[libc++] Take 2: Integrate the PSTL into libc++

Summary:
This commit allows specifying LIBCXX_ENABLE_PARALLEL_ALGORITHMS when
configuring libc++ in CMake. When that option is enabled, libc++ will
assume that the PSTL can be found somewhere on the CMake module path,
and it will provide the C++17 parallel algorithms based on the PSTL
(that is assumed to be available).

The commit also adds support for running the PSTL tests as part of
the libc++ test suite.

The first attempt to commit this failed because it exposed a bug in the
tests for modules. Now that this has been fixed, it should be safe to
commit this.

Reviewers: EricWF

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits, mclow.lists, EricWF

Tags: #libc

Differential Revision: https://reviews.llvm.org/D60480

llvm-svn: 367903

libcxx/CMakeLists.txt

@@ -80,6 +80,7 @@ endif()
 option(LIBCXX_ENABLE_FILESYSTEM "Build filesystem as part of the main libc++ library"
     ${ENABLE_FILESYSTEM_DEFAULT})
 option(LIBCXX_INCLUDE_TESTS "Build the libc++ tests." ${LLVM_INCLUDE_TESTS})
+option(LIBCXX_ENABLE_PARALLEL_ALGORITHMS "Enable the parallel algorithms library. This requires the PSTL to be available." OFF)
 
 # Benchmark options -----------------------------------------------------------
 option(LIBCXX_INCLUDE_BENCHMARKS "Build the libc++ benchmarks and their dependencies" ON)
@@ -745,6 +746,7 @@ config_define_if(LIBCXX_HAS_WIN32_THREAD_API _LIBCPP_HAS_THREAD_API_WIN32)
 config_define_if(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL)
 config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
 config_define_if(LIBCXX_NO_VCRUNTIME _LIBCPP_NO_VCRUNTIME)
+config_define_if(LIBCXX_ENABLE_PARALLEL_ALGORITHMS _LIBCPP_HAS_PARALLEL_ALGORITHMS)
 
 if (LIBCXX_ABI_DEFINES)
   set(abi_defines)

libcxx/include/CMakeLists.txt

@@ -62,6 +62,7 @@ set(files
   deque
   errno.h
   exception
+  execution
   experimental/__config
   experimental/__memory
   experimental/algorithm

libcxx/include/__config_site.in

@@ -29,6 +29,7 @@
 #cmakedefine _LIBCPP_NO_VCRUNTIME
 #cmakedefine01 _LIBCPP_HAS_MERGED_TYPEINFO_NAMES_DEFAULT
 #cmakedefine _LIBCPP_ABI_NAMESPACE @_LIBCPP_ABI_NAMESPACE@
+#cmakedefine _LIBCPP_HAS_PARALLEL_ALGORITHMS
 
 @_LIBCPP_ABI_DEFINES@
 

libcxx/include/algorithm

@@ -5678,4 +5678,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <pstl/internal/glue_algorithm_impl.h>
+#endif
+
 #endif  // _LIBCPP_ALGORITHM

libcxx/include/execution

@@ -0,0 +1,19 @@
+// -*- C++ -*-
+//===------------------------- execution ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXECUTION
+#define _LIBCPP_EXECUTION
+
+#include <__config>
+
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <pstl/internal/glue_execution_defs.h>
+#endif
+
+#endif // _LIBCPP_EXECUTION

libcxx/include/memory

@@ -5590,4 +5590,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <pstl/internal/glue_memory_impl.h>
+#endif
+
 #endif  // _LIBCPP_MEMORY

libcxx/include/module.modulemap

@@ -275,6 +275,10 @@ module std [system] {
     header "exception"
     export *
   }
+  module execution {
+    header "execution"
+    export *
+  }
   module filesystem {
     header "filesystem"
     export *

libcxx/include/numeric

@@ -586,4 +586,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <pstl/internal/glue_numeric_impl.h>
+#endif
+
 #endif  // _LIBCPP_NUMERIC

libcxx/src/CMakeLists.txt

@@ -196,6 +196,10 @@ function(cxx_link_system_libraries target)
   endif()
 endfunction()
 
+if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS AND NOT TARGET pstl::ParallelSTL)
+  message(FATAL_ERROR "Could not find ParallelSTL")
+endif()
+
 function(cxx_set_common_defines name)
   if(LIBCXX_CXX_ABI_HEADER_TARGET)
     add_dependencies(${name} ${LIBCXX_CXX_ABI_HEADER_TARGET})
@@ -222,6 +226,10 @@ function(cxx_set_common_defines name)
                                  # in printf, scanf.
                                  _CRT_STDIO_ISO_WIDE_SPECIFIERS)
   endif()
+
+  if (LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
+    target_link_libraries(${name} PUBLIC pstl::ParallelSTL)
+  endif()
 endfunction()
 
 split_list(LIBCXX_COMPILE_FLAGS)

libcxx/test/CMakeLists.txt

@@ -40,6 +40,7 @@ pythonize_bool(LIBCXX_HAS_ATOMIC_LIB)
 pythonize_bool(LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB)
 pythonize_bool(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY)
 pythonize_bool(LIBCXX_DEBUG_BUILD)
+pythonize_bool(LIBCXX_ENABLE_PARALLEL_ALGORITHMS)
 
