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. > > 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 <ppa...@redhat.com> > Jakub Jelinek <ja...@redhat.com> > > * 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_pair, va_gc> *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 > >