On Sun, 15 Oct 2023, Ken Matsui wrote:
> Since RID_MAX soon reaches 255 and all built-in traits are used approximately
> once in a C++ translation unit, this patch removes all RID values for built-in
> traits and uses the identifier node to look up the specific trait. Rather
> than holding traits as keywords, we set all trait identifiers as cik_trait,
> which is a new cp_identifier_kind. As cik_reserved_for_udlit was unused and
> cp_identifier_kind is 3 bits, we replaced the unused field with the new
> cik_trait. Also, the later patch handles a subsequent token to the built-in
> identifier so that we accept the use of non-function-like built-in trait
> identifiers.
Thanks, this looks great! Some review comments below.
>
> gcc/c-family/ChangeLog:
>
> * c-common.cc (c_common_reswords): Remove all mappings of
> built-in traits.
> * c-common.h (enum rid): Remove all RID values for built-in traits.
>
> gcc/cp/ChangeLog:
>
> * cp-objcp-common.cc (names_builtin_p): Remove all RID value
> cases for built-in traits. Check for built-in traits via
> the new cik_trait kind.
> * cp-tree.h (enum cp_trait_kind): Set its underlying type to
> addr_space_t.
> (struct cp_trait): New struct to hold trait information.
> (cp_traits): New array to hold a mapping to all traits.
> (cik_reserved_for_udlit): Rename to ...
> (cik_trait): ... this.
> (IDENTIFIER_ANY_OP_P): Exclude cik_trait.
> (IDENTIFIER_TRAIT_P): New macro to detect cik_trait.
> * lex.cc (init_cp_traits): New function to set cik_trait for all
> built-in trait identifiers.
We should mention setting IDENTIFIER_CP_INDEX as well.
> (cxx_init): Call init_cp_traits function.
> * parser.cc (cp_traits): Define its values, declared in cp-tree.h.
> (cp_lexer_lookup_trait): New function to look up a
> built-in trait by IDENTIFIER_CP_INDEX.
> (cp_lexer_lookup_trait_expr): Likewise, look up an
> expression-yielding built-in trait.
> (cp_lexer_lookup_trait_type): Likewise, look up a type-yielding
> built-in trait.
> (cp_keyword_starts_decl_specifier_p): Remove all RID value cases
> for built-in traits.
> (cp_lexer_next_token_is_decl_specifier_keyword): Handle
> type-yielding built-in traits.
> (cp_parser_primary_expression): Remove all RID value cases for
> built-in traits. Handle expression-yielding built-in traits.
> (cp_parser_trait): Handle cp_trait instead of enum rid.
> (cp_parser_simple_type_specifier): Remove all RID value cases
> for built-in traits. Handle type-yielding built-in traits.
>
> Co-authored-by: Patrick Palka <ppa...@redhat.com>
> Signed-off-by: Ken Matsui <kmat...@gcc.gnu.org>
> ---
> gcc/c-family/c-common.cc | 7 --
> gcc/c-family/c-common.h | 5 --
> gcc/cp/cp-objcp-common.cc | 8 +--
> gcc/cp/cp-tree.h | 31 ++++++---
> gcc/cp/lex.cc | 21 ++++++
> gcc/cp/parser.cc | 141 ++++++++++++++++++++++++--------------
> 6 files changed, 139 insertions(+), 74 deletions(-)
>
> diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
> index f044db5b797..21fd333ef57 100644
> --- a/gcc/c-family/c-common.cc
> +++ b/gcc/c-family/c-common.cc
> @@ -508,13 +508,6 @@ const struct c_common_resword c_common_reswords[] =
> { "wchar_t", RID_WCHAR, D_CXXONLY },
> { "while", RID_WHILE, 0 },
>
> -#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> - { NAME, RID_##CODE, D_CXXONLY },
> -#include "cp/cp-trait.def"
> -#undef DEFTRAIT
> - /* An alias for __is_same. */
> - { "__is_same_as", RID_IS_SAME, D_CXXONLY },
> -
> /* C++ transactional memory. */
> { "synchronized", RID_SYNCHRONIZED, D_CXX_OBJC | D_TRANSMEM },
> { "atomic_noexcept", RID_ATOMIC_NOEXCEPT, D_CXXONLY | D_TRANSMEM },
> diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
> index 1fdba7ef3ea..051a442e0f4 100644
> --- a/gcc/c-family/c-common.h
> +++ b/gcc/c-family/c-common.h
> @@ -168,11 +168,6 @@ enum rid
> RID_BUILTIN_LAUNDER,
> RID_BUILTIN_BIT_CAST,
>
> -#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> - RID_##CODE,
> -#include "cp/cp-trait.def"
> -#undef DEFTRAIT
> -
> /* C++11 */
> RID_CONSTEXPR, RID_DECLTYPE, RID_NOEXCEPT, RID_NULLPTR, RID_STATIC_ASSERT,
>
> diff --git a/gcc/cp/cp-objcp-common.cc b/gcc/cp/cp-objcp-common.cc
> index 93b027b80ce..b1adacfec07 100644
> --- a/gcc/cp/cp-objcp-common.cc
> +++ b/gcc/cp/cp-objcp-common.cc
> @@ -421,6 +421,10 @@ names_builtin_p (const char *name)
> }
> }
>
> + /* Check for built-in traits. */
> + if (IDENTIFIER_TRAIT_P (id))
> + return true;
> +
> /* Also detect common reserved C++ words that aren't strictly built-in
> functions. */
> switch (C_RID_CODE (id))
> @@ -434,10 +438,6 @@ names_builtin_p (const char *name)
> case RID_BUILTIN_ASSOC_BARRIER:
> case RID_BUILTIN_BIT_CAST:
> case RID_OFFSETOF:
> -#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> - case RID_##CODE:
> -#include "cp-trait.def"
> -#undef DEFTRAIT
> return true;
> default:
> break;
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 6e34952da99..583abb2e79a 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -1226,7 +1226,7 @@ enum cp_identifier_kind {
> cik_simple_op = 4, /* Non-assignment operator name. */
> cik_assign_op = 5, /* An assignment operator name. */
> cik_conv_op = 6, /* Conversion operator name. */
> - cik_reserved_for_udlit = 7, /* Not yet in use */
> + cik_trait = 7, /* Built-in trait name. */
> cik_max
> };
>
> @@ -1271,9 +1271,9 @@ enum cp_identifier_kind {
> & IDENTIFIER_KIND_BIT_0 (NODE))
>
> /* True if this identifier is for any operator name (including
> - conversions). Value 4, 5, 6 or 7. */
> + conversions). Value 4, 5, or 6. */
> #define IDENTIFIER_ANY_OP_P(NODE) \
> - (IDENTIFIER_KIND_BIT_2 (NODE))
> + (IDENTIFIER_KIND_BIT_2 (NODE) && !IDENTIFIER_TRAIT_P (NODE))
>
> /* True if this identifier is for an overloaded operator. Values 4, 5. */
> #define IDENTIFIER_OVL_OP_P(NODE) \
> @@ -1286,12 +1286,18 @@ enum cp_identifier_kind {
> & IDENTIFIER_KIND_BIT_0 (NODE))
>
> /* True if this identifier is the name of a type-conversion
> - operator. Value 7. */
> + operator. Value 6. */
> #define IDENTIFIER_CONV_OP_P(NODE) \
> (IDENTIFIER_ANY_OP_P (NODE) \
> & IDENTIFIER_KIND_BIT_1 (NODE) \
> & (!IDENTIFIER_KIND_BIT_0 (NODE)))
>
> +/* True if this identifier is the name of a built-in trait. */
> +#define IDENTIFIER_TRAIT_P(NODE) \
> + (IDENTIFIER_KIND_BIT_0 (NODE) \
> + && IDENTIFIER_KIND_BIT_1 (NODE) \
> + && IDENTIFIER_KIND_BIT_2 (NODE))
> +
> /* True if this identifier is a new or delete operator. */
> #define IDENTIFIER_NEWDEL_OP_P(NODE) \
> (IDENTIFIER_OVL_OP_P (NODE) \
> @@ -1375,16 +1381,25 @@ struct GTY (()) tree_argument_pack_select {
> int index;
> };
>
> -/* The different kinds of traits that we encounter. */
> -
> -enum cp_trait_kind
> -{
> +/* The different kinds of traits that we encounter. The size is limited to
> + addr_space_t since a trait is looked up by IDENTIFIER_CP_INDEX. */
> +enum cp_trait_kind : addr_space_t {
> #define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> CPTK_##CODE,
> #include "cp-trait.def"
> #undef DEFTRAIT
> };
>
> +/* The trait type. */
> +struct cp_trait {
> + short arity;
> + cp_trait_kind kind;
> + bool type;
Could we also store the const char* name of each trait here, so that ...
