[libc++] Define a few Lit features using the new DSL

This commit migrates some of the Lit features from config.py to the new
DSL. This simplifies config.py and is a first step towards defining all
the features using the DSL instead of the complex logic in config.py.

Differential Revision: https://reviews.llvm.org/D78382

libcxx/utils/libcxx/test/config.py

@@ -22,6 +22,7 @@
 from libcxx.test.executor import *
 from libcxx.test.tracing import *
 import libcxx.util
+import libcxx.test.features
 
 def loadSiteConfig(lit_config, config, param_name, env_name):
     # We haven't loaded the site specific configuration (the user is
@@ -130,7 +131,6 @@ def configure(self):
         self.configure_obj_root()
         self.configure_cxx_stdlib_under_test()
         self.configure_cxx_library_root()
-        self.configure_use_thread_safety()
         self.configure_ccache()
         self.configure_compile_flags()
         self.configure_link_flags()
@@ -141,11 +141,14 @@ def configure(self):
         self.configure_sanitizer()
         self.configure_coverage()
         self.configure_modules()
-        self.configure_coroutines()
-        self.configure_blocks()
-        self.configure_objc_arc()
         self.configure_substitutions()
         self.configure_features()
+        self.configure_new_features()
+
+    def configure_new_features(self):
+        supportedFeatures = [f for f in libcxx.test.features.features if f.isSupported(self.config)]
+        for feature in supportedFeatures:
+            feature.enableIn(self.config)
 
     def print_config_info(self):
         # Print the final compile and link flags.
@@ -322,14 +325,6 @@ def configure_cxx_stdlib_under_test(self):
             if self.get_lit_conf('enable_experimental') is None:
                 self.config.enable_experimental = 'true'
 
-    def configure_use_thread_safety(self):
-        '''If set, run clang with -verify on failing tests.'''
-        has_thread_safety = self.cxx.hasCompileFlag('-Werror=thread-safety')
-        if has_thread_safety:
-            self.cxx.compile_flags += ['-Werror=thread-safety']
-            self.config.available_features.add('thread-safety')
-            self.lit_config.note("enabling thread-safety annotations")
-
     def configure_ccache(self):
         use_ccache_default = os.environ.get('LIBCXX_USE_CCACHE') is not None
         use_ccache = self.get_lit_bool('use_ccache', use_ccache_default)
@@ -384,36 +379,9 @@ def configure_features(self):
         if not self.get_lit_bool('enable_filesystem', default=True):
             self.config.available_features.add('c++filesystem-disabled')
 
-
-        # Run a compile test for the -fsized-deallocation flag. This is needed
-        # in test/std/language.support/support.dynamic/new.delete
-        if self.cxx.hasCompileFlag('-fsized-deallocation'):
-            self.config.available_features.add('-fsized-deallocation')
-
-        if self.cxx.hasCompileFlag('-faligned-allocation'):
-            self.config.available_features.add('-faligned-allocation')
-
-        if self.cxx.hasCompileFlag('-fdelayed-template-parsing'):
-            self.config.available_features.add('fdelayed-template-parsing')
-
         if self.get_lit_bool('has_libatomic', False):
             self.config.available_features.add('libatomic')
 
-        macros = self._dump_macros_verbose()
-        if '__cpp_if_constexpr' not in macros:
-            self.config.available_features.add('libcpp-no-if-constexpr')
-
-        if '__cpp_structured_bindings' not in macros:
-            self.config.available_features.add('libcpp-no-structured-bindings')
-
-        if '__cpp_deduction_guides' not in macros or \
-                intMacroValue(macros['__cpp_deduction_guides']) < 201611:
-            self.config.available_features.add('libcpp-no-deduction-guides')
-
-        if '__cpp_concepts' not in macros or \
-                intMacroValue(macros['__cpp_concepts']) < 201811:
-            self.config.available_features.add('libcpp-no-concepts')
-
         if self.target_info.is_windows():
             self.config.available_features.add('windows')
             if self.cxx_stdlib_under_test == 'libc++':
@@ -429,12 +397,6 @@ def configure_features(self):
             self.config.available_features.add('libcxx_gdb')
             self.cxx.libcxx_gdb = libcxx_gdb
 
