[PATCH v18 02/40] c-family, c++: Look up built-in traits through gperf

[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 gperf 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:

	* Make-lang.in: Add targets to generate cp-trait.gperf and
	cp-trait.h.
	* 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 identifier.
	* cp-tree.h (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.
	(cxx_init): Call init_cp_traits function.
	* parser.cc (cp_lexer_lookup_trait): New function to look up a
	built-in trait from a token by gperf.
	(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.
	* cp-trait-head.in: New file.
	* cp-trait.gperf: New file.
	* cp-trait.h: New file.

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/Make-lang.in       |  26 ++++
 gcc/cp/cp-objcp-common.cc |   8 +-
 gcc/cp/cp-trait-head.in   |  30 +++++
 gcc/cp/cp-trait.gperf     |  74 ++++++++++++
 gcc/cp/cp-trait.h         | 247 ++++++++++++++++++++++++++++++++++++++
 gcc/cp/cp-tree.h          |  14 ++-
 gcc/cp/lex.cc             |  19 +++
 gcc/cp/parser.cc          | 132 ++++++++++++--------
 10 files changed, 492 insertions(+), 70 deletions(-)
 create mode 100644 gcc/cp/cp-trait-head.in
 create mode 100644 gcc/cp/cp-trait.gperf
 create mode 100644 gcc/cp/cp-trait.h

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/Make-lang.in b/gcc/cp/Make-lang.in
index 2727fb7f8cc..a67d1c3e9f3 100644
--- a/gcc/cp/Make-lang.in
+++ b/gcc/cp/Make-lang.in
@@ -34,6 +34,8 @@
 # - the compiler proper (eg: cc1plus)
 # - define the names for selecting the language in LANGUAGES.
 
+AWK = @AWK@
+
 # Actual names to use when installing a native compiler.
 CXX_INSTALL_NAME := $(shell echo c++|sed '$(program_transform_name)')
 GXX_INSTALL_NAME := $(shell echo g++|sed '$(program_transform_name)')
@@ -186,6 +188,30 @@ endif
 # This is the file that depends on the generated header file.
 cp/name-lookup.o: $(srcdir)/cp/std-name-hint.h
 
+# We always need the dependency on the .gperf file
+# because it itself is generated.
+ifeq ($(ENABLE_MAINTAINER_RULES), true)
+$(srcdir)/cp/cp-trait.h: $(srcdir)/cp/cp-trait.gperf
+else
+$(srcdir)/cp/cp-trait.h: | $(srcdir)/cp/cp-trait.gperf
+endif
+	gperf -o -C -E -k '8' -D -N 'find' -L C++ \
+		$(srcdir)/cp/cp-trait.gperf --output-file $(srcdir)/cp/cp-trait.h
+
+# The cp-trait.gperf file itself is generated from
+# cp-trait-head.in and cp-trait.def files.
+$(srcdir)/cp/cp-trait.gperf: $(srcdir)/cp/cp-trait-head.in $(srcdir)/cp/cp-trait.def
+	cat $< > $@
+	$(AWK) -F', *' '/^DEFTRAIT_/ { \
+		type = (index($$1, "DEFTRAIT_TYPE") != 0 ? "true" : "false"); \
+		gsub(/DEFTRAIT_(EXPR|TYPE) \(/, "", $$1); \
+		gsub(/\)/, "", $$3); \
+		print $$2", CPTK_" $$1", "$$3", "type; \
+	}' $(srcdir)/cp/cp-trait.def >> $@
+
+# This is the file that depends on the generated header file.
