Enable Texture Upscaling on macOS (#645)

* Compile a universal libomp
* static linking OpenMP

.github/workflows/c-cpp.yml

@@ -67,6 +67,10 @@ jobs:
           fetch-depth: 0
           submodules: true
 
+      - name: Compile a universal OpenMP
+        run: brew reinstall --build-from-source --formula ./shell/apple/libomp.rb
+        if: runner.os == 'macOS'
+
       - uses: actions/cache@v3
         with:
           path: ${{ env.CCACHE_DIR }}

CMakeLists.txt

@@ -211,6 +211,8 @@ if(USE_OPENMP)
             # Reference: https://android.googlesource.com/platform/ndk/+/refs/heads/master/tests/device/openmp/CMakeLists.txt
             set_target_properties(${PROJECT_NAME} PROPERTIES COMPILE_OPTIONS -fopenmp)
             target_link_libraries(${PROJECT_NAME} PRIVATE -fopenmp -static-openmp)
+        elseif(APPLE)
+            target_link_libraries(${PROJECT_NAME} PRIVATE OpenMP::OpenMP_CXX -static-openmp)
         else()
             target_link_libraries(${PROJECT_NAME} PRIVATE OpenMP::OpenMP_CXX)
         endif()

shell/apple/libomp.rb

@@ -0,0 +1,74 @@
+class Libomp < Formula
+  desc "LLVM's OpenMP runtime library"
+  homepage "https://openmp.llvm.org/"
+  url "https://github.com/llvm/llvm-project/releases/download/llvmorg-14.0.0/openmp-14.0.0.src.tar.xz"
+  sha256 "28a1cbdd3dfdd331e4ed2dda2b4477fc418e455c883bd0d1d6acc331118e4688"
+  license "MIT"
+
+  livecheck do
+    url "https://llvm.org/"
+    regex(/LLVM (\d+\.\d+\.\d+)/i)
+  end
+
+  bottle do
+    sha256 cellar: :any,                 arm64_monterey: "cf1058b26e1a778e523d51562c99b4145aea1b1cb89f1c60b3315677a86c7a08"
+    sha256 cellar: :any,                 arm64_big_sur:  "bbf77a1a151f00a18e340ab1f655fb87fe787a85834518f1dc44bf0c52ae7d4c"
+    sha256 cellar: :any,                 monterey:       "e66d2009d6d205c19499dcb453dfac4376ab6bdba805987be00ddbbab65a0818"
+    sha256 cellar: :any,                 big_sur:        "ed9dc636a5fc8c2a0cfb1643f7932d742ae4805c3f193a9e56cab7d7cf7342e7"
+    sha256 cellar: :any,                 catalina:       "c72ce9beecde09052e7eac3550b0286ed9bfb2d14f1dd5954705ab5fb25f231b"
+    sha256 cellar: :any_skip_relocation, x86_64_linux:   "9fe14d5f4c8b472de1fad74278da6ba38da7322775b8a88ac61de0c373c4ad10"
+  end
+
+  depends_on "cmake" => :build
+  depends_on :xcode => :build # Sometimes CLT cannot build arm64
+  uses_from_macos "llvm" => :build
+
+  on_linux do
+    keg_only "provided by LLVM, which is not keg-only on Linux"
+  end
+
+  def install
+    # Disable LIBOMP_INSTALL_ALIASES, otherwise the library is installed as
+    # libgomp alias which can conflict with GCC's libgomp.
+    
+    args = ["-DLIBOMP_INSTALL_ALIASES=OFF"]
+    args << "-DOPENMP_ENABLE_LIBOMPTARGET=OFF" if OS.linux?
+
+    # Build universal binary
+    ENV.permit_arch_flags
+    ENV.runtime_cpu_detection
+    args << "-DCMAKE_OSX_ARCHITECTURES=arm64;x86_64"
+
+    # system "cmake", "-S", "openmp-#{version}.src", "-B", "build/shared", *std_cmake_args, *args
+    # system "cmake", "--build", "build/shared"
+    # system "cmake", "--install", "build/shared"
+
+    system "cmake", "-S", "openmp-#{version}.src", "-B", "build/static",
+                    "-DLIBOMP_ENABLE_SHARED=OFF",
+                    *std_cmake_args, *args
+    system "cmake", "--build", "build/static"
+    system "cmake", "--install", "build/static"
+  end
+
+  test do
+    (testpath/"test.cpp").write <<~EOS
+      #include <omp.h>
+      #include <array>
+      int main (int argc, char** argv) {
+        std::array<size_t,2> arr = {0,0};
+        #pragma omp parallel num_threads(2)
+        {
+            size_t tid = omp_get_thread_num();
+            arr.at(tid) = tid + 1;
+        }
+        if(arr.at(0) == 1 && arr.at(1) == 2)
+            return 0;
+        else
+            return 1;
+      }
+    EOS
+    system ENV.cxx, "-Werror", "-Xpreprocessor", "-fopenmp", "test.cpp", "-std=c++11",
+                    "-L#{lib}", "-lomp", "-o", "test"
+    system "./test"
+  end
+end