[lld] Revive standalone CMake build

[garious]

Summary

A little while back we boot the standalone CMake build because it was broken, overly-complex and we found that nobody was really using it. I'd like to bring it back because it makes working with the sanitizers especially fast and easy. Some sanitizers, such as ASan, don't require dependencies to be instrumented. By leaving the LLVM libraries uninstrumented and optimized, we can build just lld with instrumentation and debug symbols, and get a blazing fast sanitizer build.

This patch reintroduces the standalone build in a cleaner way than before. The code to support the standalone build is itself standalone, nicely tucked under one conditional. It's purpose is to put the build into the same context as if the LLVM build included it. This patch also adds a config file for the one #define lld depends on, so that we don't have to reach into LLVM's private build directory for its config.h.

[shankarke]

cmake/config-ix.cmake

6

why is this being reimplemented ?

[garious]

cmake/config-ix.cmake

6

Because the LLVM install directory does not offer this functionality.

[shankarke]

CMakeLists.txt

54

Does other projects too have a standalone build, I thought it was completely removed. If this is being revived should this be done for all projects ?

Please wait for Bigcheese / Nick whether we want to bring this in.

cmake/config-ix.cmake

6

should this be then added to the LLVM install directory then ? we need to keep mirroring these changes from llvm if there is a change, I think it woul d be hard to maintain.

[garious]

CMakeLists.txt

54

Yes, all other llvm projects have a standalone CMake builds.

cmake/config-ix.cmake

6

I have no strong opinion on this. I see your point, but also think the LLVM repo should minimize its public interface. My preference is to hold off on adding this to LLVM's install directory until the duplication causes a little pain. I can imagine this particular code living a long time without causing any.

[garious]

Can others please review? Thanks.

[garious]

Still waiting on a second review. @Bigcheese, @nicholas?

[garious]

Ping

[garious]

Ping

[garious]

Ping

[chandlerc]

My position remains that this isn't really that useful or worth the
maintenance burden that it brings. But I'm not really one of the primary
developers on LLD. I've just not had any trouble just enabling sanitizers
in the LLVM build to check LLD, nor have I heard complaints about this from
others.

That's why I'm silent here. If the LLD developers really want this, they
would probably show up and review it. My guess is that it doesn't solve an
important problem for them, but I can only speculate.

[garious]

Seems I'm the only one that wants this, abandoning. That's too bad. Standalone builds are really nice in component-oriented builds, especially when managing multiple build variations. Unfortunately, all my code that demonstrates this is locked inside our company. Oh well - perhaps another day.

CMakeLists.txt

+cmake_minimum_required(VERSION 2.8.12)
+
 # If we are not building as a part of LLVM, build lld as a standalone project,
 # using LLVM as an external library.
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+  project(LLD)
+
+  # Find and include LLVMConfig via either LLVM_INSTALL_DIR or CMAKE_PREFIX_PATH.
+  find_package(LLVM REQUIRED PATHS "${LLVM_INSTALL_DIR}")
+
+  include_directories(${LLVM_INCLUDE_DIRS})
+  link_directories(${LLVM_LIBRARY_DIRS})
+
+  # Use ${cmake_2_8_12_KEYWORD} intead of KEYWORD in target_link_libraries().
+  set(cmake_2_8_12_INTERFACE INTERFACE)
+  set(cmake_2_8_12_PRIVATE PRIVATE)
+  if(POLICY CMP0022)
+    cmake_policy(SET CMP0022 NEW) # automatic when 2.8.12 is required
+  endif()
 