+cp/parser.o: $(srcdir)/cp/cp-trait.h
+
 components_in_prev = "bfd opcodes binutils fixincludes gas gcc gmp mpfr mpc isl gold intl ld libbacktrace libcpp libcody libdecnumber libiberty libiberty-linker-plugin libiconv zlib lto-plugin libctf libsframe"
 components_in_prev_target = "libstdc++-v3 libsanitizer libvtv libgcc libbacktrace libphobos zlib libgomp libatomic"
 
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-trait-head.in b/gcc/cp/cp-trait-head.in
new file mode 100644
index 00000000000..9357eea1238
--- /dev/null
+++ b/gcc/cp/cp-trait-head.in
@@ -0,0 +1,30 @@
+%language=C++
+%define class-name cp_trait_lookup
+%struct-type
+%{
+/* Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+%}
+struct cp_trait {
+  const char *name;
+  enum cp_trait_kind kind;
+  short arity;
+  bool type;
+};
+%%
+"__is_same_as", CPTK_IS_SAME, 2, false
diff --git a/gcc/cp/cp-trait.gperf b/gcc/cp/cp-trait.gperf
new file mode 100644
index 00000000000..47e3c1af499
--- /dev/null
+++ b/gcc/cp/cp-trait.gperf
@@ -0,0 +1,74 @@
+%language=C++
+%define class-name cp_trait_lookup
+%struct-type
+%{
+/* Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+%}
+struct cp_trait {
+  const char *name;
+  enum cp_trait_kind kind;
+  short arity;
+  bool type;
+};
+%%
+"__is_same_as", CPTK_IS_SAME, 2, false
+"__has_nothrow_assign", CPTK_HAS_NOTHROW_ASSIGN, 1, false
+"__has_nothrow_constructor", CPTK_HAS_NOTHROW_CONSTRUCTOR, 1, false
+"__has_nothrow_copy", CPTK_HAS_NOTHROW_COPY, 1, false
+"__has_trivial_assign", CPTK_HAS_TRIVIAL_ASSIGN, 1, false
+"__has_trivial_constructor", CPTK_HAS_TRIVIAL_CONSTRUCTOR, 1, false
+"__has_trivial_copy", CPTK_HAS_TRIVIAL_COPY, 1, false
+"__has_trivial_destructor", CPTK_HAS_TRIVIAL_DESTRUCTOR, 1, false
+"__has_unique_object_representations", CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS, 1, false
+"__has_virtual_destructor", CPTK_HAS_VIRTUAL_DESTRUCTOR, 1, false
+"__is_abstract", CPTK_IS_ABSTRACT, 1, false
+"__is_aggregate", CPTK_IS_AGGREGATE, 1, false
+"__is_assignable", CPTK_IS_ASSIGNABLE, 2, false
+"__is_base_of", CPTK_IS_BASE_OF, 2, false
+"__is_class", CPTK_IS_CLASS, 1, false
+"__is_constructible", CPTK_IS_CONSTRUCTIBLE, -1, false
+"__is_convertible", CPTK_IS_CONVERTIBLE, 2, false
+"__is_empty", CPTK_IS_EMPTY, 1, false
+"__is_enum", CPTK_IS_ENUM, 1, false
+"__is_final", CPTK_IS_FINAL, 1, false
+"__is_layout_compatible", CPTK_IS_LAYOUT_COMPATIBLE, 2, false
+"__is_literal_type", CPTK_IS_LITERAL_TYPE, 1, false
+"__is_nothrow_assignable", CPTK_IS_NOTHROW_ASSIGNABLE, 2, false
+"__is_nothrow_constructible", CPTK_IS_NOTHROW_CONSTRUCTIBLE, -1, false
+"__is_nothrow_convertible", CPTK_IS_NOTHROW_CONVERTIBLE, 2, false
+"__is_pointer_interconvertible_base_of", CPTK_IS_POINTER_INTERCONVERTIBLE_BASE_OF, 2, false
+"__is_pod", CPTK_IS_POD, 1, false
+"__is_polymorphic", CPTK_IS_POLYMORPHIC, 1, false
+"__is_same", CPTK_IS_SAME, 2, false
+"__is_standard_layout", CPTK_IS_STD_LAYOUT, 1, false
