llvm dev - Jun 2016 - [RFC] LLVM Directory Structure Changes (was Re: [PATCH] D20992: [CMake] Add LLVM runtimes directory)

Hey Ben,

Thank you for providing this feedback. I’m going to lay out some ideas that I
have inline below.
> On Jun 9, 2016, at 11:26 AM, Craig, Ben via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> I'm great with moving the runtimes into their own directory and making
cmake modules to standardize an interface between the LLVM build process and the
runtime build process.  I would like to ask for more though.
> 
> I find working with the runtimes a bit frustrating at times, and I think a
lot of that frustration stems from the second-class nature of the runtime build
process.  The "best" way to build just the runtimes today is to clone
them in the llvm tree, pass a very long cmake line, then run a very specific
make / ninja line (i.e. ninja cxx, ninja check-libcxxabi).  This is even the
case if I don't want to use the freshly generated compiler.  Here are some
specific nuisances that running in-tree has caused me:
> 
> 
Agree on all points. It might be useful to provide an alternate top-level CMake
file for runtime projects. There is some complication because the runtimes do
use CMake modules from LLVM, so you’ll need either an LLVM checkout or a built
& installed LLVM. My general hope in formalizing a runtimes directory is to
start treating runtimes as first-class members of the LLVM project. Admittedly
I’m coming from a different perspective than you, so I’m tackling the "LLVM
& Clang developer who also wants runtimes” side of the problem. I am,
however, sympathetic to your side too.
> I routinely need to pull a new LLVM for new cmake files, even though I am
not building LLVM.
Some of this may be avoidable through restructuring our CMake modules. I think
we should discuss this separately from the changes I’m asking for, but my
general idea is it might be reasonable to create a separate LLVM repository that
stores common CMake modules. If we did that it would require that *everyone*
building LLVM would need to have those modules. We may be able to hide that
complexity using CMake’s ExternalProject stuff. I’ll take it as a line item to
look into that.
> I don't get to use "standard" commands to build and test the
components I work with.  I want to just run make / ninja with no arguments, but
instead, I need to build specific targets.
This is the kind of thing I see as potentially solvable with a separate
top-level CMake file for runtimes. That said, in general I’ve been moving toward
adding more and more explicit targets into CMake. As a result of that my natural
workflow is involving less and less running general commands and more and more
running specific “ninja <some tool>” and “ninja check-llvm-<some test
set>”.
> Choices made for LLVM's build end up affecting mine, and I don't
have a good way to change them.  For example, I wanted to perform some libcxx
builds without -Wl,-z,defs.  I had to do some wacky string filtering to remove
it from the compile line after the fact, instead of preventing it from getting
added in the first place.  There wasn't a flag available on the LLVM side to
disable it at configure time.
LLVM’s flags impacting libcxx is fixed by my runtimes proposal. In fact, that’s
part of the point. Bleeding options from LLVM & Clang builds into runtime
libraries is not cool. It causes lots of problems on Darwin, so we’re sensitive
to this.
> To get cmake to work, I have to set HAVE_CXX_ATOMICS_WITHOUT_LIB, even
though I have no intention of building LLVM.  I then get to set
LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB too, because reasons.
This is bad. I’m curious why you need to set those ever. Have you diagnosed
this? For you to need to set that it means the host toolchain isn’t properly
passing the CMake checks.
> Multi-libs require multiple independent build directories, with all the
associated cmake overhead.
I strongly believe that for building multi-lib or more generally when building
for multiple targets you want multiple build directories, and in particular the
multiple-cmake invocations. I believe this because you want the checks to be
relevant for the target, and the only way to do that is to run the checks once
per target.

That said, I also strongly believe that for any user of our projects we should
find a way to have a single simple CMake invocation that gets the end result
that you want. I don’t believe these are mutually exclusive goals.

One of the development steps of the new runtime directory will be supporting
specifying multiple targets to build the runtimes for, and having CMake
construct the appropriate number of build directories and manage building them
all through a single top-level configuration and build directory. If you’re
skeptical about how doable this is I’d encourage you to look at this bot ->
http://lab.llvm.org:8011/builders/clang-3stage-ubuntu.

That bot does a full 3-stage clang build from a single CMake invocation:

cmake -C ../llvm.src/tools/clang/cmake/caches/3-stage.cmake -GNinja
-DLLVM_TARGETS_TO_BUILD=all -DLLVM_BINUTILS_INCDIR=/opt/binutils/include
../llvm.src
> So why not run out of tree instead you may ask?
> 
> No lit tests or lit utilities (FileCheck, not, etc…)
I don’t know if the runtimes you’re building are setup for this or not, but you
can get out-of-tree tests working if you have an LLVM installation on the system
or a build directory that you can point at. Compiler-RT does this. It isn’t
ideal but it is workable.

We should have a better solution.
> Even more difficult to manage dependencies between libcxxabi and libcxx
Yep. That sucks.
> So some things I would like to see...
> 
> Standalone runtime builds should use the "normal" build
interfaces (bare make, make all, make check, make install.  s/make/ninja as
desired).
I think this is doable, but I’m hesitant to rope it in with what I’m trying to
do here. Nothing I want to do would prevent this or make it any harder than it
already is.
> For in-tree builds, LLVM would use the new cmake ExternalProject feature. 
This way LLVM's in-tree support could be implemented in terms of the
runtime's "normal" build interfaces.  LLVM may also define a
refinement of that interface to provide extra LLVM information on top.
> For example, maybe all llvm runtime projects get passed something like
LLVM_RUNTIME_LIBCXXABI_PRESENT and LLVM_RUNTIME_LIBCXXABI_PATH, and those
projects can act on that or not.
Yes, there will need to be a mechanism for communicating project dependencies
between runtimes.
> Developers using standalone builds can use the same "LLVM build"
interface as the in-tree builds use.
Yes. I’ve actually been having some hallway conversations about how to
standardize the build interface a bit more cleanly. Some of this will depend on
a per-project basis, but I think compiler-rt does some of this right today.

Specifically if an LLVM build tree is available it builds as if it were in-tree
and being distributed with that build. If the LLVM build tree isn’t available,
it builds in a more standard *nix format that would be compatible with non-LLVM
toolchains. I may be wrong, but I think that is probably the right behavior for
all our runtimes.
> Break out testing infrastructure to a common repo, so that the runtimes can
have access to the testing "banana" without dragging along the LLVM
"gorilla”.
I’m hesitant to suggest more and more repos because I think there are some
challenges and additional burdens with that. I do understand the benefit of what
you’re asking for here, and I think it is worth considering. I think there is an
argument for splitting out the LLVM testing infrastructure, as well as an
argument for splitting out the LLVM build infrastructure.

In both cases I think those changes are larger than what I’m proposing, but
worth considering.

