llvm dev - Oct 2019 - RFC: LLVM Build System Future Direction

Over the past few years the LLVM CMake build system has gained a lot of new
features, which have powered new workflows and capabilities. This development
has largely been individual efforts without focus or long-term direction. The
build system is of incredible importance to LLVM as it is a primary interface
for contributors to build and test their changes.

This year, LLVM is making a huge infrastructure shift to GitHub. Along with that
shift many of the previously supported build options may not make sense. This is
a prefect opportunity to revisit the state of our build infrastructure with an
eye toward the future.

I would like this RFC, and any discussion it sparks, to serve as a starting
point for a conversation we can continue at the LLVM Developer Meeting to set
goals and conventions for the development of the build system.

Tom Stellard has scheduled a roundtable on CMake from 10:45-11:55 on Wednesday,
Oct 23.

## The Problem
Lacking clear direction and oversight the build system is evolving in rapidly
divergent ways. Further since we don't have a formalized process for
unifying workflows and deprecating old behaviors LLVM's build system has a
convoluted feature set.

This manifests itself in many unfortunate ways. Some examples are:

(1) There are three different ways to build compiler-rt as part of LLVM
(2) There are lots of incompatible build configurations that need to be
accounted for, some that aren't (like -DLLVM_BUILD_LLVM_DYLIB=On
-DBUILD_SHARED_LIBS=On, which will explode at runtime)

As the build system gains complexity maintaining the build system is getting
more expensive to the community.

## Future Directions
The following are proposals to enable the build system to better facilitate LLVM
development and provide a usable, extensible, and stable build system for LLVM
and all sub-projects.

### Updating CMake More Regularly
In the past we have clung to old versions of CMake for extended periods of time.
This has resulted in significant checking `CMAKE_VERSION` to enable some
features or being completely unable to use others. In particular recent CMake
development extending generator expressions could provide substantial benefit to
the project. If we stick to current upgrade policies, we may not be able to use
the current CMake release for another few years.

As an alternative proposal, we should consider CMake upgrades independent of OS
package manager versioning. That is not to say we should take every new version
of CMake, however we should upgrade for compelling reasons.

In tree right now we have code gated on CMake 3.7 which enables CMake to
generate Ninja rules for tablegen that process tablegen's dep files. This
allows accurately rebuilding tablegen when included files change. I propose that
this change's benefit should be sufficient to justify moving to CMake 3.7
for the project.

Additionally, building LLDB.framework on Darwin requires CMake 3.8 due to bugs
in earlier versions of CMake. This could also be a justification for updating.
Lastly, getting updated versions of CMake is very easy. Kitware provides
Windows, Mac and Linux builds on cmake.org as well as an Ubuntu apt source. If
that is insufficient building CMake from source is simple, and has minimal
system requirements. Visual Studio contains reasonably up-to-date CMake bundled.
As such we should not allow OS release or support cycles to dictate when we
upgrade CMake.

### Reducing the Test Matrix
The most important guiding principal for development of the LLVM build system
must be to reduce the matrix of configurations. The more possible configurations
the build system supports the wider the test matrix. This is not to say the
build system should support doing less, but rather to support less unique
configurations.

Many configuration options in the build system just turn on or off different
parts of the project. For example, the `LLVM_BUILD_LLVM_DYLIB` option just
disables configuring libLLVM. An alternative approach would be to always
configure libLLVM, and leave it up to users of the build system to determine
whether or not to build it.

We also have options to enable and disable configuring individual tools in the
LLVM and Clang projects. I believe we should eliminate those options, which will
result in the `all` target always being everything. We have explicit clean
dependencies for the `check-*` targets so most developer workflows should be
un-impacted. Distribution workflows can use the `LLVM_DISTRIBUTION_COMPONENTS`
option to hand tailor which parts of LLVM to build and install with better
control without as much complication.

Many other options exist to support a wide variety of divergent workflows. For
example, the `LLVM_EXTERNAL_${PROJECT}_SOURCE_DIR` options exist to allow users
to specify custom paths for projects so that, historically, they didn't need
to nest clang inside LLVM. With the move to the mono-repo we should define
consistent workflows and eliminate options that support divergent workflows.

