[Tarantool-patches] [PATCH] cmake: add LTO support for building luajit
Sergey Bronnikov
sergeyb at tarantool.org
Mon May 25 15:58:27 MSK 2020
Olya,
I have reviewed patch in a branch and below my comments.
formatting issues still exist:
+ if (CMAKE_COMPILER_IS_CLANG)
+ if (${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 3.9)
+ set (luajit_cflags ${luajit_cflags} -flto=full)
+ else()
+ # ThinLTO that is both scalable and incremental
+ # due to parallel IPO, available since 3.9 and above.
+ # See http://blog.llvm.org/2016/06/thinlto-scalable-and-incremental-lto.html
+ set (luajit_cflags ${luajit_cflags} -flto=thin)
+ endif()
+ # XCode linker dynamically load libLTO.dylib to perform
+ # link-time optimization.
+ # http://lists.llvm.org/pipermail/llvm-dev/2009-November/027103.html
^^^^^^^^^^^^^^^^^^^^^^^^
+ if (NOT TARGET_OS_DARWIN)
+ # llvm-ar is just a wrapper over ar to pass --plugin= option,
+ # so that ar can understand LTO objects.
+ # See https://lists.llvm.org/pipermail/llvm-dev/2018-March/122018.html
+ set (CMAKE_AR llvm-ar)
+ endif()
+ else()
+ # GNU opts to support lto
^^^^^^^^^^^^^^^^^^^^^^
+ # Due to some problems (bugs, slow work, etc) we support LTO
+ # only for 5.0+. The same is for binutils prior to 2.27
+ # See comments in scripts/Makefile.lto in scope of
+ # the patch: https://patchwork.kernel.org/patch/10078207/
+ if (NOT ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 5.0
+ AND NOT ${linker_version} VERSION_LESS 2.27)
+ set (luajit_cflags ${luajit_cflags} -flto -fuse-linker-plugin -fno-fat-lto-objects)
+ endif()
^^^^^^^^^^^^^^^^^^^^^^
+ # gcc-ar is just a wrapper over ar to pass --plugin option
Unfortunatlely I have no minimal required version of binutils on my system
and I tested patch with ld gold (cmake -DCMAKE_LINKER=/usr/bin/ld.gold ..),
as Timur Safin advised.
How I tested:
$ mkdir build; cd build
$ make build_bundled_libs VERBOSE=1 2>&1 | tee log.txt
with commands above output in log.txt doesn't contain LTO related options
in compilation lines for luajit.
gcc 8.3.1, clang 8.0.1, CentOS 8.1.1911
Sergey
On 17:33 Tue 14 Apr , Olga Arkhangelskaia wrote:
> Fixed tabs:
>
> + # Depending of compiler we need to set appropriate llvm/gcc-ar
> lib
> + # llvm/gcc -ar is just a wrapper over ar to pass --plugin=
> option,
> + # so that ar can understand LTO objects.
>
> 14.04.2020 12:18, Igor Munkin пишет:
> > Olya,
> >
> > Thanks for the patch! I left several comments below, please consider
> > them.
> >
> > On 12.03.20, Olga Arkhangelskaia wrote:
> > > Tarantool has LTO support, however while building luajit this opt. was
> > > omitted. Patch adds necessary flag to turn it on.
> > >
> > > Minimum compiler/linker versions: clang 3.4, gcc 5.0+, ld 2.27+.
> > >
> > > Closes #3743
> > > ---
> > > Branch: OKriw/gh-3743-LuaJIT-does-not-use-LTO-with-DENABLE_LTO=ON-full-ci
> > > cmake/lto.cmake | 3 ++-
> > > cmake/luajit.cmake | 26 ++++++++++++++++++++++++++
> > > 2 files changed, 28 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/cmake/lto.cmake b/cmake/lto.cmake
> > > index 95ade75f4..9f29f3324 100644
> > > --- a/cmake/lto.cmake
> > > +++ b/cmake/lto.cmake
> > > @@ -78,7 +78,8 @@ if (NOT TARGET_OS_DARWIN)
> > > if (linker_version VERSION_LESS "2.31")
> > > message(FATAL_ERROR "ld.bfd >= 2.31 is needed for LTO")
> > > endif()
> > > - elseif(matched_gold)
> > > +
> > > + elseif(matched_gold)
> > Typo: there is a mess with whitespace above.
> >
> > However this chunk provides no changes except whitespace and newline.
> > Please drop it.
> >
> > > set(linker_version ${CMAKE_MATCH_1})
> > > message(STATUS "Found ld.gold version: ${linker_version}")
> > > diff --git a/cmake/luajit.cmake b/cmake/luajit.cmake
> > > index 072db8269..da1b4926d 100644
> > > --- a/cmake/luajit.cmake
> > > +++ b/cmake/luajit.cmake
> > > @@ -225,6 +225,32 @@ macro(luajit_build)
> > > set(luajit_xcflags ${luajit_xcflags} -D${def})
> > > endforeach()
> > > + # Add LTO option to luajit
> > > + if (CMAKE_INTERPROCEDURAL_OPTIMIZATION)
> > > + message("Setting LTO flags for building luajit")
> > > + # Clang opt to support LTO
> > > + if (CMAKE_COMPILER_IS_CLANG AND
> > > + NOT ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 3.4)
> > So, if clang toolchain is used but version is less than 3.4, then gcc
> > toolchain settings are used. It's either totally wrong or definitely
> > need to be clarified with a corresponding comment.
> >
> > Also, AFAICS LTO support for toolchain is checked via CheckIPOSupported
> > CMake module. So additional check here looks to be excess or also need
> > to be clarified.
> >
> > > + if (${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 3.9)
> > > + set(luajit_cflags ${luajit_cflags} -flto=full)
> > > + else()
> > > + set(luajit_cflags ${luajit_cflags} -flto=full)
> > > + endif()
> > I see no difference in the branches above.
> >
> > > + if (NOT TARGET_OS_DARWIN)
> > > + # Depending of compiler we need to set appropriate llvm/gcc-ar lib
> > > + set (CMAKE_AR llvm-ar)
> > What ar is used on systems different from Darwin based ones when clang
> > toolchain is used?
> >
> > > + endif()
> > > + # GNU opts to support lto
> > > + else()
> > > + #Due to some problems (bugs, slow work, etc) we support LTO only for 5.0+
> > > + #The same is for binutils prior 2.27
> > > + if (NOT ${CMAKE_CXX_COMPILER_VERSION} VERSION_LESS 5.0
> > > + AND NOT ${linker_version} VERSION_LESS 2.27)
> > > + set(luajit_cflags ${luajit_cflags} -flto -fuse-linker-plugin -fno-fat-lto-objects)
> > > + endif()
> > > + set (CMAKE_AR gcc-ar)
> > Could you please clarify why ar is set explicitly here?
> >
> > > + endif()
> > > + endif()
> > Typo: there is a mess with indent above. Unfortunately I failed to find
> > our CMake style guide, so please adjust your changes considering the
> > code nearby.
> >
> > > # Pass the same toolchain that is used for building of
> > > # tarantool itself, because tools from different toolchains
> > > # can be incompatible. A compiler and a linker are already set
> > > --
> > > 2.20.1 (Apple Git-117)
> > >
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