-Chris

Obligatory troll: Maybe we should move to github and change the whole repo
structure in the process?
> 
> On 6/9/2016 12:20 PM, Chris Bieneman via llvm-dev wrote:
>> Moving to llvm-dev (I think this has gone a bit further than a patch
review discussion)
>> 
>> In hindsight I probably should have explained more of my thinking on
this with the patch, or done an RFC on llvm-dev to start with. I’l do that now,
and answer the questions along the way. I sent a separate email discussing
Justin’s patch review feedback.
>> 
>> In the build system today there is no strong distinction between
‘projects’ and ‘tools’. There are a few subtle differences, but I’m not sure any
of them really matter. The differences are:
>> 
>> (1) The projects directory is always configured, tools can be disabled
using LLVM_INCLUDE_TOOLS=Off (projects and tools can both be individually
disabled too)
>> (2) Projects are configured before tools, so tools can rely on targets
being created for projects (we don’t really use this, and anywhere we are is
probably a bug)
>> (3) Some projects have special handling. For example test-suite isn’t
actually treated as a project, it has special handling in
LLVM/CMakeLists.txt:727, and Compiler-RT is handled by clang if you set
LLVM_BUILD_EXTERNAL_COMPILER_RT=On.
>> 
>> With this in mind I was thinking about the general usability of our
build system. The distinction between a project         and a tool is not very
clear. At a high level I see three different use cases that are covered by our
current projects & tools directories.
>> 
>> (1) Projects that are configured with LLVM
>> (2) Runtime projects that should be configured using the just-built
tools
>> (3) The LLVM test-suite, which is really just external tests that
should be configured and run with the just-built tools
>> 
>> My proposal is that we make the tools subdirectory the *only* place for
projects that fall into category 1. I don’t think there is any technical reason
to drop an in-tree project into projects over tools today, and I think we
migrating people who are doing that away from it should be easy.
>> 
>> Second I want to add a “runtimes” directory to LLVM to cover case 2
(see D20992). The idea behind this is to use common code in LLVM to support
building runtimes. This will allow the full LLVM toolchain to be visible during
configuration. I will abstract this functionality into an installed CMake module
so that Clang can use it for out-of-tree clang builds.
>> 
>> Lastly we need to give the test-suite a new home. I’m not super
concerned with where we do that. It could be under tests, it could just be at
the root of the LLVM directory. I don’t think it matters too much because it is
a one-off. Thoughts welcome.
>> 
>> My proposed patch makes the runtimes directory work for Compiler-RT,
but it doesn’t yet handle libcxxabi, libcxx and libunwind. There is some special
case handling between libcxxabi and libcxx that will need to be handled to make
the dependencies work between the two, and I still need to work that out.
>> 
>> If we want to go with this proposal I envision the transition being
multi-staged:
>> 
>> (1) Adding the new functionality, getting it up and fully working for
all runtime projects - this will involve changes to runtime projects
>> (2) Work with bot maintainers to migrate bots, and fix any issues that
come up
>> (3) Add support for a new secondary location for the test-suite
>> (4) Set a date for removing the projects directory, post patches
including updated documentation
>> (5) Remove the projects directory entirely
>> 
>> Thoughts?
>> -Chris
>> 
>>> On Jun 8, 2016, at 6:59 PM, Chandler Carruth <chandlerc at
gmail.com <mailto:chandlerc at gmail.com>> wrote:
>>> 
>>> On Wed, Jun 8, 2016 at 4:39 PM Justin Bogner via llvm-commits <
<mailto:llvm-commits at lists.llvm.org>llvm-commits at lists.llvm.org
<mailto:llvm-commits at lists.llvm.org>> wrote:
>>> Chris Bieneman <beanz at apple.com <mailto:beanz at
apple.com>> writes:
>>> > beanz created this revision.
>>> > beanz added reviewers: chandlerc, bogner.
>>> > beanz added a subscriber: llvm-commits.
>>> >
>>> > There are a few LLVM projects that produce runtime libraries.
Ideally
>>> > runtime libraries should be built differently than other
projects,
>>> > specifically they should be built using the just-built
toolchain.
>>> >
>>> > There is support for building compiler-rt in this way from the
clang
>>> > build. Moving this logic into the LLVM build is interesting
because it
>>> > provides a simpler way to extend the just-built toolchain to
include
>>> > LLD and the LLVM object file tools.
>>> >
>>> > Once this functionality is better fleshed out and tested we’ll
want to
>>> > encapsulate it in a module that can be used for clang
standalone
>>> > builds, and we’ll want to make it the default way to build
compiler-rt.
>>> >
>>> > With this patch applied there is no immediate change in the
build.
>>> > Moving compiler-rt out from llvm/projects into llvm/runtimes
enables
>>> > the functionality.
>>> 
>>> This seems reasonable, but I am a little worried about how
transitioning
>>> to the new system will work. Will everyone have to move their
>>> compiler-rt checkout? Will we continue to support compiler-rt in
either
>>> place? Both of these are workable, but neither is great. Thoughts?
>>> 
>>> I share your concerns, but I also kind of like the direction this
is going.
>>> 
>>> But there is a higher-level meta-point: do we want to keep the
'projects' directory *at all*.
>>> 
>>> Every single resident of it I can think of except for the
test-suite is either dead (dragonegg) or a runtime library.
>>> 
>>> I think we should either have all the build-integrated projects in
a single 'projects' directory (including LLD and Clang), or we should
have none of them and use more domain relevant organization (today
"tools", you're adding "runtimes", maybe we move the
test-suite to go under one of the test directories).
>>> 
>>> I think we should have a consistent plan here before moving stuff.
But once we have it, I think we shouldn't be afraid of re-organizing stuff
to make more sense, and just work to get folks to update their checkouts.
>>> 
>>> -Chandler
>>>  
>>> 
>>> > This code has a few improvements over the method provided by
>>> > LLVM_BUILD_EXTERNAL_COMPILER_RT. Specifically the sub-ninja
command is
>>> > always invoked, so changes to compiler-rt source files will
get built
>>> > properly, so this patch can be used for iterative development
with
>>> > just-built tools.
>>> >
>>> > 
<http://reviews.llvm.org/D20992>http://reviews.llvm.org/D20992
<http://reviews.llvm.org/D20992>
>>> >
>>> > Files:
>>> >   CMakeLists.txt
>>> >   cmake/modules/LLVMExternalProjectUtils.cmake
>>> >   runtimes/CMakeLists.txt
>>> >
>>> > Index: runtimes/CMakeLists.txt
>>> >
==================================================================>>>
> --- /dev/null
>>> > +++ runtimes/CMakeLists.txt
>>> > @@ -0,0 +1,16 @@
>>> > +include(LLVMExternalProjectUtils)
>>> > +
>>> > +# Discover the projects that use CMake in the subdirectories.
>>> > +# Note that explicit cmake invocation is required every time
a new project is