+"__is_trivial", CPTK_IS_TRIVIAL, 1, false
+"__is_trivially_assignable", CPTK_IS_TRIVIALLY_ASSIGNABLE, 2, false
+"__is_trivially_constructible", CPTK_IS_TRIVIALLY_CONSTRUCTIBLE, -1, false
+"__is_trivially_copyable", CPTK_IS_TRIVIALLY_COPYABLE, 1, false
+"__is_union", CPTK_IS_UNION, 1, false
+"__reference_constructs_from_temporary", CPTK_REF_CONSTRUCTS_FROM_TEMPORARY, 2, false
+"__reference_converts_from_temporary", CPTK_REF_CONVERTS_FROM_TEMPORARY, 2, false
+"__remove_cv", CPTK_REMOVE_CV, 1, true
+"__remove_cvref", CPTK_REMOVE_CVREF, 1, true
+"__remove_reference", CPTK_REMOVE_REFERENCE, 1, true
+"__type_pack_element", CPTK_TYPE_PACK_ELEMENT, -1, true
+"__underlying_type", CPTK_UNDERLYING_TYPE, 1, true
+"__is_deducible ", CPTK_IS_DEDUCIBLE, 2, false
+"__bases", CPTK_BASES, 1, true
+"__direct_bases", CPTK_DIRECT_BASES, 1, true
diff --git a/gcc/cp/cp-trait.h b/gcc/cp/cp-trait.h
new file mode 100644
index 00000000000..97ba8492d15
--- /dev/null
+++ b/gcc/cp/cp-trait.h
@@ -0,0 +1,247 @@
+/* C++ code produced by gperf version 3.1 */
+/* Command-line: gperf -o -C -E -k 8 -D -N find -L C++ --output-file ../../gcc/cp/cp-trait.h ../../gcc/cp/cp-trait.gperf  */
+
+#if !((' ' == 32) && ('!' == 33) && ('"' == 34) && ('#' == 35) \
+      && ('%' == 37) && ('&' == 38) && ('\'' == 39) && ('(' == 40) \
+      && (')' == 41) && ('*' == 42) && ('+' == 43) && (',' == 44) \
+      && ('-' == 45) && ('.' == 46) && ('/' == 47) && ('0' == 48) \
+      && ('1' == 49) && ('2' == 50) && ('3' == 51) && ('4' == 52) \
+      && ('5' == 53) && ('6' == 54) && ('7' == 55) && ('8' == 56) \
+      && ('9' == 57) && (':' == 58) && (';' == 59) && ('<' == 60) \
+      && ('=' == 61) && ('>' == 62) && ('?' == 63) && ('A' == 65) \
+      && ('B' == 66) && ('C' == 67) && ('D' == 68) && ('E' == 69) \
+      && ('F' == 70) && ('G' == 71) && ('H' == 72) && ('I' == 73) \
+      && ('J' == 74) && ('K' == 75) && ('L' == 76) && ('M' == 77) \
+      && ('N' == 78) && ('O' == 79) && ('P' == 80) && ('Q' == 81) \
+      && ('R' == 82) && ('S' == 83) && ('T' == 84) && ('U' == 85) \
+      && ('V' == 86) && ('W' == 87) && ('X' == 88) && ('Y' == 89) \
+      && ('Z' == 90) && ('[' == 91) && ('\\' == 92) && (']' == 93) \
+      && ('^' == 94) && ('_' == 95) && ('a' == 97) && ('b' == 98) \
+      && ('c' == 99) && ('d' == 100) && ('e' == 101) && ('f' == 102) \
+      && ('g' == 103) && ('h' == 104) && ('i' == 105) && ('j' == 106) \
+      && ('k' == 107) && ('l' == 108) && ('m' == 109) && ('n' == 110) \
+      && ('o' == 111) && ('p' == 112) && ('q' == 113) && ('r' == 114) \
+      && ('s' == 115) && ('t' == 116) && ('u' == 117) && ('v' == 118) \
+      && ('w' == 119) && ('x' == 120) && ('y' == 121) && ('z' == 122) \
+      && ('{' == 123) && ('|' == 124) && ('}' == 125) && ('~' == 126))
+/* The character set is not based on ISO-646.  */
+#error "gperf generated tables don't work with this execution character set. Please report a bug to <bug-gperf@gnu.org>."