-cmake_minimum_required(VERSION 2.8)
+  # Include the LLVM CMake modules.
+  list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
+  include(AddLLVM)
+  include(TableGen)
+  include(HandleLLVMOptions)
+
+  # All options referred to from HandleLLVMOptions have to be specified
+  # BEFORE this include, otherwise options will not be correctly set on
+  # first CMake run.
+  include(cmake/config-ix.cmake)
+
+  # LLVMConfig sets LLVM_PACKAGE_VERSION whereas LLVM's CMakeLists sets
+  # PACKAGE_VERSION.
+  set(PACKAGE_VERSION ${LLVM_PACKAGE_VERSION})
+
+  # Set global variables referenced by the LLVM modules.
+  find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+  set(LLVM_RUNTIME_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin)
+  set(LLVM_LIBRARY_OUTPUT_INTDIR ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
+  list(GET LLVM_INCLUDE_DIRS 0 LLVM_MAIN_INCLUDE_DIR)
+  list(GET LLVM_LIBRARY_DIRS 0 LLVM_LIBRARY_DIR)
+
+  # Include auto-generated headers.
+  include_directories("${CMAKE_CURRENT_BINARY_DIR}/lib/Driver")
+
+  # Define the default arguments to use with 'lit', and an option for the user
+  # to override.
+  set(LIT_ARGS_DEFAULT "-sv")
+  if (MSVC OR XCODE)
+    set(LIT_ARGS_DEFAULT "${LIT_ARGS_DEFAULT} --no-progress-bar")
+  endif()
+  set(LLVM_LIT_ARGS "${LIT_ARGS_DEFAULT}" CACHE STRING "Default options for lit")
+endif()
 
 set(LLD_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 set(LLD_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})

   ${CMAKE_CURRENT_SOURCE_DIR}/include/lld/Config/Version.inc.in
   ${CMAKE_CURRENT_BINARY_DIR}/include/lld/Config/Version.inc)
 
+# Configure the config.h file.
+configure_file(
+  ${CMAKE_CURRENT_SOURCE_DIR}/include/lld/Config/config.h.cmake
+  ${CMAKE_CURRENT_BINARY_DIR}/include/lld/Config/config.h)
 
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
   message(FATAL_ERROR "In-source builds are not allowed. CMake would overwrite "

cmake/config-ix.cmake

+# size_t must be defined before including cxxabi.h on FreeBSD 10.0.
+check_cxx_source_compiles("
+#include <stddef.h>
+#include <cxxabi.h>
+int main() { return 0; }
+" HAVE_CXXABI_H)

include/lld/Config/config.h.cmake

+/* include/lld/Config/config.h.cmake */
+
+#ifndef LLD_CONFIG_CONFIG_H
+#define LLD_CONFIG_CONFIG_H
+
+/* Define to 1 if you have the <cxxabi.h> header file. */
+#cmakedefine HAVE_CXXABI_H ${HAVE_CXXABI_H}
+
+#endif

lib/ReaderWriter/ELF/ELFLinkingContext.cpp

 #include "ELFFile.h"
 #include "OrderPass.h"
 #include "TargetHandler.h"
+#include "lld/Config/config.h"
 #include "lld/Core/Instrumentation.h"
 #include "lld/Core/SharedLibraryFile.h"
 #include "lld/Passes/RoundTripYAMLPass.h"
 #include "llvm/ADT/Triple.h"
-#include "llvm/Config/config.h"
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/FileSystem.h"

lib/ReaderWriter/MachO/MachOLinkingContext.cpp

 #include "File.h"
 #include "MachONormalizedFile.h"
 #include "MachOPasses.h"
+#include "lld/Config/config.h"
 #include "lld/Core/ArchiveLibraryFile.h"
 #include "lld/Core/PassManager.h"
 #include "lld/Core/Reader.h"

 #include "lld/Passes/RoundTripYAMLPass.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Triple.h"
-#include "llvm/Config/config.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/Host.h"

test/lit.cfg

     path = os.path.pathsep.join((llvm_tools_dir, config.environment['PATH']))
     path = os.path.pathsep.join((os.path.join(getattr(config, 'llvm_src_root', None),'test','Scripts'),path))
 
+    # Add path to FileCheck
+    lit_tools_dir = getattr(config, 'lit_tools_dir', None)
+    if lit_tools_dir:
+       path = os.path.pathsep.join((lit_tools_dir, path))
+
+    # Lastly, ensure path to lld is first in the path
+    path = os.path.pathsep.join((os.path.join(lld_obj_root,'bin'), path))
+
     config.environment['PATH'] = path
 
     llvm_libs_dir = getattr(config, 'llvm_libs_dir', None)