Build the Apple-style stage2 with modules and full debug info

[aprantl]

Summary

Green dragon had a green stage2 modules bot for a long time now[1] and it is time to retire it and make a modules build the default for Apple-style stage2 builds.

This patch turns on LLVM_ENABLE_MODULES and switches the debug info generation from -gline-tables-only to -g since full debug info does no longer cause any memory issues even for full LTO builds [2].

[1] http://green.lab.llvm.org/green/job/clang-stage2-cmake-modulesRDA_build/
[2] http://llvm.org/devmtg/2015-10/#talk19
rdar://problem/28672159

[aprantl]

@beanz: Would sorting all these set() commands alphabetically break anything?

[beanz]

SWEET! this is great to see! One small comment inline, otherwise LGTM.

cmake/caches/Apple-stage2.cmake

33

Alternatively you can just remove these two lines because you're just setting this to the default value. It was only overridden to set line-tables-only.

[aprantl]

Address review feedback.

[dexonsmith]

(Both changes SGTM, but I doubt you're looking for my advice on the CMake logic.)

cmake/caches/Apple-stage2.cmake

31–32

It would simplify fallout, reverting, triaging issues, understanding compile time impact, etc., if the debug info change was left for a separate commit (maybe waiting a day). Thoughts?

[aprantl]

It would simplify fallout, reverting, triaging issues, understanding compile time impact, etc., if the debug info change was left for a separate commit (maybe waiting a day). Thoughts?

Sounds like a good plan.

cmake/caches/Apple-stage2.cmake

 # This file sets up a CMakeCache for Apple-style stage2 bootstrap. It is
 # specified by the stage1 build.
 
 set(LLVM_TARGETS_TO_BUILD X86 ARM AArch64 CACHE STRING "") 
 set(PACKAGE_VENDOR Apple CACHE STRING "")
 set(CLANG_VENDOR_UTI com.apple.clang CACHE STRING "")
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
 set(LLVM_TOOL_CLANG_TOOLS_EXTRA_BUILD OFF CACHE BOOL "")
 set(CLANG_TOOL_SCAN_BUILD_BUILD OFF CACHE BOOL "")
 set(CLANG_TOOL_SCAN_VIEW_BUILD OFF CACHE BOOL "")
 set(CLANG_LINKS_TO_CREATE clang++ cc c++ CACHE STRING "")
 set(CMAKE_MACOSX_RPATH ON CACHE BOOL "")
 set(LLVM_ENABLE_ZLIB ON CACHE BOOL "")
 set(LLVM_ENABLE_BACKTRACES OFF CACHE BOOL "")
+set(LLVM_ENABLE_MODULES ON CACHE BOOL "")
 set(LLVM_EXTERNALIZE_DEBUGINFO ON CACHE BOOL "")
 set(CLANG_PLUGIN_SUPPORT OFF CACHE BOOL "")
 set(BUG_REPORT_URL "http://developer.apple.com/bugreporter/" CACHE STRING "")
 
 set(LLVM_BUILD_EXTERNAL_COMPILER_RT ON CACHE BOOL "Build Compiler-RT with just-built clang")
 set(COMPILER_RT_ENABLE_IOS ON CACHE BOOL "Build iOS Compiler-RT libraries")
 
 set(LLVM_CREATE_XCODE_TOOLCHAIN ON CACHE BOOL "Generate targets to create and install an Xcode compatable toolchain")
 
 # Make unit tests (if present) part of the ALL target
 set(LLVM_BUILD_TESTS ON CACHE BOOL "")
 
 set(LLVM_ENABLE_LTO ON CACHE BOOL "")
 set(CMAKE_C_FLAGS "-fno-stack-protector -fno-common -Wno-profile-instr-unprofiled" CACHE STRING "")
 set(CMAKE_CXX_FLAGS "-fno-stack-protector -fno-common -Wno-profile-instr-unprofiled" CACHE STRING "")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -gline-tables-only -DNDEBUG" CACHE STRING "")
+set(CMAKE_C_FLAGS_RELWITHDEBINFO "-O2 -g -DNDEBUG" CACHE STRING "")
+set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "-O2 -g -DNDEBUG" CACHE STRING "")
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
 
 set(LIBCXX_INSTALL_LIBRARY OFF CACHE BOOL "")
 set(LIBCXX_INSTALL_HEADERS ON CACHE BOOL "")
 set(LIBCXX_INCLUDE_TESTS OFF CACHE BOOL "")
 set(LLVM_LTO_VERSION_OFFSET 3000 CACHE STRING "")
 
 # setup toolchain