> +};
> +
> +/* The trait table. */
> +extern const struct cp_trait cp_traits[];
> +
> /* The types that we are processing. */
> #define TRAIT_EXPR_TYPE1(NODE) \
> (((struct tree_trait_expr *)TRAIT_EXPR_CHECK (NODE))->type1)
> diff --git a/gcc/cp/lex.cc b/gcc/cp/lex.cc
> index 64bcfb18196..16a82a12a02 100644
> --- a/gcc/cp/lex.cc
> +++ b/gcc/cp/lex.cc
> @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3. If not see
> #include "langhooks.h"
>
> static int interface_strcmp (const char *);
> +static void init_cp_traits (void);
> static void init_cp_pragma (void);
>
> static tree parse_strconst_pragma (const char *, int);
> @@ -283,6 +284,25 @@ init_reswords (void)
> }
> }
>
> +/* Initialize the C++ traits. */
> +static void
> +init_cp_traits (void)
> +{
> + tree id;
> +
> +#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> + id = get_identifier (NAME); \
> + IDENTIFIER_CP_INDEX (id) = CPTK_##CODE; \
> + set_identifier_kind (id, cik_trait);
> +#include "cp/cp-trait.def"
> +#undef DEFTRAIT
... we could replace this straight-line code with a loop over cp_traits?
It'd make cp_traits bigger but init_cp_traits should get much smaller,
which should be a net win in terms of binary size.
> +
> + /* An alias for __is_same. */
> + id = get_identifier ("__is_same_as");
> + IDENTIFIER_CP_INDEX (id) = CPTK_IS_SAME;
> + set_identifier_kind (id, cik_trait);
> +}
> +
> static void
> init_cp_pragma (void)
> {
> @@ -324,6 +344,7 @@ cxx_init (void)
> input_location = BUILTINS_LOCATION;
>
> init_reswords ();
> + init_cp_traits ();
> init_tree ();
> init_cp_semantics ();
> init_operators ();
> diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
> index f3abae716fe..eba5272be03 100644
> --- a/gcc/cp/parser.cc
> +++ b/gcc/cp/parser.cc
> @@ -246,6 +246,12 @@ static void cp_lexer_start_debugging
> (cp_lexer *) ATTRIBUTE_UNUSED;
> static void cp_lexer_stop_debugging
> (cp_lexer *) ATTRIBUTE_UNUSED;
> +static const cp_trait *cp_lexer_lookup_trait
> + (const cp_token *);
> +static const cp_trait *cp_lexer_lookup_trait_expr
> + (const cp_token *);
> +static const cp_trait *cp_lexer_lookup_trait_type
> + (const cp_token *);
>
> static cp_token_cache *cp_token_cache_new
> (cp_token *, cp_token *);
> @@ -279,6 +285,19 @@ static FILE *cp_lexer_debug_stream;
> sizeof, typeof, or alignof. */
> int cp_unevaluated_operand;
>
> +/* The trait table, declared in cp-tree.h. */
> +const cp_trait cp_traits[] =
> +{
> +#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> + { ARITY, CPTK_##CODE, (TCC == tcc_type) },
> +#include "cp-trait.def"
> +#undef DEFTRAIT
> +};
> +/* The trait table cannot have more than 255 (addr_space_t) entries since
> + the index is retrieved through IDENTIFIER_CP_INDEX. */
> +static_assert(ARRAY_SIZE (cp_traits) <= 255,
> + "cp_traits array cannot have more than 255 entries");
> +
> /* Dump up to NUM tokens in BUFFER to FILE starting with token
> START_TOKEN. If START_TOKEN is NULL, the dump starts with the
> first token in BUFFER. If NUM is 0, dump all the tokens. If
> @@ -1167,12 +1186,6 @@ cp_keyword_starts_decl_specifier_p (enum rid keyword)
> case RID_CONSTEVAL:
> return true;
>
> -#define DEFTRAIT_TYPE(CODE, NAME, ARITY) \
> - case RID_##CODE:
> -#include "cp-trait.def"
> -#undef DEFTRAIT_TYPE
> - return true;
> -
> default:
> if (keyword >= RID_FIRST_INT_N
> && keyword < RID_FIRST_INT_N + NUM_INT_N_ENTS
> @@ -1182,6 +1195,48 @@ cp_keyword_starts_decl_specifier_p (enum rid keyword)
> }
> }
>
> +/* Look ups the corresponding built-in trait if a given token is
> + a built-in trait. Otherwise, returns nullptr. */
> +
> +static const cp_trait *
> +cp_lexer_lookup_trait (const cp_token *token)
> +{
> + tree id = token->u.value;
> +
> + if (token->type == CPP_NAME
> + && TREE_CODE (id) == IDENTIFIER_NODE
The value of a CPP_NAME token is always an IDENTIFIER_NODE, so this
check should be redundant. Also we should access the u.value union member
only after the CPP_NAME check, since for some other token kinds u.value
isn't the active member (and reading from it would be undefined behavior
strictly speaking).
