On Fri, Jan 27, 2023 at 07:42:39AM +0000, Richard Biener wrote: > > 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. > > One could argue the same way for this patch (and instead revert),
Well, this patch is in fact a conditional reversion (revert for C++11/14, add one keyword to 2 declarations otherwise). > I'd say if we tweak this now then tweak it to the maximum extent? > Isn't sth like 'enum unsigned char tree_code_class' now possible? > (and a static assert the enum values all fit, though that would > be diagnosed anyway?) C++11 indeed has enum tree_code_class : unsigned char { tcc_exceptional, ... tcc_expression }; and one indeed gets an error if some enumerator doesn't fit. The problem I see with this is that the type is 8-bit everywhere, which I'd be afraid could cause worse code generation (of course, one would need to try to see how much; e.g. build the compiler unmodified, with the unsigned char array plus explicit casts from the array and finally with unsigned char as underlying type). When passing around enum tree_code_class etc., it is fine if it is 32-bit. And there isn't a way to create an enum with different underlying type but with the same enumerators as in another enum. Perhaps for tree_code_class we could away with the underlying type because it is mostly used in the macros which immediately compare it, in gcc/*.cc just in the following explicitly: expr.cc:get_def_for_expr_class (tree name, enum tree_code_class tclass) fold-const.cc: enum tree_code_class tclass; fold-const.cc: enum tree_code_class tclass = TREE_CODE_CLASS (code); fold-const.cc: enum tree_code_class tclass = TREE_CODE_CLASS (code); fold-const.cc: enum tree_code_class kind = TREE_CODE_CLASS (code); fold-const.cc: enum tree_code_class kind = TREE_CODE_CLASS (code); fold-const.cc: enum tree_code_class kind = TREE_CODE_CLASS (code); fold-const.cc: enum tree_code_class kind = TREE_CODE_CLASS (code); gimple-fold.cc: enum tree_code_class kind = TREE_CODE_CLASS (subcode); print-tree.cc: enum tree_code_class tclass; print-tree.cc: enum tree_code_class tclass; tree.cc: These must correspond to the tree_code_class entries. */ tree.cc:const char *const tree_code_class_strings[] = tree.cc: enum tree_code_class type = TREE_CODE_CLASS (code); tree.cc: enum tree_code_class type = TREE_CODE_CLASS (code); tree.cc:tree_class_check_failed (const_tree node, const enum tree_code_class cl, tree.cc:tree_not_class_check_failed (const_tree node, const enum tree_code_class cl, tree.cc: const enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t)); tree.cc: const enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t)); tree-dump.cc: enum tree_code_class code_class; tree-inline.cc: enum tree_code_class cl = TREE_CODE_CLASS (code); tree-pretty-print.cc: enum tree_code_class tclass; tree-ssa-live.cc: enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t)); tree-ssa-operands.cc: enum tree_code_class codeclass; But as I said, one would need to watch for code generation at least on a couple of common hosts, and while x86_64 should be one of them, it might have bigger effects on others as x86 has byte comparison etc. instructions. > > > 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" > > }; > > Do we need an explicit external definition somewhere when > constant folding isn't possible? > > Otherwise looks good to me. > > Thanks, > Richard. > > > #undef DEFTREECODE > > #undef END_OF_BASE_TREE_CODES > > +#else > > +extern const enum tree_code_class tree_code_type[]; There is one here for the C++11 and C++14 cases. For C++17 and later it isn't needed, constexpr inline enum tree_code_class tree_code_type[] = { ... }; means this is a comdat variable in all TUs which need non-ODR uses of it (tree_code_type[23] evaluates to constant expression, but tree_code_type[x] or &tree_code_type[23] etc. often don't and then the comdat var is emitted and all TUs share one copy of the variable. Jakub