### Adopting Conventions
Much of LLVM's build system is not idiomatic CMake. Some of those
differences make sense because LLVM is not a typical software project. I'm
unaware of any build configuration system that was designed specifically to
build compilers and handle the complex dependency chains that come with that
territory.

Some of our divergences come from history. We have a great many features
implemented in our CMake because CMake didn't support them at the time. We
also have patterns that were appropriate before CMake added new features, and
have never cleaned them up.

One big thing our build system needs is a set of guiding conventions to direct
future development. Some key conventions that I believe are crucial:

#### Avoid Order Dependent Behavior
CMake generator expressions provide the ability to defer logic until after
script processing. This allows the build system to avoid direct dependence on
the order in which targets are processed. We should not use the `if(TARGET ...)`
or `get_target_property` interfaces unless it is completely impossible to avoid.

#### Avoid Options to Enable/Disable Configuration
If we reduce the test matrix, having a convention to keep it reduced is of vital
importance so that we don't find ourselves needing to clean up again in a
few years.

#### Avoid Caching, Use `mark_as_advanced` and `INTERNAL` Liberally
CMake has no strategy for cache invalidation. As such, cached variables add
additional maintenance burden because they can break builds sometimes in hard to
diagnose ways. That said they are useful. In particular for things like
configuration checks that are slow caching the result makes incremental
re-configuration much faster. We should use cached values sparingly and only
where they provide benefit.

Additionally, every cached CMake variable is a configuration point. Variables
not marked `INTERNAL` show up in `ccmake` and `cmake-gui`, and variables not
`mark_as_advanced` show up to all users. We should use the `INTERNAL` and
`mark_as_advanced` options wherever appropriate to limit our supported
configuration interface.

#### Making Sense of Runtime Builds
Right now, there are three different ways to build compiler-rt as part of LLVM
and two different ways to build most of the other runtime libraries (libcxxabi,
libcxx, libunwind, etc). This situation is confusing even for long time
contributors.

We need a clearer story for building runtime libraries to reduce the number of
different ways they are built and provide simplified workflows for users.

It is my opinion that if you are building a runtime library as part of an
LLVM/Clang build, it should be configured and built with the in-tree clang as it
would be for distribution. If you don't want to build with the in-tree
clang, we should encourage people to build the runtime libraries independently
of the compiler.

My reasoning for this is that distributions of clang are generally built from
the default settings in the build and configuration process, and distributions
(or installs by new users) which include the runtime libraries should have
runtimes built with the just-built compiler. To align these two situations we
need the default build configuration of LLVM+Clang+Runtimes to be using the
just-built compiler.

Adopting this change would mean runtime library projects would only contain
build system support for building "standalone" meaning not in the same
configuration as LLVM. We would then support runtime libraries built as
individual projects or using the LLVM runtimes directory, which separately
configures and builds runtime libraries using the just-built clang.

On Mon, 21 Oct 2019 at 11:26, Chris Bieneman via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Over the past few years the LLVM CMake build system has gained a lot of new
features, which have powered new workflows and capabilities. This development
has largely been individual efforts without focus or long-term direction. The
build system is of incredible importance to LLVM as it is a primary interface
for contributors to build and test their changes.
>
> This year, LLVM is making a huge infrastructure shift to GitHub. Along with
that shift many of the previously supported build options may not make sense.
This is a prefect opportunity to revisit the state of our build infrastructure
with an eye toward the future.
>
> I would like this RFC, and any discussion it sparks, to serve as a starting
point for a conversation we can continue at the LLVM Developer Meeting to set
goals and conventions for the development of the build system.
>
> Tom Stellard has scheduled a roundtable on CMake from 10:45-11:55 on
Wednesday, Oct 23.
Thanks for sharing this RFC Chris. I'd also like to highlight that the
LLVM test-suite still has parallel Make and CMake build systems - it
might be useful to consider if it's practical to retire the
Makefile-based build system?

Best,

Alex

Hi Chris,

This is a great initiative and it feels like the right direction.