> + && IDENTIFIER_TRAIT_P (id))
> + return &cp_traits[IDENTIFIER_CP_INDEX (id)];
> +
> + return nullptr;
> +}
> +
> +/* Similarly, but only if the token is an expression-yielding
> + built-in trait. */
> +
> +static const cp_trait *
> +cp_lexer_lookup_trait_expr (const cp_token *token)
> +{
> + const cp_trait *trait = cp_lexer_lookup_trait (token);
> + if (trait && !trait->type)
> + return trait;
> +
> + return nullptr;
> +}
> +
> +/* Similarly, but only if the token is a type-yielding
> + built-in trait. */
> +
> +static const cp_trait *
> +cp_lexer_lookup_trait_type (const cp_token *token)
> +{
> + const cp_trait *trait = cp_lexer_lookup_trait (token);
> + if (trait && trait->type)
> + return trait;
> +
> + return nullptr;
> +}
> +
> /* Return true if the next token is a keyword for a decl-specifier. */
>
> static bool
> @@ -1190,6 +1245,8 @@ cp_lexer_next_token_is_decl_specifier_keyword (cp_lexer
> *lexer)
> cp_token *token;
>
> token = cp_lexer_peek_token (lexer);
> + if (cp_lexer_lookup_trait_type (token))
> + return true;
> return cp_keyword_starts_decl_specifier_p (token->keyword);
> }
>
> @@ -2854,7 +2911,7 @@ static void cp_parser_late_parsing_default_args
> static tree cp_parser_sizeof_operand
> (cp_parser *, enum rid);
> static cp_expr cp_parser_trait
> - (cp_parser *, enum rid);
> + (cp_parser *, const cp_trait *);
> static bool cp_parser_declares_only_class_p
> (cp_parser *);
> static void cp_parser_set_storage_class
> @@ -6021,12 +6078,6 @@ cp_parser_primary_expression (cp_parser *parser,
> case RID_OFFSETOF:
> return cp_parser_builtin_offsetof (parser);
>
> -#define DEFTRAIT_EXPR(CODE, NAME, ARITY) \
> - case RID_##CODE:
> -#include "cp-trait.def"
> -#undef DEFTRAIT_EXPR
> - return cp_parser_trait (parser, token->keyword);
> -
> // C++ concepts
> case RID_REQUIRES:
> return cp_parser_requires_expression (parser);
> @@ -6065,6 +6116,12 @@ cp_parser_primary_expression (cp_parser *parser,
> `::' as the beginning of a qualified-id, or the "operator"
> keyword. */
> case CPP_NAME:
> + {
> + const cp_trait* trait = cp_lexer_lookup_trait_expr (token);
> + if (trait)
A tiny nit, but we could remove the extra block scope here by doing
'if (const cp_trait* trait = ...)' instead.
> + return cp_parser_trait (parser, trait);
> + }
> + /* FALLTHRU */
> case CPP_SCOPE:
> case CPP_TEMPLATE_ID:
> case CPP_NESTED_NAME_SPECIFIER:
> @@ -11033,28 +11090,11 @@ cp_parser_builtin_offsetof (cp_parser *parser)
> /* Parse a builtin trait expression or type. */
>
> static cp_expr
> -cp_parser_trait (cp_parser* parser, enum rid keyword)
> +cp_parser_trait (cp_parser* parser, const cp_trait* trait)
> {
> - cp_trait_kind kind;
> tree type1, type2 = NULL_TREE;
> - bool binary = false;
> - bool variadic = false;
> - bool type = false;
> -
> - switch (keyword)
> - {
> -#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
> - case RID_##CODE: \
> - kind = CPTK_##CODE; \
> - binary = (ARITY == 2); \
> - variadic = (ARITY == -1); \
> - type = (TCC == tcc_type); \
> - break;
> -#include "cp-trait.def"
> -#undef DEFTRAIT
> - default:
> - gcc_unreachable ();
> - }
> + const bool binary = (trait->arity == 2);
> + const bool variadic = (trait->arity == -1);
Could we continue defining the local variables 'kind' and 'type' here so
that we don't have to adjust their uses in the rest of the function?
