On Mon, Oct 16, 2023 at 7:55 AM Patrick Palka <ppa...@redhat.com> wrote:
>
> 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.
>
Thank you so much for your review :)
> >
> > 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.
>
Thank you!
> > (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.
>
I see. Since we know the number of iterations would be up to 255 and
the inner statements are only 3 and pretty simple/small, I think it is
likely that we will benefit from loop unrolling. But do we want to
prioritize the binary size over the possible performance improvements?
> > +
> > + /* 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).
>
Thank you!
> > + && 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.
>
Thank you!
> > + 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.
>
Yes, I will update this patch. Thank you!
> >
> > /* 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
> >
> >
>
