[PATCH v26 02/23] c-family, c++: Look up built-in traits via identifier node

[Ken Matsui <kmatsui@gcc.gnu.org>]

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.

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 (cp_traits): Define its values, declared in cp-tree.h.
	(init_cp_traits): New function to set cik_trait and
	IDENTIFIER_CP_INDEX for all built-in trait identifiers.
	(cxx_init): Call init_cp_traits function.
	* parser.cc (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 <ppalka@redhat.com>
Signed-off-by: Ken Matsui <kmatsui@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          |  32 +++++++++---
 gcc/cp/lex.cc             |  34 ++++++++++++
 gcc/cp/parser.cc          | 105 +++++++++++++++++++++++---------------
 6 files changed, 126 insertions(+), 65 deletions(-)

diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
index d175054dddb..0f1de44a348 100644
--- a/gcc/c-family/c-common.cc
+++ b/gcc/c-family/c-common.cc
@@ -560,13 +560,6 @@ 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 cb9b6f301d8..62d76c87cc0 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 9439c4dc744..ee88df5767b 100644
--- a/gcc/cp/cp-objcp-common.cc
+++ b/gcc/cp/cp-objcp-common.cc
@@ -565,6 +565,10 @@ 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))
@@ -578,10 +582,6 @@ 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 cb89d372b23..cbf280ec454 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -1237,7 +1237,7 @@ 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
 };
 
@@ -1282,9 +1282,9 @@ 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)		\
@@ -1297,12 +1297,18 @@ 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)			\
@@ -1386,16 +1392,26 @@ 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 {
+  const char *name;
+  cp_trait_kind kind;
+  short arity;
+  bool type;
+};
+
+/* The trait table indexed by cp_trait_kind.  */
+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..a939e2e5f13 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);
@@ -97,6 +98,19 @@ ovl_op_info_t ovl_op_info[2][OVL_OP_MAX] =
 unsigned char ovl_op_mapping[MAX_TREE_CODES];
 unsigned char ovl_op_alternate[OVL_OP_MAX];
 
+/* The trait table, declared in cp-tree.h.  */
+const cp_trait cp_traits[] =
+{
+#define DEFTRAIT(TCC, CODE, NAME, ARITY) \
+  { NAME, CPTK_##CODE, ARITY, (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");
+
 /* Get the name of the kind of identifier T.  */
 
 const char *
@@ -283,6 +297,25 @@ init_reswords (void)
     }
 }
 
+/* Initialize the C++ traits.  */
+static void
+init_cp_traits (void)
+{
+  tree id;
+
+  for (unsigned int i = 0; i < ARRAY_SIZE (cp_traits); ++i)
+    {
+      id = get_identifier (cp_traits[i].name);
+      IDENTIFIER_CP_INDEX (id) = cp_traits[i].kind;
+      set_identifier_kind (id, cik_trait);
+    }
+
+  /* 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 +357,7 @@ 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 732d2a919eb..a416b58a2a5 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 *);
@@ -1173,12 +1179,6 @@ 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
@@ -1188,6 +1188,44 @@ 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)
+{
+  if (token->type == CPP_NAME && IDENTIFIER_TRAIT_P (token->u.value))
+    return &cp_traits[IDENTIFIER_CP_INDEX (token->u.value)];
+
+  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
@@ -1196,6 +1234,8 @@ 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);
 }
 
@@ -2861,7 +2901,7 @@ 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
@@ -6055,12 +6095,6 @@ 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);
@@ -6099,6 +6133,9 @@ cp_parser_primary_expression (cp_parser *parser,
 	 `::' as the beginning of a qualified-id, or the "operator"
 	 keyword.  */
     case CPP_NAME:
+      if (const cp_trait* trait = cp_lexer_lookup_trait_expr (token))
+	return cp_parser_trait (parser, trait);
+      /* FALLTHRU */
     case CPP_SCOPE:
     case CPP_TEMPLATE_ID:
     case CPP_NESTED_NAME_SPECIFIER:
@@ -11029,28 +11066,13 @@ 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;
+  const cp_trait_kind kind = trait->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);
+  const bool type = trait->type;
 
   /* Get location of initial token.  */
   location_t start_loc = cp_lexer_peek_token (parser->lexer)->location;
@@ -20124,20 +20146,21 @@ 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 ::,
-- 
2.43.0