Improve CMake/FetchContent support

[ahoarau]

Hi,
First of all, thanks for this great library ! I started integration in various CMake projects, and wondered if we could improve the integration.

Issues

First, I noticed that the layout of the amalgamated archive is as follows:

<archive>/arm/neon.h

While the brew/apt versions are under the "simde" folder:

/usr/include/simde/arm/neon.h
/opt/homebrew/Cellar/simde/0.8.2/include/simde/arm/neon.h

To use it in CMakeusing FetchContent, we have to use a little trick to match the packaged version:

  include(FetchContent)
  FetchContent_Declare(
    simde
    URL https://github.com/simd-everywhere/simde/releases/download/v0.8.2/simde-amalgamated-0.8.2.tar.xz
    URL_HASH MD5=57239a45e0cc7ceccb20b3b69cae6db5
    # NOTE: we change the base dir with SOURCE_DIR to match the simde installed with apt-get (simde prefix)
    SOURCE_DIR ${FETCHCONTENT_BASE_DIR}/simde-src/simde
  )
  FetchContent_MakeAvailable(simde)

  add_library(simde::simde INTERFACE IMPORTED)
  target_include_directories(simde::simde SYSTEM INTERFACE ${FETCHCONTENT_BASE_DIR}/simde-src)

Proposed solutions

1. Add a "simde" sub-folder in the amalgatated archive

This would simplify the FetchContent usage to a more standard:

  include(FetchContent)
  FetchContent_Declare(
    simde
    URL https://github.com/simd-everywhere/simde/releases/download/v0.8.2/simde-amalgamated-0.8.2.tar.xz
    URL_HASH MD5=57239a45e0cc7ceccb20b3b69cae6db5
  )
  FetchContent_MakeAvailable(simde)

  add_library(simde::simde INTERFACE IMPORTED)
  target_include_directories(simde::simde SYSTEM INTERFACE ${simde_SOURCE_DIR})

2. Provide a CMake support for the repo

Use cases concerned:

• Using simde as a submodule
• Using simde as a subfolder
• Using simde with FetchContent/CPM

  include(FetchContent)
  FetchContent_Declare(
    simde
    GIT_REPOSITORY https://github.com/simd-everywhere/simde
  )
  FetchContent_MakeAvailable(simde)
  # Use the imported simde::simde target

3. Provide a Cmake Support for the amalgamated version

Adding a CMakeLists.txt in the amalgamated archive like this one would enable native FetchContent:

cmake_minimum_required(VERSION 3.10)
project(simde VERSION 0.8.7)
add_library(simde::simde INTERFACE IMPORTED)
target_include_directories(simde::simde SYSTEM INTERFACE ${CMAKE_CURRENT_SOURCE_DIR})

[mr-c]

Hello @ahoarau and thank you for the positive use report! Can you list your projects at https://github.com/simd-everywhere/simde/wiki/Projects-Using-SIMDe ?

I would accept PRs to accomplish all of your listed suggestions; though this project will continue to use meson for building and running the tests.

The amalgamated release files are built using https://github.com/simd-everywhere/simde/blob/master/amalgamate.py ; though the compressed archive is made manually. If you want to add a script to automate running the amalgamate.py script + making the compressed archive with the suggested layout.

[ahoarau]

Hello @ahoarau and thank you for the positive use report! Can you list your projects at https://github.com/simd-everywhere/simde/wiki/Projects-Using-SIMDe ?

Done 👍

I would accept PRs to accomplish all of your listed suggestions; though this project will continue to use meson for building and running the tests.

I would also add a github ci to test the CMake integration. OK for you ?

[mr-c]

Hello @ahoarau and thank you for the positive use report! Can you list your projects at https://github.com/simd-everywhere/simde/wiki/Projects-Using-SIMDe ?

Done 👍

Thank you! Cool project 👍🏻

I would accept PRs to accomplish all of your listed suggestions; though this project will continue to use meson for building and running the tests.

I would also add a github ci to test the CMake integration. OK for you ?

Sure, hopefully a quick test, our matrix is quite lengthy 😅

[ahoarau]

@mr-c The main CMakeLists is functional. There's more work for porting the tests.
If you use Meson for the tests, maybe it's best to remove all the old CMake stuff (and not port the tests in CMake) ?

[mr-c]

@mr-c The main CMakeLists is functional. There's more work for porting the tests. If you use Meson for the tests, maybe it's best to remove all the old CMake stuff (and not port the tests in CMake) ?

Sure, it has been long enough that I think we can remove the test-related CMake bits. We can support CMake only for discovery and installation of the headers, but not for building & running the tests)

[ahoarau]

@mr-c I have a python script to make the new archive (containing the simde/ folder), but I need to list the expected files for it to work. Could you show me how you use your amalgamate script ?

[mr-c]

    for header in simde/*/*.h; do
        header="$(echo "$header" | cut -b7-)"
        mkdir -p simde-amalgamated-${VERSION}/$(dirname "$header");
        ./amalgamate.py "simde/$header" > amalgamated/"${header}";
      done
    tar czf simde-amalgamated-${VERSION}.tar.xz simde-amalgamated-${VERSION}