>>> > +# added or removed.
>>> > +
>>> > +add_custom_target(runtimes)
>>> > +
>>> > +file(GLOB entries *)
>>> > +foreach(entry ${entries})
>>> > +  if(IS_DIRECTORY ${entry} AND EXISTS
${entry}/CMakeLists.txt)
>>> > +    get_filename_component(projName ${entry} NAME)
>>> > +    llvm_ExternalProject_Add(${projName} ${entry}
USE_TOOLCHAIN)
>>> > +    add_dependencies(runtimes ${projName})
>>> > +  endif()
>>> > +endforeach(entry)
>>> > Index: cmake/modules/LLVMExternalProjectUtils.cmake
>>> >
==================================================================>>>
> --- cmake/modules/LLVMExternalProjectUtils.cmake
>>> > +++ cmake/modules/LLVMExternalProjectUtils.cmake
>>> > @@ -29,7 +29,8 @@
>>> >  #     Extra targets in the subproject to generate targets for
>>> >  #   )
>>> >  function(llvm_ExternalProject_Add name source_dir)
>>> > -  cmake_parse_arguments(ARG
"USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL"
>>> > +  cmake_parse_arguments(ARG
>>> > +   
"USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL;ALWAYS_CLEAN"
>>> >      "SOURCE_DIR"
>>> >     
"CMAKE_ARGS;TOOLCHAIN_TOOLS;RUNTIME_LIBRARIES;DEPENDS;EXTRA_TARGETS"
${ARGN})
>>> >    canonicalize_tool_name(${name} nameCanon)
>>> > @@ -52,6 +53,10 @@
>>> >      endif()
>>> >    endforeach()
>>> >
>>> > +  if(ARG_ALWAYS_CLEAN)
>>> > +    set(always_clean clean)
>>> > +  endif()
>>> > +
>>> >    list(FIND TOOLCHAIN_TOOLS clang FOUND_CLANG)
>>> >    if(FOUND_CLANG GREATER -1)
>>> >      set(CLANG_IN_TOOLCHAIN On)
>>> > @@ -135,6 +140,14 @@
>>> >      CMAKE_ARGS ${${nameCanon}_CMAKE_ARGS}
>>> >                 ${compiler_args}
>>> >                 -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
>>> > +              
-DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
>>> > +              
-DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_OUTPUT_INTDIR}
>>> > +              
-DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
>>> > +               -DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
>>> > +               -DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
>>> > +               -DPACKAGE_VERSION=${PACKAGE_VERSION}
>>> > +               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
>>> > +               -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
>>> 
>>> How did you decide which variables need to be passed through like
this?
>>> The set seems somewhat arbitrary, but I may be missing something
>>> obvious.
>>> 
>>> >                 ${ARG_CMAKE_ARGS}
>>> >                 ${PASSTHROUGH_VARIABLES}
>>> >      INSTALL_COMMAND ""
>>> > @@ -152,7 +165,7 @@
>>> >      ExternalProject_Add_Step(${name} force-rebuild
>>> >        COMMAND ${run_build}
>>> >        COMMENT "Forcing rebuild of ${name}"
>>> > -      DEPENDEES configure clean
>>> > +      DEPENDEES configure ${always_clean}
>>> 
>>> I'm not sure I understand what this does. If I had to guess
I'd say that
>>> when ALWAYS_CLEAN is passed the rebuild of the external project
always
>>> invokes clean first, but if it's not passed we'll just
invoke the
>>> external build and allow it to be incremental if appropriate. Is
that
>>> right?
>>> 
>>> >        DEPENDS ${ALWAYS_REBUILD} ${ARG_DEPENDS}
${TOOLCHAIN_BINS}
>>> >        ${cmake_3_4_USES_TERMINAL} )
>>> >    endif()
>>> > Index: CMakeLists.txt
>>> >
==================================================================>>>
> --- CMakeLists.txt
>>> > +++ CMakeLists.txt
>>> > @@ -720,6 +720,8 @@
>>> >    add_subdirectory(tools)
>>> >  endif()
>>> >
>>> > +add_subdirectory(runtimes)
>>> > +
>>> >  if( LLVM_INCLUDE_EXAMPLES )
>>> >    add_subdirectory(examples)
>>> >  endif()
>>> > @@ -730,7 +732,8 @@
>>> >      llvm_ExternalProject_Add(test-suite
${LLVM_MAIN_SRC_DIR}/projects/test-suite
>>> >        USE_TOOLCHAIN
>>> >        EXCLUDE_FROM_ALL
>>> > -      NO_INSTALL)
>>> > +      NO_INSTALL
>>> > +      ALWAYS_CLEAN)
>>> >    endif()
>>> >    add_subdirectory(test)
>>> >    add_subdirectory(unittests)
>>> >
>>> 
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org <mailto:llvm-commits at
lists.llvm.org>
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> 
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>>   * To get cmake to work, I have to set HAVE_CXX_ATOMICS_WITHOUT_LIB,
>>     even though I have no intention of building LLVM.  I then get to
>>     set LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB too, because reasons.
>>
> This is bad. I’m curious why you need to set those ever. Have you 
> diagnosed this? For you to need to set that it means the host 
> toolchain isn’t properly passing the CMake checks.
It looks like I don't need to set these anymore, but the comment that I 
left myself at the time was that HAVE_CXX_ATOMICS_WITHOUT_LIB looked at 
the state of my local machine's toolchain, as opposed to the toolchain 
that I was about to use.  My local machine's toolchain is gcc 4.6.3, and 
it doesn't have an <atomic> header.
>>   * Multi-libs require multiple independent build directories, with
>>     all the associated cmake overhead.
>>
> I strongly believe that for building multi-lib or more generally when 
> building for multiple targets you want multiple build directories, and 
> in particular the multiple-cmake invocations. I believe this because 
> you want the checks to be relevant for the target, and the only way to 
> do that is to run the checks once per target.
>
> That said, I also strongly believe that for any user of our projects 
> we should find a way to have a single simple CMake invocation that 
> gets the end result that you want. I don’t believe these are mutually 
> exclusive goals.
>
> One of the development steps of the new runtime directory will be 
> supporting specifying multiple targets to build the runtimes for, and 
> having CMake construct the appropriate number of build directories and 
> manage building them all through a single top-level configuration and 
> build directory. If you’re skeptical about how doable this is I’d 
> encourage you to look at this bot -> 
> http://lab.llvm.org:8011/builders/clang-3stage-ubuntu.
>
> That bot does a full 3-stage clang build from a single CMake invocation:
>
> cmake -C ../llvm.src/tools/clang/cmake/caches/3-stage.cmake -GNinja 
> -DLLVM_TARGETS_TO_BUILD=all 
> -DLLVM_BINUTILS_INCDIR=/opt/binutils/include ../llvm.src
>
I'm fine if I can invoke cmake once and get multiple library variants 
out.  If that means that behind-the-scenes, cmake has multiple build 
sub-directories, then that's fine by me.  On Windows, this already 
happens to some degree, as the Visual Studio project is allowed to 
switch between Release, Debug, RelWithDebInfo, etc without re-running cmake.
>> So why not run out of tree instead you may ask?
>>
>>   * No lit tests or lit utilities (FileCheck, not, etc…)
>>
> I don’t know if the runtimes you’re building are setup for this or 
> not, but you can get out-of-tree tests working if you have an LLVM 
> installation on the system or a build directory that you can point at. 
> Compiler-RT does this. It isn’t ideal but it is workable.
>
> We should have a better solution.