I'd like to add another point to the list: using LLVM as a library, i.e.
being able to add it as a CMake subproject.
Currently it works pretty good, but some parts can be improved (somehow).
E.g.:
 - getting LLVM's version: the only way I've found is to parse the
CMakeLists.txt with regexes and hope it doesn't break in the future
 - getting include dirs info: IIRC currently it works transitively when one
links against some library, but it feels like a weak point to me
 - getting other configuration options (for example whether LLVM is built
with or without exceptions)
 - controlling how LLVM is built: the only way I found is to force set a
variable (i.e. set (LLVM_BUILD_32_BITS ON CACHE BOOL "" FORCE)) before
adding LLVM as a subproject

I think my list is not exhaustive since it covers only my use cases, so
maybe there are other opinions/requests from others.

Cheers,
Alex.

On Mon, Oct 21, 2019 at 8:26 PM Chris Bieneman via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Over the past few years the LLVM CMake build system has gained a lot of
> new features, which have powered new workflows and capabilities. This
> development has largely been individual efforts without focus or long-term
> direction. The build system is of incredible importance to LLVM as it is a
> primary interface for contributors to build and test their changes.
>
> This year, LLVM is making a huge infrastructure shift to GitHub. Along
> with that shift many of the previously supported build options may not make
> sense. This is a prefect opportunity to revisit the state of our build
> infrastructure with an eye toward the future.
>
> I would like this RFC, and any discussion it sparks, to serve as a
> starting point for a conversation we can continue at the LLVM Developer
> Meeting to set goals and conventions for the development of the build
> system.
>
> Tom Stellard has scheduled a roundtable on CMake from 10:45-11:55 on
> Wednesday, Oct 23.
>
> ## The Problem
> Lacking clear direction and oversight the build system is evolving in
> rapidly divergent ways. Further since we don't have a formalized
process
> for unifying workflows and deprecating old behaviors LLVM's build
system
> has a convoluted feature set.
>
> This manifests itself in many unfortunate ways. Some examples are:
>
> (1) There are three different ways to build compiler-rt as part of LLVM
> (2) There are lots of incompatible build configurations that need to be
> accounted for, some that aren't (like -DLLVM_BUILD_LLVM_DYLIB=On
> -DBUILD_SHARED_LIBS=On, which will explode at runtime)
>
> As the build system gains complexity maintaining the build system is
> getting more expensive to the community.
>
> ## Future Directions
> The following are proposals to enable the build system to better
> facilitate LLVM development and provide a usable, extensible, and stable
> build system for LLVM and all sub-projects.
>
> ### Updating CMake More Regularly
> In the past we have clung to old versions of CMake for extended periods of
> time. This has resulted in significant checking `CMAKE_VERSION` to enable
> some features or being completely unable to use others. In particular
> recent CMake development extending generator expressions could provide
> substantial benefit to the project. If we stick to current upgrade
> policies, we may not be able to use the current CMake release for another
> few years.
>
> As an alternative proposal, we should consider CMake upgrades independent
> of OS package manager versioning. That is not to say we should take every
> new version of CMake, however we should upgrade for compelling reasons.
>
> In tree right now we have code gated on CMake 3.7 which enables CMake to
> generate Ninja rules for tablegen that process tablegen's dep files.
This
> allows accurately rebuilding tablegen when included files change. I propose
> that this change's benefit should be sufficient to justify moving to
CMake
> 3.7 for the project.
>
> Additionally, building LLDB.framework on Darwin requires CMake 3.8 due to
> bugs in earlier versions of CMake. This could also be a justification for
> updating.
> Lastly, getting updated versions of CMake is very easy. Kitware provides
> Windows, Mac and Linux builds on cmake.org as well as an Ubuntu apt
> source. If that is insufficient building CMake from source is simple, and
> has minimal system requirements. Visual Studio contains reasonably
> up-to-date CMake bundled. As such we should not allow OS release or support
> cycles to dictate when we upgrade CMake.
>
> ### Reducing the Test Matrix
> The most important guiding principal for development of the LLVM build
> system must be to reduce the matrix of configurations. The more possible
> configurations the build system supports the wider the test matrix. This is
> not to say the build system should support doing less, but rather to
> support less unique configurations.
>
> Many configuration options in the build system just turn on or off
> different parts of the project. For example, the `LLVM_BUILD_LLVM_DYLIB`
> option just disables configuring libLLVM. An alternative approach would be
> to always configure libLLVM, and leave it up to users of the build system
> to determine whether or not to build it.
>
> We also have options to enable and disable configuring individual tools in