 # By default, for non-standalone builds, libcxx and libcxxabi share a library
 # directory.

libcxx/test/libcxx/double_include.sh.cpp

@@ -63,6 +63,7 @@
 #include <deque>
 #include <errno.h>
 #include <exception>
+#include <execution>
 #include <fenv.h>
 #include <filesystem>
 #include <float.h>

libcxx/test/lit.site.cfg.in

@@ -33,6 +33,7 @@ config.use_libatomic            = @LIBCXX_HAVE_CXX_ATOMICS_WITH_LIB@
 config.debug_build              = @LIBCXX_DEBUG_BUILD@
 config.libcxxabi_shared         = @LIBCXXABI_ENABLE_SHARED@
 config.cxx_ext_threads          = @LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY@
+config.pstl_root                = "@ParallelSTL_SOURCE_DIR@" if @LIBCXX_ENABLE_PARALLEL_ALGORITHMS@ else None
 
 # Let the main config do the real work.
 config.loaded_site_config = True

libcxx/test/std/pstl

@@ -0,0 +1 @@
+../../../pstl/test/std

libcxx/utils/libcxx/test/config.py

@@ -581,6 +581,13 @@ class Configuration(object):
         support_path = os.path.join(self.libcxx_src_root, 'test/support')
         self.cxx.compile_flags += ['-I' + support_path]
 
+        # Add includes for the PSTL headers
+        pstl_root = self.get_lit_conf('pstl_root')
+        if pstl_root is not None:
+            self.cxx.compile_flags += ['-I' + os.path.join(pstl_root, 'include')]
+            self.cxx.compile_flags += ['-I' + os.path.join(pstl_root, 'test')]
+            self.config.available_features.add('parallel-algorithms')
+
         # FIXME(EricWF): variant_size.pass.cpp requires a slightly larger
         # template depth with older Clang versions.
         self.cxx.addFlagIfSupported('-ftemplate-depth=270')

libcxxabi/src/CMakeLists.txt

@@ -147,6 +147,10 @@ if (LLVM_ENABLE_MODULES)
   string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
 endif()
 
+if (NOT TARGET pstl::ParallelSTL)
+  message(STATUS "Could not find ParallelSTL, libc++abi will not attempt to use it but the build may fail if the libc++ in use needs it to be available.")
+endif()
+
 if ("${CMAKE_OSX_ARCHITECTURES}" MATCHES "^(armv6|armv7|armv7s)$")
   set(LIBCXXABI_USE_SJLJ_EXCEPTIONS ON)
 else()
@@ -160,6 +164,9 @@ if (LIBCXXABI_ENABLE_SHARED)
     llvm_setup_rpath(cxxabi_shared)
   endif()
   target_link_libraries(cxxabi_shared PRIVATE ${LIBCXXABI_SHARED_LIBRARIES} ${LIBCXXABI_LIBRARIES})
+  if (TARGET pstl::ParallelSTL)
+    target_link_libraries(cxxabi_shared PUBLIC pstl::ParallelSTL)
+  endif()
   set_target_properties(cxxabi_shared
                         PROPERTIES
                           CXX_EXTENSIONS
@@ -208,6 +215,9 @@ endif()
 if (LIBCXXABI_ENABLE_STATIC)
   add_library(cxxabi_static STATIC ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
   target_link_libraries(cxxabi_static PRIVATE ${LIBCXXABI_STATIC_LIBRARIES} ${LIBCXXABI_LIBRARIES})
+  if (TARGET pstl::ParallelSTL)
+    target_link_libraries(cxxabi_static PUBLIC pstl::ParallelSTL)
+  endif()
   set_target_properties(cxxabi_static
                         PROPERTIES
                           CXX_EXTENSIONS

llvm/projects/CMakeLists.txt

@@ -30,8 +30,8 @@ if(${LLVM_BUILD_RUNTIME})
     # Add the projects in reverse order of their dependencies so that the
     # dependent projects can see the target names of their dependencies.
     add_llvm_external_project(libunwind)
-    add_llvm_external_project(libcxxabi)
     add_llvm_external_project(pstl)
+    add_llvm_external_project(libcxxabi)
     add_llvm_external_project(libcxx)
   endif()
   if(NOT LLVM_BUILD_EXTERNAL_COMPILER_RT)

pstl/test/std/lit.local.cfg

@@ -0,0 +1,2 @@
+if 'parallel-algorithms' not in config.available_features:
+    config.unsupported = True