The nightly builds that my organization produces is generally a 
"customer build", and not a "developer build".  Stated
otherwise, it
doesn't include llvm-config, libclang.a, or any of the other things that 
people building against llvm would want.  That means that if I wanted to 
use this particular out-of-tree solution, I would still need to clone 
down LLVM and rebuild and reinstall it on occasion.
>> So some things I would like to see...
>>
>>   * Standalone runtime builds should use the "normal" build
>>     interfaces (bare make, make all, make check, make install. 
>>     s/make/ninja as desired).
>>
> I think this is doable, but I’m hesitant to rope it in with what I’m 
> trying to do here. Nothing I want to do would prevent this or make it 
> any harder than it already is.
Completely fair.  I figured I'd get my grievances and wishlist out 
first, just so that some agreement on a direction can be figured out.  
It does extend beyond the directory re-org patch.
>>   * Break out testing infrastructure to a common repo, so that the
>>     runtimes can have access to the testing "banana" without
dragging
>>     along the LLVM "gorilla”.
>>
> I’m hesitant to suggest more and more repos because I think there are 
> some challenges and additional burdens with that. I do understand the 
> benefit of what you’re asking for here, and I think it is worth 
> considering. I think there is an argument for splitting out the LLVM 
> testing infrastructure, as well as an argument for splitting out the 
> LLVM build infrastructure.
>
> In both cases I think those changes are larger than what I’m 
> proposing, but worth considering.
>
> -Chris
>
> Obligatory troll: Maybe we should move to github and change the whole 
> repo structure in the process?
I figured the github thread was crazy enough without me sabotaging it 
with this kind of suggestion :)
>>
>> On 6/9/2016 12:20 PM, Chris Bieneman via llvm-dev wrote:
>>> Moving to llvm-dev (I think this has gone a bit further than a
patch
>>> review discussion)
>>>
>>> In hindsight I probably should have explained more of my thinking
on
>>> this with the patch, or done an RFC on llvm-dev to start with. I’l 
>>> do that now, and answer the questions along the way. I sent a 
>>> separate email discussing Justin’s patch review feedback.
>>>
>>> In the build system today there is no strong distinction between 
>>> ‘projects’ and ‘tools’. There are a few subtle differences, but I’m
>>> not sure any of them really matter. The differences are:
>>>
>>> (1) The projects directory is always configured, tools can be 
>>> disabled using LLVM_INCLUDE_TOOLS=Off (projects and tools can both 
>>> be individually disabled too)
>>> (2) Projects are configured before tools, so tools can rely on 
>>> targets being created for projects (we don’t really use this, and 
>>> anywhere we are is probably a bug)
>>> (3) Some projects have special handling. For example test-suite 
>>> isn’t actually treated as a project, it has special handling in 
>>> LLVM/CMakeLists.txt:727, and Compiler-RT is handled by clang if you
>>> set LLVM_BUILD_EXTERNAL_COMPILER_RT=On.
>>>
>>> With this in mind I was thinking about the general usability of our
>>> build system. The distinction between a project and a tool is not 
>>> very clear. At a high level I see three different use cases that
are
>>> covered by our current projects & tools directories.
>>>
>>> (1) Projects that are configured with LLVM
>>> (2) Runtime projects that should be configured using the just-built
>>> tools
>>> (3) The LLVM test-suite, which is really just external tests that 
>>> should be configured and run with the just-built tools
>>>
>>> My proposal is that we make the tools subdirectory the *only* place
>>> for projects that fall into category 1. I don’t think there is any 
>>> technical reason to drop an in-tree project into projects over
tools
>>> today, and I think we migrating people who are doing that away from
>>> it should be easy.
>>>
>>> Second I want to add a “runtimes” directory to LLVM to cover case 2
>>> (see D20992). The idea behind this is to use common code in LLVM to
>>> support building runtimes. This will allow the full LLVM toolchain 
>>> to be visible during configuration. I will abstract this 
>>> functionality into an installed CMake module so that Clang can use 
>>> it for out-of-tree clang builds.
>>>
>>> Lastly we need to give the test-suite a new home. I’m not super 
>>> concerned with where we do that. It could be under tests, it could 
>>> just be at the root of the LLVM directory. I don’t think it matters
>>> too much because it is a one-off. Thoughts welcome.
>>>
>>> My proposed patch makes the runtimes directory work for
Compiler-RT,
>>> but it doesn’t yet handle libcxxabi, libcxx and libunwind. There is
>>> some special case handling between libcxxabi and libcxx that will 
>>> need to be handled to make the dependencies work between the two, 
>>> and I still need to work that out.
>>>
>>> If we want to go with this proposal I envision the transition being
>>> multi-staged:
>>>
>>> (1) Adding the new functionality, getting it up and fully working 
>>> for all runtime projects - this will involve changes to runtime
projects
>>> (2) Work with bot maintainers to migrate bots, and fix any issues 
>>> that come up
>>> (3) Add support for a new secondary location for the test-suite
>>> (4) Set a date for removing the projects directory, post patches 
>>> including updated documentation
>>> (5) Remove the projects directory entirely
>>>
>>> Thoughts?
>>> -Chris
>>>
>>>> On Jun 8, 2016, at 6:59 PM, Chandler Carruth <chandlerc at
gmail.com
>>>> <mailto:chandlerc at gmail.com>> wrote:
>>>>
>>>> On Wed, Jun 8, 2016 at 4:39 PM Justin Bogner via llvm-commits 
>>>> <llvm-commits at lists.llvm.org> wrote:
>>>>
>>>>     Chris Bieneman <beanz at apple.com <mailto:beanz at
apple.com>> writes:
>>>>     > beanz created this revision.
>>>>     > beanz added reviewers: chandlerc, bogner.
>>>>     > beanz added a subscriber: llvm-commits.
>>>>     >
>>>>     > There are a few LLVM projects that produce runtime
libraries.
>>>>     Ideally
>>>>     > runtime libraries should be built differently than
other
>>>>     projects,
>>>>     > specifically they should be built using the just-built
toolchain.
>>>>     >
>>>>     > There is support for building compiler-rt in this way
from
>>>>     the clang
>>>>     > build. Moving this logic into the LLVM build is
interesting
>>>>     because it
>>>>     > provides a simpler way to extend the just-built
toolchain to
>>>>     include
>>>>     > LLD and the LLVM object file tools.
>>>>     >
>>>>     > Once this functionality is better fleshed out and
tested
>>>>     we’ll want to
>>>>     > encapsulate it in a module that can be used for clang
standalone
>>>>     > builds, and we’ll want to make it the default way to
build
>>>>     compiler-rt.
>>>>     >
>>>>     > With this patch applied there is no immediate change
in the
>>>>     build.
>>>>     > Moving compiler-rt out from llvm/projects into
llvm/runtimes
>>>>     enables
>>>>     > the functionality.
>>>>
>>>>     This seems reasonable, but I am a little worried about how