> the LLVM and Clang projects. I believe we should eliminate those options,
> which will result in the `all` target always being everything. We have
> explicit clean dependencies for the `check-*` targets so most developer
> workflows should be un-impacted. Distribution workflows can use the
> `LLVM_DISTRIBUTION_COMPONENTS` option to hand tailor which parts of LLVM to
> build and install with better control without as much complication.
>
> Many other options exist to support a wide variety of divergent workflows.
> For example, the `LLVM_EXTERNAL_${PROJECT}_SOURCE_DIR` options exist to
> allow users to specify custom paths for projects so that, historically,
> they didn't need to nest clang inside LLVM. With the move to the
mono-repo
> we should define consistent workflows and eliminate options that support
> divergent workflows.
>
> ### Adopting Conventions
> Much of LLVM's build system is not idiomatic CMake. Some of those
> differences make sense because LLVM is not a typical software project.
I'm
> unaware of any build configuration system that was designed specifically to
> build compilers and handle the complex dependency chains that come with
> that territory.
>
> Some of our divergences come from history. We have a great many features
> implemented in our CMake because CMake didn't support them at the time.
We
> also have patterns that were appropriate before CMake added new features,
> and have never cleaned them up.
>
> One big thing our build system needs is a set of guiding conventions to
> direct future development. Some key conventions that I believe are crucial:
>
> #### Avoid Order Dependent Behavior
> CMake generator expressions provide the ability to defer logic until after
> script processing. This allows the build system to avoid direct dependence
> on the order in which targets are processed. We should not use the
> `if(TARGET ...)` or `get_target_property` interfaces unless it is
> completely impossible to avoid.
>
> #### Avoid Options to Enable/Disable Configuration
> If we reduce the test matrix, having a convention to keep it reduced is of
> vital importance so that we don't find ourselves needing to clean up
again
> in a few years.
>
> #### Avoid Caching, Use `mark_as_advanced` and `INTERNAL` Liberally
> CMake has no strategy for cache invalidation. As such, cached variables
> add additional maintenance burden because they can break builds sometimes
> in hard to diagnose ways. That said they are useful. In particular for
> things like configuration checks that are slow caching the result makes
> incremental re-configuration much faster. We should use cached values
> sparingly and only where they provide benefit.
>
> Additionally, every cached CMake variable is a configuration point.
> Variables not marked `INTERNAL` show up in `ccmake` and `cmake-gui`, and
> variables not `mark_as_advanced` show up to all users. We should use the
> `INTERNAL` and `mark_as_advanced` options wherever appropriate to limit our
> supported configuration interface.
>
> #### Making Sense of Runtime Builds
> Right now, there are three different ways to build compiler-rt as part of
> LLVM and two different ways to build most of the other runtime libraries
> (libcxxabi, libcxx, libunwind, etc). This situation is confusing even for
> long time contributors.
>
> We need a clearer story for building runtime libraries to reduce the
> number of different ways they are built and provide simplified workflows
> for users.
>
> It is my opinion that if you are building a runtime library as part of an
> LLVM/Clang build, it should be configured and built with the in-tree clang
> as it would be for distribution. If you don't want to build with the
> in-tree clang, we should encourage people to build the runtime libraries
> independently of the compiler.
>
> My reasoning for this is that distributions of clang are generally built
> from the default settings in the build and configuration process, and
> distributions (or installs by new users) which include the runtime
> libraries should have runtimes built with the just-built compiler. To align
> these two situations we need the default build configuration of
> LLVM+Clang+Runtimes to be using the just-built compiler.
>
> Adopting this change would mean runtime library projects would only
> contain build system support for building "standalone" meaning
not in the
> same configuration as LLVM. We would then support runtime libraries built
> as individual projects or using the LLVM runtimes directory, which
> separately configures and builds runtime libraries using the just-built
> clang.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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> On Oct 24, 2019, at 02:17, Alex Denisov via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi Chris,
> 
> This is a great initiative and it feels like the right direction.
> 
> I'd like to add another point to the list: using LLVM as a library,
i.e. being able to add it as a CMake subproject.
> Currently it works pretty good, but some parts can be improved (somehow).
E.g.:
I believe the CMake-correct way of doing that is to produce LLVM export files
when installing LLVM, which would allow find_package to work out of the box.
You’d get LLVM targets you can link against and all dependencies would be
propagated by CMake properly.