That should yield a smaller diff for this function.
>
> /* Get location of initial token. */
> location_t start_loc = cp_lexer_peek_token (parser->lexer)->location;
> @@ -11063,12 +11103,12 @@ cp_parser_trait (cp_parser* parser, enum rid
> keyword)
> cp_lexer_consume_token (parser->lexer);
>
> matching_parens parens;
> - if (kind == CPTK_TYPE_PACK_ELEMENT)
> + if (trait->kind == CPTK_TYPE_PACK_ELEMENT)
> cp_parser_require (parser, CPP_LESS, RT_LESS);
> else
> parens.require_open (parser);
>
> - if (kind == CPTK_IS_DEDUCIBLE)
> + if (trait->kind == CPTK_IS_DEDUCIBLE)
> {
> const cp_token* token = cp_lexer_peek_token (parser->lexer);
> type1 = cp_parser_id_expression (parser,
> @@ -11079,7 +11119,7 @@ cp_parser_trait (cp_parser* parser, enum rid keyword)
> /*optional_p=*/false);
> type1 = cp_parser_lookup_name_simple (parser, type1, token->location);
> }
> - else if (kind == CPTK_TYPE_PACK_ELEMENT)
> + else if (trait->kind == CPTK_TYPE_PACK_ELEMENT)
> /* __type_pack_element takes an expression as its first argument and uses
> template-id syntax instead of function call syntax (for consistency
> with Clang). We special case these properties of __type_pack_element
> @@ -11094,7 +11134,7 @@ cp_parser_trait (cp_parser* parser, enum rid keyword)
> if (type1 == error_mark_node)
> return error_mark_node;
>
> - if (kind == CPTK_TYPE_PACK_ELEMENT)
> + if (trait->kind == CPTK_TYPE_PACK_ELEMENT)
> {
> cp_parser_require (parser, CPP_COMMA, RT_COMMA);
> tree trailing = cp_parser_enclosed_template_argument_list (parser);
> @@ -11144,7 +11184,7 @@ cp_parser_trait (cp_parser* parser, enum rid keyword)
> }
>
> location_t finish_loc = cp_lexer_peek_token (parser->lexer)->location;
> - if (kind == CPTK_TYPE_PACK_ELEMENT)
> + if (trait->kind == CPTK_TYPE_PACK_ELEMENT)
> /* cp_parser_enclosed_template_argument_list above already took care
> of parsing the closing '>'. */;
> else
> @@ -11158,17 +11198,17 @@ cp_parser_trait (cp_parser* parser, enum rid
> keyword)
>
> /* Complete the trait expression, which may mean either processing
> the trait expr now or saving it for template instantiation. */
> - switch (kind)
> + switch (trait->kind)
> {
> case CPTK_BASES:
> return cp_expr (finish_bases (type1, false), trait_loc);
> case CPTK_DIRECT_BASES:
> return cp_expr (finish_bases (type1, true), trait_loc);
> default:
> - if (type)
> - return finish_trait_type (kind, type1, type2, tf_warning_or_error);
> + if (trait->type)
> + return finish_trait_type (trait->kind, type1, type2,
> tf_warning_or_error);
> else
> - return finish_trait_expr (trait_loc, kind, type1, type2);
> + return finish_trait_expr (trait_loc, trait->kind, type1, type2);
> }
> }
>
> @@ -20081,20 +20121,21 @@ cp_parser_simple_type_specifier (cp_parser* parser,
>
> return type;
>
> -#define DEFTRAIT_TYPE(CODE, NAME, ARITY) \
> - case RID_##CODE:
> -#include "cp-trait.def"
> -#undef DEFTRAIT_TYPE
> - type = cp_parser_trait (parser, token->keyword);
> + default:
> + break;
> + }
> +
> + /* If token is a type-yielding built-in traits, parse it. */
> + const cp_trait* trait = cp_lexer_lookup_trait_type (token);
> + if (trait)
> + {
> + type = cp_parser_trait (parser, trait);
> if (decl_specs)
> cp_parser_set_decl_spec_type (decl_specs, type,
> token,
> /*type_definition_p=*/false);
>
> return type;
> -
> - default:
> - break;
> }
>
> /* If token is an already-parsed decltype not followed by ::,
> --
> 2.42.0
>
>