>>>>     transitioning
>>>>     to the new system will work. Will everyone have to move
their
>>>>     compiler-rt checkout? Will we continue to support
compiler-rt
>>>>     in either
>>>>     place? Both of these are workable, but neither is great.
Thoughts?
>>>>
>>>>
>>>> I share your concerns, but I also kind of like the direction
this
>>>> is going.
>>>>
>>>> But there is a higher-level meta-point: do we want to keep the 
>>>> 'projects' directory *at all*.
>>>>
>>>> Every single resident of it I can think of except for the 
>>>> test-suite is either dead (dragonegg) or a runtime library.
>>>>
>>>> I think we should either have all the build-integrated projects
in
>>>> a single 'projects' directory (including LLD and
Clang), or we
>>>> should have none of them and use more domain relevant
organization
>>>> (today "tools", you're adding
"runtimes", maybe we move the
>>>> test-suite to go under one of the test directories).
>>>>
>>>> I think we should have a consistent plan here before moving
stuff.
>>>> But once we have it, I think we shouldn't be afraid of 
>>>> re-organizing stuff to make more sense, and just work to get
folks
>>>> to update their checkouts.
>>>>
>>>> -Chandler
>>>>
>>>>
>>>>     > This code has a few improvements over the method
provided by
>>>>     > LLVM_BUILD_EXTERNAL_COMPILER_RT. Specifically the
sub-ninja
>>>>     command is
>>>>     > always invoked, so changes to compiler-rt source files
will
>>>>     get built
>>>>     > properly, so this patch can be used for iterative
development
>>>>     with
>>>>     > just-built tools.
>>>>     >
>>>>     >http://reviews.llvm.org/D20992
>>>>     >
>>>>     > Files:
>>>>     >   CMakeLists.txt
>>>>     >  cmake/modules/LLVMExternalProjectUtils.cmake
>>>>     >   runtimes/CMakeLists.txt
>>>>     >
>>>>     > Index: runtimes/CMakeLists.txt
>>>>     >
>>>>    
==================================================================>>>>
> --- /dev/null
>>>>     > +++ runtimes/CMakeLists.txt
>>>>     > @@ -0,0 +1,16 @@
>>>>     > +include(LLVMExternalProjectUtils)
>>>>     > +
>>>>     > +# Discover the projects that use CMake in the
subdirectories.
>>>>     > +# Note that explicit cmake invocation is required
every time
>>>>     a new project is
>>>>     > +# added or removed.
>>>>     > +
>>>>     > +add_custom_target(runtimes)
>>>>     > +
>>>>     > +file(GLOB entries *)
>>>>     > +foreach(entry ${entries})
>>>>     > +  if(IS_DIRECTORY ${entry} AND EXISTS
${entry}/CMakeLists.txt)
>>>>     > +    get_filename_component(projName ${entry} NAME)
>>>>     > + llvm_ExternalProject_Add(${projName} ${entry}
USE_TOOLCHAIN)
>>>>     > +    add_dependencies(runtimes ${projName})
>>>>     > +  endif()
>>>>     > +endforeach(entry)
>>>>     > Index: cmake/modules/LLVMExternalProjectUtils.cmake
>>>>     >
>>>>    
==================================================================>>>>
> --- cmake/modules/LLVMExternalProjectUtils.cmake
>>>>     > +++ cmake/modules/LLVMExternalProjectUtils.cmake
>>>>     > @@ -29,7 +29,8 @@
>>>>     >  #     Extra targets in the subproject to generate
targets for
>>>>     >  #   )
>>>>     >  function(llvm_ExternalProject_Add name source_dir)
>>>>     > -  cmake_parse_arguments(ARG
>>>>     "USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL"
>>>>     > +  cmake_parse_arguments(ARG
>>>>     > +
"USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL;ALWAYS_CLEAN"
>>>>     >      "SOURCE_DIR"
>>>>     >
>>>>    
"CMAKE_ARGS;TOOLCHAIN_TOOLS;RUNTIME_LIBRARIES;DEPENDS;EXTRA_TARGETS"
>>>>     ${ARGN})
>>>>     >    canonicalize_tool_name(${name} nameCanon)
>>>>     > @@ -52,6 +53,10 @@
>>>>     >      endif()
>>>>     >    endforeach()
>>>>     >
>>>>     > +  if(ARG_ALWAYS_CLEAN)
>>>>     > +    set(always_clean clean)
>>>>     > +  endif()
>>>>     > +
>>>>     >    list(FIND TOOLCHAIN_TOOLS clang FOUND_CLANG)
>>>>     >    if(FOUND_CLANG GREATER -1)
>>>>     >      set(CLANG_IN_TOOLCHAIN On)
>>>>     > @@ -135,6 +140,14 @@
>>>>     >      CMAKE_ARGS ${${nameCanon}_CMAKE_ARGS}
>>>>     >                 ${compiler_args}
>>>>     >  -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
>>>>     > + 
-DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
>>>>     > + 
-DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_OUTPUT_INTDIR}
>>>>     > + 
-DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
>>>>     > +  -DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
>>>>     > +  -DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
>>>>     > +  -DPACKAGE_VERSION=${PACKAGE_VERSION}
>>>>     > +  -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
>>>>     > +  -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
>>>>
>>>>     How did you decide which variables need to be passed
through
>>>>     like this?
>>>>     The set seems somewhat arbitrary, but I may be missing
something
>>>>     obvious.
>>>>
>>>>     >                 ${ARG_CMAKE_ARGS}
>>>>     >  ${PASSTHROUGH_VARIABLES}
>>>>     >      INSTALL_COMMAND ""
>>>>     > @@ -152,7 +165,7 @@
>>>>     >      ExternalProject_Add_Step(${name} force-rebuild
>>>>     >        COMMAND ${run_build}
>>>>     >        COMMENT "Forcing rebuild of ${name}"
>>>>     > -      DEPENDEES configure clean
>>>>     > +      DEPENDEES configure ${always_clean}
>>>>
>>>>     I'm not sure I understand what this does. If I had to
guess I'd
>>>>     say that
>>>>     when ALWAYS_CLEAN is passed the rebuild of the external
project
>>>>     always
>>>>     invokes clean first, but if it's not passed we'll
just invoke the
>>>>     external build and allow it to be incremental if
appropriate.
>>>>     Is that
>>>>     right?
>>>>
>>>>     >        DEPENDS ${ALWAYS_REBUILD} ${ARG_DEPENDS}
${TOOLCHAIN_BINS}
>>>>     >        ${cmake_3_4_USES_TERMINAL} )
>>>>     >    endif()
>>>>     > Index: CMakeLists.txt
>>>>     >
>>>>    
==================================================================>>>>
> --- CMakeLists.txt
>>>>     > +++ CMakeLists.txt
>>>>     > @@ -720,6 +720,8 @@
>>>>     >    add_subdirectory(tools)
>>>>     >  endif()
>>>>     >
>>>>     > +add_subdirectory(runtimes)
>>>>     > +
>>>>     >  if( LLVM_INCLUDE_EXAMPLES )
>>>>     >    add_subdirectory(examples)
>>>>     >  endif()
>>>>     > @@ -730,7 +732,8 @@
>>>>     > llvm_ExternalProject_Add(test-suite
>>>>     ${LLVM_MAIN_SRC_DIR}/projects/test-suite
>>>>     >        USE_TOOLCHAIN
>>>>     >        EXCLUDE_FROM_ALL
>>>>     > -      NO_INSTALL)
>>>>     > +      NO_INSTALL
>>>>     > +      ALWAYS_CLEAN)
>>>>     >    endif()
>>>>     >    add_subdirectory(test)
>>>>     >    add_subdirectory(unittests)
>>>>     >
>>>>
>>>>     _______________________________________________
>>>>     llvm-commits mailing list
>>>>     llvm-commits at lists.llvm.org <mailto:llvm-commits at
lists.llvm.org>
>>>>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>> -- 
>> Employee of Qualcomm Innovation Center, Inc.
>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
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It seems to me that the feedback here has been generally positive, but a lot of
different ideas have been added to the mix.