-        # Support Objective-C++ only on MacOS and if the compiler supports it.
-        if self.target_info.platform() == "darwin" and \
-           self.target_info.is_host_macosx() and \
-           self.cxx.hasCompileFlag(["-x", "objective-c++", "-fobjc-arc"]):
-            self.config.available_features.add("objective-c++")
-
     def configure_compile_flags(self):
         self.configure_default_compile_flags()
         # Configure extra flags
@@ -820,9 +782,6 @@ def configure_warnings(self):
         # don't enable warnings in system headers on GCC.
         if self.cxx.type != 'gcc':
             self.cxx.warning_flags += ['-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER']
-        if self.cxx.hasWarningFlag('-Wuser-defined-warnings'):
-            self.cxx.warning_flags += ['-Wuser-defined-warnings']
-            self.config.available_features.add('diagnose-if-support')
         self.cxx.addWarningFlagIfSupported('-Wshadow')
         self.cxx.addWarningFlagIfSupported('-Wno-unused-command-line-argument')
         self.cxx.addWarningFlagIfSupported('-Wno-attributes')
@@ -908,27 +867,6 @@ def configure_coverage(self):
             self.cxx.flags += ['-g', '--coverage']
             self.cxx.compile_flags += ['-O0']
 
-    def configure_coroutines(self):
-        if self.cxx.hasCompileFlag('-fcoroutines-ts'):
-            macros = self._dump_macros_verbose(flags=['-fcoroutines-ts'])
-            if '__cpp_coroutines' not in macros:
-                self.lit_config.warning('-fcoroutines-ts is supported but '
-                    '__cpp_coroutines is not defined')
-            # Consider coroutines supported only when the feature test macro
-            # reflects a recent value.
-            if intMacroValue(macros['__cpp_coroutines']) >= 201703:
-                self.config.available_features.add('fcoroutines-ts')
-
-    def configure_blocks(self):
-        if self.cxx.hasCompileFlag('-fblocks'):
-            self.config.available_features.add('has-fblocks')
-
-    def configure_objc_arc(self):
-        cxx = copy.deepcopy(self.cxx)
-        cxx.source_lang = 'objective-c++'
-        if cxx.hasCompileFlag('-fobjc-arc'):
-            self.config.available_features.add('has-fobjc-arc')
-
     def configure_modules(self):
         modules_flags = ['-fmodules']
         if not self.target_info.is_darwin():

libcxx/utils/libcxx/test/features.py

@@ -0,0 +1,30 @@
+#===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===----------------------------------------------------------------------===##
+
+from libcxx.test.dsl import *
+import sys
+
+features = [
+  Feature(name='fcoroutines-ts', compileFlag='-fcoroutines-ts',
+          when=lambda cfg: hasCompileFlag(cfg, '-fcoroutines-ts') and
+                           featureTestMacros(cfg, flags='-fcoroutines-ts').get('__cpp_coroutines', 0) >= 201703),
+
+  Feature(name='thread-safety',                 when=lambda cfg: hasCompileFlag(cfg, '-Werror=thread-safety'), compileFlag='-Werror=thread-safety'),
+  Feature(name='has-fblocks',                   when=lambda cfg: hasCompileFlag(cfg, '-fblocks')),
+  Feature(name='-fsized-deallocation',          when=lambda cfg: hasCompileFlag(cfg, '-fsized-deallocation')),
+  Feature(name='-faligned-allocation',          when=lambda cfg: hasCompileFlag(cfg, '-faligned-allocation')),
+  Feature(name='fdelayed-template-parsing',     when=lambda cfg: hasCompileFlag(cfg, '-fdelayed-template-parsing')),
+  Feature(name='libcpp-no-if-constexpr',        when=lambda cfg: '__cpp_if_constexpr' not in featureTestMacros(cfg)),
+  Feature(name='libcpp-no-structured-bindings', when=lambda cfg: '__cpp_structured_bindings' not in featureTestMacros(cfg)),
+  Feature(name='libcpp-no-deduction-guides',    when=lambda cfg: featureTestMacros(cfg).get('__cpp_deduction_guides', 0) < 201611),
+  Feature(name='libcpp-no-concepts',            when=lambda cfg: featureTestMacros(cfg).get('__cpp_concepts', 0) < 201811),
+  Feature(name='has-fobjc-arc',                 when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc') and
+                                                                 sys.platform.lower().strip() == 'darwin'), # TODO: this doesn't handle cross-compiling to Apple platforms.
+  Feature(name='objective-c++',                 when=lambda cfg: hasCompileFlag(cfg, '-xobjective-c++ -fobjc-arc')),
+  Feature(name='diagnose-if-support',           when=lambda cfg: hasCompileFlag(cfg, '-Wuser-defined-warnings'), compileFlag='-Wuser-defined-warnings'),
+]