+#endif
+
+#line 4 "../../gcc/cp/cp-trait.gperf"
+
+/* Copyright (C) 2023 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+#line 23 "../../gcc/cp/cp-trait.gperf"
+struct cp_trait {
+  const char *name;
+  enum cp_trait_kind kind;
+  short arity;
+  bool type;
+};
+/* maximum key range = 79, duplicates = 0 */
+
+class cp_trait_lookup
+{
+private:
+  static inline unsigned int hash (const char *str, size_t len);
+public:
+  static const struct cp_trait *find (const char *str, size_t len);
+};
+
+inline unsigned int
+cp_trait_lookup::hash (const char *str, size_t len)
+{
+  static const unsigned char asso_values[] =
+    {
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86,  1, 86, 86,
+       0, 35, 86,  0, 86,  0, 86, 86, 10, 10,
+      50, 15, 55, 86, 30,  5, 15,  0, 86, 86,
+      86, 20, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86, 86, 86, 86, 86,
+      86, 86, 86, 86, 86, 86
+    };
+  unsigned int hval = len;
+
+  switch (hval)
+    {
+      default:
+        hval += asso_values[static_cast<unsigned char>(str[7])];
+      /*FALLTHROUGH*/
+      case 7:
+        break;
+    }
+  return hval;
+}
+
+const struct cp_trait *
+cp_trait_lookup::find (const char *str, size_t len)
+{
+  enum
+    {
+      TOTAL_KEYWORDS = 45,
+      MIN_WORD_LENGTH = 7,
+      MAX_WORD_LENGTH = 37,
+      MIN_HASH_VALUE = 7,
+      MAX_HASH_VALUE = 85
+    };
+
+  static const struct cp_trait wordlist[] =
+    {
+#line 73 "../../gcc/cp/cp-trait.gperf"
+      {"__bases", CPTK_BASES, 1, true},
+#line 56 "../../gcc/cp/cp-trait.gperf"
+      {"__is_pod", CPTK_IS_POD, 1, false},
+#line 48 "../../gcc/cp/cp-trait.gperf"
+      {"__is_enum", CPTK_IS_ENUM, 1, false},
+#line 64 "../../gcc/cp/cp-trait.gperf"
+      {"__is_union", CPTK_IS_UNION, 1, false},
+#line 44 "../../gcc/cp/cp-trait.gperf"
+      {"__is_class", CPTK_IS_CLASS, 1, false},
+#line 60 "../../gcc/cp/cp-trait.gperf"
+      {"__is_trivial", CPTK_IS_TRIVIAL, 1, false},
+#line 41 "../../gcc/cp/cp-trait.gperf"
+      {"__is_aggregate", CPTK_IS_AGGREGATE, 1, false},
+#line 72 "../../gcc/cp/cp-trait.gperf"
+      {"__is_deducible ", CPTK_IS_DEDUCIBLE, 2, false},
+#line 43 "../../gcc/cp/cp-trait.gperf"
+      {"__is_base_of", CPTK_IS_BASE_OF, 2, false},
+#line 40 "../../gcc/cp/cp-trait.gperf"
+      {"__is_abstract", CPTK_IS_ABSTRACT, 1, false},
+#line 58 "../../gcc/cp/cp-trait.gperf"
+      {"__is_same", CPTK_IS_SAME, 2, false},
+#line 42 "../../gcc/cp/cp-trait.gperf"
+      {"__is_assignable", CPTK_IS_ASSIGNABLE, 2, false},
+#line 59 "../../gcc/cp/cp-trait.gperf"
+      {"__is_standard_layout", CPTK_IS_STD_LAYOUT, 1, false},
+#line 30 "../../gcc/cp/cp-trait.gperf"
+      {"__is_same_as", CPTK_IS_SAME, 2, false},
+#line 63 "../../gcc/cp/cp-trait.gperf"
+      {"__is_trivially_copyable", CPTK_IS_TRIVIALLY_COPYABLE, 1, false},
+#line 39 "../../gcc/cp/cp-trait.gperf"
+      {"__has_virtual_destructor", CPTK_HAS_VIRTUAL_DESTRUCTOR, 1, false},
+#line 61 "../../gcc/cp/cp-trait.gperf"
+      {"__is_trivially_assignable", CPTK_IS_TRIVIALLY_ASSIGNABLE, 2, false},
+#line 57 "../../gcc/cp/cp-trait.gperf"
+      {"__is_polymorphic", CPTK_IS_POLYMORPHIC, 1, false},
+#line 71 "../../gcc/cp/cp-trait.gperf"