To focus conversation and move things along I'm going to provide a summary
of changes with proposals for rollout.

Splitting Compiler-RT

If we want to split compiler-rt, which I think makes a lot of sense, I think the
best path forward is to copy the trunk (via svn cp). Copying the branch is the
best way to preserve the history and workflows.

For naming purposes I would suggest retaining the compiler-rt name for the
builtin libraries, and having a repository named sanitizer-rt for the sanitizer
libraries (this is of course just a suggestion, feel free to bike shed).

After duplicating the repository we could setup an auto-merge from compiler-rt
to sanitizer-rt. We could setup the LLVM build system so that if both projects
were present it would force only building builtins from compiler-rt and
sanitizers from sanitizer-rt. This would allow a transition time where bots
could be updated to include both repositories, and engineer workflows would not
be impacted.

After a brief time for bots to be updated with the new repository we could
modify the repositories separately to build only the parts they are supposed to
build, remove the hack from LLVM to force that, and begin removing code from the
separate repositories.

LLVM Restructuring

The first step here is adding the new functionality, iterating on the CMake
interface for the runtime projects and getting all the runtime projects hooked
up.

Once all the runtime project support is ready we can begin migrating bots and
evangelizing the new runtime build process.

At some point before or after the runtime work we can modify CMake to support
the test-suite living under tests (or somewhere else, bikeshed away).

Once runtime support is ready, and the test-suite is supported outside projects
we can set a date for removal of the projects directory. This planning should
take into account updating bots as well as updating scripts and tooling.

Breaking out testing tools

As I started looking into breaking out the testing tools I realized it is *much*
more complicated than I had first thought. I do think that it is a good idea to
do this, but it is going to be a bigger change than I had originally thought.

The big wrench in breaking out the testing tools is that you need more than just
lit. In particular you need FileCheck, not, count and a few other random things
under llvm/utils. This also means you need to break out libSupport and ADT.

While I think that breaking this stuff all out is a good idea, it is a much
larger change than what I was trying to propose. If we go down this route I
would recommend creating a new llvm-infrastructure repository. We could then
stub it out and update projects and workflows to include it. After the workflows
are updated we can start moving libraries and tools into it.

An alternative approach we could take would be to migrate the testing tools off
libSupport to make them standalone. Then the testing tools and lit could more
easily be lifted out of the LLVM repository. This approach has some benefits,
but also has added complication because some of the libSupport functionality in
use is non-trivial.