Louis
>  - getting LLVM's version: the only way I've found is to parse the
CMakeLists.txt with regexes and hope it doesn't break in the future
>  - getting include dirs info: IIRC currently it works transitively when one
links against some library, but it feels like a weak point to me
>  - getting other configuration options (for example whether LLVM is built
with or without exceptions)
>  - controlling how LLVM is built: the only way I found is to force set a
variable (i.e. set (LLVM_BUILD_32_BITS ON CACHE BOOL "" FORCE)) before
adding LLVM as a subproject
> 
> I think my list is not exhaustive since it covers only my use cases, so
maybe there are other opinions/requests from others.
> 
> Cheers,
> Alex.
> 
> On Mon, Oct 21, 2019 at 8:26 PM Chris Bieneman via llvm-dev <llvm-dev at
lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> Over the past few years the LLVM CMake build system has gained a lot of new
features, which have powered new workflows and capabilities. This development
has largely been individual efforts without focus or long-term direction. The
build system is of incredible importance to LLVM as it is a primary interface
for contributors to build and test their changes.
> 
> This year, LLVM is making a huge infrastructure shift to GitHub. Along with
that shift many of the previously supported build options may not make sense.
This is a prefect opportunity to revisit the state of our build infrastructure
with an eye toward the future.
> 
> I would like this RFC, and any discussion it sparks, to serve as a starting
point for a conversation we can continue at the LLVM Developer Meeting to set
goals and conventions for the development of the build system.
> 
> Tom Stellard has scheduled a roundtable on CMake from 10:45-11:55 on
Wednesday, Oct 23.
> 
> ## The Problem
> Lacking clear direction and oversight the build system is evolving in
rapidly divergent ways. Further since we don't have a formalized process for
unifying workflows and deprecating old behaviors LLVM's build system has a
convoluted feature set.
> 
> This manifests itself in many unfortunate ways. Some examples are:
> 
> (1) There are three different ways to build compiler-rt as part of LLVM
> (2) There are lots of incompatible build configurations that need to be
accounted for, some that aren't (like -DLLVM_BUILD_LLVM_DYLIB=On
-DBUILD_SHARED_LIBS=On, which will explode at runtime)
> 
> As the build system gains complexity maintaining the build system is
getting more expensive to the community.
> 
> ## Future Directions
> The following are proposals to enable the build system to better facilitate
LLVM development and provide a usable, extensible, and stable build system for
LLVM and all sub-projects.
> 
> ### Updating CMake More Regularly
> In the past we have clung to old versions of CMake for extended periods of
time. This has resulted in significant checking `CMAKE_VERSION` to enable some
features or being completely unable to use others. In particular recent CMake
development extending generator expressions could provide substantial benefit to
the project. If we stick to current upgrade policies, we may not be able to use
the current CMake release for another few years.
> 
> As an alternative proposal, we should consider CMake upgrades independent
of OS package manager versioning. That is not to say we should take every new
version of CMake, however we should upgrade for compelling reasons.
> 
> In tree right now we have code gated on CMake 3.7 which enables CMake to
generate Ninja rules for tablegen that process tablegen's dep files. This
allows accurately rebuilding tablegen when included files change. I propose that
this change's benefit should be sufficient to justify moving to CMake 3.7
for the project.
> 
> Additionally, building LLDB.framework on Darwin requires CMake 3.8 due to
bugs in earlier versions of CMake. This could also be a justification for
updating.
> Lastly, getting updated versions of CMake is very easy. Kitware provides
Windows, Mac and Linux builds on cmake.org <http://cmake.org/> as well as
an Ubuntu apt source. If that is insufficient building CMake from source is
simple, and has minimal system requirements. Visual Studio contains reasonably
up-to-date CMake bundled. As such we should not allow OS release or support
cycles to dictate when we upgrade CMake.
> 
> ### Reducing the Test Matrix
> The most important guiding principal for development of the LLVM build
system must be to reduce the matrix of configurations. The more possible
configurations the build system supports the wider the test matrix. This is not
to say the build system should support doing less, but rather to support less
unique configurations.
> 
> Many configuration options in the build system just turn on or off
different parts of the project. For example, the `LLVM_BUILD_LLVM_DYLIB` option