+      {"__underlying_type", CPTK_UNDERLYING_TYPE, 1, true},
+#line 62 "../../gcc/cp/cp-trait.gperf"
+      {"__is_trivially_constructible", CPTK_IS_TRIVIALLY_CONSTRUCTIBLE, -1, false},
+#line 74 "../../gcc/cp/cp-trait.gperf"
+      {"__direct_bases", CPTK_DIRECT_BASES, 1, true},
+#line 51 "../../gcc/cp/cp-trait.gperf"
+      {"__is_literal_type", CPTK_IS_LITERAL_TYPE, 1, false},
+#line 33 "../../gcc/cp/cp-trait.gperf"
+      {"__has_nothrow_copy", CPTK_HAS_NOTHROW_COPY, 1, false},
+#line 31 "../../gcc/cp/cp-trait.gperf"
+      {"__has_nothrow_assign", CPTK_HAS_NOTHROW_ASSIGN, 1, false},
+#line 55 "../../gcc/cp/cp-trait.gperf"
+      {"__is_pointer_interconvertible_base_of", CPTK_IS_POINTER_INTERCONVERTIBLE_BASE_OF, 2, false},
+#line 52 "../../gcc/cp/cp-trait.gperf"
+      {"__is_nothrow_assignable", CPTK_IS_NOTHROW_ASSIGNABLE, 2, false},
+#line 54 "../../gcc/cp/cp-trait.gperf"
+      {"__is_nothrow_convertible", CPTK_IS_NOTHROW_CONVERTIBLE, 2, false},
+#line 32 "../../gcc/cp/cp-trait.gperf"
+      {"__has_nothrow_constructor", CPTK_HAS_NOTHROW_CONSTRUCTOR, 1, false},
+#line 53 "../../gcc/cp/cp-trait.gperf"
+      {"__is_nothrow_constructible", CPTK_IS_NOTHROW_CONSTRUCTIBLE, -1, false},
+#line 50 "../../gcc/cp/cp-trait.gperf"
+      {"__is_layout_compatible", CPTK_IS_LAYOUT_COMPATIBLE, 2, false},
+#line 67 "../../gcc/cp/cp-trait.gperf"
+      {"__remove_cv", CPTK_REMOVE_CV, 1, true},
+#line 36 "../../gcc/cp/cp-trait.gperf"
+      {"__has_trivial_copy", CPTK_HAS_TRIVIAL_COPY, 1, false},
+#line 68 "../../gcc/cp/cp-trait.gperf"
+      {"__remove_cvref", CPTK_REMOVE_CVREF, 1, true},
+#line 34 "../../gcc/cp/cp-trait.gperf"
+      {"__has_trivial_assign", CPTK_HAS_TRIVIAL_ASSIGN, 1, false},
+#line 69 "../../gcc/cp/cp-trait.gperf"
+      {"__remove_reference", CPTK_REMOVE_REFERENCE, 1, true},
+#line 37 "../../gcc/cp/cp-trait.gperf"
+      {"__has_trivial_destructor", CPTK_HAS_TRIVIAL_DESTRUCTOR, 1, false},
+#line 35 "../../gcc/cp/cp-trait.gperf"
+      {"__has_trivial_constructor", CPTK_HAS_TRIVIAL_CONSTRUCTOR, 1, false},
+#line 49 "../../gcc/cp/cp-trait.gperf"
+      {"__is_final", CPTK_IS_FINAL, 1, false},
+#line 47 "../../gcc/cp/cp-trait.gperf"
+      {"__is_empty", CPTK_IS_EMPTY, 1, false},
+#line 46 "../../gcc/cp/cp-trait.gperf"
+      {"__is_convertible", CPTK_IS_CONVERTIBLE, 2, false},
+#line 45 "../../gcc/cp/cp-trait.gperf"
+      {"__is_constructible", CPTK_IS_CONSTRUCTIBLE, -1, false},
+#line 66 "../../gcc/cp/cp-trait.gperf"
+      {"__reference_converts_from_temporary", CPTK_REF_CONVERTS_FROM_TEMPORARY, 2, false},
+#line 65 "../../gcc/cp/cp-trait.gperf"
+      {"__reference_constructs_from_temporary", CPTK_REF_CONSTRUCTS_FROM_TEMPORARY, 2, false},
+#line 70 "../../gcc/cp/cp-trait.gperf"
+      {"__type_pack_element", CPTK_TYPE_PACK_ELEMENT, -1, true},
+#line 38 "../../gcc/cp/cp-trait.gperf"
+      {"__has_unique_object_representations", CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS, 1, false}
+    };
+
+  static const signed char lookup[] =
+    {
+      -1, -1, -1, -1, -1, -1, -1,  0,  1,  2,  3,  4,  5, -1,
+       6,  7, -1,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