Thoughts?
-Chris

> On Jun 9, 2016, at 2:09 PM, Craig, Ben <ben.craig at codeaurora.org>
wrote:
> 
> 
>>> To get cmake to work, I have to set HAVE_CXX_ATOMICS_WITHOUT_LIB,
even though I have no intention of building LLVM.  I then get to set
LIBCXX_HAVE_CXX_ATOMICS_WITHOUT_LIB too, because reasons.
>> This is bad. I’m curious why you need to set those ever. Have you
diagnosed this? For you to need to set that it means the host toolchain isn’t
properly passing the CMake checks.
> It looks like I don't need to set these anymore, but the comment that I
left myself at the time was that HAVE_CXX_ATOMICS_WITHOUT_LIB looked at the
state of my local machine's toolchain, as opposed to the toolchain that I
was about to use.  My local machine's toolchain is gcc 4.6.3, and it
doesn't have an <atomic> header.
> 
>>> Multi-libs require multiple independent build directories, with all
the associated cmake overhead.
>> I strongly believe that for building multi-lib or more generally when
building for multiple targets you want multiple           build directories, and
in particular the multiple-cmake invocations. I believe this because you want
the checks to be relevant for the target, and the only way to do that is to run
the checks once per target.
>> 
>> That said, I also strongly believe that for any user of our projects we
should find a way to have a single simple CMake invocation that gets the end
result that you want. I don’t believe these are mutually exclusive goals.
>> 
>> One of the development steps of the new runtime directory will be
supporting specifying multiple targets to build the runtimes for, and having
CMake construct the appropriate number of build directories and manage building
them all through a single top-level configuration and build directory. If you’re
skeptical about how doable this is I’d encourage you to look at this bot ->
http://lab.llvm.org:8011/builders/clang-3stage-ubuntu
<http://lab.llvm.org:8011/builders/clang-3stage-ubuntu>.
>> 
>> That bot does a full 3-stage clang build from a single CMake
invocation:
>> 
>> cmake -C ../llvm.src/tools/clang/cmake/caches/3-stage.cmake -GNinja
-DLLVM_TARGETS_TO_BUILD=all -DLLVM_BINUTILS_INCDIR=/opt/binutils/include
../llvm.src
>> 
> I'm fine if I can invoke cmake once and get multiple library variants
out.  If that means that behind-the-scenes, cmake has multiple build
sub-directories, then that's fine by me.  On Windows, this already happens
to some degree, as the Visual Studio project is allowed to switch between
Release, Debug, RelWithDebInfo, etc without re-running cmake.
> 
>>> So why not run out of tree instead you may ask?
>>> 
>>> No lit tests or lit utilities (FileCheck, not, etc…)
>> I don’t know if the runtimes you’re building are setup for this or not,
but you can get out-of-tree tests working if you have an LLVM installation on
the system or a build directory that you can point at. Compiler-RT does this. It
isn’t ideal but it is workable.
>> 
>> We should have a better solution.
> The nightly builds that my organization produces is generally a
"customer build", and not a "developer build".  Stated
otherwise, it doesn't include llvm-config, libclang.a, or any of the other
things that people building against llvm would want.  That means that if I
wanted to use this particular out-of-tree solution, I would still need to clone
down LLVM and rebuild and reinstall it on occasion.
> 
>>> So some things I would like to see...
>>> 
>>> Standalone runtime builds should use the "normal" build
interfaces (bare make, make all, make check, make install.  s/make/ninja as
desired).
>> I think this is doable, but I’m hesitant to rope it in with what I’m
trying to do here. Nothing I want to do would prevent this or make it any harder
than it already is.
> Completely fair.  I figured I'd get my grievances and wishlist out
first, just so that some agreement on a direction can be figured out.  It does
extend beyond the directory re-org patch.
> 
>>> Break out testing infrastructure to a common repo, so that the
runtimes can have access to the testing "banana" without dragging
along the LLVM "gorilla”.
>> I’m hesitant to suggest more and more repos because I think there are
some challenges and additional burdens with that. I do understand the benefit of
what you’re asking for here, and I think it is worth considering. I think there
is an argument for splitting out the LLVM testing infrastructure, as well as an
argument for splitting out the LLVM build infrastructure.
>> 
>> In both cases I think those changes are larger than what I’m proposing,
but worth considering.
>> 
>> -Chris
>> 
>> Obligatory troll: Maybe we should move to github and change the whole
repo structure in the process?
> I figured the github thread was crazy enough without me sabotaging it with
this kind of suggestion :)
> 
>>> 
>>> 
>>> On 6/9/2016 12:20 PM, Chris Bieneman via llvm-dev wrote:
>>>> Moving to llvm-dev (I think this has gone a bit further than a
patch review discussion)
>>>> 
>>>> In hindsight I probably should have explained more of my
thinking on this with the patch, or done an RFC on llvm-dev to start with. I’l
do that now, and answer the questions along the way. I sent a separate email
discussing Justin’s patch review feedback.
>>>> 
>>>> In the build system today there is no strong distinction
between ‘projects’ and ‘tools’. There are a few subtle differences, but I’m not
sure any of them really matter. The differences are:
>>>> 
>>>> (1) The projects directory is always configured, tools can be
disabled using LLVM_INCLUDE_TOOLS=Off (projects and tools can both be
individually disabled too)
>>>> (2) Projects are configured before tools, so tools can rely on
targets being created for projects (we don’t really use this, and anywhere we
are is probably a bug)
>>>> (3) Some projects have special handling. For example test-suite
isn’t actually treated as a project, it has special handling in
LLVM/CMakeLists.txt:727, and Compiler-RT is handled by clang if you set
LLVM_BUILD_EXTERNAL_COMPILER_RT=On.
>>>> 
>>>> With this in mind I was thinking about the general usability of
our build system. The distinction between a project and a tool is not very
clear. At a high level I see three different use cases that are covered by our
current projects & tools directories.
>>>> 
>>>> (1) Projects that are configured with LLVM
>>>> (2) Runtime projects that should be configured using the
just-built tools
>>>> (3) The LLVM test-suite, which is really just external tests
that should be configured and run with the just-built tools
>>>> 
>>>> My proposal is that we make the tools subdirectory the *only*
place for projects that fall into category 1. I don’t think there is any
technical reason to drop an in-tree project into projects over tools today, and
I think we migrating people who are doing that away from it should be easy.
>>>> 
>>>> Second I want to add a “runtimes” directory to LLVM to cover
case 2 (see D20992). The idea behind this is to use common code in LLVM to
support building runtimes. This will allow the full LLVM toolchain to be visible
during configuration. I will abstract this functionality into an installed CMake
module so that Clang can use it for out-of-tree clang builds.
>>>> 
>>>> Lastly we need to give the test-suite a new home. I’m not super
concerned with where we do that. It could be under tests, it could just be at
the root of the LLVM directory. I don’t think it matters too much because it is
a one-off. Thoughts welcome.
>>>> 
>>>> My proposed patch makes the runtimes directory work for
Compiler-RT, but it doesn’t yet handle libcxxabi, libcxx and libunwind. There is
some special case handling between libcxxabi and libcxx that will need to be
handled to make the dependencies work between the two, and I still need to work
that out.
>>>> 
>>>> If we want to go with this proposal I envision the transition
being multi-staged:
>>>> 
>>>> (1) Adding the new functionality, getting it up and fully
working for all runtime projects - this will involve changes to runtime projects
>>>> (2) Work with bot maintainers to migrate bots, and fix any
issues that come up
>>>> (3) Add support for a new secondary location for the test-suite
>>>> (4) Set a date for removing the projects directory, post
patches including updated documentation
>>>> (5) Remove the projects directory entirely
