > > > +#undef END_OF_BASE_TREE_CODES > > > > > > IIUC defining these globals as non-inline constexpr gives them internal > > > linkage, and so each TU contains its own unique copy of these globals. > > > This bloats cc1plus by a tiny bit and is technically an ODR violation > > > because some inline functions such as tree_class_check also ODR-use > > > these variables and so each defn of tree_class_check will refer to a > > > "different" tree_code_class. Since inline variables are a C++17 > > > feature, I guess we could fix this by defining the globals the old way > > > before C++17 and as inline constexpr otherwise? > > > > And I'd argue with the tiny bit. > > In my x86_64-linux cc1plus from today, I see 193 _ZL16tree_code_length vars, > > 374 bytes each, and 324 _ZL14tree_code_type vars, 1496 bytes each. > > So, that means waste of 555016 .rodata bytes, plus being highly non-cache > > friendly. > > > > The following patch does that. > > > > So far tested on x86_64-linux in my -O0 working tree (system gcc 12 > > compiler) where .rodata shrunk with the patch by 928896 bytes, in last > > stage of a bootstrapped tree (built by today's prev-gcc) where .rodata > > shrunk by 561728 bytes (in neither case .text or most other sections > > changed sizes) and on powerpc64le-linux --disable-bootstrap > > (system gcc 4.8.5) to test also the non-C++17 case. > > LGTM FWIW. On a related note I noticed the function > tree.h:tree_operand_length is declared static and is then used in the > non-static inline functions tree_operand_check etc, which seems to be > also be a (harmless) ODR violation? > > We probably should do s/static inline/inline throughout the header files > at some point, which'd hopefully reduce the size of and speed up stage1 > cc1plus. Mechanically replacing uses of static inline in headers via echo gcc/*.h gcc/*/*.h | xargs sed -i 's/^static inline/inline/g' reduces rodata size of stage1 cc1plus by ~1.5MB and seems to make it ~2% faster. Not bad.. > > > > > Ok for trunk if it passes full bootstrap/regtest? > > > > BTW, wonder if tree_code_type couldn't be an array of unsigned char > > elements rather than enum tree_code_class and we'd then cast it > > to the enum in the macro, that would shrink that array from 1496 bytes > > to 374. Of course, that sounds like stage1 material. > > > > 2023-01-26 Patrick Palka > > Jakub Jelinek > > > > * tree-core.h (tree_code_type, tree_code_length): For > > C++17 and later, add inline keyword, otherwise don't define > > the arrays, but declare extern arrays. > > * tree.cc (tree_code_type, tree_code_length): Define these > > arrays for C++14 and older. > > > > --- gcc/tree-core.h.jj 2023-01-02 09:32:31.188158094 +0100 > > +++ gcc/tree-core.h 2023-01-26 16:02:34.212113251 +0100 > > @@ -2284,17 +2284,20 @@ struct floatn_type_info { > > /* Matrix describing the structures contained in a given tree code. */ > > 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, > > > > - > > -/* Class of tree given its code. */ > > -constexpr enum tree_code_class tree_code_type[] = { > > +constexpr inline enum tree_code_class tree_code_type[] = { > > #include "all-tree.def" > > }; > > > > #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. */ > > @@ -2302,14 +2305,18 @@ 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, > > -constexpr unsigned char tree_code_length[] = { > > +constexpr inline unsigned char tree_code_length[] = { > > #include "all-tree.def" > > }; > > > > #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_pairs; > > --- gcc/tree.cc.jj 2023-01-13 17:37:45.259482663 +0100 > > +++ gcc/tree.cc 2023-01-26 16:03:59.796878082 +0100 > > @@ -74,7 +74,33 @@ 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. */ > > > > Jakub > > > > >