+      19, 20, -1, -1, 21, 22, -1, 23, -1, 24, 25, 26, 27, 28,
+      29, -1, -1, -1, 30, -1, 31, 32, 33, -1, -1, 34, 35, 36,
+      -1, -1, -1, -1, 37, -1, -1, -1, -1, 38, 39, -1, 40, -1,
+      41, -1, 42, -1, 43, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, 44
+    };
+
+  if (len <= MAX_WORD_LENGTH && len >= MIN_WORD_LENGTH)
+    {
+      unsigned int key = hash (str, len);
+
+      if (key <= MAX_HASH_VALUE)
+        {
+          int index = lookup[key];
+
+          if (index >= 0)
+            {
+              const char *s = wordlist[index].name;
+
+              if (*str == *s && !strcmp (str + 1, s + 1))
+                return &wordlist[index];
+            }
+        }
+    }
+  return 0;
+}
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 6e34952da99..7baacfca0a7 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,	/* Build-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)			\
diff --git a/gcc/cp/lex.cc b/gcc/cp/lex.cc
index 64bcfb18196..f6e1f6a4075 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 +284,23 @@ 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); \
+  set_identifier_kind (id, cik_trait);
+#include "cp/cp-trait.def"
+#undef DEFTRAIT
+
+  /* An alias for __is_same.  */
+  id = get_identifier ("__is_same_as");
+  set_identifier_kind (id, cik_trait);
+}
+
 static void
 init_cp_pragma (void)
 {
@@ -324,6 +342,7 @@ 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..39952893ffa 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -49,6 +49,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "contracts.h"
 #include "bitmap.h"
 #include "builtins.h"
+#include "cp-trait.h"
 
 \f
 /* The lexer.  */
@@ -246,6 +247,12 @@ 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 *);
@@ -1167,12 +1174,6 @@ 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 +1183,51 @@ 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
+      && IDENTIFIER_TRAIT_P (id))
+    {
+      const char *id_str = IDENTIFIER_POINTER (id);
+      const int id_len = IDENTIFIER_LENGTH (id);
+      return cp_trait_lookup::find (id_str, id_len);
+    }
+  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 +1236,8 @@ 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 +2902,7 @@ 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 +6069,6 @@ 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 +6107,12 @@ 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)
+	  return cp_parser_trait (parser, trait);
+      }
+      /* FALLTHRU */
     case CPP_SCOPE:
     case CPP_TEMPLATE_ID:
     case CPP_NESTED_NAME_SPECIFIER:
@@ -11033,28 +11081,11 @@ 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);
 
   /* Get location of initial token.  */
   location_t start_loc = cp_lexer_peek_token (parser->lexer)->location;
@@ -11063,12 +11094,12 @@ 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 +11110,7 @@ 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 +11125,7 @@ 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 +11175,7 @@ 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 +11189,17 @@ 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 +20112,21 @@ 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