>>>> 
>>>> Thoughts?
>>>> -Chris
>>>> 
>>>>> On Jun 8, 2016, at 6:59 PM, Chandler Carruth <chandlerc
at gmail.com <mailto:chandlerc at gmail.com>> wrote:
>>>>> 
>>>>> On Wed, Jun 8, 2016 at 4:39 PM Justin Bogner via
llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at
lists.llvm.org>> wrote:
>>>>> Chris Bieneman <beanz at apple.com <mailto:beanz at
apple.com>> writes:
>>>>> > beanz created this revision.
>>>>> > beanz added reviewers: chandlerc, bogner.
>>>>> > beanz added a subscriber: llvm-commits.
>>>>> >
>>>>> > There are a few LLVM projects that produce runtime
libraries. Ideally
>>>>> > runtime libraries should be built differently than
other projects,
>>>>> > specifically they should be built using the just-built
toolchain.
>>>>> >
>>>>> > There is support for building compiler-rt in this way
from the clang
>>>>> > build. Moving this logic into the LLVM build is
interesting because it
>>>>> > provides a simpler way to extend the just-built
toolchain to include
>>>>> > LLD and the LLVM object file tools.
>>>>> >
>>>>> > Once this functionality is better fleshed out and
tested we’ll want to
>>>>> > encapsulate it in a module that can be used for clang
standalone
>>>>> > builds, and we’ll want to make it the default way to
build compiler-rt.
>>>>> >
>>>>> > With this patch applied there is no immediate change
in the build.
>>>>> > Moving compiler-rt out from llvm/projects into
llvm/runtimes enables
>>>>> > the functionality.
>>>>> 
>>>>> This seems reasonable, but I am a little worried about how
transitioning
>>>>> to the new system will work. Will everyone have to move
their
>>>>> compiler-rt checkout? Will we continue to support
compiler-rt in either
>>>>> place? Both of these are workable, but neither is great.
Thoughts?
>>>>> 
>>>>> I share your concerns, but I also kind of like the
direction this is going.
>>>>> 
>>>>> But there is a higher-level meta-point: do we want to keep
the 'projects' directory *at all*.
>>>>> 
>>>>> Every single resident of it I can think of except for the
test-suite is either dead (dragonegg) or a runtime library.
>>>>> 
>>>>> I think we should either have all the build-integrated
projects in a single 'projects' directory (including LLD and Clang), or
we should have none of them and use more domain relevant organization (today
"tools", you're adding "runtimes", maybe we move the
test-suite to go under one of the test directories).
>>>>> 
>>>>> I think we should have a consistent plan here before moving
stuff. But once we have it, I think we shouldn't be afraid of re-organizing
stuff to make more sense, and just work to get folks to update their checkouts.
>>>>> 
>>>>> -Chandler
>>>>>  
>>>>> 
>>>>> > This code has a few improvements over the method
provided by
>>>>> > LLVM_BUILD_EXTERNAL_COMPILER_RT. Specifically the
sub-ninja command is
>>>>> > always invoked, so changes to compiler-rt source files
will get built
>>>>> > properly, so this patch can be used for iterative
development with
>>>>> > just-built tools.
>>>>> >
>>>>> > 
<http://reviews.llvm.org/D20992>http://reviews.llvm.org/D20992
<http://reviews.llvm.org/D20992>
>>>>> >
>>>>> > Files:
>>>>> >   CMakeLists.txt
>>>>> >   cmake/modules/LLVMExternalProjectUtils.cmake
>>>>> >   runtimes/CMakeLists.txt
>>>>> >
>>>>> > Index: runtimes/CMakeLists.txt
>>>>> >
==================================================================>>>>>
> --- /dev/null
>>>>> > +++ runtimes/CMakeLists.txt
>>>>> > @@ -0,0 +1,16 @@
>>>>> > +include(LLVMExternalProjectUtils)
>>>>> > +
>>>>> > +# Discover the projects that use CMake in the
subdirectories.
>>>>> > +# Note that explicit cmake invocation is required
every time a new project is
>>>>> > +# added or removed.
>>>>> > +
>>>>> > +add_custom_target(runtimes)
>>>>> > +
>>>>> > +file(GLOB entries *)
>>>>> > +foreach(entry ${entries})
>>>>> > +  if(IS_DIRECTORY ${entry} AND EXISTS
${entry}/CMakeLists.txt)
>>>>> > +    get_filename_component(projName ${entry} NAME)
>>>>> > +    llvm_ExternalProject_Add(${projName} ${entry}
USE_TOOLCHAIN)
>>>>> > +    add_dependencies(runtimes ${projName})
>>>>> > +  endif()
>>>>> > +endforeach(entry)
>>>>> > Index: cmake/modules/LLVMExternalProjectUtils.cmake
>>>>> >
==================================================================>>>>>
> --- cmake/modules/LLVMExternalProjectUtils.cmake
>>>>> > +++ cmake/modules/LLVMExternalProjectUtils.cmake
>>>>> > @@ -29,7 +29,8 @@
>>>>> >  #     Extra targets in the subproject to generate
targets for
>>>>> >  #   )
>>>>> >  function(llvm_ExternalProject_Add name source_dir)
>>>>> > -  cmake_parse_arguments(ARG
"USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL"
>>>>> > +  cmake_parse_arguments(ARG
>>>>> > +   
"USE_TOOLCHAIN;EXCLUDE_FROM_ALL;NO_INSTALL;ALWAYS_CLEAN"
>>>>> >      "SOURCE_DIR"
>>>>> >     
"CMAKE_ARGS;TOOLCHAIN_TOOLS;RUNTIME_LIBRARIES;DEPENDS;EXTRA_TARGETS"
${ARGN})
>>>>> >    canonicalize_tool_name(${name} nameCanon)
>>>>> > @@ -52,6 +53,10 @@
>>>>> >      endif()
>>>>> >    endforeach()
>>>>> >
>>>>> > +  if(ARG_ALWAYS_CLEAN)
>>>>> > +    set(always_clean clean)
>>>>> > +  endif()
>>>>> > +
>>>>> >    list(FIND TOOLCHAIN_TOOLS clang FOUND_CLANG)
>>>>> >    if(FOUND_CLANG GREATER -1)
>>>>> >      set(CLANG_IN_TOOLCHAIN On)
>>>>> > @@ -135,6 +140,14 @@
>>>>> >      CMAKE_ARGS ${${nameCanon}_CMAKE_ARGS}
>>>>> >                 ${compiler_args}
>>>>> >                
-DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
>>>>> > +              
-DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
>>>>> > +              
-DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_OUTPUT_INTDIR}
>>>>> > +              
-DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
>>>>> > +              
-DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
>>>>> > +              
-DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
>>>>> > +               -DPACKAGE_VERSION=${PACKAGE_VERSION}
>>>>> > +               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
>>>>> > +              
-DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
>>>>> 
>>>>> How did you decide which variables need to be passed
through like this?
>>>>> The set seems somewhat arbitrary, but I may be missing
something
>>>>> obvious.
>>>>> 
>>>>> >                 ${ARG_CMAKE_ARGS}
>>>>> >                 ${PASSTHROUGH_VARIABLES}
>>>>> >      INSTALL_COMMAND ""
>>>>> > @@ -152,7 +165,7 @@
>>>>> >      ExternalProject_Add_Step(${name} force-rebuild
>>>>> >        COMMAND ${run_build}
>>>>> >        COMMENT "Forcing rebuild of ${name}"
>>>>> > -      DEPENDEES configure clean
>>>>> > +      DEPENDEES configure ${always_clean}
>>>>> 
>>>>> I'm not sure I understand what this does. If I had to
guess I'd say that
>>>>> when ALWAYS_CLEAN is passed the rebuild of the external
project always
>>>>> invokes clean first, but if it's not passed we'll
just invoke the
>>>>> external build and allow it to be incremental if
appropriate. Is that
>>>>> right?
>>>>> 
>>>>> >        DEPENDS ${ALWAYS_REBUILD} ${ARG_DEPENDS}
${TOOLCHAIN_BINS}
>>>>> >        ${cmake_3_4_USES_TERMINAL} )
>>>>> >    endif()
>>>>> > Index: CMakeLists.txt
>>>>> >
==================================================================>>>>>
> --- CMakeLists.txt
>>>>> > +++ CMakeLists.txt
>>>>> > @@ -720,6 +720,8 @@
>>>>> >    add_subdirectory(tools)
>>>>> >  endif()
>>>>> >
>>>>> > +add_subdirectory(runtimes)
>>>>> > +
>>>>> >  if( LLVM_INCLUDE_EXAMPLES )
>>>>> >    add_subdirectory(examples)
>>>>> >  endif()
>>>>> > @@ -730,7 +732,8 @@
>>>>> >      llvm_ExternalProject_Add(test-suite
${LLVM_MAIN_SRC_DIR}/projects/test-suite
>>>>> >        USE_TOOLCHAIN
>>>>> >        EXCLUDE_FROM_ALL
>>>>> > -      NO_INSTALL)
>>>>> > +      NO_INSTALL
>>>>> > +      ALWAYS_CLEAN)
>>>>> >    endif()
>>>>> >    add_subdirectory(test)
>>>>> >    add_subdirectory(unittests)
>>>>> >
>>>>> 
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at lists.llvm.org <mailto:llvm-commits at
lists.llvm.org>
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits>
>>>> 
>>>> 
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>>> 
>>> -- 
>>> Employee of Qualcomm Innovation Center, Inc.
>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>> 
> 
> -- 
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux
Foundation Collaborative Project
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