just disables configuring libLLVM. An alternative approach would be to always
configure libLLVM, and leave it up to users of the build system to determine
whether or not to build it.
> 
> We also have options to enable and disable configuring individual tools in
the LLVM and Clang projects. I believe we should eliminate those options, which
will result in the `all` target always being everything. We have explicit clean
dependencies for the `check-*` targets so most developer workflows should be
un-impacted. Distribution workflows can use the `LLVM_DISTRIBUTION_COMPONENTS`
option to hand tailor which parts of LLVM to build and install with better
control without as much complication.
> 
> Many other options exist to support a wide variety of divergent workflows.
For example, the `LLVM_EXTERNAL_${PROJECT}_SOURCE_DIR` options exist to allow
users to specify custom paths for projects so that, historically, they
didn't need to nest clang inside LLVM. With the move to the mono-repo we
should define consistent workflows and eliminate options that support divergent
workflows.
> 
> ### Adopting Conventions
> Much of LLVM's build system is not idiomatic CMake. Some of those
differences make sense because LLVM is not a typical software project. I'm
unaware of any build configuration system that was designed specifically to
build compilers and handle the complex dependency chains that come with that
territory.
> 
> Some of our divergences come from history. We have a great many features
implemented in our CMake because CMake didn't support them at the time. We
also have patterns that were appropriate before CMake added new features, and
have never cleaned them up.
> 
> One big thing our build system needs is a set of guiding conventions to
direct future development. Some key conventions that I believe are crucial:
> 
> #### Avoid Order Dependent Behavior
> CMake generator expressions provide the ability to defer logic until after
script processing. This allows the build system to avoid direct dependence on
the order in which targets are processed. We should not use the `if(TARGET ...)`
or `get_target_property` interfaces unless it is completely impossible to avoid.
> 
> #### Avoid Options to Enable/Disable Configuration
> If we reduce the test matrix, having a convention to keep it reduced is of
vital importance so that we don't find ourselves needing to clean up again
in a few years.
> 
> #### Avoid Caching, Use `mark_as_advanced` and `INTERNAL` Liberally
> CMake has no strategy for cache invalidation. As such, cached variables add
additional maintenance burden because they can break builds sometimes in hard to
diagnose ways. That said they are useful. In particular for things like
configuration checks that are slow caching the result makes incremental
re-configuration much faster. We should use cached values sparingly and only
where they provide benefit.
> 
> Additionally, every cached CMake variable is a configuration point.
Variables not marked `INTERNAL` show up in `ccmake` and `cmake-gui`, and
variables not `mark_as_advanced` show up to all users. We should use the
`INTERNAL` and `mark_as_advanced` options wherever appropriate to limit our
supported configuration interface.
> 
> #### Making Sense of Runtime Builds
> Right now, there are three different ways to build compiler-rt as part of
LLVM and two different ways to build most of the other runtime libraries
(libcxxabi, libcxx, libunwind, etc). This situation is confusing even for long
time contributors.
> 
> We need a clearer story for building runtime libraries to reduce the number
of different ways they are built and provide simplified workflows for users.
> 
> It is my opinion that if you are building a runtime library as part of an
LLVM/Clang build, it should be configured and built with the in-tree clang as it
would be for distribution. If you don't want to build with the in-tree
clang, we should encourage people to build the runtime libraries independently
of the compiler.
> 
> My reasoning for this is that distributions of clang are generally built
from the default settings in the build and configuration process, and
distributions (or installs by new users) which include the runtime libraries
should have runtimes built with the just-built compiler. To align these two
situations we need the default build configuration of LLVM+Clang+Runtimes to be
using the just-built compiler.
> 
> Adopting this change would mean runtime library projects would only contain
build system support for building "standalone" meaning not in the same
configuration as LLVM. We would then support runtime libraries built as
individual projects or using the LLVM runtimes directory, which separately
configures and builds runtime libraries using the just-built clang.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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