[This is a re-send of my previous e-mail; my apologies, yet again, for the e-mail mangling on my end. Those responsible have been sacked.]
With the introduction of the variadic templates patch, we now have more than 255 tree codes in GCC. This causes the mainline Objective-C++ compiler to fail to build: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31134 We've known for a long time that we would eventually hit the limit on the number of tree codes in GCC, and the variadic templates patch happened to win the 8-bit tree-code lottery. Reverting the variadic templates patch is not a solution: we'll hit this limit again, and next time it will be with a feature that you find crucial. Reducing the number of tree codes we use also seems infeasible: combining two somewhat-similar entities into a single tree code is a short-term fix with long-term problems, including poor readability and a greater likelihood of bugs. We need more tree codes. With GCC's current structure, that means increasing the number of bits allocated for tree codes in the tree_base struct. This will increase GCC's memory footprint. It's unfortunate, but is it avoidable? I suspect it is not, without a major restructuring of the compiler. The patch below makes the CODE field of the tree_base struct 16 bits, and adds suitable padding to fill out a 32-bit word. Elsewhere, the limit on tree codes is raised to 512. Tested i686-pc-linux-gnu; no regressions with C, C++, Objective C, Objective-C++, or Java. Note: I've also sent this to gcc-patches, because there is a patch in it. However, let's keep the discussion on [EMAIL PROTECTED] Cheers, Doug :ADDPATCH C: 2007-03-12 Douglas Gregor <[EMAIL PROTECTED]> * tree.c (tree_contains_struct): Permit 512 tree codes. * tree.h (tree_contains_struct): Ditto. (MAX_TREE_CODES): Ditto. (struct tree_base): Make CODE 16 bits, instead of 8 bits. Add SPARE member to store remaining padding bits. Index: tree.c =================================================================== --- tree.c (revision 122840) +++ tree.c (working copy) @@ -168,7 +168,7 @@ static unsigned int attribute_hash_list tree global_trees[TI_MAX]; tree integer_types[itk_none]; -unsigned char tree_contains_struct[256][64]; +unsigned char tree_contains_struct[512][64]; /* Number of operands for each OpenMP clause. */ unsigned const char omp_clause_num_ops[] = Index: tree.h =================================================================== --- tree.h (revision 122840) +++ tree.h (working copy) @@ -41,7 +41,7 @@ enum tree_code { #undef DEFTREECODE -extern unsigned char tree_contains_struct[256][64]; +extern unsigned char tree_contains_struct[512][64]; #define CODE_CONTAINS_STRUCT(CODE, STRUCT) (tree_contains_struct[(CODE)][(STRUCT)]) /* Number of language-independent tree codes. */ @@ -80,7 +80,7 @@ extern const char *const tree_code_class #define TREE_CODE_CLASS_STRING(CLASS)\ tree_code_class_strings[(int) (CLASS)] -#define MAX_TREE_CODES 256 +#define MAX_TREE_CODES 512 extern const enum tree_code_class tree_code_type[]; #define TREE_CODE_CLASS(CODE) tree_code_type[(int) (CODE)] @@ -363,7 +363,7 @@ union tree_ann_d; struct tree_base GTY(()) { - ENUM_BITFIELD(tree_code) code : 8; + ENUM_BITFIELD(tree_code) code : 16; unsigned side_effects_flag : 1; unsigned constant_flag : 1; @@ -392,6 +392,8 @@ struct tree_base GTY(()) unsigned lang_flag_6 : 1; unsigned visited : 1; + unsigned spare : 24; + /* FIXME tuples: Eventually, we need to move this somewhere external to the trees. */ union tree_ann_d *ann;
